PID Control System Design and Automatic Tuning using MATLAB/Simulink

5Disturbance Observer- Based PID and Resonant Controller

5.1 Introduction

In Chapter 1 to Chapter 4, we discussed PID control systems with explicit functions of proportional control, integral control, and derivative control. Because integral control embeds a marginally stable mode in the controller structure, which could cause the problem of integrator windup when the control signal reaches its saturation limits, the PID control system implementation requires modification to overcome this problem. Similar implementation problems to a worse degree are faced by the resonant controllers.

This chapter examines the PID controller design and resonant controller design from a different angle to the previous chapters. It introduces the integral mode and resonant modes through disturbance estimation. By doing so, the design becomes simpler, and more importantly, the implementations of the PID and resonant controllers flow naturally from the designs with anti-windup mechanisms. This development is particularly significant for resonant controllers because simplicity in the implementation with anti-windup mechanisms is paramount for practical applications.

5.2 Disturbance observer-Based PI Controller

This section introduces the idea of disturbance estimation that leads to an equivalent PI control system. The mathematical model used in this section is a first order model. For systems with higher order transfer functions, approximation is required.

5.2.1 Estimation of Disturbance with ...