Model Based Design Of OBD Fault Diagnostic Instrument

With the increasing complexity of automotive electronic systems function, the traditional software development mothod are increasingly unable to meet market demand. The traditional development methodology contains requirements, design, implementation, and testing stages. The four stages are isolated from each other. Model Based Design(model based design, MBD) and automatic code generation method of software development is an effective and promising way to solve the challengs above.In the paper, know-how and a new software development platform for control-based automatic code generation technology is developed, andapplied in software development of on board fault diagnosis instrument.A complete automatic code generation and downloading system, includes the following components: model-based automatic code generation; automatically compiled code; automatic download of application; real-time monitoring of applications running conditions.Through this technology, the algrithm of the controller required for all of the C code are generated, consisting of the hardware driver and upper layer algorithms, without manual writing any code. It improves the efficiency of the software development siginificantly.For OBD diagnostic development, it analyzes the automobile fault diagnosis system mainly four standard, namely ISO 15031, KWP 2000, ISO 15765 and SAEJ1939-73,we use vehicle diagnostic protocol ISO 15765 based on CAN bus. The autor studies the auto diagnosis system architecture, and analyzes in detail from application layer, network layer, data link layer and physical layer four aspects based on ISO 15765 OBD diagnosis system.In the Simulink we build upper algorithm and hardware driver, and download them to the OBD fault diagnosis equipment. Meanwhile, through simulation and real vehicle tests, the basic function of OBD diagnostic system is verified, and the correctness of the automatic code generation is also verified.