16.400/453J Human Factors Engineering. Manual Control I

Transcription

1 J Human Factors Engineering Manual Control I 1

2 Levels of Control Human Operator Human Operator Human Operator Human Operator Human Operator Display Controller Display Controller Display Controller Display Controller Display Computer Computer Computer Computer Sensor Actuator Sensor Actuator Sensor Actuator Sensor Actuator Sensor Actuator Task Task Task Task Task Manual Control Supervisory Control Fully Automatic Control

3 Aircraft Basics 4

4 Control of Aircraft Forces on an A/C W Propulsive A Aerodynamic MT Gravitational Time (a) Control responses Stabilization Handling qualities Disturbance regulation Time (b) Maneuverability Reactive vs. proactive human response The innate human response to home in on a signal Distance Velocity

5 Pilot Input Actual pitch attitude θ Desired pitch attitude θ c Pitch attitude error θ e Digital flight control computer Cockpit inceptor Fly-by-wire Sensed aircraft motion Actuator Control effector 6

6 The Basic Pilot/Plant Feedback Loop What you want + - Display Pilot Sensor Airplane/ Plant Disturbance Input Where you are Pilot sees error state (i.e., not on altitude, heading, etc.) Pilot understands what must be done to correct for error Pilot corrects Airplane corrects 7 Sensed state is communicated to pilot

7 Some important definitions Pilot/operator never needs to respond as long as there is no error Two input types Command Disturbance Transient vs. continuous Continuous Periodic vs. random Can model these in the frequency domain A good assumption? Pursuit vs. compensatory displays Linear vs. non-linear Transfer function 8 Mathematical relationship between input and output

8 Transfer Function Interpretation (a) (b) Pure gain o(t) = ki(i) O = kl Pure time delay o(t) = i(t - τ) O = e-τsl These are for step response input why is this a good assumption? (c) τ T i Exponential lag O = l T i S + 1 Pure gain and pure time delay have no effect on each other 9

9 Transfer Function Interpretation, II Constantly held position produces constant rate of movement Input withdrawn, velocity =0, but new position is achieved (a) o(t) = O = l S i(t) dt First-order integral control; velocity control (b) o(t) = O = i(t) dt l S 2 Second-order acceleration control Typical pure 2 nd order systems are large mass/high inertia for constant input force Sluggish, unstable when tracked, &requires a series of reverse corrections

10 Transfer Function Interpretation, III 1 (c) Exponential lag l O = T i S + 1 T i First order response to error (as opposed to commanded input) will look like lag (response velocity is proportional to response error) (a) o(t) = O = l S i(t) dt First-order integral control; velocity control 11

11 Human Performance & System Order Human information processing causes a delay Perceptually humans track position, velocity, and acceleration changes the best (in that order) 0 th and 1 st order systems are tracked with time delays of ~ ms 2 nd order systems: ms Systems can cause delay Computationally Communication Best human can do is 2 corrections per second Serial reaction time experiments show people can make 2.5 decisions per second Countering inherent human delays with display 12 preview/prediction

12 Demo 13

13 Order and System Response Order Input Response to correct System response 0 1 Time 2 3 Position 14

14 System Order Design Considerations Which system order is best for humans? 0 th and 1 st equivalent Cost-benefit analysis (time vs. magnitude of response) Economy of movement & space Level of expertise Not mutually exclusive, rate aided displays are a combination 2 nd order and higher should be avoided Operators must perceive higher-error derivatives continuously Near-constant monitoring reduces cognitive capacity for other tasks 15 Error and subjective workload increase significantly

15 Stability Design Considerations Systems with intermediate gains have lowest error and easiest to track High gain = minimal effort but high likelihood of overshoot Instability exacerbated by system lags Finding the right gains PIO Caused by high gain & large lags/time delays in loop closure Inherent aspect of negative feedback systems High Good Unstable Oscillatory Acceptable Sluggish Low Long Short Time delay (τ) Gain (K)

16 Some PIO footage F-22 Gripen Shuttle mov 17

17 Predictive Interface Design Should control by error rates vs. error values When humans respond to predictive cues, they act as differentiator and cancel out an integrator (reducing order) Predictive displays can mitigate consequences of time delay Two types Preview Prediction Quickening where system error is likely to be in the future Issues with assumptions 18

18 Measuring Pilot Response B Vertical Speed (fpm) A C C RMSE ( Y Y ) 2 a d n Time (sec) Actual Desired +/- 10% Measuring signal strength as opposed to average values

19 Multi-axis Control Cross-coupled & hierarchical tasks Lower order variables must be controlled to regulate higher order variables Cognitive workload & design interventions (a) (b) (c) Steering wheel angle Aileron position (rate of roll) Rubber plane angle Inner Loop Bank angle Heading φ φ Pitch rate Pitch angle Depth 0 Heading δ Lateral position Outer Loop δ Lateral deviation

20 MIT OpenCourseWare / Human Factors Engineering Fall 2011 For information about citing these materials or our Terms of Use, visit: