1 DESIGN FOR HUMAN FACTORS. 2

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DESIGN FOR HUMAN FACTORS

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HUMAN - FACTORS ENGINEERING

Human factors data may exist as:

1. Expert judgments

2. Experience and common sense

3. Design standards

4. Established design principles

5. Graphic representations

6. Quantitative data tables

7. Mathematical functions and expressions

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DESIGNING USER-FRIENDLY PRODUCTS

Some important questions to ask:

1. Can each control device be easily identified?

2. Is the visual display arrangement optimized?

3. What sensory channel would be most suitable for a message to be communicated

through the displays?

4. Does the design effectively use human decision making and adaptive capabilities?

5. Are the controls effectively designed with respect to shape, size, accessibility?

6. Does the design effectively address the possibility of grouping the tasks to be

performed into jobs?

7. Are control devices compatible with their corresponding displays, with respect to

human factors?

8. For satisfactory levels of human performance, were such environmental factors as

noise, temperature, and illumination taken into consideration?

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• Considering human factors during the design process means

being aware of the user of the product as the occupant of a

workspace, a source of power, a sensor, and a controller .

• Readily available statistical data should be used in designing size

and power relationships between a human user and the product

being designed.

• Product safety implies concern for injury to humans and for

damage to the device itself, other equipment, or the environment.

HUMAN INTERACTIONS WITH A PRODUCT

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Safety can be

• designed into a product

• added on

• the hazard warned against

The first of these is best; the last is often unacceptable.


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The preferred position of the elbow when holding a device when force or weight are involved.

Incorrect Correct

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TYPES OF VISUAL DISPLAYS

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APPROPRIATE USES OF COMMON VISUAL DISPLAYS

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Redesigned cloths dryer control panel

USER FRIENDLY DESIGN

Original cloths dryer panel

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Before Tool Redesign After Tool Redesign

The handle on the right is much more user-friendly for a lever or tool that must be pushed with considerable force.

USER FRIENDLY DESIGN

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"Photograph courtesy of www.baddesigns.com"

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Bad Good?

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Bad

Which way to turn for warmer water?

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Q. What are you, stupid? These things aren't bad designs! You're just too

stupid to figure out how to use them! You have no common sense.

You're too lazy to read instructions.

A. Things designed for common use should not require that people have

an above average intelligence and should not require them to expend a

lot of mental energy or time learning, problem solving or reading

instructions. If designers want their products to be widely used, they

are well-advised to design them so that they are easy to use.

www.baddesigns.com

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www.baddesigns.com

Q. How can I make sure the product I am working on is easy to use?

A. First, determine who is going to use your product - for example, the

group's age and experience level. Determine what features are going to be

used most often and what basic tasks people will perform with the product.

Build a prototype of your product that allows people to perform the tasks -

at least to some degree. Higher fidelity prototypes are better, but good

feedback can be obtained from low fidelity prototypes.

Next, find some people who are like the ones who will be using your

product and have them perform some typical tasks with the prototype.

Observe the people to see what confused them, where they make mistakes

or are inefficient. Then modify the prototype to reduce or eliminate these

problems. Repeat this process until you have eliminated the problems.

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• Human-factors engineering deals with applying the knowledge

gained from human physiology and psychology (concerning the

characteristics and capabilities of the human body and mind) to

product design and use.

• These include such factors as: height, weight, vision, hearing,

posture, strength, age, intelligence, educational level, dexterity,

and reaction time.

• A variety of qualitative and numeric data are available to describe

these characteristics.

HUMAN - FACTORS ENGINEERING

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People often:

• are reluctant to admit errors

• perform tasks while thinking about other things

• misread or overlook instructions and labels

• respond irrationally in emergency situations

• become complacent after successfully handling dangerous items

over a longer period of time

GENERAL OBSERVATIONS OF HUMAN BEHAVIOR

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People often:

• fail to recheck outlined procedures for errors

• poor estimators of speed, clearance, or distance (they frequently

overestimate short distances and underestimate larger distances )

• too impatient to take the time needed to observe precautions

• reluctant to admit that they cannot see objects well enough, due

either to poor eyesight or to inadequate illumination and use their

hands for examining or testing.

GENERAL OBSERVATIONS OF HUMAN BEHAVIOR

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1. Operation error - attributed to operating personnel.

Causes: improper procedures, poor surrounding environment, task

complexity, overload conditions, operator carelessness, inadequate

personnel training or selection, and incorrect operating procedures.

CATEGORIES OF HUMAN ERROR

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2. Maintenance error - occur in the field and are attributable to

maintenance personnel.

Examples: the use of the wrong grease to lubricate the equipment,

and the incorrect calibration of the equipment.


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3. Design error - reflect inadequate designs.

Causes: inadequate analysis of the system requirements,

designer's bias toward a specific design, insufficient time spent on

the design.


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4. Inspection error

Purpose of inspection is to uncover all items with defects, however,

inspection effectiveness often averages around 85%.


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5. Fabrication error - result from poor workmanship during

product assembly.

Causes: poor blueprints, inadequate illumination, poor

workstation layout, excessive noise etc.

CATEGORIES OF HUMAN ERROR (CONT’D)

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6. Installation error - attributed to incorrect or incomplete

installation of the product.

Primary cause: failure to follow the instructions or

blueprints.


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7. Handling error - due to the inappropriate or improper storage

or transport of a product, and can result in damage to the

product.

Example: improper packaging for shipment.


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8. Contributory error

This classification covers those errors that are difficult to identify

as either human or hardware.


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Hartford Civic Centre Arena roof collapse.

Failure occurred due to modeling error; model was not validated.

http://www.eng.uab.edu/cee/faculty/ndelatte/case_studies_project/Hartford%20Civic%20Center/hartford.htm#Top


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Sinking of Sleipner A platform

Failure occurred due to due to discretization error; model was not verified.

http://www.ima.umn.edu/~arnold/disasters/sleipner.html


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The following must be considered when designing products:

• Safety standards and criteria for safe design.

• How a product will function and the impact of user/operator error.

• Analysis of safety problems, failures, and malfunctions during

prototype testing.

• Is the product toxic? Can it be easily maintained? Does it have

protective guards? Warning labels? Hot surface? Rotating blades

and sharp edges? etc.

• Sudden acceleration/deceleration, pressure hazards, radiation,

vibration,electrical and fire hazards, etc.

PRODUCT SAFETY AND LIABILITY

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The following must be considered when designing products:

• Adequate factor of safety and system redundancy.

• Cost of failure repair, cost of malfunction, cost of injury, cost of

component and subassembly replacement.

• Impact of product usage on the environment.

• Instructions for use, troubleshooting, minor repair, and routine

maintenance.

• Design deficiencies such as inadequate identification, lighting, and

accessibility.

PRODUCT SAFETY AND LIABILITY

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• Eliminate hazards by modifying design, maintenance procedures, or

material used.

• Control hazards at their source through guarding, enclosing, or

capturing.

• Provide necessary warnings/instructions in documentation and

display them in effective places.

SAFETY GUIDELINES

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• Educate people to be aware of hazards and to follow appropriate

steps to avoid them.

• Expect certain abuse and misuse, and take necessary measures to

reduce their consequences.

• Provide suitable protective equipment to people, and develop steps

for ensuring that it is effectively used.

SAFETY GUIDELINES

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1. Caution - used under conditions where hazards or unsafe

practices may lead to minor personal injury, and/or minor

damage to the product or to property.

2. Danger - used where immediate hazards (if they occur)

would lead to severe personal injury or death.

3. Warning - used where hazards or unsafe acts (if they occur)

could lead to severe personal injury or death.

LABELS AND WARNINGS

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LABELS AND WARNINGS

[Ullman 1992]

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1 DESIGN FOR HUMAN FACTORS. 2