Automatic mass balancing of spacecraft attitude simulators by optimal feedback control

Abstract

There is an increasing interest in development of spacecraft attitude simulators. A necessary and challenging task in preparation for any attitude control experiment is to remove the gravitational disturbances on the simulator by a mass balancing system which relocates the center of mass to coincide with the center of rotation. This research is aimed at filling a substantial gap in the literature by presenting a methodical framework for analysis and design of closed-loop automatic mass balancing systems. In this regard, a state-space representation for imbalanced dynamics of attitude simulators is derived to enable the application of modern control techniques to the problem which will be shown to be very effective in achieving an accurate balancing. The model is further enhanced by state augmentation and incremental control input to address the practical requirements for an efficient balancing strategy. Next, an optimal feedback control is designed on the enhanced dynamics model to minimize the rotational kinetic energy and leveling accuracy as key performance measures of the problem. The simulation results and comparative evaluations with a previously validated method verified that the proposed modeling and control approach is effective in achieving an accurate mass balancing while providing a convenient and methodical analysis and design procedure.