Active vibration suppression in flexible spacecraft with mismatched uncertainty via variable structure control

This investigation is to apply the variable structure output feedback control (VSOFC) and distributed piezoelectric sensor/actuator technology to a large-angle rotational maneuver and vibration control of a flexible spacecraft. Two separate control loops are adopted to satisfy the pointing requirements and simultaneously suppress vibrations. We use the piezoceramics as sensors and actuators to actively suppress certain flexible modes in designing a positive position feedback (PPF) compensator that adds damping to the flexible structures in certain critical modes of the inner feedback loop. Then, a second feedback loop is designed using the variable structure techniques, using only output information, to slew the spacecraft. Compared with conventional methods, the proposed scheme guarantees closed-loop system stability, and yields good performance and robustness in the presence of parametric uncertainties and external disturbance. Simulation results for the spacecraft model show precise trajectory control and vibration suppression.