Robust controller design for First order Plus Time Delay systems using Kharitonov Theorem

In this paper, a new method using Kharitonov theorem and an algorithm in MATLAB for stability boundary locus is applied to compute all the stabilizing PI controller gains for a stable first order plus time delay system which satisfies both robust stability and robust performance criteria. The PI settings designed using SIMC rule is also shown in the common stability region. Similarly for an unstable FOPTD system all stabilizing PID controller is identified which satisfies both robust stability and P.M specification. The PI settings designed for unstable FOPTD system using Dominant Pole Placement and Equating Coefficient method is shown on kp – ki plane to compare robustness. It is also shown that to design robust controller for Unstable FOPTD, PID controller should be preferred to PI controller.