Design Of Vessel Structure Safety Monitoring System Based On CAN Bus

Vessel structure safety monitoring system can be used to implement real-time monitoring for strain and evaluation of vessel structure. safety By the comparison and analysis of RS-485 bus technology and CAN bus technology, characters of general operation system and embedded operation system, vessel structure safety monitoring system integrating CAN bus technique with embedded system technique was demonstrated, which can be described from two parts in the structure: data collection module based on CAN bus and the host system based embedded operating system Windows CE.NET.The first part is data collection module,which takes charge of collecting strain data and transferring them to the host over CAN bus. This part involves design of Software and hardware of the module. In designing of hardware, singlechip SST89C54, stand-alone CAN controller SJA1000 and AD converter AD679 were selected to establish the kernel controlling part of data collection module, and interface connection of main chips and hardware anti-jamming technology were described in detail. In the implement of software, procedural flows of main functional modules such as initialization, data receipt and transmission were particularly described. In addition, Considering factors of influencing measurement precision of strain, corresponding technology, including software correction method of non linear of strain measurement, three wires connection technology for strain resistance and four wires detecting technology for measurement bridge power, were adopted to improve measurement precision of strain.The second part is the host system based on Windows CE.NET. The system is composed of customization of the kernel of embedded operating system, design of CAN adapter driver and application system. At first, according to difference of resources of hardware and requirements of application, functional modules in Windows CE.NET were tailored , customized. Secondly, in the design of stream interface CAN adapter driver, process of interrupt disposal in Windows CE.NET was analyzed, and CAN interrupt serve thread(IST), receipt and transmission of message was described in detail. In addition, the thesis discussed CAN driver's influence on response ability of received message, and gave a method with a real-time response on received message, which set the size of receiving buffer queue and the critical number of received messages in it according to requirement of real-time response time and transmission rate of CAN bus. Thirdly, for application system, the thesis specified program flow of important functional modules such as main flow ,self check and initialization, parameter setting and modifying, calibration of strain benchmark at a sampling position and measurement controlling of strain.The third part is customization of communication protocol. According to the feature of the monitoring system, Master-slave communication mechnism was set up. Setting and querying of parameter and controlling of sampling and transfers of sampling modules and channels were implemented.