A Design Method for Stabilizing Smith Predictor for a Class of Non-minimum-phase Time-delay Systems

Abstract

In this paper, we examine a design method for a modified Smith predictor for a class of non-minimum-phase time-delay plants. The modified Smith predictor is well known as an effective time-delay compensator for a plant with large time delays. Several papers on the modified Smith predictor have been published. However, the parametrization of all stabilizing modified Smith predictors has not been obtained. The purpose of this paper is to propose the parametrization of all stabilizing modified Smith predictors for a class of non-minimum-phase time-delay plants and present a design method of modified Smith predictors. At first, the definition of modified Smith predictor is given. Next, we propose the parametrization of all stabilizing modified Smith predictors for a class of non-minimum-phase system which is not necessarily stable. The control characteristics of the control system using the parametrization of all stabilizing modified Smith predictors are also given. The obtained parametrization of all stabilizing modified Smith predictor has a free-parameter which is used to specify control specification. Next, in order to specify input-output characteristics, we present a design method of modified Smith predictor using the fusion of obtained parametrization of all stabilizing modified Smith predictors and the model matching methods. Finally, a numerical example for unstable plant is illustrated to show the effectiveness of the proposed method.