| Research Abstract |
The final purpose of this research is to design a flexible and stable navigation algorithm for multiple mobile robots and human beings it they move simultaneously in the same 2-D (two-dimensional) environment including static obstacles. This on-line navigation algorithm is designed by mixing implicit and explicit communications, In the implicit communication, each robot has a set of outer sensors and a set of on-line traffic rules, and then sequentially determines its behavior by processing sensor information in the rule set. On the other hand, many robots communicate with each other via an explicit devise, e.g., a radio Ethernet in the explicit communication. In general, the explicit communication is more stable but slower than the implicit communication. Therefore, a part of the navigation algorithm adopts the implicit communication if its stability is maintained. Then, the others use the explicit communication.
(1)Designing a robust sensor-based navigation algorithm for a single robo
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t : A mobile robot Nomad200 (Nomadic Co., USA) has a ring of ultrasonic sensors, a ring of infrared sensors, and a laser range finder. Even though the robot uses three different sensors, it unfortunately misunderstands the Euclidean distance to an uncertain static obstacle. Moreover, the robot misunderstands its own position and orientation by a dead-reckoning system based on encoders of wheels. Therefore, we design a flexible and stable navigation algorithm that a mobile robot arrives at the neighborhood of its destination in an unknown 2-D environment while overcoming sensor, position and orientation errors. In addition, because of no obstacle information, a mobile robot sometimes selects an extremely longer path to its destination. To overcome this defective point, we modify the proposed algorithm into a near-optimal sensor-based navigation algorithm.
(2)Developing a sensor-based navigation algorithm based on the implicit communication between multiple robots : We design a sensor-based navigation algorithm for multiple mobile robots which communicate by sensor information and traffic rules. Three or more mobile robots Nomad200 and Nomad l5Oplus supervised by this algorithm run simultaneously. In this case, some of the robots collide with each other, or some of them cannot avoid a static obstacle or a wall. The reason is as follows : two active sensors discharge infrared and ultrasonic waves which are interfered each other in a complicated environment, For this reason, we check a bound of the sensor-based navigation or the implicit communication for multiple robots by three kinds of outer sensors.
(3)Developing an on-line navigation algorithm based on the explicit communication between multiple robots and human beings : We design an on-line navigation algorithm for multiple mobile robots which communicate with each other by a radio Ethernet UDP (User Datagram Protocol). Furthermore, many human beings are in pursuit of a tracking vision system (FUJITSU Co.), and consequently their behaviors are communicated to all robots by the explicit communication. By the on-line navigation algorithm based on the explicit communication, a robot arrives at its destination surely after avoiding human beings and the other robots. Less
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