A novel force-velocity field for object manipulation with a model-free cooperative controller

When robots grasp a rigid object, homogeneous holonomic constraints give rise to stiff nonlinear constrained dynamics. As a result, a smooth motion is preferred when grasping an object in a tight but gentle manner, making it a difficult control problem that increases when uncertainties and unmodelled dynamics exist. In this paper, a fuzzy design is proposed by exploiting a physics-based orthogonalization of contact mechanics to produce desired velocity and force fields. The proposed scheme enables the regulation of the velocity component in order to navigate smoothly, while the force field enforces grasp at contact in the normal direction of the cooperative joint-velocity field. Then, the robust model-free controller is designed to track such orthogonal fields while enforcing cooperation among all robots, even under uncertainties and unknown dynamics. A representative simulation study is discussed to show the feasibility of the proposal.