Fault-tolerant attitude control for flexible spacecraft without angular velocity magnitude measurement

The fault-tolerant control (FTC) scheme for flexible spacecraft attitude stabilization in the presence of external disturbances, uncertain inertia matrix, and even two types of actuator faults was investigated. The control law was derived with quaternion feedback and the knowledge on direction of the body angular velocity only by using a first-order differentiation filter to account for the unmeasured magnitude of the angular velocity. The control law equation managed to compensate for the additive fault and partial loss of effectiveness, so that the closed-loop system was stabilized within 150 s, and acceptable performance was also met despite of severe external disturbances. The developed control scheme did not involve any adaptive learning on system uncertainties or unknown bound, so the controller was more computationally favorable and practical for applications. Numerical simulations were carried out to demonstrate the effectiveness of the proposed control structure.