Abstract:Attitude control for a flexible spacecraft with inertia uncertainty and external disturbance is considered. First, a flexible modal observer is constructed to estimate the flexible modal variables. Then, an adaptive law is constructed to estimate the upper bound of a certain function of the inertia uncertainty and external disturbance. Then, based on the constructed flexible modal observer and proposed adaptive law, an adaptive sliding mode control law based on observer is established for the flexible spacecraft with inertia uncertainty. To verify the effectiveness of the presented control law, simulations are performed in the presence of inertia uncertainty. Simulation results show that the proposed control law can attenuate the effect of inertia uncertainty successfully and the attitude states can be stabilized by the proposed sliding mode control laws.