Cooperative Manipulation of Objects by Mobile Robots with Tools

In this study we propose a method that multiple mobile robots use tools to accomplish tasks easily and efficiently. A single robot is likely to have limited ability so we adopt multiple mobile robots in our system. Multiple mobile robots, however, cannot always accomplish cooperative tasks efficiently because of their motion errors and lack of information about handling objects. Therefore, we adopt a system that multiple mobile robots use auxiliary tools in cooperative to accomplish tasks more efficiently (Fig. 1).

The difficulty of handling tools is less than that of handling several objects. Robots can choose appropriate tools to suit the situation and a resultant force can be generated by using tools. We classify several tools into two groups considering their characteristics: (1)rigid tools like sticks and plates and (2)flexible tools like strings and fabric. The robots make use of characteristics of tools and manipulate objects easily and efficiently. Using rigid tools enable the robots to give constraint hardly to objects and to extend their manipulating area and power. For example, the robots can manipulate objects in a narrow space where the robots cannot approach by using a thin stick, can transfer a heavy object by using a stick as a lever, and can line up objects by using a long stick. When the robots manipulate objects by using a stick, we decide the direction of approach that the robots can line up objects simultaneously (Fig. 2). Using flexible tools enable the robots to cope with objects that exist in complicate environment. For example, objects can be transferred stably and objects can be divided into some groups by using a piece of string. When the robots transfer objects by using a piece of string, we plan the paths of the robots that objects can be divided into multiple groups (Fig. 3).

We develop a system that four wheeled robots are equipped with toos handling module. The effectiveness of the proposed method is shown in the experiments of prototype robots performing objects transportation task.

Keywords: Tool, Multiple Mobile Robots, Cooperation, Manipulation, Transportation