Development Of Ignition Engine Misfire And Oxygen Sensor Fault Simulation System

With the increasingly strict emission regulations and the continuous improvement of vehicle performance,on board diagnosis system(OBD-II)has higher requirements for real-time emission monitoring and fault diagnosis of vehicles.There are many kinds of automobile faults,so it is very difficult for actual engine fault state to test software and verify function.Fault simulator system shielding control of incoming normal ignition signal causes engine misfire.The fault simulation system shields the original ignition signal to cause the engine misfire,and deteriorates the original oxygen sensor signal to produce the oxygen sensor fault signal,which verifies the reliability of the fault diagnosis function of the OBD-II system.This paper is based on the MC9S12XET256 microcontroller to develop an ignition engine misfire and oxygen sensor fault simulation system.Develop,test and verify of fault diagnosis algorithms for OBD-II misfire and oxygen sensor fault.The main contents are as follows.(1)Based on the function requirements of the fault simulation system,the 16-bit microcontroller is used as the core board to complete the system hardware design.It mainly includes minimum system design,power supply module,raw signal acquisition circuit,ignition coil drive circuit,communication circuit and DTA conversion circuit design.(2)The system design is modular and hierarchical.Based on Code Warrior development environment to write the base software layer clock,communication,ATD,ECT and application layer program.The main tasks of the application layer are original signal acquisition,misfire fault simulation,oxygen sensor fault simulation,interruptions and system error.Developing management software based on Qt compiler environment.The management software and the controller communicate to achieve fault simulation parameter set and fault simulation control.The main functions include communication setting,fault simulation parameter setting and data showing,storing and playing back.(3)Use signal generator to generate original signal for system hard and software debugging.The system tests single-cylinder periodic,continuous,complete misfire and multi-cylinder intermittent periodic misfire.Build an oxygen sensor deterioration model using Simulink.The oxygen sensor waveform simulates for short to power,short to ground,heating fault,phase delay in the sensor signal,and periodic expansion of the signal.A comparison of the waveforms of the bench test detection of the oxygen sensor fault and the Simulink simulation waveforms to verify function of the system.