Research On Control Strategy Of ECU Fault Diagnosis System For High Pressure Common Rail Diesel Engine

The electronic control system structure of high pressure common rail diesel engine is precise and component is various, so the probability of fault is higher. These fault not only cause the problems of the electric control system and affect the normal operation, but also lead to the increase of emissions. High pressure common rail diesel engine ECU must have fault diagnosis system which can accurate monitoring all kinds of faults, storaging and responsing the fault information timely, taking corresponding fault handling, to ensure engine in the presence of faults can operate safely. Because the control of the fault diagnosis system is complex, the control strategy of the ECU fault diagnosis system of high pressure common rail diesel engine must be studied deeply.The control scheme of ECU fault diagnosis system of high pressure common rail diesel engine was put forward by studying the standard and diagnosis method of fault diagnosis system and combing with the ECU of the high pressure common rail diesel engine developed by the laboratory. The control scheme is divided into monitoring module and fault management module, and fault management module is divided into fault path management module and fault management module. According to the method of fault detection and time pre chattering, the fault types and fault attributes are established. Fault path management module uses the fault path processing method and the fault state controller to solve the fault classification, MIL lamp working mode and storage of frozen frame, fault code and so on Diagnostic coordination module through the suppression of procedures, priority calculation, mutual exclusion series algorithm to establish the processing priority of all types of fault and the corresponding fault treatment.Studying character of accelerator pedal, coolant temperature, common-rail fuel pressure, fuel injector, sensor of SCR in depth. The corresponding diagnosis strategy is designed for the prone to fault. Using rationality and scope of the fault detection method can real-time accurate to judge the fault type, through the time state machine determine the fault properties, use reduces torque (fuel injection quantity restrictions), instead of other sensors, calibration default value replace the effective processing all kinds of faults, and fault recovery process take ramp function of the fault default values to a certain slope and the current value of a signal, successfully avoid the engine rotating speed mutation in.The fault diagnosis system control strategy model of typical components based on software platform of MATLAB/Simulink and StateFlow was established, the simulation test was carried out. Results show:When the accelerator pedal, common rail pressure sensor fault, by the time state machine determine as final fault. Diagnosis system select corresponding processing method and instead of default value to ensure safe operation under engine in the presence of faults; when the ECU of its own parts, fuel injector, the SCR system cooling water temperature fault. Diagnosis system take place of other sensors, default calibration value and fuel injection quantity restrictions to alert the driver to repair them as soon as possible. To prevent pollution because of the fault of egine lead to excessive emissions on the environment. The identification of fault disappears, the default value of the fault is made by using the slope function method to a certain slope fault recovery to the current value, prevent the engine speed mutation affecting road safety.