Integral Sliding Mode Fault-Tolerant Control and Active Vibration Suppression of a Flexible Spacecraft in the Presence of External Disturbances

An active vibration control algorithm and robust integral sliding mode control (SMC) are discussed to stabilize the attitude of the flexible spacecraft under external disturbances and actuator faults. As a coupled rigid-flexible dynamical system, the flexible spacecraft is modeled as a rigid hub with two solar panels equipped with piezoelectric (PZT) sensors and actuators. A passive fault-tolerant integral sliding mode control algorithm using a nominal proportional-derivative control algorithm and an improved fault-tolerant algorithm with time-varying additive fault is developed to increase system’s performance, prevent the system's flexible modes excitations in the phase of reaching the sliding surface. Therefore, when the system enters the sliding mode, the closed-loop dynamic behavior, including actuator faults, will be identical to that of the system without faults. It is possible to reduce the residual vibrations caused by the attitude dynamics and actuator faults by simultaneously activating the strain rate feedback (SRF) vibration control algorithm during the maneuver. The performance of the proposed integral fault-tolerant control in terms of the flexible modes excitation, the control effort, and achieving the desired attitude parameters in a comparative study demonstrated its advantage and superiority over the conventional integral sliding mode algorithms.