System and method for diagnosing a controller in a limited rotation motor system

1. A diagnostic system for analyzing a limited rotation motor system, said diagnostic system comprising:

first transform means for receiving a first digital signal that is representative of a motor control signal, and for providing a motor control frequency domain signal that is representative of a frequency domain representation of the motor control signal;

second transform means for receiving a second digital signal that is representative of a position detection signal, and for providing a position detection frequency domain signal that is representative of a frequency domain representation of the position detection signal;

closed loop frequency response means for identifying a representation of the frequency response of the limited rotation motor responsive to the motor control frequency domain signal and the position detection frequency domain signal; and

diagnostic means for comparing the representation of the frequency response with a previously recorded representation of a prior frequency response to identify an error condition with respect to the limited rotation motor system.

2. The system as claimed in claim 1 , wherein said first transform means and said second transform means each perform a Fast Fourier Transform.

3. The system as claimed in claim 1 , wherein said representation of the frequency response identified by the closed loop frequency response means includes a ratio of the position detection frequency domain signal and the motor control frequency domain signal.

4. The system as claimed in claim 3 , wherein said ratio is provided by the position detection frequency domain signal divided by the motor control frequency domain signal.

5. The system as claimed in claim 1 , wherein said diagnostic means compares a low frequency range of the frequency response with the prior frequency response.

6. The system as claimed in claim 5 , wherein said diagnostic means provides a failed bearing error signal that is indicative of whether a bearing is at risk of failing.

7. The system as claimed in claim 1 , wherein said diagnostic means compares a mid frequency range of the frequency response with the prior frequency response.

8. The system as claimed in claim 7 , wherein said diagnostic means provides a torque constant error signal that is indicative of a change in torque constant of the limited rotation motor.

9. The system as claimed in claim 1 , wherein said diagnostic means provides an asymmetry error signal that is indicative of whether the range of movement of a rotor shaft of the limited rotation motor is not symmetrical with respect to the torque constant.

10. The system as claimed in claim 1 , wherein said limited rotation motor system includes a proportional, integral, derivative controller.

11. The system as claimed in claim 10 , wherein said diagnostic means provides corrective signals to the proportional, integral, derivative controller.

12. A diagnostic system for analyzing a limited rotation motor system, said diagnostic system comprising:

first FFT means for receiving a first digital signal that is representative of a motor control signal, and for providing a motor control frequency domain sequence that is representative of a frequency domain representation of the motor control signal for a plurality of frequencies;

second FFT means for receiving a second digital signal that is representative of a position detection signal, and for providing a position detection frequency domain sequence that is representative of a frequency domain representation of the position detection signal for the plurality of frequencies;

closed loop frequency response means for identifying a representation of the frequency response for the plurality of frequencies of the limited rotation motor responsive to the motor control frequency domain signal and the position detection frequency domain signal; and

diagnostic means for comparing the representation of the frequency response with a previously recorded representation of a prior frequency response to identify an error condition with respect to the limited rotation motor system.

13. The system as claimed in claim 12 , wherein said representation of the frequency response identified by the closed loop frequency response means includes a ratio of the position detection frequency domain signal and the motor control frequency domain signal.

14. The system as claimed in claim 13 , wherein said ratio is provided by the position detection frequency domain signal divided by the motor control frequency domain signal.

15. The system as claimed in claim 12 , wherein said diagnostic means compares a low frequency range of the frequency response with the prior frequency response.

16. The system as claimed in claim 15 , wherein said diagnostic means provides a failed bearing error signal that is indicative of whether a bearing is at risk of failing.

17. The system as claimed in claim 12 , wherein said diagnostic means compares a mid frequency range of the frequency response with the prior frequency response.

18. The system as claimed in claim 17 , wherein said diagnostic means provides a torque constant error signal that is indicative of a change in torque constant of the limited rotation motor.

19. The system as claimed in claim 12 , wherein said diagnostic means provides an asymmetry error signal that is indicative of whether the range of movement of a rotor shaft of the limited rotation motor is not symmetrical with respect to the torque constant.

20. The system as claimed in claim 12 , wherein said limited rotation motor system includes a proportional, integral, derivative controller.

21. The system as claimed in claim 20 , wherein said diagnostic means provides corrective signals to the proportional, integral, derivative controller.