Systems and methods for detecting a control loop interaction

Patent metadata

Field	Value
Publication number	US-9348325-B2
Application number	US-201213361857-A
Country	US
Kind code	B2
Filing date	Jan 30, 2012
Priority date	Jan 30, 2012
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A system for detecting a control loop interaction between two or more control loops. The system includes a processing circuit configured to store a history of detected loop disturbances for a plurality of control loops. The processing circuit is also configured to compute a measure of interaction between control loops using the history of detected loop disturbances. The processing circuit is further configured to determine whether a loop interaction exists based on the computed measure of interaction.

First claim

What is claimed is:

1. A computerized method for detecting a control loop interaction, the method comprising:
receiving an indication of a control loop disturbance detected by a controller for a first control loop, wherein the control loop disturbance is a change detected in the first control loop that exceeds a disturbance detection threshold;
storing, in a memory, a history of detected loop disturbances for the first control loop and at least a second control loop, wherein each of the detected loop disturbances is stored with a time parameter indicating a time at which the disturbance is detected;
using the history of detected loop disturbances to assign each of a plurality of time periods to one of categories (a), (b), (c), and (d) according to whether a disturbance is detected or not detected during the time period in each of the first and second control loops, wherein a time period is assigned to:
category (a) if a disturbance is detected in the first control loop and not detected in the second control loop during the time period,
category (b) if a disturbance is detected in the second control loop and not detected in the first control loop during the time period,
category (c) if a disturbance is detected in both the first control loop and the second control loop during the time period, and
category (d) if a disturbance is detected in neither the first control loop nor the second control loop during the time period;

generating and storing a set of variables that indicate a quantity of the time periods assigned to each of categories (a)-(d);
calculating, by a processor, a measure of interaction between the first and second control loops using the set of variables, the measure of interaction indicating a statistical correlation between the times at which disturbances are detected in the first control loop and the times at which disturbances are detected in the second control loop;
determining whether a loop interaction exists between the first and second control loops based in part on the measure of interaction; and
using a communications interface to transmit data representing the result of the determination.

2. The method of claim 1 , wherein the controller for the first control loop is an adaptive controller configured to detect the disturbance by detecting a setpoint change for the first control loop controlled by the adaptive controller.

3. The method of claim 1 , wherein the controller for the first control loop is an adaptive controller configured to detect the disturbance by detecting a load change in a control loop controlled by the adaptive controller.

4. The method of claim 1 , wherein the disturbance is at least one of:
(a) a load change;
(b) a setpoint change;
(c) a measured variable change beyond a tolerance limit;
(d) a measured variable change beyond a historical deviation from a setpoint; and
(e) a significant measured variable change.

5. The method of claim 1 , wherein the controller is a pattern recognition adaptive controller.

6. The method of claim 1 , wherein the indication of the control loop disturbance comprises a binary value and the interaction measure comprises a mean-square contingency coefficient.

7. The method of claim 1 , wherein the loop interaction is determined to exist by comparing the measure of interaction to a threshold value.

8. The method of claim 1 , further comprising calculating a plurality of measures of interaction between different sets of two or more control loops and determining a set of possible loop interactions based on the plurality of measures of interaction.

9. The method of claim 1 , wherein the control loops control devices of a heating, ventilation, and air conditioning system.

10. The method of claim 1 , further comprising adjusting a setpoint of the controller in response to a determination that a loop interaction exists for a control loop controlled by the adaptive controller.

11. A system for detecting a control loop interaction comprising:
a processing circuit configured to store, in a memory, a history of detected loop disturbances for two or more control loops, wherein each of the detected loop disturbances is stored with a time parameter indicating a time at which the disturbance is detected;
wherein the processing circuit is configured to use the history of detected loop disturbances to assign each of a plurality of time periods to one of categories (a), (b), (c), and (d) according to whether a disturbance is detected or not detected during the time period in each of the first and second control loops, wherein a time period is assigned to:
category (a) if a disturbance is detected in the first control loop and not detected in the second control loop during the time period,
category (b) if a disturbance is detected in the second control loop and not detected in the first control loop during the time period,
category (c) if a disturbance is detected in both the first control loop and the second control loop during the time period, and
category (d) if a disturbance is detected in neither the first control loop nor the second control loop during the time period;

wherein the processing circuit is configured to generate and store a set of variables that indicate a quantity of the time periods assigned to each of categories (a)-(d);
wherein the processing circuit is configured to calculate a measure of interaction between the two or more control loops using the set of variables, the measure of interaction indicating a statistical correlation between the times at which disturbances are detected in the two or more control loops;
wherein the processing circuit is configured to determine whether a loop interaction exists between the two or more control loops based in part on the measure of interaction; and
wherein the processing circuit causes a communications interface to transmit a message representing that a loop interaction exists when the determination is positive.

12. The system of claim 11 , wherein the processing circuit is further configured to provide adaptive control over one or more control loops and to detect a loop disturbance in the one or more control loops.

13. The system of claim 12 , wherein the processing circuit is configured to detect a loop disturbance by detecting a load change in the one or more control loops.

14. The system of claim 12 , wherein the processing circuit is configured to detect a loop disturbance by detecting a setpoint change in the one or more control loops.

15. The system of claim 12 , wherein the processing circuit is further configured to adjust a setpoint of the one or more control loops in response to a determination that a loop interaction exists for the one or more control loops controlled by the processing circuit.

16. The system of claim 11 , wherein the processing circuit further comprises an interface configured to receive indications of loop disturbances from two or more controllers and to store the indications in the history of detected loop disturbances.

17. The system of claim 11 , wherein the history comprises binary values and the interaction measure comprises a mean-square contingency coefficient.

18. The system of claim 11 , wherein the processing circuit is further configured to calculate a plurality of measures of interaction between different sets of two or more control loops and to determine a set of loop interactions based on the plurality of measures of interaction.

19. A system for detecting a control loop interaction in a heating, ventilation, and air conditioning (HVAC) system compri

Assignees

• Salsbury Timothy I
• House John M
• Seem John E
• Johnson Controls Tech Co

Inventors

• Salsbury Timothy I
• House John M
• Seem John E

Classifications

• G05B13/02 Primary

  electric · CPC title