Design of robust pid controllers for first-order plus time delay systems based on frequency domain specifications

Abstract EN

This paper considers a design method for PID controllers to achieve the robustness to the uncertainty of the time delay for the first-order plus time delay system (FOPTD).

Initially, the stabilizing regions of the PID controller gains are determined by a graphical stability method.

Then, we specify two simultaneous design specifications: gain margin and phase crossover frequency.

These specifications give a set of stabilizing PID controllers.

To get a unique PID controller, we introduce an additional constraint which is finding the smallest absolute value of the slope of the open-loop system magnitude at the specified phase crossover frequency.

The obtained PID controller is located in the stability region, and also robust to system time delay variation due to the proposed constraint.