Robust tuning of 2DoF PID controllers with filter for unstable first-order plus dead-time processes

The aim of this paper is to present the application of a model reference design procedure to the robust tuning of two-degree-of-freedom proportional integral derivative controllers with filter for control of unstable controlled processes. The design is based on the use of an optimization procedure with servo and regulatory closed-loop transfer functions targets. Due to the constrains imposed by the unstable processes the robust design is based in the maximum obtainable robustness with the selected control system response target. Controller tuning equations are provided for unstable first-order plus dead-time models. The design procedure considers at the same time the five parameters of the controller including the filter time constant. Equivalent parameters and a tuning rule for Standard PID controllers are also presented.