Amplitude dependent analysis and stabilization for nonlinear sampled-data control systems

This paper analyzes the amplitude dependent behavior of nonlinear sampled-data control systems in a frequency domain. We apply the robust stability condition for discrete-time nonlinear systems to a sampled-data control system containing a single nonlinear element in the forward path. By considering a restricted area (a sector) in the nonlinear characteristic, we can accurately predict and estimate the existence of a sustained oscillation whether it is periodic or not. In this paper, first, we summarize the robust stability condition and discuss the possibility of the amplitude dependent analysis for these types of nonlinear control systems. Then, we present a method of improvement in the stability for nonlinear sampled-data control systems.