Study Of Intelligence Diagnosis For Electronic Controlled Diesel Engine Faults

Increasingly severity of energy crisis and stringency of exhaust gaslegislation, make electronic controlled common rail system being usedwidely, which gives a chance for performance optimizing of diesel engineand vehicle propelled by such an engine. But as common rail system is a verycomplicated control system, referenced to electronics, control theory,hydrodynamics and combustion theory, it is very difficult for normal serviceman to repair it with high efficiency as scarcity of relative knowledge.This project created intelligence diagnosis system for GD-1electroniccontrolled common rail engine, including on board detection of non-relativeemission faults, on board diagnosis (OBD) of emission relative faults anddiagnostic tool with Guidance Service suggestion (GSS) function. Without orwith little help from service man, intelligence diagnosis system can detectalmost all of electronic controlled component faults and some machine faults,which reduce the knowledge requirements of normal service man and giveadvantages to aftermarket services. So, intelligence diagnosis system is thelatest trend of fault detection domain of electronic controlled common railengine. Following are the main aspects of this project:1Hardware in loop equipment are developed, through which, diagnosisfunctions of foreign advanced electronic controlled fuel injection systemhave been tested deeply, at the same time, with the help of SAE J2012legislation, main frame of GD-1diagnosis system has been constructed. Moreimportant, a lot of diagnosis functions which are more comply with chineseaftermarket characteristics are added to this frame, so, the question of ‘Whatto do?’ of this project has been found out.2A lot of theories of diagnosis domain have been studied, consideringthe real time, exactness and robustness requirements of on board diagnosissystem, this project created a diagnosis theory named as experts system basedon signal character and muti-data fusing method, through which, the questionof ‘How to do?’ of this project has been found out.3Two level diagnosis criterion has been created, which means that allsensor signals are under the monitor of first and second level diagnosismodules. First level diagnosis module is used to check the physical character of sensor input signal, which can detect almost all of the circuit faults of thatsensor. Second level diagnosis module is used to detect the sensor signalpausibilty using some running logic of engine or vehicle, these kinds of faultsare often caused by function failures of sensor. Two level diagnosis criterionmake the diagnosis conclusion more credible.4For the calibration of diagnosis strategy, statistic analysis calibrationcriterion are created, during which, method of stratified sampling withoutrepeating is adopted in order to reduce average error of sampling. So,calibration can be changed to sampling and calculation for main parameters.It can effectively avoid the mistakes during calibration process caused byscarcity of experience for some fresh calibration engineer.5Fault forecast theory has been created, which can make maintenanceto replace most of repairs, and also can reduce repair costs, enhance the drivesafety. Fault forecast theory include following two characteristics:Faults of some components could be detected before the running ofvehicle or engine, which avoid the danger if running with these faults;Faults of some components could be detected during early phase, whichavoid the whole damage after the deterioration of these faults.6OBD frame and details of electronic controlled diesel engine arecreated for the firist time in inland, and lots of them are more comlpy withchinese after markets than those advanced foreign system, they are:In order to affirm and choose OBD items with little test costs, method ofraw choice based on experts’ knowledge and ESC emission test cycle areused, it is conclusion that, faults of fuel injection system, inlet airmanagement system and emission after treatment system are belong to OBDitems.For the fuel injection system, OBD faults could present in CPU, TPU,watch dog, injection driven module, driven circuits of injector, rail pressuresensor, and etc. For example, this project can judge accurate positions ofinjector driven circuits and can complete it at station mode;For inlet air management system, OBD faults could present in boostpressure signal, inlet air mass flow signal, and break out at inlet pipe aftersupercharger. Boost pressure signal drift and inlet pipe break out detectionfunctions are more comlpy with chinese after markets;For emission after treatment system, OBD faults could present in ureaquality, heating driven circuit, exaust temperature sensor, dosing valve and its driven circuit. Considering urea quality of some area is not good enoughin China, which can cause the dosing valve sticking, so, new function todetect this kind of valve stuck fault is created in this project.7After failure of electronic components, special strategies are triggeredto make sure of drive safety and continuity, when this faults is emissionrelated, these strategies can give attention to avoid exhaust level deteriorationat the same time.8In order to keep the integrality of diagnosis system of electroniccontrolled diesel engine, diagnostic tool was developed to be used ataftermarket, the software and hardware of it are chosen specially for servicecharacteristic.The diagnostic tool can not only read, clear and record diagnostictrouble codes, monitor running parameters, but also can detect faultsintelligently, which pay more attention to machine components. GSSfunction is integrated to diagnostic tool, which can guide maintain man toadopt intelligence diagnosis process appropriately to reduce service time.9After lots of tests on hardware in loop, engine rig and vehicle, thispaper made detailed validation of on board diagnosis system, which showsthat, it can detect faults effectively, and diagnostic tool can also do great helpto service at aftermarket.