Adaptive Backstepping Control for Attitude Tracking of a Spacecraft

The problem of adaptive attitude tracking control for a rigid spacecraft with uncertain inertia matrix is addressed by means of backstepping technique. As a stepping-stone, we first construct a nonadaptive control scheme that is dependent on exact knowledge of the spacecraft inertia matrix. The control scheme is then redesigned to be adaptive, which is independent of any inertia parameters. The Modified Rodrigues Parameter (MRP) is adopted as attitude variable due mainly to its global nonsingular description when combined with its shadow sets. One salient feature of the proposed controllers is that they allow integral control action, which can potentially eliminate or reduce steady-state attitude errors in the presence of constant external disturbances. Simulation results for the derived controllers demonstrate the efficiency of the proposed backstepping strategy in achieving attitude tracking for spacecraft with inertia uncertainty.