Control systems for valve actuators, valve actuators and related systems and methods

1. A valve system comprising:

a valve actuator for controlling a position of a valve element in a valve in order to control flow through at least a portion of the valve; and

a control system for controlling the valve actuator, the control system configured to:

instruct the valve actuator to move the valve element toward an unobstructed first position in the valve to enable fluid flow through the at least a portion of the valve;

instruct the valve actuator to move the valve element from the unobstructed first position to a second closed position in the valve to reduce the fluid flow through the at least a portion of the valve, wherein the valve element is at least partially seated to reduce the fluid flow in the valve in the second closed position;

monitor at least one characteristic of the valve system during movement of the valve element to the second closed position comprising a hard stop;

determine a drift of a sensed location of the second closed position based on the monitored at least one characteristic of the valve system by calculating a difference between a previously recorded closed position and the second closed position; and

during each movement of the valve element, maintain a predetermined location of the unobstructed first position while actively adjusting the location of the second closed position comprising the hard stop each time the drift in the sensed location of the second closed position is detected.

2. The valve system of claim 1 , wherein the control system is further configured to:

reduce a rate of speed of the valve element as the valve element travels to the second closed position at a selected point; and

update the selected point for the reducing of the speed of the valve element based on the determined drift of the second closed position.

3. The valve system of claim 1 , wherein the control system is further configured to at least one of:

determine that the second closed position of the valve element has drifted to a location relatively closer to the first position; or

determine that the second closed position of the valve element has drifted to a location relatively further away from the first position.

4. The valve system of claim 1 , wherein the control system is further configured to update a deacceleration point based on the determined drift.

5. The valve system of claim 1 , wherein the control system is further configured to, at a predetermined location along a path of the valve element, switch to monitoring another characteristic of the valve system that is distinct from the at least one characteristic as the valve element approaches and reaches the second closed position along the path.

6. The valve system of claim 1 , wherein the at least one characteristic comprises at least one of torque of the valve actuator, current of the valve actuator, rate of flow through the valve, flow type through the valve, position of the valve element, or a pressure in the valve.

7. The valve system of claim 1 , wherein the control system is further configured to monitor at least another characteristic of the valve system during movement of the valve element back to the first position.

8. The valve system of claim 7 , wherein the at least another characteristic comprises at least one of flow through the valve, flow type through the valve, position of the valve element, or a pressure in the valve.

9. The valve system of claim 1 , wherein the unobstructed first position comprises a position of the valve element that lacks a hard stop, and wherein the second closed position comprises a hard stop.

10. The valve system of claim 1 , wherein the control system is further configured to:

update a location of the second closed position based on the detected drift; and

update a location of a change in speed of the valve element based on the detected drift.

11. The valve system of claim 1 , wherein the control system is further configured to generate an alarm or alert when the drift is outside of a selected range of drift values.

12. The valve system of claim 1 , wherein the second closed position comprises a closed seated position, and wherein the control system is configured to move the valve element into contact with a seat of the valve system and then to force the valve element into the seat until a selected value of torque in the valve actuator is reached.

13. A valve system comprising:

a valve actuator for controlling fluid flow through at least a portion of a valve with a valve element; and

a control system for controlling the valve actuator, the control system configured to:

instruct the valve actuator to move the valve element to a target position from an initial position in the valve to reduce or increase fluid flow through the at least a portion of the valve, the initial position being an unobstructed position;

monitor at least one characteristic of the valve system during movement of the valve element to the target position;

detect a location of the target position based on the monitored at least one characteristic of the valve system; and

during each movement of the valve element, the control system being further configured to at least one of:

move the valve element into contact with a seat of the valve system in the target position and then to force the valve element into the seat until a selected value of torque in the valve actuator is reached; or

maintain a predetermined location of the initial position while actively adjusting the location of the target position based on the monitored at least one characteristic of the valve system each time the valve element is moved to the target position.

14. The valve system of claim 13 , wherein the control system is configured to monitor a torque of the valve actuator as the valve element is positioned at the target position.

15. A method of operating a control system of a valve actuator, the method comprising:

moving a valve element with the valve actuator to a closed position to substantially inhibit fluid flow through at least a portion of a valve;

determining a drift of the closed position based on the monitored at least one characteristic of the valve system; and

at least one of:

moving the valve element into contact with a seat of the valve system in the closed position and then forcing the valve element into the seat until a selected value of torque in the valve actuator is reached; or

maintaining a predetermined location of the open position lacking a hard stop in the valve to enable fluid flow through the at least a portion of the valve while actively adjusting the location of the closed position based on a monitored at least one characteristic of the valve system each time the valve element is moved between the open position and the closed position.

16. The method of claim 15 , further comprising monitoring at least another characteristic of the valve system during movement of the valve element to the open position.

17. The method of claim 15 , further comprising:

monitoring position of the valve element as the valve element is moving along a path toward the closed position; and

at a location along the path, switching to monitoring at least one of a torque or a current of the valve actuator as the valve element approaches and reaches the closed position along the path.

18. The method of claim 15 , further comprising:

reducing a rate of speed of the valve element as the valve element travels to the closed position at a selected point; and

update the selected point for the reducing of the speed of the valve element based on the determined drift of the closed position.

19. The method of claim 15 , further comprising locating the control system at a location remote from the valve.