Reducing controller updates in a control loop

Patent metadata

Field	Value
Publication number	US-11199824-B2
Application number	US-201514663077-A
Country	US
Kind code	B2
Filing date	Mar 19, 2015
Priority date	Jan 17, 2012
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

A control technique controls a process in a manner that reduces the number of controller changes provided to a controlled device, and so reduces the power consumption of the controlled device along with the loading of a process control communications network disposed between the controller and the controlled device. This technique is very useful in a control system having wirelessly connected field devices, such as sensors and valves which, in many cases, operate off of battery power. Moreover, the control technique is useful in implementing a control system in which control signals are subject to intermittent, non-synchronized or significantly delayed communications and/or in a control system that receives intermittent, non-synchronized or significantly delayed process variable measurements to be used as feedback signals in the performance of closed-loop control.

First claim

The invention claimed is:

1. A method of controlling a controlled device within a process using a control signal, comprising:
implementing, on a process controller computing device, multiple iterations of a control routine to generate, during each of the multiple iterations, a control signal value for controlling the controlled device; and
implementing a communications routine within a computer processing device coupled to the process controller computing device including, during each of the multiple iterations of the control routine,
determining if a minimum predetermined communication time period has passed, and
determining if an acknowledgement has been received from the controlled device indicating that the controlled device has received a previous control signal;
and, at least when the minimum predetermined communication time period has passed and the acknowledgement has been received from the controlled device indicating that the controlled device has received the previous control signal, determining if a further signaling condition is met; and
sending a new control signal to the controlled device via a communications link only when the minimum predetermined communication time period has passed and the acknowledgement has been received from the controlled device indicating that the controlled device has received the previous control signal and when the further signaling condition is met,
wherein sending the new control signal to the controlled device via the communications link includes sending a new control signal value and a predetermined time to implement the new control signal value at the controlled device, and
wherein the control routine generates the new control signal based on an assumption that the controlled device implemented a previous control signal value of the previous control signal at the predetermined time to implement the previous control signal value, the new control signal generated prior to the control routine receiving an indication of a feedback signal associated with the previous control signal.

2. The method of claim 1 , wherein determining if the further signaling condition is met includes determining if the difference between the control signal value generated for a control routine iteration and the value of the previous control signal sent to controlled device is greater than a threshold value.

3. The method of claim 1 , wherein determining if the further signaling condition is met includes determining if the time since the previous control signal was sent to the controlled device exceeds a maximum threshold time value.

4. The method of claim 1 , wherein determining if the further signaling condition is met includes determining if either the difference between the control signal value generated for a control routine iteration and the value of the previous control signal sent to controlled device is greater than a threshold value or the time since the previous control signal was sent to the controlled device exceeds a maximum threshold time value.

5. The method of claim 1 , wherein implementing the communications routine within a computer processing device coupled to the process controller computing device includes implementing the communications routine during each of a multiplicity of consecutive iterations of the control routine.

6. The method of claim 1 , wherein sending a new control signal to the controlled device via a communications link includes determining if the difference between the control signal value for the control routine iteration and the value of the previous control signal sent to controlled device is greater than a maximum change threshold value and sending the new control signal as a limited version of the control signal value for the control routine iteration when the difference between the control signal value for the control routine iteration and the value of the previous control signal sent to controlled device is greater than the maximum change threshold value.

7. The method of claim 1 , wherein sending the new control signal to the controlled device via a communications link includes sending the new control signal to the controlled device via a wireless communications link.

8. The method of claim 1 , wherein sending the new control signal to the controlled device via a communications link includes sending the new control signal to the controlled device via a wired communications link.

9. The method of claim 1 , wherein sending the time to implement the new control signal value includes sending the time as an offset time.

10. The method of claim 1 , wherein sending the time to implement the new control signal value includes sending the time as an absolute time.

11. The method of claim 1 , wherein implementing, on the process controller computing device, multiple iterations of the control routine includes implementing a proportional, integral, derivative type control routine.

12. The method of claim 1 , further including receiving the feedback signal via a wireless communication link.

13. The method of claim 1 , further including receiving the feedback signal via a wired communication link.

14. The method of claim 1 , wherein the indication of the feedback signal originates from a second controlled device, the second controlled device different from the controlled device.

15. The method of claim 1 , wherein the indication of the feedback signal originates from the controlled device.

16. The method of claim 1 , wherein an attribute of the controlled device as determined from the feedback signal is used by the control routine during a further iteration to generate a further new control signal value.

17. The method of claim 1 , wherein each of the control signal and the new control signal is sent via one of: (i) a wireless transmission or (ii) a wired transmission,
wherein the controlled device is associated a first wireless controller error value for the wireless transmission, and wherein the controlled device is associated with a wired controller error value for the wired transmission,
wherein the control routine is configured to implement a custom command for transmitting the wireless transmission,
wherein the custom command modifies the controlled device by reducing the first wireless controller error value to a reduced wireless controller error value of the controlled device.

18. The method of claim 17 , wherein each of the control signal and the new control signal is sent via the wireless transmission, and
wherein based on the custom command, a wireless error rate of the controlled device is equal to a wired error rate of the controlled device.

19. The method of claim 18 , wherein each of the reduced wireless controller error value and the wired controller error value is an integral absolute error (IAE) value, and wherein the reduced wireless controller error value and the wired controller error value differ by no more than a value of 300 IAE.

20. The method of claim 17 , wherein the custom command is a command configured for a WirelessHART-based network.

21. A process control system for use in controlling a controlled device within a process using a control signal, comprising:
a process controller that stores a control routine and that implements the control routine during multiple iterations to generate, during each of the multiple iterations, a control signal value for controlling the controlled device; and
a communications routine, implemented within a computer processing device that is coupled to the process controller, where

Assignees

• Fisher Rosemount Systems Inc

Inventors

• Blevins Terrence L
• Nixon Mark J
• Jensen Kurtis K
• Panther Mitchell S
• Chen Deji
• Rotvold Eric D

Classifications

• G05B17/02 Primary

  electric · CPC title