Automatic verification of contact states taking into account manipulator constraints

Compliant motion is required or desirable in many robotic tasks, especially assembly tasks. Both planning and execution of autonomous compliant motion requires the knowledge of contact states between parts in contact beforehand. Previous research has addressed automatic generation of contact states between rigid objects. However, not all such contact states can be possibly reached if a rigid object is attached to and moved by a manipulator due to the manipulator constraints. In this paper, we study the problem of finding feasible contact states between a polyhedral part A held by a manipulator with a fixed base and a fixed polyhedral part B. Given a contact state graph between the unattached part A and the fixed part B, our approach then attaches A to the manipulator model and checks the reachability of each contact state and the connection between two neighboring contact states by applying a virtual compliant controller to the manipulator to test possible compliant motions of A. Implementation results validate the effectiveness of our method.