Feedback control methods and apparatus for electro-pneumatic control systems

• US 20050278074A1
• Filed: 06/14/2004
• Published: 12/15/2005
• 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: Junk, Kenneth William, Metschke, Christopher S.
• Granted Patent: US 7,337,041 B2
• Time in Patent Office: Days
• US Class Current: 700/282
• 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 feedback signal to the electro-pneumatic controller.

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 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 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 feedback signal is based on a derivative of the pressure.

9. An electro-pneumatic control system as defined in claim 1 wherein the 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 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 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 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 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 feedback signal is a first feedback signal, and wherein the electro-pneumatic controller is configured to determine a second feedback signal based on the first feedback signal, and wherein the feedback loop is based on the second feedback signal.

16. An electro-pneumatic control system as defined in claim 15 wherein the second 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 wherein the feedback signal is a first feedback signal, and further comprising a pneumatic actuator coupled to the electro-pneumatic controller to provide a second feedback signal to the electro-pneumatic controller.

19. An electro-pneumatic control system as defined in claim 18 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 and 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 and 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 feedback signal.

23. An electro-pneumatic control system as defined in claim 18 wherein the electro-pneumatic controller is configured to implement a diagnostic monitor loop based on the first feedback signal.

24. An electro-pneumatic controller comprising:

an electro-pneumatic transducer;

a control unit coupled to the electro-pneumatic transducer; and

an input to the control unit, wherein the input is configured to be coupled to a secondary pneumatic power stage.

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

26. An electro-pneumatic controller as defined in claim 24 wherein the input is a first input, and further comprising a second input to the control unit, wherein the second input is configured to be coupled with a pneumatically-actuated device.

27. An electro-pneumatic controller as defined in claim 26 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 input.

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

detecting an operational response associated with a secondary pneumatic power stage; and

controlling an operation of the pneumatically-actuated device based on the operational response associated with the secondary pneumatic power stage.

30. A method as defined in claim 29 further comprising:

detecting an operational response associated with a pneumatically-actuated device; and

controlling the operation of the pneumatically-actuated device based on the operational response associated with 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 and a quick exhaust valve.

32. A method as defined in claim 29 wherein detecting the 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 operational response comprises determining a derivative of the pressure.

34. A method as defined in claim 29 wherein detecting the 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 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 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 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 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 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 the operational response is a first operational response, and wherein controlling the operation of the pneumatically-actuated device comprises determining a second operational response based on the first operational response, and wherein the feedback loop is based on the second operational response.

43. A method as defined in claim 42 wherein the second 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 and the pneumatically-actuated device based on the operational response.