Feedback control methods and apparatus for electro-pneumatic control systems

• US 7,337,041 B2
• Filed: 06/14/2004
• Issued: 02/26/2008
• Est. Priority Date: 06/14/2004
• Status: Active Grant

• Current Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Original Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Inventors: Metschke, Christopher S., Junk, Kenneth William
• Primary Examiner(s): Knight; Anthony
• Assistant Examiner(s): Chang; Sunray
• Application Number:
  US10/867,189
• Publication Number:
  US 20050278074A1
• Time in Patent Office: 1,352 Days
• Field of Search: 700/275, 700/282, 604/13, 702/188, 137/85
• US Class Current: 700/275
• CPC Class Codes: F15B 21/08 Servomotor systems incorporating electrically operated control means F15B21/02, F15B21/065 take precedence
• CPC Class Codes: F15B 5/006 with electrical means, e.g. electropneumatic transducer F15B5/003 takes precedence
• CPC Class Codes: F15B 9/03 with electrical control means F15B9/07, F15B9/09, F15B9/17 take precedence
• CPC Class Codes: F15B 9/09 with electrical control means
• CPC Class Codes: Y10T 137/2409 With counter-balancing pressure feedback to the modulating device

Abstract

Methods and apparatus related to feedback control for electro-pneumatic control systems are disclosed. An example electro-pneumatic control system comprises an electro-pneumatic controller and a secondary pneumatic power stage coupled to the electro-pneumatic controller to provide a feedback signal to the electro-pneumatic controller.

Claims

1. An electro-pneumatic control system comprising:

an electro-pneumatic controller; and

a secondary pneumatic power stage coupled to the electro-pneumatic controller to provide a first feedback signal from the secondary pneumatic power stage to the electro-pneumatic controller, wherein each of the secondary pneumatic power stage and the electro-pneumatic controller is configured to be coupled to a pneumatic actuator, wherein the electro-pneumatic controller is configured to receive a second feedback signal from the pneumatic actuator, and wherein the second feedback signal is separate from the first feedback signal.

2. An electro-pneumatic control system as defined in claim 1 wherein the secondary pneumatic power stage comprises a volume booster.

3. An electro-pneumatic control system as defined in claim 1 wherein the secondary pneumatic power stage comprises a quick exhaust valve.

4. An electro-pneumatic control system as defined in claim 1 wherein the first feedback signal is based on a measurement of a position.

5. An electro-pneumatic control system as defined in claim 4 wherein the position is based on a poppet valve position.

6. An electro-pneumatic control system as defined in claim 5 further comprising a hall-effect sensor to measure the poppet valve position.

7. An electro-pneumatic control system as defined in claim 1 wherein the first feedback signal is based on a pressure associated with an output of the secondary pneumatic power stage.

8. An electro-pneumatic control system as defined in claim 7 wherein the first feedback signal is based on a derivative of the pressure.

9. An electro-pneumatic control system as defined in claim 1 wherein the first feedback signal is based on a first pressure associated with a first output of the secondary pneumatic power stage and a second pressure associated with a second output of the secondary pneumatic power stage.

10. An electro-pneumatic control system as defined in claim 9 wherein the first feedback signal is based on a difference between the first pressure and the second pressure.

11. An electro-pneumatic control system as defined in claim 10 wherein the first feedback signal is based on a derivative of the difference between the first pressure and the second pressure.

12. An electro-pneumatic control system as defined in claim 1 wherein the electro-pneumatic controller is configured to convert the first feedback signal to correspond to an air mass flow associated with an output of the secondary pneumatic power stage.

13. An electro-pneumatic control system as defined in claim 1 wherein the electro-pneumatic controller is configured to implement a feedback loop based on the first feedback signal.

14. An electro-pneumatic control system as defined in claim 13 wherein the feedback loop is a negative feedback loop.

15. An electro-pneumatic control system as defined in claim 13 wherein the electro-pneumatic controller is configured to determine a third feedback signal based on the first feedback signal, and wherein the feedback loop is based on the third feedback signal.

16. An electro-pneumatic control system as defined in claim 15 wherein the third feedback signal is equal to the first feedback signal scaled by a gain factor.

17. An electro-pneumatic control system as defined in claim 16 wherein the gain factor is based on a response characteristic of a pneumatically-actuated device.

18. An electro-pneumatic control system as defined in claim 1 further comprising the pneumatic actuator coupled to the electro-pneumatic controller to provide the second feedback signal to the electro-pneumatic controller.

19. An electro-pneumatic control system as defined in claim 1 wherein the electro-pneumatic controller is configured to implement a feedback loop based on the first and second feedback signals.

20. An electro-pneumatic control system as defined in claim 19 wherein the electro-pneumatic controller is configured to determine at least one of a third feedback signal based on the first feedback signal or a fourth feedback signal based on the second feedback signal, and wherein the feedback loop is based on the at least one of the third feedback signal or the fourth feedback signal.

21. An electro-pneumatic control system as defined in claim 20 wherein the third feedback signal is equal to the first feedback signal scaled by a first gain factor and the fourth feedback signal is equal to the second feedback signal scaled by a second gain factor.

22. An electro-pneumatic control system as defined in claim 1 wherein the electro-pneumatic controller is configured to implement a diagnostic monitor based on the first feedback signal.

23. An electro-pneumatic control system as defined in claim 22 wherein the electro-pneumatic controller is configured to implement a second diagnostic monitor based on the second feedback signal.

24. An electro-pneumatic controller comprising:

an electro-pneumatic transducer;

a control unit coupled to the electro-pneumatic transducer;

a first input to the control unit, wherein the first input is configured to be coupled to a secondary pneumatic power stage; and

a second input to the control unit, wherein the second input is configured to be coupled to a pneumatic actuator, and wherein the first and second input signals are separate input signals.

25. An electro-pneumatic controller as defined in claim 24 wherein the control unit is configured to implement a feedback loop based on the first input.

26. An electro-pneumatic controller as defined in claim 24 wherein the second input is indicative of an operational response of a pneumatically-actuated device coupled to the pneumatic actuator.

27. An electro-pneumatic controller as defined in claim 24 wherein the control unit is configured to implement a feedback loop based on the first and second inputs.

28. An electro-pneumatic controller as defined in claim 24 wherein the control unit is configured to implement a diagnostic monitor based on the first input.

29. A method of controlling a pneumatically-actuated device in an electro-pneumatic control system comprising:

detecting via a controller a first operational response of a secondary pneumatic power stage;

detecting via the controller a second operational response of a pneumatic actuator; and

controlling an operation of the pneumatically-actuated device based on the first and second operational responses, wherein the first and second responses are separate signals.

30. A method as defined in claim 29 wherein the second operational response is indicative of an operation of the pneumatically-actuated device.

31. A method as defined in claim 29 wherein the secondary pneumatic power stage comprises at least one of a volume booster or a quick exhaust valve.

32. A method as defined in claim 29 wherein detecting the first operational response comprises measuring a pressure associated with an output of the secondary pneumatic power stage.

33. A method as defined in claim 32 wherein detecting the first operational response comprises determining a derivative of the pressure.

34. A method as defined in claim 29 wherein detecting the first operational response comprises measuring a first pressure associated with a first output of the secondary pneumatic power stage and a second pressure associated with a second output of the secondary pneumatic power stage.

35. A method as defined in claim 34 wherein detecting the first operational response comprises determining a difference between the first pressure and the second pressure.

36. A method as defined in claim 35 wherein detecting the first operational response comprises determining a derivative of the difference between the first pressure and the second pressure.

37. A method as defined in claim 29 wherein detecting the first operational response comprises measuring a position.

38. A method as defined in claim 37 wherein measuring the position comprises measuring a poppet valve position.

39. A method as defined in claim 29 wherein controlling the operation of the pneumatically-actuated device comprises converting the first operational response to correspond to an air mass flow associated with an output of the secondary pneumatic power stage.

40. A method as defined in claim 29 wherein controlling the operation of the pneumatically-actuated device comprises implementing a feedback loop based on the first operational response.

41. A method as defined in claim 40 wherein the feedback loop is a negative feedback loop.

42. A method as defined in claim 40 wherein controlling the operation of the pneumatically-actuated device comprises determining a third operational response based on the first operational response, and wherein the feedback loop is based on the third operational response.

43. A method as defined in claim 42 wherein the third operational response is equal to the first operational response scaled by a gain factor.

44. A method as defined in claim 43 wherein the gain factor is based on an operational response associated with the pneumatically-actuated device.

45. A method as defined in claim 29 further comprising determining diagnostic information for at least one of the secondary pneumatic power stage or the pneumatically-actuated device based on the first operational response.