The Research On Robust PID Controllers

PID controller is the most widely used controller in process industry. However, there are many kinds of uncertainties in complex process. For this kind of process, the regular PID controllers can hardly achieve satisfactory control effects. In order to strengthen the tolerance of PID controller to process' uncertainties, three tuning methods for robust PID controller is studied in this paper. And through simulation researches, the performance and robustness of the robust PID controllers are proved.In chapter two, the robust PID controller based on internal model control (IMC-PID) is presented. For model sets whose uncertainty boundary is known and models with bounded uncertainty, two robust PID tuning methods are given respectively. Because the robustness of the systems is taken into account in the designing process, the IMC-PIDcontroller has good robustness. Simulation experiments on first order plus dead time (FOPDT) models using Matlab and physical simulator are done in this paper. The simulation results show that IMC-PID controller has good performance and robustness.In chapter three, the robust PID controller based on H_∞ control theory is investigated. Based on Youla parameterization principle, and through optimizing the sensitivity function of the system, theparameters-tuning method of robust PID controller is accomplished. Will) regard to dead time of process, usually the first order Pade approximation method is adopted. While this paper uses the second order unsymmetrical Pade approximation, which can decrease the approximation error and improve the robustness and performance of the system. Simulation researches on FOPDT plants and plants with large dead time proved the validity of this method.In chapter four, the robust PID controller based on Hm loop-shaping principle is studied. The designing procedure of the robust PID controller is given and the selection of weighting functions is discussed in detail in this paper. Simulation researches on FOPDT plants, plants with large dead time, and plants with integrating process are done to verify the performance and robustness of the system.In all of the three methodes stated above, the PID controllers are functions of parameter A, whose value will affect the performance and robustness of the system. The range of X and its effects to the control performance of the systems are analyzed, and relevant simulation researches are accomplished in this paper.Liu Guohua (Control theory & control engineering)Supervised by: Shihongrui...