Studies And Implementation Of Control Method For UEGO Sensor

Universal exhaust gas oxygen(UEGO)sensor has a wide range of air-fuel ratio measurement,is widely used in air-fuel ratio control system of the lean-burn engine.The sensor provides a more accurate air-fuel ratio signal for the automotive electronic control unit(ECU).The air/fuel mixture in the engine cylinder is controlled to the ideal air-fuel ratio,and then the air pollution caused by automobile exhaust is reduced.UEGO sensor must be combined with the controller to work properly.The characteristic of controller determines the performance of the UEGO sensor directly.The thesis studied on the control method and software of UEGO sensor controller.Based on the open-loop experiment in the air environment,the mathematical model of the temperature module was established.According to the non-linearity of the temperature and the heating limit of the start-up,a segmentation control strategy which combining slope heating with fuzzy PI was proposed.The open-loop experiment of the pump current module was carried out on the mixed gas distribution platform,and the mathematical model of the controlled object under different working conditions was established.The fuzzy PID control method was proposed for the perturbation of the model parameters.The system software of UEGO controller was developed,which consists of modules such as initialization,watch-dog,man-machine interface,host computer communication,temperature control,pump current control and air-fuel ratio calculation.The functions of temperature signal acquisition,pump current module control,measurement calculation and human-computer interaction was implemented.The PC monitoring software was developed based on LabVIEW to achieve functions of the control parameter settings,status monitoring,and the results of records and display.The air environment experiments show that the normal temperature start-up time is less than 20 s and the precision of temperature control is high.The pump current regulation time is 191 ms,and the dynamic response is fast with strong anti-interference ability.The dynamic experiment on the mixed gas platform is implemented,the results show that the UEGO controller can respond quickly for the change of the external working condition,and the dynamic performance is very good.