How the IPIDController function block implements PID control

The IPIDController function block, available in the
FactoryTalk Design Workbench
 instruction set, is based on PID control theory and combines all of the necessary logic to perform analog input channel processing and proportional integral-derivative (PID) control.
In the HMI, the IPID faceplate is available for use with the IPIDController function block.

IPIDController function block description

The IPIDController function block uses the following function block components:
  • A: Acting (+/- 1)
  • PG: Proportional Gain
  • DG: Derivative Filter Gain
  • td: ãD
  • ti: ãI
IPIDController function block description
IPIDController function block description

Preventing integral windup

If the difference between the setpoint value and the process value is great, the output value increases significantly, and during the time it takes to decrease, the process is not in control. The IPIDController function block interactively tracks feedback and prevents integral windup. When the output is saturated, the integral term in the controller is recomputed so that its new value provides an output at the saturation limit.
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