The low-sensitivity control with robust stability using Multiplex-feedback control system for a time-delay plant having a varying number of unstable poles

In this paper, we propose a design method of the multiplex-feedback control system having low-sensitivity and robust stability for a single-input/single-output time-delay system with a varying number of poles in the closed right half plane. The low sensitivity control has high-performance of input-output property. However, it is well-known that the low-sensitivity control often cannot maintain the control system robust stability. According to Yamada, there is a low sensitivity control system design method maintaining robust stability for a single-input/single-output minimum-phase system with a varying number of unstable poles. In addition, Yu et al. expand the result of Yamada and propose a design method of the multiplex-feedback control system that has low-sensitivity characteristics less than a conventional two-degree-of-freedom control system. In this paper, we expand the result of Yamada and Yu et al. and propose a design method of the multiplex-feedback control system with robust stability that has low-sensitivity characteristics less than a conventional feedback control system for a single-input/single-output time-delay plant having a varying number of unstable poles.