1 ISE 412 Control & Response Selection Response Selection Response Execution

2 ISE 412 Types of Control:

3 ISE 412 Issues in Response Selection: Decision complexity Response expectancy Compatibility Speed-accuracy tradeoff Feedback Task Environment Control design

4 ISE 412 Choice Reaction Time: The HICK-HYMAN LAW says that choice reaction time is a function of the amount of information in a stimulus: RT = a + b H where, H is the amount of information a is simple reaction time b is the slope of the function (the amount of added processing time for each bit of information.) Intuitively - the more choices we have, the longer it will take to choose from among them.

5 ISE 412 Choice Reaction Time Example In the tetris-like game described last time, the simple reaction time and the choice reaction time when all pieces are equally likely is measured. The results are as follows:  simple reaction time, a = 300 msec.  choice reaction time for equally likely events, Rt eq = 800 msec. Then the probability of appearance of the individual pieces is changed as described. What is the new expected choice reaction time?

6 ISE 412 Movement Time: FITTS' LAW relates movement time to the distance and the size of the target. MT = a + b log 2 (2D/W) where, MT = movement time a & b = empirically derived constants D = distance of movement from start to target center W = width of the target Note: the term (2D/W) is sometimes referred to as the index of difficulty (ID), so that Fitts' Law becomes: MT = a + b log 2 (ID)

7 ISE 412 Movement Time Example W = _1 in_ D = _3.5 in_ W = _0.5 in_ D = _7 in_ a = 50 msec. MT = 200 msec. MT = __________

8 ISE 412 Movement Time: Side Note: we might also use Schmidt's Law for movements executed so fast they cannot benefit from visual feedback W = a + b(D/MT) where W is now the effective target width or the "standard deviation of the end point dispersion..".

9 ISE 412 Continuous Control Feedback control model for continuous control: Display Human operator Control Device System or Plant Disturbance input Target Cursor Wickens et. al, pg. 274

10 ISE 412 Tracking: Pursuit vs Compensatory Pursuit - “chasing” the target  Display “tells you where you are” in relation to the target  Examples: driving, visual flight, tracing a path Compensatory - reducing the error  Display “tells you where you should be” and the error  Examples: aircraft instrument landing system, glide slope indicator; “pong” game 

11 ISE 412 Input Frequency of movement of the target  bandwidth of the input  overshoot and undershoot errors depend on the range of magnitude changes  time lag errors depend on the frequency of changes " Look-ahead" or prediction  provide cues as to the direction and magnitude of the next change  fewer and smaller errors  smoother control motions

12 ISE 412 Control order (what type of controller is "best"?) 0-order (position)  e.g., moving the mouse to a position on the screen 1st -order (velocity)  e.g., joystick where increased control force increases the speed of response 2nd - order (acceleration)  e.g, low speed ship steering, rocket maneuvering Position Time Position Time Position Time

13 ISE 412 Problems of stability Closed-loop instability of the controlled system due to overcorrections, resulting in oscillations around the target. Due to:  time lags - delay between control input and system response  high gain - the system response to a given control input is too great for the operator to correctly control  inappropriate operator response - too fast for system response, possibly due to combination of time lags and high input bandwidth Design guidelines to reduce instability …  reduce time lags through preview / predictor displays, better display design  lower the gain  change control strategy  “open loop” operation

14 ISE 412 Control Input Devices Switch Knob Keyboard Mouse Voice Pointer Trackball/joystick Button

15 ISE 412 Buttons, switches, and knobs Recall design issues …  Physical feel  Size  Compatibility spatial, proximity pictorial realism, moving part frame of reference, conceptual (mental models)  Affordances and constraints  Movement time, reaction time

16 ISE 412 Keyboards and keypads Keyboards  Purpose  Layout QWERTY, DVORAK, alphabetic Keypads  Purpose  Layout telephone vs calculator Chordic keyboards

17 ISE 412 Mouse vs pointer For spatial tasks Direct vs indirect control  Pointer (light pen, touch screen, etc.) direct control faster, but less accurate parallax errors size issues with touch screen best for more complex spatial control movements  Mouse, touchpad, tablet indirect control more precise, but slower adjustable gain

18 ISE 412 Voice input

19 ISE 412 Technology issues in voice input … Noise control “Robust against drift” (i.e., not affected by stress, natural changes in speaker voice.) Encoding, buffers, and editing Prompting (visual and auditory, etc.) and feedback Remote data entry Interruption allowance, continuous recognition, gender independence Customization (vocabulary, branching, applications, communication modes, etc.) Queuing of input data Help functions, ease of use, etc. (from: Pulat, B.M. (1997) Fundamentals of Industrial Ergonomics (2nd ed), Ch. 10. Prospect Heights, IL: Waveland Press.)

20 ISE 412 Control-display compatibility AKA “Stimulus-Response Compatibility”  that is, what is the relationship between the stimulus (the content and format of the information) you receive and the response(s) available to you?  affects learning, response time, errors, and preference We have already discussed several aspects of human information processing that apply  sensory processing vision haptic/tactile senses etc.  attention  etc.

21 ISE 412 Control-Display Design Principles Modality Compatibility  degree to which the controls and displays utilize the same sensory modality.  Within-modality stimuli-response relationships are generally faster, e.g., for verbal task: ___________________________________ for spatial task: ___________________________________

22 ISE 412 Movement Compatibility  relationships between movements of displays and controls where the direction of movement of a control follows from expectations, e.g. steering wheel turns car in direction of wheel movement. Movement of a control can: 1. follow - display movement as in radar tracking. 2. control - display movement as when moving a computer mouse to reposition a cursor. 3. produce - a specific system response such as turning a car steering wheel to turn a car in the same direction (it's the reverse on a boat).

23 ISE 412 Spatial Compatibility  physical arrangement of controls and associated displays in space or physical similarity of displays and controls  e.g., identify which controls should go with which “display” below …

24 ISE 412 Rotary controls and rotary displays A.Fixed scales and moving pointers clockwise turn of pointer should result from clockwise turn of control and should represent and increase in the value. B.Moving scales and fixed pointers scale should rotate in the same direction as the control, scale numbers should increase from left to right, and a clockwise turn should increase the setting. Unfortunately, all three requirements can't be satisfied.

25 ISE 412 Rotary controls and rotary displays (cont.) C.Rotary controls and linear displays in the same plane controls can be placed above, below, left or right of the display with fixed-scale linear displays. 1. Warricks' principle (only applies when the control is located to the side of the display) 2. Scale-by-side-principle (applies to top and bottom control locations as well as to the side)

26 ISE 412 Rotary controls and rotary displays (cont.) D.Clock-wise for increase – clock-wise movement of a rotary control will cause an increase in the value on the display irrespective of control display relations. E.Clock-wise - away and Counter-clock-wise - near clock-wise rotation suggests movement away from a person and counter-clock-wise rotation suggests movement towards the person.

27 ISE 412 Movements of displays and controls in different planes  relationships tend to be orthogonal.  Generally moving the control up and moving up on the display is superior to moving the control up and moving down on the display.  There's less difference between moving the control forward to move the display up and moving the control forward to move the display down. Rotary and stick-type controls and linear displays  several options, mostly following those recommendations for “in the same plane”