Week 6 - Assessment and Design

7/29/2019 Week 6 - Assessment and Design

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Assessment and Design

Anthropometry

Physiology of WorkErgonomic/Anthropometric Assessment

Design of Work


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Anthropometry

The science of measurement and the art of

application that establishes the physical

geometry, mass properties, and strength

capabilities of the human body (Roebuck,1993)

Anthropos = human

metricos = measurement

Uses/applications for measurement Design, criminology, medical practice, personnel

selection


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What defines the human being

anthropometrically?

Physical Measurements Wide range of sizes

Proportions of various body dimensions

Mobility

Strengths

Human Sensing and Performance Capabilities

Physiology

Psychology of Comfort and Perception

e.g., three dimensional spatial locations of the eyes so as

to determine what can be seen and thereby identify

obstructions that limit vision and cause error


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Anthropometry helps to

Evaluate postures and distances to reach controls

Specify clearances separating the body from hazards such as

surrounding equipment Identify objects or elements that constrict movement

Assess the biomechanical forces and torques during manualmaterial handling , operator fit in vehicles, accommodationcomfort, and general human performance

Assist in the design of tools to be grasped and handles thatcan be grasped or readily operated

Help clothing designers develop better fitting garments andmake it easier for clothing buyers and military quartermastersto know how many of what sizes to procure

Provide numerical data permitting a persons body dimensions

to seat heights, breadths, depths, and support angles (studieshave shown that ranges of these values correlate closely withcomfort/discomfort according to the activity performed in theseat.


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History of Anthropometry

An outgrowth of physical anthropology Developed 200 years ago to distinguish among the races and

ethnic groups of humans, identify criminals, and aid in

medical diagnosis

More recently used in developing engineering design

requirements and evaluation of modern vehicles, work sites,

equipment, and clothing (Roebuck, Kroemer, and Thompson,

1975), evaluations of cockpits and clothing were strongly

supported and determined by military needs during and

following World War II (Hertzberg, 1955) Many modern applications are to commercial and civilian

equipment, vehicles, and clothing (CAD Modelling, 1992;

Czaja, 1984; Roe, 1992; Sanders and Shaw, 1985).


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History of Anthropometry

Anthropometric studies are fairly infrequent and lack theprominence in academic anthropology tend to be more

technical papers

Considered a developing science where certain aspects of

he subject matter of anthropometry qualify it as an historical

science (anthropometric surveys are in many ways historicalevents and can never be repeated in exactly the same way,

even on the same people due to developmental changes.

Consequently, populations are frequently identified by year of

measurement, by occupation, and by ethnic group.

Body dimension surveys serve as benchmarks against which

new survey data can be compared and can be used to trace

and predict the microevolution of human groups.


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Electronic Modeling and New Measurement Technologies

Technological innovations are changing the use of

anthropometry in engineering applications Computer modeling of people as substitutes for living humans in

computer-aided design (CAD) for human factors applications

Use of new electronic imaging methods for measurement

3-D visualization and statistical manipulation of body sizes andshapes

Widespread attempts to develop graphical computer models ofthe human body forms and functions

Becoming a new design approach called concurrent design orsimultaneous engineering (Boyle, Ianni, Easterly, Harper, andKorna, 1991; Majoros, 1990; Roebuck, 1991) Major goal is to complete engineering analyses before spending a

large percentage of the project funds on construction of physicalmockups, prototypes, or products (e.g., Boeing 777 and 787)

Ergonomics today cannot rely as heavily on the responses and fit ofliving subjects in mockups

Leading to models of human responses and size variations intoelectronic models of humans


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Electronic measurement and modeling

Focusing attention on past and current

deficiencies of anthropometric data gathering,reporting and application methods

Creating new demands for more comprehensive,

integrated data

3-D measurements of body surface contours andlandmarks

Location of internal joint centers of rotation

Determination of interjoint link lengths and orientations

Need for data on the effects of changes in orientation,pressures on external surfaces on body flesh,

environmental effects, clothing shape, and new

concepts for body support


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Computer Modeling Historically, it has been common to have different sets of data

and models for each application area (e.g., work space or

clothing) Developments in computer models and data-handling

technologies offers new opportunities for using large, centralmathematical databases and more integrated, comprehensiverepresentations of the human form

Potentially useful for design of clothing, work space, tools, andequipment

Frequently require more data than available from most surveys

Data need to be in three dimensions and to describe ranges ofmovement for joints

When a great deal of contour data are known (up to 5000 points),

it has generally not been at the key cross-sections desired(passing through joints or a specified percentages of distancebetween joints) or related to internal links and joint centers

Lack of data and large individual differences result in contourdata cannot be readily analyzed using conventional statistics


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New Approaches

Development of typical sets of equations thatdescribe general form functions common to manydifferent people

Standard sets of internal coordinate systems relatedto joint centers and vectors connecting them

Modelers hope to more completely specify bodyshape, size, and postures without incurringexcessive cost to gather, analyze, and publish data

Potential to improve our understanding how thegeometry of human bodies may be defined in termsof statistical variables and functional mechanisms


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Benefits

Computer modeling offer enhancements to:

Sports performance

Design of personal protective gear

Design of clothing

Design of medical prostheses and medical

equipment

Design of tools and assembly jigs Design of vehicle interiors


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Measurement Technology

Started as simple body measurements

Standardization required focus on body landmarks

Usefulness required understanding of joint movements,associated torques and stresses

New measurement techniques include use of lasers, stereo

video, structured light, flying-spot light beam, magneticresonance imaging (MRI), computer aided tomography (CAT)scanning, special X-ray methods, ultrasonic visualization, sonicdigitization, movement measurement methods

Most new methods couple computers to sensors in ways thatproduce digitized data, points, and pixels located in three-

dimensional space. Significantly more data than single or twodimension methods.

New measurement capabilities complement new data needs butpose problems for comparing/understanding data produced byolder, manual methods


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Knowledge and Skill Requirements

Traditional measurement requires knowledge of anatomy,especially locations, names, and shapes of bones and muscles

Understanding of how to read measurement scales, how tomeasure weights, how to handle instruments.

Advanced technologies require understanding principles ofelectronics, lasers, photography, video devices necessary

Statistics knowledge to plan measurement surveys, reduce dataand analyze data, forcast and estimate values

Helpful to have successful planning experience dealing withprioritization of time and processes in an efficient and effectiveorder

Artistic, line-drawing skills to depict measurement equipment andhow it is used for scientific illustration


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Knowledge and Skill Requirements

Knowledge of mathematics (algebra, geometry, andtrigonometry), mechanical aspects of physics, mechanicalengineering principles and practices

Need to be able to read engineering orthographic drawings andunderstand the concepts of mass properties, force, and torque

Talent for visualizing geometric relationships and performingelementary design work for planning mockup evaluations

Ability to perform hands-on construction of models, specialmeasurement devices, full-scale mockups from a variety ofmaterials

Since many techniques require touching people and directing

their movements to assume certain postures, need to be able toexplain your activity in a credible manner

Must be able to develop a friendly relationship with subjects whilemaintaining a professional attitude


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Planning for Measurements

Fundamental requirement when selectingmeasurements and methods is to plan ahead tosatisfy users of the data produced Imagine future applications

Perform task analyses on future uses of the data Ask potential users what they need (face to face or use of

questionaire

After list of perceived needs is compiled, creative

methods to estimate some dimensions may bedeveloped to help limit the number and kind ofdimensions to be measured (use the systemsapproach)


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Remember that most anthropometric measurements representsamples taken at one point in time (cross-sectional survey).Rarely are individuals tracked in a longitudinal survey

Sequential surveys will reveal changes in means, variabilities,correlations, and proportions of body parts that may be causedby attrition from death, illness, disinterest, aging, selection, ordietary changes.

Remember there are significant changes in proportions ofdifferent racial and ethnic groups surveyed at different times that

may affect body proportion averages Remember to consider these changes not only when deciding on

sampling procedures but also when assessing the accuracy andmeaning of available anthropometric data. This is especiallyimportant with regard to age brackets because of relatively rapid

changes during youth and extreme age


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Elements of a Measurement Plan

Varying degrees of planning required

Facilities, subjects, paperwork to recruit subjects,

legal release of data, purchasing or building

instruments/equipment, obtaining services ofthose who will measure/analyze data

Scheduling transport, arranging for housing,

feeding, sanitation, and thermal comfort of

subjects; scheduling and distribution of work ofthe measurers, checking data before entry into

records, recording data efficiently


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Facilities

Private space for disrobing

Adequate room for stands, jigs, chairs, desks, andother furnishings

Storage of instruments and supplies

Workload and time required at each station (if morethan one) for balanced, smooth flow of subjectsthrough facility

To limit confusion caused by audible reading ofinstructions and measurements, recommend use ofseparate rooms when more than one subject beingtested at the same time


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Equipment

Measuring team must obtain/have available

anthropometric instruments and chairs,

tables, jigs, and fixtures in a sufficient number

for each measuring site plus spares Computers at each station for checking and

recording data (eliminates transcription of

data Forms, recording sheets, other supplies may

also be needed


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Checking Software and Procedures

Remember, every measurement instrument madeby human beings is subject to error. Misread scales

Transposed digits

Judgment/rounding

Subjects may make inadvertent motions ormeasures may be inconsistent based on thepressure applied (Gavan, 1950). There are tables

of expected and acceptable variations inmeasurement for each dimension (Gordon, 1988;Gordon and Bradmiller, 1992) as well as accuracysummaries of various scales


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Procedures (continued)

Desirable to perform each measurement twice and compare theresults to see if the readings are the same or acceptably close

Computers and some software available allow comparison ofdetected measurements against detected measurements toidentify potential errors. Software may also accumulate data as

measuring proceeds and develop a continually updatedprediction of expected population statistical extremes (e.g., 2-3standard deviations) for each dimension measured.

As collection continues, software may be able to calculatedispersion values around average trends (regressions of one

dimension on one or more others). (Churchill, et al., 1988). May consider regression formulas to test for outliers or deviant

measures to be expected in a population of measures


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Personnel

Each measuring site typically requires two people: one to recordand one to conduct measurements.

If complicated adjustments are required, a third technician maybe needed.

Best if a female measurer works with female subjects and a maleconducts measurements on male subjects especially whenmeasurements are made in sex-sensitive areas

May consider a receptionist to manage scheduling andappearance times, for paperwork management, and foranswering questions at the beginning of the measuring process.

Subject selection is a key concern and may require severalrecruiters.


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Training

Measurers need to be trained in proper techniques and tested toassure the principal investigator that all are using the sametechniques

Consistancy among measures requires hours of practice. PIneeds to check that each measurer will obtain the same resultswith repeated measures.

Training time will depend on new skills to be learned andpersonnel background.

May consider preparing a videotape of the measurementmethods as a more feasible and cost effective method of training

Video taped records of measuring may also serve as an effective

supplement to written documentation of methods used in thesurvey and can be very helpful in standardizing data (Gordon etal., 1989a, 1989b). This becomes increasingly important withlarge surveys.


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Scheduling

The number and relative complexity of measurements should bedivided equitably among the measuring teams to make efficientuse of their time and ensure a smooth flow of subjects

Commonly the measurer and recorder alternate tasks after asuitable period (say an hour) to reduce fatigue and boredom

Scheduling should consider procedures for ensuring health andsafety.

When direct contact methods are used, provisions should bemade to prevent the transmission of disease. Instruments shouldbe wiped with alcohol before each use

Consider giving subjects disposable paper slippers and washableshorts


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Administrative Concerns

Need to consider and resolve and problems

with:

pay (unless volunteers are used)

Lines of authority

Permission to use buildings and rooms

Scheduling of work hours

Ensure that the planning efforts are carriedout through effective and timely actions by all

involved in the surveys


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What to Measure?

When planning an anthropometric survey,developers are faced with conflicting goals indeciding what parts and attributes to measure. Industrial Applications workplace design

Body segment lengths and heights Some breadths

Some depths

Few circumferences

Clothing Design/Size Distributions

Circumferences

Surface areas

Few lengths and heights


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Physiological Studies

Volumes

Densities

Areas

Computer Modeling workspace design/manual

materials handling

Joint centers of rotation

Inter-joint link lengths relative to skin surfaces Offsets in relation to consistent, 3D coordinate systems


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Regardless of the measurement devices/media used, thequestion of what to measure for engineering anthropometryMUST include postures Standing posture

Standard upright sitting posture Certain postures that permit maximum reach with the arms and

legs

Future needs for the location of joint centers may dictate severaldifferent postures for each joint that can be flexed or extended inorder to locate effective centers of joint rotation.

Ideally, a full set of contours for the entire body should bescanned in several postures to provide details of body cross-sections so that joint centers of rotation can be derived.

Models incorporating a full set of contours for the whole bodymay prove useful in many different applications These ideas have rarely been achieved due to the constraints of

time, money, and available technology If contour data are not gathered, measures should obtain many

more depths, breadths, and offsets than is typical of currentpractice.


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Historical Practice and Measuring Standards

Standard measurements needed for

comparative purposes and forecasting trends

Ideas about which dimensions should be

standard have gradually changed with

purposes of anthropometric measurements Major shift in goals for the use of data away from

purely scientific studies of differences among

peoples of various parts of the world toward

engineering applications (which are also changing


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Surveys done by/for the USAF present highquality documentation Good for teaching about commonly used

measurement methods and instruments

Frequently include text and illustrations oftechniques with line drawings and photographs

Anthropometric Standardization ReferenceManual (Lohman, Roche, and Martorell,1988) is a more readily accessiblecommercial publication

Book includes pictures and illustrations Emphasizes measurements of interest for sports

medicine and performance rather than design ofwork space and clothing


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What are the accepted standards for measurementnaming, measurement selection, and measurementmethodology? Titles of landmarks and measurement methods written in

German by Martin (1928) and later revised (Martin andKnussman, 1988; Martin and Saller, 1957) (out of print).

Certain general approaches to establishing names fordimensions have evolved and appear consistentlythroughout the literature on physical and engineeringanthropometry.

Various compilations but little consensus

Anthropometric Source Book (NASA, 1978a,b,c)

Electronic Human Modeling (CSERIAC, 1991) workshopbut mainly concerned with medical imaging and softwarecommunication standards rather than anthropometry fordesign


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Society of Automotive Engineers (SAE) held meetings(1990) for setting standards and naming anthropometricdimensions, performing measurements, and selecting apreferred minimum list of measurements

Various source books (Donelson and Gordon, 1991;Gordon et al., 1989a,b; Clauser et al., 1987) illustrate thevarious landmarks (key features marked on the body priorto measurement) used to identify locations of underlyingbone features

Although many measurements are common to all past

large-scale military surveys, some notable exceptionsinfluence applications of data to design (e.g., Waist Heightand Buttock-Heel Length)


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Waist Height

Either of two easily confusable measurements may sometimesbe erroneously listed simply as Waist Height

Dimension name should indicate which of two commonlandmarks was used for the Waist Height measurement

Naval (omphalion in some reports)

Natural Indentation place where the middle portion of the trunk isnarrowest (as seen from front or back) and where the circumferenceis generally smallest). Difficult to locate on very obese persons (oftenresulting in arbitrary decision

Often easy to locate on military personnel

Can be defined as half the between the 10th rib and top of the pelvis

(iliocristale) Place an elastic cord with round cross section, adjust its length to apply

moderate tension, release tension, cord will see the height with thesmallest circumference) height then marked and circumferencemeasured with a tape.


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ButtockHeel Length

A subtle problem relating to definition of measurement andpostures used in measuring and the ultimate use of the dataused.

Buttock-leg length, buttock-heel length, functional leg length, totalleg length.

CAD generate models and drafting manikins is a theoreticalupright sitting posture with legs fully extended forward at the kneewould be desirable (note, upper and lower legs in alignment andthe sum of the distances from heel to hip joint (approximatelyequal to Trochanteric Height) could be subtracted from Buttock-Leg length to determine horizontal location of the hip joint

Knee bent posture is more realistic when back is upright

Men cannot actually achieve the extended posture when sittingwith a hip angle of 90 degrees (mean is 2.3 cm longer than thetheoretical length with sd of .64 greater


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Clauser is yet another solution but introduces error in averagelength of perhaps 2.2 cm depending on the angle of the leg fromhorizontal

Perhaps consider Idealized Buttock-Heel length by addingButtock-knee length to Flexed knee-heel length, standing (which

can be either difference between Stature and Kneeling Height todetermine Flexed Knee-heel Length standing.

Issues of sitting heights are lack of weight on the heal pads andjoints and subtle leaning postures involved in stable standingorientations that can produce small changes in overall length.

Joints measured landmark to landmark are often slightly longer

With increased accuracy requirements come more careful anddetailed attention to effects of posture and gravitational load ondifferences between landmarks.


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Summary

For each population, you must read the descriptions

of how the measurements were made

Researchers and writers dealing with anthropometry

should Attempt to use standard methods when possible

Accurately describe each measurement method used,

especially if it is unusual or if no commonly recognized

standard is available;

Locate all such descriptions together in reports and

handbooks so that they can be readily compared.


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Assignment

Next time we meet, be prepared to conduct some

anthropometric dimension measurements

Each of you should be dressed or be prepared to

change into some athletic clothing, preferably thincloth (like running pants)

You should be prepared to be both a Subject, a

Measurer, and a Data Collection Agent

We will shift roles as we measure variousanthropometric dimensions

Documents

Week 6 - Assessment and Design