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ROBOTIC BOAT
PRESENTER: JACLYN TARNAI, GRAHAM WILLIAMSON , DAVID WONG, YIRAN ZHOU
PRESENTATION FORMAT
1. Introduction and Background
2. Identify Needs and Set Specifications
3. Generate, Evaluate and Select Concept
4. Critical Function Prototype
5. Design in Detail
6. Validation of Design
7. Construction Process
8. Final Prototype Testing
9. Final Specifications and Recommendations
INTRODUCTION AND
BACKGROUND
ABOUT UBC
University located in
British Columbia (45
mins away)
Consistently ranked
among the 40 best
universities in the
world
ABOUT THE CAPSTONE COURSE
A 2-term, 6 credit course
for mechanical engineering
students in their senior
year
Required for graduation
Problems are proposed by
industry clients, and
students design a solution
BACKGROUND OF THE PROJECT
• Stratus Aeronautics designs UAVs
for aerial mapping applications
• Geophysical mapping (local
magnetic field)
• Light Detection And Ranging
terrain mapping
• Would like to enhance existing
mapping solution with bathymetry
PRIMARY FUNCTION
Bathymetry survey
Example of Bathymetry Survey Post Analysis
Note: Alberto Romani and Pierluigi Duranti(2012), "Autonomous Unmanned Surface Vessels for Hydrographic Measurement and
Environmental Monitoring"
DATA COLLECTION PROCESS
Example of a Mow the Lawn Path
Note: Christopher Kitts, Paul Mahacek, Thomas Adamek, Ketan Rasal, Vincent Howard, Steve Li, Alexi Badaoui, William Kirkwood, Geoffrey
Wheat and Sam Hulme (2012), "Field operation of a robotic small waterplane area twin hull boat for shallow-water bathymetric
characterization”
BENCHMARKING OF EXISTING ALTERNATIVES
YSI EcoMapper (AUV) Kingfisher USV by Clearpath Robotics
Long operating time (8-14 hrs)
Can be carried (45kg)
Expensive ($50,000)
Small measuring depth (100m)
Can fit in helicopter/truck
Easily carried (28kg)
Expensive ($50,000)
Low operating time (2.5 hrs)
IDENTIFY NEEDS AND SET
SPECIFICATIONS
PRIMARY REQUIREMENTS
FUNCTION DECOMPOSITION
Determinative functions:
1. Maintain device on top of water
2. Increase speed of device relative to water
3. Change orientation of device relative to water
4. Prepare device for transport
5. Decrease speed of device relative to water
6. Support components relative to device
7. Identify position of device relative to surrounding
8. Send and receive data from device to shore
9. Protect electronics from water contact
Non-determinative functions:
Store power in device
Modify power stored in device
Display information to user
Receive control parameters from user to device
Generate route device’s current position to destination position
Notify user of device’s hazardous situation
Monitor device’s status
Correct device’s current position relative to desired position
Return device to “home” position
Store “home” position in device
Store sensor data in device
GENERATE, EVALUATE, AND SELECT
CONCEPTS
EVALUATION PROCESS
Winnowing
Needs and Requirements (Thresholds)
Feasibility
Technical Readiness
Ranking(Pugh Chart)
Scoring
Weighted Decision Matrix (with AHP weightings )
Value Equations
WINNOWING
F1 Maintain device on top of water
• Dual outrigger floats
• Tupperware boat
• Partially inflated hull
• Catamaran
• Hovercraft
• Semi-submersible
• Inflatable float
• Single hull
• Raft
• Hydrofoils
• AUV
F2 Increase speed of device relative to
water
• Thruster(s)
• Impeller water jet
• Ducted fan
• Shafted propeller through hull
• Water wheels
• Air propeller
• Variable pitch propeller
• Sail
F3 Change orientation of
device relative to water
• Rudder
• Variable direction propulsion
• Differential propulsion
• Lateral propulsion
• Air rudder
• Shifting CG
F4 Prepare device for transport
• Folding floatation device
• Removable parts
• Pivoting floatation device on rail tracks
• Sliding with positioning
• Partially hollow floatation device
F5 Decrease speed of device relative to
water
• Regular drag
• Reverse propulsion
• Air brakes
• Water brakes
• Rudder braking
WINNOWING
F6 Support components relative to device
• Enclosure attachment
• Components inside floatation device
• Tow
• Bonded to vibration absorber
• Fixed to suspension platform
• Bonded to floatation device
• Suspended in air
• Suspended between hull(s)
F7 Identify position of device relative to
surrounding
• GPS
• Home reference (DGPS)
• Transmission latency
• Compass + math model
• Sonar sensor(s)
• Camera
• Wire/cord
• Signal tracking
• Flare tracking
• Drone
• Visually tracked from shore (laser)
• Inertia sensor
F8 Send and receive data from device to shore
• Antenna tower
• Omnidirectional antenna
• Balloon antenna
• Relay
• Transmit to third party
• Wired (no transmitting)
• Laser
• Sound transmission
• Wi-Fi
F9 Protect electronics from water contact
• Waterproof enclosure
• Waterproof spray
• Umbrella
SCREENING
(PUGH CHART)
CRITERIA
Concept
#1
Concept
#2
Concept
#3
Concept
#4
Concept
#5 Example Justifications
Concept
#6
Concept
#7
Concept
#8
Cost 0 -1 -1 1 0 -1 -1 -1
Transport-
ation Size 0 -1 1 -1 1
Inflated hull significantly shortens
the length of boat and allows
folding -1 0 -1
Endurance 0 -1 -1 0 -1
Inflated hull creates additional
water resistance compared to
streamlined hull 0 -1 -1
Robustness 0 -1 0 1 -1
Partially inflated hull may need
more maintenance than rigid hull 0 1 0
Weight 0 1 -1 -1 1
Weight of hull and simpler
shafted propellor are lighter 0 -1 -1
Controll-
ability 0 1 -1 0 -1
inflated hull lowers the
predictive behavior of device -1 1 -1
sum 1's 0 2 1 2 2 0 2 0
sum -1's 0 4 4 2 3 3 3 5
sum 0's 6 0 1 2 1 3 1 1
overall rating 0 -2 -3 0 -1 -3 -1 -5
rank 1 5 6 1 3 6 3 8
CONCEPT #1
Tupperware Boat -Thrusters - Rudder - Folding - Reverse Propulsion - Mechanical Attachment
- DGPS - Antenna Tower - Waterproof Enclosure
CONCEPT #4
Catamaran Dual Outrigger Float - Thrusters - Rudder - Removable - Regular Drag -
Mechanical Attachment - GPS - Antenna Tower - Waterproof Enclosure
CONCEPT #5
Catamaran Partially Inflated Hull - Shafted Propeller - Rudder - Folding - Rudder Braking -
Vibration Absorber - DGPS - Omnidirectional Antenna - Waterproof Enclosure
Folding hinge
Cross section
CONCEPT #7
Semi-submersible (catamaran style) - Impeller Waterjet - Differential Thrust - Sliding with
Positioning - Regular Drag - Fixed to Suspension Platform - GPS - Antenna Tower -Waterproof
Enclosure
EVALUATION STRATEGY
Weight
6%Transportation size
9%
Endurance
15%
Controllability
16%
Robustness
17%
Cost
37%
0
50
100
0 500 1000 1500
Sat
isfa
ctio
n (%
)
Cost ($)
Customer Satisfaction % vs Cost of Robotic Boat
CRITICAL FUNCTION PROTOTYPING
CRITICAL FUNCTION
FUNCTION: Correct device's current position relative to desired position.
Will the Pixhawk autopilot be able to correct the devices position accurately after a
disturbance?
Actual Path
Disturbance
Desired Path
Acce
pta
ble
devia
tion
Image from https://www.youtube.com/watch?v=4Y7zG48uHRo
RATIONAL FOR CFP
Three main categories in the project:
Mechanical Design: Well-developed with existing solutions
Data Collection: Scope is limited to researching, selecting, and integrating sensor
Autonomous Navigation System: Integration is complex
Autopilot importance:
Most complex feature
Significant project cost and lead time
Lack of team familiarity
WHICH CONCEPT WILL BE TESTED ?
Tupperware boat
Thruster(s)
Rudder(s)
Regular Drag
WHAT WAS USED FOR TESTING?
Pixhawk Autopilot
Autopilot suggested by client
GPS ublox LEA-6 w/compass
Provided for Testing
More accurate Swift or Novatel GPS for project
Image from http://www.robotshop.com/ca/en/3dr-px4-pixhawk-advanced-autopilot.html
http://www.robotshop.com/ca/en/3dr-gps-module-ublox-lea-6-compass.html
EXECUTION OF CRITICAL FUNCTION PROTOTYPE
MAPPING OF FEATURES OF CFP TO
VERIFICATION CRITERIA
Hovercraft CFP Features
Rudder system
Throttle controlled thruster
Operating in fluid
GPS waypoint navigation
CFP BUILD QUALITY
Cost (“small expenditure” = $30)
Limited time & budget available
Material used
Material available at-hand
Robust
Used for 2 days w/o significant wear
Consistent performance
Re-usable for further testing
PID tuning and path testing
Electrical connections must be
temporary
TYPICAL SCENARIO
Positional Shift of the boat
Ref: http://ngm.nationalgeographic.com/u/TvyamNb-
BivtNwcoxtkc5xGBuGkIMh_nj4UJHQKuorle-82rIjPED3j1K-
sgp7vZ4QwrDy0gkuBKjQ/
Angular Shift of the boat
Top View:
Top View:
ASSUMPTION FOR SCENARIO
Positional Shift of Hovercraft
Angular Shift of Hovercraft
6ft
3ft
-3ft
ASSUMPTIONS
Behavior of the hovercraft is comparable to a boat
Autopilot behavior using current GPS is comparable to a more accurate GPS
PID for hovercraft is not usable as PID for boat
More time will be spent to tune PID for boat
LIMITATIONS
Hovercraft is a different system
Less friction from air therefore less damping
More prone to skidding/drifting
Smaller scale
PID control is not perfectly tuned
Testing conditions
Minor slopes/debris on ground
Accurate GPS for final prototype is not available during CFP stage
- Slight drifting of GPS is expected
RESULTS
-4
-3
-2
-1
0
1
2
3
4
-5 0 5 10 15 20 25
Devi
atio
n (
m)
Distance from starting point (m)
Deviation of various offsets
Control
-3 ft position offset
-6 ft position offset
3 ft position offset
15 deg offset
30 deg offset
45 deg offset
60 deg offset
RESULTS
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20 25
Devi
atio
n (
m)
Distance from starting point (m)
Deviation of various offsets with drift corrected
Control
-3 ft position offset
-6 ft position offset
3 ft position offset
15 deg offset
30 deg offset
45 deg offset
60 deg offset
CONCLUSION OF RESULTS
Met verification criteria within limitations
30 deg. & -6ft results were influenced by testing environment
Pixhawk autopilot is suitable
Responsiveness can be improved with further PID tuning
Drift shows that improved accuracy of DGPS is worthwhile
RESULTS/LESSONS LEARNED
Result
Autopilot will work for the final prototype
Lessons Learned
PID controller tuning
Start with suggested PID control parameters for boats
Autopilot has not been used extensively with hovercraft
Procedure to analyze GPS data
DESIGN IN DETAILDESIGNING THE HULL
CALCULATION PARAMETERS
EXAMPLE CALCULATIONS
HULL OPTIMIZATION
Plotted various parameters as a function of hull length and hull width
Draught
Drag force
Max speed
Stability
Endurance
Final dimensions:
Length – 2m
Width – 18cm
Draught – 9.4cm
Center-to-center distance of hulls – 1m
612
1824
3036
4248
5460
0
1
2
3
4
5
6
7
8
9
1 1.2 1.4 1.6 1.8 2 2.2
HU
LL W
IDT
H (C
M)
MA
X S
PEED
(K
M/H
)
HULL LENGTH (M)
MAX SPEED
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9
STABILITY CALCULATIONS
𝐼𝑇𝑟𝑎𝑛𝑠𝑣𝑒𝑟𝑠𝑒 = 2 ∗ (𝐿𝑒𝑛𝑔𝑡ℎ ∗𝑊𝑖𝑑𝑡ℎ3
12+ 𝐴 ∗ 𝑑2)
𝐵𝑀 =𝐼𝑇𝑟𝑎𝑛𝑠𝑣𝑒𝑟𝑠𝑒
𝑊𝑒𝑖𝑔ℎ𝑡
KG = Draught
KB = Draught / 2
𝐺𝑀 = 𝐵𝑀 + 𝐾𝐵 − 𝐾𝐺 = 1.8𝑚
Longitudinal Static StabilityTransverse Static Stability
𝐼𝐿𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑖𝑛𝑎𝑙 = 2 ∗ (𝑊𝑖𝑑𝑡ℎ∗𝐿𝑒𝑛𝑔𝑡ℎ3
12+ 𝐴 ∗ 𝑑2)
𝐵𝑀 =𝐼𝐿𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑖𝑛𝑎𝑙
𝑊𝑒𝑖𝑔ℎ𝑡KG = DraughtKB = Draught / 2
𝐺𝑀𝐿𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑖𝑛𝑎𝑙 = 𝐵𝑀 + 𝐾𝐵 − 𝐾𝐺 = 3.04𝑚
HULL DESIGN
Recommendation from Client
– simple hull to limit manufacturing time
Approx. Length = 2m
Polystyrene and Fiberglass Hull
Construction
STRESS CALCULATIONS
CALCULATED PERFORMANCE
Assumptions
Weight = 45.04kg
Drag Coefficient = 1.2
Batteries: 1x90Ah at 12V
Overhead Power Loss=50W
Performance
Dimensions of device below surface:
approx. 2m x 18cm x 8.5cm per hull,
center-to-center spacing =1m
Max. speed: 6.6 km/hr (3.56 Knots)
Battery life: 3.2 hr
VALIDATION AND VERIFICATION
¼ SCALE MODEL VERIFICATION
Tested at scale speed:
0.83m/s, survey speed
1.25m/s, mid speed
1.67m/s, top speed
Tested with:
1/4 scale sensor
Sensor fairing
Reduced weight
FLUME TESTING
Scale Model
DAQ System
Pulley
Tank
FLUME TESTING
Include Video/GIF
RESULTS
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Dra
g Fo
rce (
N)
Scale Speed (m/s)
Model Drag Force
No Load
Sensor
Fairing
Light Model
RESULTS
Average Drag CoefficientNo Load 0.719Sensor 0.603Fairing 0.324Light Model (-14.3%) 0.335
MAPPING TO EVALUATION CRITERIA
Cost
24%
Manufacturability
22%
Robustness
8%
Weight
2%
Endurance
6%
Controllability
9%
Stability
29%
APPROPRIATENESS OF EVALUATION CRITERIA
Manufacturability and cost reflects the design of the boat hulls
Hand calculations were done for speed, endurance, stability, and robustness
The hand calculation results show that the design was barely meeting the minimum requirements for
speed and endurance, so a physical scale testing needs to be done
As well, the sonar may pose significant drag force due to its geometry, so a comparison
between the sensor and sensor with fairing was needed.
DESIGN FEATURES MAPPED TO EVALUATION CRITERIA
• Cost(24%)
• $193.03 for hulls
• Manufacturability(22%)
• Straight edges, no curves
• Stability(29%)
• Catamaran design(horizontal)
• Maximized water-plane
area(longitudinal)
• Lowered CG with batteries
stored in hull
CONCLUSION
Our hand calculations are valid
Further improvements to design:
Decrease weight
Swap lead-acid battery for lighter alternative
Round off edges
CONSTRUCTION PROCESS
CONSTRUCTION PROCESS
Template for hull shape
Template for front hull shape
CONSTRUCTION PROCESS
Layout of foam layouts
Hot wire cutting for hull shape& battery compartment
CONSTRUCTION PROCESS
Plywood hard points for attaching fasteners onto hull
Made into shape for battery hatches
CONSTRUCTION PROCESS
Fiberglass layer on top of foams (fiber, epoxy, paint)
Reapplication of epoxy at corners
CONSTRUCTION PROCESS
Handles for carrying
CONSTRUCTION PROCESS
Two 2” x 2” x 1.32m horizontal struts for connecting hulls
Two 1” x 1” vertical struts for motor mounts
CONSTRUCTION PROCESS
Mounting L brackets for motor
Waterjet cut from aluminum sheet
CONSTRUCTION PROCESS
Fabrication of power system
Glands and gaskets used for waterproofing
CONSTRUCTION PROCESS
Fabrication of Pelican case, Power electronics,
signal processing and telemetry
CONSTRUCTION PROCESS
Mounting brackets for pelican case
Connection of power and signal to rudder & thrusters
FINAL PROTOTYPE TESTING
FINAL PROTOTYPE TESTING
Location: UBC Fountain
Verified stability at 7s oscillation from impulse
Verified water line at 46kg weight
Verified maneuverability requiring < 10 lbf to turn boat
FINAL PROTOTYPE TESTING
Location: Alta Lake, Whistler
Validated onsite assembly and transportation
Verified Maximum speed (7.9kph)
Less than desired, space to improve
Verified Turning Radius (1.73m)
Lessons Learned:
Need improvements on compass interference
Need improvements on control thresholds
FINAL PROTOTYPE TESTING
Location: Como Lake, Coquitlam
Successful collection of sonar data
Further PID tuning required to follow
generated path
TESTING VIDEO
FINAL SPECIFICATIONS AND
RECOMMENDATIONS
FINAL SPECIFICATIONS
Maximum Speed : 2.2 m/s (7.9kph)
Turning Radius: 1.73m
Survey Depth: 150m
Weight: 44.4 kg
Dimension: 2000mm (L) x 1180(W) x 1450 (H)
Hull Dimension: 2000mm (L) x 180mm (W) x 300mm (H)
Draught (waterline): 94mm
Material: Polystyrene Foam, Fiberglass, Plywood, Aluminum 6068 T6, Stainless
Steel 316, Polypropylene and Mild Steel
Battery Capacity: 5s x 60Ah for Boat (LiFe) & 2 x 4s x 3Ah for Sensor (LiPo)
Operation Time: 10.7h (Boat) & 2h (Sensor)
REPLACE STIFF ELECTRICAL WIRE
Stiff Wire Flexible Wire
CONTINUE TUNING AUTOPILOT
REDUCE BOAT WEIGHT
Final weight: 44.4kg
Max weight: 46.0kg
Platform weight: 7.9kg
OPERATE USING 6 BATTERIES INSTEAD OF 5
Battery Specifications
60Ah capacity
Min: 2.5V, Nom: 3.2V, Max: 3.65V
Thruster max: 6-20V
> 16V – performance unknown
15V – 21.9V range
< 20V = <3.33V per battery
LOWER THRUSTERS DEEPER INTO WATER
Observed water splashing
Improve efficiency
ADD TELEMETRY CONNECTION TO NUC
Pelican Case with NUC GPS and Heave Data for NUC
INCREASE SENSOR BATTERY CAPACITY
Current capacity: 2 x 4S LiPo
3Ah each = 6Ah total
Operating time = 2hr
REPLACE 3D PRINTED RUDDER
3D Printed Design Final 3D Printed Part
REPLACE ALL NON-STAINLESS FASTENERS
Some steel bolts and screws were included
Due to time constraints
Replace with 18-8 stainless steel equivalent
REPLACE GLANDS WITH CONNECTORS
Waterproof Cable Glands Military Grade Connectors
QUESTIONS?
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