PID Control System Design and Automatic Tuning using MATLAB/Simulink

4Implementation of PID Controllers

4.1 Introduction

The key reason for the wide application of PID control systems is their simplicity of structure, design, and implementation. This chapter shows how to implement a PID controller with operational constraints. Operational constraints are used to ensure plant safe operation and protect the electronics from damage when the control signals exceed limits. Without exception, all control systems implemented in practical applications must contain the operational constraints.

4.2 Scenario of a PID Controller at work

To understand how the implementation of a PID controller is performed, we will first describe the general scenario of a digital control system at work.

A computer controlled system generally consists of a plant to be controlled (including sensors and actuators), and a computer that stores control algorithms and computes the input to the plant. In many applications, the computer is replaced by a micro-controller or a digital signal processor.

The majority of the physical systems are continuous time systems. The variables within the systems are inherently analog continuous signals. For instance, the pressure signals, temperature signals, voltage signals and current signals are the commonly encountered analog signals in physical systems. These analog signals are continuous in nature. Since the computers, micro-controllers and digital signal processors only take the digital signals for processing, there must be key devices ...