Hybrid attitude tracking of output feedback controlled rigid bodies

In this paper we address the problem of output feedback attitude control of a rigid body in quaternion coordinate space through a PD+ based tracking controller using switching technique to obtain stability for all initial values. Assumptions on earlier results where either the initial state is considered bounded, or the attitude error for all time is less than 180 degrees, is removed by applying switching technique, also including hysteresis for robust stability. More precisely, we show uniform asymptotic stability in the large of a set containing the origin for the closed-loop system in the presence of unknown, bounded input disturbances. Simulation results are presented to verify our theoretical findings, showing that the system stabilizes as expected, even with high initial estimated velocity error.