Asymptotic Characteristics of Optimal Preview Control System

One of the useful method to improve a designed control system performance is utilization of the future desired signal and/or disturbance signal, if possible. Until now, optimal preview control system and preview pre-compensator are considered on the basis of optimal regulator theory and model matching approach. Effectiveness of the preview control system is shown in the application to servo system and robot manipulator control etc. Usually, preview control system has excellent phase characteristics compared with the usual control system which does not utilize future desired signal. In order to make clear the characteristics of the optimal preview control system, asymptotic characteristics of the preview control system with respect to near-zero weighting factor for input variable term in the quadratic performance index. In this paper, the asymptotic characteristics for the following three points are shown (1) closed loop poles (2) pulse transfer function (3) performance index value. Pulse transfer function from desired signal to controlled variabvle approaches to unity and that from disturbance signal to controlled variable approaches to zero by utilizing future desired signals. Performance index value approaches to zero on approaching zero weighting factor for input variable in the quadratic performance index. Above considerations are carried out for two cases control system with and without input delay time due to processing time for control algorithm.