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Chapter 15

Controls

2

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Human-System Interaction

Attend

Observe

Remember

Think Act

attend to one taskattend to several tasks

see/readhearfeel (palpate)detectdiscriminaterecognizeperceive

memorizerecall (long-/short-term)maintain mental model

calculatedecidesolvedevelop alternativeschoose alternativeselect response

reachgraspmove/manipulatespeakwalk/runrespond

Environment

Displays System Controls

stimuli responses

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MD-11 Cockpit

Copyright Harri Koskinen, used with permission, downloaded from http://www.airliners.net/open.file/463667/M/ 30 Jun 04

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Control Principles

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Control Compatibility Principles● Spatial Compatibility

– Proximity– Physical Similarity– Arrangement

● Movement Compatibility

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Proximity Compatibility

● Place control close to display or controlled element.

vs.

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Proximity (2)

● Issues– Accessibility– Safety– Cost– Technical Feasibility– Practical Considerations

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● Make the physical appearance of the control similar to that of the display or controlled element.

Physical Similarity

Instrument panel

Landing gear lever handle shaped like wheel(side view).

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Arrangement

● Arrange groups of controls in same patterns as groups of displays or controlled elements.

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Movement Compatibility

● Population stereotypes● Up-to-increase● Right-to-increase● Clockwise-to-increase● Warrick’s Principle● Vehicular control

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Population Stereotypes

● An expectation a specific group of people have about how to interpret or to behave.

● Examples– Walk through right-hand door– Turn clockwise to increase– Move up to increase

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Up - to - Increase

● Move control up to increase parameter or display value

● Example– Slider

implies increased value

● Limits– Physical arrangement restrictions

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Right - to - Increase

● Move control to right to increase display value or parameter

● Example:– Move lever to right to increase temperature setting

in auto temp control system.● Limits

– Physical arrangement restrictions

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Clockwise - to - Increase

● Rotate control clockwise to increase parameter or display value.

● Example– Turn knob on stereo clockwise to increase volume

● Limits– Possible conflict with display movement (e.g. fixed

pointer moving scale)

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Warrick’s Principle

● Pointer should move in same direction as nearest point on control knob.

● Example

● Limits– conflict with other principles:

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Vehicular Control

● Principles and Examples

● Limits: Physical arrangement limitations

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Control Characteristics

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Force and Displacement

● Force– Required force to move control– May be

● constant over range of control movement● proportional to control displacement

● Displacement– Linear– Rotational

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Control / Response Ratio(C/R Ratio)

● Low C/R ratio– High sensitivity, high gain– Good for rapid, coarse adjustment

● High C/R ratio– Low sensitivity, low gain– Good for fine, precise adjustment

● “Optimal” C/R ratio– Knobs: 0.2 - 0.8– Levers: 2.5 - 4.0

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Control Resistance

● Importance– Preventing inadvertent activation– Feedback– Precise positioning

● Problems– Difficult activation– Difficult precise postioning

● Types– Static (initial friction)– Elastic (resistance a displacement - e.g. spring)– Viscous (resistance a velocity)– Inertial (resistance a acceleration)

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Feedback

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Control Coding

● Size

● Shape

● Texture

● Location

● Type

● Color

● Label

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Preventing Inadvertent Activation

● Provide resistance● Recess● Locate outside movement areas● Orient to require conscious movement● Provide guard● Lock● Require sequential operation● Require redundant activation● Require multiple operators

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Examples of Controls

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Classification of Controls

Discrete/linear– manual pushbutton– legend switch– toggle switch– foot pushbutton– detent lever– keyboard

• Continuous/linear– lever– joystick– pedal

• Discrete/rotary– rotary selector– snap-action

thumbwheel

• Continuous/rotary– knob– thumbwheel– wheel– yoke– crank– rotary pedal

Rotary

Linear

ContinuousDiscrete

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Keyboards: QWERTY

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Keyboards: The Dvorak Layout

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Keyboards: Alphabetic Layout (1)

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Keyboards:Alphabetic Layout (2)

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A B C D

E F G H

I J K L

M N O P

Q R S T

U V W X

Y Z

Keyboards: Other Alphabetic Layouts

A B C D E

F G H I J

K L M N O

P Q R S T

U V W X Y

Z

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Ergonomic Keyboards

Microsoft Elite Keyboard

GoldTouch Adjustable Keyboard

SafeType Keyboard

Contoured KeyboardSource: http://www.ergonomicsmadeeasy.com

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Chord Keyboards(Chorded Keyboards)

Twiddler2, http://www.handykey.com/MicroWriter handheld word processor (~1980),http://en.wikipedia.org/

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Chord Keyboards(Chorded Keyboards)

Braille Writer, http://en.wikipedia.org/

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Membrane Keyboards

Yan Chuen keyboards, http://www.globalsources.com/

Pannam medical keyboards, http://www.pannam.com/

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Touchscreens

http://www.touchscreens.com/

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Pen Controls

http://www.wacom.com

wacom pen displaywacom tablet PC systems

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Multifunction Display Buttons(F/A - 18 Cockpit)

Source: AirSim Images, http://www.netset.co.uk/flight/aircraft/jpegs

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F/A-18 HOTAS (Hands - On Throttle And Stick)

● All essential controls on– throttle lever (left hand)– stick (right hand)

● Pilot need not remove hands from throttle lever or stick to control most important aircraft systems

High Rev Simulators HOTAS,http://hirevsims.com/

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Trackballs

Evergreen Systems industrial trackball,http://www.trackballs.com/Logitech Cordless Trackman Wheel,

http://www.tigerdirect.com

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Eye Trackers

tobii eye controlled assistive technology,http://www.tobii.com/

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LapSim Laparoscopy Simulator(“instruments” with force feedback)

Photo courtesy of Alex Gandsas, MD.Used with permission.SurgicalScience LapSim,

http://www.surgical-science.com/

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Voice Input

● Benefits– single utterance to select from many options– natural communication channel– time-share with other actions

● Costs– subtle differences in sounds– variability of sounds– limited continuous speech capabilities– training required (speaker-dependent systems)– difficulty in noisy environments– effects of stress– not suitable for continuous control

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Control Design/Selection Principles and Guidelines

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Control Design/Selection: Prerequisites

● Perform process/task analysis● Determine control’s function● Determine info needs of operator with respect to control

– location and ID– current setting – changes in setting

● Determine requirements of control subtask– importance– precision and accuracy– speed– force

● Determine consequences of inadvertent activation● Determine workspace requirements

– available locations, space– operator location, orientation– relationship to displays and other controls

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Control Design/Selection: General Guidelines (1)

● Selection– Use discrete controls for discrete applications.– Use continuous control for continuous applications.– Use multi-rotation controls for precise settings, long ranges.– Select for movement compatibility.– Select controls that can be easily identified.– Minimize the number of controls.

● Location, orientation– Locate and orient for compatibility.

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Control Design/Selection: General Guidelines(2)

● Design– Do not overburden any one limb.– Combine functionally related controls.– Consider the least capable user WRT force, speed, accuracy,

geometry.– Design for natural movement.– Keep control movements short.– Design for feedback.– Provide extra cues for power-assisted controls.– Design control surfaces to prevent slipping.– Provide enough resistance to prevent inadvertent activation.– Design to withstand abuse.

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Workstation Design Relevant to ControlsArrange the workstation logically.

1. Accommodate primary visual tasks.2. Place controls for primary visual tasks (next slide).3. Preserve control / display relationships, e.g.,

population stereotypes up-increase etc.

4. Arrange by sequence of use.5. Arrange by frequency of use.6. Arrange to be consistent with other systems.

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Control Grouping

● Component clusters, spacing between groups● Borders around groups● Groups in recessed areas● Groups in raised areas● Color or shading around group● Groups on inclined areas● Groups on separate modules