Global adaptive stabilization using output feedback for spacecraft attitude tracking

In this paper, we construct a nonlinear adaptive controller for stabilizing spacecraft attitude tracking dynamics. The body inertia matrix is assumed to be completely unknown and the control torque is computed using only angular position (attitude) measurements without requiring the body angular velocity. In the process of synthesizing the controller, we never make any additional assumptions such as availability of the lower and upper bounds on the eigenvalues of the unknown inertia matrix or a priori upper bounds on the signals of the desired (reference) trajectory and their higher time derivatives. In addition to a stability proof, numerical simulations are also presented that show the effectiveness of the proposed methodology.