Study On Tuning Of Fractional-order PID Controller

At present, the research of fractional-order PID controller tuning method is a hot topic in the control field. Many scholars had begun the research and many achievements had been got. Compared with the ordinary PID controller, the difficulty in tuning the fractional-order PID increased because of the addition of anther two parameters λ and μ, although the fractional order one could lead to a better control effect and more flexible tuning method. In the thesis, the study was on the basis of the existing achievements and had been preceded in the following aspects.Firstly, the Quantum Evolutionary Algorithm (QEA) has been studied, and the method of tuning fraction-order PID using revised QEA based on Bloch sphere was proposed. The comparison of the control effects among another two schemes including revised PSO and Generic Algorithm (GA) presented in the references had been made. And the simulation results proved the validation of the approach.Secondly, on the basis of the existing achievements about the parameter stability region of fractional-order PID controller, a new method of determining the optimal controller parameters was proposed. For the integral-order or fractional-order controlled system, the boundaries of the parameter stability region including Real Root Boundary (RRB), Complex Root Boundary (CRB) and Infinite Root Boundary (IRB) could be attained, and the controller parameter together with frequency range could be determined. Then, the Integral Time Absolute Error (ITAE) could be chosen as the performance index, and the optimal parameters could be got using the GA optimization with the preset phrase and amplitude margin as the constraints. The simulation results illustrated that good dynamic response could be got when tuning the fractional-order PID controller with the proposed method.At last, the problem of tuning the fractional-order PID satisfying the sensitivity constraints was discussed. In the paper, the expression of Kp,Ki was derived when the controller meeting the sensitivity constraint, and the cases were studied when integral time delay fractional-order system or the quasi-first order time delay system was taken as the controlled system. The method of the stable solution judgment presented in the paper could avoid the complicated procedure when adopting the other method in the reference. The validation was proved by the simulation examples.