Adaptation to unmeasured variables

• US 6,404,581 B1
• Filed: 10/04/2000
• Issued: 06/11/2002
• Est. Priority Date: 01/08/1999
• Status: Expired due to Fees

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Voyan Technology Incorporated (Plantronics, Inc.)
• Inventors: Shah, Sunil C.
• Primary Examiner(s): Sniezek, Andrew L.
• Application Number:
  US09/680,128
• Time in Patent Office: 615 Days
• Field of Search: 360/75, 360/61, 360/77.04, 360/78.04, 360/78.09, 360/77.02, 700/2, 700/8, 700/18, 700/20, 700/29
• US Class Current: 360/75
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: G11B 20/00 Signal processing not specific to the method of recording or reproducing; Circuits therefor

Abstract

A scheme for management of uncertainty in control systems that require adaptation is described. The scheme removes as much uncertainty as possible at design time and manufacturing time by taking advantage of available compute resources in pre-computing a large set of robustness-performance tradeoff based model controllers at different operating conditions for different values of uncertainty parameters that occur in-use and in manufacturing. A group of control models, and corresponding model controllers with an uncertainty bound larger than the best-tuned controller, are generated. A subset of the model controllers is implemented in the system at manufacturing time based on characterization of the system. The subset of model controllers is switched at run time based on transient information received during operation of the system.

Claims

1. A disk drive system, comprising:

a head assembly; and

a servo controller coupled to the head assembly, the servo controller comprising;

a plurality of model controllers, each of the plurality of model controllers coupled to receive a plurality of head position sensor signals, each of the plurality of model controllers to generate a control signal; and

a data evaluator coupled to receive the plurality of head position sensor signals and generate an output, the data evaluator to determine when sufficient information from the plurality of head position sensor signals is received, the data evaluator coupled to select the control signal of one of the plurality of model controllers based on the output of the data evaluator.

2. The disk drive system of claim 1, wherein the data evaluator comprises a model hypothesis tester and test confidence indicator.

3. The disk drive system of claim 2, wherein the output is a model index.

4. The disk drive system of claim 3, wherein the servo controller further comprises:

a fall-back controller coupled to receive the plurality of head position sensor signals, the fall-back controller generating the control signal and wherein the model hypothesis tester and test confidence indicator is coupled to select the control signal of the fall-back controller when insufficient information from the plurality of head position sensor signals is received; and

a controller selector coupled to receive the model index, the controller selector coupled to receive the control signal of each of the plurality of model controllers and the fall-back controller, the controller selector to output the control signal of one of the plurality of model controllers based on the model index.

5. The disk drive system of claim 4, wherein the control signal is a voice coil motor current.

6. The disk drive system of claim 4, wherein the control signal is an actuator voltage.

7. A method of handling disk drive variations, comprising:

receiving a plurality of position sensor signals by a servo controller, the plurality of position sensor signals having a range of a factor;

evaluating the plurality of position sensor signals to determine when sufficient information of the plurality of position sensor signals is received; and

selecting one of a plurality of model controllers within the servo controller based on the factor.

8. The method of claim 7, wherein evaluating comprises performing a generalized likelihood ratio test on the plurality of position sensor signals to determine when there is a high confidence in the plurality of position sensor signals received by the servo controller.

9. The method of claim 8, further comprising:

receiving a control signal by the servo controller, each of the plurality of the model controllers having adaptive parameters affecting the received control signal; and

gradually adjusting the adaptive parameters of the selected one of the plurality of model controllers.

10. The method of claim 7, wherein the factor is resonance.

11. The method of claim 7, wherein the factor is disturbance.

12. The method of claim 11, wherein the factor is environment.

13. A disk drive, comprising:

means for receiving a plurality of position sensor signals by a servo controller, the plurality of position sensor signals having a range of a factor;

means for evaluating the plurality of position sensor signals to determine when sufficient information of the plurality of position sensor signals is received; and

means for selecting one of a plurality of model controllers within the servo controller based on the factor.

14. The disk drive of claim 13, wherein the means for evaluating comprises performing a generalized likelihood ratio test on the plurality of position sensor signals to determine when there is a high confidence in the plurality of position sensor signals received by the servo controller.

15. The disk drive of claim 14, further comprising:

means for receiving a control signal by the servo controller, each of the plurality of the model controllers have adaptive parameters affecting the received control signal; and

means for gradually adjusting the adaptive parameters of the selected one of the plurality of model controllers.

16. The disk drive of claim 13, wherein the factor is resonance.

17. A machine readable medium having stored thereon instructions, which when executed by a processor cause the processor to perform the following:

receiving a plurality of position sensor signals by a servo controller, the plurality of position sensor signals having a range of a factor;

evaluating the plurality of position sensor signals to determine when sufficient information of the plurality of position sensor signals is received; and

selecting one of a plurality of model controllers within the servo controller based on the factor.

18. The machine readable medium of claim 17, wherein evaluating comprises performing a generalized likelihood ratio test on the plurality of position sensor signals to determine when there is a high confidence in the plurality of position sensor signals received by the servo controller.

19. The machine readable medium of claim 18, wherein the processor further performs:

receiving a control signal by the servo controller, each of the plurality of the model controllers having adaptive parameters affecting the received control signal; and

gradually adjusting the adaptive parameters of the selected one of the plurality of model controllers.

20. The machine readable medium of claim 17, wherein the factor is resonance.

21. The machine readable medium of claim 17, wherein the factor is disturbance.