ECE 796/896 Human Factor Engineering Chapter 22 Human Factors in System design

Design 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 System 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. 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 Performance specifications 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 Definition What functions does the system perform in order to meet its objectives. Tool: Flow diagram

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Stage 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 Functions 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 based Allocation made on least cost, but if humans are available they may need be used. 4. Affective or Cognitive Support Allocations Affective - emotional support for humans Cognitive - information needs

Dynamic Allocation Make decisions during system operation, by the operator. Ex: Autopilots, cruise control.

Human Performance Requirements 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 Analysis 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.

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Job 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 Design 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 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 HF 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 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 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 Design Materials that promote acceptable human performance Imbedded training - training built into the system

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

Special Problems in HF Evaluation Special problems: much work is carried out in laboratories Subjects, criteria, Experimental procedures and controls, research setting

HF 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. 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. 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. 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. 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. 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.