Attitude Controller Design of Underactuated Spacecraft with Two Control Moment Gyroscopes

The problem of stabilization was studied for an underactuated spacecraft with two single gimbal control moment gyroscopes (SGCMGs). The equations of dynamics and kinematics were derived under the assumption of zero momentum of the spacecraft. By using backstepping design method, a discontinuous state feedback controller is obtained. It can stabilize the attitude of the spacecraft in globally asymptotic way. All kinds of singularities of the SGCMG system were discussed. And the steering law of the SGCMG system is obtained under the premises of avoiding singularities. Simulation results of a certain underactuated spacecraft indicate that the controller presented above is feasible