Abstract:

Attitude tracking problem with unknown friction torques of reaction wheels and external disturbances is addressed. A robust adaptive controller with parameter update law is proposed and analyzed. An indirect (nonregressor-based) approach used to deal with the effects of unknown friction torque and external disturbances is explored for the attitude control law. This is done by not focusing on friction torques and external disturbances, but on their bound, thus allowing the core information on friction torque and external disturbances to be extracted and used for controller design. The stability of the resulting closed-loop system is proved by application of Barbalat’s Lemma. Numerical simulations are presented to show the effectiveness of the proposed attitude tracking approach.

Key words: Spacecraft, Attitude tracking, Adaptive control, Robust control, Reaction wheel, Friction torque