DEVELOPMENT OF A PSEUDO-NYQUIST ANALYSIS TECHNIQUE FOR HYBRID SAMPLED-DATA CONTROL SYSTEMS.

The stability characteristics of a launch vehicle, as a function of gain and phase variations at the thrust vector controller (TVC), cannot be obtained using classical sampled-data control theory if the launch vehicle attitude control system contains both sampled-data and continuous feedback control loops. A method has been developed which can be used to generate a sampled-data pseudo-Nyquist plot for gain and phase variations at the controller. This method was developed and used to determine the stability characteristics of the Saturn IB launch vehicle in the backup guidance mode.