Synthesis of fractional order robust controller based on Bode's ideas

The basic Bode's ideal transfer function (BITF) based controller may not guarantee sufficient disturbance rejection for a class of plants with a cascaded integrator. In this paper, an improved BITF based control method is proposed to enhance the disturbance rejection performance for this class of control systems. A fractional order proportional-integral controller and a Bode's ideal cut-off filter are introduced into the BITF based control strategy, improving the open-loop magnitude characteristics of the control system in the low and high frequency ranges. Therefore, the disturbance rejection performance of the control system can be improved, with small impact on the system's stability. The improved BITF based control method is applied to the speed control problem of a class of permanent magnet synchronous motor servo systems. The robustness and dynamic response performances of the improved BITF based control system are verified by simulation and experiments. Performance comparisons are performed between the system using the improved BITF based control method and those using some existing control methods. Simulation and experimental results both show that the improved BITF based controller can enhance the step response performance and robustness of the PMSM servo system simultaneously and make the system achieve better disturbance rejection performance than the systems using some existing methods.