HYBRID SWITCHING ATTITUDE CONTROL OF UNDERACTUATED SPACECRAFT SUBJECT TO SOLAR RADIATION PRESSURE

In this paper, attitude control of an underactuated spacecraft with two control moments is considered. Both the case of two external moments, that can, for instance, be applied by thrusters or two internal moments, that can, for instance, be applied by reaction wheels, are treated. Both problems are known to be challenging, e.g., there exists no smooth or even continuous time-invariant stabilizing feedback law in either of these cases. Our controller is based on a hybrid switching feedback law that exploits an inner-loop controller and an outer-loop controller. The fast inner loop controller tracks periodic reference trajectories while parameters which determine the amplitude of these reference trajectories are adjusted by an outer-loop controller. We demonstrate through simulations on a nonlinear spacecraft attitude dynamics model that this switching feedback law successfully accomplishes rest to-rest reorientation maneuvers, even in the presence of solar radiation pressure disturbance moments or in the case of nonzero total angular momentum.