Valve assembly with pressure disturbance rejection and fault detection and diagnosis

1. A pressure disturbance rejection valve assembly configured to modify an environmental condition of a building, the valve assembly comprising:

a valve configured to regulate a flow rate of a fluid through a conduit;

a flow rate sensor configured to measure the flow rate of the fluid through the conduit and provide a flow rate measurement indicating the flow rate of the fluid through the conduit;

an actuator comprising:

a motor;

a drive device configured to be driven by the motor and coupled to the valve for driving the valve within a range of positions;

a position sensor configured to measure a rotational position of the drive device and provide a rotational position measurement indicating the rotational position of the drive device;

a communications mechanism configured to receive a flow rate setpoint from an external control device of an outer control loop; and

a processing circuit coupled to the motor, the communications mechanism, the position sensor, and the flow rate sensor, the processing circuit configured to:

determine an actuator position setpoint using a feedback control mechanism based on the flow rate setpoint and the flow rate measurement;

operate the motor to drive the drive device to the actuator position setpoint;

detect a fault condition based at least in part on the actuator position setpoint and a comparison of the flow rate setpoint and the flow rate measurement; and

perform a fault mitigation action in response to detection of the fault condition.

2. The valve assembly of claim 1 , wherein the communications mechanism is configured to receive the flow rate setpoint as at least one of an analog input signal or a digital input signal.

3. The valve assembly of claim 1 , wherein the feedback control mechanism is a cascaded feedback control mechanism.

4. The valve assembly of claim 1 , wherein the fault condition is a position fault comprising a difference between the actuator position setpoint and the rotational position measurement exceeding a position error value.

5. The valve assembly of claim 1 , wherein the fault condition is a low flow fault.

6. The valve assembly of claim 5 , wherein the low flow fault comprises the flow rate measurement being less than a flow rate setpoint value when the rotational position measurement indicates that the valve is in a fully open position.

7. The valve assembly of claim 1 , wherein the fault condition is a no flow fault.

8. The valve assembly of claim 7 , wherein the no flow fault comprises the flow rate measurement being less than a minimum rated flow rate value when the rotational position measurement indicates that the valve exceeds a minimum open position.

9. The valve assembly of claim 1 , wherein the fault condition is a leaky valve fault.

10. The valve assembly of claim 9 , wherein the leaky valve fault comprises the flow rate measurement exceeding a leaky flow rate value when the rotational position measurement indicates that the valve is in a fully closed position.

11. The valve assembly of claim 1 , wherein the fault mitigation action comprises at least one of transmitting a fault notification message, activating a system alarm, logging an entry in a system log, illuminating a fault indicator light, or operating in a fault tolerant control mode.

12. A method for controlling a pressure disturbance rejection valve assembly in an HVAC system, the method comprising:

determining an actuator position setpoint of an actuator based on a flow rate setpoint and a flow rate measurement;

driving the actuator to the actuator position setpoint, wherein the actuator is coupled to a valve in order to drive the valve within a range of positions;

measuring a flow rate of fluid through the valve;

detecting a fault condition based at least in part on the actuator position setpoint and a comparison of the flow rate setpoint and the flow rate measurement; and

performing a fault mitigation action in response to detection of the fault condition.

13. The method of claim 12 , wherein the fault condition is a position fault comprising a difference between the actuator position setpoint and a rotational position measurement exceeding a position error value.

14. The method of claim 12 , wherein the fault condition is a low flow fault.

15. The method of claim 14 , wherein the low flow fault comprises the flow rate measurement being less than a flow rate setpoint value when a rotational position measurement indicates that the valve is in a fully open position.

16. The method of claim 12 , wherein the fault condition is a no flow fault.

17. The method of claim 16 , wherein the no flow fault comprises the flow rate measurement being less than a minimum rated flow rate value when a rotational position measurement indicates that the valve exceeds a minimum open position.

18. The method of claim 12 , wherein the fault condition is a leaky valve fault.

19. The method of claim 18 , wherein the leaky valve fault comprises the flow rate measurement exceeding a leaky flow rate value when a rotational position measurement indicates that the valve is in a fully closed position.

20. An actuator, comprising:

a motor;

a drive device configured to be driven by the motor;

a position sensor configured to measure a rotational position of the drive device and provide a rotational position measurement indicating the rotational position of the drive device;

a communications mechanism configured to receive a flow rate setpoint from an external control device of an outer control loop; and

a processing circuit coupled to the motor, the communications mechanism, and the position sensor, the processing circuit configured to:

determine an actuator position setpoint using a feedback control mechanism based on the flow rate setpoint and a flow rate measurement from a flow sensor;

operate the motor to drive the drive device to the actuator position setpoint;

detect a fault condition based at least in part on the actuator position setpoint and a comparison of the flow rate setpoint and the flow rate measurement;

transition the actuator to a fault state based on determining the fault condition exists for at least a threshold period of time; and

perform a fault mitigation action in response to transitioning the actuator to the fault state.