Study on low-sensitivity control system with robust stability for time-delay plants using double feedback control system

Abstract

In this paper, we consider a robust stability condition of the double feedback control system with low-sensitivity for single-input/single-output time-delay system having an uncertainty in which has a varying number of the closed right half plane. The robust stability problem is to stabilize the control system for the uncertainty. The control system is made robust stability if the complementary sensitivity function of the control system is made small value. On other hands, the control system has the low-sensitivity characteritics such as reducing the influence of uncertaity, the disturbance and etc. if the sensitivity function of the control system is made small value. However, it is difficult that the control system with robust stability has the low-sensitivity characteristics because the sum of the sensitivity function and the complementary sensitivity function is equal to 1. According to Yamada and Yu et al., we can construct the high-performance control system such as having the robust stability and low-sensitivity. The aim of this paper is to expand the result of Yamada and Yu et al. and propose the design method of the control system with robust stablity and low-sensitivity by reducing the influence of uncertainty.