Simple analytical rules for PI-PD controllers to tune integrating and unstable plants

Proportional-Integral-Derivative (PID) controllers are still extensively used in industrial systems. In the literature, many publications can be found considering PID controller design for processes with integrators and unstable transfer functions. However, due to structural limitations of PID controllers, generally, good closed loop performance cannot be achieved with a PID for controlling aforementioned processes and usually a step response with a high overshoot and oscillation is obtained. On the other hand, PI-PD controllers are proved to give very satisfactory closed loop performances for these processes. Hence, the paper introduces a simple approach to obtain parameters of a PI-PD controller for the control of integrating and unstable processes. Simulation examples are given to illustrate the value of the approach proposed