PID Controller And Its Design Methods

Most of real industrial processes are controlled by PID controllers. The performance of these control systems are directly related to the stable operation of processes, the quality of product and the great benefit of the enterprises. It is very significative for optimization design.Many traditional design methods consider only one aspect of the control problem. For example, in the classical design rule of Ziegler-Nichols the objective was to reject load disturbances, no aspect was taken to changes in set point. It is necessary for a new design method to consider all aspects of the control problem.The stability of the closed-loop system is first considered in controller design. If the system is not stable, it is not benefit to improve other performances. When controller implemented, its parameters often have a departure from ideal design value for a variety of reasons. For example, the change of environmental temperature will result in the changes of electronic components parameters. As a result, it is necessary to design a non-fragile PID controller for the stability of the closed-loop system even though there are some disturbances in the parameters of controllers.Based on the above problems, the main research ideas and results obtained in this paper are as following,Firstly, the basic principle of PID controller and its parameters tuning method are briefly reviewed. Secondly, some recent optimization design methods are summarily introduced, mainly including the design method of two degrees of freedom PID controller and the approchs of PID controllers design via Linear matrix inequalityies (LMI). Thirdly, based on a suitable extension of the Hermite-Biehler Theorem, the problem of the region of PID parameters for stabilizing a second-order system with time delay is sloved, and the method of Linear Programming is used to determine the non-fragile PID stabilizingcontroller. Finally, experiment results for a triple-flume control system prove the effectiveness of the non-fragile PID stabilizing controller.