PID Control System Design and Automatic Tuning using MATLAB/Simulink

8PID Controller Design for Complex Systems

8.1 Introduction

The PID controller design methods discussed in the previous chapters are either model based approaches or rule based approaches. It is clear that when using a model based approach, a first order model yields a PI controller and a second order model yields a PID controller. In some applications, the first order and second order models are basically an approximation to the actual physical systems. In other applications, the underlying physical systems are complex and are of higher order. This chapter studies how to design PID controllers for higher order systems directly using frequency response data.

8.2 PI Controller Design via Gain and Phase Margins

This section presents PID controller design via specification of gain margin and phase margin.

8.2.1 PI Controller Design Using Gain Margin and Phase Margin Specifications

The starting point is to assume that the frequency response of a desired open-loop transfer function at a specific frequency point is available. It is also assumed that the frequency response of the system is available at .

At the frequency , the actual open-loop frequency response with a PI controller ...