Adaptive control system having hedge unit and related apparatus and methods

• US 6,618,631 B1
• Filed: 05/31/2000
• Issued: 09/09/2003
• Est. Priority Date: 04/25/2000
• Status: Expired due to Term

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Johnson, Eric Norman, Calise, Anthony J.
• Primary Examiner(s): Follansbee, John
• Assistant Examiner(s): PHAM, THOMAS K
• Application Number:
  US09/585,106
• Time in Patent Office: 1,196 Days
• Field of Search: 700/28, 700/29, 700/30, 700/31, 700/32, 700/47, 700/48, 700/173, 701/58, 701/59, 701/60, 701/63, 701/68
• US Class Current: 700/28
• CPC Class Codes: G05B 13/027 using neural networks only
• CPC Class Codes: G05B 13/04 involving the use of models or simulators
• CPC Class Codes: G05B 13/041 in which a variable is automatically adjusted to optimise the performance

Abstract

The invention includes an adaptive control system used to control a plant. The adaptive control system includes a hedge unit that receives at least one control signal and a plant state signal. The hedge unit generates a hedge signal based on the control signal, the plant state signal, and a hedge model including a first model having one or more characteristics to which the adaptive control system is not to adapt, and a second model not having the characteristic(s) to which the adaptive control system is not to adapt. The hedge signal is used in the adaptive control system to remove the effect of the characteristic from a signal supplied to an adaptation law unit of the adaptive control system so that the adaptive control system does not adapt to the characteristic in controlling the plant.

Claims

1. A method executed by an adaptive control system, the method comprising the steps of:

a) generating an input control signal based on at least one of a reference model state signal, a commanded state signal, a plant state signal, and an adaptive control signal;

b) generating a command control signal based on at least one of a commanded state signal, a plant state signal, an adaptive control signal, and further based on control allocation and a control characteristic of a controller used to generate the command control signal;

c) supplying the command control signal to an actuator;

d) controlling a state of the plant based on the command control signal;

e) sensing a state of the plant;

f) generating a plant state signal based on the sensing of the step (e);

g) generating a first signal based on the input control signal, the plant state signal, and a plant model without a plant characteristic for which the adaptive control system is not to adapt;

h) generating a second signal based on the command control signal, the plant state signal, and a plant model with the plant characteristic for which the adaptive control system is to adapt;

i) generating a hedge signal by differencing the first and second signals;

j) generating a reference model state signal by modifying the commanded state signal with the hedge signal to include the effect of the control allocation and control characteristic on plant state from the reference model state signal;

k) comparing the plant state signal and the reference model state signal;

l) generating a tracking error signal based on the comparing of the step (k); and

m) generating the adaptive control signal based on the tracking error signal.

2. A method as claimed in claim 1 further comprising the step of:

n) generating the reference model signal based on the commanded state signal, the hedge signal, and a reference model representing the target response of the plant, the reference model signal used in the step (a) to generate the input control signal.

3. A method as claimed in claim 1 further comprising the step of:

n) generating the reference model signal based on the commanded state signal, the hedge signal, and a reference model representing the target response of the plant, the reference model signal used in the step (b) to generate the command control signal.

4. A method as claimed in claim 1 further comprising the step of:

n) generating a linear control signal based on the tracking error signal;

o) generating a reference model signal based on the commanded state signal, the hedge signal, and a reference model; and

p) generating a pseudo-control signal based on the linear control signal, the reference model signal, and the adaptive control signal, the pseudo-control signal used in the generation of the adaptive control signal in the step (m).

5. A method as claimed in claim 1 further comprising the step of:

n) generating the commanded state signal based on a control action from an operator.

6. A method as claimed in claim 1 further comprising the step of:

n) generating the commanded state signal based on a signal generated by an operator that is a computer.

7. A method as claimed in claim 1 further comprising the step of

n) generating a display for an operator based on the input control signal, the operator generating the command control signal based on the display.

8. A method as claimed in claim 1 wherein the plant is an aircraft and/or spacecraft.

9. A method as claimed in claim 1 wherein the plant is an automobile.

10. A method as claimed in claim 1 wherein the plant is an unmanned vehicle.

11. A method as claimed in claim 4 wherein the adaptive control signal is generated in the step (m) based on the plant state signal, the step (m) performed by a neural network having connection weights adjusted based on the tracking error signal and the pseudo-control signal, the neural network mapping the plant state signal to the adaptive control signal in the performance of the step (m).

12. A method as claimed in claim 4 wherein the plant state signal is used in the step (m) to generate the adaptive control signal.

13. A method as claimed in claim 5 wherein the operator is human, the method further comprising the step of:

o) generating a display based on the plant state signal, the display used by the operator to generate the commanded state signal in the step (n).

14. An adaptive control system coupled to receive a command state signal indicative of a target state of a plant controlled by the adaptive control system, the adaptive control system comprising:

a controller coupled to receive the commanded state signal, a plant state signal, and an adaptive control signal, the controller generating an input command signal based on the commanded state signal, the plant state signal, the adaptive control signal, and a control model, and the controller generating a command control signal based on the commanded state signal, the plant state signal, the adaptive control signal, the control model, control allocation of the controller, and at least one control characteristic of the controller, the controller coupled to supply the command control signal to the plant to control the plant'"'"'s state;

an actuator coupled to receive the command control signal, and affecting physical control of the plant'"'"'s state based on the command control signal;

a sensor coupled to sense the plant state, and generating a plant state signal based on the sensed plant state;

a hedge unit coupled to receive the input control signal, the command control signal, and the plant state signal, and generating a hedge signal to modify the command state signal based on the input control signal, the command control signal, the plant state signal, and a hedge model indicative of a characteristic of at least one of the plant and the adaptive control system, to remove the effect of the characteristic on a tracking error signal;

a reference model unit coupled to receive the command state signal and the hedge signal, the reference model unit generating a reference model state signal based on the commanded state signal and a hedge signal;

a comparator unit coupled to receive the reference model state signal and the plant state signal, and generating a tracking error signal based on a difference between the plant state signal and the reference model state signal; and

an adaptation law unit coupled to receive the tracking error signal, and generating the adaptive control signal based on the tracking error signal, the adaptation law unit coupled to supply the adaptive control signal to the controller.

15. An adaptive control system as claimed in claim 14 wherein the controller generates the input control signal and the command control signal further based on the reference model state signal.

16. An adaptive control system as claimed in claim 14 wherein the characteristic is a time delay between generation of the commanded state signal by the controller at a time;

and receipt by the controller of the plant state signal resulting from the commanded state signal generated at the time.

17. An adaptive control system as claimed in claim 14 wherein the characteristic is a time delay between generation of a state by the plant in response to the command control signal, and sensing of the state of the plant resulting from the command control signal.

18. An adaptive control system as claimed in claim 14 wherein the characteristic pertains to a control limit of the actuator used to control the plant.

19. An adaptive control system as claimed in claim 14 wherein the commanded state signal is generated by an operator, the adaptive control system further comprising:

an operator interface unit coupled to receive the plant state signal, the operator interface unit relaying the plant state to the operator; and

a command unit operable by the operator, and generating the command state signal based on the operator'"'"'s control action.

20. An adaptive control system as claimed in claim 14 wherein the operator interface is a display generated based on the plant state signal, and the operator is a human being that generates the control action to the command unit to generate the commanded state signal.

21. An adaptive control system as claimed in claim 14 wherein the commanded state signal is generated by a machine operator based on the plant state signal.

22. An adaptive control system as claimed in claim 14 wherein the adaptation law unit comprises a neural network having connection weights determined by the tracking error signal, the neural network mapping the plant state signal to the adaptive control signal based on the connection weights to generate the adaptive control signal.

23. An adaptive control system as claimed in claim 14 wherein the controller includes a dynamic inversion unit to generate the command control signal.

24. An adaptive control system as claimed in claim 14 wherein the input control signal is used to generate a display, and the operator generates a command control signal based on the display.

25. An adaptive control system as claimed in claim 14 wherein the plant is an aircraft and/or spacecraft.

26. An adaptive control system as claimed in claim 14 wherein the plant is an automobile.

27. An adaptive control system as claimed in claim 14 wherein the plant is an unmanned vehicle positioned remotely from the operator.

28. An adaptive control system as claimed in claim 18 wherein the control limit pertains to actuator end points.

29. An adaptive control system as claimed in claim 18 wherein the control limit pertains to actuator dynamics.

30. An adaptive control system as claimed in claim 18 wherein the control limit pertains to a rate limit of the actuator.

31. An adaptive control system as claimed in claim 18 wherein the control limit pertains to quantization effects of the actuator.

32. An adaptive control system as claimed in claim 22 wherein the controller generates a pseudo-control signal based on the commanded state signal and the plant state signal, the controller coupled to supply the pseudo-control signal to the neural network to adjust the connection weights of the neural network.