lecture5 8 skovde pp

8/2/2019 Lecture5 8 Skovde PP

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Ergonomic Design with

Virtual Applications

Lecture 8Controls and Displays

Professor Keith CaseSchool of Technology and Society

University of Skvde

Mechanical and Manufacturing EngineeringLoughborough University


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The Human-Machine Interface

Controls andDisplays in Train


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Control Selection, Design & Use

Type of Control

Consider as extension

of operators limb

Use natural motion ofarm, wrist, leg, ankle,foot, etc and avoidawkward postures ormotions


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Feedback

Provide feedback toindicate what is beingaccomplished by the

control input

Resistance

Sufficient resistance to

dampen spurious input,but not so much as tocause muscle fatigue ordifficulty in maintaining

operating position


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Position

To give suitable posturefor user population

throughout the motionof the control (may

need to considerdynamic interaction with

other controlmovements)


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Size and Shape

Compatible withoperators hands,fingers or feet

Implications of shoes orgloves

Consider grip,inadvertent use and

adequate clearanceShape compatible withcontrol motion eground knobs for rotation


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Interface Surface

Depends on activity may be smooth so thatposition can be easilychanged (egmousepad), knurling forgrip, etc


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One/Two Handed

OperationTwo hands give

greater precision and

force but may preventthe simultaneous useof another control


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Hand vs Foot operated Controls

Use of toes impracticalExtremely versatile finger motions

Difficult and slowRapid repetitive motions

Standing difficultSit/stand

Similar operationsTwo hands performing differentoperations

Few motions, eg push, pressWide range of motions. eg push, pull,rotate and press and squeeze

Usually cannot be seen duringoperation

Usually easier to see

High force capabilityLimited forceLimited precisionPrecise inputs

FootHand

This is a specific Fitts List


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Control Selection Guide

The general principles outlined abovecan be used to generate specificcontrols (most of the following examples

come from Woodsons Human FactorsDesign Handbook)


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Non-critical operations. Place within easy reach

Critical operations (panic buttons). Locate sothat inadvertent operation is impossible

Use with hand controller to change controlmode etc, multi-button keyboards, fire button,etc. Often thumb operated position

accordingly

Finger or thumb operation


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Binary operation. eg on/off, start/stop. May bespring-loaded to return after giving a momentaryreading. May use three position, but avoid four ormore. Guard against accidental use.

Alternative to toggle switch may be illuminated.Do not mix toggle and rocker switches on samepanel.

2-24 selections (channels, circuits, etc) to savespace. Identify pointing end and providemechanical detents.


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Some control motions seem more natural due to: Musculo-skeletal configuration

Handedness

Habit etc.

Where these are well-established it can beextremely dangerous to try to change them. e.g. allpeople would expect a car to turn right with aclockwise motion of the steering wheel

Control Motion Stereotypes


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Other examples:



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Pull knobs have a well-established direction of

operation (conflicts with previous stereotypes)

National conventions. eg UK light switches

down/ON, US up/ON. Left is usually LOW/OFF andright HIGH/ON

Rotary switches clockwise to increase value or ON

Rotary switches used by the left hand should useanti-clockwise for increase in value !


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Knowledge of theoperating mechanics of a

control may determine themotion


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Control Motion StereotypesLocation of the control in

relation to the operator mayaffect perception of its use.Generally assume that it

will be operated as if theoperator is facing the panel


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Keypads/Keyboards

Keypads have becomestereotyped according tofunction without reference to

human orientation. TheQWERTY keyboard is anextreme example where

engineering totallydominated human issues


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Non-stereotypical Keyboards


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Control and Display Direction ofMotion Relationships

These are dominated byright-handed expectationsand the perceived

mechanical relationship. Theleft-handed arrangement isconsidered less desirable (as

blind operation would almostcertainly revert to right-handed expectation).


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Expectation versus AppearancePush buttons extending out of the panel

to imply that it is to be depressed

Pointer shaped controls imply positioningin discrete steps

Circular knobs imply continuous valuecontrol. Serrations reinforce thisperception

Pull type knob (again serrations wouldimply that it should also be rotated)

Rocker or toggle suggests a switch withtwo positions


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Size and ShapeGeneral principles

maximise hand-controlcontact area wherelarge forces are

required, for precisioncontrol ensure thatdiameter is sufficient for

all fingers and thumb. Ifspace is limited usesmall diameter but

longer controls.

lecture5 8 skovde pp

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