Integrated diagnostics and control systems

• US 6,326,758 B1
• Filed: 12/15/1999
• Issued: 12/04/2001
• Est. Priority Date: 12/15/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Reliance Electric Technologies LLC (ABB Limited)
• Inventors: Discenzo, Frederick M.
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): SMITH, TYRONE W
• Application Number:
  US09/461,787
• Time in Patent Office: 720 Days
• Field of Search: 318/432, 318/463, 318/609, 318/610, 318/565, 388/906, 388/909
• US Class Current: 318/609
• CPC Class Codes: G05B 23/0243 model based detection method, e.g. first-principles knowledge model
• CPC Class Codes: G05B 23/0283 Predictive maintenance, e.g. involving the monitoring of a system and, based on the monitoring results, taking decisions on the maintenance schedule of the monitored system; Estimating remaining useful life [RUL] preventive maintenance, i.e. planning maintenance according to the available resources without monitoring the system G06Q10/06
• CPC Class Codes: G05B 23/0294 Optimizing process, e.g. process efficiency, product quality
• CPC Class Codes: Y10S 388/906 Proportional-integral system
• CPC Class Codes: Y10S 388/909 Monitoring means

Abstract

An integrated control and diagnostics system for a controlled system (e.g., a motor) includes a diagnostics module and a controller coupled to the motor. To optimize operation, the diagnostics information signal is used to modify the control provided by the controller as required. Moreover, the output of the control module is coupled to the diagnostics module so that the health assessment made by the diagnostics module can be based at least in part on the output of the controller. The invention uses a model-based diagnostics approach that allows integration of control algorithms with diagnostics algorithms to intelligently trade off optimizing performance to avert or accommodate failures, and to meet performance requirements in a wide range of applications.

Claims

1. A method of optimizing control and diagnostics operations performed on a controlled system, the method comprising:

providing a diagnostics module and a control module, wherein each module is integrated with the controlled system;

generating, with the control module, a control signal in response to feedback from the controlled system;

generating, with the diagnostics module and based on the control signal, a health assessment signal indicative of the health of the controlled system;

predicting (1) when a controlled system failure will occur, and (2) the cause of the controlled unit failure, wherein said predicting step is performed in response to said health assessment and control signals; and

determining whether to alter the control signal based on said predicting step.

2. The method according to claim 1, further comprising planning a change in the control signal in response to said determining step, and altering the control signal based on said planning step.

3. The method according to claim 2, further comprising determining, prior to said altering step, the stability of the controlled system in response to said planning step.

4. The method according to claim 3, further comprising activating the controller prior to said altering step.

5. The method according to claim 1, wherein the control signal is based on a process constraint associated with the controlled system.

6. The method according to claim 5, wherein the process constraint is an operational frequency to avoid.

7. The method according to claim 6, wherein the operational frequency to avoid is determined by the diagnostics module in response to feedback from the controlled system.

8. The method according to claim 1, wherein the feedback is generated by a sensor monitoring the controlled system.

9. A method of optimizing control and diagnostics operations performed on a motor, the method comprising:

providing a feedback control circuit and a diagnostics circuit, both of the circuits being integrated with the motor;

generating a health assessment signal with the diagnostics circuit, the health assessment signal being based on an output of the control feedback circuit;

generating a controller modification signal with the diagnostics circuit wherein the controller modification signal is based on the health assessment signal; and

generating a driving output with the feedback control circuit based on feedback from the motor and the controller modification signal.

10. The method according to claim 9, wherein the controller includes a velocity feedback loop and a torque feedback loop, wherein said velocity feedback loop generates a current command signal in response to the feedback from the motor, and said torque feedback loop generates the driving output in response to the current command signal.

11. The method according to claim 10, wherein the velocity feedback loop includes a sensor that is coupled to the motor, the sensor generating the feedback signal.

12. The method according to claim 11, wherein the feedback is indicative of a velocity of the motor.

13. The method according to claim 12, wherein said generating a health assessment signal step is performed by using a model associated with the motor, the model embedded in a memory of diagnostics circuit.

14. A method of optimizing the useful life of a motor according to a preventive maintenance schedule that includes a plurality of preventive maintenance checkpoints, the method comprising:

sensing a motor parameter during operation of the motor and generating a corresponding motor parameter signal;

generating, with a controller, a driving output based on the motor parameter signal;

diagnosing a health condition of the motor based on at least one of a group comprising (1) an operating objective, (2) the driving output, and (3) a process constraint;

predicting, based on the health condition, whether a motor fault condition will occur prior to the next preventive maintenance checkpoint; and

determining whether to alter the control signal in response to said predicting step.

15. The method according to claim 14, wherein the controller includes a velocity feedback circuit and a torque feedback circuit.

16. The method according to claim 15, wherein said torque feedback circuit includes a P-I controller and an inverter.

17. The method according to claim 16, wherein said diagnosing step is performed with a diagnostics module integrated with the motor.

18. The method according to claim 17, wherein said controller is integrated with the motor.

19. The method according to claim 14, wherein said diagnosing step is performed by using a model associated with the motor.

20. A method of optimizing the useful life of a motor according to a preventive maintenance schedule that includes a plurality of preventive maintenance checkpoints, the method comprising:

sensing a motor parameter during operation of the motor and generating a corresponding motor parameter signal;

generating, with a controller, a driving output based on the motor parameter signal;

diagnosing a health condition of the motor based on at least one of a group comprising (1) an operating objective, (2) the driving output, and (3) a process constraint;

predicting, based on the health condition, whether a motor fault condition will occur prior to the next preventive maintenance checkpoint; and

determining whether to alter the control signal in response to said predicting;

wherein the operating objective is operating the motor at 200% duty for a predetermined amount of time.

21. A method of optimizing the useful life of a motor according to a preventive maintenance schedule that includes a plurality of preventive maintenance checkpoints, the method comprising:

sensing a motor parameter during operation of the motor and generating a corresponding motor parameter signal;

generating, with a controller, a driving output based on the motor parameter signal;

diagnosing a health condition of the motor based on at least one of a group comprising (1) an operating objective, (2) the driving output, and (3) a process constraint;

predicting, based on the health condition, whether a motor fault condition will occur prior to the next preventive maintenance checkpoint; and

determining whether to alter the control signal in response to said predicting;

wherein the process constraint is a motor operational frequency to avoid.

22. The method according to claim 21, wherein the operational frequency to avoid is determined based on the motor parameter signal.

23. A method of optimizing the useful life of a motor according to a preventive maintenance schedule that includes a plurality of preventive maintenance checkpoints, the method comprising:

sensing a motor parameter during operation of the motor and generating a corresponding motor parameter signal;

generating, with a controller, a driving output based on the motor parameter signal;

diagnosing a health condition of the motor based on at least one of a group comprising (1) an operating objective, (2) the driving output, and (3) a process constraint;

predicting, based on the health condition, whether a motor fault condition will occur prior to the next preventive maintenance checkpoint; and

determining whether to alter the control signal in response to said predicting;

wherein the process constraint is the criticality of a mission including an allowable risk.

24. A method of optimizing control and diagnostics operations performed on a controlled system, the method comprising:

providing a diagnostics module and a control module, wherein each module is integrated with the controlled system;

generating, with the control module, a driving output in response to feedback from the controlled system;

generating, with the diagnostics module and based on the driving output, a diagnostics signal indicative of the health of the controlled system;

determining an expected time to fail based on the diagnostics signal; and

predicting whether the controlled system will operate according to a predetermined set of criteria in response to said determining step.

25. The method of claim 24, further comprising:

planning a change in control based on said predicting step;

determining a new expected time to fail in response to said planning step; and

predicting whether the controlled unit will operate according to the predetermined set of criteria in response to said determining a new expected time to fail step.

26. The method according to claim 25, further comprising:

prescribing a change in control based on an operating objective; and

predicting whether the controlled unit will operate according to the operating objective based on said prescribing step.

27. The method of claim 26, further comprising generating a controller modification signal in response to at least one of said predicting steps.

28. The method of claim 27, further comprising activating the controller.

29. The method of claim 25, wherein the predetermined set of criteria includes controlled system operation according to a normal operating characteristic for a predetermined amount of time.