THE ATTITUDE-CONTROL PROBLEM

A general framework for the analysis of the attitude tracking control problem for a rigid body is presented in this paper. In contrast to the approach that feedback linearizes the attitude dynamics to a double integrator form with respect to some minimal representation of the orientation, a large family of globally stable control laws are obtained by using the globally nonsingular unit quaternion representation in a Lya-punov function candidate whose form is motivated by the consideration of total energy of the rigid body. The controllers share the common structure of a proportional-derivative feedback plus some feedforward which can be zero (the model-independent case), the Coriolis torque compensation, or an adaptive compensation. These controller structures are compared in terms of the requirement on the a priori model information, guaranteed transient performance, and robustness. The global stability of the Luh-Walker-Paul robot end-effector controller is also analyzed in this framework.