Research On Fault Detection Of Communication Lines And Communication Real-time Performance Based On Marine CAN BUS

With the continuous development of industrial automation and the complexity of communication structures,the real-time and reliability problems have become a problem that needs to be solved urgently.In recent years,especially unmanned ships have made continuous breakthroughs in environmental monitoring,water rescue,etc.,which have become the focus of research in the marine military and research departments of all countries in the world today.In such an intelligent,information-based highly integrated platform,it also puts forward higher requirements on the reliability and real-time performance of data transmission.Among them CAN bus has outstanding advantages such as its strong real-time nature,high reliability,perfect function,simple structure,so it is more applied in the industrial communication such as ship communication.Although the CAN bus itself improves the accuracy of data transmission through error frames,cyclic check,bit stuffing,etc.,when the system appears physical failure,the system can only make failure response to the fault,and can not locate the fault point in time.The thesis conducts simulation experiments on various communication line faults,and formulates a complete detection scheme based on the corresponding fault phenomena such as voltage value and register value changes caused by different faults,making the system able to locate alarms and complete redundant bus switching.In terms of real-time,the traditional CAN bus adopts non-destructive arbitration technology for data transmission.However,with the complexity of the network structure and a large amount of data interaction,the bus load is too high,which may cause the lower priority sites in the network will experience longer delays due to multiple arbitration failures.Therefore,the thesis improves the real-time performance of the system by adopting the method of combining time-divided sending messages and dynamically changing message priority under the basic framework of the CANopen protocol.The thesis adopts TTCAN protocol to realize time-sharing messages,and improves the real-time performance by dynamically changing the priority of certain messages within the arbitration window of the TTCAN system schedule.Moreover,since the schedule of the TTCAN system stipulates that the time window length of each column must be the same and the worst transfer time of the message corresponding to each column time window is different,the scheduling table has the problem of waste of bus resources.The thesis adopts adaptive genetic algorithm to optimize the scheduling table of TTCAN system so as to achieve the purpose of improving bus utilization.Finally,after experimental testing,the reliability of the system can quickly locate the fault of the communication line and alarm,real-time aspects of the combination of TTCAN protocol and dynamic priority algorithm under high load conditions can effectively reduce the message delay compare with the traditional CAN protocol.