Anti-unwinding constrained attitude control for flexible spacecraft with actuator saturation

In this paper, two novel anti-unwinding constrained attitude controllers for flexible spacecraft are designed based on inverse optimal approach and unit quaternion representation of attitude subjected to inertia matrix uncertainty and external disturbance. One accounts for actuator amplitude constraint and the other considers actuator amplitude and rate constraints at length. A new saturation compensator is designed and embedded into the controllers to eliminate the effect of actuator saturation. The proposed controllers can avoid the issue of attitude slewing unwinding due to the double values of unit quaternions. The stability of the resulting closed-loop systems by the proposed controllers is guaranteed by Lyapunov-based approach. Simulation results are presented to assess the performance of the proposed methods.