Abstract: For a spacecraft with three orthogonally placed reaction wheels and the fourth skewed one, the attitude control problem is considered in this paper when two of three orthogonally placed wheels failed. Under the assumption of zero system angular momentum, a piecewise decoupling control law is designed to stabilize the attitude of the spacecraft by using two residual wheels. By using the Euler angle parameterization method, spacecraft dynamics and kinematics are given and a piecewise control law is proposed based on the decoupling property of the model. After six maneuvers, the proposed scheme ultimately guarantees the attitude stability. Simulation results demonstrate the proposed control approach.

Key words: underactuated, spacecraft, attitude stabilization, decoupling control, reaction wheel