Balance motion generation for a humanoid robot playing table tennis

Rapid advancement in the field of humanoid robot has been on-going in the last ten years, however, the common goal that robot can interact with human being to achieve a complicate task remains a difficult problem. We take table tennis playing as a demonstration to study how a humanoid robot shall interact with the environment and human beings and developed a humanoid robot ´Kong´ that can play table tennis and rally with a human player continuously. This paper focuses on robot´s stability keeping during table tennis playing. This problem becomes crucial due to the recoil force resulted from large arm acceleration. We introduce an optimal momentum compensation method and a position-based impedance control scheme to generate body motion so that the robot absorb the recoil force and ensure successful hit to the ball. The experimental results demonstrate that the robot is capable to rally with a human player and can act against the recoil force to maintain stability.