A Study Of The Smith Predictor To Time Delay Systems

Delays are very common in the industry control process. The large delays dramatically weaken the stability and performance of systems. So it is meaning for putting forward simple and useful methods to control delay systems.Smith predictor is an effective method to compensate for time delays, but it is sensitive to the change of the parameters, which often causes systems unstable. This paper analyzes the stability of the quasi-polynomials, which is derived from the characteristic equations of Smith predictor control systems, based on two differential-equation theorems.After analyzing stability of the traditional Smith-Predictor, this paper furthermore analyzes the stability of a modified Smith predictor. The simulation shows that a large stability field is obtained. When parameters of the plant are time-varying, the modified Smith predictor with adaptive control scheme can eliminate the difference between the plant and the model.