Contact Force Observer for Space Robots

In this paper, the problem of estimating a contact wrench at the end-effector for a space robot is addressed. To this aim, a generalized force observer based on a base-joints dynamics is first reviewed. Then, a different formulation is proposed, which is based on a centroidal-joints dynamics. The proposed observer features interesting decoupling properties from the base linear velocity that lead to a more practical and better-performing estimation when limitations in real space scenarios are considered. The two observers are compared and the advantage of the proposed one is shown through a simulation example featuring a free-floating robot composed of a 7 degrees-of-freedom (DOF) arm mounted on a 6DOF moving base.