Automatic Mass Balancing of a Spacecraft Three-Axis Simulator: Analysis and Experimentation

Spacecraft three-axis simulators provide frictionless and, ideally, torque-free hardware simulation platforms that are crucial for validating spacecraft attitude determination and control strategies. To reduce the gravitational torque, the distance between the simulator center of mass and the center of rotation needs to be minimized. This work proposes an automatic mass balancing system for spacecraft simulators, which uses only the three sliding masses during the balancing process, without need of further actuators. The proposed method is based on an adaptive nonlinear feedback control that aims to move, in real time, the center of mass toward the spacecraft simulator's center of rotation. The stability of the feedback system and the convergence of the estimated unknown parameter (the distance between the center of mass and the center of rotation) are analyzed through Lyapunov stability theory. The proposed method is experimentally validated using the CubeSat Three-Axis Simulator at the Spacecraft Robotics Laboratory of the Naval Postgraduate School.