Genetic algorithm tuned PID controller for process control

The main aim of this paper is to develop a PID tuning methodology for a processing plant using Genetic Algorithm. Genetic Algorithm or in short GA is a stochastic algorithm based on principles of natural selection and genetics. Genetic Algorithms (GAs) are a stochastic global search method that mimics the process of natural evolution. Genetic Algorithms have been shown to be capable of locating high performance areas in complex domains without experiencing the difficulties associated with high dimensionality or false optima as may occur with gradient decent techniques. Using genetic algorithms for the tuning of controller will result in the optimum controller being evaluated for the system every time. In this proposed work, it has been demonstrated that by employing the GA method of tuning a plant, an optimization can be achieved. The performance of proposed GA tuned plant has been compared with classically tuned plant, where the GA tuned (proportional, integral and differential) PID controller outperforms the conventionally developed PID controller.

I. Introduction

It is a known fact that the PID controller is employed in every facet of industrial automation and process control. The application of PID controller ranges from small industry to high technology industry. For those who are in heavy industries such as refineries and ship buildings, working with PID controller is like a routine work. PID controller consists of Proportional Action, Integral Action and Derivative Action. It is commonly refer to Ziegler-Nichols PID tuning parameters. It is by far the most common control algorithm [1], [9]. In this portion, the basic concept of the PID control has been explained. PID control algorithms are mostly used in feedback loops. PID controllers can be implemented in many forms. It can be implemented as a stand-alone controller or as part of Direct Digital Control (DDC) package or even Distributed Control System (DCS). The latter is a hierarchical distributed process control system which is widely used in process plants such as pharmaceutical or oil refining industries. It is interesting to note that more than half of the industrial controllers in use today utilize PID or modified PID control schemes. In Fig. 1 a simple diagram illustrating the schematic of the PID controller in non-interacting form or parallel form is shown.