Introduction to Human Factors/Ergonomics

(HFE)Engineering Anthropometry

- Hardianto Iridiastadi, Ph.D.

Introduction

- Variability in physical dimensions
- Studied earlier in Anthoropology (study of

mankind) - Interest in physical aspects (beginning of

anthropometry) - Later, data are used for biomechanics

investigations - The need to design workplaces to accomodate

differences in body dimensions

Human variation

Factors Affecting Anthropometrical Variation

- Age
- Gender
- Race Ethnic
- Socio-economics
- Occupation
- Life style
- Circadian
- Secular trend
- Measurement

Ergonomic Implications

- International markets
- Different target countries
- Transfer of technology
- Job selection
- Healthy worker effect
- Fit the man to the job

Engineering Anthropometry

- a branch of science originating from

anthropology that attempts to describe the

physical dimensions of the (human) body - anthropos man
- metron measure

Types of Anthropometric Data

- Physical (Static) anthropometry which addresses

basic physical dimensions of the body. - Functional anthropometry concerned with

physical dimensions of the body relevant to

particular activities or tasks. - Newtonian data body segment mass data and data

about forces that can be exerted in different

tasks/postures

Applications

- Tools design
- Consumer product design
- Workplace design
- Interior design

Applied Anthropometry

Measurement Techniques

- Positions
- Standing naturally upright
- Standing stretched to maximum height
- Lean against a wall
- Sitting upright
- Lying (supine posture)
- Anatomical position (see Kroemer et al)

Measurement Techniques

- Some key measurement terms
- Height
- Breadth
- Depth
- Distance
- Curvature
- Circumference
- Reach

Measuring Devices

(No Transcript)

(No Transcript)

Newer Measuring Devices

- Photograph
- Use of grids
- Image processing techniques
- Can record all three dimensional aspects
- Infinite number of measurements
- Drawbacks
- Parallax
- Body landmarks cannot be palpated

Newer Measuring Devices

- Whole body scanner
- Ergonomic center UI
- 50,000 - 400,000
- Hundreds of variables
- Standing and
- seated posture
- Combined with
- modeling software
- (Jack, Mannequin, etc.)

Sample Anthropometric Data

Statistics

- Coefficient of variation
- Data diversity sd/mean
- CV 5 (10 for strength data)
- Large CV should be suspected
- Standard error of the mean (se)
- se sd/vn
- Useful for describing confidence interval
- E.g., 95 CI mean 1.96 se

Statistics

- Means (?) and standard deviations (?) are

typically reported for anthropometric data (often

separated by gender) - Use of these value implicitly assumes a Normal

distribution. Assumption is reasonable for most

human data. - Percentiles can easily be calculated from mean

and std.dev. using these formulas and/or standard

statistical tables (usually z).

Statistics

- Percentile
- Commonly used 5th, 95th, 50th (median)
- Lower-limit dimension the smaller the system,

the more unusable by the largest user ? Use high

percentile - Upper-limit dimension the bigger the system, the

more unusable by smallest user ? Use low

percentile

Statistics - Standard Normal Variate

- Z (y-?)/?
- Normally distributed with mean 0 and variance

1 - z is N(0,1)
- From tables of normal cumulative probabilities
- Pzz(A) A
- Example if zA 2, A 0.9772 (two std.dev.

above mean is the 97.7-ile) - Properties of z
- zA gt 0 above mean (gt50-ile)
- zA 0 at mean (50-ile)
- zA lt 0 below mean (lt50-ile)

Normal Distribution Table

Percentile Example

- For female stature (from Table)
- ? 160.5 cm
- ? 6.6 cm
- What female stature represents the 37.5th -ile?
- From normal distribution
- z(37.5) -0.32
- Thus, X(37.5) ? z?
- 160.5 - (0.32)(6.6)
- 158.4 cm

Anthropometric Data Variances

- To combine anthropometric dimension, need to

calculate a new distribution for the combined

measures, accounting also for the covariance

(Cov) between measures (M mean S std. dev.)

MXY MX MY SXY SX2 SY2

2Cov(X,Y)1/2 SXY SX2 SY2

2(rXY)(SX)(SY)1/2 MX-Y MX - MY SX-Y SX2

SY2 - 2Cov(X,Y)1/2 SX-Y SX2 SY2 -

2(rXY)(SX)(SY)1/2

- Means add, variances do not!

Class Activity

Anthropometrical Design Procedures

- Determine dimensions of product which are

critical for design (considering effectiveness,

safety and comfort) - Determine the related body dimensions
- Select user population (who will use the product

or workplace) - Conduct reference study to find secondary data,

if available (considering population

characteristics) or conduct measurement - Select percentile

The Average Human

- Anthropometric data for individuals is often

estimated using stature or body weight in linear

regression equations. - Ex average link lengths as a proportion of body

stature - Advantages
- Simplicity
- Disadvantages
- relationships are not necessarily linear, nor the

same for all individuals - Values represent averages for a portion of a

specific population

Anthropometry in Design

- Anthropometric data is most often used to specify

reach and clearance dimensions. - The criterion values most often used
- Reach 5 Female
- Clearances 95 Male
- Try to accommodate as large as possible user

population within constraints

Design Approaches

- Design for extremes
- emphasize one 'tail' of distribution
- Design for average
- emphasize the center of a population distribution
- Design for adjustability
- emphasize that all potential users/consumers are

'equal - Varying ranges of accommodation
- 5th-95th ile typical
- 25th-75 ile less critical functions or

infrequent use - 1st - 99th ile more critical functions /- low

- 0.01 - 99.99 ile risk of severe outcomes

Design for Extremes

- Example Door Height
- Assuming a normal distribution
- z (X - ?)/?
- Obtain z gt -ile from stats table
- What height to accommodate? (95th-ile male)
- ? 69 ? 2.8 (from anthropometric table)
- z0.95 1.645 (X - 69)/2.8 gt X 73.6
- Additional allowances?
- Hair
- Hats and shoes
- Gait
- Etc.

Examples

Which design strategy should be employed?

- leg clearance at a work table
- finger clearance for a recessed button
- height of an overhead conveyor system
- grip size for a power tool
- weight of a power tool
- height of a conveyor
- strength required to turn off an emergency valve

General Strategies and Recommendations

- Design for Average
- Usually the worst approach both larger and

smaller users wont be accommodated - Design for Extremes
- Clearance use 95th percentile male
- Reach use 5th percentile female
- Safety accommodate gt99 of population
- Design for Adjustability
- Preferred method, but range and degrees of

adjustment are difficult to specify

Homework

- Working in groups
- Select a workplace near campus. Identify any

ergonomic mismatch. Suggest how the workplace

can be better designed from the perspective of

engineering anthropometry. You should outline the

design approach. - Pick a journal paper that discusses the use of

anthropometric data in design. Submit a one-page

summary (in Indonesian) of the paper. Also submit

softcopy of the paper.