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Human Factors in Engineering &

Design

References:

Human Factors in Engineering & Design: Sanders &McCormick

Human Factors Essentials : Peggy & Barry Tillman

Introduction to Ergonomics: R S Bridges

Fundamentals of Industrial Ergonomics: B Mustafa Pulat

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Chapter I : TOPICS

Evolution of Human Factors

Introduction & Definitions

Assumptions & Significance Applications

Man-Machine-Environment Interaction

System, Types & Characteristics Systems Approach to Human Factors

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Evolution of Human Factors

Why ?

System failures during & after World War II

Fatality & Casualties

Human element taken for granted

Military to Industrial:

Theory & data developed for militaryadopted for industrial sector

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Human Factors: Neglect

Human beings taken for granted for theirefficiencies or inefficiencies

Only after significant damage, correctivemeasures initiated

Solution: Human Factors isthe process

ofdesigningfor human use:Child Car Safety Seat

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Cavemen in the Space Age; Howto Design Systems for Humans

Stone-Age People in the Jet Age

Punch line: Keep things very clear

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HUMAN FACTORS: Profession

Ensures equipment systems easy & safeto operate

HF Researcher: Gathers data & analyzes

(on work, human capabilities & limitations)

HF Engineer: Work with designers to

ensure people operate & maintain system HF Professional: Ensures totality to the

product generated through improvements

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Definitions

Websters:An applied science concerned withcharacteristics of people that need to be

considered in designing and arranging thingsthat they use in order that people & things willinteract most effectively and safely.

Psychologists:

HF is the body of knowledge about humanabilities, human limitations & other humancharacteristics that are relevant to design.

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Definitions (Contd.)

Polish Educator on Ergonomics:

Ergon = Work ; Nomos = Laws

Laws governing work

General definition:

HF is the study of the interactions between human

beings & objects they use and the environment in whichthey function

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Definitions (Contd.) :

Sanders & McCormick3 branched approach:

The Central focus: Consideration of human beings in thedesign of objects, machinery & environments.

The Objectives: Increase the effectiveness of Man-Machine system while maintaining human wellbeing.

The Central Approach: Systematic application of

available data on human characteristic to design of system/ procedures.

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Definition: Sanders & McCormick

COMFORT

ERGONOMICS

WELL-BEING EFFICIENCY:

Physical, Mental, Production

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Human FactorsResearch V/s Application

Scientific Research of Human Characteristics :Factors

Application of HF data to design :Applied Ergonomics

Science Combining Research & Application of Human data:ThroughHF Experts, Resources, Tools & principles to improve design

Example:NASA standards for nutritional meals for space dwellers

Research(Factors)

HF Application(Applied HF)

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ASSUMPTIONS IN ERGONOMICS

Linking efficiency of person-object system - If personcannot work effectively, the system efficiency isalso degraded

People achieve more when motivated

Objects, equipments, environment characteristics

influence human performance.

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ACCIDENTS AND INJURIES

Data compiled in the US indicate amongst the top 10

work related diseases, ergonomic related are:

Musculoskeletal (2) Amputation, fracture, eye loss, traumatic deaths (4)

Cardiovascular diseases (5) Noise-induced loss of hearing (8) Psychological disorders (10)

COMPENSATION PAID INCREASING mostly dueto back injuries & over exertion

Training & Education helps reduce negative impact.

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Organizations in Ergonomics in the US

OSHA : Occupational Safety & Health Act(generates safety standards & inspects)

NIOSH : National Institute of OccupationalSafety & Health (conducts research to support OSHA)

MSHA : Mine Safety & Health Administration(OSHAs equivalent in mining activity)

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Other Professional bodies:

HFS : Human Factors Society

IIE : Institute of Industrial Engineers

IEA : International Ergonomics Association ILO : International Labor Organization

WHO : World Health Organization

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Costs of Ignoring Ergonomics

Less production output Increased lost time

Higher material cost

Increased absenteeism

Low quality work Injuries, strains & compensation

Increased probability of errors

Less spare capacity for emergencies Increased labor turnover

POTENTIAL GAINS are the reverse of the above

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Types of Ergonomic related Problems

Anthropometric:

Relates to the dimensional conflict between functionalspace geometry & the human body.

Cognitive:Refers to the information overload or under load ininformation processing requirements (memory strain)

Musculoskeletal:Refers to the strain to the muscular & skeletal systems(slipped disc)

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Types of Ergonomic related Problems - Contd.

Cardiovascular:

Refers to the strain to circulatory system including the heart(increased pumping to meet excess oxygen requirement)

Psychomotor:

Refers to the strain to the psychomotor system humancapabilities & redefinition of job

Note:Stress under each case must be analyzed separately &

remedial package suggested.Education & Training - improves / extend human capabilities,create awareness and avoid damages.

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The Role of Ergonomics Specialist

All Engineers expected to possess Ergonomicbackground

An Organization with over 1500 employees to have afull-time HF Expert to handle complex HF problems(IIE study)

Interest of study ranges vastly layouts & seating,manual material handling hand tool design to softwaredesign, Job evaluation to training.

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The Role of Ergonomics Specialist

(Contd.)

Interdisciplinary science experts trained inPsychology, Anthropometry, Education, Engineering,Medicine and a host of other disciplines.

Prevent disasters Bhopal Gas tragedy, Belgianferry sinking, Chernobyl incident, Air crashes andcollusions

Improper design of controls and non-considerationsof human capabilities.

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Human Factors Applications

Automobile Design:

Flexible design to suit all categories of people tall short, overweight, handicapped etc.

Reduce driver fatigue, improve visibility, safetyand decrease accidents.

Business Offices:

Comfortable Physical environment lighting,ventilation, noise control, layout

Improve informal atmosphere

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(Contd.)

Personnel Selection & Training:

Design of programs for effective selection andtraining activities improves performance.

US Army use HF expertise to design programsfor selection of crew members for combatmissions, write training manuals etc.

Selection process should include HFconsiderations.

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(Contd.)

Computers: Can help design computer & software for

programmers & users stores clerk eliminatingmanual records.

Speed, color contrast & information overload

Manufacturing , Assembly Plants:

Robots a common feature in assembly line

manufacture Activity chart, Process chart. Interaction of automated machines with humans and

its harmful effects.

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(Contd.)

Schools & other facilities:

Design of classrooms, rest rooms, sportsfacilities & other special purpose areas.

To consider age, physical size, capabilityof individual users.

Facilities present & future use.

New technologies.

Social changes

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Application of Human engineeringprinciples used in the design not exactlyscience, but an approach to problems ofdesigning & constructing things people use

comfortably, efficiently and with less fatigue.

Designer not necessarily represents the user& Everything designed for the user

A chrome touch product does not alwaysattract a repeat customer.

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Concept of System central to HF:

System: An entity that exists to carryout a function or purpose.

Composed of man, machine and other things

with which they interact.System maybe classified as:Physical system: Assemblage of components

Theoretical system: Assemblage of concepts

Biological system: Assemblage of body parts

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Steps in design of System

Purpose recognition

Analyze recognition

Understand System requirement

Design System which meets requirements

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Functions as a closed loop system

Comprising combination of human beings and componentsone or more each interacting to produce some desired output

Machine a device that is physically verifiable or a facility withcertain function Welding machine, Hair Drier.

Systems less delineate or marked out & more amorphous or

vague or formless like a hospital service.

M M hi E i t I t ti

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Man-Machine Interaction

Display Unit displays current Machine status

Reception of Data - Receptors

Operator Mind / Brain Analyzes information

Decision making on control action

Action through Control Devices

Operational changes machine status

Display unit displays revised machine status

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Perceived Information Displays

Internal & ExternalEquipment status

Controls

Information Processing

Output Mechanism:

Speech* Manual Control

MAN MACHINE

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ELEMENTS OF MAN-MACHINE SYSTEM

TASK

Film ware

Human Operator

Hardware Software

Input Output

Environment

Feedback

ELEMENTS OF MAN MACHINE SYSTEM

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ELEMENTS OF MAN-MACHINE SYSTEM(Contd.)

Environment: Effect of environment on othersystem elements to be considered.

Types of environment:

Social:Task pressures, Isolation, group dynamics.

Physical:Illumination, Noise, Vibration, Heat, Cold.


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Hardware:

Elements that are physically verifiable.

Are better responded to by humans

Examples:

Display units, controls, equipments, dimensions,

shapes, layout, chairs.


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Software:

Helps operator identify in an adequate manner, givecomplete access to information in a most comfortable

manner.Helps understand the hardware operating procedure.

Examples:Menu structures, Screen layout, messages, instructionmanuals.


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Film ware:Software loaded hardware is film ware.

Identifies the degree of compatibility of the software onthe hardware ease of combining or working together.

Example:

Labeling for proper identification.


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Human / Operator:Human operator assisted with equipment carryout task.

They complement one another.

Human variables to be considered by designers:

Age, physique, gender, training & education.


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Task:Also called as Systemobjective.

Clearly defined.

Central to all elements.

Human Task parameters to be assessed:(Assuming equipment perform properly)

Speed of performance, strength requirements,accuracy requirements and task sequencing.

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TYPES OR CLASSES OF SYSTEMS

Operator role in system:

Acquires information, decides and acts

Degree of system automation decides

human coverage, degree of involvement,control & importance.

E.g.: Fully automated control room operatorto a cyclist cycling through a unknownterrain.

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TYPES OR CLASSES OF SYSTEMS Contd.

Manual Systems: (Hand tools)

Adjusts task parameters like force & pacebased on information received andperceived by operator.

Highly flexible.

Less repeatability.

Human physical energy source.

TYPES OR CLASSES OF SYSTEMS C d

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Mechanical Systems: (machine)

Semi automatic systems. Power & other functions by machines.

Better repeatability.

Well integrated parts. Designed to operate with less vibrations.

Human function essentially Controls the

functions or power delivered by the m/c.

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Automated Systems: ( Robots)

Operational functions with little humanintervention or attention sensing, decision

making & action. No human intervention a mistaken belief.

Emergency analysis allow human intervention.

Fully automated systems also require humans toinstall, program, reprogram & maintain operatingcondition.

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Man versus MachineDesigner to:

Have the user in mind.

Be able to describe exactly what operator has to dofor operating & maintaining the equipment.

Determine if a function to be performed manually orautomatic

There is no easy Yes /No answer.Needs analysis of capabilities of Humans & M/cs.

Man versus Machine

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Man versus Machine

Wide variety of stimuli

Perceiving patterns &generalizing about them

Judgment on events thatcannot be completelydefined

Adopting flexible

procedures

Analyzing & originality inproblem solving

Monitoring Man & Machine

For routine, repetitive &precise operation

Quick response to signals

Applying large force,smoothly and precisely

Storing & recalling largeamount of info in quickly

Operate in environment

hazardous to humans

Humans Excel In Machines Excel In

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Man versus Machine Contd.

Operate in environmenthazardous to humans

Performance rapid andcomplex computationaccurately

Sensitive to stimuli beyond therange of humans

Perform different tasks at thesame time

Perform deductive processes

Insensitive to external factors

Profit from past experience &alter course of action

Inductive reasoning

Perform even when overloaded

Humans Excel In Machines Excel In

Characteristics of Systems

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Characteristics of Systems

1. Systems are purposive:

Exists for accomplishing goal or objective else systems

would be collection of odds & ends.

2. Systems can Hierarchical:

Part of a larger system, concept of sub-systems. When

one analyses a complex system, one may question:

Where does one start and stop?

Depends

How far into the system should one go?As far as one could go.

Characteristics of Systems - Contd

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Characteristics of Systems Contd.

3. Systems operate in Environment:

Environment of a system is everything outside its boundaries set.

Depending upon how the boundaries are drawn, the environmentcan range from:

a. Immediate environment:

Office Workstation, Work Chair.

b. Intermediate environment:

Office, Home, Factory, School.

c. General environment:

Community, City, highway system, Neighborhood.

Ch t i ti f S t C td

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Characteristics of Systems - Contd.Systems operate in Environment - Contd.:

Physical environment may not be cooperative oradaptable for modifications: Heater & Coolers.

Peoples nature essentially passive.

To impose certain constraints on their movements orrestricting the field of view.

To predetermine certain aspects of behavior: tryingto see edge of road on a rainy night

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Characteristics of Systems - Contd.

4. Components serve Functions:

Each component or element (lowest levelof analysis) to serve at least one or more

system goals.

Components involve combination of thefollowing four functions:

Sensing, Storing, Processing, Decisionmaking, Action

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Components serve Functions:

Information Storage

Sensing

(Info. Receiving)

Info

Processing&

Decision

Action:

Physical controlCommunication

InformationInput

System

Output


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Characteristics of Systems - Contd. Sensing: Order copy for production plan.

Info Storing: Tables of record, discs, tapes. Processing & Decision making: Info sensed & stored.

Human: Act or not to

Machine: Decision to be programmed throughcomputer, gear arrangements, levers, circuits.

Action: Consequence of decision

Physical control Action: activating control devices

physically, modifications of objects, materials.Communication Action: Through voice (humans)

Signals, records (Eqpt.)


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5. Components Interact:

Each component has an effect however

small, on the other components.

Components work together to achievesystem objectives (elementary subsystems)

Characteristics of Systems Contd

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Characteristics of Systems - Contd.6. Systems, Subsystems & Components have

Input & Output: Inputs to a subsystem is an output from another

component / subsystem. A system receives input from environment &

delivers output to the environment.

Inputs may be physical, impulses or info.

Open Loop: Die that is cast (unguided system) Closed Loop: continuous operationchem. process.

(Feedback & control)


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7. Reliability of Systems:

Dependability of system (Man/Machine) onsuccessful completion of an discrete event.

Starting of a car

Electronic Teller 999 / 1000 right, R=0.999Another measure of Reliability:

MTTF : Mean Time To Failure


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Characteristics of Systems - Contd. Reliability of system depends upon reliability of

individual components in the system. Depends on how they combine.

a. Components in Series / Sequence:

Failure of one component leads to the failure of the

system.Component failures are independent of oneanother.

As more are added, the system reliability reduces.

RMax.Overall = RComponent with Least

RMin.Overall < RComponent with Least


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b. Components in Parallel:

Referred to as Back up or Redundancyarrangements as one component backs upthe other during failure.

For system to fail all parallel componentsneed to fail.

Human functions generally to have parallel

components as humans are the weak link.

SYSTEMS APPROACH

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SYSTEMS APPROACH

Systematic study involve large detailscovering minute aspects

Frequently, not possible to approach from

right the beginning (some decisions alreadytaken)

Systematic Approach applicable to evenminor modifications/additions to old system

General steps using Systems Approach:

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Ge e a steps us g Syste s pp oac

Information Phase: Data about operational

requirements, constraints, environment & peopleusing the system collected

Planning Phase:Explore alternate approaches

to meet stated objectives, keeping in mindeconomy, ease of mfg, reliability, Maintenance &servicing

Selection Phase:Select the design optimizingall factors in info & planning & proceed with thedesign using HF principles

General steps using Systems Approach:

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p g y pp(Contd.)

Test Phase: Construct models, mock ups ofdesign to evaluate / test against stated objectives. Incase of dynamic parameters, prepare simulatedmodels

Field Test Phase: Test design under actualoperating conditions, utilizing actual personnel / enduser

Follow up surveys to provide feedback for designimprovements.

S stems Approach to H man Engineering

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Systems Approach to Human EngineeringRequirement & Task Analysis: It is the Infophase

Eg.:System Requirements - Safe transport of goods by shipSystem Limitations - Ship on rivers onlyOperational Functions - Control of traffic, navigation,

communication & supervisionTask Analysis involves:Dividing functions into building blocks or tasks, skill &knowledge requirements, workplace assignment & errorpotential.

Tasks may further be divided into sub-tasks

Functions

Systems Approach to Human Engineering

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Error Analysis:

Equipment malfunction, human error potential to beestimated. This is a part of Task analysis.

Objective: to develop system success probability based

on task/subtask success probabilities & theirrelationship, so that system achieves the goal with adegree of confidence.

Human tasks to be provided with certain minimalpermissible errors or be made fault tolerant.


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Time Planning:To ensure that system achieve results in theplanned period of time.

Designer to review the resource (Man & M/c)allocation & its optimal use by Time planning.



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Use of Operational Sequence Diagramming (OSD):

Gives a pictorial description of system Displays functions & their elements in sequential logic

Helps understand the relationship between functions

Help trace the flow of info, identifying inputs & outputs

Time Line Analysis:

When time info is added to flow charting technique

This analysis will provide the overload / under load

conditions for the resourcesGantt chart, Man-M/c process chart, Precedence diagrams


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Human resource planning:

A design process is incomplete without humanresource planning & implementation.

Steps in Resource Planning:Developing Staffing requirements

Selection

Training & Development

Follow-up


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Developing Staffing requirements:

Data gathered from detailed Task analysis, identifyingoperators needs & skill in a quantified manner.

Selection:Applicants should be exposed to situations of job

requirement through well designed tests, only thosepossessing skill are to be selected, else it may lead toinjury to operator or the people around.


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Training & Development:

Training for upgrading skill for adequate performanceon job, may not be for all potential personnel.

Techniques of training: On the Job & Class room

Applicable for lower level in hierarchyDevelopment to improve personal traits such as

Judgmental abilities, communication, leadership

Applicable for higher level in hierarchy

Follow-up:

Periodic follow up be carried out on personnelafter actual job assignment for some time.


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Detailed design & acquisition (Development):

Involves reviewing the preliminary plans in greaterdetail.

Taking final decisions on all steps.

Includes detailing, purchase & acquisition of all

necessary equipments, software's & other resources


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Testing:

Testing NOTthe last step in development process.

Tests are conducted throughout Planning,Preliminary & detailed design, development &acquisition & operational stages.

Tests ensures that:System requirements fulfilled

Defects identified & rectified early

Undesirable features not introduced into design

Design decisions are of quality

There would be optimal interaction between people& equipment


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Testing Techniques:

Testing on all elements of system includingoperational relationships.

Mock up tests:

Static Mock up test: Cheaper technique

Dimensional accuracy maintainedEg.: 2 or 3 dimensional templates, drawings,checklists, questionnaires.

Functional Mock up test: Costly, use true set up

Eg. Simulation, Modeling & other quantitativetechniques to make strategic decisions on relativeposition of equipment & workstation etc.


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Design synthesis:

1. Imperative to go back and make corrections &revisions after each step/cycle

2. Iterates between alternate methods of achievingfunctional system objectives till the best workable

combination is obtained3. Ensures good compatibility between requirements& expected results

4. After field operation, expect immediate positive

resultInitial drop in productivity or success attributed toLearning period, resistance to change and not betaken as failure of design of system

SYSTEM DEVELOPMENT CYCLE

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Define System requirements& Limitations

Define Operationalfunctions

TEST

&

REVISE

ITERATE

Bottom

Top1. SYSTEM PLANNING

2. INITIAL DESIGN


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FunctionAllocation

MachineTasks

TEST

&

REVISE

ITERATE

Bottom

Top2. INITIAL DESIGN

HumanTasks

Joint Tasks

Task Analysis

3. DETAIL DESIGN & DEVELOPMENT


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ITERATE

Bottom

Top

TEST

&

REVISE

Hardware, Software, Film ware,HR Development

TimePlans

ContingencyAnalysis

Selection &Training

3. DETAIL DESIGN & DEVELOPMENT

ErrorAnalysis

ManpowerPlanning

4. TESTING


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ITERA

TE

Bottom

Top

TEST

&

REVISE

Field Test

Drawings Mock ups QuantitativeTechniques

Templates

4. TESTING

TEST

&

REVISE

5. OPERATIONAL PHASE

End of Chapter Questions

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p Q Select a human-object system in your environment.

Analyze its constituent elements in terms of

hardware, software, tasks, human, environment.Discuss each element & its relationships with otherelements.

Select a manual human-object system in yourenvironment. How can it be converted first into amechanical & then into a automated system?

Select a human-object system in your environment.Detail its operational functions. Carry out a detailedanalysis for one of its functions & display theresults on a flowchart with allocated resources approximate estimate

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