by Jan Schuurmans, written at 16-1-2020
Estimated reading time: 1 minutes
Offset in PID control
In this post I am writing about PID control that suffers from offset. Offset means that the controlled Process Variable (PV) deviates from Set-Point (SP). If you are using P-control or PD control, without integral action, this problem should not surprise you. However, if you use PI or PID with Integral action, you would not expect this issue. Right? Wrong: we had this issue in several cases, among others in a laminator (see our post Temperature Control of a Laminator
As an example, have a look at Figure 1, showing the measured(!) temperature and setpoint of a process that was regularly perturbed. The PID controller, containing integral action, was tuned well and did not show an offset after a single perturbation. However, in this case it was perturbed regularly again and again.