Nonlinear digital scheme for attitude tracking

The paper deals with asymptotic tracking of a reference attitude trajectory for rigid spacecraft. Based on differential equations that describe the error dynamics with respect to a given reference trajectory, the design procedure is formulated as a stabilization problem. Both gas-jet and reaction-wheel control modes are considered. Under mild smoothness assumptions on the reference trajectory, a nonlinear digital controller is proposed based on a multirate control strategy. Simulation results show the effectiveness of the proposed digital control scheme