LEAD-LAG FILTER ARRANGEMENT FOR ELECTRO-PNEUMATIC CONTROL LOOPS

• US 20090326682A1
• Filed: 09/09/2009
• Published: 12/31/2009
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Original Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Inventors: Latwesen, Annette L., Junk, Kenneth W.
• Granted Patent: US 7,917,233 B2
• Time in Patent Office: Days
• US Class Current: 700/65
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 19/44 pneumatic
• CPC Class Codes: G05B 2219/41203 Lead-phase compensation, lag-phase compensation servo
• CPC Class Codes: G05B 2219/41304 Pneumatic
• CPC Class Codes: G05D 16/2013 using throttling means as controlling means

Abstract

A lead-lag input filter is connected ahead of a positioner feedback loop having one or more valve accessories, such as a volume booster or a QEV, to overcome slow dynamics experienced by the accessories when receiving low amplitude change control or set point signals. A user interface is connected to the lead-lag input filter and enables an operator or other control personnel to view and change the operating characteristics of the lead-lag input filter to thereby provide the control loop with any of a number of desired response characteristics.

Claims

1. A method for controlling a process parameter of a control loop comprising:

providing a reference control signal at an input to a control loop;

providing a lead-lag filter in communication with the reference control signal prior to amplification of the reference control signal;

providing a user interface in operable communication with the lead-lag filter, said user interface facilitating remote manipulation of a ratio of lead-to-lag produced by the lead-lag filter; and

operating the user interface to remotely manipulate the ratio of lead-to-lag of the lead-lag filter to produce an alteration in the process parameter to be controlled.

2. The method of claim 1, wherein operating the user interface includes adjusting at least one tuning coefficient associated with the lead-lag filter by manipulating at least one virtual interface control provided on a display associated with the user interface.

3. The method of claim 2, and displaying data associated with the process parameter to be controlled.

4. The method of claim 3, wherein the data is displayed on the display associated with the user interface.

5. The method of claim 1, and manipulating a virtual ratio of lead-to-lag to generate a predicted response of the process parameter to be controlled, and displaying the predicted response on a display associated with the user interface.

6. The method of claim 1, wherein the reference control signal is a 4-20 mA control signal.

7. A system for tuning a process parameter of a control loop comprising:

a lead-lag input filter in communication with an input to the control loop;

a controller applying an unamplified reference control signal to an input of the lead-lag input filter;

a user interface in operable communication with the lead-lag filter, said user interface including at least one adjustable interface control, wherein adjustment of each of said at least one adjustable interface controls alters at least one tuning coefficient associated with the lead-lag filter.

8. The system of claim 7, wherein the user interface further includes a display for monitoring a process parameter affected by alteration of the at least one tuning coefficient.

9. The system of claim 8, wherein the control loop includes at least one feedback signal that varies with changes in the process parameter.

10. The system of claim 8, wherein the user interface includes a display on which variations in the at least one feedback signal are graphically displayed.

11. The system of claim 7, wherein the user interface further includes a display for a monitoring a predicted response of the process parameter in response to adjustments of each of the at least one adjustable interface controls.

12. The system of claim 11, wherein the user interface is provided with at least one control mechanism to control a latency period between the predicted response of the process parameter to adjustments of each of the at least one adjustable interface controls, and application of the adjustments of each of the at least one adjustable interface controls to the lead-lag filter to effect an actual response of the process parameter.

13. The system of claim 7, wherein said user interface is provided in a location remote from the lead-lag input filter.

14. A system for tuning the response of a control valve comprising:

a control loop including a valve controller, a current-to-pressure transducer, a control valve, and a valve actuator in operable communication with a valve plug of the control valve;

a lead-lag filter in communication with an input to the control loop; and

a process controller supplying an unamplified reference control signal to an input of the lead-lag filter.

15. The system of claim 14, further comprising a user interface in operable communication with the lead-lag filter, said user interface including at least one adjustable interface control, wherein adjustment of each of said at least one adjustable interface controls alters at least one tuning coefficient associated with the lead-lag filter.

16. The system of claim 15, wherein the user interface is located at a remote location from the lead-lag filter.

17. The system of claim 15, wherein the user interface communicates with the lead-lag filter through at least one of a group of telephone lines, satellite transmission, coaxial cable, Ethernet, fiber optic cable, and the Internet.

18. The system of claim 15, wherein the user interface further includes a display for a monitoring a predicted response of a position of the valve plug of the control valve in response to adjustments of each of the at least one adjustable interface controls.

19. The system of claim 18, wherein the user interface is provided with at least one control mechanism to control a latency period between the predicted response of the position of the valve plug of the control valve to adjustments of each of the at least one adjustable interface controls, and application of the adjustments of each of the at least one adjustable interface controls to the lead-lag filter to effect an actual response of the position of the valve plug of the control valve.

20. The system of claim 14, wherein the lead-lag input filter is in communication with a controller, said controller including programming adapted to cause the lead-lag input filter to curtail movement of a valve stem of the control valve operatively coupled to the valve plug as the valve plug approaches at least one of a valve seat and a travel stop of the control valve.

21-34. -34. (canceled)

35. A method for optimally tuning adjustment of a parameter of a control loop comprising:

providing a lead-lag input filter in communication with an input of a control loop;

supplying an unamplified reference control signal to an input of the lead-lag input filter;

providing at least one of a user interface and a controller in operable communication with the lead-lag input filter; and

operating the user interface or controller to signal the lead-lag input filter to modify the reference control signal prior to application of the control signal to the input of the control loop.

36. The method of claim 35, and providing both the user interface and the controller in operable communication with the lead-lag input filter, and selecting among the user interface and the controller.

37. The method of claim 36, wherein upon selecting the controller, at least partially disabling the user interface.

38-42. -42. (canceled)