Robot Network Based On 802.15.4

With the continuous development of ultra-large scale integrated circuit technology, sensor technology, control theory and artificial intelligence theory, robot system is becoming more and more powerful. Multi-robot system has been paid more and more attention because of its advantages such as high parallelism, high distribution, high robustness and low individual requirement over single-robot system. Multi-robot communication, which can provide current status, current mission and other information to other members in order to achieve the coordination, is becoming an active research area.In this paper, a communication network is developed for multi-robot system which can be used for map exploration, pattern formation and other occasions. These multi-robot systems have features like small size, high mobility, quick topology variation, low communication traffic and powered by batteries. The current communication platform used by multi-robot system is a commercial product and has two problems: one is the lack of source code, which prevents us from customizing; the other is the master-slave architecture, which lays burden on the central node, causing packet loss.RoboNet (Robot Network) developed in this paper is a multi-hop ad-hoc network. Robot node in this network works as a host running application programs as well as a router, which relays data for the other robots. When this relaying node fails, some redundant node can take up its responsibility, thus strengthens the survivability of the network. The specific content of this paper is as follows:(1) A printed circuit board is designed and assembled. With CC2430 as RF MCU and a ceramic antenna for radio transceiving, the system only occupies an area of 2.8cm x 3.5cm, making it suitable for small size battery powered mobile robots.(2) The IEEE 802.15.4 standard established for Low-Rate Personal Area Network is analyzed and adopted as physical and MAC protocol. The binary exponential backoff algorithm in physical layer reduces packet collision. The retransmission timeout mechanism in MAC layer improves reliability of packet delivery.(3) Dynamic Source Routing algorithm is implemented in network layer, making the system self organizable. The UART interaction layer defines frame format and provides services like data transceiving, parameter inquiring and setting for robots.(4) A test platform is developed to evaluate the performance of the system. The test compares the impact of different hops, different baud rate, different send interval, whether unicast or broadcast, whether the node is transceiving at the same time on delivery ratio. The suggestions for users and secondary developers of the system are also provided.The analysis of the test results shows that RoboNet is capable for map exploration, pattern formation and gains better packet delivery ratio than current one.