Robust Adaptive Tracking of Rigid-Body Motion With Applications to Asteroid Proximity Operations

This paper addresses the coupled position-and attitude-tracking control of a rigid spacecraft in the proximity of asteroids, where multiple, complicated, unknown perturbations resulting from highly uncertain environment must be dealt with. Dual quaternions are used to formulate the tracking error dynamics in a compact manner for unified translational and rotational control law design. A robust adaptive control scheme is then developed from an originally model-dependent controller by introducing an adaptive algorithm to dynamically adjust the compensation for perturbations due to parametric uncertainties and external disturbances. The proposed method has a simple structure and is computationally efficient, since it requires no information about the unknown perturbations and involves only two adaptive variables. Numerical simulations for asteroid landing and hovering control are presented to verify the effectiveness of the proposed methods.