Building climate control system with decoupler for independent control of interacting feedback loops

Disclosed is a system to control a climate of a space via a first control loop and a second control loop interacting with the first control loop. The system includes a first controller of the first control loop to generate a first control signal based on a first modified set point and a first feedback signal. The system further includes a second controller of the second control loop to generate a second control signal based on a second modified set point and a second feedback signal. The system further includes a decoupler configured to predict a first effect of the first control signal on the second control loop and a second effect of the second control signal on the first control loop, and generate the first modified set point and the second modified set point to reduce the first effect and the second effect.

BACKGROUND

The present disclosure relates generally to control systems for a heating, venting, and air conditioning (HVAC) system. More particularly, the present disclosure relates to a decoupler for improving independent control of interacting feedback loops.

HVAC systems can be used to control the climate of a space (e.g., in a building). For example, HVAC systems may allow a temperature, pressure, humidity, or a combination of them in a room to be controlled. HVAC systems often include a feedback loop comprised of a water plant, a heater plant, or both for adjusting a temperature, and a sensor for sensing a temperature in a room. These components in the feedback loop operate together to set the climate within the room to be at a target climate.

Some HVAC systems include multiple feedback loops for controlling climates of different areas. For example, a first feedback loop may be responsible for controlling a climate in a first area, and a second feedback loop may be responsible for controlling a climate in a second area near the first area. The first feedback loop and the second feedback loop may be designed to be isolated from each other to allow independent controls of climates in two areas. However, an interaction between the first feedback loop and the second feedback loop may occur, thereby affecting controls of the climates in the two areas. For example, a wall separating the first area and the second area may be removed, which may cause interaction between the feedback loops. Such interaction between the feedback loops may obstruct accurate control of the climate in different areas.

SUMMARY

Various embodiments of the present disclosure relate to a system to control a climate of a space via a first control loop and a second control loop that interacts with the first control loop. The system includes a first controller of the first control loop. The first controller is configured to receive a first modified set point and a first feedback signal, and to generate a first control signal based on the first modified set point and the first feedback signal. The system further includes a second controller of the second control loop. The second controller is configured to receive a second modified set point and a second feedback signal, and to generate a second control signal based on the second modified set point and the second feedback signal. The system further includes a decoupler coupled to the first controller and the second controller. The decoupler is configured to receive a first set point, a second set point, the first feedback signal, and the second feedback signal. The decoupler is further configured to predict a first effect of the first control signal on the second control loop, and predict a second effect of the second control signal on the first control loop. The decoupler is further configured to generate the first modified set point and the second modified set point based on the first set point, the second set point, the first feedback signal, and the second feedback signal to reduce the first predicted effect and the second predicted effect.

Various embodiments of the present disclosure also relate to a method of controlling a climate of a space via a first control loop and a second control loop that interacts with the first control loop. The method includes receiving, by a decoupler, a first set point, a second set point, a first feedback signal, and a second feedback signal. The method further includes predicting a first effect of a first control signal on the second control loop. The method further includes predicting a second effect of a second control signal on the first control loop. The method further includes generating, by the decoupler, a first modified set point and a second modified set point based on the first set point, the second set point, the first feedback signal, and the second feedback signal to reduce the first predicted effect and the second predicted effect. The method further includes generating, by a first controller of the first control loop electrically coupled to the decoupler, the first control signal based on the first modified set point and the first feedback signal. The method further includes generating, by a second controller of the second control loop electrically coupled to the decoupler, the second control signal based on the second modified set point and the second feedback signal.

DETAILED DESCRIPTION

Overview

Referring generally to the FIGURES, systems and methods for improving independent controls of interacting feedback loops in an HVAC system are described. More particularly, the present disclosure relates to a decoupler for improving control of interacting feedback loops.

In some embodiments, a disclosed system herein includes a decoupler to improve independent control of interacting feedback loops for controlling climates of different areas. In one aspect, the decoupler receives target set points, and generates modified set points by modifying the target set points. Each target set point may be an electrical signal or data indicating a target climate (e.g., target temperature, pressure, or humidity) of a respective area. The decoupler predicts interactions between feedback loops, and performs modifications on the target set points based on the predictions. Each feedback loop may include a feedback loop controller for generating a control signal according to a target set point and a sensed climate (also referred to as “a measured climate”), and a climate actuator (e.g., heater, cooler, a valve, etc.) for changing climate in a respective area according to the control signal. The decoupler predicts an effect of a control signal for controlling a feedback loop on another feedback loop. Moreover, the decoupler modifies the target set points to generate the modified set points according to the predicted effect. The modified set points may improve independent control of climates in different rooms. For example, a first modified set point applied to a first feedback loop and a second modified set point applied to a second feedback loop allow climate of a first area to be controlled according to a first target set point regardless of a second target set point, and climate of a second area to be controlled according to the second target set point regardless of the first target set point.

Beneficially, the disclosed system provides several advantages. In one aspect, the system can dynamically adapt to a change in a configuration of a space. For example, when a wall separating two areas within a space is removed, the decoupler can predict a change in interactions between two feedback loops, and adaptively generate modified set points according to the predicted change. In another aspect, the disclosed system implements the decoupler at a front end before the feedback loops, allowing ease of integration with existing feedback loops or existing components of the feedback loops. Often, a feedback loop controller and a climate actuator in a feedback loop are implemented in a single package. By implementing the decoupler at the front end as disclosed herein, any modifications on a signal or an operation between the feedback loop controller and the climate actuator can be eschewed.

Building and HVAC System

Referring now toFIGS. 1-3, an exemplary HVAC system in which the systems and methods of the present disclosure can be implemented are shown, according to an exemplary embodiment. While the systems and methods of the present disclosure are described primarily in the context of a building HVAC system, it should be understood that the control strategies described herein may be generally applicable to any type of control system.

Although subplants202-212are shown and described as heating and cooling water for circulation to a building, it is understood that any other type of working fluid (e.g., glycol, CO2, etc.) can be used in place of or in addition to water to serve the thermal energy loads. In other embodiments, subplants202-212can provide heating and/or cooling directly to the building or campus without requiring an intermediate heat transfer fluid. These and other variations to waterside system200are within the teachings of the present invention.

Hot TES subplant210is shown to include a hot TES tank242configured to store the hot water for later use. Hot TES subplant210can also include one or more pumps or valves configured to control the flow rate of the hot water into or out of hot TES tank242. Cold TES subplant212is shown to include cold TES tanks244configured to store the cold water for later use. Cold TES subplant212can also include one or more pumps or valves configured to control the flow rate of the cold water into or out of cold TES tanks244.

Cooling coil334can receive a chilled fluid from waterside system200(e.g., from cold water loop216) via piping342and can return the chilled fluid to waterside system200via piping344. Valve346can be positioned along piping342or piping344to control a flow rate of the chilled fluid through cooling coil334. In some embodiments, cooling coil334includes multiple stages of cooling coils that can be independently activated and deactivated (e.g., by AHU controller330, by BMS controller366, etc.) to modulate an amount of cooling applied to supply air310.

Each of valves346and352can be controlled by an actuator. For example, valve346can be controlled by actuator354and valve352can be controlled by actuator356. Actuators354-356can communicate with AHU controller330via communications links358-360. Actuators354-356can receive control signals from AHU controller330and can provide feedback signals to AHU controller330. In some embodiments, AHU controller330receives a measurement of the supply air temperature from a temperature sensor362positioned in supply air duct312(e.g., downstream of cooling coil334and/or heating coil336). AHU controller330can also receive a measurement of the temperature of building zone306from a temperature sensor364located in building zone306.

In some embodiments, AHU controller330receives information (e.g., commands, set points, operating boundaries, etc.) from BMS controller366and provides information (e.g., temperature measurements, valve or actuator positions, operating statuses, diagnostics, etc.) to BMS controller366. For example, AHU controller330can provide BMS controller366with temperature measurements from temperature sensors362-364, equipment on/off states, equipment operating capacities, and/or any other information that can be used by BMS controller366to monitor or control a variable state or condition within building zone306.

Example Climate Control System

Referring toFIG. 4A, a drawing of an HVAC system400A controlling climates of two rooms410A,410B with independent feedback loops450A,450B is shown, according to some embodiments. The HVAC system400A may be the HVAC system100ofFIG. 1. InFIG. 4A, the HVAC system400A includes an air handling unit405, dampers420A,420B (e.g., valves), thermostats425A,425B, and the feedback loop controllers435A,435B. The air handling unit405supplies air to the rooms410A,410B through a common duct408and separate ducts418A,418B coupled to the common duct408. Air supplied to the room410A is controlled by the first feedback loop450A including the damper420A, the thermostat425A and the feedback loop controller435A to adjust climate of the room410A. Similarly, air supplied to the room410B is controlled by the second feedback loop450B including the damper420B, the thermostat425B and the feedback loop controller435B to adjust climate of the room410B.

A thermostat425is a device to provide a target set point and a feedback signal for a corresponding room410. A target set point is a signal or data indicating a target climate (e.g., target temperature, target pressure, target humidity, etc.) of its associated area. The feedback signal may be an electrical signal or data indicating a sensed climate (e.g., measured temperature, measured pressure, measured humidity, etc.) of its associated area. The thermostat425provides the target set point and the feedback signal to the feedback loop controller435through a wired or wireless communication link. The thermostat425may include a switch, push buttons, or touch sensor integrated display allowing a user to select a target climate. The thermostat425generates a target set point indicating the selected target climate, and provides the target set point to the feedback loop controller435. In addition, the thermostat425may include one or more climate sensors (e.g., a temperature sensor, pressure sensor, humidity sensor, etc.) that sense climate of an area of a room, and generate a feedback signal based on the sensed climate. The thermostat425also provides the feedback signal to the feedback loop controller435.

The feedback loop controller435is a component that receives target set points and feedback signals from the thermostats425, and controls a climate of a corresponding room410accordingly. The feedback loop controller435may be hardware, software, firmware, or a combination thereof. Examples of feedback loop controller435include a proportional-integral-derivative (PID) controller and a proportional-integral (PI) controller. In one implementation, the feedback loop controller435is communicatively coupled to the thermostat425through wired or wireless communication links. The feedback loop controller435may be integrated with the damper420in a single package. Alternatively, the feedback loop controller435and the damper420may be physically separated and electrically coupled to each other through conductive wires or traces. In this configuration, the feedback loop controller435receives a target set point and a feedback signal of the room410from the thermostat425, and generates a control signal for controlling an amount of opening (or closing) of the damper420based on the target set point and the feedback signal of the room410.

FIG. 4Bis a drawing of two feedback loops450A,450B interacting with each other due to a change in a configuration of the two rooms410A,410B ofFIG. 4A. A configuration of two rooms410A,410B may be temporarily or permanently changed by modifying a wall, a ceiling, a removable partition, or ductwork connected to the two rooms410A,410B. In the example shown inFIG. 4B, air can be exchanged through a space, at which the wall separating the rooms410A,410B inFIG. 4Awas located. The exchanged air can affect climates of the rooms410A,410B, thereby causing an interaction between the two feedback loops450A,450B. Such interaction between the two feedback loops450A,450B may degrade an ability to independently control climates of the rooms410A,410B.

FIG. 5Ashows a schematic representation of a climate control system500A including two independent feedback loops. The climate control system500A may be part of the HVAC system400A ofFIG. 4A. The climate control system500A includes a first feedback loop controller510A, a second feedback loop controller510B, and an actuator multiplier network550A comprising a first primary actuator multiplier G11and a second primary actuator multiplier G22. In one configuration, a first feedback loop controller510A and the first primary actuator multiplier G11, form a first feedback loop. Similarly, a second feedback loop controller510B and the second primary actuator multiplier G22form a second feedback loop. The first feedback loop receives a first target set point r1, and changes a first feedback signal y1according to the first target set point r1. Similarly, the second feedback loop receives a second target set point r2, and changes a second feedback signal y2according to the second target set point r2. The first feedback signal y1may be an electrical signal or data indicating a sensed climate (e.g., measured temperature, measured pressure, or measured humidity) of a first area of the room410A, and the second feedback signal y2may be an electrical signal or data indicating a sensed climate of a second area of the room410B. As shown inFIG. 5A, the first feedback loop and the second feedback loop are independent from each other.

The first feedback loop controller510A receives the first target set point r1and the first feedback signal y1, and generates a first control signal k1according to the first target set point r1and the first feedback signal y1. The first feedback loop controller510A may be part of the feedback loop controller435A ofFIG. 4A. The first feedback loop controller510A may include a first control error detector520A, and a first proportional-integral (PI) controller530A coupled to the first control error detector520A.

The first control error detector520A receives the first target set point r1and the first feedback signal y1, and generates a first control error signal e1based on the first target set point r1and the first feedback signal y1. In one aspect, the first control error detector520A obtains a difference between the first target set point r1and the first feedback signal y1, and generates the first control error signal e1indicating the difference. The first control error detector520A outputs the first control error signal e1to the first PI controller530A.

The first PI controller530A receives the first control error signal e1and generates the first control signal k1based on the first control error signal e1. The first PI controller530A includes an input coupled to an output of the first control error detector520A. In this configuration, the first PI controller530A may generate the first control signal k1based on present and previous components of the first control error signal e1. The first PI controller530A outputs the first control signal k1to the first primary actuator multiplier G11.

The first primary actuator multiplier G11represents an effect on the climate of a respective area in response to the first control signal k1. The first primary actuator multiplier G11may correspond to a combination of a climate actuator (e.g., damper420ofFIG. 4A) changing climate according to a control signal and a thermostat sensing the climate and generating a feedback signal according to the sensed climate. For example, the first primary actuator multiplier G11represents an effect of a temperature in the room410A ofFIG. 4Aaccording to the damper420A operated based on the first control signal k1. In one aspect, the primary actuator multiplier G11represents that the first feedback signal y1is obtained by multiplying the first control signal k1by a first primary actuator coefficient gc11. The first primary actuator coefficient gc11may be obtained through an open loop test measurement.

The second feedback loop receives the second target set point r2and the second feedback signal y2, and changes the second feedback signal y2according to the second target set point r2and the second feedback signal y2. The second feedback loop includes the second feedback loop controller510B, and the second primary actuator multiplier G22, that are configured and operate in a similar manner as the first feedback loop controller510A and the first primary actuator multiplier G11of the first feedback loop. Therefore, the detailed description thereof is omitted herein for the sake of brevity.

FIG. 5Bshows a schematic representation of a climate control system500B including two interacting feedback loops. The climate control system500B may be part of the HVAC system400B ofFIG. 4B. The components of the climate control system500B are substantially similar to the components of the climate control system500A inFIG. 5A, except the actuator multiplier network550B further includes interaction actuator multipliers G12and G21and adders560A,560B, and outputs of the primary actuator multipliers G11and G22are replaced with primary actuator output signals op1, op2, respectively. In one aspect, the interaction actuator multipliers G12and G21and adders560A,560B may not be physically implemented, but models effects of climates due to interaction between two feedback loops. The interaction between the feedback loops may occur in response to a change in a configuration of two rooms410A,410B, as shown inFIG. 4B. Such interactions as represented by these additional components may degrade control performance of the feedback loops.

The interaction actuator multiplier G12and the adder560A represent an effect of the second control signal k2on the first feedback loop, and the interaction actuator multiplier G21and the adder560B represent an effect of the first control signal k1on the second feedback loop. For example, the interaction actuator multiplier G12represents an effect on the temperature in the room410A by controlling the damper420B according to the second control signal k2. Similarly, the interaction actuator multiplier G21represents an effect on the temperature in the room410B by controlling the damper420A according to the first control signal k1. In one approach, the interaction actuator multiplier G21represents that the interaction actuator output signal oi2may be obtained by multiplying the first control signal k1by an interaction actuator coefficient gc2i. Similarly, the interaction actuator multiplier G12represents that the interaction actuator output signal oi1may be obtained by multiplying the second control signal k2by an interaction actuator coefficient gc12. The adder560A represents that the feedback signal y1is affected by the interaction actuator output signal oi1from the interaction actuator multiplier G12. Similarly, the adder560B represents that the feedback signal y2is affected by the interaction actuator output signal oi2from the interaction actuator multiplier G21. Hence, the interaction actuator multipliers G12and G21and adders560A,560B model interference between two feedback loops.

Referring toFIG. 6, illustrated is a drawing of an HVAC system600including a decoupler630to improve independent control of climates of two rooms, according to one or more embodiments. The configuration of the HVAC system600is similar to the HVAC system400B ofFIG. 4B, except that a decoupler630is added to improve control of interacting feedback loops450A,450B and the feedback loop controllers435A,435B ofFIG. 4Bare replaced with the feedback loop controllers635A,635B. Specifically, the decoupler630allows climates of the rooms410A,410B to be independently controlled despite of interaction between the rooms410A,410B. In some embodiments, different feedback loops or different components than shown inFIG. 6may be included in the HVAC system600. Moreover, additional rooms and additional feedback loops may be included in the HVAC system600.

In one or more embodiments, the decoupler630is a component that receives target set points and feedback signals, and generates modified set points. The decoupler630may be hardware, software, firmware, or any combination thereof. In one implementation, the decoupler630is coupled between thermostats425A,425B, and feedback loop controllers635A,635B. In this configuration, the decoupler630receives target set points and feedback signals from the thermostats425A,425B, modifies the target set points to obtain modified set points, and provides the modified set points to the feedback loop controllers635A,635B. The modified set points provided to the feedback loop controllers635A,635B instead of target set points allow climates of the rooms410A,410B to be independently controlled. In some embodiments, the decoupler630and the feedback loop controllers635A,635B may be integrated together. Detailed configurations and operations of the decoupler630are provided below with respect toFIGS. 7 through 11.

FIG. 7shows a schematic diagram of a climate control system700including a decoupler730, according to some embodiments. The climate control system700may be part of the HVAC system600ofFIG. 6. InFIG. 7, the climate control system700includes a decoupler730, feedback loop controllers740A,740B, and an actuator multiplier network750. The actuator multiplier network750may be same as the actuator multiplier network550ofFIG. 5B, thus interaction between two feedback loops may occur through a cross-over network of the actuator multiplier network750. In one aspect, the configuration of the climate control system700is similar to the climate control system500B ofFIG. 5B, except that the decoupler730is added and the feedback loop controllers510A,510B ofFIG. 5Bare replaced with feedback loop controllers740A,740B. In this configuration, the decoupler730receives target set point r1, r2and feedback signals y1, y2, and generates modified set points r1*, r2*. The feedback loop controllers740A,740B generate control signals u1, u2according to the modified set points r1*, r2*. The modified set points r1*, r2* may cause each of the feedback signals y1, y2from the actuator multiplier network750to depend on the target set points r1, r2, respectively, but not on the other target set points. Accordingly, the climate control system700improves control of climates in different areas despite of interacting feedback loops710A,710B.

In one or more embodiments, the decoupler730receives the target set points r1, r2and the feedback signal y1, y2, and generates the modified set points r1*, r2* based on the target set points r1, r2and the feedback signal y1, y2. In one aspect, the decoupler730includes a cross-over network that predicts interaction between two feedback loops710A,710B and modifies the target set points r1, r2to add pre-compensation components to the target set points r1, r2, according to the predicted interaction. The pre-compensation components applied to the actuator multiplier network750through the feedback loop controllers740A,740B allow the actuator multiplier network750to operate as if the interaction between the two feedback loops710A,710B does not occur. As a result, the decoupler730enables the feedback signal y1to be independent from the target set point r2, and the feedback signal y2to be independent from the target set point r1. Detailed description of implementation of the decoupler730is provided below with respect toFIGS. 8 and 9.

Although only two feedback loops are shown inFIGS. 6-7, the systems and methods described herein may be applicable to any number of interacting control loops. For example, the HVAC system600may include two interacting control loops, three interacting control loops, four interacting control loops, or more. In general, the HVAC system600may include N interacting control loops, where N≥2.

An example of a control system700for a space with two interacting control loops is described in detail with reference toFIGS. 7-11to illustrate one implementation of the present invention. In various embodiments, the control system700can be used to decouple any number N of interacting control loops or may be implemented as part of a system including more than two interacting control loops in any configuration.

Each of the control loops may include a separate controller corresponding to one of the multiple control loops. Each controller can be configured to receive a modified set point from a corresponding decoupler and a feedback signal from one of the control loops. Each controller can generate a control signal for the corresponding control loop based on the modified set point and the feedback signal for the corresponding control loop.

The decoupler can be coupled to each of the two or more controllers. The decoupler may receive target set points and feedback signals from two or more interacting control loops. The decoupler may predict an effect of each control signal for the corresponding control loop on each of the two or more interacting control loops other than the corresponding control loop, and may generate each of the modified set points based on each of the target set points and each of the feedback signals to reduce the predicted effects of each control signal on each of the other control loops.

FIG. 8shows an example schematic diagram of feedback loop controllers740A,740B ofFIG. 7, according to some embodiments. The feedback loop controllers740A,740B may be the feedback loop controllers635A,635B ofFIG. 6. In one embodiment, the feedback loop controller740A includes a control error detector810A and a proportional-derivative (PD) controller C1′. Similarly, the feedback loop controller740B includes a control error detector810B and a PD controller C2′. The components in the feedback loop controllers740A,740B are substantially similar to the feedback loop controllers510A,510B ofFIG. 5A, except that the control error detectors810A,810B receive modified set points r1*, r2*, respectively, and the PI controllers530A,530B are replaced with PD controllers C1′, C2′. Together, these components operate to control feedback loops.

Implementing the PD controllers C1′, C2′ instead of PI controllers allows the decoupler730to be implemented at the front end without intercepting control signals between the feedback loop controllers740A,740B, and the actuator multiplier network750. Specifically, implementing a decoupler before a PI controller renders a static gain to be infinite. For example, a transfer function of a PI controller includes an integrator 1/s term as shown below:

C⁡(s)=K⁡(1+1Ti⁢s)Eq.⁢(1)
where C(s) is a transfer function of a PI controller, K is a proportional coefficient, and Tiis an integral coefficient. In one aspect, the PI controller530can be converted into a PD controller as shown below:

Referring toFIG. 9, illustrated is an example schematic diagram of the decoupler730ofFIG. 7, according to some embodiments. In one embodiment, the decoupler730includes decoupling error detectors905A,905B, integrators910A,910B, and a cross-over network960including a primary decoupling multipliers T11, T22, interaction decoupler multipliers T12, T21, and decoupling adders930A,930B. The first decoupling error detector905A receives a target set point r1and a feedback signal y1, and generates an error signal e1. Similarly, the second decoupling error detector905B receives a target set point r2and a feedback signal y2, and generates an error signal e2. The integrator910A receives the error signal e1, and generates a first integrated decoupling error signal s1. Similarly, the second integrator910B receives the error signal e2, and generates a second integrated decoupling error signal s2. The cross-over network960receives the integrated decoupling error signals s1, s2and the feedback signals y1, y2, and generates modified set points r1*, r2*. Together, these components operate to predict interaction between two feedback loops, and add pre-compensation components to the target set points r1, r2to obtain the modified set points r1*, r2*.

The first decoupling error detector905A receives the first target set point r1and the first feedback signal y1, and generates a first decoupling error signal e1based on the first target set point r1and the first feedback signal y1. In one aspect, the first decoupling error detector905A obtains a difference between the first target set point r1and the first feedback signal y1, and generates the first decoupling error signal e1indicating the difference. The first decoupling error detector905A outputs the first decoupling error signal e1to the first integrator910A.

The first integrator910A receives the first decoupling error signal e1and generates the first integrated decoupling error signal s1. The first integrator910A includes an input coupled to an output of the first decoupling error detector905A and an output coupled to an input of the cross-over network960. In this configuration, the first integrator910A integrates the first decoupling error signal e1for a time period to generate the first integrated decoupling error signal s1, and provides the first integrated decoupling error signal s1to the cross-over network960. In one aspect, the first integrator910A is implemented as the integrator 1/s term from Eq. (2).

The second decoupling error detector905B receives the second target set point r2and the second feedback signal y2, and generates a second decoupling error signal e2based on the second target set point r2and the second feedback signal y2. In one aspect, the second decoupling error detector905B obtains a difference between the second target set point r2and the second feedback signal y2, and generates the second decoupling error signal e2indicating the difference. The second decoupling error detector905B outputs the second decoupling error signal e2to the second integrator910B.

The second integrator910B receives the second decoupling error signal e2and generates the second integrated decoupling error signal s2. The second integrator910B includes an input coupled to an output of the second decoupling error detector905B and an output coupled to another input of the cross-over network960. In this configuration, the second integrator910B integrates the second decoupling error signal e2for a time period to generate a second integrated decoupling error signal s2, and provides the second integrated decoupling error signal s2to the cross-over network960. In one aspect, the second integrator910B is implemented as the integrator 1/s term from Eq. (2).

The cross-over network960is a component that receives integrated decoupling error signals s1, s2and feedback signals y1, y2to generate modified set points r1*, r2*. In one implementation, the cross-over network960includes the primary decoupling multipliers T11, T22, the interaction decoupling multipliers T12, T21, and the decoupling adders930A,930B. In one configuration, the primary decoupling multiplier T11is coupled between the integrator910A and the decoupling adder930A, the primary decoupling multiplier T22is coupled between the integrator910B and the decoupling adder930B, the interaction decoupling multiplier T12is coupled between the integrator910B and the decoupling adder930A, and the interaction decoupling multiplier T21is coupled between the integrator910A and the decoupling adder930B. The decoupling adder930A adds the feedback signal y1and outputs from the primary decoupling multiplier T11and the interaction decoupling multiplier T12to generate the modified set point r1*. Similarly, the decoupling adder930B adds the feedback signal y2and outputs from the primary decoupling multiplier T22and the interaction decoupling multiplier T21to generate the modified set point r2*.

In one embodiment, each of the decoupling multipliers T11, T12, T21, T22multiplies its input with a corresponding coefficient. Specifically, the primary decoupling multiplier T11multiplies the integrated decoupling error signal s1by a first primary decoupling coefficient tc11to generate a first primary multiplied error signal sp1as an output. The interaction decoupling multiplier T12multiplies the integrated decoupling error signal s2by a first interaction decoupling coefficient tc12to generate a first interaction multiplied error signal si1as an output. Similarly, the primary decoupling multiplier T22multiplies the integrated decoupling error signal s2by a second primary decoupling coefficient tc22to generate a second primary multiplied error signal sp2as an output. The interaction decoupling multiplier T21multiplies the integrated decoupling error signal s1by a second interaction decoupling coefficient tc21to generate a second interaction multiplied error signal si2as an output.

The decoupling adders930A,930B are components that add multiplied error signals sp1, si1, si2, sp2to feedback signals y1, y2to obtain modified set points r1*, r2*. In one implementation, the decoupling adder930A includes an input to receive the first feedback signal y1, an input coupled to an output of the primary decoupling multiplier T11, an input coupled to an output of the interaction decoupling multiplier T12, and an output coupled to an input of the feedback loop controller740A. Similarly, the decoupling adder930B includes an input to receive the second feedback signal y2, an input coupled to an output of the primary decoupling multiplier T22, an input coupled to an output of the interaction decoupling multiplier T21, and an output coupled to another input of the feedback loop controller740B. In this configuration, the decoupling adder930A adds the feedback signal y1, the first primary multiplied error signal sp1, and the first interaction multiplied error signal si1to obtain the first modified set point r1*. Similarly, the decoupling adder930B adds the feedback signal y2, the second primary multiplied error signal sp2, and the second interaction multiplied error signal si2to obtain the second modified set point r2*.

In one aspect, the coefficients tc11, tc12, tc21, tc22are determined such that interaction between two feedback loops can be predicted and the modified set points can be generated when the target set points r1, r2and the feedback signals y1, y2are applied to the decoupler730. The modified set points applied to the feedback loop controllers740A,740B allow the effect of the target set point r1on the second feedback loop710B, and the effect of the target set point r2on the first feedback loop710A to be reduced. In one approach, the coefficients tc11, tc12, tc21, tc22are determined to satisfy the following equation:
y=GCTe=diag(G)C(s)e=diag(G)C′(s)(1/s)eEq. (3)
where

y=[y1y2],e=[e1e2],G=[gc11gc12gc21gc22],C′⁡(s)=[C1′⁡(s)00C2′⁡(s)],⁢T=[tc11tc12tc21tc22],
C1′(s) is a transfer function of the PD controller C1′ ofFIG. 8, and C2′(s) is a transfer function of the PD controller C1′ ofFIG. 8. That is, the coefficients tc11, tc12, tc21, tc22are selected such that (i) the feedback signal y1depends on the decoupling error signal e1but not the decoupling error signal e2, and (ii) the feedback signal y2depends on the decoupling error signal e2but not the decoupling error signal e1. In particular, the coefficients tc11, tc12, tc21, tc22may be selected to satisfy the following equation:
GC′(s)T=diag(G)C′(s), or
T=C′(s)−1G−1diag(G)C′(s)  Eq. (4).

Although the HVAC system600inFIG. 6and the climate control system700inFIG. 7are shown to control climates in two areas through two feedback loops, in other embodiments, additional areas can be controlled by modifying target set points through one or more decouplers and applying the modified set points to feedback loops, according to the disclosed principle herein.

In some embodiments, the climate control system700can dynamically adapt to a change in a configuration of a space. For example, the climate control system700can determine a change in interaction between two feedback loops (e.g., interaction actuator multipliers G12, G21ofFIG. 5B). A change in interaction between two feedback loops may be performed by open loop tests, closed loop tests or a combination of them. The climate control system700may determine a change in the interaction between the two feedback loops when automatically detecting a change in target set points, when automatically detecting a change in configuration of the space, when manually requested by a user, or periodically. Responsive to detecting the change in the interaction between the two feedback loops, the climate control system700can adjust the coefficients tc11, tc12, tc21, tc22, for example, according to Eq. (4) above.

In some embodiments, the configuration of a space is selected from a set of configurations, and the coefficients tc11, tc12, tc21, tc22are determined according to the selected configuration. For example, a wall separating two rooms410A,410B may be selectively configured according to options including “fully opened,” “half way opened,” and “fully closed.” Prior to operation or in between operations, interaction between feedback loops may be determined for each configuration, and a corresponding set of coefficients tc11, tc12, tc21, tc22may be predetermined accordingly. Additionally, a corresponding set of coefficients tc11, tc12, tc21, tc22may be stored by a memory for each configuration. During operation, a corresponding set of coefficients tc11, tc12, tc21, tc22may be retrieved according to the selected configuration of the wall (or a configuration of the space) to implement the decoupler as disclosed herein.

FIG. 10is a block diagram of a climate controller1000to implement a decoupler (e.g., decoupler630ofFIG. 6) for improving control of interacting feedback loops, according to one or more embodiments. The climate controller1000may be the AHU controller330ofFIG. 3, or a combination of the BMS controller366and the AHU controller330ofFIG. 3. In one configuration, the climate controller1000includes a communication interface1025, and a processing circuit1028. These components operate together to implement a decoupler that modifies the target set points to obtain modified set points, and applies the modified set points to interacting feedback loops for improved control. In some embodiments, the climate controller1000includes additional, fewer, or different components than shown inFIG. 10.

The communication interface1025facilitates communication of the climate controller1000with other components (e.g., dampers420A,420B, air handling unit405or thermostats425A,425B ofFIG. 6). The communication interface1025can be or include wired or wireless communications interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.). In various embodiments, communications via the communication interface1025can be direct (e.g., local wired or wireless communications) or via a communications network (e.g., a WAN, the Internet, a cellular network, etc.). For example, the communication interface1025can include an Ethernet/USB/RS232/RS485 card and port for sending and receiving data through a network. In another example, the communication interface1025can include a Wi-Fi transceiver for communicating via a wireless communications network. In another example, the communication interface1025can include cellular or mobile phone communication transceivers.

The processing circuit1028is a hardware circuit that facilitates implementation of the decoupler730ofFIG. 7. In one embodiment, the processing circuit1028includes a processor1030, and memory1040storing instructions (or program code) executable by the processor1030. In one embodiment, the instructions executed by the processor1030form software modules including a set point configuration module1060, a feedback controller configuration module1070, an interference modeling module1080, a decoupler configuration module1090, and a decoupler implementation module1095. In other embodiments, the processor1030, and the memory1040may be omitted, and these modules may be implemented as hardware modules by a reconfigurable circuit (e.g., field programmable gate array (FPGA)), an application specific integrated circuit (ASIC), or any circuitries, or a combination of software modules and hardware modules.

The set point configuration module1060is a component that obtains target set points. The set point configuration module1060may receive target set points of different rooms through the communication interface1025. The set point configuration module1060may store the received target set points, and provide the target set points to the feedback controller configuration module1070, the interference modeling module1080, the decoupler configuration module1090, and the decoupler implementation module1095.

The interference modeling module1080is a component that generates modeling of an interaction between feedback loops. In one approach, the interference modeling module1080generates model data corresponding to a first schematic representation of independent feedback loops (e.g., independent feedback loops ofFIG. 5A), and generates additional model data corresponding to a second schematic representation of interacting feedback loops (e.g., interacting feedback loops ofFIG. 5B) by adding interaction components to the first schematic representation. Moreover, the interference modeling module1080determines parameters (e.g., transfer function or gain coefficients such as interaction actuator coefficients gc12, gc21) of the interaction components (e.g., interaction actuator multipliers G12and G21). The interference modeling module1080may determine the parameters through opened loop tests, closed loop tests, or a combination of them. The interference modeling module1080may determine the parameters when automatically detecting a change in target set points, when manually requested by a user, periodically, or any combination of them.

The decoupler implementation module1095is a component that implements the decoupler (e.g., decoupler630ofFIG. 6) according to the parameters determined by the decoupler configuration module1090. The decoupler implementation module1095may generate a model data (e.g., netlist or register transfer level (RTL) code) indicating schematic representation of the decoupler and parameters for configuring the decoupler. Based on the model data, the decoupler implementation module1095may implement the decoupler on a reconfigurable hardware circuit. For example, the decoupler implementation module1095generates decoupling error detectors905, integrators910A,910B, multipliers T11, T12, T21, T22, and decoupling adders930as shown inFIG. 9, according to the parameters for configuring the decoupler. Alternatively, the decoupler implementation module1095implements the decoupler on a software module to perform functionalities of the decoupler described herein.

FIG. 11is a flow chart illustrating a process1100of improving independent controls of interacting feedback loops, according to some embodiments. The process1100may be performed by a decoupler730ofFIG. 7. In some embodiments, the process1100may be performed by other entities. In some embodiments, the process1100may include additional, fewer, or different steps than shown inFIG. 11.

The decoupler730receives a first set point, a second set point, a first feedback signal, and a second feedback signal (step1110). The first set point may be a signal or data indicating a target climate (e.g., temperature, pressure, humidity, etc.) of a first area of a space, and the second set point may be a signal or data indicating a target climate of a second area of the space. The first feedback signal may be a signal or data indicating a sensed climate of the first area of the space and the second feedback signal may be a signal or data indicating a sensed climate of the second area of the space.

The decoupler730predicts an effect of a first control signal on a second feedback loop and an effect of a second control signal on a first feedback loop (step1120), and generates a first modified set point and a second modified set point based on the predicted effects (step1130). In one aspect, the decoupler730predicts the effect of the first control signal on the second feedback loop and the effect of the second control signal on the first feedback loop, and generates pre-compensation components to reduce the predicted effects by applying the target set points and the feedback signals to a cross-over network of the decoupler730. Parameters of the cross-over network may be selected based on a model of interaction between the first feedback loop and the second feedback loop, as described above with respect toFIG. 9and Eq. (4).

The decoupler730provides the first modified set point to a first feedback loop controller to generate the first control signal and the second modified set point to the second feedback loop controller to generate the second control signal (step1140). The first feedback loop controller and the second feedback loop controller operating according to the first modified set point and the second modified set point may reduce the predicted effect of the first control signal on the second feedback loop and the predicted effect of the second control signal on the first feedback loop.

Advantageously, generating modified set points by the decoupler and operating feedback loops according to the modified set points allow a climate of each area to be independently controlled by a respective target set point and irrespective of other target set points. Moreover, implementing the decoupler as disclosed herein allows the decoupler to be implemented at the front end, without intercepting connections or signals between feedback loop controllers and climate actuators.

Referring now toFIG. 12, a pair of graphs1200A and1200B illustrating an example closed loop response of the climate control system ofFIG. 5Bare shown, according to some embodiments. Graph1200A indicates a target temperature1210A of a first room and a measured temperature1220A of the first room. Graph1200B indicates a target temperature1210B of a second room and a measured temperature1220B of the second room. Because of two interacting feedback loops, when the target temperature1210B of the second room changes at T1, temperature of the first room is affected as indicated by the measured temperature1220A at T1. Similarly, when the target temperature1210A of the first room changes at T2, temperature of the second room is affected as indicated by the measured temperature1220B at T2.

Referring now toFIG. 13, a pair of graphs1300A and1300B illustrating an example closed loop response of the climate control system ofFIG. 7including a decoupler as disclosed herein, according to some embodiments. Graph1300A indicates a target temperature1210A of the first room and a measured temperature1320A of the first room. Graph1300B indicates a target temperature1210B of the second room and a measured temperature1320B of the second room. Despite of the interacting feedback loops, an effect of the change in the target temperature1210B of the second room on the measured temperature1320A of the first room at T1is reduced by employing the disclosed decoupler, compared to when the decoupler is not implemented as shown inFIG. 12. Similarly, an effect of the change in the target temperature1210A of the first room on the measured temperature1320B of the second room at T2is reduced by employing the disclosed decoupler, compared to when the decoupler is not implemented as shown inFIG. 12.

Configuration of Exemplary Embodiments

Although the configurations as disclosed are in the context of controlling climates of different areas of a space, the principles disclosed herein can apply to any system including interacting feedback loops. For example, the system may include a vapor compression cycle for controlling climate of a space, and a decoupler as disclosed herein to reduce interaction between two interacting feedback loops within the single vapor compression cycle.