FAULT DETECTION SYSTEMS AND METHODS FOR SELF-OPTIMIZING HEATING, VENTILATION, AND AIR CONDITIONING CONTROLS

• US 20090083583A1
• Filed: 11/25/2008
• Published: 03/26/2009
• Est. Priority Date: 07/17/2007
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Seem, John E., Salsbury, Timothy, Li, Yaoyu
• Granted Patent: US 8,027,742 B2
• Time in Patent Office: Days
• US Class Current: 714/39
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2011/0006 using low temperature external supply air to assist cooling
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 5/01 electric

Abstract

A fault detection system for detecting a fault in a process system includes a first circuit configured to modify an input of the process system with a modifying signal. The fault detection system further includes a second circuit configured to receive an output from the process system and configured to determine whether the fault exists based on at least one of a reduction of a signal component and an unexpected transformation of the signal component, wherein the signal component corresponds to a function of the modifying signal.

Claims

1. A method for detecting a fault in a process system, the method comprising:

modifying an input of the process system with a modifying signal;

monitoring an output of the process system for a signal component corresponding to a function of the modifying signal; and

determining whether a fault exists based on at least one of a reduction of the signal component and an unexpected transformation of the signal component;

wherein the process system is operated using a closed-loop system and is subject to feedback control.

2. The method of claim 1, wherein the modifying signal is a periodic signal.

3. The method of claim 2, wherein the output provides a performance measure of the process system and the method further comprises:

optimizing the process system utilizing the output.

4. The method of claim 3, wherein the optimization is conducted according to an extremum seeking control strategy.

5. The method of claim 4, wherein the output is used by the feedback control and by the extremum seeking control strategy.

6. The method of claim 4, wherein the process system comprises an air handling unit configured to regulate temperature using a temperature regulator, wherein the air handling unit comprises a damper controlled by an actuator, the method further comprising:

controlling the temperature regulator; and

utilizing the extremum seeking control strategy to operate the actuator by providing a second control signal to the actuator;

wherein the second control signal is the input of the process system modified by the modifying signal.

7. The method of claim 6, wherein the modifying signal comprises a dither signal provided to the input as a part of the extremum seeking control strategy.

8. The method of claim 7, wherein the dither signal is at least one of rectangular, triangular, ellipsoidal, and sinusoidal.

9. The method of claim 8, further comprising:

extracting the signal component from the output using a filter network.

10. The method of claim 9, wherein determining that the fault exists based on at least one of a reduction of the signal component and an unexpected transformation of the signal component comprises at least one of:

(a) comparing the signal component to a threshold power level; and

(b) comparing a phase of the signal component to an expected phase.

11. The method of claim 10, wherein monitoring for the output of the process system for a signal component corresponding to a function of the modifying signal comprises at least one of:

(a) extracting the signal component from the output using a filter configured with a passband near that of an angular frequency component of the modifying signal;

(b) conducting a frequency domain analysis of the output using a fast Fourier transform; and

(c) conducting a time-domain analysis of the output using a zero-cross detection method.

12. A fault detection system for detecting a fault in a process system:

a first circuit configured to modify an input of the process system with a modifying signal;

a second circuit configured to receive an output from the process system and configured to determine whether a fault exists based on at least one of a reduction of a signal component and an unexpected transformation of the signal component, wherein the signal component corresponds to a function of the modifying signal; and

wherein the process system operated using a closed loop system and is subject to feedback control.

13. The system of claim 12, wherein the first circuit is part of an extremum seeking controller and wherein the modifying signal applied to the input of the process system comprises a dither signal applied to the input for the purpose of probing for a performance gradient used by the extremum seeking controller to optimize the process system.

14. The system of claim 13, further comprising:

a filter configured to extract the signal component from the output.

15. The system of claim 14, wherein the filter is a bandpass filter.

16. A controller for detecting a fault in a process system, the controller comprising:

a circuit configured to affect an input of the process system, the circuit configured to modify the input with a modifying signal, wherein the circuit is further configured to monitor an output of the process system for a signal component corresponding to a function of the modifying signal, and wherein the circuit is further configured to determine whether the fault exists based on at least one of a reduction of the signal component and an unexpected transformation of the signal component;

wherein the circuit is further configured to provide an output signal indicative of the presence of the fault to at least one of a computerized system, a memory device, a communications device, and an electronic display device;

wherein the controller further comprises circuitry configured to operate the process system as a closed-loop system and is subject to feedback control.

17. The controller of claim 16, wherein the circuit is further configured to provide an extremum seeking control strategy to at least one manipulated variable of the process system by using the modifying signal to identify a performance gradient in the process system.

18. The controller of claim 17, wherein the process system comprises a temperature regulator configured to regulate temperature in response to a first control signal, and wherein the process system further comprises a damper moved by an actuator;

wherein the circuit is configured to operate the actuator by providing a second control signal to the actuator, and wherein modifying the input of the process system with a modifying signal comprises modifying the second control signal provided to the actuator with the modifying signal.

19. The controller of claim 18, wherein the circuit is configured to operate the actuator according to the extremum seeking control strategy.

20. The controller of claim 19, wherein the circuit comprises:

a filter configured to filter the output of the process system to extract the signal component from the output.

21. The controller of claim 20, wherein the filter comprises a bandpass filter.

22. The controller of claim 21, wherein the circuit is configured to compare the signal component to a threshold power level to determine whether the fault exists.

23. The controller of claim 16, further comprising:

wherein the circuit is further configured to provide an output signal indicative of the presence of the fault to at least one of a computerized system, a memory device, a communications device, and an electronic display device.

24. The controller of claim 16, wherein the output is fed back to the circuitry configured to operate the process system as a closed-loop system.

25. The controller of claim 24, wherein the input to the process system is provided by the circuitry configured to operate the process system as a closed-loop system.

26. The controller of claim 16, wherein the output is neither used by the circuitry configured to operate the process system as a closed-loop system nor is the output used by circuitry configured to optimize the process system.

27. The controller of claim 16, wherein the circuitry configured to operate the process system as a closed-loop system is a feedback controller.