ECE 796/896ECE 796/896Human Factor Human Factor EngineeringEngineering

Chapter 22Chapter 22

Human Factors inHuman Factors in

System designSystem design

Design StagesDesign Stages

• 1. Determine Objectives & Performance specifications

• 2. Definition of the System

• 3. Basic Design

• 4. Interface Design

• 5. Facilitator Design

• 6. Testing and Evaluation

Characteristics of the Characteristics of the System design ProcessSystem design Process

• 1. Molecularization: goes from broad to fine• 2. Requirements are Forcing Functions: Design

options are developed to satisfy system requirements.

• 3. System Development is Discovery: unkown’s become clarified

• 4. System Development Involves Transformation: physical to behavioral

• 5. Time: Never enough time• 6. Cost: Never enough money

Cont.Cont.

• 7. Iteration: Tuning the design as more detailed information becomes available

• 8. Design Competition: Design is by groups - function under more dominant groups.

• 9. Relevance: Critical for the acceptance and judged value of behavioral inputs

Stage 1: Objectives and Stage 1: Objectives and Performance Performance

specificationsspecifications• Purposes of a system = objectives

• System performance specs. Detail what a system must do to meet the objectives.

• HF: ID system users and id the activity related needs of users

Stage 2: System DefinitionStage 2: System Definition

• What functions does the system perform in order to meet its objectives.

• Tool: Flow diagram

22.2

Stage 3: Basic DesignStage 3: Basic Design

• 1. Allocating functions to humans.

humans vs. machines - best attributes

automation

• 2. Specifications of human performance.

• 3. Task analysis

• 4. Job Design

Strategy for Allocation of Strategy for Allocation of FunctionsFunctions

• Allocations are made through expert judgment - art and a science.

• 4 rules for developing a strategy.– Mandatory Allocation: Task must go to the

human because of safety, labor, legal …– Balance of Value: Estimate the goodness

of the machine vs. the human for performing a task - plot values

Utilitarian or cost basedUtilitarian or cost based

• Allocation made on least cost, but if humans are available they may need beused.

4. Affective or Cognitive Support AllocationsAffective - emotional support for humansCognitive - information needs

Dynamic AllocationDynamic Allocation

• Make decisions during system operation, by the operator.

• Ex: Autopilots, cruise control.

Human Performance Human Performance RequirementsRequirements

• Characteristics to meet the system’s requirements.

• Accuracy,speed, time to develop proficiency, user satisfaction.

• If the requirements are beyond the capabilities, requirements might require redefinition.

Task Description and Task Description and AnalysisAnalysis

• Nature of the process: Start with the task and break it down into the smallest definable parts, in the sequence that it

performed.

Check each process step for , stimuli to

initiate the step, human decisions required, etc.

22.4

Job DesignJob Design

• Human Values in job design: Human Values in job design: – Job enrichment and enlargement, making

the tasks more complex, including inspection of their own work. There is some concern that not all people respond well to this approach.

Stage 4: Interface Stage 4: Interface DesignDesign

• Characteristics of Human-Machine and Human-software interfaces.

• 1. Gather and interpret human factors and human performance data.

• 2. Conduct attribute evaluations of suggested designs

• 3. Conduct human performance studies

How Engineers DesignHow Engineers Design

• How they use HF inputs• 1. Engineers are experience oriented.• 2. Engineers are often intuitive in their

thinking• 3. Engineers get down to the nitty-gritty

aspects• 4. Engineers do not know where to find

needed information (behavioral)

Gathering and Interpreting Gathering and Interpreting HF dataHF data

• Common Sense and experience• Comparative quantitative data• Sets of quantitative data - anthropometric• Principles - minimize glare• Mathematical functions - human performance

relationships• Graphical representation - tolerance to

acceleration• Judgment of experts• Design standards (noise standards)

Presentation of HF DataPresentation of HF Data

• 1. Eliminate general or ambiguous terms ( proper feel or high torque)

• 2. Present quantitative data in a manner consistent with designer preferences.

• 3. Eliminate narrative statements when data can be presented quantitatively.

• 4. Eliminate inconsistencies among standards.

• 5. Update standards on a timely basis

Attribute EvaluationsAttribute Evaluations

• Use of Checklists– Informal and verbal - written

• Walk-Through Evaluations– Use of mock-ups to show users

• Computer-Aided Design and Evaluation Aids– SAMMIE, CHESS, HECAD

Stage 5: Facilitator Stage 5: Facilitator DesignDesign

• Materials that promote acceptable human performance

• Imbedded training - training built into the system

Instruction MaterialsInstruction Materials

• Rules of thumb for manuals:– Less is more: avoid information overload– Avoid abstract information– Forget why’s; concentrate on how’s– Remember that learning will come from

doing– Forget the hype. Users have the product,

they want to set it up.

Use of illustrationsUse of illustrations

• Pictures :– Realistic photo or drawing of an object

• Symbols:– A photo are picture that represents something else

Simple Concept: perform a simple action

Complex Concept: Multiple actions

Stage 6: Testing and Stage 6: Testing and EvaluationEvaluation

• Human Factors Evaluation: examination of these products to ensure adequacy of attributes the have implications of human performance.

Special Problems in HF Special Problems in HF EvaluationEvaluation

• Special problems: much work is carried out in laboratories

• Subjects, criteria, Experimental procedures and controls, research setting

HF and System DesignHF and System Design

• 1. What functions need to be carried out to fulfill the system objective?

• 2. What options are available which should be performed by human beings?

• 3. For each function, what information external to the individual is required?

• 4. For information presented by displays, what sensory modality should be used ?

Cont.Cont.

• 5. For a given type of information what type of display should be used?

• 6. Are displays arranged optimally?• 7. Are the information inputs collectively w/

reasonable bounds for human information-receiving capacities?

• 8. Is their excessive timesharing ?• 9. Are decision making and adaptive abilities

appropriate for humans?

Cont.Cont.• 10. Are decisions to be made at any time within

the reasonable cap. Limits of humans?• 11. Do humans of basic control of auto systems ?• 12. When performing physical control, what is the

control devices?• 13. Each control device easily identifiable?• 14. Are controls designed properly, shape, size?• 15. Operational requirements of any given control

within bounds?

Cont.Cont.

• 16. Operational control compatible with the device it controls?

• 17. Control devices arranged conveniently and for optimum use

• 18. Work space suitable for the people who will use it

• 19. Are other feature arranged safely in the facility

• 20. Is visibility from the workstation satisfactory

Cont.Cont.• 21. Will communication avoid overloading the

individuals using it• 22. Are tasks grouped appropriately into jobs• 23. Tasks requiring timesharing avoid

overburdening any individual• 24. Provision for adequate redundancy• 25. Are jobs such that personnel can be trained to

do them• 26. Training period reasonable• 27. Work aids and training complement each other

Cont.Cont.

• 28. Do training simulators achieve a reasonable balance between costs and training

• 29. Is system designed for maintenance• 30. Do environmental conditions permit

optimum human performance• 31. Does the system meet performance

specs.• 32. Is human fulfillment reasonable.