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Controls

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  1. Controls Rebecca W. Boren, Ph.D. IEE 437/547 Introduction to Human Factors Engineering Arizona State University October 24, 2011

  2. Controls Think of as many control devices as you can and write them down.

  3. Cameras Remote Controls

  4. 1950 Zenith Remote Ad http://www.tvhistory.tv/Remote%20Controls.htm

  5. Computer Input Devices Mouse Joystick Wii Keyboard DataHand

  6. Automobile Controls The one on the right is all hand operated.

  7. Simple? Designing for visibility means that just by looking, users can see the possibilities for action. Visibility is often violated in order to make things "look good“.

  8. Complex? Submarine controls Multi head Shower

  9. Onscreen Computer Controls

  10. Onscreen Computer Control or the Real Deal?

  11. What do these control?

  12. Controls • Display is the perception. • Seeing, hearing, or other sense • Control is the action after a decision is made. • Involves the selection and execution of responses. • Includes the feedback loop.

  13. Model of Human Processing

  14. Principles of Response Selection

  15. Decision complexity • The speed with which an action can be selected is strongly influenced by the number of possible alternative actions that could be selected.

  16. Decision complexity • Hick-Hyman Law of reaction time shows a logarithmic increase in reaction time (RT) as the number of possible stimulus-response alternatives (N) increases.Humans process information at a constant rate. RT = a + bLog2N

  17. Hick-Hyman Law

  18. The most efficient way to deliver a given amount of information is by a smaller number of complex decisions rather than a large number of simple decisions. An example is typing versus Morse code.

  19. Response expectancy • We perceive rapidly and accurately that information that we expect. • We don’t expect a car to suddenly pull in front of us on the freeway. It takes time to perceive and to respond.

  20. Response expectancy • We use the yellow caution light to help us anticipate a red light.

  21. Compatibility • Good stimulus-response compatibility (display-control compatibility) aids in response selection. • Two sub principles: • Location compatibility (mapping) • Movement compatibility (moving a lever right should move the display to the right).

  22. Location Compatibility

  23. Location Compatibility

  24. Location Compatibility

  25. Movement Compatibility

  26. How do I turn this computer on? Usability and Human Factors Web Workshop series at Monash University

  27. How do I turn this computer on? • About 4 or 5 years ago I'd just started a new job • I had a choice of using a fairly new Macintosh or a rather old PC - I wanted to use the Mac • I'd never used a Mac before • And I couldn't figure out where the "ON" switch was • After messing around for a long time, I accidentally turned it on after randomly pressing a whole bunch of keys on the keyboard • I still didn't know how I'd done it, so I turned it off and tried the keys again until I realized it was the Apple key that brought the machine to life

  28. Speed-accuracy tradeoff • Sometimes positively correlated, sometimes negatively correlated. • The first three principles result in a positive correlation. Whatever makes the response selection faster makes it less prone to error.

  29. Principles of Speed-accuracy tradeoff • Good stimulus-response compatibility (display-control compatibility) aids in response selection. • Location compatibility (mapping) • Movement compatibility (moving a lever right should move the display to the right).

  30. Speed-accuracy tradeoff • In a few cases, control devices differ in the speed-accuracy tradeoff because one induces faster, but less precise behavior or more careful but slower behavior (2nd order).

  31. Feedback • Instantaneous or nearly instantaneous feedback is helpful. • If there is a lag of even 100 msec, an unskilled operator will have difficulty. • What kinds of feedback are helpful? Name some.

  32. Discrete Control Activation • Physical feel. There should be some feedback as to state change: a click, beep, flashing light, change of color, etc. • Feedback lights should be redundant with another signal and should be immediate.

  33. Discrete Control Activation A toggle switch provides visual feedback, an auditory click, and a tactile snap with the sudden loss of resistance.

  34. Discrete Control Activation • Size. Smaller keys are difficult for humans. In relationship to the size of large hands, it is easy to make mistakes by pressing the wrong key or two keys at once.

  35. Discrete Control Activation • Confusing labeling. Key press or control activation errors also occur if the identity of a key or control is not well marked for novice users.

  36. Discrete Control Activation • Well-labeled controls.

  37. Positioning Control Device • A common human-machine task is to position an entity in space. • The positioning or pointing task is defined as “movement of a controlled entity, called a cursor, to a destination, called the target.”

  38. Positioning Task • Movement of a controlled entity, called a cursor, to a destination, called the target. target cursor

  39. Positioning Control Device • Movement time: controls typically require two different movements: • movement of the hand or fingers to the control device • movement of the control device in some direction.

  40. Movement Time • Predicted by Fitts’ Law MT = a + b log2(2A/W) • MT is movement time • A is amplitude (distance) of the movement • W is width of the target (corresponds to accuracy) • log2(2A/W) is the index of difficulty (ID) • a and b are constants • MT is proportional to the index of difficulty

  41. Movement Time – Fitts’ Law MT = a + b log2(2A/W)

  42. Fitts’ Reciprocal Tapping Task

  43. Movement Time Examples • If the keys on a keyboard are made smaller, without the space also made proportionally smaller, then movement is more difficult. • Foot reaching a foot pedal • Assembly and manipulation under a microscope.

  44. Device Characteristics • Direct position controls: Light pen and touch screen • Indirect position controls: Mouse, touch pad, and touch tablet. • Indirect velocity controls: Joystick and cursor keys

  45. Direct Position Controls • Light pen and touch screen using a stylus or finger on a tablet. • Position of the human hand or finger directly corresponds to the desired location of the cursor.

  46. Direct Position Controls • Light pen and touch screen using a stylus or finger on a tablet. • Position of the human hand or finger directly corresponds to the desired location of the cursor.

  47. Indirect Position Controls • Mouse, touch pad, and touch tablet. • Changes in the position of the limb directly correspond to changes in the position of the cursor, but on a different surface.

  48. Indirect Position Controls • Mouse, touch pad, and touch tablet. • Changes in the position of the limb directly correspond to changes in the position of the cursor, but on a different surface.

  49. Indirect Velocity Controls • Joystick and cursor keys. • An activation of control in a given direction yields a velocity of cursor movement in that direction. For cursor keys the operator may repeat or hold down.