Stability regions of PID parameters for model-free SISO systems with time delay
无模型SISO时滞系统的PID参数稳定域研究

For the single-input and single-output (SISO) time-delay system with no accurate model, we propose an analytical method for determining the stability regions of PID parameters by using the frequency response data. The frequency response data are obtained by using the method of frequency response identification from relay feedback. Then, the singular and nonsingular boundaries of the PID parameters are determined from the frequency response data. By comparing the number of unstable poles on both sides of a boundary, we select the side with less unstable poles for determining the regions of PID parameters which make the closed-loop system stable. For the model-free SISO system with time delay, the proposed method avoids the complexity of the model identification, and thus provides a convenient approach for the design and tuning of the PID controller. The simulation results demonstrate the validity of this method.