Genetic optimization of variable structure PID control systems

This paper describes the design of a variable structure PID control system (VSPID) using genetic algorithms. This VSPID has a structure similar to that of the simple PID controller where the PD mode is used to speed up response, whereas the PI mode is applied to eliminate the steady state offset. Flexible changes of controller modes and parameter values of the VSPID could therefore solve the conflict between steady state error and dynamic responsiveness. Due to the difficulties encountered in the application of traditional analytical and numerical methods for the design of variable structure controllers, a microgenetic algorithm is used for the determination of the controller parameters. uGA is known to converge rapidly with optimal or near optimal results. In order to demonstrate the design procedure the temperature control of an oven is used. Taking the integral of the absolute of the error as the performance measure reveals that the proposed VSPID is better than the simple PID controller