Human Factors Engineering Principles of System Design

Components Serve Functions Systems Information Processing & Decision Making Info Input Output Sensing information receiving Action Functions physical controls Information Storage Components Interact Systems, Subsystems, and Components Have Inputs and Outputs

Systems Human - Machine System Information Processing Controlling Controls Sensing Displays Operation InputOutput Human Being Machine

Human Aspects of System Design  Designing the system with the human element as a paramount issue in evaluating the design’s overall success.  Recognizing that a system which overlooks or inadvertently incorporates an opportunity for human error can lead to catastrophic results.

System Design Process Molecularization Definition of System Options Addressing Unknown Elements Transformation Iterative Cycling Competition Within Design Group From Competing Requirements Design Relevance

System Design Process Molecularization Task Analysis and Subdivision of Tasks Overall Task SubTask ASubTask BSubTask C

System Design Process Definition of System Options Design solutions based on system requirements Must understand system (and user) requirements Must account for limitations / constraints Technology Resources (Time, Funding, Personnel, etc)

System Design Process Addressing Unknown Elements  Specifically identify all expected users  Identify activity related user needs  Identify unexpected / incidental uses  Example – Kitchen Stove

Household Cooking Ranges

Design #1

Design #2

Design #3

System Design Process Transformation  Physical Requirements  Behavioral Implications  Physical Manifestations

System Design Process Iterative Cycle DesignTest & Evaluation New Information

System Design Process Competition  Within Design Team Sales, Administration, Manufacturing Software, Quality Assurance, Management Human Factors, Engineering  Ego Factors  Money, People, Power, Influence

System Design Process Relevance  Selling the Idea -  Design Team  Management  Customer

System Design Process Six Major Stages  Definition Implementation Test &  Evaluation  Stage 4  Stage 1 Stage 3 Stage 6  Stage 5  Stage 2

System Design Process Six Major Stages  1. Determine the Objects  2. Define the System  3. Basic Design  4. Interface Design  5. HFE Design Elements (Facilitation)  6. Testing and Evaluation

Stage One – Determine Objectives  What purpose will the system serve ?  What are the user’s needs ? Actual Perceived What are the system performance specifications ? Success Criteria System Constraints

Stage Two – System Definition  Define functions that support performance criteria Generalized Function (Unassigned)  Machine, Computer, Software, Human  Use a “want” function Not a “solution definition” function  Say what we want – not how to implement it !

Stage Three – Basic Design  Function Allocation Machine, Computer, Software, Human  Allocation Criteria Economy and/or superiority Grey Areas - Several nearly equal results

Function Allocation Guidelines  Humans  Inductive reasoning required  Perception of unusual / unexpected events  Application of novel solutions  Machines  Monitoring of prespecified events  Storing / retrieving coded information  Performing repetitive tasks  Exerting high levels of physical force

Function Allocation Guidelines  Mandatory Allocation  Balanced Value  Utilitarian and Cost Based Allocation  Affective and Cognitive Support Allocations

Mandatory Allocation  Based on system requirements, hostile environments,safety considerations, legal or labor constraints.

Balanced Value  Excellent  H  u m a  n Unsatisfactory Excellent Machine

Utilitarian Allocation  Assigning particular functions to human operators simply because they are present (cost effective?)

Affective and Cognitive Support  Affective Support Addressing the emotional (ego) elements Need for challenging work Need for being in control (personal security)  Cognitive Support Human need for relevant information in order to make rational decisions as required.

Stage Four – Interface Design  Most Important HFE Phase  Occurs only after Function Allocation  And in Conjunction with Stage Five (Facilitation)  Deals with -  Environmental Factors  Spaces, Displays, Controls  Computer / User Dialog  Cautions and Warnings

Stage Five – Facilitation  Planning phase for successful implementation of  HFE based support which helps ensure  Successful human performance.  Examples:  Instruction Manuals, Performance Aids,  Training Programs and Devices,  Personnel Selection Criteria

Stage Six - Testing and Evaluation  Evaluation – Measure of system development products (hardware, procedures, personnel) in order to verify that they perform as they as supposed to.  Human Factors Evaluation – Examination of the products to ensure the adequacy of the attributes that have implications regarding human performance.

Take Home Message  Each aspect of the design process must be examined to determine whether or not it is relevant;  and if so, appropriate attention should be paid to it.  Corollary: The design process by its nature is cyclic.