The Implementation And Application Of Vehicle Diagnostic Protocol KWP2000

To meet more and more strict emission regulation and to improve economy, power nature, security and comfort of the vehicle, the application of electronic technology is a current trend of the industrial development of automobile. Wide application of electronic technology makes the systematic structure more and more complicated. When breaking down, to judge the trouble reason and find the fault part becomes more and more difficult. Under this background, the diagnostic system has been developed during the development of electronic control unit to realize on-board and off-board diagnosis. So the development of diagnostic system is of important practical significance.In this dissertation, the diagnostic protocol KWP2000 is deeply researched based on the document and material study of the domestic and international relevant fields. Also the development and application of the protocol is carried out. The main research contents include several respects as follows.Firstly, the characteristic and architecture of diagnostic protocol KWP2000 are introduced. According to the OSI seven layers basic reference model, the communication system is divided into three layers according to KWP2000, including physical layer, data link layer and application layer. The functions and technology characteristics of these sub layers are analyzed in detail, as well as communication relationship between these layers.Secondly, the dissertation focuses on the implementation technology of data link layer and application layer, furthermore, proposes corresponding technology solution approach. On data link layer implementation, a software mechanism based on state switching is given in the dissertation. The key technology, such as initialization process, data segmentation and reassembly,timing mechanism, error handing and arbitration is analyzed particularly, thus the complete communication network based on K line is implemented. On application layer implementation, the software structure and interface design is brought forward in the dissertation. The implementation process of unified diagnostic services, such as start diagnostic session, security access and tester present, is also analyzed.Thirdly, the application of diagnostic protocol on specific diagnostic system is discussed. The diagnostic system provides some diagnostic functions, such as fault diagnosis and online programming. On fault diagnosis, some existing fault detected methods are explored, combined with on-board diagnosis strategy. The functionality of the fault retention manager and self-healing mechanisms are analyzed. The method of how to combine on-board and off-board diagnosis strategy is discussed particularly. To solve problems of ECU test and monitor in non-laboratory condition, a method of ECU online programming based on diagnostic protocol is proposed.Finally, the function and performance of diagnostic software is verified with Softing which is a diagnostic system development tool. The test result shows that the proposed software solution is feasible and effective.The main task of the dissertation is implementation and application of diagnostic protocol KWP2000 on the specific ECU. Furthermore, some explorations on method of software design for diagnostic system has been done, which is of great practical significance.