SYSTEMS AND METHODS FOR DERIVATIVE-FREE OUTPUT FEEDBACK ADAPTIVE CONTROL

• US 20120265367A1
• Filed: 04/12/2012
• Published: 10/18/2012
• Est. Priority Date: 04/12/2011
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Calise, Anthony J., Yucelen, Tansel, Kim, Kilsoo
• Granted Patent: US 8,996,195 B2
• Time in Patent Office: Days
• US Class Current: 701/1
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

An adaptive control system is disclosed. The control system can control uncertain dynamic systems. The control system can employ one or more derivative-free adaptive control architectures. The control system can further employ one or more derivative-free weight update laws. The derivative-free weight update laws can comprise a time-varying estimate of an ideal vector of weights. The control system of the present invention can therefore quickly stabilize systems that undergo sudden changes in dynamics, caused by, for example, sudden changes in weight. Embodiments of the present invention can also provide a less complex control system than existing adaptive control systems. The control system can control aircraft and other dynamic systems, such as, for example, those with non-minimum phase dynamics.

Claims

1. An adaptive control system for controlling a vehicle, the adaptive control system comprising:

a state observer configured to receive a sensed quantity from the vehicle, the state observer further configured to output a state estimate based at least in part on the sensed quantity; and

a controller configured to receive the state estimate and employ the state estimate in a derivative-free adaptive control law to calculate an adaptive control, the derivative-free adaptive control law based at least in part on a derivative-free weight update law, the controller further configured to produce a control command that is an input to a control system of the vehicle;

wherein at least a component of the control command is the adaptive control; and

wherein the derivative-free weight update law comprises a time-varying estimate of an ideal vector of weights.

2. The adaptive control system of claim 1, wherein the derivative-free weight update law further comprises a first gain, the first gain providing a parameter dependent Riccati equation with a positive definite solution.

3. The adaptive control system of claim 2, wherein a parameter other than the first gain of the parameter dependent Riccati equation restricts the values of the first gain for which the parameter dependent Riccati equation has a position definite solution.

4. The adaptive control system of claim 1,

wherein the control command further comprises a nominal control from the control system of the vehicle, the nominal control comprising a first gain;

wherein the adaptive control is added to the nominal control; and

wherein the first gain of the nominal control is not modified by the adaptive control.

5. The adaptive control system of claim 4, wherein the nominal control comprises a first gain and a second gain, and either the first gain, the second gain, or both are employed by the state observer.

6. The adaptive control system of claim 1, wherein the adaptive control comprises a weight estimate and a basis function;

and

wherein the weight estimate is obtained from the derivative-free weight update law.

7. A method for adaptive control of an uncertain system, the method comprising:

providing a first control command as an input to the uncertain system, the first control command comprising a first adaptive control;

receiving at least one sensed quantity from the uncertain system by a state observer;

outputting a state estimate from the state observer;

employing the state estimate in a derivative-free adaptive control law to calculate a second adaptive control, the derivative-free adaptive control law comprising a derivative-free weight update law; and

providing a second control command as an input to the uncertain system, the second control command comprising the second adaptive control;

wherein the derivative-free weight update law comprises a time-varying estimate of an ideal vector of weights.

8. The method for adaptive control of claim 7, wherein the derivative-free weight update law further comprises a first gain, the first gain selected to provide a parameter dependent Riccati equation with a positive definite solution.

9. The method for adaptive control of claim 8, wherein a parameter of the parameter dependent Riccati equation restricts the values of the first gain for which the parameter dependent Riccati equation has a positive definite solution.

10. The method for adaptive control of claim 7, wherein a weight estimate and a basis function are multiplied together to yield the second adaptive control, the weight estimate obtained from the derivative-free weight update law.

11. The method for adaptive control of claim 10, wherein the weight estimate is a function of continuous time.

12. The method for adaptive control of claim 10, wherein the weight estimate is a function of discrete time.

13. The method for adaptive control of claim 7, wherein the second control command comprises the second adaptive control added to a nominal control.

14. The method for adaptive control of claim 13, wherein the nominal control comprises a gain, and the gain is not modified by the adaptive control.

15. The method for adaptive control of claim 7, wherein the uncertain system is a non-minimum phase system.

16. An adaptive control system for controlling a vehicle, the adaptive control system comprising:

a reference model configured to output a state estimate; and

a controller configured to receive the state estimate and employ the state estimate in a derivative-free adaptive control law to calculate an adaptive control, the derivative-free adaptive control law based at least in part on a derivative-free weight update law, the controller further configured to produce a control command that is an input to a control system of the vehicle;

wherein at least a component of the control command is the adaptive control; and

wherein the derivative-free weight update law comprises a time-varying estimate of an ideal vector of weights.

17. The adaptive control system of claim 16, wherein the derivative-free weight update law further comprises a first gain, the first gain providing a parameter dependent Riccati equation with a positive definite solution.

18. The adaptive control system of claim 17, wherein a parameter other than the first gain of the parameter dependent Riccati equation restricts the values of the first gain for which the parameter dependent Riccati equation has a position definite solution.

19. The adaptive control system of claim 16,

wherein the control command further comprises a nominal control from the control system of the vehicle, the nominal control comprising a first gain;

wherein the adaptive control is added to the nominal control; and

wherein the first gain of the nominal control is not modified by the adaptive control.

20. The adaptive control system of claim 16, wherein the adaptive control comprises a weight estimate and a basis function, the weight estimate obtained from the derivative-free weight update law.