EXTREMUM SEEKING CONTROL WITH ACTUATOR SATURATION CONTROL

• US 20120239165A1
• Filed: 05/30/2012
• Published: 09/20/2012
• 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: Li, Yaoyu, Seem, John E.
• Granted Patent: US 8,694,132 B2
• Time in Patent Office: Days
• US Class Current: 700/28
• 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

An extremum seeking control method optimizes a control process for a plant such as an air handling unit. The method improves the performance of an extremum seeking control strategy by limiting, removing or preventing the effects of an actuator saturation condition, particularly as the extremum seeking control strategy relates to HVAC applications.

Claims

1. A method for optimizing a control process for an actuator, the method comprising:

operating the control process using an extremum seeking control strategy; and

using an electronics circuit to compensate for an actuator saturation condition of the extremum seeking control strategy.

2. The method as recited in claim 1, further comprising:

receiving a feedback signal from the actuator;

comparing the feedback signal to a control signal sent to the actuator;

subtracting the control signal from the feedback signal to obtain a difference signal;

amplifying the difference signal to exaggerate the difference signal; and

providing the amplified difference signal to an input of the extremum seeking control strategy to override previously determined optimum control parameters.

3. The method as recited in claim 2, further comprising:

receiving the amplified difference signal at the input of the extremum seeking control strategy; and

providing the amplified difference signal to an integrator configured to reduce a performance gradient.

4. The method as recited in claim 1, further comprising:

distinguishing the actuator saturation condition from a state in which the actuator is not saturated.

5. The method as recited in claim 4, further comprising:

resetting the extremum seeking control strategy when the actuator saturation condition is distinguished.

6. The method as recited in claim 1, further comprising:

retrieving physical boundary information for the actuator from memory; and

detecting the actuator saturation condition using the retrieved physical boundary information.

7. A controller for controlling an actuator, the controller comprising:

a processing circuit configured to operate the plant using an extremum seeking control strategy and to compensate for an actuator saturation condition of the extremum seeking control strategy.

8. The controller of claim 7, further comprising:

an input configured to receive a feedback signal from the actuator; and

an output configured to send a control signal to the actuator;

wherein the processing circuit is further configured to subtract the control signal from the feedback signal to obtain a difference signal and wherein the processing circuit is further configured to provide the difference signal to a portion of the processing circuit configured to provide the extremum seeking control strategy, the difference signal to override previously determined optimal control parameters.

9. The controller of claim 8, further comprising:

amplifying the difference signal prior to providing the difference signal to the logic of the processing circuit for providing the extremum seeking control strategy.

10. The controller of claim 8, wherein the portion of the processing circuit configured to provide the extremum seeking control strategy comprises an integrator configured to reduce a performance gradient, and wherein the integrator is configured to receive the difference signal as an input.

11. The controller of claim 8, wherein the processing circuit is further configured to distinguish the actuator saturation condition from a state in which the actuator is not saturated.

12. The controller of claim 11, wherein the processing circuit is further configured to reset the extremum seeking control strategy when the actuator saturation condition is distinguished.

13. The controller of claim 8, wherein the processing circuit further comprises:

memory storing physical boundary information for the actuator, wherein the processing circuit is configured to retrieve the physical boundary information from memory and to detect the actuator saturation condition using the retrieved physical boundary information.

14. The controller of claim 8, wherein the processing circuit comprises a processor and a memory device communicably coupled to the processor, the memory device storing computer code for operating the plant using the extremum seeking control strategy and computer code for compensating for the actuator saturation condition of the extremum seeking control strategy.

15. A controller for an air handling unit having an actuator that opens and closes a damper to control the amount of outdoor air used for cooling the air provided to a building space by the air handling unit, comprising:

an input interface configured to receive a temperature sensor input;

a temperature regulator control module configured to provide a command to a temperature regulator system configured to chill air provided by the air handling unit, wherein the temperature regulator control module determines the command based on the temperature sensor input received at the input interface;

an extremum seeking control module configured to receive the command from the temperature regulator control module and comprising an integrator and a performance gradient probe, the performance gradient probe configured to use the received command to detect a difference between an estimated optimal position for the actuator and a current actuator position and to provide the detected difference to the integrator, wherein the integrator is configured to calculate an actuator command signal configured to reduce the detected difference;

an output interface configured to provide the actuator command signal to the actuator; and

a feedback interface configured to receive a feedback signal from the actuator representative of the actual position of the actuator after the actuator is adjusted in response to the actuator command signal;

wherein the extremum seeking control module is further configured to determine an error between the actuator command signal and the feedback signal;

wherein the extremum seeking control module is further configured to add the error to the detected difference provided to the integrator of the extremum seeking control module.

16. The controller of claim 15, wherein the addition of the error to the detected difference of the integrator is configured to reduce or change the sign of the detected difference provided to the integrator.

17. The controller of claim 16, wherein the estimated optimal position for the actuator is calculated to minimize the power consumption of the temperature regulator system by maximizing the use of outdoor air provided to the building by the damper.

18. The controller of claim 17, wherein the extremum seeking control module comprises a first processing element configured to determine the error between the actuator command signal and the feedback signal by subtracting the actuator command signal from the feedback signal.

19. The controller of claim 18, wherein the extremum seeking control module further comprises a second processing element configured to amplify the error by a gain to at least offset integrator windup.

20. The controller of claim 19, wherein the detected difference provided to the integrator of the extremum seeking control module is not affected by the second processing element when the error is zero.