Control Chapter 9

Defining Control Chapter 6 (human information processing) – knowing the state of affairs, knowing what to do, and doing it. Control is the doing part of the process. It is both a noun and a verb (to control). In information processing, it involves the selection and execution of responses or the last two stages of the model. Chapter 6 (human information processing) – knowing the state of affairs, knowing what to do, and doing it. Control is the doing part of the process. It is both a noun and a verb (to control). In information processing, it involves the selection and execution of responses or the last two stages of the model.

Information Processing Model

Principles of Response Selection Decision Complexity – speed of action selection affected by complexity Decision Complexity – speed of action selection affected by complexity Response Expectancy – perceive rapidly & effectively info that we expect Response Expectancy – perceive rapidly & effectively info that we expect Compatibility – location & movement expectency Compatibility – location & movement expectency The Speed-Accuracy Tradeoff – not always positive correlation between speed & accuracy (e.g. severe time constraints) The Speed-Accuracy Tradeoff – not always positive correlation between speed & accuracy (e.g. severe time constraints) Feedback – visual, tactile, & auditory Feedback – visual, tactile, & auditory

Discrete Control Activation Physical Feel – feed back is positive feature of discrete controls (toggle switch state (visual), click (auditory), & snap (tactile). Physical Feel – feed back is positive feature of discrete controls (toggle switch state (visual), click (auditory), & snap (tactile). Size – size of keys/controls represents the trade-offs between available space and usability Size – size of keys/controls represents the trade-offs between available space and usability Confusion & Labeling – when controls are unlabeled or poorly labeled confusion results Confusion & Labeling – when controls are unlabeled or poorly labeled confusion results

Positioning Control Devices Movement time (figure 9.2) Movement time (figure 9.2) Device characteristics Device characteristics –Direct position (light pen, touch screen) –Indirect position (mouse, pad, tablet) –Indirect velocity (joy stick, arrow keys) Isotonic, isometric, spring loaded Isotonic, isometric, spring loaded –Gain control (sensitivity) Task performance dependence (figure 9.3) Task performance dependence (figure 9.3) The work space (table 9.3) The work space (table 9.3) The environment (figure 9.4) The environment (figure 9.4)

Verbal & Symbolic Input Devices Numerical Data Entry (figure 9.4) Numerical Data Entry (figure 9.4) Linguistic Data Entry Linguistic Data Entry –Type writer/keyboard –Direct writing input (technical challenges) –Chording keyboard (figure 9.5) Fast transcribing (court recorders) Fast transcribing (court recorders) Less fatigue and muscular/skeletal stress Less fatigue and muscular/skeletal stress Requires extensive learning Requires extensive learning

Voice Input Benefits Benefits –Natural communications channel –Advantageous in dual task situations (dialing cell phone while driving) –Allows dual input Costs Costs –Confusion & limited vocabulary –Speed constraints –Acoustic quality & noise/stress –Compatibility – less suitable for controlling continuous movement

Continuous Control & Tracking The tracking loop elements – standard, actual, difference, & corrective action

Continuous Control & Tracking (cont.) Input task – varies with frequency of corrective actions Input task – varies with frequency of corrective actions Control order Control order –Position (0 order control) –Velocity (1 st order control) –Acceleration (2 nd order control) Time delays & transport lags (e.g. controlling robot on mars) Time delays & transport lags (e.g. controlling robot on mars)

PROPORTIONAL CONTROL Magnitude of correctvie action is proportional to magnitude of “error” C P (t) = K P e(t) Old Set-Point New Set-Point Proportional Cont Action tapers off as process approaches new set-point but over shoots Time

DERIVATIVE CONTROL Old Set-Point New Set-Point Time Proportional & Integral Control are pushing the process down. Derivative Control is anticipating over- shoot & is pushing the process up.

INTEGRAL CONTROL Keeps history of the accumulated error and attempts to correct any imbalance Old Set-Point New Set-Point Time

Continuous Control & Tracking (cont.) Gain control (proportional to amount of correction required) Gain control (proportional to amount of correction required) Stability – instability is result of lags, gain to high, & human trying to correct too fast Stability – instability is result of lags, gain to high, & human trying to correct too fast Open- versus closed-loop systems Open- versus closed-loop systems –Previous discussion was closed-loop –Open loop would be when operator notes correction needed and simply puts switch to new position regardless of correction needed

Remote Manipulation or Telerobotics Time delay Time delay Depth perception & image quality - problem of accuracy in 3-D settings. Limited bandwidth may also affect image quality Depth perception & image quality - problem of accuracy in 3-D settings. Limited bandwidth may also affect image quality Proprioceptive feedback – Sense of tactile feedback to prevent crushing of fragile object being manipulated Proprioceptive feedback – Sense of tactile feedback to prevent crushing of fragile object being manipulated