Combined Dual Plant Modeling and Controller Design with Verification for the Nutator System

Abstract

A nutating sub-reflector is a convenient method for switching an antenna's beam between its target and background. Technically, the nutating mechanism introduces potential dynamical instability to an antenna structure. A typical nutator system can be roughly separated in two major rotating parts, the rocker and the reflector. Both of them equipped with controller, voice coil motor (VCM) and encoders/sensors. We propose combined dual plant modeling to reduce the couple system and combining the rocker and reflector plant in single transfer function form. Besides, the nutator system's stability, controllability and observability also are analyzed. Laser Doppler Vibrometer (LDV) and Dynamic Signal Analyzer (DSA) were used to experiment the realistic system and build up system dynamic response to verify the mathematical system. PID (Proportional-Integral Derivative) and PDFF (Pseudo-Derivative Feedback with Feed-forward Gain) were individually designed for it. Moreover, adding a white noise block in front of the VCM plant which can simulate the outside disturbance due to wind torque or other environmental impact. Our target was to proposed better effective control loop which inhibited the disturbance effectively. We present a complete analysis of combined dual plant modeling as well as control loop about the nutator system, and verifying the mathematical plant by LDV and DSA.