Contact states: representation and recognizability in the presence of uncertainties

Recognition of contact states is often necessary or preferred in planning and executing contact-based assembly motions in the presence of uncertainties. However, due to inevitable uncertainties, not all contact states can be identified at all contact configurations. A crucial question is what kinds of contact states at what kinds of configurations are impossible to be distinguished or identified. We address the question by analyzing the recognizability of contact states between convex polyhedral objects with both position/orientation and force/moment sensing in the presence of sensing uncertainties, i.e., by characterizing configurations where contact states are intrinsically indistinguishable with those sensing means. To reflect contact recognizability in contact representation, we propose a fuzzy definition of contact states. We further introduce a practical approach towards real-time automatic contact state identification based on the recognizability analysis