1ISE 311 - Ch. 17/18

Human–Machine System The boundary between the human and the machine is the

“user interface.” Information flows from human to machine through controls. Displays include instruments, labels, and accompanying

printed instructions and warnings.

HUMAN

CONTROLS

MACHINE

DISPLAYS

Physical Environment

2ISE 311 - Ch. 17/18

Guideline 1: Select the Proper Type of Control

Types of systems: Open-loop Closed-loop

Discrete vs continuous Select part of the body to implement mental

command Choose mechanical interface between

human body and machine interior Consider amount of human power required Consider errors and speed

CONTROLS

3ISE 311 - Ch. 17/18

Guideline 2: Select the Proper Control Characteristics

Force People variables:

Muscles used User population Percentile designed for Control variables

Control options Keys and pushbuttons Knobs Cranks

Control variables: Purpose Design

Hand wheels Foot/leg controls

CONTROLS

4ISE 311 - Ch. 17/18

Control Options Keys and Pushbuttons

Knobs

Cranks

CONTROLS

5ISE 311 - Ch. 17/18

Control Options (cont.) Hand Wheels

Foot–Leg Controls

CONTROLS

6ISE 311 - Ch. 17/18

Guideline 3: Prevent Unintended Activation

More severe consequences require greater precautions.

Consider that operators may bypass the guard if it makes operation difficult.

All equipment should have an emergency stop control.

Consider two reaction times: Human (sensing, deciding, carrying out) Machine

CONTROLS

7ISE 311 - Ch. 17/18

Methods of Reducing Accidental Activation Key or special tool activation (locks) Interlocks Barriers or covers Recessing Spacing Resistance Direction

CONTROLS

8ISE 311 - Ch. 17/18

Guideline 4: Prevent Incorrect Identification Labeling

Color

Shape

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CONTROLS

9ISE 311 - Ch. 17/18

Size

Mode of operation

Location

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CONTROLS

10ISE 311 - Ch. 17/18

Guideline 5: Make Accomplishments Equal Intentions

Require verification of critical commands. Make complex sequences of actions user-

friendly. Use more care and testing for actions with

multiple steps. Check input for validity. For continuous controls, consider

control/response ratio. Control positions often act as displays.

CONTROLS

11ISE 311 - Ch. 17/18

Population Stereotypes

Engineer’s habit patterns may not be the user’s habit patterns.

Stereotypes are often country-specific (light switches, water faucets, car blinkers). See table 17.9, pg. 323 for US conventional control

movements

Consider labeling.

CONTROLS

12ISE 311 - Ch. 17/18

Guideline 6: Properly Locate and Arrange the Controls

Arrangement of Controls Group related controls and

displays together. Minimize layout

complexity. Have blank space on the

panel. Hand Controls

Keyboards Manipulative controls

Knobs Switches

Force controls

Foot Controls Avoid foot controls for

standing operators. For continuous control, leg

should fully extend at bottom of stroke.

For discrete control, use one leg.

Have straight line between pedal and back support.

Comfort may be more important than force capability.

Design to avoid fatigue.

CONTROLS

13ISE 311 - Ch. 17/18

Human–Machine System: Displays

Causes of Failure: Legibility or detectability Understanding

14ISE 311 - Ch. 17/18

Displaying InformationInform

atio

n

Display

DISPLAYS

15ISE 311 - Ch. 17/18

Guideline 1: Select Legible Characters

Font Use printed characters Avoid Roman numerals Upper/lower case:

For short messages, use all caps For text or longer messages, use mixed-case with large

open spaces in letters For VDT, use more pixels and lower dot pitch

Size Character height = K × Distance from eye

K = 0.004, 0.006, 0.0017, 0.0073 radians Visual angle should be 15–25 min of arc

1 min of arc = 0.00029 rad

DISPLAYS

16ISE 311 - Ch. 17/18

DISPLAYS

17ISE 311 - Ch. 17/18

DISPLAYS

18ISE 311 - Ch. 17/18

Guideline 2: Arrange Characters & Symbols

Text – clear and legible

Codes – don’t rely on memory

Abbreviations – use with caution

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DISPLAYS

19ISE 311 - Ch. 17/18

Guideline 3: Decide on Type of Display

General Considerations Task/job – what’s the purpose of the display? User characteristics Standardization (see examples, next slide)

Menus – lists of options Deep vs Shallow Structure according to how information is used Minimize complexity / maximize understanding

DISPLAYS

20ISE 311 - Ch. 17/18

DISPLAYS

21ISE 311 - Ch. 17/18

Display Types Menus – lists of options

Tables – make the information easy to find

Formulas – simplify calculations

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DISPLAYS

22ISE 311 - Ch. 17/18

Graphs – make relationships visible

Symbolic Messages – be sure they’re understood

Maps – locate in space and time

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DISPLAYS

Display Types

23ISE 311 - Ch. 17/18

Guideline 4: Project Your Message

Slides 35 mm slides Computer projection

Transparencies Video

DISPLAYS

24ISE 311 - Ch. 17/18

Guideline 5: Select the Instrument Display

Discrete: finite choice of options Continuous: point on a scale

Analog Digital

Representational: provide diagram or picture Video Compatible with:

Operator’s internal representation of the variable Control operation

DISPLAYS

25ISE 311 - Ch. 17/18

Warning Messages

Type of failure: False signals Missing signals Multiple signals

Should be both visual and aural Should be within primary field of view Should provide guidance information Urgency / immediacy of warning should match

severity of danger

DISPLAYS

26ISE 311 - Ch. 17/18

Guideline 6: Locate/Arrange the Display

Location

Arrangement

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DISPLAYS