The Mechanical Engineering Laboratory (MEL) is developing technologies for multi-robot collaboration in remote environments with the Toshiba Mechanical Systems Laboratory (TMSL). Human operators' delayed visual perception due to the communication delay over the network seriously affects the collaboration performance in the multi-operator-multi-robot tele-manipulation. We have built an experimental tele-manipulation test bed connecting the MEL and the TMSL to study the time-delayed remote tele-collaboration between two places. In the test bed, one operator controls her master robot nearby two slave robots in the work site and another from a distance. A local online graphics simulator without time delay is developed to cope with the communication delay and several multi-robot coordinated control strategies are devised to avoid the collision. To verify the validity of this simulator assisted approach, we demonstrated a maintenance work on a plant mock-up in the TMSL by two different slave robots and two distant operators in the MEL and TMSL respectively through an ISDN.

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.