A Construction of Self-Tuning PID Control System and Its Application to Temperature Control of a Polystyrene Reactor

Abstract

Self-tuning control strategies have been considered for systems with unknown parameters. The rapid progress of digital computer enables us to simulate complex and large-scale systems. Many control techniques have been proposed in order to improve the control performance for discrete-time control systems. However, since these control techniques are too complex, it is usually difficult to apply them to real plants and also difficult to understand a physical meaning of control parameters included in these control systems. On the other hand, PID control methods based on the classical control theory have been used widely for real control systems since they have simple control schemes. Therefore, it is necessary to consider control methods with PID control structure in the discrete-time systems. Many literatures with regard to auto-tuning and self-tuning PID control strategies have been reported up to now. But none of them gives us any results for discrete-time systems with time-delay which takes important roles for the stability of the control system and the good control performance.In this paper, we consider a self-tuning PID control algorithm for a system with a time delay element. This control method has four gains, which are proportional, integral, differential gains and a gain for modifying the reference signal. This method enables us to improve a tracking property for a reference signal in the transient state, and also to guarantee the global stability of the control system. Finally, the effectiveness of this control method is shown by applying the method to a temperature control system of a polystrene reactor. In order to show the effectiveness of this method.