Nonlinear Stability Analysis of Control System with Program Floatation of Interceptor

According to naturally nonlinear characteristics of attitude and divert engines,the describing function method based on harmonic linearization is used to analyze the system stability.The Nyquist magnitude and phase criteria of nonlinear system is derived.Furthermore,in the appilication of project,the Nyquist magnitude and phase criteria is exchanged with Bode logarithm criteria.The two criteria are used to analyze the stability of pitch loop control,roll loop control and position control.The force bias of attitude and divert engines is also considered.The result shows the attitude control system and position control system of program floatation are stable.