Sliding mode control of flexible spacecraft under disturbance torque

The authors present a control system design for large-angle rotational maneuvers of a spacecraft-beam-tip body (an antenna or a reflector) configuration. It is assumed that an unknown but bounded disturbance torque is acting on the spacecraft. A sliding mode attitude control law is derived for the slewing of the space vehicle. This slewing control law requires only attitude error and its derivative for feedback and does not need any information on the elastic motion of the system. For the damping of the elastic motion, a stabilizer is designed separately based on the asymptotically decoupled system describing the elastic deflections in two orthogonal planes. Simulation results are presented to show that precise large rotational maneuvers can be performed using the attitude controller and the elastic mode stabilizer in spite of the uncertainty in the system