Something that all manufactures of wireless throttling valves must be concerned with in their design is battery power consumption. In a control application using a wireless throttling valve much of the power available to the actuator is used to track changes in target valve position. To minimize battery power consumption, the number of changes made in target valve position may be reduced by structuring the control as illustrated below.
If an acknowledgement to the last change in target position has been received, then a new target position will be transmitted to the valve when either of the following conditions are met:
- The absolute value of the difference between the calculated PID output and the last target value communicated to the valve exceeds a configured DEADBAND value.
- The time since the last communication to the valve exceeds the configured DEFAULT reporting time.
The resulting slower, non-periodic changes in stem valve position can be accommodated by the PIDPlus through the use of stem position feedback. As is illustrated in the example below, stable control comparable to that provided by using a wired valve with PID was observed for changes in setpoint and load disturbances.
However, the number of changes in valve target is significantly reduced. In this example, the number of changes in target valve position vs PID with a wired valve was reduced by a factor of 23X. Such a reduction can significantly reduce battery power consumption.