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Automatic mass balancing and design of a six degrees-of-freedom air bearing spacecraft simulator

Six degrees of freedom(DOF) air bearing spacecraft simulators are the major component of the all physical simulation test system engaged in rendezvous and docking in the third stage of lunar exploration project. Ground simulation of spacecraft motion simulating all six degrees of freedom(DOF) is a challenging problem mainly due to that weightlessness in space is difficult to reproduce on ground, to simulate the space environment with the air bearing spacecraft simulator, the effects of gravity should be minimized. This paper designs a 6 DOF air bearing spacecraft simulator, and an automatic mass balancing system by actuating three proof masses on linear motion stages to compensate the offset between the center of mass(CM) and the center of rotation(CR) for the spherical air bearing system with 3 rotational degrees of freedom on the simulator. This paper propose using nonlinear adaptive control and unscented Kalman filter(UKF) for mass balancing. The stability of the feedback system and the convergence of the estimated unknown parameter are analyzed through Lyapunov stability theory. The proposed methods are simulated based on the data of a 3 DOF air bearing simulator that our team developed, the results show that the performance of the method proposed is better than that of the method has been used.