UNIFIED APPROACH TO ADAPTIVE VARIABLE-STRUCTURE CONTROL FOR ATTITUDE TRACKING IN VARIOUS PARAMETERIZATIONS

The adaptive variable-structure control for attitude tracking is examined in general terms. The earlier formulation developed in terms of quaternion components is reexamined in a more general form suitable for other attitude parameterizations. The adaptive control laws are modified to address the unwinding phenomenon and to guarantee that the closed-loop error dynamics evolve along the shortest arcs. It is shown that different parameterizations provide additional degrees of freedom for improving parameter adaptation and closed-loop performance.