Optimal Control for Spacecraft Large Angle Maneuvers Using H infinity Linear Varying Parameter Control Techniques

Abstract

This study investigates the possibility of designing and implementing a Linear Parameter Varying controller with H infinity performance criteria integrated into the synthesis of the controller for a spacecraft undergoing a large angle maneuver about its principal axes. Towards this end, Cayley-Rodrigues parameters were used to model nonlinear spacecraft dynamics and to ensure up to 180 degerees of rotation about the principal axis without singularities in the system. Several linear parameter varying (LPV) controllers with different parameter ranges were designed and the closed-loop performances were compared with respect to the H infinity upper bound gamma. The optimal gamma value obtained is roughly 0026. Two resulting LPV controllers were then examined through a series of simulations in order to observe both fuel economy and disturbance rejection capabilities for these controllers. The two controllers demonstrated fast response times and good disturbance rejection. It was also found that the controller with the smaller performance level gamma did perform better. Both control systems seemed to show some positive signs of enhanced fuel economy. There was chatter involved with certain aspects of the controller input profiles, but the simulations showed evidence that this was not caused by external disturbance, and can be eliminated by proper selection of weighting functions in the control design process.