Adaptive control system

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

a control system configured to generate drive signals for the plant in dependence upon a reference signal and an error signal;

a state observer or state sensor configured to generate an estimate of a state of the plant in dependence upon the reference signal;

an error combiner configured to selectably combine a first error signal determined from the reference signal and a set of measurements of the plant and a second error signal determined from the reference and the estimate so as to produce a third error signal which is provided as the error signal to the control system, wherein the error combiner is configured to pre-multiply the first error signal by a first gain and the second error signal by a second gain so as to obtain first and second amplified error signals respectively and to add the first and second amplified error signals to obtain the third error signal.

2. An adaptive control system according to claim 1 , wherein, in a first or second enhanced mode, the error combiner is configured to set the first and second gains to respective non-zero, positive values.

3. An adaptive control system according to claim 2 , wherein, in the first enhanced mode, the first and second gains are equal.

4. An adaptive control system according to claim 3 , wherein the first and second gains are equal to one.

5. An adaptive control system according to claim 2 , wherein, in the second mode, the first gain is equal to or greater than one, the second gain is equal to or greater than one, and the first gain and/or the second gain is greater than one.

6. An adaptive control system according to claim 1 , wherein the control system comprises a field-orientated control system which comprises a speed regulator.

7. An adaptive control system according to claim 1 , wherein the state observer or state sensor comprises a signal-based model reference adaptive control speed observer.

8. An adaptive control system according to claim 1 , wherein the first error is determined from a speed reference ω R and a plant speed ω P .

9. An adaptive control system according to claim 1 , wherein the second error is determined from a speed reference ω R and a speed estimate ω E .

10. An integrated circuit comprising:

an adaptive control system according to claim 1 .

11. An integrated circuit according to claim 10 , further comprising:

a CPU sub-system; and

a peripheral module configured to provide the adaptive control system.

12. An integrated circuit according to claim 10 , further comprising:

a CPU sub-system comprising at least one processor and memory;

wherein the CPU sub-system provides the adaptive control system.

13. An integrated circuit according to claim 10 , which is microcontroller.

14. A system comprising:

at least one plant; and

at least one adaptive control system according to claim 1 arranged to control operation of the at least one plant.

15. A vehicle comprising a system according to claim 14 .

16. A vehicle according to claim 14 , which is an aerial vehicle, such as an unmanned aerial vehicle.

17. A vehicle according to claim 14 , which is a ground vehicle, such as a motor vehicle.

18. An industrial system, such as a robot, comprising a system according to claim 14 .

19. An appliance, such as a domestic appliance, a heating, ventilation and air conditioning appliance or power tool, comprising a system according to claim 14 .

20. A system according to claim 14 , wherein the plant comprises a brushless DC motor, a permanent-magnet synchronous motor or an AC induction motor.

21. A method of controlling a plant, the method comprising:

generating drive signals for the plant in dependence upon a reference signal and an error signal; and

generating an estimate of a state of the plant in dependence upon the reference signal;

wherein generating the error signal comprises:

generating a first amplified error signal by multiplying a first error signal determined from the reference signal and a set of measurements of the plan by a first gain;

generating a second amplified error signal by multiplying a second error signal determined from the reference signal and the estimate by a second gain; and

adding the first and second amplified error signals.

22. A hardware circuit configured to perform a method according claim 21 .

23. A computer program product comprising a machine-readable medium storing thereon the computer program comprising instructions which, when executed by a computer, causes the computer to perform the method according to claim 21 .