Self-balanced modal control for spacecraft using thrusters and adaptive bandpass filters

A self-balanced active modal damping scheme is developed for elastic modes of free space structures using thrusters, gyros, and adaptive bandpass filters—self-balanced because it results in no net change in the spacecraft's attitude or angular momentum. The pulsewidth of the thrusters is optimized for fast active damping without destabilizing high-frequency modes and obeying the self-balancing requirement. The thrusters are fired around peak modal rates for maximum efficiency. Minimum rise time bandpass filters are used to extricate the mode from attitude signals issued by gyros. These filters are adaptive in that they can accurately measure the frequency of the mode, known imprecisely before, and adjust their outputs accordingly to yield correct amplitudes and phases of the modes to be damped. The modal amplitudes are then propagated as in Kalman filter. The scheme is successfully illustrated on a generic flexible spacecraft in the presence of modeling errors in structural damping.