摘要: The variation of plant dead-time deeply affects the stability of the predictive PI control system. It is important for designing and applying the PPI controller to calculate the delay margin. A criterion of stability for the PPI system and the quantitive relationship among the delay margin, the time constant of the closed-loop system, and the dead-time of the model are given. A graphic algorithm to compute the delay margin is also developed. The phenomenon that there exist more than one stability delay zones is discussed. The algorithm is shown to be precise by some simulations.