Transcript ECE 796/896 Human Factor Engineering

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
22.2
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.
22.4
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 informationreceiving 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.