Maneuvering and vibration damping of flexible spacecraft using adaptive variable structure control and suboptimal positive position feedback

This paper presents a dual-stage control system design method for the rotational maneuver and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as sensors and actuators. In this design approach, attitude control and vibration suppression were designed separately using lower order model. The design of attitude controller was based on adaptive variable structure control (AVSC) theory leading to a discontinuous control law. This controller ac complishes asymptotic attitude maneuvering in the closed-loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. To actively suppress certain flexible modes, a modified positive position feedback compensator which adds damping to the flexible structures in certain critical modes was designed in the inner loop. The problem of deter mining the modified PPF gain is formulated as static output feedback problem. Numerical simulations are performed to show that rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance torque and parameter uncertainty.