Attitude control of a piezo-strut mounted camera on a spacecraft with deployed solar panels

A nonlinear two loop quaternion based state dependent Ricatti equation (QSDRE) control and an LQR control based on linearized system equations are designed to improve the pointing performance of a large Earth Observation camera carried by a spacecraft with deployed solar panels. The system is modeled as eight bodies, a spacecraft, a high resolution camera, four solar panels, two in each side, and two yokes for connecting solar panels to spacecraft. The spacecraft and camera is connected by piezoelectric actuators to damp out vibrations, and a satellite mounted reaction wheel cluster to realize slew maneuvers. The Newton-Euler method is employed for the derivation of the multi-body equations of motion. Different pointing metrics such as accuracy, jitter and stability are used to evaluate the pointing performance of the camera. The effectiveness of this two loop QSDRE control as well as LQR control for improving the pointing performance of the camera are examined through simulations. The simulation results of both controllers are then compared and discussed from pointing performance point of view.