Research On Fault Diagnosis Strategy Of Heavy-duty Gas Engine

Natural gas engine due to the complexity of the electronic control system structure,the probability of failure will greatly increase the occurrence of failure will lead to electronic control system can’t work properly,resulting in the vehicle can’t be normal operation,so the gas machine ECU must be equipped with fault diagnosis system.The system can monitor various faults in real time and accurately.After the fault information is stored and the faults occur,corresponding measures are taken to ensure the driving safety of the vehicle.Since this research object is a heavy-duty gas machine,the diagnostic communication protocol adopted in the fault diagnosis system is the J1939 protocol.Need to complete the construction of J1939 protocol stack,mainly the construction of data units and the construction of interface functions.By studying the methods of fault diagnosis and related standards,the overall design of gas engine fault diagnosis system is proposed.The design is divided into fault management module and fault monitoring module.Fault management module is divided into diagnostic coordination module and fault path module.The working process of the fault diagnosis system is as follows: The fault monitoring module determines the fault type and the fault attributes through the fault diagnosis strategy and the anti-vibration mode.Fault path management module’s role is to use fault path handling and fault status controller to control the fault indicator light,fault code and freeze frame storage.Diagnostic coordination module’s role is to calculate the priority,the corresponding suppression procedures,mutual exclusion algorithm to determine the priority of various failures and treatment.Use MATALAB/SIMULINK to build the fault diagnosis model of typ ical components and simulate it to verify the reliability of the model.The simulation results show that when the accelerator pedal sensor determines the final failure,the corresponding treatment method and substitute value should be adopted instead.When the coolant temperature sensor and the ECU itself determine the final failure,the value of the relevant sensor is used instead to ensure that the vehicle O f the normal driving;when the engine has a fire failure,the battery voltage is normal,the coolin g water temperature,the engine speed within a certain range,without other failures,It can be determined by the instantaneous acceleration of each cylinder to determine whether there is a cylinder gas machine misfire failure By detecting the signals of the four pins IA,IP,UN,and VM,the fault diagnosis of the wide-area oxygen sensor can be realized.The DIAHG and DIAHD pins can also be used to separately collect the gate and drain of the MOS transistor in the heating loop.The signal to achieve the fault diagnosis of the MOS tube.Set up a fault diagnosis test bench to verify the fault diagnosis control strategy to ensure the correctness and reliability of the control strategy.By testing the failure of the test bench simulation equipment can simulate the occurrence of failure,and then by the USB-CAN will transmit the fault code data to the Labwindows upper computer interface,the interface can be displayed on the fault data after the fault.By reading the fault code data,observe whether the interface can accurately display the fault code in a timely manner,and check whether the fault code data is co nsistent with the underlying fault code,so as to achieve the correctness of the fault diagnosis strategy.Through repeated experimental data,we can verify the correctness and reliability of the cooling water temperature sensor fault diagnosis strategy,accelerator pedal fault diagnosis strategy,ECU own fault strategy,oxygen sensor diagnosis strategy,and engine misfire fault strategy.