Copyright Catherine M. Burns CONTROLS Text p. 218-242 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Control Model Controls enable an operator to take action A. action on the interface B. control signal to the machine C. action on the world 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Controls as Displays Controls must be visible and understandable. All guidance on information displays holds here as well. Controls are also displays: must be visible must be understandable what they control actions on them must be visible - give feedback! 05/12/2018 Copyright Catherine M. Burns

Exercise 1: Picking something for lunch With a partner, examine the following menus. Make a decision on what to order. 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Basic Principles Hick-Hyman Law: Reaction time increases logarithmically as number of possible responses increases (2 options faster than 8) (or RT is a linear function of log2(n), suggesting people process information at a constant rate) RT N 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Basic Principles Decision Complexity Advantage: But given same amount of information to transmit, smaller # of complex decisions is faster than more simple decisions Shallow menus faster than deep menus 05/12/2018 Copyright Catherine M. Burns

Resolving HH Law and Decision Complexity Advantage Given 1 message It will be faster to type it than to use Morse Code Fewer keystrokes, but each keystroke carries more information Morse Code keystrokes will be faster than typewriter keystrokes HH Law (2 choices vs 26) 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Basic Principles Response Expectancy: better select actions that are expected Compatibility: to mental model of the user and physical compatibility location compatibility (close to display) movement compatibility (congruent with feedback) 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Exercise 2 With a partner Draw a dot on a sheet of blank paper. Have your partner try to hit the dot 1. As many times as possible in 1 minute 2. As accurately as possible 10 times. Reverse roles. 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Exercise 3 With a partner Take a sheet of blank paper Draw a large circle on it and a small circle on it. Hold the paper arm’s length away from your partner. Have your partner touch the large circle 10 times, then the small circle 10 times Which is easier? 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Basic Principles Speed-Accuracy Trade-off: faster behaviour is generally less precise Fitts Law: MT = a + blog2(2A/W) where A = amplitude, W = target width (Further target or decreased size, increases MT) Feedback of control state: Can you tell when the control has been activated, or when the control signal has been sent? 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Fitts Law MT is proportional to 2A/W Log2(2A/W) is called the index of difficulty 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Software Controls Usually 2 controls (input device) and on screen “soft control” Input devices are highly task dependent. Touch screen not precise, parallax issues, but direct input, easy to understand, no peripheral (Table 9.1, 9.2, 9.3) Slide pad: Any comments? 05/12/2018 Copyright Catherine M. Burns

Continuous Control and Tracking following a moving target driving the most common example generally based on controlling the error signal e(t) 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Exercise 4 Finger Tracking exercise One partner is the leader the other the tracker. Then reverse roles. How do you make it difficult for your partner to follow you? 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Types of Control Zero order (Position x Control): position of control device = position of output. computer mouse, drawing a line, analog tuning 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Velocity Control First order (Velocity dx/dt Control): activation of control yields a velocity. Control must be moved back to stop movement.. car steering wheel Joystick Radio scan button (1 push sets up scan velocity, push to stop) Control needs to have a “neutral” point where response stops 05/12/2018 Copyright Catherine M. Burns

Second Order or Acceleration Control Spacecraft maneuvering Each input produces an acceleration Hard to control, sluggish and unstable 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Control Order Zero Order First Order Second Order 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Control Problems Time delays Gain Called “closed loop” or sometimes “negative feedback loop” instability 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Time delays People tend to over command Handling the lag requires anticipating the results of control movements People correct too rapidly, or to tiny deviations 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Gain Large system output to small input Gain=DO/DI Proper gain is somewhat task dependent High gain good for large changes High gain can cause overshooting and instability for small deviations 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns 05/12/2018 Copyright Catherine M. Burns

Controls on the Space Shuttle 05/12/2018 Copyright Catherine M. Burns

Death Star Gunner’s Helmet 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Lightsabers 05/12/2018 Copyright Catherine M. Burns

Darth Vader Control Accessibility? 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Close-up 05/12/2018 Copyright Catherine M. Burns

Copyright Catherine M. Burns Control – Finger match 05/12/2018 Copyright Catherine M. Burns