Control and Controls

IE 366 Human-Machine System Displays Controls Other Subsystems Environment Human(s)

3 MD-11 Cockpit Copyright  Harri Koskinen, used with permission, downloaded from 30 Jun 04

4 Basic Principles of Control ● Decision Complexity – Hick-Hyman law of reaction time – Decision complexity advantage: small # of complex decisions > large number of simple ones ● Response expectancy – Expectancy → speed accuracy ● Speed-accuracy trade-off ● Feedback ● Compatibility

5 Compatibility Principles ● Spatial Compatibility – Proximity – Physical Similarity – Arrangement ● Movement Compatibility – Population Stereotypes – Up-to-increase – etc.

6 Proximity Principle: Place control close to display or controlled element Examples: √ ✖✔

IE 366 ● 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).

8 Arrangement Principle: Arrange groups of controls in same patterns as groups of displays or controlled elements. √ ✖ ✔ ✖ ✔

9 Movement Compatibility ● Population stereotypes ● Up-to-increase ● Right-to-increase ● Clockwise-to-increase ● Warrick’s Principle ● Scale-side Principle ● Movement in different planes ● Vehicular control

10 Population Stereotypes A population stereotype is 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 –Upward movement to increase

11 Up - to - Increase Principle: Move control up to increase parameter or display value Example – Slider implies increased value

12 Right - to - Increase Principle: Move control to right to increase display value or parameter Example: Move lever to right to increase temperature setting in auto temp control system.

13 Clockwise - to - Increase Principle: Rotate control clockwise to increase parameter or display value Example: Turn knob on stereo clockwise to increase volume

14 Warrick’s Principle Principle: Pointer should move in same direction as nearest point on control knob Examples

15 Scale Side Principle Principle –Pointer should move in same direction as the part of control knob located in the same relative position on the knob as the scale is on display –Examples

16 Vehicular Control Principles and Examples

Controls (Devices)

18 Control Classification Continuous/linear ● lever ● joystick ● pedal Discrete/rotary ● rotary selector ● snap-action ● thumbwheel Continuous/rotary ● knob ● thumbwheel ● wheel ● yoke ● crank ● rotary pedal Rotary Linear ContinuousDiscrete Discrete/linear ● manual pushbutton ● legend switch ● toggle switch ● foot pushbutton ● detent lever ● keyboard

19 Keyboards: QWERTY Source: Wikimedia commons, downloaded 2 Nov 10 from

20 Keyboards: The Dvorak Layout Source: Wikimedia commons, downloaded 2 Nov 10 from

21 Keyboards: Alphabetic Layout (1) Source: The ABCkeyboard, downloaded 2 Nov 10 from

22 Keyboards:Alphabetic Layout (2)

23 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 ABCDE FGHIJ KLMN O PQRST UVWXY Z

Keyboards: Ergonomic Keyboard Source: ergonomics.com/

Chord Keyboard (2) Source: HandyKey Corporation

Membrane Keyboard Source: Low Key Corp (

Touchscreen Source:

Digitizing Tablet Source: Pandora’s ToyBox ( m)

F/A - 18 Cockpit Source: AirSim Images (

IE 366 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,

IE 366 Trackballs Evergreen Systems industrial trackball, Logitech Cordless Trackman Wheel,

32 Voice Input ● Advantages – single utterance to select from many options – natural communication channel – time-share with other actions ● Disadvantages – 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

Control Characteristics

34 Force and Displacement ● Force – Required force to move control – May be ● constant over range of control movement ● proportional to control displacement ● Displacement – Linear – Rotational

35 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: –Levers: Control Movement Change in Controlled Parameter C/R Ratio =

36 Control Resistance Importance –Preventing inadvertent activation –Feedback –Precise positioning Problems –Difficult activation –Difficult precise postioning Types –Static (initial friction) –Elastic (resistance  displacement - e.g. spring) –Viscous (resistance  velocity) –Inertial (resistance  acceleration)

37 Feedback

38 Control Coding Size Shape Texture Location Type Color Label

39 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

IE 366 Control Design/Selection Principles and Guidelines

IE 366 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

IE 366 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.

IE 366 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.

IE 366 Workstation Design Relevant to Controls Arrange 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.

IE 366 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

Tracking

47 Tracking ● Definition – Human attempts to controls a continuous system so that one or more of its parameters matches one or more varying reference values ● Examples – Driving a car – Flying an airplane – Watching a bird with binoculars

48 Tracking Control System (simulated) input to system: u(t) input (target): i(t) output from system: o(t) Human Display Control

49 Pursuit Tracking Display Display Control System (simulated) input to system: u(t) input (target): i(t) output from system: o(t) target cursor

50 Compensatory Tracking Display Display Control System (simulated) input to system: u(t) input (target): i(t) o(t) error  error: e(t) For a real example, see

51 System Dynamics Control Order: ● Zero-Order Control: Position Control – Direct (e.g., stylus-cursor) – Indirect (e.g., mouse-cursor) ● First-Order Control: Rate/Velocity Control – e.g., joystick, cursor key – Isotonic joystick (moves) – Isometric joystick (rigid) ● Second-Order Control: Acceleration Control ● Higher-Order Control: Jerk, etc. Control

52 Zero - Order (Position) Control Example: computer mouse u(t) = fore/aft mouse position on desk o(t) = cursor vertical position on screen o(t)

53 First - Order (Rate) Control Example: car accelerator pedal u(t) = pedal angle o(t) = car distance from start o(t)

54 Second - Order (Acceleration) Control Example: car steering u(t) = wheel angle o(t) = car lateral distance from centerline o(t)

55 Human Performance in Tracking ● Processing time: – time delays: lag ● Bandwidth: – rate for corrections - < Hz ● Anticipation: – not very good at anticipating slowly- responding systems

56 Factors Affecting Tracking Performance ● Preview helps ● Type of Display: Pursuit > Compensatory (?) ● Time Lags decrease performance ● Display Resolution: higher resolution improves performance ● Pacing: self-paced easier

57 Facilitating Tracking Performance ● Aiding – Control affects both rate and position – Improves performance in some cases ● Predictor Displays – Display o(t) and o’(t + ∆t) – Can improve performance ● Quickening – Display o’(t + ∆t) only – Not as helpful as predictors

58 Other Tracking/Continuous Control Considerations ● Stability – Closed-loop instability (e.g., Pilot-Induced Oscillation, PIO) ● Examples – NASA F8 NASA F8 – Fighter Fighter – F22 F22 – Shuttle Shuttle ● Contributing Factors ● Lag ● High gain ● Attempts to correct too quickly ● Fix these ● Open-loop vs closed-loop systems – Closed-loop (feedback) relies on feedback – Open-loop (no feedback) relies on accurate mental model, skill-based processing