In the future, as the fields of activity for mobile robots extend, robots will have to coexist with humans in order to perform tasks. Then, robots will be expected to adapt to usual human environments and move autonomously. Of course, it is possible to implement high-level functions on a single robot. However, it is not feasible from the viewpoints of cost, robot size, technical difficulties and so on; hence, we will not require robots to have perfect faculties, and will instead have the environment (or the human) provide some of them (see Fig. 1).

• Environments provide faculties to robots - Environment design / Environment use

1. A study on problems of environment design: We put marks on objects in the environment. And the robots measure them and achieve tasks. The marks are artificial objects designed to be measured by the robots and thus give them information about not only their own positions and orientations but also task processing instructions. For example, if we put the marks on a book shelf and the books in it, the robots may pull an indicated book out of the shelf. It is a very general task.
2. A study on problems of environment use: The supply of energy is an important factor. It can be problematic for mobile robots to drag overlong electric cords. On the other side, the capacity of batteries is limited. Hence, robots need to use wall sockets and change sockets depending on their position in order to extend their range and operation time (see Fig. 2).

• The human provides faculties to robots

While dealing with multiple mobile robots, the system seldom has true autonomy. Hence we research operation methods to complement the imperfect faculties of robots. When many robots are present, it is impossible for the user to command robots individually and grasp the situation of the whole system. Hence, we deal with robots as a group and give orders to the group instead of commanding the robots individually. We also introduce a certain amount of autonomy into the robot system to complement the lack of commands (see Fig. 3).

Fig. 1 Human-robot coexistence