Positioning Actuator Control Loops - FACTS Engineering Direct Logic 405 Manual

POSITIONING ACTUATOR CONTROL LOOPS

A reversible electric motor used to operate a valve is an example of a positioning actuator. This
example will use the controller output in V5003 to position an actuator controlled by forward and reverse
contacts. Y11 will run the motor in reverse and Y10 will turn the motor in the forward direction.
Feedback is required to correctly position the actuator. The actuator position could be input via a 4-20
mA signal derived from a slidewire connected to the actuator mechanism. A scaled BCD output of an
absolute encoder connected to the motor might also be used to determine the actuator position. In this
example, the actuator position is assumed to be in V1400. A value of 4095 (20 mA) in V1400 indicates
that the actuator is 100% forward. A value of 0 (4 mA) in V1400 indicates that the actuator is at the
reverse limit.
A deadband (tolerance) is applied to the actuator position to prevent chattering of the outputs when the
actuator is near the desired position. In this example, the deadband of the actuator positioning is
specified in V1401.
SUPPORTING LADDER LOGIC 3.5