Research And Design Of The On-Board Diagnostics System

With the development of automobile electronic technology, electronic controlunits integrated in the car are increasing, and the control system of electronic controlunits is becoming more and more complicated, fault of any emission-related electroniccontrol unit could lead to excessive automobile emissions, therefore, research anddevelopment of On-Board Diagnostics has important practical significance.Aiming at the problems of On-Board Diagnostics in development process, thispaper studies fault diagnostic strategies and methods of On-Board Diagnostics, designsand implements the diagnostic communication. Firstly, a description of developmentoverview and basic functions of On-Board Diagnostics is introduced in this paper, and abrief introduction of CAN bus network communication technology of On-BoardDiagnostics is given. Secondlly, a need analysis of diagnostic system according tonational standards is made, the research of fault diagnostic process and diagnosticcommunication is described, and the design of overall framework of system software isgiven. Thirdly, the research and design of key functional modules in the system by usingmodular design method based on software framework is described. Fourthly, typicalfaults diagnosis processing and communication functions in On-Board Diagnostics arerealized in this paper.Finally, the system software is debugged in CodeWarrior platform, and the testresults are analyzed by using oscilloscope in hardware platform. The experimentalresults show that the system complies with the CAN bus communication protocolstandards, and be able to accomplish the diagnosis and process of typical faults.