1. 고려대학교 산업공학과 IND641 Engineering Psychology Chapter 10. Manual Control  OVERVIEW  the analog form or the time-space trajectory of the response – the domain of continuous control  human performance in manual control  skills approach  primarily involves analog motor behavior, in which the operator must produce or reproduce a movement pattern from memory with little environmental uncertainty  with little environmental uncertainty, skills in theory may be performed perfectly and identically from trial to trial  open-loop control because once the skill has developed there is little need to process the visual feedback from the response  focuses on skill acquisition and practice  dynamic systems  examines human abilities in controlling or tracking dynamic system to conform with certain time-space trajectories in the face of environmental uncertainty  because of the need to process error signals  closed-loop control  focuses on mathematical representations of the human’s analog response when processing uncertainty  generally addresses the behavior of the well-trained operator

2. 고려대학교 산업공학과 IND641 Engineering Psychology  OPEN-LOOP MOTOR SKILLS  Discrete Movement Time  Fitts’ Law  when movement amplitude (A) and target width (W) were varied, their joint effects were summarized by a simple equation (Fig 10.1; Fig 10.2):Fig 10.1Fig 10.2  speed-accuracy trade-off in movement: movement time and accuracy reciprocally related  index of difficulty (ID) of the movement  higher b indicates less efficient movements, “a” reflects the start-up time for a movement  Models of Discrete Movement  typical trajectory or time history as the stylus approaches the target (speed-accuracy tradeoff) 1.an exponential approach to the target with an initial high-velocity approach(initial ballistic) followed by a smooth, final, homing phase (current control) 2.velocity profile  control is not continuous but discrete corrections, acceleration and deceleration  feedback processing assumption (Fig 10.3) – sample-and-correct process until the target boundary is crossed – closed loop behavior -- generally exponential approachFig 10.3  Motor Schema  with highly learned skills under minimal environmental uncertainty, visual feedback is not necessary  open-loop fashion  visual feedback may be harmful

3. 고려대학교 산업공학과 IND641 Engineering Psychology  general characteristics of well-learned motor skills 1.they may well depend on feedback, but the feedback is proprioceptive 2.the patterns of desired muscular innervation may be stored centrally in LTM and executed as an open-loop motor program without visual feedback correction or guidance  motor program and motor schema  highly overlearned skills that do not depend on guidance from visual feedback  low attention demand, single-response selection, and consistency of outcome  Low Attention Demand  the motor program tends to be automated  Single-Response Selection  single-response selection required to activate or “load” a single motor program even with a number of separate, discrete responses  resources are demanded only once, at the point of initiation, when the program is selected  Consistency of Outcome: Programs Versus Schemata  a motor program is assumed to generate very consistent space-time trajectories from one replication to another  what is consistent is not the process of muscular innervation but the product of response  signature of one’s name meets the criteria of motor program  certain characteristics of the time-space trajectories remained invariant  whatever is learned and stored in LTM cannot be a specific set of muscle commands but must represent a more generic or general set of specifications of how to reach the desired goal – motor schema  once a schema is selected, the process of loading requires the specific instance parameters to be specified to meet the immediate goals at hand

4. 고려대학교 산업공학과 IND641 Engineering Psychology  TRACKING OF DYNAMIC SYSTEMS  when describing human operator control of physical systems, research moves from the domain of perceptual motor skills and motor behavior to the more engineering domain of tracking  this shift in domain from three nonhuman elements on the performance 1.the dynamics of the system itself 2.the input to the operator 3.the display  The Tracking Loop: Basic Elements (Fig 10.4)Fig 10.4  control dynamic – the relationship between the force, f(t), applied and the steering wheel movement, u(t)  system dynamic – the relationship between control position, u(t) and system response, o(t)  error sources 1.command inputs, i c (t) – changes in the target to be tracked 2.disturbance inputs, i d (t) – applied directly to the system  input (Fig 10.5) – may be transient or continuous (predictable, periodic, random)Fig 10.5  display – the source of all information necessary to implement the corrective response  pursuit display – independent movement of both the target and the cursor  compensatory display – only movement of the error relative to a fixed 0-error reference  tracking performance in terms of error

5. 고려대학교 산업공학과 IND641 Engineering Psychology  Transfer Functions  the mathematical relationship between the input and the output of a system (Fig 10.6)Fig 10.6  Pure Gain -- (the output)/(the input) -- low-gain system – sluggish  Pure Time Delay – transmission lag  delays the input but reproduce it in identical form T seconds later  no effect on gain, nor does gain have any effect on time delay  Experimental Lag  gradually “home in” or stabilize on the target input  defined by time constant T i : the time the output reach 63 % of its final value  Velocity-Control, Integrator, or First-Order System  constant velocity, time integral of the output  closely related to exponential lag  Acceleration-Control, Double-Integrator, or Second-Order System  combines two integrators in series – constant acceleration  unstable, or difficult to control – inertia  Differentiator  minus-first-order: produce an output position of a value equal to the rate of change of the input  theoretically step response is a “spike”  Frequency-Domain Response

6. 고려대학교 산업공학과 IND641 Engineering Psychology  Human Operator Limits in Tracking  Processing Time  effective time delay – perceived error translated by operator after a lag  zero and first-order system – 150 to 300 msec: second-order – 400 to 500 msec  time delays due to human processing or system lag are harmful to tracking (Fig 10.7)Fig 10.7 1.any lag will cause output to no longer line up with input 2.with periodic or random inputs, delay produce instability, oscillatory behavior  Bandwidth  tracking involves the transmission of information – common or disturbance-induces error  the limit of information transmission in tracking is between 4 to 10 bits/sec (preview)  frequency limit determines the maximum bandwidth of random inputs -- 0.5 to 1.0 Hz  max. frequency with which corrections are exerted in tracking – 2times/sec  Prediction and Anticipation  must anticipate future errors on the basis of present values to make control correction after a considerable lag  Processing resources  difficulty in anticipation related to the resource demands of spatial working memory  mental model of the system’s dynamics  working memory  disrupted by concurrent tasks  Compatibility  tracking is primarily a spatial task -- spatial compatibility affects tracking performance

7. 고려대학교 산업공학과 IND641 Engineering Psychology  Effect of System Dynamics on Tracking Performance  Gain  U-shaped function of system gain (system output / control input)  intermediate gain – the lowest error and easiest to track  high gain  minimal control effort to produce large corrections  overcorrections and oscillations  instability resulted in lags in system  optimal gain – the crossover point of the instability at high gain and effort at low gain  Time Delay  pure time delay harmful in tracking  worse tacking performance with greater delays  System Order  zero-order and first order – roughly equivalent – successful tracking requires position and velocity to be matched (Fig 10.8); economy of movement and spaceFig 10.8  the orders above first – error and subjective workload increase dramatically  second order control – unequivocally worse  generating lead – higher order derivatives be perceived as a basis for correction  longer effective time delay  increased lag  respond smoothly  bang-bang – double impulse or time-optimal control – optimal control (Fig 10.9)Fig 10.9

8. 고려대학교 산업공학과 IND641 Engineering Psychology  Instability  oscillatory and unstable behavior  positive feedback systems  once an error is in existence, feedback works to add the error in the same direction  negative feedback systems  more typical  humans and systems function to reduce rather than increase detected error  high gain and long phase lag – instability  Tracking Displays  Preview  command input and system output determine the future error  the future input will be most accurately available when there is preview – it enables the operator to compensate for processing lags in the tracking loop  no preview – predict the future course of the input (Fig 10.10)Fig 10.10  precognition mode – the input is nonrandom or contains periodicities – easier prediction  Output Prediction and Quickening  output prediction – a combination of its present position and its higher derivatives  displays in which a computer estimates error derivatives and future position  predictive display (Fig 10.11; Fig 10.12)Fig 10.11Fig 10.12  accuracy of any prediction – sluggishness (inertia) of the system and the frequency of control or disturbance inputs

9. 고려대학교 산업공학과 IND641 Engineering Psychology  quickening – where the system error likely to be in the future if is not controlled --no indication of current error because current error provides no information that is useful for correction  Pursuit Versus Compensatory Displays  the goal of tracking – to match the output to the input, or minimize error  pursuit display – views the command input and the system output moving separately  generally superior performance to compensatory one for two major reasons -- ambiguity of compensatory information and the compatibility of pursuit displays  cannot distinguish among the three potential causes of error: command input, disturbance input, and the operator’s own incorrect control actions -- error is ambiguous and control is more difficult  a changing command input – advantage with greater S-R compatibility compensatory display  CONTROL DEVICES  the light pen, touch screen, trackball, mouse, cursor keys, or joysticks  implication of different control devices for simple positioning tasks, characterized by Fitts’s law  Manual Control  manual control devices – anthropometric and biomechanical factors  The Speed-Accuracy Trade-off  direct point devices (light pen or touch screen) -- very rapid but less accurate than indirect devices (mouse)  the slope of the Fitts’s law – the overall effectiveness of a control device, (lower, better)  the slope by the mouse – lower than other control devices

10. 고려대학교 산업공학과 IND641 Engineering Psychology  Control Order Compatibility  most control devices – displacement produce a constant displacement (zero-order) or constant rate of movement (first-order) of the cursors across the screen  only the light pen and touch screen must be zero-order controllers  natural “affinities” or “compatibilities” – mice for zero-order control dynamics, and joysticks for first-order control dynamics  mouse  best captures the natural eye-hand coordination  the optimal gain is between one and three – the cursor should travel between one and three times the distance traveled by the hand  if first-order control – abandons the natural eye-hand coordination and the zero- velocity resting place  spring-loaded joysticks  spring loading maximize proprioceptive and kinesthetic feedback  natural resting state by “snap back” – automatically recovered  problems as a zero-order device: the lack of precision with which any position off of the center can be maintained, lack of available movement range

11. 고려대학교 산업공학과 IND641 Engineering Psychology

12. 고려대학교 산업공학과 IND641 Engineering Psychology

13. 고려대학교 산업공학과 IND641 Engineering Psychology

14. 고려대학교 산업공학과 IND641 Engineering Psychology

15. 고려대학교 산업공학과 IND641 Engineering Psychology

16. 고려대학교 산업공학과 IND641 Engineering Psychology

17. 고려대학교 산업공학과 IND641 Engineering Psychology

18. 고려대학교 산업공학과 IND641 Engineering Psychology

19. 고려대학교 산업공학과 IND641 Engineering Psychology

20. 고려대학교 산업공학과 IND641 Engineering Psychology

21. 고려대학교 산업공학과 IND641 Engineering Psychology