Amplitude dependent analysis and design of nonlinear control systems in a frequency domain

Examines the amplitude dependent behavior of nonlinear feedback systems in a frequency domain. We apply a robust stability condition to a feedback control system containing a nonlinear element in the forward path. In addition, we derive an instability condition for that type of nonlinear feedback system. By using these concepts, we can accurately predict and estimate the existence of a periodic oscillation, that is, a limit cycle in a phase space of the nonlinear dynamical system. Two numerical examples for that type of control system are presented to verify the method.