New Drones in Arctic Environments: Development of Automatic …1257208/FULLTEXT01.pdf · 2018. 10. 19. · Drones in Arctic Environments: Development of Automatic Water Sampler for

IN DEGREE PROJECT MECHANICAL ENGINEERING,SECOND CYCLE, 30 CREDITS

, STOCKHOLM SWEDEN 2018

Drones in Arctic Environments: Development of Automatic Water Sampler for Aerial Drones

SOFIA OLSSON

KTH ROYAL INSTITUTE OF TECHNOLOGYSCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT

Drones in Arctic Environments: Development ofAutomatic Water Sampler for Aerial Drones

Thesis WIP

SOFIA OLSSON

Master’s Thesis at ITMSupervisor: Carl During

Examiner: Martin Grimheden

TRITA-ITM-EX 2018:706

AbstractThe purpose of the thesis is to develop a water samplingsolution to use with an aerial drone for remote water sam-pling and to investigate the feasibility of the system. Theactuating hypothesis is that using a drone for this applica-tion will have many benefits over the manual methods, forexample to reach inhospitable areas, improve data gath-ering and offer a safer work situation for the researchers.The research method has been empirical and exploring, byrapidly develop prototypes based on a pre-study, test thefull test system and draw conclusions regarding the feasi-bility of the application based on the tests. Through thepre-study of the current water sampling process throughinterviews and a survey, a general user case was created. Itwas studied with a mechatronic perspective to understandhow the current water sampling process could be adjustedto function remotely with a drone. The main focuses whendeveloping the water sampler was to design a product inde-pendent from the drone with full automatic function, andto maximize its water volume capacity while minimizing theweight of the sampler to manage the drones barload con-straints of 1 kg. Through workshop activities and methodsfrom TRIZ theory, several concepts were evaluated. Themain idea was to integrate the laboratory bottle with thewater sampler. Two physical prototypes were designed totest the function of the concepts and evaluate them againstthe Ruttner sampler. The first prototype, the Wheel, has asimple design, is lightweight and mechanic while the secondprototype, the Combination, is more complex, heavier anduses a mechatronic system. The prototypes were evaluatedthrough functional tests to investigate its design and suit-ability to be used with a drone for water sampling. The be-havior of the full test system, consisting of the Wheel sam-pler and a drone, was observed and analyzed through dronedata when gathering water samples. The thesis demon-strates through field tests that the system, consisting ofdrone and developed water sampler, succeeds in gatheringwater samples remotely. Through tests of the water sam-plers, the thesis also shows the benefits and disadvantagesof their proposed design for water sampling.

ReferatDrones in Arcitc Environments: Utveckling

av automatisk vattenprovtagare förluftdrönare

Examensarbetets syfte ar att utveckla en losning for vatten-provtagning som kan anvandas med en luftdronare for attta vattenprover och att undersoka systemets lamplighet.Den drivande tesen ar att anvandningen av dronare fordenna applikation har manga fordelar framfor de manu-ella metoderna, till exempel att na ogastvanliga omraden,forbattrad datainsamling och en sakrare arbetsplats for fors-karna. Forksningsmetoden har varit empirisk och utfors-kande, genom att snabbt utveckla prototyper, baserat pa enforstudie, testa hela testsystemet och dra slutsatser angaendelampligheten av applikationen basera pa testerna. Genomforstudien, som undersokte den nuvarande vattenprovtag-ningsprocessen genom intervjuer och en undersokning, ska-pades ett generellt anvandarfall. Det studerades med ettmekatroniskt perspektiv for att forsta hur dagens processkan anpassas for att fungera remote med en dronare. Fo-kuset under utvecklingen var att designa en fullt autom-tisk provtagare fristaende fran dronaren, samt att maxime-ra dess volymkapacitet medan dess vikt minimerades foratt klara dronarens lastkrav pa 1 kg. Genom workshopsoch metoder fran TRIZ-teorin utvarderades flera koncept.Huvudiden var att integrera laborationsflaskan med prov-tagaren. Tva fysiska prototyper byggdes for att testa derasfunktion och utvardera dem mot Ruttnerhamtaren. Forstaprototypen, the Wheel, har en simpel design, har lag viktoch ar mekanisk, medan den andra prototypen, the Com-bination, ar mer komplex, tyngre och har ett mekatronisktsystem. Prototyperna utvarderas genom funktionstester foratt undersoka dess design och lamplighet att anvandas meddronare for vattenprovtagning. Beteendet hos hela testsy-stemet, som bestod av the Wheel och dronare, observeradesoch analyserades nar vattenprov samlades. Examensarbetetdemonstrerar genom faltprov att systemet, som bestar avprovtagare och dronare, lyckas samla in vattenprover re-mote. Genom tester av vattenprovtagarna visar examens-arbetet ocksa fordelar och nackdelar med deras foreslagnadesign for vattenprovtagning.

Acknowledgements

This study would not have been possible without the support, knowledge and feed-back from a big variety of people.To begin with, I would like to thank my academic supervisor from KTH, Carl Dur-ing for his constant support and encouragements throughout the thesis work. FromKTH, I would also like to thank Damir Nesic for helping me define the thesis in itsinitial state.Furthermore, I would like to thank my technical supervisor at AF, Tomas Gustafs-son, for guiding me in the right directions. Other important people at AF thatI would like to thank are Johan Rossner and Johan Eed for participating in theWorkshop activities which generated a lot of well elaborated ideas, Eskil Bendz andTor Ericson for guidance, knowledge and inspiration. All of you made me feel verywelcome at AF.Additionally, I would like to thank all environmental researchers within InterActthat participated in the interviews and the survey. Your experience and knowledgeare the foundation of the thesis and it would not have been possible without yourhelp.Finally, I have to thank my close friends and family for all support and encourage-ment. I would like to give a special thank you to my partner Tim Lindqvist for hisdaily inspiration, valuable ideas and technical knowledge, and to my parents EvaOlson and Urban Olsson for helping me with project planning, technical issues andbelieving in me from the beginning to the end.

Contents

1 Introduction 11.1 Drones in Arctic Environments . . . . . . . . . . . . . . . . . . . . . 11.2 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4 Research questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.5 Research methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 21.6 Ethical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 State of the Art 52.1 Water samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 Water sampling drones . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3 Pre-study 153.1 Interviews and survey . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.1.1 Interview evaluation . . . . . . . . . . . . . . . . . . . . . . . 153.1.2 Survey evaluation . . . . . . . . . . . . . . . . . . . . . . . . 17

3.2 Requirement specification . . . . . . . . . . . . . . . . . . . . . . . . 233.3 Problem formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.1 Optimized water sampling procedure . . . . . . . . . . . . . . 24

4 Concept generation 274.1 TRIZ - Theory of Inventive Problem Solving . . . . . . . . . . . . . 27

4.1.1 Results from TRIZ . . . . . . . . . . . . . . . . . . . . . . . . 284.2 Workshop activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304.3 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.1 Plastic Bag . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.3.2 Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.3.3 Cake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334.3.4 Combination . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.4 Evaluation and choice of concept . . . . . . . . . . . . . . . . . . . . 354.4.1 Suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364.4.2 Concept evaluation . . . . . . . . . . . . . . . . . . . . . . . . 36

5 Construction of Prototypes 39

5.1 Material choices and manufacturing method . . . . . . . . . . . . . . 395.2 Base design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395.3 Wheel unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415.4 Cake unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.4.1 Design options for Cake unit . . . . . . . . . . . . . . . . . . 435.4.2 Electric components of mechatronic system . . . . . . . . . . 455.4.3 Construction of Cake unit . . . . . . . . . . . . . . . . . . . . 475.4.4 Combination concept . . . . . . . . . . . . . . . . . . . . . . . 50

6 Testing and results 536.1 Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

6.1.1 Weight of prototypes, Req. 1, 2, 3 . . . . . . . . . . . . . . . 536.1.2 Take samples at depth of 10 meters, Req 5 . . . . . . . . . . 556.1.3 Water sample reliability . . . . . . . . . . . . . . . . . . . . . 576.1.4 Depth and temperature of pressure sensor . . . . . . . . . . . 586.1.5 Full test system . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7 Discussion and Future work 697.1 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.1.1 Regarding the pre-study . . . . . . . . . . . . . . . . . . . . . 697.1.2 Regarding the design and prototypes . . . . . . . . . . . . . . 707.1.3 Regarding the full test system . . . . . . . . . . . . . . . . . . 737.1.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

7.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Bibliography 79

Appendices 80

A Interviews with researchers 81

B Survey report 91

C Requirement specification 103

D Criterion for concept evaluation 105

E Code 109

List of Figures

2.1 Ruttner sampler, open to the left and closed to the right. . . . . . . . . 62.2 Limnos sampler, open to the left and closed to the right. . . . . . . . . . 62.3 Glass bottle version of Limnos sampler. . . . . . . . . . . . . . . . . . . 72.4 Niskin sampler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5 Function of Nansen sampler, where the weight triggers the closing mech-

anism to the left, the Nansen starts to reverse and drops the next weightin the middle and is closed to the right. . . . . . . . . . . . . . . . . . . 8

2.6 Van Dorn sampler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.7 Autonomous drone with the three water sample containers attached on

the bottom of the drone. . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.8 Lusi drone water sampler and winch. . . . . . . . . . . . . . . . . . . . . 112.9 Several syringe samplers combined in an AUV Gulper. . . . . . . . . . . 112.10 Robotic catamaran with water sampling carousel. . . . . . . . . . . . . . 122.11 Remote helicopter with water sample container attached on the bottom

of the helicopter and the pump hanging freely. . . . . . . . . . . . . . . 12

3.1 Transfer of water sample to laboratory bottle. . . . . . . . . . . . . . . . 163.2 Result from survey about the respondents. . . . . . . . . . . . . . . . . . 183.3 Result from survey regarding water sample volume. . . . . . . . . . . . . 183.4 Survey result regarding current material and wanted material in sam-

pling equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.5 Survey result regarding how often the respondents gather water samples,

how many people are needed and how many hours are spent on eachwater sampling session. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.6 Survey result regarding sampling interval and maximum depth. . . . . . 203.7 Survey result regarding data gathering. . . . . . . . . . . . . . . . . . . 213.8 Survey result regarding actions to avoid contamination. . . . . . . . . . 223.9 Visualization of the water sampling procedure were a) is the current

procedure using a boat and b) is an optimized procedure using a drone. 25

4.1 The contradiction matrix with chosen features to improve and preserve,and the suggested solving principles marked by the yellow crossroad. . . 28

4.2 Sketch of double threaded container to make laboratory bottle similarto todays water samplers. . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3 Sketch of closing mechanism of a) van Dorn, b) Ruttner and c) Limnossampler, where a) and b) are inside the container, and c) is outside thecontainer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.4 Basic sketch of a mechanism that screws on/holds the lids onto the lab-oratory bottle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.5 Basic sketch of from each other independent closing mechanisms thatallows water to flow in only one direction. . . . . . . . . . . . . . . . . . 31

4.6 Basic sketch of Plastic Bag concept where a) is the disposable plasticversion and b) is the expandable version for multiple use in empty andfilled state respectively. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.7 Wheel concept where a) is the cross-section of the valve, b) is the functionwhen the bottle is sinking and c) is the function when the bottle is pulledup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.8 Cake concept where a) is the open valve when the bottle is sinking andb) is the closed valve when the outer discs have rotated. Above thebottles, the cross-section of the discs are shown. . . . . . . . . . . . . . . 34

4.9 Combination of concepts where the Wheel is on the top and the Cake ison the bottom, short name WT-CB (Wheel Top - Cake Bottom). Theleft is when the bottle is sinking and the right when the bottle is pulledup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.10 Combination of concepts where the Cake is on the top and the Wheel ison the bottom, short name CT-WB (Cake Top - Wheel Bottom). Theleft is when the bottle is sinking and the right when the bottle is pulledup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.11 The four concepts to further develop, where a) uses two Wheel units, b)uses two Cake units and c) and d) uses one Cake unit and one Wheel unit. 37

5.1 Hollow laboratory bottle, without lids to the left and with lids to theright. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.2 Threaded base on which a valve unit will be attached. The margin ismarked in the left figure. The three brackets for suspension are seen inthe right figure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.3 CAD illustration of Wheel unit, where a) is the upper unit and b) is thelower unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.4 Exploded view of the two Wheel units, where a) is the top unit and b)is the bottom view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.5 CAD illustration of entire Wheel concept, with both upper and lowerWheel units and laboratory bottle. Silicon was glued to the red areas inthe figure to avoid leakage. . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.6 Visualization of the servo idea, view from the side. The blue arrowsindicates where water can potentially leak into the enclosure. . . . . . . 43

5.7 Visualization of the magnet and servo idea, view from the side. . . . . . 445.8 Visualization of the magnet idea, view from the side. . . . . . . . . . . . 445.9 CAD illustration of the content of the Cake unit. . . . . . . . . . . . . . 47

5.10 Pressure sensor in its enclosure. . . . . . . . . . . . . . . . . . . . . . . . 475.11 CAD illustration and photo of the bottom of the Cake unit, where the

content in the enclosures can be accessed. . . . . . . . . . . . . . . . . . 485.12 CAD illustrations and photo of the Cake unit. . . . . . . . . . . . . . . 485.13 Schematic of the electric wiring of the Cake unit. . . . . . . . . . . . . . 495.14 General software logic of the system. . . . . . . . . . . . . . . . . . . . . 505.15 Combination concept where a) is Cake unit on top and Wheel unit as

bottom and b) is the Wheel unit on top and Cake unit as bottom. . . . 51

6.1 Illustration of how the Combination concept with Wheel unit on top andCake unit as bottom failed due to the floating Cake unit. . . . . . . . . 56

6.2 Illustration of how the other Combination concept (CT-WB) sinks. . . . 576.3 Combination concept with Cake unit at top and wheel unit at bottom.

The image to the right is the reference, the middle image is at a depthof 5 m and the image to the left is at 10 m. . . . . . . . . . . . . . . . . 58

6.4 Wheel concept. The image to the right is the reference, the middle imageis at a depth of 5 m and the image to the left is at 10 m. . . . . . . . . 58

6.5 Test of depth and temperature measurement of pressure sensor. . . . . . 596.6 Roll, pitch and yaw angles of drone. . . . . . . . . . . . . . . . . . . . . 616.7 The current of the Quadrotor during no external payload. The blue line

is the altitude [m], and the red line is the current [A]. . . . . . . . . . . 626.8 The current of the Quadrotor when gathering a water sample with the

Wheel sampler at 425 seconds, see dotted line. The blue line is thealtitude [m], and the red line is the current [A]. . . . . . . . . . . . . . . 62

6.9 The desired yaw and the actual yaw of the Quadrotor during watersampling. The red line is the desired yaw and the blue line is the actualyaw. No remarkable deviation is noted in the time interval between 310and 425 s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.10 The desired pitch and the actual pitch of the Quadrotor during watersampling. The red line is the desired pitch and the blue line is the actualpitch. The deviation is notable between 310 s and 425 s. . . . . . . . . . 63

6.11 The desired roll and the actual roll of the Quadrotor during water sam-pling. The red line is the desired roll and the blue line is the actual roll.The deviation is notable between 310 s and 425 s. . . . . . . . . . . . . 64

6.12 The current of the Octorotor during no external load. The blue line isthe altitude [m], and the red line is the current [A]. . . . . . . . . . . . . 64

6.13 The current of the Octorotor when gathering a water sample at approx-imately 150 s with the Wheel sampler, see dotted line. The blue line isthe altitude [m], and the red line is the current [A]. . . . . . . . . . . . . 65

6.14 The desired yaw and the actual yaw of the Octorotor during water sam-pling. The red line is the desired yaw and the blue line is the actual yaw.No remarkable deviation is noted. . . . . . . . . . . . . . . . . . . . . . 65

6.15 The desired pitch and the actual pitch of the Octorotor during watersampling. The red line is the desired pitch and the blue line is the actualpitch. No remarkable deviation is noted. . . . . . . . . . . . . . . . . . . 66

6.16 The desired roll and the actual roll of the Octorotor during water sam-pling. The red line is the desired roll and the blue line is the actual roll.No remarkable deviation is noted. . . . . . . . . . . . . . . . . . . . . . 66

7.1 The triangular force distribution when the two discs are pressed againsteach other at the servo axis position only. . . . . . . . . . . . . . . . . . 76

7.2 Placement of o-ring for a better sealed unit. The o-rings should be placedbetween the two disks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

B.1 Graphs showing profession, years experience and current task. . . . . . . 91B.2 Graphs showing water volume and frequency of water samples. . . . . . 92B.3 Graph and tables showing sampler models and their pros and cons. . . . 92B.4 Graphs showing time and how many people sampling takes. . . . . . . . 93B.5 Graphs showing max. depth and depth interval of sampling. . . . . . . . 93B.6 Graph showing measured data. . . . . . . . . . . . . . . . . . . . . . . . 94B.7 Graphs showing desired data and accuracy of temp. . . . . . . . . . . . 95B.8 Graph showing importance of characteristics of sampler. . . . . . . . . . 96B.9 Graph showing importance of characteristics with average value. . . . . 97B.10 Graph showing actions to avoid contamination. . . . . . . . . . . . . . . 98B.11 Graph showing reasonable pricing of sampler. . . . . . . . . . . . . . . . 99B.12 Tables showing challenges and risks of sampling. . . . . . . . . . . . . . 100B.13 Graphs showing current material and desired material of sampler. . . . 101B.14 Graph showing reactions on proposed idea with integrated laboratory

bottle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

List of Tables

2.1 Advantages and disadvantages of water samplers . . . . . . . . . . . . . 92.2 Approaches of the presented water sampling drones . . . . . . . . . . . . 13

3.1 Advantages and disadvantages of water sampling models according tothe survey respondents. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2 Characteristics of sampler rated according to importance . . . . . . . . 223.3 Identified challenges and risks with water sampling according to the re-

spondents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1 Pugh evaluation matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

6.1 Tests and reference to its originating requirement. . . . . . . . . . . . . 536.2 Weighed parts of the prototypes according to test 1. . . . . . . . . . . . 546.3 Water sample volume per gram. . . . . . . . . . . . . . . . . . . . . . . 556.4 Sinking speed of water sampler. . . . . . . . . . . . . . . . . . . . . . . . 556.5 Actual and outputted depth of sensor. . . . . . . . . . . . . . . . . . . . 606.6 Actual and outputted temperature of sensor. . . . . . . . . . . . . . . . 606.7 Specifications of the two drones used for tests. . . . . . . . . . . . . . . 606.8 Summary of test results. . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

7.1 Summary RQ 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697.2 Summary RQ 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 717.3 Summary RQ 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

D.1 Criterion for concept evaluation . . . . . . . . . . . . . . . . . . . . . . . 105

Chapter 1

Introduction

This chapter contains background information, the purpose of the study and thescope of the thesis, in order to explain the motivations behind it. It further includesthe research questions and research methodology, to define the research focus of thethesis. The chapter is ended with the ethical considerations taken into accountthroughout the thesis.

1.1 Drones in Arctic Environments

InterAct is an EU funded project for international polar research that investigatesclimate change and its effect on the Arctic environment [1]. Researchers from anetwork of over 80 different polar stations investigate, identify and predict the cli-mate changes on the Arctic regions [2]. Data is collected through two primarymethods: satellite information and field work. To investigate how drones can makethe researchers’ work process more efficient, improve the data gathering and accessinhospitable polar regions, AF AB has initiated the project “Drones in Arctic Envi-ronments”. An earlier master’s thesis identified the field work associated with watersampling as an area that could be improved [3]. Water samples are gathered fromlakes that contains melt water from surrounding glaciers to investigate the waterenvironment and the glacier content.

1.2 Purpose

The purpose of the thesis is to study the current water sampling process of the re-searchers within the network InterAct with a mechatronic perspective to investigatehow to improve the process. This will be done by developing an automatic watersampling equipment based on their needs, to be used with a drone for remote watersampling.

1

CHAPTER 1. INTRODUCTION

1.3 ScopeThis report describes the work conducted during a 20 week period at AF AB inSweden. A water sampling prototype to use with drones will be developed. Formanufacturing, machines available at Royal Institute of Technology will be used.The drones used to test the sampling equipment are capable of carrying a load ofmaximum 1 kg. When designing the water sampling equipment, only aerial vehiclesare considered as carriers. The drones need to keep a safety distance to the watersurface of at least 2 meters. The drone will exclusively be seen as a carrier of thesampling equipment and will not be modified.

1.4 Research questionsThe research consists of a main research question RQ, which will be investigatedthrough three underlying research questions, focusing on the main RQ from differentperspectives.

RQ Can a water sampler be designed to a given drone to automate the watersampling process?

a) What challenges and needs do the researchers have regarding the water sam-pling procedure they use today?

b) How can a water sampler be designed to a given drone to automate the watersampling process?

c) How is the full test system1 affected by water sampling?

1.5 Research methodologyThe main research question RQ will be investigated through the three underlyingquestions a), b) and c) and explicitly answered in Chapter 6. Since the specific ap-plication, water sampling using drones, is relatively unexplored the overall method-ology in the thesis is empirical and exploring.The first underlying question a) will be answered using a qualitative research method.Researchers will be interviewed using semi-structured interviews. The interviewquestions will encourage open answers within the area of water sampling. The re-searchers will also answer a survey with the purpose of examining the severity ofchallenges, needs and issues using the current methods and equipment and the in-terest for different solutions, and structure the data quantitatively. The results fromthe interviews and survey will be used, in combination with relevant literature, todraw conclusions on how to improve the water sampling procedure and formulatethe needed requirements.

1The full test system refers to the combined system of a drone and water sampler.

2

1.6. ETHICAL CONSIDERATIONS

The second question b) will be answered using a confirming quantitative researchmethodology where certain properties of the functionality of the developed solutionand the water sampler used today are compared. The result will state what bene-fits and constraints the developed solution has compared to the water sampler usedtoday in terms of functionality. The importance of the properties will be mappedin the survey conducted when answering research question a), which will affect thefocus of the functionality of a developed solution. The properties are:

• Weight

• Water sample volume

• Level of automation

• Ability to take samples on different depths

• Time to take the needed samples as desired depths

• Reliability of water sample

The third underlying question c) will be answered through observation and analysisof the behavior of the full test system. The focus of the observation and analysiswill be both on the overall system and on more focused areas of the system. Theinfluence by the water sampler on the drones will be analyzed through data fromthe drones during the water sampling tests. How the application water samplingaffects the flight time of the drone, through current consumption, stability of thedrone and the behavior of the water sampler in water, is analyzed.

1.6 Ethical considerationsWhen performing research it is important to credit the authors of the sources usedthroughout the study. Being transparent with what work is done by who is im-portant, since taking credit for work performed by somebody else is consideredunethical. It is also important to offer the reader the sources and references usedin the study if they want more information within that field. Another reason to betransparent with the used sources is to increase the credibility and reliability of theresearch by showing what the conclusions and results in the study are based on.Specific ethical considerations in this study are aspects regarding environmental im-pact. The end-users are polar researchers who work with investigating, identifyingand predicting the climate changes in the Arctic regions. Their current methodof water sampling is using a boat and a mechanical water sampler. This manualmethod can be seen as more environmentally friendly than using a more advancedtechnical water sampling drone with possibly integrated electric components. Inthe future, the product can be extended to several versions and modules, whichin the long run could favor mass production of sampling devices. When develop-ing new products it is always important to avoid products for short term use and

3

CHAPTER 1. INTRODUCTION

aim towards an environmentally friendly life cycle of the product, but even morein this project considering the end-users being environmental researchers. On theother hand, the purpose of the water sampling drone is to improve the current watersampling procedure which means it could improve the understanding of the environ-mental situation in the long run. Also, using only a water sampler will have a lowerimpact on the lake water in terms of contamination compared to using both boatand water sampler. Another perspective is that of the inhabitants of the glaciers.Drones are usually loud which will disturb the animals living there. Some animalscan confuse drones for eagles or other threatening creatures [3]. As humans areintruding the environment of the animals and the surrounding nature, respect andunderstanding of the environment is necessary.Another aspect is the automation of work duties. In the future, the prototypecould be further developed and used for a fully autonomous, remote water sam-pling, meaning the researchers could control the drone from a far distance. Thiswould only be possible if the law regarding flying drones within the line of sightwould be modified. This kind of autonomous sampling would decrease the amountof work for the researchers and help them reach water in inhospitable areas, whichwould increase the knowledge of the water environment in those areas. On the otherhand, many environmental researchers enjoy being out in nature doing field work,and might experience negative feelings regarding this automated development.

4

Chapter 2

State of the Art

This chapter contains a state of the art of water samplers and water sampling drones.A literature review was conducted to investigate the available water samplers onthe market as well as the current usage of water sampling drones.

2.1 Water samplersThere is a big variety of water samplers on the market, both models designed for aspecific purpose and models designed for water sampling in general. Many modelshave similar design or functions but with varying details. The presented samplersbelow are a selection of the most popular models for general water sampling. Theadvantages and disadvantages of the models are summarized in the end of thesection.

Ruttner sampler

The Ruttner sampler is available in many different sizes and is often used whensamples from different depths are needed [4]. It is a acrylic cylinder open in bothends, with the two lids held apart from the openings by a rod placed through thecylinder, see figure 2.1. When put in water, the open cylinder sinks vertically asthe water is flushing through it. The Ruttner sampler is attached to a wire with amark at the desired depth and a weight that can slide along the wire. When thedesired depth is reached the user drops the weight, and when the weight hits the lidof the cylinder a closing mechanism is triggered. The water sample is then capturedinside the cylinder. A hose at the bottom of the sampler is used to transfer thewater sample to a laboratory bottle.

5

CHAPTER 2. STATE OF THE ART

Figure 2.1. Ruttner sampler, open to the left and closed to the right.

Limnos sampler

There are two different models called Limnos sampler. One is similar to a Ruttnersampler but with a better and more robust closing mechanism with the drawbackof increased weight and bulkiness, see figure 2.2. The step when the user drops a

Figure 2.2. Limnos sampler, open to the left and closed to the right.

weight that slides along the wire to close the sampler is the same as for the Ruttner.The other model is designed to avoid contamination. It consists of two or more glassbottles, fastened in a holder device [5] [6], see figure 2.3. When lowered into thewater, the glass bottles are closed to avoid contamination from other water layers.Two hoses placed inside the glass bottles and through the lid are kept fixed in abent position to prevent water from entering the bottle. When at the right depth,the user drops a weight that triggers the hoses to spring open, letting water in andair out simultaneously. To avoid transferring the water sample to another vessel,the glass bottles are unscrewed from the holder device and a sterilized lid is screwed

6

2.1. WATER SAMPLERS

Figure 2.3. Glass bottle version of Limnos sampler.

on.

Niskin sampler

The Niskin sampler is a robust sampler, often used when big volumes of watersamples are needed. Usually the sampler is used for water sampling in oceans fromships [7]. The sampler is made of plastic and is a vertical, hollow cylinder with astopper on each end, see figure 2.4. The stoppers are both attached to an elastic

Figure 2.4. Niskin sampler.

cord going through the center of the cylinder pulling them towards each other.They are also attached to an elastic cord outside the bottle pulling them apart.The bottle is closed when the user drops a weight that slides along the wire untilit hits the closing mechanism, which releases the outer elastic cord. The stoppersare then pulled towards each other by the inner elastic cord in the bottle and thewater sample is captured. Several Niskin bottles can be used at the same time tocollect several samples at a desired depth in a rosette sampling system or at differentdepths throughout the water column in a chain sampling system. For simultaneoussampling at different depths, several bottles are attached to the wire at a decided

7


distance. The closing mechanism from the upper bottle then triggers a weight tofall onto the lower bottle which creates a chain reaction.

Nansen sampler

The Nansen sampler was developed late 19th century and is seen as the forerunnerto the Niskin bottle [8]. The differences between the two is that the Nansen sampleris made of metal and that the closing mechanism is different, see figure 2.5. When

Figure 2.5. Function of Nansen sampler, where the weight triggers the closingmechanism to the left, the Nansen starts to reverse and drops the next weight in themiddle and is closed to the right.

the user drops the weight thats hits the bottle, the upper attachment is disengagedfrom the wire and the bottle is reversed 180◦ which closes the ends. If several bottlesare attached to the wire, the reversion also triggers another weight to slide onto thenext bottle.

Van Dorn sampler

The van Dorn sampler is a hollow cylinder with a the same closing mechanism asthe Niskin sampler. It is more robust than the Ruttner sampler [4] and can be usedboth in a vertical and horizontal position, see figure 2.6. The horizontal position is

Figure 2.6. Van Dorn sampler.

8

2.1. WATER SAMPLERS

efficient for taking samples close to the water bed [9].

Summary

Table 2.1 describes some advantages and disadvantages with the presented watersamplers.

Table 2.1. Advantages and disadvantages of water samplers

Model Advantages DisadvantagesRuttner Able to sample at different

depthsManual closing mechanism usingweight

Simple Manual depth measurementAvailable different sizes Need to transfer sample into other bot-

tleLimnos Avoids contamination Glass bottle (fragile)(Glassbottle

No need to transfer sampleinto other bottle

Manual closing mechanism usingweight

version) Able to sample at differentdepths

Manual depth measurement

SimpleNiskin Gathers big water volumes Heavy

Able to sample at differentdepths


Can be used in rosette sys-tem

Need to transfer sample into other bot-tle

Can be used in chain system Manual depth measurementNansen Can be used in chain system Made of metal


Manual closing mechanism usingweightClosing mechanism stirs waterNeed to transfer sample into other bot-tleManual depth measurement

Van Dorn Can be used both verticallyand horizontally



Need to transfer sample into other bot-tle

Simple Manual depth measurement

It is noted that all samplers have a closing mechanism that requires the user todrop a weight onto the water sampler. They also require the user to know whenthey reached the desired depth through the marked wire. All models except theglass bottle version of the Limnos sampler are designed to transfer the water sample

9


into a laboratory bottle. The conclusion is that all the presented water samplersare manual and require an active user to function properly.

2.2 Water sampling drones

The use of drones for environmental research is growing [10] but using drones forwater sampling is still relatively rare. Some reasons identified are that until re-cently, the technology has been mainly within military applications [11], payloadconstraints of drones and budget limitations of research projects. However, someinteresting water sampling drones have been developed, both using aerial- and un-derwater drones. All found water sampling drones have solutions that exceeds theweight constraint of 1 kg including water sample, which means their full solutionsare not plausible for the drone used in this thesis. Even so, they have differentinteresting solutions to gather water samples according to their specific conditions.The different approaches the drones use to gather water samples are summarized inthe end of the section.

Autonomous aerial water sampler

The autonomous aerial water sampler developed at University of Nebraska [12]is designed to collect three different samples of 20 ml automatically. The purposeof the system is to automatically gather samples from several nearby lakes. Thesystem improves the efficiency as it eliminates the need of moving a boat betweenlakes, thus saving time and cost. The water is pumped into the three containersattached to the drone, see figure 2.7. The design is 3D printed and guarantees no

Figure 2.7. Autonomous drone with the three water sample containers attached onthe bottom of the drone.

cross contamination between the sample containers. The drone can only samplesurface water because of the usage of a pump.

10

2.2. WATER SAMPLING DRONES

The Lusi Drone

The Lusi drone [13] is a multidisciplinary aerial drone used to gather sensor dataand samples from the harsh environment of the Lumpur Sidoarjo mud volcano. Itis able to gather mud and water samples using a sampler made of teflon, see figure2.8, attached to an automatic winch which is connected to the drone.

Figure 2.8. Lusi drone water sampler and winch.

The AUV Gulper

The AUV Gulper water sampler [14] is designed for underwater vehicles. Thesampler has a syringe design with several springs holding a piston, that covers theopening. When at the decided depth, the springs are compressed and the syringetake in water. Several Gulper samplers can be combined to take samples at differentdepths [15], see figure 2.9.

Figure 2.9. Several syringe samplers combined in an AUV Gulper.

Remote sampling with robotic catamaran

The robotic catamaran uses an autonomous, mechatronic bottle using a syringe-piston design [16]. The water sampler is attached to a winch on the robotic cata-maran, see figure 2.10. Up to five samples arranged in a sampling carousel can

11


Figure 2.10. Robotic catamaran with water sampling carousel.

be taken at predefined depths throughout the water column, down to a maximumdepth of 50 m. The design is for underwater vehicles.

Remote sampling with autonomous helicopter

The autonomous helicopter uses a pump to pump water samples to a containerattached on the helicopter [17], see figure 2.11. The design process evaluates

Figure 2.11. Remote helicopter with water sample container attached on the bottomof the helicopter and the pump hanging freely.

different solutions for suspending the equipment to the aerial drone.

12

2.2. WATER SAMPLING DRONES

Summary

Even though the full solutions of the presented water sampling drones exceed theweight constraint of 1 kg, the different ideas and approaches to gather water samplesare interesting to study. Four different approaches to sample water in the dronesystems are summarized in table 2.2 along with the advantages and disadvantagesof the approach.

Table 2.2. Approaches of the presented water sampling drones

Approach Advantages DisadvantagesWinch Allows drone to be far away

from waterAdds weight

Able to control height/depthof container

Complex

Pump Load not oscillating Adds weightComplexHard to get water from depthDrone needs to be close to water

Wire Low weight Entanglement riskSimple Oscillating load when flyingAllows drone to be far awayfrom water

Syringe Load not oscillating Drone needs to be close to/in wa-ter

13

Chapter 3

Pre-study

This chapter contains information about the work conducted in the pre-study phase.This includes the results from performed the interviews and survey, the resultingrequirement specification, problem formulation and use cases for the water sampler.The purpose of the chapter is to answer RQ a).

3.1 Interviews and survey

The method used to answer research question a), stated in section 1.4, was touse semi-structured interviews and to create a survey. Semi-structured interviewswas used as interview method because it results in qualitative data focused onthe specified area of water sampling, while having the flexibility of open-endedquestions [18]. The combination was useful to define the problem formulation, ascan be seen in section 3.3. A total of four interviews were performed, one in person,two over telephone and one over email. A more targeted survey was also createdto complement the interviews and to provide quantitative data. The survey wasdesigned to provide several options for each question but with the opportunity towrite a comment to each question. A total of 12 researchers participated in thesurvey and the survey consisted of 30 questions. When responding, the study groupwas asked to mainly consider water sampling in lakes and to focus on their mostfrequent case of sampling.

3.1.1 Interview evaluation

This subsection summarizes the most important findings from the interviews. Ap-pendix A includes the raw interview data. The purpose of the interviews is to get abetter understanding of the challenges of the water sampling process and the needsof the researchers within InterAct.The general purpose of water sampling is to investigate and understand the waterenvironment changes over time by measuring different biological and chemical sub-stances of the studied water environment. There are many different types of water

15

CHAPTER 3. PRE-STUDY

environment studies, both regarding type of water to be studied (streams, surfacewater, seabed water, ocean water etc), and type of substances to be measured. Thewater sampling method can differ depending on the purpose of the study, for exam-ple regarding water sample volume, frequency of the samples, amount of samples,at what depth the sample is taken, how the samples are handled or prepared foranalysis, etc.The general work method is to use a boat to reach the desired position in the wa-ter. Usually, the water samples are gathered during good weather to avoid risks anddiscomfort because of bad weather. Several water samples are taken at a chosendepth interval throughout the water column, for example every 5 meters. A sampleat a specific depth is considered representative for the homogeneous water columnfor that interval, meaning the depth accuracy is ±2.5 meters in the example above.The sampling equipment usually includes 2 containers, one is the water samplercollecting the water sample, and the other is the laboratory bottle into which thesample is transferred to, see figure 3.1. Temperature and depth are measured man-

Figure 3.1. Transfer of water sample to laboratory bottle.

ually directly when the sample is taken. Other data varies between being measureddirectly in the boat, back at the research station or being sent to an external labo-ratory, depending on the study and the substance being measured. In general, onelaboratory test needs a 20 ml of water sample. Sample volumes ranges from 200ml to several liters, but in general it is better to take a larger water sample volumeto lower the concentration of possibly occurring contamination. Other examples ofactions to avoid contamination are

• To use clean equipment.

• To collect twice the water sample volume in order to rinse the laboratorybottle with water sample before transferring water sample into it. This isdone to avoid contamination from earlier samples.

16

3.1. INTERVIEWS AND SURVEY

• To ensure that the laboratory bottle is completely filled with water sample toavoid reaction with oxygen in the air.

• Use dark material for equipment to avoid exposure to sunlight, as sunlightcan react with nutrients in the sample.

• To use equipment of appropriate material. For example, avoiding dark ma-terial in order to prevent temperature changes or avoiding metal to preventreactions with the water sample.

• To use a hollow cylindrical water sampler as the Ruttner sampler that getsrinsed automatically when sinking in the water.

• To use a sterilized closed water sampler as the Limnos sampler that is pro-tected from contamination from surface water.

Ensuring that the gathered water sample is an exact representative of the waterenvironment is hard, especially as the actions taken to avoid contamination can becontradictory. In the list above, it is noted that using dark material or a hollowwater sampler can both be positive and negative from an contamination perspective,depending on what is studied. The severity of different types of contaminationis also different depending on what is studied. Therefore, the actions to avoidcontamination differ according to the purpose of the study.

3.1.2 Survey evaluation

This subsection summarizes the most important findings from the survey and theconclusions drawn from it. The full survey report can be seen in Appendix B. Thefirst part of the survey consists of questions about the twelve respondents, see figure3.2. The figure shows that the study group is a homogeneous group of researcherswith many years experience of water sampling that have water sampling as a currenttask in their job.The next part of the survey is the main part and consists of 23 questions about the

water sampling procedure. The survey shows that 25% of the respondents need asample volume of ≤500 ml, 25% of the respondents need a sample volume of 1000 mland 50% of the researchers need a volume of ≥2000ml, see figure 3.3. The responsesthroughout the survey are marked regarding to which of these three sample volumegroups the respondent belongs to. This is to map how specifications and samplevolume needs are related, and in some cases, focus on the answers from researcherswith a need for smaller water sample volumes. The reason why water sample volumeis the separator is because the weight constraint the drone payload is 1 kg, whichmeans researchers with a smaller sample volume need are more likely to get use ofthe prototype constructed in the thesis.The survey shows that 36% of the respondents use a Ruttner sampler, 21% use aLimnos sampler, 7% use a Niskin sampler and the remaining 36% use alternative

17


Figure 3.2. Result from survey about the respondents.

Figure 3.3. Result from survey regarding water sample volume.

options. Table 3.1 show the respondents experienced advantages and disadvantagesof the different models.

18


Table 3.1. Advantages and disadvantages of water sampling models according tothe survey respondents.

Model Advantages DisadvantagesRuttner Simple Fails to close sometimes

Easy to use Many moving partsSampler is closed after filling Works bad when cold (-20◦C)Easy to sample at decideddepth

Need to transfer sample to labbottle

Take representative samples Can open by mistakeFills sampler smoothly Needs messengerLittle turbulence Long

Limnos Durable Labor intensiveEasy to useReliableAble to collect large amountof water at preferred depths

Niskin Single: easy to use Rosette system: hard to useRosette system: fast

Bottle Simple Labor intensive

The respondents answer regarding which materials are used in their water sam-pler can be seen in figure 3.4, as well as the wanted material in a water sampler.Acrylic is the most common material for the current water samplers as well as themost wanted material for a sampler, according to the respondents. It is also notedthat 42% of the respondents has no preferences or no answer regarding wantedmaterial for a sampler.

Figure 3.4. Survey result regarding current material and wanted material in sam-pling equipment.

19


Figure 3.5 show that most respondents, namely 33%, gather water samples oncea month. 75% of the respondents say the procedure involves 2 people and 50% saythe water sampling usually takes 1-3 hours. According to figure 3.6, the sampling

Figure 3.5. Survey result regarding how often the respondents gather water samples,how many people are needed and how many hours are spent on each water samplingsession.

interval throughout the water column differs widely. However, if surface sampling isdisregarded, the smallest interval is every 0.5 meter. The distribution of responsesfor maximum depth for sampling can also be seen in Figure 3.6.

Figure 3.6. Survey result regarding sampling interval and maximum depth.

20


The result shows that 58% of the respondents take samples at ≤20 m and theother 42% take samples at ≥40 m. A trend that respondents who sample at depths≤20 m need smaller sampling volumes is noted. The water properties that aremeasured in the sample can be seen in Figure 3.7. Both temperature and depth

Figure 3.7. Survey result regarding data gathering.

are essential to measure as 100% of the respondents measure these properties. Dateand time are also important information as 92% respectively 83% respondents needthese values. When measuring temperature, 75% need an accuracy of 0.1◦C, 17%need an accuracy of 0.01◦C and 8% need different accuracies depending on project.The respondents were asked about what actions they find important to perform toavoid contamination, see figure 3.8.

21


Figure 3.8. Survey result regarding actions to avoid contamination.

The result shows that 100% of the respondents thinks rinsing the laboratorybottle is important. 67% finds avoiding airspace important, which means filling thelaboratory bottle completely with water sample.The respondents were asked to rate different characteristics of a water samplingequipment from 1 (not important) to 5 (very important). A summary of the resultcan be seen in Table 3.2. The table shows that the most important characteristics,

Table 3.2. Characteristics of sampler rated according to importance

Characteristic 1 2 3 4 5 AverageEasy to use 8% 8% 17% 25% 42% 3.8Long durability 0% 0% 25% 42% 33% 4.1Fast sampling 0% 8% 42% 33% 17% 3.6High accuracy of sensor data 0% 0% 17% 58% 25% 4.1High accuracy of depth mea-surement

17% 17% 17% 25% 25% 3.3

Measure temperature 0% 0% 8% 42% 50% 4.4Take samples on differentdepths

25% 0% 8% 25% 42% 3.6

Take big water sample vol-umes

33% 17% 25% 25% 0% 2.4

Low price 0% 17% 67% 0% 17% 3.2Low weight 0% 0% 17% 58% 25% 4.1

rated ≥4, are ability to measure temperature, have a low weight, provide high accu-racy of sensor data and have a long durability. The rather important characteristics,rated ≥3, are easy to use, ability to take samples on different depths, fast sampling,provide high accuracy of depth measurement and low price. The least important

22

3.2. REQUIREMENT SPECIFICATION

characteristic, rated <3, is ability to take big water sample volumes. Table 3.3shows the identified challenges and risks with water sampling according to the re-spondents. The identified challenges evolve around weather conditions, walking inrough terrain and the field work being time and resource consuming. The identifiedrisks are about the danger of working in or close to lakes in case of an accident.

Table 3.3. Identified challenges and risks with water sampling according to therespondents.

Challenges RisksAccess to water site Fall in water

Avoid heavy equipment Danger to work in cold waterRequires several people Ice conditions can be difficult

Require boat Getting wetCarry samples back to lab in rough terrain Sampling in rivers

Windy/rough weather conditions Danger if something goes wrong withHard to sub sample the water boat or equipment

Problems when coldHard work to get to lake

Equipment freezes in winterTime consuming

3.2 Requirement specificationThe purpose of the system requirements are to compile the need from the literaturereading, the interviews and the survey. For a complete compilation of the definedrequirements, see Appendix C. The most important requirements are stated in thelist below.

1. The weight of the water sampling construction, including water sample, shallbe below or equal to 1 kg.

2. The water sample volume to be collected by the water sampler shall be mini-mum 500 ml.

3. Based on requirement 1 and 2, the empty sampling prototype shall weight lessthan 0.5 kg.

4. The full test system shall be able to gather water samples remotely.

5. The full test system shall be able to gather water samples at a depth of 10meters.

6. The accuracy of the depth measurement shall be ±0.25m.

23


7. The water sampler shall be able to measure temperature within the range0-20◦C.

8. The accuracy of the temperature measurement shall be ±0.1◦C.

9. Electronics shall be protected from water.

10. The full test system shall be able to gather water samples at the desired depthautomatically.

11. The drone shall keep a safety distance of at least 2 meters above the watersurface.

3.3 Problem formulationThe interviews and the survey shows that the main focus in the thesis is to maximizethe sample volume ability of the equipment with regards to the weight constraintof 1 kg. Aside of that, four possible problem areas have been identified:

1. As 75% of the researchers has a sample volume need of ≥1000 ml, can thesesamples be gathered with a drone despite the load constraint 1 kg?

2. As several samples throughout the water column often are gathered, how canthey be gathered in one sampling in order to increase the efficiency of thework process?

3. Considering the different volume need of the researchers’, how can the equip-ment gather the exact amount of water sample that is needed, in order toavoid wasting fly time of the drone and thereby increase the efficiency of thework process?

4. To increase the efficiency of the work process and avoid wasting water sampleon rinsing the laboratory bottle, how can the rinsing step of the laboratorybottle be removed?

Problem area 4 is identified as the most important to solve. Firstly because therinsing step is a common step for all researchers and secondly, it is a specific problemfor gathering samples using a drone, see section 3.3.1. After solving this problemarea, solutions to the other problem areas can be developed in order to furtherincrease the efficiency of the work process.

3.3.1 Optimized water sampling procedureThe current work process when taking water samples has been visualized in theflow chart seen in Figure 3.9 a). The current procedure starts with four consecutivesteps, followed by the question ”Is lab bottle rinsed?”. If the answer is ”no”, thelaboratory bottle has to be rinsed as an important step to avoid contamination.

24

3.3. PROBLEM FORMULATION

Figure 3.9. Visualization of the water sampling procedure were a) is the currentprocedure using a boat and b) is an optimized procedure using a drone.

25


Then the question ”Enough left to fill lab bottle?” is asked. The laboratory bottleneeds to be completely filled with water sample in order to avoid influence from freegases in the air. If the answer is ”yes”, the work flow continues undisrupted, if nomore samples are needed, with data gathering and transferring water sample intothe laboratory bottle. This is usually the case when water samples are collectedmanually, as the only critical weight constraint is how much the user is able to haulup. However, when sampling using a drone with the payload constraint of 1 kg,the step where water sample is used to rinse the laboratory bottle is considered anissue. Either, approximately twice the water sample volume needs to be gatheredin order to both rinse and fill the laboratory bottle, which means the volume of theaccessible water sample reduces by half. If the sampling equipment weights 0.5 kgaccording to requirement 1, the accessible water sample is only 0.25 l as 0.25 l hasbeen used to rinse the laboratory bottle. According to requirement 2, the minimumvolume to gather is 0.5 l. Another option is that the pilot has to fly back for morewater sample at that specific depth after the laboratory bottle is rinsed, in orderto fill the laboratory bottle. This option is considered time inefficient. Designing awater sampler in such way that the steps regarding rinsing is eliminated from theprocess would solve this issue. Figure 3.9 b) summarizes the planned, optimizedwork procedure using a drone. In order for the full system, consisting of both droneand sampler, to take water samples remotely, the sampler would need the ability toclose itself automatically at the desired depth. Preferably, the needed sampling data,namely depth, temperature, date and time, would be saved digitally to increase theaccuracy and save time. To summarize, the main focuses of the thesis is to designan automatic sampler, to maximize the sample volume capacity of the equipmentand to remove the step where the laboratory bottle is rinsed with water sample.These design adjustments of the water sampler are considered central when usingit with a drone for remote water sampling.

26

Chapter 4

Concept generation

This chapter contains a description of the design process based on the conclusionsdrawn in chapter 3. The purpose of the chapter is to answer RQ b). For the inertialconcept generation, the theory of inventive problem solving, TRIZ, was used. Adescription of the method, how it was used and the results from it are describedbelow. The theory resulted in interesting suggestions for solutions to contradictingscientific problems. Based on the ideas from the TRIZ method, different ideaswere investigated as described in the brainstorm section. To further develop theconcept generation, three workshop activities were performed. Two engineers withmechanical background from AF AB participated in the 30-60 min long workshopactivities. The different concepts were then evaluated and concepts for furtherdevelopment was chosen.

4.1 TRIZ - Theory of Inventive Problem Solving

TRIZ is a theory by G. Altshuller used to solve inventive problems in a analyticalway using different TRIZ tools [19]. The general method is to identify the specificscientific problem, reformulate it into a more abstract, general problem, and thenfind an equivalent, solved problem. The purpose of the problem abstraction is toexpand the solution span. The TRIZ tool used in this thesis is the contradictionmatrix. The purpose of the contradiction matrix is to direct the problem solvingprocess to investigate ideas that have been used previously to solve similar problems.A list of 40 inventive principles with concrete examples are complementing thecontradiction matrix. 39 engineering parameters are structured along the verticaland horizontal axes, and in the intersections, one to four principles to solve eachconflicting problem are stated. The 39x39 matrix is used by asking ”What elementof the system is in need of improvement? If improved, which element of the system isdeteriorated?” [19] (Kutz 2006, p. 622). A cropped part of the contradiction matrixcan be seen in figure 4.1. For the concept generation, the feature to improve wasnumber 8, volume of stationary, and the feature to preserve was number 2, weight ofstationary. This contradiction generated four suggestions of principles to solve the

27

CHAPTER 4. CONCEPT GENERATION

Figure 4.1. The contradiction matrix with chosen features to improve and preserve,and the suggested solving principles marked by the yellow crossroad.

problem; 35. Parameter changes, 10. Preliminary action, 19. Periodic action and14. Spheroidality - Curvature. The first principle, Parameter changes, suggestedto change the objects physical state, concentration, consistency, temperature orflexibility. If used to change the water sample parameters, these suggestions wouldmean a contaminated water sample and is therefore not plausible. However, thesuggestion led to the idea of using some sort of flexible container to hold the watersample. The next principle, Preliminary action, suggested to perform the requiredchange of an object before it is needed, with the example ”Sterilize all instrumentsneeded for a surgical procedure on a sealed tray” [20]. This suggestion inspiredthe idea of designing the water sampler in such way that it rinses the laboratorybottle automatically, or using pre rinsed or sterilized bottles. The next principle”Periodic action” suggested to use periodic or pulsating actions, elaborate withfrequency or magnitude of the periodic action or to use pauses between the pulsesto perform a different solution. The principle would be suiting if the thesis wasfocusing on problem area 1 in section 3.3.1, regarding taking samples larger than1000 ml. A solution could then cover taking several water samples as an periodicaction and merge them at the shore to the required volume. The fourth principleis ”Spheriodality - Curvature”, which suggested to use spherical surfaces and parts,and to go from linear to rotary motion. These suggestions led to the thought ofusing a rotary motion for the closing mechanisms instead of the linear motion oftodays water samplers.

4.1.1 Results from TRIZ

Three main results from working with TRIZ are further investigated in the Work-shop activities in section 4.2. The first is the idea of using a flexible, light-weight and

28

4.1. TRIZ - THEORY OF INVENTIVE PROBLEM SOLVING

expandable material to gather the water samples. The second is the idea of havinga rotary motion for the closing mechanism. The third is the idea of integrating thelaboratory bottle in the water sampling equipment initially, instead of transferringthe water sample into it after sampling. The third idea is further investigated priorto the workshop activities.

Integrated laboratory bottle

A way of integrating the laboratory bottle in the sampling equipment is to use ahollow, self-rinsing container, similar to today’s water samplers. The difference isthat the container is threaded in both ends to be able to screw on caps on both endsafter sampling, see figure 4.2. The sampling equipment, including closing mecha-nisms, is attached to the laboratory bottle and detached after the sampling. To

Figure 4.2. Sketch of double threaded container to make laboratory bottle similarto todays water samplers.

understand how to design a closing mechanism for the laboratory bottle, the clos-ing mechanisms of todays water samplers were examined. The closing mechanismused in the Ruttner and van Dorn sampler goes inside of the container, see figure4.3 a) and b). The closing mechanism of the Limnos sampler goes outside of thecontainer, see figure 4.3 c). For the integrated laboratory bottle idea, having theclosing mechanism inside the laboratory bottle is considered complex, as the labo-ratory bottle shall be easy to separate from the other sampling equipment. An ideaof a mechanism that screwed the lids onto the bottle or simply holding the lid tightagainst the bottle until the sampler were returned to the pilot to screw on the lidproperly can be seen in figure 4.4. The functionality of a diode, that allows flowin one direction but blocks in the other, led to the thought of using some sort ofvalve. The membrane-like valve of a snorkel further inspired using valves on theends of the laboratory bottle. The closing mechanisms of todays water samplersare connected to each other and closes both ends of the sampler simultaneously.Attaching the closing mechanism to the threads in the ends of the laboratory bottlein figure 4.2 instead, and thereby disconnecting the closing mechanisms from eachother, the ends of the bottle can be closed independently, see figure 4.5.

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Figure 4.3. Sketch of closing mechanism of a) van Dorn, b) Ruttner and c) Limnossampler, where a) and b) are inside the container, and c) is outside the container.

Figure 4.4. Basic sketch of a mechanism that screws on/holds the lids onto thelaboratory bottle.

4.2 Workshop activitiesThe first workshop session started with a visual presentation of the problem for-mulation, todays water sampling methods and equipment, the requirement specifi-cation of the water sampling equipment to be constructed and the ideas from theTRIZ method. The focus of the first workshop activity was defined in the followingquestions:

• How shall the water sample be taken?

• What type of container shall be used?

• How shall the water sampler close at the correct depth?

In the first session, two concepts were discussed. The first is the ”Plastic bag” insubsection 4.3.1, which focused on maximizing the volume while minimizing the

30

4.3. CONCEPTS

Figure 4.5. Basic sketch of from each other independent closing mechanisms thatallows water to flow in only one direction.

weight. The second concept was developed through discussion about different waysof closing the integrated laboratory bottle using valve functionality. The result isthe concept ”Wheel” in subsection 4.3.2, which is inspired by buckets with an openbottom. The combination of an expandable material as container and the Wheelvalve as closing mechanism was also discussed.In the second workshop activity, the participants discussed the results of the firstactivity and the new ideas that had developed. As an alternative to plastic for theexpandable material, different interesting woven materials were discussed. An ex-ample is silnylon, a silicon impregnated nylon fabric that is waterproof, lightweightand durable [21]. An alternative concept for the closing mechanism to the first valveidea was also developed, ”Cake” in subsection 4.3.3, which uses a rotating motioninstead of a linear. This concept is a mechatronic unit using a microcontroller.Another alternative concept, ”Combination” in subsection 4.3.4, is also discussed,which contains one valve type each from ”Wheel” and ”Cake”.In the third workshop activity, the decision was made to create functional proto-types to test the functionality of the chosen concept/s in section 4.4. The differentconcepts were discussed more in detail regarding how to design for assembly andhow the functional prototypes can be constructed.

4.3 Concepts

The different concepts are explained more in detail below. The first concept is theplastic bag idea, and the second concept is varying closing mechanisms with valvefunctionality with the integrated double-threaded laboratory bottle, called a) forWheel, b) for Cake and c) for Combination.

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4.3.1 Plastic Bag

Different ways of using flexible material were discussed which led to the followingideas. The first idea is to lower an empty plastic container, inspired by blood bags,into the water, see figure 4.6a. It does not contain any air, in order to sink easily.When it reaches the desired depth, it opens to let water in, using for example a pumpor a syringe. The plastic bag is a disposable product with the benefits of alwaysbeing sterilized and therefore avoiding contamination, and being very light-weightand therefore maximizing the sampling volume. However, according to section 1.6Ethical considerations, using disposable plastic products for environmental researchis not considered ethical because of the negative environmental impact of disposableplastic products [22]. Therefore, another version was discussed, namely to useexpandable material as the double threaded laboratory bottle. see figure 4.6b. The

Figure 4.6. Basic sketch of Plastic Bag concept where a) is the disposable plasticversion and b) is the expandable version for multiple use in empty and filled staterespectively.

material discussed was mainly silnylon but other expandable, water proof materialcould be used. The advantage of using a durable fabric material is that it can beused several times and have a low weight. The disadvantage is that if used severaltimes, the benefit of the disposable plastic being sterilized is lost. Expandableplastic and fabric containers are also considered difficult to handle after samplingwhen performing lab analyses, as they are not stiff.

4.3.2 Wheel

The concept for the closing mechanism is a valve design to be attached to thedouble threaded laboratory bottle. The concept has a similar design as the Ruttner

32

4.3. CONCEPTS

sampler. The valve idea consists of a disc that can move freely along a rod inside thevalve to let water in when the laboratory bottle is sinking and block water when thelaboratory bottle is pulled upwards, see figure 4.7. The bottle is attached to a wire

Figure 4.7. Wheel concept where a) is the cross-section of the valve, b) is thefunction when the bottle is sinking and c) is the function when the bottle is pulledup.

with marks to indicate at which depth the bottle currently is, alike todays depthmeasuring method. The benefits of this concept is that it is light weight, cheap andsimple. The downsides are that it relies on the self weight and water pressure tobe strong enough to push the disc up to let water in. Therefore, maximizing thediameter of the moving disc is essential. It is also unsure whether the water flowwill be strong enough to completely exchange the water sample inside the bottlewhen it sinks through the water column.

4.3.3 CakeThe second concept for the closing mechanism uses a rotary motion to rotate onedisc is over the other to open or close. The two discs have cut-out areas that closesthe valve when rotated to a certain angle. The inner disc is kept stationary andthe outer disc can rotate, see figure 4.8. The rotating motion is created using aservo that is controlled by a micro controller alternatively using magnets. Theconcept has depth perception by a sensor connected to the micro controller. Thebenefit of the concept is the exactness of the depth perception compared to themarked-wire method, that the water can flow more easily through the open cut-outareas compared to in the Wheel concept and that the opening and closing of thevalves are controllable and independent of the water flow. The downsides are thatit is heavier, complexer and more expensive than the other concepts and that theelectronics needs to be protected from the water in some sort of waterproof airchamber which will decrease its ability to sink.

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Figure 4.8. Cake concept where a) is the open valve when the bottle is sinkingand b) is the closed valve when the outer discs have rotated. Above the bottles, thecross-section of the discs are shown.

4.3.4 CombinationAs the two described valve ideas are independent units, using one of each valve ideais another concept. The first option is to have the Wheel unit on top of the bottleand the Cake unit in the bottom, see figure 4.9. The other option is to have theWheel valve in the bottom and the Cake valve in the top of the bottle, see figure4.10. The solution will weight less than the Cake concept and have a digital depthperception and controlled closing mechanism. The water flow through the bottlewould also be improved compared to the Wheel concept, as the Cake unit has amore open design. The downsides are that it will weight more than the Wheel. Thesinking ability of the two versions depends on the density of the Cake unit, as itcontains air chambers.

34

4.4. EVALUATION AND CHOICE OF CONCEPT

Figure 4.9. Combination of concepts where the Wheel is on the top and the Cakeis on the bottom, short name WT-CB (Wheel Top - Cake Bottom). The left is whenthe bottle is sinking and the right when the bottle is pulled up.

Figure 4.10. Combination of concepts where the Cake is on the top and the Wheelis on the bottom, short name CT-WB (Cake Top - Wheel Bottom). The left is whenthe bottle is sinking and the right when the bottle is pulled up.

4.4 Evaluation and choice of concept

In order to decide what solution is most suitable for remote sampling using a drone,two evaluations were done. The first is regarding how to attach the sampler to thedrone, which is based on the literature review in Chapter 2. The second evaluationis regarding what concept to continue with, which is based on the researchers needs

35


through interviews, the survey, the requirements and a comparison to the mostcommon sampler of the study group, namely the Ruttner sampler.

4.4.1 SuspensionDifferent options for attaching the water sampler on the drone were considered,based on table 2.2 in section 2.2. The most important characteristics of the at-tachment is having a low weight in order to keep the total load of the drone belowthe weight constraint of 1 kg, and being able to reach a depth of maximum 10meters. The investigated winches strong enough to reel up the water sampler fromthe depth of 10 meters need an external power supply of 12-24V, and the combinedpower supply and winch system is therefore considered too heavy. A pump systemcapable of pumping water from a depth of 10 meters including a power supply of12-24 V also exceeds the weight constraint. Using a syringe requires the drone tobe very close to or in the water, which is not plausible with the aerial drones withinthe scope. Therefore, the conclusion is to suspend the water sampler using a simple,lightweight wire. The disadvantages with the solution is that the load will oscillateand that the risk of entanglement is high, which has to be considered when usingand testing the full system. If a heavier payload was allowed by the drone, thewinch solution would be investigated more thoroughly.

4.4.2 Concept evaluationThe concepts were evaluated using the table of criterion for concept evaluation, tableD.1 shown in Appendix D. The reference sampler, Ruttner, were evaluated by theenvironmental researcher Erik Lundin. His motivations to the ratings can be seenin Appendix D. Based on his motivations of the reference sampler and the criteriontable, the concepts have been evaluated using a version of the Pugh matrix, seetable 4.1. In the Pugh matrix, the characteristics are weighted according to table3.2 in section 3.1.2. The weighting value is then multiplied with the rated valuefor each concept and summarized to give the result. The characteristic ”Level ofremoteness” was not included in the survey, but is given the weighted value 5.0, asit is crucial that the sampling equipment has full remote function when used witha drone. The Plastic Bag concept is abbreviated to Bag in table 4.1 and refers tothe blood bag-inspired version using a sterilized, disposable plastic bag.

36

4.4. EVALUATION AND CHOICE OF CONCEPT

Table 4.1. Pugh evaluation matrix

Characteristics Weight Ref Bag Wheel Cake CombiEasy to use 3.8 3 2 5 3 3Long durability 4.1 5 2 5 4 4Fast sampling 3.6 2 1 1 1 1High accuracy of sensor data 4.1 1 1 1 5 5High accuracy of depth mea-surement

3.3 2 2 2 5 5

Measure temperature 4.4 2 1 1 5 5Take samples on differentdepths

3.6 4 4 2 3 3

Take big water sample vol-umes

2.4 4 3 4 4 4

Low price 3.2 3 4 5 2 3Low weight 4.1 4 5 5 2 3Remote 5.0 3 5 5 5 5Result ∑ 124 114 137 150 158

The result of the Pugh matrix is an outspread score between the Plastic Bagwith the lowest score of 114 and the Combination with the highest score of 158. Thecommon characteristics of the Cake and Combination, which have the two highestscores, are the ability to measure temperature and depth with high accuracy. It ismotivated by the Pugh matrix to continue with the Cake and Combination concept.The matrix also motivates to continue with the Wheel concept, as it got higherscores than the reference. Another reason to continue with the Wheel is that boththe upper and lower Wheel units nevertheless are needed in the two versions of theCombination respectively. To summarize, a double-threaded container, two Cakeunits and two Wheel units will be further developed, see figure 4.11, in order toevaluate the best solution.

Figure 4.11. The four concepts to further develop, where a) uses two Wheel units,b) uses two Cake units and c) and d) uses one Cake unit and one Wheel unit.

37

Chapter 5

Construction of Prototypes

The chapter describes the further development of the concepts and the constructionof the prototypes. It begins with a brief discussion regarding the material choicesand manufacturing method throughout the making of the prototypes. Then thebase design is described, which is mutual for all concepts. It is followed by thedetailed design of the two different valve units Cake and Wheel.

5.1 Material choices and manufacturing methodThe purpose of designing the prototypes is to test and evaluate the function ofthe prototypes, meaning that their design is not necessarily optimal for productionand the materials used does not guarantee a water sample free of contamination.According to the survey answers in section 3.1.2, the wanted material for the watersampling equipment is acrylic, polythen, glass, teflon etc. When making the proto-types, these materials have been prioritized when possible throughout the construc-tion process to minimize the contamination risk. In situations where these materialswere unavailable, a rule of thumb was to use materials used in the food industry.This means that PET-plastic, PLA-plastic and silicon was chosen over for exampleABS-plastic or rubber when possible. In some cases, the design solution has beensimplified compared to the presumed manufacturing method in production. There-fore, the contamination risk of those materials who would not be needed in actualproduction was not taken into account. An example of such case is when a part issplit in several parts and glued together with epoxy glue, where the manufacturingmethod in production likely would be casting for the entire part.

5.2 Base designThe major idea for the water sampler is the double threaded, self-rinsing laboratorybottle with the ability to attach automatic valve units on both threads. The con-cepts to be constructed and evaluated use the same base design but have varyingvalve designs.

39

CHAPTER 5. CONSTRUCTION OF PROTOTYPES

Container

The container is a hollow cylinder, threaded in both ends. When the water sampleis captured inside the container, the upper valve unit is unscrewed and a sterilizedlid is screwed on. Then the container is turned around, and the other valve unitis unscrewed and a new sterilized lid is screwed on. The container is then used ina laboratory for water analyses. Figure 5.1 shows the laboratory bottle with andwithout the lids screwed on. The cylinder has a wide diameter of 100 mm, to create

Figure 5.1. Hollow laboratory bottle, without lids to the left and with lids to theright.

a strong water flow force through the container. The sample volume capacity ofthe water sampler can be changed by using a container with a different height withthe same threads. The height of the prototype laboratory bottle is 80 mm. Theinner diameter at the threads is 90 mm. The volume capacity of the laboratorybottle is approximately 610 ml. The container prototype is created by cutting offthe bottom of two plastic jars, heating the not-threaded end of one of the jars tomake it melt a little, and inserting the melted end into the other jar. Using glueand more heat, the two jars are connected into one, double-threaded cylinder. Theempty laboratory bottle weights 40 g and can hold 610 ml of water.

Threaded valve base

Both valve units need to have a threaded base, which suits the threads of thelaboratory bottle. It is created by removing the threads from spare lids of the jarsused to create the laboratory bottle. The threads are then glued inside a 3D-printedcylinder. The height of the cylinder is higher than the threads in order to gather

40

5.3. WHEEL UNIT

more water than the laboratory bottle can hold. This spare water sample ensuresno airspace in the laboratory bottle in case of a leaking valve. The suspension ofthe water sampler needs to be very light weight. Therefore, a synthetic fishing lineis tied onto three plastic brackets on each prototype, see figure 5.2.

Figure 5.2. Threaded base on which a valve unit will be attached. The marginis marked in the left figure. The three brackets for suspension are seen in the rightfigure.

5.3 Wheel unitThe mechanic unit is made of acrylic discs, glued onto the lid base, as can be seenin figure 5.3. Figure 5.4 shows the exploded view of the two Wheel units. The

Figure 5.3. CAD illustration of Wheel unit, where a) is the upper unit and b) isthe lower unit.

full Wheel concept can be seen in figure 5.5. To avoid leakage, silicon sealing was

41


Figure 5.4. Exploded view of the two Wheel units, where a) is the top unit and b)is the bottom view.

glued to the areas marked with red in the figure. After construction, the Wheelunits weights 85 g each including the threaded valve base. The full Wheel concept

Figure 5.5. CAD illustration of entire Wheel concept, with both upper and lowerWheel units and laboratory bottle. Silicon was glued to the red areas in the figure toavoid leakage.

weights 210 g (two Wheel units of 2x85 g and the laboratory bottle of 40 g) and iswell below the prototype weight constraint of 500 g.

42

5.4. CAKE UNIT

5.4 Cake unitThe purpose of the mechatronic system in the Cake unit is to output a rotatingmotion when the water sampler is at the inputted depth.

5.4.1 Design options for Cake unitWhen deciding how to create the rotating motion, different options were explored,focusing on requirement 9 regarding how to protect the electronics from water.Three design options for the mechatronic system were explored focusing on therotating motion.

Servo

The first idea is to use a servo to transfer rotational torque through the lid of theunit, see figure 5.6. The servo axis going through the lid increases the risk of water

Figure 5.6. Visualization of the servo idea, view from the side. The blue arrowsindicates where water can potentially leak into the enclosure.

leaking into the unit containing the electronic system, which is visualized with bluearrows in the figure. The servo needs an external power supply of 4.5-6 V, as theArduino Nano is not capable of providing enough current for the needed torque.

Magnets and servo

The focus of the second idea is to avoid the servo axis being transferred through thelid because of the risk of leakage. To make the servo rotate the outer disc withouthaving a drilled hole for the torque transfer, magnets are glued onto the servo andthe outer disc for contact-less torque transfer, see figure 5.7. When the servo isrotating, the magnets attached to the outer disc will follow the rotation becauseof the magnetic force. The casing is completely sealed to protect the electronicsfrom water. The idea requires a strong, non magnetic servo as the discs are pressed

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Figure 5.7. Visualization of the magnet and servo idea, view from the side.

against each other by the magnets. A risk with using strong magnets is the potentialmagnetic interference on the drone.

Magnets

The third idea is using repelling magnets and a linear actuator as a barrier, seefigure 5.8. When the unit reaches the inputted depth, the linear actuator is pulled

Figure 5.8. Visualization of the magnet idea, view from the side.

in and the disc is rotated by the strong magnets. The benefits of this design is thatthe rotating force is created without the risk of leakage. Once again, using strongmagnets leads to a risk of magnetic interference on the drone.

Evaluation

When evaluating the design options, the downsides of the options were compared.Both servos and linear actuators that are strong enough and very low weight are

44

5.4. CAKE UNIT

found to require an external power supply of 4.5-6 V. The major downside withthe servo idea is the risk of leakage into the Cake unit. The major downside withusing magnets is the risk of magnetic interference on the compass of the drone.Because of time limitations in the scope of the thesis, a proper investigation andrisk analysis of the magnetic interference on the drone was not possible. Therefore,the choice was to use the servo idea, as the risk of destroying the relatively cheapCake unit because of leakage is preferred over disturbing the compass of the droneduring flying.

5.4.2 Electric components of mechatronic systemThe electric components of the unit are chosen for being low-weight and small sizedin order to achieve the weight constraint of 500 g excluding water sample.

Control

To control the system, an Arduino Nano is used as microcontroller because of its lowweight of 9 grams and physically small size. Its purpose is to control the inputtedand outgoing signals.

Sensor

To measure the current depth and temperature, a water pressure sensor is used.According to requirement 5, the water sampler shall be able to gather water samplesfrom a depth of 10 meters. The accuracy of the depth measurement needs tobe ±0.25 m, according to requirement 6. According to requirement 7 and 8, themeasured temperature range needs to be between 0-20 ◦C and the accuracy of thetemperature measurement needs to be 0.1◦C. The water pressure Pwater at thedepth d of 10 meters is calculated according to

Pwater = ρgd (5.1)

where g is the gravitational force of 9.8 m/s2 and ρ is the density of water, ap-proximately 1000kg/m3 for fresh water with the temperature 4◦C [23]. The waterpressure is calculated to 0.98 Bar. The breakout board SparkFun MS5803-14BA,containing a pressure and temperature sensor is chosen because of its low weight,small size and ability to measure a water pressure of 14 Bar. It can be powereddirectly from the Arduino Nano and has a minimal resolution of 1 mBar, whichcorresponds to 0.01 m fresh water. The minimal resolution is well within the re-quirement 6 regarding depth accuracy. The maximal resolution of the sensor is 0.2mBar. The temperature range of the sensor is -40 to +85◦C. The accuracy ofthe temperature measurement is ±0.8◦C according to the sensor datasheet. How-ever, when investigating the graph ”Temperature error VS Temperature” in thedatasheet, the accuracy of the temperature is ±0.1◦C within the temperature rangeof 0-20◦C. The accuracy of the temperature is therefore sufficient, according torequirement 8.

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Servo

The servo is a SO5NF STD Servo with the weight 20 g and the torque 3.2 kg-cmif powered with 6 V. The diameter of the disc to be rotated is 10 cm and the servoaxis is to be placed in the center of the disc. The servo is capable of rotating amass of 0.64 kg at 5 cm from the servo/disc center. This corresponds to 6.3 N. Thefriction coefficient µ between two acrylic surfaces is 0.24 [24]. The kinetic frictionforce Fµ between the two discs is calculated according to

Fµ = µN = µ ·mg (5.2)

where N is the normal force of the disc, m is the mass of the disc of 0.02 kg andg is the gravitational force of 9.8 m/s2. The friction force is calculated to 0.05 N.This estimation shows that the servo is well dimensioned to handle the friction forcebetween the two discs when one disc rotates over the other. In reality, the discswill be pressed against each other with more force than the normal force to avoidleakage, which means the friction force will be increased. However, the marginbetween the capacity of the servo and the friction force is considered high enoughto handle an increased friction force.

Power supply

Two options were considered regarding the placement of the power supplies andmicrocontroller. The first option is to attach the microcontroller and the powersupplies onto the drone and have a cable going down to the water sampler. Thewater sampler needs to be at least 12 meters below the drone to safely gather samplesfrom a depth of 10 m, according to requirement 11 regarding the drones height abovethe water surface. A total of 6 wires are needed between the drone and the rest ofthe system, namely 3.3V, SDA, SCL to the sensor and SIG, V+ to the servo, anda common GND, see figure 5.13. The total wire length would then be 72 meters.A standard wire weights approximately 7g/m, which means 72 m weights 500 g.Considering the weight constraint of 1 kg and the requirement to gather at least500 ml water, it is not possible to use this approach. The other option is to integratethe microcontroller and power supplies in the Cake unit. The microcontroller andpower supplies would need to be reachable by the user to program the requireddepth and to exchanges batteries. This is solved by integrating enclosures in theunit, see figure 5.9.

Switch

A toggle switch is used to turn on and off the device. The switch has capacity tobreak 12V/20A.

46

5.4. CAKE UNIT

5.4.3 Construction of Cake unit

The mechatronic unit is made of a 3D printed waterproof casing that holds a servo,a micro controller, an on-off switch, batteries and a combined pressure and temper-ature sensor, shown in figure 5.9. The breakout board for the pressure sensor needs

Figure 5.9. CAD illustration of the content of the Cake unit.

to be protected from water, but the pressure sensor itself needs access to water.This is solved by a 3D-printed enclosure which is filled with epoxy glue to the edgeof the pressure sensor, see figure 5.10. The sensor enclosure is glued to the inside ofthe casing and a hole is drilled to the position of the sensor so it has contact with

Figure 5.10. Pressure sensor in its enclosure.

47


Figure 5.11. CAD illustration and photo of the bottom of the Cake unit, where thecontent in the enclosures can be accessed.

Figure 5.12. CAD illustrations and photo of the Cake unit.

the water. The user needs access to the microcontroller and the batteries. Thisis solved by integrating enclosures that can be opened from the bottom, see figure5.11. The enclosures are created by two acrylic jars with a threaded lid. The bot-tom of the jar is removed and inputted in the 3D-printed casing. To avoid leakage,an o-ring is placed around the threads. The o-ring is squeezed in the gap betweenthe lid and threads when the it is screwed on which creates the seal. Figure 5.12shows the CAD illustration and a photo of the full Cake unit. The purpose of theborder is to seal the edge of the rotating disc. A thin layer of silicon (0.5 mm) isattached on the inside of the border to improve its ability to seal properly.

48

5.4. CAKE UNIT

Electronics

The full schematics of the connections can be seen in figure 5.13. The micro con-

Figure 5.13. Schematic of the electric wiring of the Cake unit.

troller Arduino Nano needs a voltage supply of 7-12 V to function. It is thereforepowered with 9 V by three 3 V button cell batteries, connected in series. Thissolution takes up less space and weights less than using a 9 V battery directly. Theservo is powered by four 1.5 V cell batteries connected in series to create 6 V. Bothbattery packs are placed in one of the enclosures of the unit. As the GND wireis the common connection for both circuits, it is attached to the on-off switch tobe able to turn off all electronics when not in use. The pressure and temperaturesensor needs 3.3 V and is powered from the micro controller.

Communication and software

The sensor and microcontroller are communicating through I2C communication.The general logic of the software of the Cake unit can be seen in figure 5.14. Thestate ”Initialization” is were the variables are defined, the servo is rotated to itsopened position and the data variables are stored in a array. As an example,the variable desired depth is defined as 10 meters. The next state is a WHILE-loop were the current sensor depth is read as long as the variables curr depth anddesired depth are not equal. The two variables are constantly compared throughan IF-loop, and when they are equal, the servo is rotated to its closed position. The

49


Figure 5.14. General software logic of the system.

needed data is stored in the data-array and the code is ended. The code to readthe sensor signals is open source from SparkFun. A software test case of the systemcan be found in Appendix E.

5.4.4 Combination conceptThe finished Cake unit weights 320 g including batteries and threaded valve base.Because of the weight constraint of 500 g for the prototype, the concept with twoCake units is not possible. The conclusion is to use one Cake unit and one Wheelunit, the so called Combination concept. The total weight of the concept is 445 g(Cake unit weights 320 g, Wheel unit weights 85 g and laboratory bottle weights 40g), which is below the weight constraint. Both versions of the Combination conceptscan be seen in figure 5.15.

50

5.4. CAKE UNIT

Figure 5.15. Combination concept where a) is Cake unit on top and Wheel unit asbottom and b) is the Wheel unit on top and Cake unit as bottom.

51

Chapter 6

Testing and results

In this chapter, the design of the prototypes and the full test system are evaluatedthrough tests and observations during the tests. The design of the prototypes isevaluated by comparing them with each other and with the current most usedwater sampler. The purpose is to expand the answer to RQ b) found in chapter 4by confirming or disproving the design of prototypes. To answer RQ c), analyzes ofdrone data as well as general observations during water sampling with the dronesare done.

6.1 TestsThe purpose of the tests is to verify the requirements stated in section 3.2 and toobserve how the full test system behaves during the tests to answer RQ c). Thetests and requirements are summarized in table 6.1.

Table 6.1. Tests and reference to its originating requirement.

No. Tests Req.1. Weight the prototypes with and without water sample. 1, 2, 32. Take sample at 10 m depth. 53. Test reliability of design when gathering samples at different depths. 104. Observe if enclosures for electronics are leaking water. 95. Test depth accuracy of pressure sensor. 66. Test temperature accuracy of pressure sensor. 87. Take remote samples. 48. Observe full test system during water sampling. RQ c)

6.1.1 Weight of prototypes, Req. 1, 2, 3

To ensure that the prototypes are below the weight constraint of 1000 g includingwater sample, they were weighed according to test 1.

53

CHAPTER 6. TESTING AND RESULTS

Testing method

Each part was weighed separately using a scale with the resolution 1 gram. Theresult can be seen in table 6.2

Test result

Table 6.2. Weighed parts of the prototypes according to test 1.

Sampler Part Weight [g]Lab. Empty laboratory bottle (capacity 610 ml). 40

Laboratory lid (each). 17Filled laboratory bottle with lids (610 ml water). 685

Wheel Wheel unit (each). 85Empty Wheel concept. 210Filled Wheel concept (610 ml water). 820

Comb. Cake unit including batteries. 320Empty Combination concept. 445Filled Combination concept (610 ml water). 1055

Cake Hypothetically: Empty Cake concept. 680Ruttner Empty Ruttner sampler incl messenger weight (capac-

ity 220 ml).360

Filled Ruttner sampler incl messenger weight (capac-ity 220 ml).

580

The laboratory bottle has a capacity of 610 ml, which is 110 ml more than therequired minimal capacity of 500 ml. The result shows that the filled Wheel concept(lab.bottle + 2 Wheel units) is below the weight constraint despite this. The filledCombination concept (lab.bottle + Wheel unit + Cake unit) is above the weightconstraint with 55 grams, but it would meet the requirement if the laboratory bot-tle contained a smaller water volume. This means that both developed prototypeconcepts meet the weight-versus-volume requirements.The hypothetical weight of the Cake concept (lab.bottle + 2 Cake units) was cal-culated to 680 g, which is above the constraint of 500 g excluding water sample.Therefore, a prototype for the Cake concept was not constructed.The Ruttner sampler is the most used water sampler amongst the study groupwith 36% using it. The efficiency of the constructed prototypes is compared witha Ruttner sampler from Swedaq HB, model Hydro-X 0.22 liter, by calculating thegathered water sample volume per mass unit of the filled water sampler. The ratiobetween the volume V [ml] and mass m [g], V

m can be seen in table 6.3. The tableshows that the Wheel sampler is the most efficient at gathering big water volumesper mass unit. The Combination sampler is also more efficient than the Ruttnersampler, which is the least efficient. This result is expected as one of the main

54

6.1. TESTS

Table 6.3. Water sample volume per gram.

Water sampler Ratio [ml/g]

Ruttner sampler 220580 = 0.4 ml/g

Combination sampler 6101055 = 0.6 ml/g

Wheel sampler 610820 = 0.7 ml/g

focuses of the thesis is to develop samplers with an optimized ratio between volumeand weight.

6.1.2 Take samples at depth of 10 meters, Req 5

How well the samplers sinks to the depth 10 meter is investigated according to test2. The purpose of the test is to observe how the sampler behaves when sinkingin the water, but also to calculate their sinking speeds. The sinking speed of theprototypes is interesting to analyze, as the flight time of the drone is limited. Howwell the enclosures of the Cake unit are sealed when it is 10 meters under water isalso examined according to test 4.

Test method

The samplers were placed on the water surface with a wire with a mark every meter.The time it took for the samplers to reach a depth of 10 m was noted to calculatethe sinking speed. Five sinking tests/sampler was performed and the result can beseen in table 6.4. Cotton pads were placed inside each enclosure of the Cake unitto examine if they were properly sealed at the depth of 10 meters.

Test result

Table 6.4. Sinking speed of water sampler.

Water sampler: Ruttner Wheel Combi CT-WB1 Combi WT-CBTest 1, [s] 29 42 56 N/ATest 2, [s] 33 40 55 N/ATest 3, [s] 29 39 53 N/ATest 4, [s] 30 41 53 N/ATest 5, [s] 32 38 57 N/A

Average time [s] 30.6 40.0 54.8 N/AAverage speed [m/s] 0.33 0.25 0.18 N/A

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The test results shows that the average time for the Combination sampler tosink to a depth of 10 m is 54.8 s. This is a relatively long time considering thegeneral flight time of drones today. The average time for the Wheel sampler is 40s and the average time for the Ruttner sampler is 30.6 s. It is difficult to define asuitable sinking speed requirement for the water sampler, as it depends on the flighttime of the specific drone that is used. The affect the sinking speed will have on thefull test system will be further discussed in section 6.1.5. The Combination versionwith Cake unit on top and Wheel unit as bottom was the slowest with a speed of0.18 m/s. The Combination version with the Wheel unit on top and Cake unit asbottom did not sink properly, as the density of the Cake unit was too high. Thismeant that the prototype turned around and tried to sink in the wrong direction,with the Cake unit as a buoy. The Wheel unit is then blocking the water, whythe prototype simply could not sink, see figure 6.1. This issue is further discussed

Figure 6.1. Illustration of how the Combination concept with Wheel unit on topand Cake unit as bottom failed due to the floating Cake unit.

in chapter 7, subsection 7.2. The reason why the other Combination version couldsink is because when the Wheel unit started to take in water, its weight increasedwhich dragged the entire sampler down, see figure 6.2.General observations from the sinking tests is that the Ruttner sampler started tosink immediately, and the Wheel and Combination samplers needed to take in somewater to start sinking. They were also more prone to swing around in the state whenthey were breaking the surface than the Ruttner sampler. An aspect regarding thedesign of the Wheel sampler is that if the sampler is accidentally pulled up anddown at the wrong depth, it will let new water in.Concerning the seal of the enclosures, the cotton pads were damp after sampling.This means that the enclosures are not protecting the electronics from water. Thesealing between the thread and lid of the enclosures would need to be improved inorder to be used as waterproof enclosures for electronics.

1CT-WB: Cake top - Wheel bottom. WT-CB: Wheel top - Cake bottom.

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6.1. TESTS

Figure 6.2. Illustration of how the other Combination concept (CT-WB) sinks.

6.1.3 Water sample reliabilityThe water samplers shall be able to take reliable water samples at different depths.When taking water samples from different depths, it is important that the watersample is an exact representative of the water from the desired depth. An identifiedrisk with the valve design is that surface water is captured inside the containerand never exchanged when the water sampler is sinking through the water column.Therefore, the reliability of the water sample is tested according to test 3.

Test method

To test how well the water is exchanged in the samplers when sinking through thewater column, the water samplers were filled with colored water, see left referenceimage in figures 6.3 and 6.4. The sampler filled with colored water was lowered to adepth of 5 meters. Then the sampler was filled with new colored water and loweredto a depth of 10 meters. Five tests were performed for each sampler and each depth,a total of 20 tests. The samplers were filled with new colored water after every test.The results can be seen in figures 6.3 and 6.4. The test with the colored water isnot applicable for the function of the Ruttner sampler, as its closing mechanism isirreversible.

Test results

The result shows that the water is not fully exchanged after 5 meters for any ofthe two samplers. However, after 10 meters, it is fully exchanged for the Wheelsampler. A colored shade can be seen in the water in the Combination samplerafter 10 meters. This means that neither designs exchanges the water properly, butthe Wheel sampler is doing it better. After 5 m, the water in the Wheel samplerhas a slightly lighter blue color than the water in the Combination sampler, seemiddle image in figure 6.4 and 6.3. This further implies that the water is betterexchanged in the Wheel sampler. For researchers with the need of surface samples,

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Figure 6.3. Combination concept with Cake unit at top and wheel unit at bottom.The image to the right is the reference, the middle image is at a depth of 5 m andthe image to the left is at 10 m.

Figure 6.4. Wheel concept. The image to the right is the reference, the middleimage is at a depth of 5 m and the image to the left is at 10 m.

the prototypes could still work. However, they are considered unreliable for watersampling at depths in their current form.

6.1.4 Depth and temperature of pressure sensor

According to test 6 and 8, the accuracy of the depth and temperature measurementsof the pressure sensor shall be tested. The subsystem including the pressure sensor,microcontroller, servo and batteries was also tested to verify the system.

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6.1. TESTS

Test method

For the general test of the depth and temperature measurement, the pressure sensorwas connected to the microcontroller. The sensor was placed in a high transparentjar with a water level of 0.2 m, see figure 6.5. The jar was marked every 0.05 m

Figure 6.5. Test of depth and temperature measurement of pressure sensor.

to observe the actual depth of the sensor. For the temperature measurement, a labthermometer from TFA Dostmann 30.1013 was used. It has an accuracy of ±0.8◦Cwhich is not sufficient to meet the requirement, but it is used as reference. The Ar-duino monitor showed the sensor depth and temperature output which is comparedto the measured depth and temperature. The result can be seen in tables 6.5 and6.6.To test the entire subsystem, the components were connected according to the elec-tronics schematic in figure 5.13. When the pressure sensor was within the interval±0.01 cm of the desired depth, the servo should rotate.

Test result

The result shows that the outputted sensor measurements are close to the actualmeasurements.

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Table 6.5. Actual and outputted depth of sensor.

Actual depth [m] 0.05 0.10 0.15 0.20Sensor depth output [m] 0.054 0.093 0.152 0.201

Table 6.6. Actual and outputted temperature of sensor.

Actual temperature [◦C] 5 10 15 20Sensor temp. output [◦C] 5.2 10.4 14.6 20.2

In order to draw better conclusions, more tests should be performed closer to the re-ality of the application. The depth measurement should be tested at a more realisticdepth interval, for example every 0.5 meter down to 10 meters. The temperaturemeasurement should be tested using a more accurate thermometer.The test of the entire subsystem proved successful. The servo rotated when the sen-sor was within the desired depth interval of 0.1±0.01 m. To draw better conclusions,the test should be repeated at a more realistic depth for the application.

6.1.5 Full test system

The full test system consists of a water sampler and a drone. Two drones of differentsizes were used, a smaller quadrotor and a bigger octorotor. Table 6.7 summarizessome drone specifications of the two models. The reason to test the full test system

Table 6.7. Specifications of the two drones used for tests.

Spec. Quadrotor OctorotorFrame 450 mm frame build as

quad/X4Tarot 960 Octorotor, build asX8

Motor T-motor 3508-20, 580KV T-motor MN4014-11 330KVPropellers 11” 17” upper/18” lowerFC Pixhawk 2 with 433MHz

telemetry3DR Pixhawk with 433MHztelemetry

ESC Hobbywing X-Rotor 40A Hobbywing X-Rotor 40ABatteries 4S single lipo battery, total

capacity 5000 mAh6S dual lipo batteries, totalcapacity 20 000 mAh

Weight 1.2 kg without batteries 3.8 kg without batteriesFlight time Approx. 15 min without pay-

loadApprox. 20 min without pay-load

in reality is to examine how the drone and the water sampler behave and getsaffected by water sampling to be able to answer RQ c). How the drones are affectedby water sampling is examined through analyzes of the log files and observations.The log files are analyzed through the current consumption before and after watersampling, and how well the drone follows the desired roll, pitch and yaw angle

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6.1. TESTS

before and after water sampling, see figure 6.6. The roll, pitch and yaw angles are

Figure 6.6. Roll, pitch and yaw angles of drone.

measured in degrees. The roll angles are defined as negative if left roll and positiveif right roll. Pitch forward is defined as a negative angle and pitch backward is apositive angle. The yaw angle is defined as zero when angled to the north. How thewater samplers are affected is investigated through observations.

Test method

Two different tests were performed for each drone. The first was a no payload testto use as reference, and the second was a test were the Wheel sampler was usedto gather a water sample. The Combination sampler was not used in these testsbecause of its poor ability to sink. The water sample was collected from a big bucketplaced on the ground. Because of the safety of the drones, field tests in a lake wasnot performed. On the test day, the weather was cloudy with an air temperatureof approximately 19 ◦C and a wind speed of 5 m/s.

Test result: Quadrotor

The first test is a no payload test. The current consumption is approximately 11A when flying with no payload, see figure 6.7. The second test is when the Wheelsampler is attached to the drone for actual water sampling.The first observations was the risk of the sampler’s wire to get stuck in the pro-pellers during take off and landing. The wire is a transparent fishing line which isvery hard to see. To avoid this risk, the wire was made shorter than 12 meters, andthe sampler ended up at approximately 2 meters below the drone. The sampler wasthen dragged along the ground during take off and landing, to ensure that the wirewas straight and would not get stuck in the propellers. This way of flying sets highdemands of the robustness of the water sampler as well as its capability to hold thewater sample.When flying with the empty Wheel sampler of 210 g as payload, the current in-creased to approximately 12 A. After 425 seconds, the water sample is gathered

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Figure 6.7. The current of the Quadrotor during no external payload. The blueline is the altitude [m], and the red line is the current [A].

which increases the payload to 820 g. The current is then increased to approxi-mately 20 A, see figure 6.8. The current increases from 11 A to 20 A when the

Figure 6.8. The current of the Quadrotor when gathering a water sample with theWheel sampler at 425 seconds, see dotted line. The blue line is the altitude [m], andthe red line is the current [A].

payload increases from 0 g to 820 g. Suppose that the current increases proportion-ally with the payload. Then, when the payload is increased to it required maximumvalue 1000 g, the current would increase to 22 A. That would mean that the currentconsumption is doubled because of water sampling. Table 6.7 shows that the flighttime of the Quadrotor is approximately 15 minutes without payload. Because ofthe increased current consumption, the battery life would be half, and thereby, theflight time would be half - about 7.5 minutes, when used for water sampling.A decreased stability of the drone was observed when flying with a suspended pay-load. It was harder to control the drone as the water sampler was oscillating below

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6.1. TESTS

it. It was especially noted when the water sampler was lowered into the bucket.The sampler was swinging under the drone, which interfered with the drone stabilityand made it harder to fly. At 310 s, the pilot hovered above the bucket and triedto place the water sampler in the bucket. The water sample is gathered around 425s, and the actual water sampler took approximately 115 seconds due to the dronebeing hard to control. Figures 6.9, 6.10 and 6.11 show the desired and actual dronesangles during the time period of the water sampling. The conclusion is that the

Figure 6.9. The desired yaw and the actual yaw of the Quadrotor during watersampling. The red line is the desired yaw and the blue line is the actual yaw. Noremarkable deviation is noted in the time interval between 310 and 425 s.

Figure 6.10. The desired pitch and the actual pitch of the Quadrotor during watersampling. The red line is the desired pitch and the blue line is the actual pitch. Thedeviation is notable between 310 s and 425 s.

yaw angle is not affected notably during the hovering and water sampling. Thisis expected, as the yaw angle is not really affected by sudden lateral movements.However, the pitch and roll angles are affected by the suspended payload. This wasobserved during the tests and confirmed by the graphs.

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Figure 6.11. The desired roll and the actual roll of the Quadrotor during watersampling. The red line is the desired roll and the blue line is the actual roll. Thedeviation is notable between 310 s and 425 s.

Test results: Octorotor

The first test is a no payload test. The current consumption is approximately35 A when flying with no payload, see figure 6.12 The second test is to take a

Figure 6.12. The current of the Octorotor during no external load. The blue lineis the altitude [m], and the red line is the current [A].

water sample with the Wheel sampler. The current is approximately 35 A whenflying with the empty Wheel sampler, a payload of 210 g. The current increasedto approximately 40 A when the water is gathered after 150 seconds, which meanswhen the payload is 820 g, see figure 6.13. The current consumption is increasinga lot less for the Octorotor than for the Quadrotor. Supposing that the currentconsumption increased proportionally, the current consumption would be 41 A ifthe payload increased to 1000 g. According to table 6.7, the flight time of theOctorotor is approximately 20 minutes without payload. That means that theflight time of the drone would be decreased to approximately 16.5 minutes, if thepayload was 1 kg.

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Figure 6.13. The current of the Octorotor when gathering a water sample at ap-proximately 150 s with the Wheel sampler, see dotted line. The blue line is thealtitude [m], and the red line is the current [A].

When flying the Octorotor with the suspended payload, the drone was a lot morestable and easy to control. The water sampler was placed in the bucket and asample was gathered between 140 s and 150 s, which means the water samplingtook approximately 10 s. This time value can be compared to the time value ofthe Quadrotor performing the same task, which took 115 s. Figures 6.14, 6.15 and6.16 show the desired and actual drones angles during the time period of the watersampling. The interpretation is that the drone is handling the suspended payload

Figure 6.14. The desired yaw and the actual yaw of the Octorotor during watersampling. The red line is the desired yaw and the blue line is the actual yaw. Noremarkable deviation is noted.

of 820 g well, even though the payload is oscillating. Neither the yaw, roll or pitchangle are affected remarkably according to the observations and the drone data.

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Figure 6.15. The desired pitch and the actual pitch of the Octorotor during watersampling. The red line is the desired pitch and the blue line is the actual pitch. Noremarkable deviation is noted.

Figure 6.16. The desired roll and the actual roll of the Octorotor during watersampling. The red line is the desired roll and the blue line is the actual roll. Noremarkable deviation is noted.

The conclusion is that the Octorotor is a lot less affected by water sampling thanthe Quadrotor, both considering current consumption and control. The currentconsumption will impact the flight time of the drone, and a shorter flight timemeans that the user needs to change the batteries more often.

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Test results: Summary

An overview of the test results when testing the full test system can be seen in table6.8. The current consumption is the average value during the flights. The current

Table 6.8. Summary of test results.

Quadrotor OctorotorCurrent No load 11 35

consumption [A] Max. load2 22 41Increase [%] 100 17

Flight time [min] No load 15 20Max. load 7.5 16.5

Stability of Yaw Not affected Not affectedcontrol angles Pitch Affected Not affected(with payload) Roll Affected Not affected

consumption of the Quadrotor increases with 100% when it carries a payload of 1000g, compared to 17% for the Octorotor. The flight time decreases correspondingly.The stability of the control angles pitch and roll are affected when the Quadrotorhas the payload, but not the yaw. For the Octorotor, the stability of all controlangles are unaffected. Derived from the sinking speed tests in section 6.1.2, theCombination sampler sinks to the depth 10 m in approximately 55 s. If the Com-bination sampler is used together with the Quadrotor for sampling at a depth of 10m, with an already significantly decreased flight time because of the barload, therelatively slow sinking speed would further affect the drones suitability to gatherwater samples in a negative way. In terms of maintaining a preferred flight time,both the type of drone and the sinking speed of the sampler makes a big difference.

2Max. load refers to a payload of 1000 g.

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Chapter 7

Discussion and Future work

This chapter contains a discussion about the overall thesis procedure and results anda conclusion, which answers the main RQ. The chapter is ended with suggestionsfor future work.

7.1 DiscussionThe research conducted in this thesis is analyzed in order to draw conclusion aboutthe results. The discussion is divided into four sections corresponding to the mainresearch question and the three underlying research questions.

7.1.1 Regarding the pre-study

The first underlying research question is ”What challenges and needs do the re-searchers have regarding the water sampling procedure they use today?”. Theresearch method to answer the question was to perform a SOTA, through inter-views with several researchers and a survey. The answer to the research question issummarized in table 7.1.

Table 7.1. Summary RQ 1

What challenges and needs do the researchers have regarding thewater sampling procedure they use today?The purpose is to gather a sample that is a representative of the water at aspecific depth interval.Depending on study, different approaches to avoid contamination are used.Material choice, sterilized/rinsed equipment, ensure no headspace and protectsample from sunlight are examples of such approaches.The most important info to note is depth, temperature, date and time.Challenges with sampling is to reach the site, requires boat, carry equipmentin rough terrain, bad weather conditions, time consuming.Risks are to fall in the lake, if it is icy, sampling in rivers, etc.

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Discussion

Some interviews were held in Swedish or Norwegian and translated into Englishwhich increases the risk of information getting lost. The interviews were semi-structured, with the benefit of being flexible. A result of the flexibility is that allinterviews differs slightly as the focus can be different depending on the respondent.The answers can also be biased as they are interpreted by the author.Regarding the survey, some of the questions in the survey were inexplicit, which re-sulted in inexplicit answers. An example is the question ”What approximate pricedo you think is reasonable for a water sample equipment?”, where the answers dif-fered from 5000 SEK to 100000 SEK because there was a confusion whether thequestion included the drone or not. The question referred to a sampling equipmentexcluding the drone. Another example of an inexplicit question was ”When takingthe samples (and not later in the lab), what data would you like to measure/in-formation would you like to note when taking water samples?”, which not onlygenerated answers about what they would wish to measure in the future, but alsowhat they measure today. This was a problem as some respondents only answeredwhat they want to measure, and some answered what they want to measure andwhat they already measure, which made the answers hard to map. The questionreferred to what they would want to measure in the future, not including what theyalready measure.

7.1.2 Regarding the design and prototypesThe second underlying research question is ”How can a water sampler be designedto a given drone to automate the water sampling process?”. It was investigated andanswered through the problem formulation in the pre-study, the concept generation,the design of prototypes and the tests of the prototypes. The answer to the researchquestion is summarized in table 7.2.

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How can a water sampler be designed to a given drone to automatethe water sampling process?The conclusion was that to design a sampler to be used remotely with adrone, it needs to have full automatic function, with a maximized water samplecapacity and without the inefficient rinsing step of the laboratory bottle.The contradicting problem weight vs volume was solved through TRIZ-methods.A design where the laboratory bottle was integrated in the water sampler wascreated.The closing mechanism was created by independent threaded valve units thatcould be combined.The design of the water sampler can easily be made modular by exchangingthe height of the laboratory bottle.The tests of the Wheel prototype showed that it is capable of gathering surfacewater samples. It has problems when gathering samples at different depths.The tests of the Combination prototype showed that it needs to be redoneto gather water samples. It also has problems when gathering samples atdifferent depths.

Discussion

The result from the pre-study was four problem formulations. The thesis focusedon the fourth problem area regarding how to remove the rinsing step of laboratorybottle to avoid gathering unnecessary water sample. The other problem areas werealso considered interesting to analyze, but as the chosen problem area occurs in allother problem areas, it was prioritized to focus on that area first.Two main concepts were discussed in the thesis, the plastic bag and the laboratorybottle with valve units. Within the laboratory bottle concept, several subconceptsfor valve units were discussed. Having more than two main concepts would haveincreased the chance of finding other interesting ideas for solutions. More subcon-cepts for the valves would also increase the solution span.The evaluation of the concepts were made through a list of criterion, see AppendixD. The list of criterion were produced based on the authors interpretations fromthe interviews and survey. This increases the risk for misinterpretations having animpact in the chosen concept. The evaluation of the concepts was performed bythe author alone, which increases the risk of a subjective evaluation. To decreasethe risk of being subjective, the reference Ruttner sampler was evaluated by anenvironmental researcher from the study group.An option that was considered in the thesis was to test the concept ideas usingsoftware tools and simulations. An example of a software tool considered for thisthesis is FloEFD, which simulates flow through CAD models. Using such tool couldbe helpful for the design and evaluation of concepts. The option was neglected be-

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cause of budget and time limitations and the steep learning curve of the software.However, it is recommended for further development of the concepts.As the prototypes are designed to test different functional requirements, the mate-rial choices and manufacturing methods can differ from that of the actual, producedproduct. This means that the components, weight and dimensions could be differ-ent from the chosen ones, especially for the Cake unit. More on this subject can befound in section 5.1.Making the closing mechanisms of the valve units completely sealed proved to bechallenging. In the thesis, more focus on sealing would have been beneficial to havemore realistic prototypes.The Cake units density was too high for the unit to sink properly. This subject isfurther investigated and discussed in section 7.2.The rotation of the Cake unit was not functioning properly because of friction issuesin the prototype. This subject is further discussed in section 7.2.Regarding the tests of the prototypes in general, more tests would increase the ac-curacy of the data. For test 1, weight of prototypes, the accuracy of the scale is 1gram. This accuracy is considered high enough for the weight tests.Test 2, take sample at 10 m depth, have several error sources. The depth is measuredby marks on the wire. With the mark-the-wire-method it is hard to verify that thesampler sinks straight. The pressure sensor was not used for the tests, because ofthe problems with the Cake unit discussed in section 7.2. Regarding sinking speed,the wire was held straight to control the direction of the prototype samplers andto stop them from swinging around, as the light weight prototype samplers neededto take in some water to start sinking. The holding of the straight wire might havedecelerated the prototypes. Regarding the protection of electronics, the cotton padswere damp after sampling. As the entire inside of the Cake unit is covered in heatglue, the only components exposed to the enclosures were the battery pack and themicrocontroller. The battery pack was covered with heat shrink which worked asa protection from moist. The microcontroller was directly exposed to the moist,which means that it would need a better protection in the future. However, themoist was not bad enough to affect the functionality of the prototype notably.Test 3, water sample reliability, could have been performed using more exact meth-ods than observing colored water. The test results can only be used to indicate aproblem with the sample reliability that would need to be solved in the future. Away of verifying the reliability of the water sample could be to gather water samplesat the same depth using the prototypes and using the Ruttner sampler. The wa-ter samples would then be analyzed in a chemical laboratory to measure the waterchemistry of all samples with the sample from the Ruttner sampler as reference. Ofcourse, the water environment could be similar at different depths and the resultwould then be misleading. The water environment would need to be measurablydifferent at different depths for this type of test.For test 4, regarding the depth and temperature of the pressure sensor, the accuracyof the used laboratory thermometer is not accurate enough to verify the temper-ature from the pressure sensor. This would be solved by using a more accurate

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7.1. DISCUSSION

thermometer.

7.1.3 Regarding the full test systemThe third underlying research question is ”How is the full test system1 affectedby water sampling?”. It was investigated through field tests were drone data wasanalyzed and observations were made. The answer to the research question issummarized in table 7.3.


How is the full test system affected by water sampling?When the smaller drone, the Quadrotor, was used as carrier, both currentconsumption and stability of the drone was affected notably.When the bigger drone, the Octorotor, was used as carrier, the current con-sumption was notably affected but not the stability of the drone.During take-off and landing, the prototypes were handled very roughly andneeds to be robustly designed for this application.

Discussion

The conclusions made regarding stability based on the pitch and roll angle devi-ations in the Quadrotor case would be better supported if more tests had beenperformed. If the routes were programmed, the log data from different payloadcases could be analyzed and more scientific conclusions could be drawn. As it isnow, a possibility is that the deviation of the pitch and roll angles in the Quadrotorcase is totally normal when hovering, and not a reaction of the suspended payload.However, the conclusion that the stability of the Quadrotor decreased because ofthe suspended payload persists, because it noted through observations when per-forming the field tests.The weather conditions could have changed during the different flights which wouldaffect the test results.The field tests were performed using an experienced pilot, which would affect thetest results.The exact test environment is very hard to recreate for repeatability. The conclu-sions based on the results from the field tests are therefore very specific for the fieldtests performed in this thesis and has the purpose of understanding the feasibilityof and problems with the application, rather than function as scientific proof.

7.1.4 ConclusionThe main research question is ”Can a water sampler be designed to a given drone toautomate the water sampling process?”. The strategy to answer the research ques-

1The full test system refers to the combined system of a drone and water sampler.

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tion was through investigation of the three underlying research questions, whichhave been separately answered above. Working with the underlying research ques-tions resulted in physical prototypes being designed which were used for field testswith drones. The field tests clearly shows that the designed water sampler is suitablefor water sampling using a drone, being a proof of concept. Due to the narrow timeframe of the project and the specific application of water sampling, the methodto undertake the main research question has been to transfer the concept ideas,developed based on the pre-study, to physical models through rapid prototypingmethods. The understanding of the technical difficulties for this specific applicationhas been developed in an exploratory way through the design and the testing ofthe prototypes. This rapid prototyping method has had both benefits and disad-vantages in the thesis, compared to for example substantiate design decisions basedon calculations and simulations. A benefit is that the full design focus could be onbuilding the physical prototypes quickly and analyze and learn more about theiractual design both independently and together with the drones. Another benefitwith having physical prototypes is to show that the concept, namely water samplingusing drones, works. In that way, the thesis is a feasibility study that investigatesthe appropriateness of using the full test system for water sampling. Therefore,using physical prototypes has been very useful when investigating the appropriate-ness of the application. A disadvantage with this rapid prototyping method is thatmany design decisions are based on assumptions by the author. Some of the issueswith the design of the prototypes could probably have been avoided if more carefulcalculations and simulations had been performed throughout the design process.The thesis shows that despite technical problems with the prototypes and despitetheir design being mostly based on assumptions, the prototypes can be used tocollect water samples with a drone. The thesis also shows some new, interestingproblem areas with the application. One problem area is deciding on what type ofwater sampler to design. The term ”Water sampling” is very broad and includesmany different types of environmental studies with different purposes. The studygroup declared a variety of needs and requirements, sometimes opposing each other.Another problem area is regarding the design of the sampler. The contradictionsof designing a product that is very light weight, able to sink fast and relativelyvoluminous, is a challenge considering for example issues with density. Yet anotherproblem area is regarding the full test system. Using the smaller Quadrotor forwater sampling, the flight time decreased to approximately 7.5 min. In combina-tion with the drone being harder to control with the payload, it is questionablehow many water samples can be gathered before the drone batteries needs to bechanged. This problem is easily solved by changing the drone model to for examplethe Octorotor, with the disadvantage of increased cost.

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7.2. FUTURE WORK

7.2 Future workThis section discusses suggestions for future work. The suggestions were not per-formed in the thesis because of time and budget constraints or because the sugges-tion was out of the scope.

Density of Cake unit

In order to have a better functioning prototype, some calculations were made ofthe density. The issue with the floating of the Cake unit was investigated throughcalculation of the density of the unit. The volume of the unit was approximated bythe water displacement method were the change of water level when the object wasplaced in the water was noted. The volume of the unit is VCake = 0.00045m3. Themass of the unit before being filled with heat glue was mCake,1 = 0.317kg and afterbeing filled with heat glue mCake,2 = 0.365kg. The density of the unit is calculatedaccording to

ρ = m

V(7.1)

to ρCake,1 = 704.4kg/m3 before being filled and ρCake,2 = 811.1kg/m3 after beingfilled. In order to sink, it needs to have higher density than water, which hasρH2O = 999.7kg/m3 at 10◦C [25]. This means the unit would need a weight ofat least 0.45 kg in order to have a higher density and thereby sink in water, if thevolume is kept constant. The full prototype would then weight 0.574 kg includingthe Steering wheel unit and the container. This solution is not plausible consideringthe weight constraint of the full prototype being 0.5 kg. The conclusion is that theCake unit needs to be redesigned into a more dense unit, focusing on lowering thevolume of the unit.

Closing mechanism of Cake unit

The closing mechanism of the Cake unit consisted of the rotation of a plastic diskusing a servo motor. Two major problems were observed in the function prototypeof the Cake unit. The first problem was that the servo motor did not rotate properlyand sometimes stopped rotating. Through a investigation of the unit the followingissues were identified as reasons for this.

• The motor axis is not completely perpendicular to the horizontal plane, whichaffects the rotation of the disk. The border of the unit lowers the tolerance torotate with a differentiating radius. The issue can be solved by reassemblingthe servo motor and ensure it is fastened completely perpendicular to thehorizontal plane.

• The proper balance of torque when tightening the bolt of the motor axis isdifficult to find. The bolt needs to be tightened enough to ensure there is noleakage between the two plastic surfaces but loose enough to minimize the

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torque needed from the servo motor to rotate the disk. The friction betweenthe two surfaces, and thereby the needed torque, can be lowered by changingthe material in the contact area to a material with a lower friction coefficient,for example PTFE (Teflon).

• The friction of the sealing between the motor axis and the fixed disk couldbe too high. The sealing was made by a heatshrink tube that was shapedto create a sealed space for the axis to rotate in but also a sealed surfaceagainst the disk hole. A better solution to seal the hole for the axis would bea waterproof bearing with proper dimensions.

The conclusion is that the described issues increased the needed motor torque abovethe accessible motor torque. Using a stronger motor is therefor an alternativesolution. However, it is advised to solve the described issues first, as a strongermotor usually is bigger and weights more.The second major problem was that the unit was leaking water between the twosurfaces. The leaking problem cohere with the rotation issues to some extent, butsome other issues described below were also identified.

• The force that pushes the disk against the surface is distributed triangularlyacross the disk, see figure 7.1 As stated above, a balance between tightening

Figure 7.1. The triangular force distribution when the two discs are pressed againsteach other at the servo axis position only.

the motor axis bolt too hard and too loose must be found. If the disk isbeing tightening it too hard, the outer diameter of the plastic disk starts tobend upwards, which leads to a leaking design and possibly deformation ofthe disk. A solution is to distribute the force more evenly across the surfaceby extending the motor axis to put pressure on the entire disk instead of atone point. Another solution is to make the rotating disk stiffer by changingthe material or thickness of it.

• Proper sealing to leak prone areas like the cutout areas are needed. A solutionis to cut a track around the cutout areas using a mill, and place a o-ring in thetrack, see figure 7.2 The other disk would need a beveled edge to easily rotateover the o-ring. The shape of the cutouts can be changed into a standard

76

7.2. FUTURE WORK

Figure 7.2. Placement of o-ring for a better sealed unit. The o-rings should beplaced between the two disks.

shape like a circle in order to find proper standard o-rings. However, thereason for the current shape of the cutouts is to maximize the water flowthrough the unit which would need to be accounted for if changed.

Other

Future research regarding the feasibility of the system, consisting of drone and sam-pler, for water sampling would be highly interesting. The thesis brings up someaspects of the feasibility of using drones and the proposed water samplers for re-mote water sampling, mainly regarding flight time of the drones and drone stability,but this could be investigated more thoroughly.An idea that was discussed in the thesis was to implement a sensor to confirm thatthe servo position definitely is at the closed position when it should. This redun-dancy of the position measurement is to prevent errors if the servo would get stuckwhile rotating.Communication between the sampler and the user was also considered. It wouldease the process and shorten the consumed time of the water sampling if the userconstantly knew at what depth the sampler was at and when the sample was gath-ered.The method to measure depth of the Wheel concept is using the mark-the-wiremethod. This method is not sufficient when gathering water samples using a drone,as it requires a human to see the marks on the wire. Implementing another depthmeasurement method for the Wheel concept is therefore essential. The Wheel con-cept does not measure temperature which would need to be implemented. Thiscan be done by simply using an analogue thermometer, or by using more complexsolutions.The design of the prototypes could be better designed to sink in water by designingthe samplers differently, for example by adding fins. Using software to simulate howthe design is behaving in water would be a good way of doing this.If drones with other bar load constraints were used, a solution that used a winch

77


would be very interesting to investigate. Being able to elevate the sampler fromand to the drone would simplify the take off and landing procedure and when trans-porting between the lake and the pilot, as the wire would not risk getting stuck inpropellers or oscillate during transportation.Considering the risk of the relatively cheap water sampler getting stuck in the out-door environment, a release mechanism would be a good implementation. Froma budget perspective, it is more important to protect the drone than the watersampler.

78

Bibliography

[1] http://www.interact-eu.net/

[2] Nyamko Sabuni, Green Advisor Report 2017. New perspectives when the dronesfly over climate change research.

[3] Maria Ader, David Axelsson 2017 Drones in arctic environments.(http://kth.diva-portal.org/smash/get/diva2:1158400/FULLTEXT01.pdf)

[4] Vattenprovtagare [ONLINE] Available at: http://www.swedaq.se/index.php/vattenprovtagare[Accessed 28 March 2018]

[5] LIMNOS water sampler [ONLINE] Available at:https://www.hydrobios.de/product/limnos-water-sampler/ [Accessed 28March 2018]

[6] Water sampler [ONLINE] Available at: http://www.act-us.info/ [Accessed 29March 2018]

[7] Office Of Marine Programs Niskin bottles [ONLINE] Available at:http://www.coml.org/edu/tech/collect/niskin.htm [Accessed 28 March 2018]

[8] The Editors of Encyclopaedia Britannica Nansen bottle [ONLINE] Availableat: https://www.britannica.com/technology/Nansen-bottle#ref1068132 [Ac-cessed 28 March 2018]

[9] P. Quevauviller 1995 Quality Assurance in Environmental Monitoring VCH Ver-lagsgesellschaft mbH

[10] M. Dunbabin L. Marques 2012 Robots for Environmental Monitoring: Signifi-cant Advancements and Applications IEEE Robotics & Automation Magazine

[11] The Evolution of Drones [ONLINE] Available at:http://www.amaflightschool.org/DRONEHISTORY [Accessed 29 March2018]

[12] J-P. Ore, S. Elbaum, A. Burgin, C. Detweiler 2015 Autonomous Aerial WaterSampling Journal of Field Robotics

79

BIBLIOGRAPHY

[13] G. Di Stefano G. Romeo A. Mazzini A. Iarocci S. Hadi S. Pelphrey 2017 TheLusi drone: A multidisciplinary tool to access extreme environments Marine andPetroleum Geology

[14] L. Bird A. Sherman J. Ryan 2007 Development of an active, large volume, dis-crete seawater sampler for autonomous underwater vehicles Oceans ConferenceRecord

[15] J. T. Pennington M. Blum F. P. Chavez 2015 Seawater sampling by an au-tonomous underwater vehicle: “Gulper” sample validation for nitrate, chloro-phyll, phytoplankton, and primary production Association for the Sciences ofLimnology and Oceanography

[16] F. Fornai G. Ferri A. Manzi F. Ciuchi F. Bartaloni C Laschi C 2017 An Au-tonomous Water Monitoring and Sampling System for Small-Sized ASVs Journalof Oceanic Engineering

[17] M. Schwarzbach M. Laiacker M. Mulero-Pazmany K. Kondak 2014 Remotewater sampling using flying robots 2014 International Conference on UnmannedAircraft Systems, ICUAS 2014 - Conference Proceedings

[18] D. Balkingssoon Semi-Structured Interviews [ONLINE] Available at:http://designresearchtechniques.com/casestudies/semi-structured-interviews/[Accessed 13 March 2018]

[19] M. Kutz 2006 Mechanical Engineers’ Handbook Third Edition: Materials andMechanical Design John wiley & Sons, INC.

[20] TRIZ40 [ONLINE] Available at: http://www.triz40.com/TRIZ GB.php [Ac-cessed 2 May 2018]

[21] 2013 Working with Silnylon [ONLINE] Available at:http://specialtyoutdoors.com/working-with-silnylon/ [Accessed 22 May2018]

[22] M. Haward 2018 Plastic pollution of the world’s seas and oceans as a contem-porary challenge in ocean governance Nature Communications 9

[23] The Physics Factbook [ONLINE] Available at:https://hypertextbook.com/facts/2007/AllenMa.shtml [Accessed 20 August2018]

[24] General Magnaplate Corp Friction Calculator [ONLINE] Available at:http://www.frictioncalculator.com/ [Accessed 20 August 2018]

[25] Water - Density, Specific Weight and Thermal Expansion Coefficient[ONLINE] Available at: https://www.engineeringtoolbox.com/water-density-specific-weight-d 595.html [Accessed 28 June 2018]

80

Appendix A

Interviews with researchers

The appendix shows the raw interview data from the four interviews. The firstinterview was over telephone with Paul Eric Aspholm, research scientist situatedin Svanvik, Norway. The second interview was a personal meeting with GunhildRosqvist, professor in physical geography, and Pia Eriksson, research assistant,situated at Tarfala research station in Sweden. The third interview was a telephonewith postdoctoral researcher Erik Lundin situated in Abisko in Sweden. The fourthinterview was over e-mail with researcher and Ph.D student at Greenland Instituteof Natural Resources, Katrine Raundrup. The interviews were held in Swedishand Norwegian and translated into English by the interviewer. Words written inbrackets in the answers are comments from the interviewer.

81

APPENDIX A. INTERVIEWS WITH RESEARCHERS

Paul Eric Aspholm - telephone interview

1: How is the sampling procedure today?

− Big water sampler. Need 1 liter of water, but clean out laboratory bottle 2times with sample so take about 1.5-2 liter. Use boat in the summer and snowscooter in winter from nov-april. In winter, ice is 1 meter thick so need todrill a hole.

2: What do you use as vessel?

− KPT cylinder (can’t find online, must have heard wrong)

3: How is it working? Tell me about the user experience.

− Cylinder that is open in both ends (like Ruttner). Very heavy, weight 6-7kg.Made of lead to make it heavy and have a straight wire in stream water. It iseasy to use, cheap.

4: What can be improved? (Depth measurement, speed, air-tightness etc)

− Nansen/Niskin bottles are more advanced but they are bad when gettingsurface water.

5: What actions are you taking to avoid contamination?

− Clean laboratory bottle twice with water sample - need about 2 liter of samplefor this and gets 1 liter water sample.

6: What sampling sizes and depths are interesting in your research?

− 1 liter water sample (meaning 2 liters of water). Depths is 0-10 cm, 10-15 mand 34 m.

7: Do you take samples from the same position at several depths? (Throughoutthe water column)

− Yes.

8: Do you take/want to take samples from exactly the same place every time?(GPS coordinate)

− Yes, we use GPS coordinates.

9: What do you measure in the sample? What do you use the sample for? (pH,temperature, salt concentration, gases etc?)

− Temperature is measured instantly with thermometer. The sample is thensent to lab where those other things are measured.

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10: What would you like to measure in the sample? (Anything else than youmeasure now)

− Nothing. Follows the Water frame directivehttp : //ec.europa.eu/environment/water/waterframework/index en.htmland NVE https : //www.nve.no/.

11: How do you handle the sample when it’s taken?

− Keep at the same temperature as the sample temperature. Use refrigerator.In summer it can be 10-15 or even 20 degrees, needs to keep samples cold.Stays in refrigerator in 1-2 weeks until it is sent to lab analysis in Russia.

12: Is it important to keep sample as steady as possible to avoid to shake thesample?

− No but it is important that the container contains 100% water and no air.Also important to be able to replicate the sampling and that the wire is keptstraight if it is stream water. This is not a big issue in lakes.

13: What is the first step with the sample when going back to the station?

− Before station is to take temperature and keep cold. In station is to put inrefrigerator.

14: : How often do you take samples?

− Every month.

15: Do you have contact information to anyone else related to water samples?

− NVE and Fylkesmannen (Lansherren) for Finnmarkhttps : //www.fylkesmannen.no/F innmark/

Other comments:

− Drones needs to be able to fly far distances and carry payload. In Norway aspecific certificate is needed to fly big drones -¿ too time consuming, about 2years to get a license, not option when working in projects (ARO3 certificate?).Lockheed makes light weight drones. Airborne South Africa can handle coldtemperature, wet environment and big payload but are too big.

− Other more interesting technologies to implement with a drone are lidar - greenlaser - that can penetrate water to 10-15 m depth to see chlorophyll, planktonand silt. The combination of FLIR and lidar is also interesting. Multi spectralcamera can analyze the water quality, Algiers, plankton, temperature of thesurface and nutrients. Also using three different cameras for triangulation isinteresting to analyze the water. Much more interesting for us.

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Gunhild Rosqvist and Pia Eriksson - meeting at Stockholm Uni-versity


− Take boat into middle of lake and take the sample.


− Ruttner sampler, 200 ml at most

3: How is it working? Tell me about user experience.

−


− To take samples where we normally can’t take samples today. Get more accu-racy. Be able to change the volume of the vessel. It is windy an uncomfortable.It takes time, about half a day for 2 people.


− Sterilize the vessel before taking the sample.


− About 200 ml. The lake is 50 m deep so surface water, bottom water as itis poor of oxygen which makes it very interesting, and everything in betweenare interesting samples. We sample at the interval every second meter.

7: Do you take samples from the same position at several depths? (Throughoutthe water column)

− Yes.

8: Do you take/want to take samples from exactly the same place every time?(GPS coordinate)

− Yes, not very accurately but trying as much as possible.

9: What do you measure in the sample? What do you use the sample for? (pH,temperature, salt concentration, gases etc?)

− Temperature, pH, conductivity. Salt and DNA but that is hard to do withouta lab. Transect, measure occurrence of plankton. In lake inlet, outlet, un-derstand the dynamics in the water balance, oxygen and hydrogen, isotopes,evaporate.


84

− See answer 9.


− Don’t know.

12: Is it important to keep sample as steady as possible to avoid to shake thesample?

− No


−


− Some times every summer, when it is ice free July-Aug in Storsjon. Everyweek for the output of the lake including Dalmynningen.


− Abisko, Umea Uni, Niklas Rako. Also Erken, the lake in Norrtalje has waterlab. SITES network ecosystem science.

Other comments:

− Other applications are taking samples between ice sheets in the ocean or justmeasuring with sensors without taking the physical water sample.

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Erik Lundin - telephone interview


− Boat


− Ruttner


− Good.


− Using drones can save energy, time and therefore money. Problems withwater sampling: contamination, disturb the sample. Using a boat candisturb if you want to investigate free gases. Keeping a raft for envi-ronmental monitoring that is fixed in the water shadows the water andaffects the lake.


− Come to the lake with a clean bottle and then rinse it with lake water1-2 times. A big sample is also better than a small since the effect ofthe contamination is less the bigger sample. No exposure to sunlight.Prefer bottle that is covered but not too dark to keep the temperatureconstant. Use to tape bottles with reflection foil. Use polythen bottle.Sometimes use glass bottle. Some traces of Quicksilver can be found soTeflon surface is good. Good to have opportunity to buy different typesof bottles in future. Modular bottle can be good - would be good tochoose between 1 big sample or several smaller samples.


− 1 liter samples but you usually don’t use the full liter. Every analy-sis needs about 20 ml. Regarding depth, plus minus 2m (every 5 m).Interested in homogeneous water column.

7: Do you take samples from the same position at several depths? (Through-out the water column)

− Yes generally. In the summer it is warmer water at the surface thanat the bottom, so can be important to look at different water masses.Generally you want to take at 2-3 different depths.

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8: Do you take/want to take samples from exactly the same place everytime? (GPS coordinate)

−

9: What do you measure in the sample? What do you use the sample for?(pH, temperature, salt concentration, gases etc?)

− Water chemistry, DNA samples to freeze, filter water for plankton, CO2,temperature, conductivity.


− Pressure sensor would be good. Get a log file / meta file ”The samplewas taken at coordinate x y depth z time temperature”


− Transfer it to rinsed sample bottle.

12: Is it important to keep sample as steady as possible to avoid to shakethe sample?

− Doesn’t matter. Important is that it is no head space which means thesample bottle is completely filled with sample and no exchange of gas ishappening.


−


− 1 time every second week (physical water sampling) during summer andin winter time 1 time/month.


− I am from Polar Sekretariatet https://polar.se/ support research anddevelopment, I’m working more with chemical things, research etc andNiklas works with data logs and more technical things - would have otherinput then me.

Other comments:

87


− I work with environment supervision and sees relevance in drone tech-nology in Arctic environment and also in water sampling in general.About taking multiple samples: CTD robot on marine research shipshttp://www.vliz.be/en/ctd-en . Know researcher that uses helicopter tosample water from different lakes. Battery consumption when using sen-sors, oxygen sensors are easy and light weight, CO2 sensors can be foundat 9V but usually at 24V - which could be a problem when using a drone.Regarding several samples: Marine research vessels use CTD robot withdifferent sensors on (conductivity, pH, dissolved oxygen). Different ves-sels are attached with vacuum and when it reached its correct depth, oneof the vessels open up. Downside is that it gets turbulent when takingthe samples.

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Katrine Randrup - mail interview


− We collect water samples from two freshwater lakes ever 4 weeks duringthe ice-free season. One lake is ca. 50m above sea level while the other isca. 250m absl and they are ca. 3.5km apart. In each lake we have a fixedsampling point at the deepest point in the lake. We use a rubber dinghywith an outboard to reach the sampling station. We collect ca. 25 litersof water from 0.5m blow surface to 0.5 above bottom – depth integratedpooled water. At each of the sampling depths we record temperature.From the water sample we take subsample for phytoplankton studies, afiltered sample to zooplankton, a sample for water chemistry testing, asample for DOC (dissolved organic carbon), and a sample for chlorophylla measurement. Conductivity and pH is measured on the pooled watersample. Samples are analyzed in the lab when returning to the institute.


− We use a rubber dinghy with an outboard engine. For water sampling weuse a sampler similar to this one (http://www.kc-denmark.dk/products/water-sampler/limnos-water-sampler-2-l.aspx). Last summer we started usinga handheld CTD to get more precise information on temperature andconductivity in the water column.


−


−


− If the water sampler hits the bottom and sediment is upwelled a newsample from the bottom layer has to be taken. This has to be done in anearby spot or after waiting until the sediment has settled again. Othertypes of contamination is not relevant while out in the field.


− We need ca. 25l of water from the water column – in one lake the depthis ca. 35m while the other is ca. 27m

7: Do you take samples from the same position at several depths? (Through-out the water column)

89


− Yes

8: Do you take/want to take samples from exactly the same place everytime? (GPS coordinate)

− Yes

9: What do you measure in the sample? What do you use the sample for?(pH, temperature, salt concentration, gases etc?)

− Please see the answer to the first question.


− Ideally we would also like to measure different nutrients (Nitrogen andPhosphor) and dissolved oxygen

11: How do you handle the sample when it’s taken? (Put it in safe box orput directly in back pack etc).

− The different samples (please see answer to the first question) are handleddifferently. Samples for phyto- and zooplankton are stored in brown bot-tles with a little lugol for preservation. The other samples are wrappedin tinfoil to keep out of sunlight and to keep relatively cold.

12: Is it important to keep sample as steady as possible to avoid to shakethe sample?

− No


− We measure pH and conductivity at the field station. Other measure-ments/analyses are done at the institute – preparation and/or analysismust be done or started at the same day as sampling.


− Approximately every 4 weeks


− I have forwarded your mail to relevant colleagues at the institute andexternal as well. I hope some have replied directly to you.

90

Appendix B

Survey report

The data from the survey is reported below.

Figure B.1. Graphs showing profession, years experience and current task.

91

APPENDIX B. SURVEY REPORT

Figure B.2. Graphs showing water volume and frequency of water samples.

Figure B.3. Graph and tables showing sampler models and their pros and cons.

92

Figure B.4. Graphs showing time and how many people sampling takes.

Figure B.5. Graphs showing max. depth and depth interval of sampling.

93


Figure B.6. Graph showing measured data.

94

Figure B.7. Graphs showing desired data and accuracy of temp.

95


Figure B.8. Graph showing importance of characteristics of sampler.

96

Figure B.9. Graph showing importance of characteristics with average value.

97


Figure B.10. Graph showing actions to avoid contamination.

98

Figure B.11. Graph showing reasonable pricing of sampler.

99


Figure B.12. Tables showing challenges and risks of sampling.

100

Figure B.13. Graphs showing current material and desired material of sampler.

Figure B.14. Graph showing reactions on proposed idea with integrated laboratorybottle.

101

Appendix C

Requirement specification

Functional requirements

1. The water sampler shall be able to collect samples remotely.

2. The full test system shall be able to gather water samples at the desireddepth automatically.

3. The equipment shall remain its functionality after being dropped from aheight of 2 m.

4. The equipment shall remain its functionality after being dragged on theground 5 m.

5. The water sampler shall protect internal electronics from water damage.

6. The water sampler shall be able to take samples from different depths.

7. The water sampler shall be able to take water samples that are at least10 m deep.

8. The construction shall contain a release mechanism to protect the drone.

9. The parts of the water sampler in contact with lake water shall notcontain metal.

10. WISH: The water sampling equipment can be modular.

11. The water sampling construction shall not increase contamination com-pared to the manual sampling method.

12. The gathered water sample volume shall completely fill the laboratorybottle (no headspace).

13. Electronics shall be protected from water.

103

APPENDIX C. REQUIREMENT SPECIFICATION

Non-functional requirements

1. The weight of the water sampling construction, including water sample,shall be below or equal to 1 kg.

2. The water sample volume to be collected by the water sampler shall beminimum 500 ml.

3. Based on requirement [1] and [2], the empty sampling equipment shallweight less than 0.5 kg.

4. The full test system shall be able to gather water samples at a depth of10 meters.

5. The accuracy of the depth measurement shall be ±0.25m.

6. The water sampler shall be able to measure temperature within the range0-20◦C.

7. The accuracy of the temperature measurement shall be ±0.1◦C.

8. The drone shall keep a safety distance of at least 2 meters above thewater surface.

104

Appendix D

Criterion for concept evaluation

Table D.1. Criterion for concept evaluation

Characteristics 1 5Easy to use Hard to learn how to use the

productEasy to learn how to use theproduct

Very labor extensive Automated functionalityHard to use when perform-ing analyses in laboratory

Easy to use when perform-ing analyses in laboratory

Long durability Low quality product High quality productNot made for long time use Made for long time use

Fast sampling Takes more than 3 h to takesamples

Takes less than 3 h to takesamples

No ability to take severalsamples through out watercolumn

Ability to take several sam-ples through out water col-umn

Low sinking velocity of sam-pler

High sinking velocity ofsampler

Need to merge several sam-ples to get needed volume

No need to merge severalsamples to get needed vol-ume

High accuracyof sensor data

No interface for sensors in-stalled

Interface for sensors in-stalled

High accuracyof depth mea-surement

Not able to measure depth Able to measure depth

No interface for depth mea-suring installed

Interface for depth measur-ing installed

Continued on next page

105

APPENDIX D. CRITERION FOR CONCEPT EVALUATION

Table D.1 – Continued from previous pageCharacteristics 1 5

Accuracy of depth measure-ment > ±0.5m

Accuracy of depth measure-ment < ±0.5m

Measure tem-perature

Not able to measure tem-perature

Able to measure tempera-ture throughout water col-umn

No interface for tempera-ture measuring installed

Interface for temperaturemeasuring installed

No accuracy of temperaturemeasurement

High accuracy of tem-perature measurement(< 0.1◦C)

Take sampleson differentdepths

Not able to take samples ondifferent depths

Able to take samples fromdifferent depths

Mark-wire-method fromdistance

Communication from sam-pler in water

Take big watersample volumes

One size only Sampler available at differ-ent sizes

Low price Less than 5000 SEK More than 5000 SEKLow weight High weight per water vol-

ume unitLow weight per water vol-ume unit

Remote Can not be carried by hu-man

Can be carried by drone

Needs human assistance tofunction

Full remote function

Reliability Need to retake sample everytime

Never need to retake sample

High risk of taking wrongsample

Low risk of taking wrongsample

High risk of contaminatedsample

Low risk of contaminatedsample

The following motivations from Erik Lundin were written in Swedish andtranslated into English.

• Easy to use, 3-4: Everyone understands the principle after using it for 5minutes, but it takes a couple of attempts to get the pace up.

106

• Long durability, Summer time 5, Winter time 1-2: In winter time, themoving parts freeze and you can often only take 1 sample before theentire equipment froze completely.

• Fast sampling, 1-2: to sample with a Ruttner is rather time consuming

• High accuracy of sensor data: Usually, no extra sensors are used butthey could possibly be added.

• High accuracy of depth measurement, 2-3: the precision gets worse withthe depth as the sampler can move with streams etc.

• Able to measure temperature, 2: it is possible, but a thermometer mustbe installed, and it is only the temperature of the gathered water samplethat gets measured.

• Able to take samples on different depths, 3-4: it is the purpose of theRuttner sampler.

• Able to take big water sample volumes, 4: I have seen Ruttner samplersfor sample volumes up to 10 liters, so the size is not really limited.

• Low price, 3: it costs 500-2000 Euro, which is considered a low pricein the context. Low weight, 4: Everything is relative, but the Ruttnersampler it self weights less than carrying the water sample back to thestation.

• Level of remoteness, 2-3: compared to other equipment that we use, thatis too heavy to even carry without having extra aid/tools.

107

Appendix E

Code

The code below is a test code for verifying that the servo rotates when thepressure sensor is within ± 1 cm of the inputted depth. The current waterpressure and temperature is continuously printed. The outcome of the test ispositive.

/∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗SparkFun MS5803 Demo.inoDemo Program for MS5803 pressure sensors.Casey Kuhns @ SparkFun Electronics7/20/2014https://github.com/sparkfun/MS5803−14BA Breakout/

The MS58XX MS57XX and MS56XX by Measurement Specialties is a lowcost I2C pressure

sensor. This sensor can be used in weather stations and for altitudeestimations. It can also be used underwater for water depth measurements.

Resources:This library uses the Arduino Wire.h to complete I2C transactions.

Development environment specifics:IDE: Arduino 1.0.5Hardware Platform: Arduino Pro 3.3V/8MHzT5403 Breakout Version: 1.0

∗∗Updated for Arduino 1.6.4 5/2015∗∗

This code is beerware. If you see me (or any other SparkFun employee) atthe

109

APPENDIX E. CODE

local pub, and you’ve found our code helpful, please buy us a round!

Distributed as−is; no warranty is given.∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗

∗/

#include <Servo.h>#include <Wire.h>#include <SparkFun MS5803 I2C.h>

// Begin class with selected address// available addresses ( selected by jumper on board)// default is ADDRESS HIGH

// ADDRESS HIGH = 0x76// ADDRESS LOW = 0x77

MS5803 sensor(ADDRESS HIGH);

//Create variables to store resultsfloat temperature c, temperature f;double pressure abs, pressure relative , altitude delta , pressure baseline ,

pressure 2 , water sample depth;Servo myservo; // create servo object to control a servoint pos = 0; // variable to store the servo position

// Create Variable to store altitude in (m) for calculations ;//double base altitude = 1655.0; // Altitude of SparkFun’s HQ in Boulder,

CO. in (m)

void setup() {Serial .begin(9600);//Retrieve calibration constants for conversion math.sensor. reset () ;sensor.begin();pressure baseline = sensor.getPressure(ADC 4096);water sample depth = 10.00; //cm, input desired depth

myservo.attach(9); // attaches the servo on pin 9 to the servo objectSerial .begin(9600);

}

110

void loop() {//Serial . println(water sample depth+1);//Serial . println(water sample depth−1);if ((pressure 2 < water sample depth+1) && (pressure 2 >

water sample depth−1)){

//Turn servoSerial . print(”Verfiying pressure = ”);Serial . println(pressure 2) ;for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180

degrees// in steps of 1 degreemyservo.write(pos); // tell servo to go to position in

variable ’pos’delay(15); // waits 15ms for the servo to

reach the position}}

// To measure to higher degrees of precision use the following sensorsettings :

// ADC 256// ADC 512// ADC 1024// ADC 2048// ADC 4096

// Read temperature from the sensor in deg C. This operation takesabout

temperature c = sensor.getTemperature(CELSIUS, ADC 512);

// Read temperature from the sensor in deg F. Converting// to Fahrenheit is not internal to the sensor.// Additional math is done to convert a Celsius reading.

// temperature f = sensor.getTemperature(FAHRENHEIT, ADC 512);

// Read pressure from the sensor in mbar.pressure abs = sensor.getPressure(ADC 4096);pressure 2 = pressure abs−pressure baseline;// Let’s do something interesting with our data.

111

APPENDIX E. CODE

// Convert abs pressure with the help of altitude into relative pressure// This is used in Weather stations.// pressure relative = sealevel(pressure abs, base altitude ) ;

// Taking our baseline pressure at the beginning we can find anapproximate

// change in altitude based on the differences in pressure.altitude delta = altitude(pressure abs , pressure baseline ) ;

/∗// Report values via UARTSerial . print(”S pressure = ”);Serial . println( pressure baseline ) ;

Serial . print(”Temperature C = ”);Serial . println(temperature c);

/∗Serial . print(”Temperature F = ”);Serial . println(temperature f);∗/

/∗Serial . print(”Current pressure (mbar)= ”);Serial . println(pressure 2) ;

/∗Serial . print(”Pressure relative (mbar)= ”);Serial . println( pressure relative ) ; ∗//∗Serial . print(”Altitude change (m) = ”);Serial . println( altitude delta ) ;Serial . print(” ”) ;∗/

delay(1000);

}

// Thanks to Mike Grusin for letting me borrow the functions below from// the BMP180 example code.

/∗ double sealevel (double P, double A)// Given a pressure P (mbar) taken at a specific altitude (meters),// return the equivalent pressure (mbar) at sea level .

112

// This produces pressure readings that can be used for weathermeasurements.

{return(P/pow(1−(A/44330.0),5.255));

}∗/

double altitude(double P, double P0)// Given a pressure measurement P (mbar) and the pressure at a baseline

P0 (mbar),// return altitude (meters) above baseline.{

return(44330.0∗(1−pow(P/P0,1/5.255)));}

113

TRITA TRITA-ITM-EX 2018:706

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