We developed a robot system which can play one-on-one volleyball games with a human player. It can not only hit a flying ball back to the player correctly but also have various autonomous functionalities to interact with humans necessary for playing games, i.e., it can pick up a ball of a requested color by recognizing voice instructions, can locate the players by recognizing their faces, and can shake hands. This robot performed the entire game sequence over 100 times at a company-sponsored exhibition, where the ball rally continued over 25 times with an arbitrary player. In this paper, we mainly describe the real-time visual feedback system of the robot which is essential for playing ball games.

A new master-slave manipulator (MSM) with different configurations and different degrees of freedom (DOF) has been developed. It consists of a general master arm using pantograph mechanisms and a seven degree of freedom slave arm with a redundant joint. Symmetric bilateral control using a virtual internal model and redundant arm control with a singular configuration are used to improve the maneuverability of the MSM. The developed MSM has been confirmed to have good maneuverability from basic experiments. This paper describes the mechanisms, control methods, and experimental results of the MSM.