Robust Nonlinear Attitude Stabilization of a Spacecraft through Digital Implementation of an Immersion & Invariance Stabilizer1

The paper deals with the problem of robust nonlinear attitude stabilization of a rigid spacecraft. In particular, an Immersion and Invariance robust attitude stabilizer is proposed, taking into account actuator dynamics in control design. The proposed continuous-time controller is then implemented under sampling using an approximated single-rate strategy to match, at the sampling instants, the zerogoing evolution of the off-the-manifold coordinates. Simulations show the effectiveness of the proposed controller.