Research Of Large Delay Control Process Based On The Self-tuning Control

The time delay is widely existed in modern industrial process. It has negative effects on the control performance of the system, especially when delay time is large, inertia time is long and dynamic characteristics of the process object is influenced by the various factors. The conventional control method such as PID control can not meet requirements and even cause the stability of the system worse. Therefore, it is an important research with actual meaning to improve the control quality of the system with delay time.In this paper, the theory of the self-tuning control is presented firstly. Then many control algorithms of current large time delay system are studied, for example PID regulator, Smith predictor controller and self-tuning controller. Through simulation, comparing their advantages and disadvantages in the large time delay control system, the result shows that self-tuning control is comparatively the best method.The problem of how to set up the parameter is studied through simulation. In this paper, a lot of simulations show that the order of the model in the algorithm can be set a little larger than the actual object, after setting it like that, the controller do not affect the stability of the system, but also can adapt the time-varying character of the system; loss function is used to determine the time delay constant; and the recursive parameter and covariance matrix has been identified at the beginning of the simulation, the controller do not calculate the output, just identify the recursive parameter and covariance matrix, so when the self-tuning is used, these two parameters has been identified and very fit for the system. With these operations, the controller can not only guarantee stability of the control system, but also adapt the time-varying dynamic characteristics. Aiming at the problem of self-tuning regulator, that is oscillation of the controller output and breakdown of the system. Forgetting factor is determined to 0.9999, and the weighted filtering control thought is introduced into output of the controller, recursive parameter, gain vector, and covariance matrix. These two algorithms are combined together, and a kind of the modified self-tuning control is proposed.At last, the modified self-tuning control arithmetic is applied to the temperature control system of the heater in hot-exchange integrated lab. The system typically possesses heating single direction, large time delay, big inertia and slow time varying characters. The result of the simulation reveals that its performance is much better than PID control.