A new design method of internal model control based on butterworth filter for non-minimum phase high-order systems

The first-order or second-order process model with time delay is often used to approximate the high-order process object. However, it is difficult to accurately describe the dynamic behavior of the system. Therefore, the traditional PID control method is unable to obtain satisfactory control effect. In the meantime, conventional internal model control (IMC) cannot obtain better control performance. In this paper, the filter of conventional IMC is replaced by the optimized and improved Butterworth filter. The main reason for this is that the Butterworth filter has an ideal low-pass filter characteristic, as well as its most stable characteristic of ups and downs of amplitude-frequency features within the whole frequency pass band. The method proposed is compared respectively with traditional PID control and conventional IMC. Simulation studies show that the method proposed can improve dynamic quality and robustness of high-order process. Meanwhile, the method provides good performance even though a mismatch exits between model and actual process.