Distributed Communication System Design Of Remotely Operated Vehicle Based On Bus Redundancy

With the deepening of marine scientific research and requirement of ocean resources exploration, the development of shallow water ROV (Remotely Operated Underwater Vehicle) technology can't meet the requirements of marine exploration ability. The development of deep-sea ROV technology becomes more and more important. As one of the key technologies, communication system plays a vital role in deep-water ROV. Therefore, communication system of ROV needs to have high reliability, stability and strong real-time in complex environment of underwater. After researching on the ROV communication system, a distributed communication system based on dual redundant CAN bus for ROV is introduced. The significance is to verify the performance of ROV in deep-water environment through the study of communication system, and to provide reference for the realization of AUV (Autonomous Underwater Vehicle) model. The final experimental results show that the communication system meets the requirements of stability and reliability, and has strong real-time on data. In this paper, the specific process is as follows:First, the deep-sea ROV communication system consists of autonomous unit, attitude and promote unit, navigation unit, monitoring unit and the surface control unit. It adopts distributed communication in structure.Second, after taking comparison of advantages and disadvantages between RS232, RS485 and CAN bus which commonly used in ROV, CAN bus is selected to form the underlying network and RS232 is chosen to be the media of data transmission between surface control unit and autonomous unit. According to the requirement of real-time of communication system and considering the efficiency of data transmission and the complexity of data packets analysis, RS232 communication protocol and CAN bus application layer protocol are designed.Again, a hardware platform is designed for dual CAN bus. In hardware, the characters of ARM and x86 platform are analyzed and ARM-based hardware platform is introduced to achieve double CAN bus redundancy. ARM architecture reduces system's power consumption, avoids system instability caused by poor heat dissipation, and simplifies the design of power supply for communication system. The PC/104 expansion board for Communication proposed in this file is distinct with common PC/104 boards used for extension. The difference lies in that a ARM micro-processor is used on this expansion board. The realization of the extended function of this board is no need to be controlled by the mother board, and that this board can auto manage the communication of ROV and the implementation of dual CAN bus redundancy strategy without the intervention of mother board. Sequentially, reduce the workload for master board , improve the modularization of the system. PC/104 is used for master board to access communication management board and improve the scalability of the system. In software, the implementation of double CAN bus redundancy is mainly to solve two problems: fault detection and automatic switching of the bus. In this paper, bus failure detection and switching are accomplished by different settings and bus interrupt reception processing for master node and child nodes of CAN network, respectively.Finally, according to the real-time requirement of deep-sea ROV, the real-time operating system VxWorks is selected to be the operating environment of the communication system, and it is transplanted to the ARM platform. At the same time, software designed for communication system is accomplished in the integrated development workbench tornado, and the performance of the communication system is analyzed by the its development tools.