| With the growing number of electronic control unit(ECU) used on cars, automotive network turns into automotive electronic development trend. Over a long period development, Controller Area Network (CAN) has become one of the actual car bottom bus standards. As a vehicle network diagnostic protocol based on CAN, ISO 15765 is currently widely used because of its merits on transmission mechanism, time control, error detection etc…ISO 15765 is more stringent on the time control of network layer and provides more comprehensive diagnostic services on application layer. How to reasonably set up the parameters to reduce the network layer transmission time and implement different diagnoses as per different requirements is still pending to research.Based on lots of domestic and foreign analysis data reading and analysison ISO 15765 protocols, this thesis carries out relevant research on the network layer, the application layer and diagnosis process of the protocol. First of all, by analyzing link layer arbitration mechanism of CAN bus and transmission mechanism, Stmin parameter model of the network layer is set up which uses network load rate and data frame priority parameters as constraints. Compared with the tradition parameter model, this model could reduce the average waiting time of the network layer in a multi-frame transmission. Secondly, in accordance with the characteristic of automotivecar body network and by analyzing the specific diagnosis service and process of the application layer, the colored Petri nets model of diagnosis process is set up by combining the colored Petri nets and process of diagnosis system. This model could be used to describe the logic relationship of communication of diagnostic instrument and ECU. Simulation shows this method would improve automotive network software development efficiency.Finally, the thesis introduces implementation of seat ECU diagnosis system, which is verified and analyzed by using CANoe simulation software to simulate the network environment. |
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