Incremental actuator with feedback control

A system for controlling a flow rate through an HVAC component is provided. The system includes a controller communicably coupled with a potentiometer and an actuator configured to drive the HVAC component between multiple positions to affect the flow rate. The controller configured to determine an actuator position setpoint based on a flow rate setpoint, drive the actuator to the actuator position setpoint using a calculated travel period, and set a current actuator position based on a voltage signal received from the potentiometer upon stopping the actuator at an expiration of the calculated travel period.

BACKGROUND

The present disclosure relates generally to actuators for use in a heating, ventilating, or air conditioning (HVAC) system and more particularly to systems and methods for controlling the position of incremental actuators with feedback control.

HVAC actuators are used to operate a wide variety of HVAC components such as air dampers, fluid valves, air handling units, and other components that are typically used in HVAC systems. For example, an actuator may be coupled to a damper in an HVAC system and may be used to drive the damper between an open position and a closed position. An HVAC actuator typically includes a motor and a drive device (e.g., a hub, a gear train, etc.) that is driven by the motor and coupled to the HVAC component.

HVAC actuators typically require accurate position feedback for use in closed-loop control systems. Some HVAC actuators use floating control with incremental actuators to open or close the actuator based on flow requirements for a variable air volume (VAV) unit. An actuator implemented with floating control drives between a minimum rotational position and a maximum rotational position based on an input signal. One disadvantage of this method for actuator control is that the actual position of the actuator is not known, and over time, the actual position can differ from a calculated position. This effect is known as drift. Other HVAC actuators are proportional actuators that control the position of the drive device according to a value of DC voltage received. However, proportional actuators can require additional wiring to be installed and are generally more expensive than incremental actuators. It would be desirable to provide a system and method for controlling the more economical incremental actuator that provides accurate calculated positions for the actuator and requires no additional wiring during installation.

SUMMARY

One implementation of the present disclosure is a system for controlling a flow rate through an HVAC component. The system includes a controller communicably coupled with a potentiometer and an actuator configured to drive the HVAC component between multiple positions to affect the flow rate. The controller configured to determine an actuator position setpoint based on a flow rate setpoint, drive the actuator to the actuator position setpoint using a calculated travel period, and set a current actuator position based on a voltage signal received from the potentiometer upon stopping the actuator at an expiration of the calculated travel period.

In some embodiments, the flow rate setpoint is based on a zone temperature error. In other embodiments, the system includes a temperature sensor communicably coupled to the controller. In still further embodiments, the zone temperature error is based on a zone temperature setpoint and a zone temperature measurement from the temperature sensor.

In some embodiments, the potentiometer is coupled to a gear train of the actuator. In other embodiments, the potentiometer is coupled to an external analog output of the actuator.

In some embodiments, the HVAC component is a damper. In other embodiments, the HVAC component is a valve.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is lower than a low endpoint threshold, and in response to a determination that the voltage signal is not lower than the low endpoint threshold, determining whether the voltage signal is higher than a high endpoint threshold. In response to a determination that the voltage signal is not higher than the high endpoint threshold, setting the current actuator position includes calculating the current actuator position based on the voltage signal, the low endpoint threshold, and the high endpoint threshold.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is lower than a low endpoint threshold, and in response to a determination that the voltage signal is lower than the low endpoint threshold, resetting the low endpoint threshold to the voltage signal and calculating the current actuator position based on the low endpoint threshold.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is higher than a high endpoint threshold, and in response to a determination that the voltage signal is higher than the high endpoint threshold, resetting the high endpoint threshold to the voltage signal and calculating the current actuator position based on the high endpoint threshold.

In some embodiments, the calculated travel period is based on a stroke time of the actuator between a low endpoint position and a high endpoint position.

Another implementation of the present disclosure is a method for controlling a flow rate through an HVAC component. The method includes determining an actuator position setpoint based on a flow rate setpoint, driving an actuator coupled to the HVAC component to the actuator position setpoint using a calculated travel period, and setting a current actuator position based on a voltage signal received from a potentiometer coupled to the actuator upon stopping the actuator at an expiration of the calculated travel period.

In some embodiments, the flow rate setpoint is based on a zone temperature error. In other embodiments, the zone temperature error is based on a zone temperature setpoint and a zone temperature measurement from a temperature sensor.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is lower than a low endpoint threshold, and in response to a determination that the voltage signal is not lower than the low endpoint threshold, determining whether the voltage signal is higher than a high endpoint threshold. In response to a determination that the voltage signal is not higher than the high endpoint threshold, setting the current actuator position includes calculating the current actuator position based on the voltage signal, the low endpoint threshold, and the high endpoint threshold.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is lower than a low endpoint threshold, and in response to a determination that the voltage signal is lower than the low endpoint threshold, resetting the low endpoint threshold to the voltage signal and calculating the current actuator position based on the low endpoint threshold.

In some embodiments, setting the current actuator position based on the voltage signal received from the potentiometer includes determining whether the voltage signal is higher than a high endpoint threshold, and in response to a determination that the voltage signal is higher than the high endpoint threshold, resetting the high endpoint threshold to the voltage signal and calculating the current actuator position based on the high endpoint threshold.

Yet another implementation of the present disclosures is a system for controlling an airflow rate through a damper. The system includes a controller communicably coupled with a potentiometer and an incremental actuator configured to drive the damper between multiple positions to affect the airflow rate. The controller is configured to determine a position setpoint for the incremental actuator based on a zone temperature error, operate the incremental actuator to the position setpoint, receive a feedback signal from the potentiometer once the incremental actuator has stopped changing position, and overwrite a calculated position of the incremental actuator with a current position of the incremental actuator based on the feedback signal.

DETAILED DESCRIPTION

Overview

Before turning to the FIGURES, which illustrate the embodiments in detail, it should be understood that the disclosure is not limited to the details or methodology set forth in the description or illustrated in the FIGURES. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

The embodiments and implementation of the systems and methods disclosed herein improve current HVAC systems by providing an incremental actuator with feedback control. For example, the incremental actuator may be a damper actuator. In other embodiments, the incremental actuator may be a valve actuator, a fan actuator, a pump actuator, or any other type of actuator that can be used in a HVAC system that uses incremental or floating control for the actuator.

The incremental actuator includes a potentiometer to measure the position of the incremental actuator. In some embodiments, the potentiometer is incorporated into the gear train for the incremental actuator. In other embodiments, the potentiometer is external to the incremental actuator (e.g., wired to an external analog input of the actuator). The potentiometer provides feedback to the controller corresponding to the position of the incremental actuator by providing a voltage signal proportional to the position. A position feedback controller converts the voltage signal from the potentiometer to a position value. Furthermore, the position feedback controller auto-calibrates the position values by adjusting the voltage signal limits as each of the actuator endpoints or end stops is reached. The high and low voltage values can be measured and can correspond with the endpoints of the incremental actuator (e.g., from 0% to 100%, where 0% may correspond with a fully closed damper and 100% may correspond with a fully open damper). The position feedback controller may further perform one or more processes based on potentiometer feedback to calculate the current position of the incremental actuator, overcoming the effect of drift.

Advantageously, incremental actuators are more affordable for consumers to purchase and can utilize existing controllers (e.g., modular assemblies for VAV controllers) for ease of installation. By providing an accurate current position of the actuator, the incremental actuator with feedback control can be utilized in air handling unit (AHU) applications and may aid in optimizing AHU fan speed and cold air temperature parameters, to name a few examples. Additional features and advantages of the present invention are described in greater detail below.

Building Management System and HVAC System

Referring now toFIG.2, a block diagram of a waterside system200is shown, according to an exemplary embodiment. In various embodiments, waterside system200may supplement or replace waterside system120in HVAC system100or may be implemented separate from HVAC system100. When implemented in HVAC system100, waterside system200may include a subset of the HVAC devices in HVAC system100(e.g., boiler104, chiller102, pumps, valves, etc.) and may operate to supply a heated or chilled fluid to AHU106. The HVAC devices of waterside system200may be located within building10(e.g., as components of waterside system120) or at an offsite location such as a central plant.

InFIG.2, waterside system200is shown as a central plant having a plurality of subplants202-212. Subplants202-212are shown to include a heater subplant202, a heat recovery chiller subplant204, a chiller subplant206, a cooling tower subplant208, a hot thermal energy storage (TES) subplant210, and a cold thermal energy storage (TES) subplant212. Subplants202-212consume resources (e.g., water, natural gas, electricity, etc.) from utilities to serve the thermal energy loads (e.g., hot water, cold water, heating, cooling, etc.) of a building or campus. For example, heater subplant202may be configured to heat water in a hot water loop214that circulates the hot water between heater subplant202and building10. Chiller subplant206may be configured to chill water in a cold water loop216that circulates the cold water between chiller subplant206and building10. Heat recovery chiller subplant204may be configured to transfer heat from cold water loop216to hot water loop214to provide additional heating for the hot water and additional cooling for the cold water. Condenser water loop218may absorb heat from the cold water in chiller subplant206and reject the absorbed heat in cooling tower subplant208or transfer the absorbed heat to hot water loop214. Hot TES subplant210and cold TES subplant212may store hot and cold thermal energy, respectively, for subsequent use.

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.) may be used in place of or in addition to water to serve the thermal energy loads. In other embodiments, subplants202-212may 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.

Each of dampers316-320may be operated by an actuator. For example, exhaust air damper316may be operated by actuator324, mixing damper318may be operated by actuator326, and outside air damper320may be operated by actuator328. Actuators324-328may communicate with an AHU controller330via a communications link332. Actuators324-328may receive control signals from AHU controller330and may provide feedback signals to AHU controller330. Feedback signals may include, for example, an indication of a current actuator or damper position, an amount of torque or force exerted by the actuator, diagnostic information (e.g., results of diagnostic tests performed by actuators324-328), status information, commissioning information, configuration settings, calibration data, and/or other types of information or data that may be collected, stored, or used by actuators324-328. AHU controller330may be an economizer controller configured to use one or more control algorithms (e.g., state-based algorithms, extremum seeking control (ESC) algorithms, proportional-integral (PI) control algorithms, proportional-integral-derivative (PID) control algorithms, model predictive control (MPC) algorithms, feedback control algorithms, etc.) to control actuators324-328.

Cooling coil334may receive a chilled fluid from waterside system200(e.g., from cold water loop216) via piping342and may return the chilled fluid to waterside system200via piping344. Valve346may 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 valves346and352may be controlled by an actuator. For example, valve346may be controlled by actuator354and valve352may be controlled by actuator356. Actuators354-356may communicate with AHU controller330via communications links358-360. Actuators354-356may receive control signals from AHU controller330and may provide feedback signals to 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 controller330may also receive a measurement of the temperature of building zone306from a temperature sensor364located in building zone306.

Client device368may include one or more human-machine interfaces or client interfaces (e.g., graphical user interfaces, reporting interfaces, text-based computer interfaces, client-facing web services, web servers that provide pages to web clients, etc.) for controlling, viewing, or otherwise interacting with HVAC system100, its subsystems, and/or devices. Client device368may be a computer workstation, a client terminal, a remote or local interface, or any other type of user interface device. Client device368may be a stationary terminal or a mobile device. For example, client device368may be a desktop computer, a computer server with a user interface, a laptop computer, a tablet, a smartphone, a PDA, or any other type of mobile or non-mobile device. Client device368may communicate with BMS controller366and/or AHU controller330via communications link372.

Each of building subsystems428may include any number of devices, controllers, and connections for completing its individual functions and control activities. HVAC subsystem440may include many of the same components as HVAC system100, as described with reference toFIGS.1-3. For example, HVAC subsystem440may include and number of chillers, heaters, handling units, economizers, field controllers, supervisory controllers, actuators, temperature sensors, and/or other devices for controlling the temperature, humidity, airflow, or other variable conditions within building10. Lighting subsystem442may include any number of light fixtures, ballasts, lighting sensors, dimmers, or other devices configured to controllably adjust the amount of light provided to a building space. Security subsystem438may include occupancy sensors, video surveillance cameras, digital video recorders, video processing servers, intrusion detection devices, access control devices and servers, or other security-related devices.

Still referring toFIG.4, BMS controller366is shown to include a communications interface407and a BMS interface409. Interface407may facilitate communications between BMS controller366and external applications (e.g., monitoring and reporting applications422, enterprise control applications426, remote systems and applications444, applications residing on client devices448, etc.) for allowing user control, monitoring, and adjustment to BMS controller366and/or subsystems428. Interface407may also facilitate communications between BMS controller366and client devices448. BMS interface409may facilitate communications between BMS controller366and building subsystems428(e.g., HVAC, lighting security, lifts, power distribution, business, etc.).

Memory408(e.g., memory, memory unit, storage device, etc.) may include one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage, etc.) for storing data and/or computer code for completing or facilitating the various processes, layers and modules described in the present application. Memory408may be or include volatile memory or non-volatile memory. Memory408may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present application. According to an exemplary embodiment, memory408is communicably connected to processor406via processing circuit404and includes computer code for executing (e.g., by processing circuit404and/or processor406) one or more processes described herein.

In some embodiments, BMS controller366is implemented within a single computer (e.g., one server, one housing, etc.). In various other embodiments BMS controller366may be distributed across multiple servers or computers (e.g., that can exist in distributed locations). Further, whileFIG.4shows applications422and426as existing outside of BMS controller366, in some embodiments, applications422and426may be hosted within BMS controller366(e.g., within memory408).

Enterprise integration layer410may be configured to serve clients or local applications with information and services to support a variety of enterprise-level applications. For example, enterprise control applications426may be configured to provide subsystem-spanning control to a graphical user interface (GUI) or to any number of enterprise-level business applications (e.g., accounting systems, user identification systems, etc.). Enterprise control applications426may also or alternatively be configured to provide configuration GUIs for configuring BMS controller366. In yet other embodiments, enterprise control applications426can work with layers410-420to optimize building performance (e.g., efficiency, energy use, comfort, or safety) based on inputs received at interface407and/or BMS interface409.

Building subsystem integration layer420may be configured to manage communications between BMS controller366and building subsystems428. For example, building subsystem integration layer420may receive sensor data and input signals from building subsystems428and provide output data and control signals to building subsystems428. Building subsystem integration layer420may also be configured to manage communications between building subsystems428. Building subsystem integration layer420translates communications (e.g., sensor data, input signals, output signals, etc.) across a plurality of multi-vendor/multi-protocol systems.

Demand response layer414may further include or draw upon one or more demand response policy definitions (e.g., databases, XML files, etc.). The policy definitions may be edited or adjusted by a user (e.g., via a graphical user interface) so that the control actions initiated in response to demand inputs may be tailored for the user's application, desired comfort level, particular building equipment, or based on other concerns. For example, the demand response policy definitions can specify which equipment may be turned on or off in response to particular demand inputs, how long a system or piece of equipment should be turned off, what setpoints can be changed, what the allowable set point adjustment range is, how long to hold a high demand setpoint before returning to a normally scheduled setpoint, how close to approach capacity limits, which equipment modes to utilize, the energy transfer rates (e.g., the maximum rate, an alarm rate, other rate boundary information, etc.) into and out of energy storage devices (e.g., thermal storage tanks, battery banks, etc.), and when to dispatch on-site generation of energy (e.g., via fuel cells, a motor generator set, etc.).

Incremental Actuator with Feedback Control

Referring now toFIGS.5-7, systems and methods to control an incremental actuator with position feedback are shown, according to some embodiments. In brief overview,FIG.5is a block diagram of an incremental actuator interacting with a controller.FIG.6is a flow diagram of a process for determining the calculated position of an incremental actuator.FIG.7is a flow diagram of a process for controlling an incremental actuator using position feedback from a potentiometer.

Referring now toFIG.5, a block diagram of an incremental actuator and feedback control system500is depicted. In various embodiments, the incremental actuator and feedback control system500may be used in the HVAC system ofFIG.1, the waterside system ofFIG.2, the airside system ofFIG.3, or the BMS ofFIG.4to control a HVAC component. Incremental actuator and feedback control system500is shown to include a controller502that is communicably coupled to a damper actuator514and a temperature sensor518. In some embodiments, controller502can be implemented within a single computer (e.g., one server, one housing, etc.). In other embodiments, controller502can be distributed across several servers or computers (e.g., that can exist in distributed locations). Furthermore, applications that are carried out by system500may exist outside controller502or may be hosted within controller502(e.g., within memory).

Damper actuator514can be configured as an incremental actuator that drives a damper used within an airside system (e.g., airside system300, as described in detail with reference toFIG.3). In other embodiments, the incremental actuator drives other components of an HVAC system, such as a fan, a valve, or a pump. Damper actuator514can be connected to controller502and potentiometer516to communicate information on the position of the incremental actuator. In some embodiments, damper actuator514is powered by an AC power supply (e.g., the electric utility of building10) through a wired interface.

Controller502is shown to include various components or circuits, including, but not limited to a zone temperature circuit504, a close output circuit506, a position feedback controller circuit508, and an open output circuit510. Each of the circuits504-510may be a subcomponent of a hardware manager520. Zone temperature504can be configured to store information on temperatures for a zone (i.e., a portion of a building, such as a room or a floor) within controller502. Furthermore, zone temperature504may contain applications that calculate a difference or error value between a desired temperature and a calculated temperature. The desired zone temperature may be received from a supervisory controller, from a thermostat or other user device, or from any other source. In some embodiments, this calculation can then be used to determine whether the zone needs more cold airflow to lower the temperature of the room or if the zone is too cold and needs an increase in temperature. Thus, zone temperature504can be used for defining the desired airflow to a zone within a building (e.g., building10). Temperature sensor518can be any type of temperature sensor and can be configured to provide real time information to the actuator controller on temperatures of a zone. In some embodiments, temperature sensor518provides data points of air temperature in the zone that include a measured data value indicating the temperature measured by the temperature sensor. The data points from temperature sensor518can also include timestamps of when the temperature was measured by the temperature sensor.

Still referring toFIG.5, close output506can be configured to send a signal from the controller to an incremental actuator (e.g., damper actuator514) to close the actuator a certain amount. Close output506may contain information in controller502on how much the position of the incremental actuator may close in order to maintain a desired airflow. For example, close output may contain a voltage value that corresponds with a position of damper actuator514, such that the incremental actuator will continue to close until it reaches that position. Open output510can also be configured to send a signal from a controller to an incremental actuator (e.g., damper actuator514), but instead of closing the position, the signal may provide information to open the position a certain amount. In some embodiments, closing the incremental actuator completely means the actuator has a corresponding position value of 0%, while opening the incremental actuator completely means the actuator has a corresponding position value of 100%.

Potentiometer516can be configured to produce a voltage signal that is proportional to the position of the incremental actuator (e.g., 0.0-100% open) and to output the voltage signal to the position feedback controller508of the incremental actuator. In some embodiments, potentiometer516is attached to a gear train of the incremental actuator in order to provide position feedback to the position feedback controller508through an internal connection to an analog to digital converter (ADC). In other embodiments, potentiometer516is external to the incremental actuator514(e.g., wired to an external analog input of the actuator).

The position feedback controller508may be responsible for processing inputs and outputs of the actuator controller. The position feedback controller508may also be programmed to execute a hardware manager application that converts voltage values from potentiometer516to position values and provides an actual position of the incremental actuator to a control primitive. In some embodiments, the control primitive is a Position Adjust Output (PAO). The control primitive PAO can be responsible for managing the position of the incremental actuator (e.g., damper actuator514). The hardware manager520also can auto-calibrate the position value by adjusting signal limits as each endpoint of the incremental actuator is reached. Further details of this auto-calibration process are included below with reference toFIG.6. In order to prevent operational failure of the incremental actuator, if the position feedback signal from the potentiometer (e.g., potentiometer516) is lost, the actuator continues using incremental control without position feedback. The PAO can be configured to establish a connection to the hardware manager520and to ask for a valid position feedback signal from the potentiometer. If the position feedback signal exists and is also reliable, the hardware manager520can send updates of the position value to a current instance of the PAO object.

Referring now toFIG.6, a flow diagram of process600for determining the calculated position of an incremental actuator is shown, according to some embodiments. Process600may be completed by various components of system500, as described in detail with reference toFIG.5. In some embodiments, process600can be executed in part by an application associated with BMS400. Process600provides an overview of a way to determine the current position of an incremental actuator using feedback from a potentiometer. Process600can be used for HVAC systems, such as airside system300, described in detail with reference toFIG.3. In some embodiments, process600is performed each time the incremental actuator stops.

The calculated position of the incremental actuator allows the HVAC system (e.g., HVAC system100, described in detail with reference toFIG.1) to open and close the actuator to satisfy airflow requirements while preventing a drift effect. The drift effect occurs when an actuator is open and closed without attention to the actual position of the actuator. The inattention to the actual position of the actuator results in inaccurate information of the position of the actuator, such that the actual current position of the actuator may vary greatly (“drift”) from the calculated position. By continually updating information on the position of the incremental actuator, process600can inhibit drift effects in incremental actuators.

Furthermore, knowledge of the position of the actuator can be useful in newer AHU applications. For example, the actuator position can be used to optimize AHU fan speed and cold air temperatures in HVAC systems. However, the operation of the incremental actuator does not depend on an actuator position feedback signal from the potentiometer being received and the completion of process600. For example, if the feedback signal from the potentiometer on the actuator position feedback is lost during process600, the actuator can continue to operate normally using incremental control to meet the airflow requirements.

Process600is shown to include receiving a measured voltage from a potentiometer (step602) and determining if the measured voltage signal from the potentiometer position feedback is less than a low endpoint threshold of the incremental actuator (step604). In some embodiments, a potentiometer (e.g., potentiometer516) is configured to produce a voltage signal that is proportional to a position of the incremental actuator. After the actuator controller (e.g., controller502) receives the position feedback from the potentiometer, the hardware manager520processes the input and converts the measured voltage to a corresponding percentage value of the incremental actuator position. For example, if the measured voltage signal is equivalent to the lower endpoint threshold of the actuator position, the hardware manager520converts the measured voltage value to a position value of 0%. The value of the position for the incremental actuator may then be stored in memory of the position feedback controller508to be used for decisions to open or close the actuator based on zone temperature feedback. The low position endpoint may also be stored in memory in position feedback controller508.

If the measured voltage from the potentiometer is found to be less than the low endpoint threshold of the incremental actuator, process600is shown to set the low endpoint to equal the measured voltage from the potentiometer feedback (step608). The low endpoint of the actuator position may be stored in position feedback controller508and rewritten by controller502to equal the position from the most recent measured voltage that is less than the voltage value for the current low endpoint. After the low endpoint threshold has been updated to be the position corresponding to the measured voltage reading from the potentiometer position feedback, process600continues to step610.

However, if the measured voltage from the potentiometer is found to be greater than the low endpoint threshold of the incremental actuator, process600is shown to proceed with step606before determining if the voltage from the potentiometer is greater than the high endpoint threshold of the incremental actuator (step610). In some embodiments, controller502uses the hardware manager520to compare voltages for the most recent potentiometer position feedback value and the low endpoint position value. After determining that the low endpoint position voltage value is still lower than the most recent voltage value measured from position feedback, controller502can retain the current low endpoint position (step606) before continuing to step610of process600.

Process600is further shown to include determining if the measured voltage signal from potentiometer position feedback is greater than the high endpoint threshold of the incremental actuator (step610). If the measured voltage from the potentiometer is found to be greater than the high endpoint of the incremental actuator in step610, process600is shown to proceed with setting the high endpoint threshold of the incremental actuator equal to the value of the measured voltage from feedback (step614). For example, if the measured voltage signal is equivalent to the higher endpoint of the actuator position, the hardware manager520converts the measured voltage value to a position value of 100%. The high endpoint of the actuator position may be stored in position feedback controller508and rewritten by controller502to equal the position from the most recent potentiometer position feedback that is greater than the voltage value for the current high endpoint threshold. After the high endpoint has been set to the measured voltage reading from the potentiometer position feedback, process600continues to step616to calculate the position of the incremental actuator. However, if the voltage from potentiometer feedback is found to be lower than the current high endpoint, process600is shown to proceed with retaining the current high endpoint (step612) before calculating the position of the incremental actuator in step616.

Process600is shown to include calculating the position of the incremental actuator from the endpoints of the incremental actuator and measured voltage from potentiometer position feedback (step616). In some embodiments, step616is accomplished by controller502and values stored in position feedback controller508. For example, the hardware manager520can compare the voltage values for the low position endpoint and high position endpoint with the measured voltage value from potentiometer516to calculate what percentage from the low position endpoint to the high position endpoint the measured voltage value falls. Based on that comparison, controller502can calculate the percentage of total distance, from one endpoint to the other endpoint, the position of the incremental actuator is away from the low endpoint position.

Referring now toFIG.7, a flow diagram of process700for controlling the incremental actuator ofFIG.5using feedback from a potentiometer is shown, according to some embodiments. In some embodiments, process700is completed by multiple components of system500, described with reference toFIG.5, to improve management of HVAC systems, such as airside system300. Steps within process700may occur after or concurrently with process600and may use information produced by process600to control the incremental actuator (e.g., damper actuator514) within the HVAC system.

Process700is shown to include determining a desired flow rate based on a zone temperature error (step702). In various embodiments, process700may be performed every time the zone temperature error exceeds a certain threshold (e.g., the zone temperature error exceeds 0.5 degrees), or every time controller502receives a new zone temperature setpoint (e.g., a user changes a thermostat setting for a building zone). Controller502may be configured to determine a temperature error and a desired flow rate for an airside system using information from a temperature sensor (e.g., temperature sensor518), which may be stored and processed in zone temperature504. For example, temperature sensor518can be configured to communicate to controller502that a zone has a current temperature of 79° F., whereas the desired temperature setpoint of the zone is 72° F. Thus, the temperature error of the zone is 7° F. and controller502can be configured to determine that there needs to be an increase in airflow to the zone in order to cool down the temperature.

Process700is shown to include calculating a desired damper actuator position based on the desired flow rate setpoint through the damper (step704). Controller502and other components of system500, described in detail with reference toFIG.5, can be used in completing step704. For example, if the temperature of a zone is greater than the desired temperature setpoint, an increase in airflow to the zone may be used to lower the temperature of the zone. Therefore, a controller (e.g., controller502) can determine that the damper should be opened more in order to permit more air to flow through to the zone and to calculate the actuator position setpoint that would allow the correct amount of air to flow into the zone.

Process700is shown to include updating the current position based on how much time has elapsed since the actuator began moving (step706). If the actuator has not yet begun to move, a controller (e.g., controller502) can utilize the actuator's last calculated position. If the actuator has begun moving, the controller can calculate the actuator's current position based on the stroke time of the actuator and the commanded actuator position setpoint. For example, if the actuator has a stroke time of 100 seconds to move from a low endpoint or fully closed (i.e., 0% open) position to a high endpoint or fully open (i.e., 100% open) position, if the actuator has been moving for 10 seconds from a fully closed position, the controller will calculate that the actuator is in a 10% open position.

Process700is further shown to include determining whether the incremental actuator must begin to move or keep moving in order to reach the actuator position setpoint (step708). In some embodiments, this is accomplished by comparing the calculated current position, determined in step706, with the desired position setpoint, determined in step704and determining whether the current position is equal to the desired position setpoint. For example, a controller (e.g., controller502) can use information stored about position feedback relating to the current position and calculate a difference between the current position and the desired position. Then, based on the difference between the current position and the desired position, the controller may determine whether an incremental actuator for the damper (e.g., damper actuator514) is going to open more, close more, or not make any changes to position. For example, if the desired position is fully open and the current position is only half open, then a movement is required and the controller can send a signal to the damper incremental actuator to increase its position to be more open.

If actuator movement is required, process700is shown to include starting the actuator (step710). In some embodiments, starting the actuator may include a controller (e.g., controller502) commanding open or close output with remaining onTime (step710). OnTime can be a variable the controller sends to the incremental actuator that informs the actuator how long to remain “on” while changing position. In some embodiments, the primitive control PAO from the controller (e.g., controller502) for the incremental damper actuator commands the damper to close a specific amount using close output506. In other embodiments, the next movement required is to open the damper more, thus the controller commands the incremental actuator to open more than its current position using open output510. PAO can incrementally move the actuator to its new position, updating its calculated position as it moves based on the elapsed travel time since the actuator began moving. As soon as the onTime is over, the incremental actuator can be considered to be “off” and can stop movement, signaling that movement is no longer necessary in order to change the position. Process700can then return to step702to determine whether the zone temperature error persists.

If a movement is not required at step708, process700is shown to include stopping the incremental actuator (step712). The controller of the incremental actuator, in this case an incremental damper actuator (e.g., damper actuator514), can send a signal to the actuator to stop any further movements to change the position. For example, once the incremental actuator has changed the position to be equal or close to the calculated desired position, the incremental actuator no longer needs to open or close more. In some embodiments, the controller (e.g., controller502) sends a signal to stop the incremental actuator via a communications interface that is similar to communications interface407of the building management system, described in detail with reference toFIG.4.

Once the actuator is stopped after step712, process700is shown to include setting the current position to a feedback value (step714). In some embodiments, the current position of the incremental damper actuator (e.g., damper actuator514), is set equal to the feedback value from a potentiometer (e.g., potentiometer516) by the Hardware Manager of the position feedback controller508. Furthermore, the feedback value can be a voltage signal produced by the potentiometer that corresponds with a position of the actuator based on the voltages for two endpoint positions. The hardware manager520can overwrite the calculated position of the actuator based on the travel time with the new current position. To update the current position, the PAO can verify that a feedback signal is being received by the controller and that the signal is reliable before the hardware manager520sends value updates. The current position of the actuator can be stored in memory within controller502to be accessed later by the controller. In some embodiments, controller502contains memory that is similar to memory408of the BMS controller, described in detail with reference toFIG.4. After the current position of the actuator is updated and saved, it can be used in applications where knowing the actual position of the incremental actuator (e.g., damper actuator514) can be beneficial, such as in AHUs to optimize fan speed or optimize cold air temperature.

Configuration of Exemplary Embodiments