Motion Planning for Dual-arm Assembly of Ring-shaped Elastic Objects

This paper discusses a motion planning method for assembling a ring-shaped elastic part to a cylindrical part by using a dual-arm manipulator. When assembling a ring-shaped elastic part, it is important to keep the amount of elastic deformation as small as possible during the assembly task. To achieve this purpose, we show that it is effective to utilize the Covariant Hamiltonian Optimization and Motion Planing (CHOMP) method. We introduce an energy based objective functional that is obtained by adding a term related to the potential energy of the elastic object. This objective functional yields a trajectory where the deformation of the elastic object is minimized. At the same time, we modified the collision cost function such that the robot can approach to the assembly parts as much as permitted without colliding. To confirm the validity of the proposed planner, simulation results of the PR2 robot handling a ring-shaped elastic object are shown. We show that our modified motion planner is able to find a feasible trajectory keeping the deformation of the elastic object small, and we analyzed the objective functional weights to obtain smaller energy costs.