Design for the six-DOF air bearing table and automatic mass balancing system of attitude platform

For the problem of relative attitude and position control involved in satellite rendezvous and docking, a 6 degree-of-freedom (DOF) air bearing table is designed, and a coupled 6-DOF dynamics model is developed to describe that two air bearing tables simulate the motion of rendezvous and docking. To reduce the gravitational torque involved in creating a space-like environment with the air bearing table, an automatic mass balancing system based on an adaptive finite-time control scheme which uses a novel fast nonsingular terminal sliding mode surface is designed, then the center of mass is estimated out, and based on this, three proof masses are actuated to compensate for the center of mass offset from the center of rotation. The Lyapunov theory and the simulation results show that the method proposed can accurately estimate the center of mass of the attitude platform rapidly, and realize the center of mass being exactly aligned with the center of rotation.