Elimination of unnecessary contact states in contact state graphs for robotic assembly tasks

Abstract

It needs much computation to develop a contact state graph and find an assembly sequence because polyhedral objects consist of a lot of vertices, edges, and faces. In this paper, we propose a new method to eliminate unnecessary contact states in the contact state graph corresponding to a robotic assembly task. In our method, the faces of polyhedral objects are triangulated, and the adjacency of each vertex, edge, and triangle between an initial contact state and a target contact state is defined. Then, this adjacency is used to create contact state graphs at different priorities. When a contact state graph is finished at a higher priority, a lot of unnecessary contact states can be eliminated because the contact state graph already includes at least one realizable assembly sequence. Our priority-based method is compared with a face-based method through statistically analyzing the contact state graphs obtained from different assembly tasks. Finally, our method results in a significant improvement in the final performance

A robot learning from demonstration framework for skillful small parts assembly

“…In view of the pick-and-place processes only one policy is learned for the whole assembly process therein, never-theless, it may fail to work in the small parts assembly tasks since features of the assembly motion vary significantly between the two phases. Another formulation of small parts assembly tasks is peg-in-hole problem [14,16,26] and Reinforcement Learning (RL) based methods are widely applied to learn a decision making policy that maps states to actions through trial-anderror [7,8,12,27]. RL-based approaches typically require the robot to explore the state space.…”

Investigating the Conditions of Automatic Assembly

“…In [11] proposes a new method for eliminating unnecessary contact states in the state graph corresponding to the problem of assembling polyhedral joints by a robot. The method signi cantly reduces the number of contact states and transitions in the nal contact graph when generating an assembly sequence.…”