Research And Design Of Air Fuel Ratio Control System For Electronically Controlled Gasoline Engine

With the rapid development of Chinese economy,car ownership increased year by year,which has a large proportion of gasoline vehicles,and increasingly stringent emissions regulations on the performance and emissions of the car made a higher demand.The main gasoline engine electronic control technologies are from engine management system monopolized by foreign manufacturers.Under the current situation,study automobile electronic control technologies to solve gasoline vehicle emission pollution and energy saving problems has important significance.For a complicated,nonlinear and time-varying engine object,it's difficult to calculate and design an accurate mathematical model;intake manifold oil film evaporation effect actually entering the cylinder of a gaseous fuel;transient air-fuel ratio control accuracy is poor;the accuracy and reliability of sensor affect values calculated;mixed gas combustion,exhaust gas transfer to the oxygen sensor,and oxygen sensor response all have some time delay,which need a lot of time calibration to make maps;parameters of conventional PID algorithm is fixed,which is difficult to meet the complicated working condition and parameter variation range of engine system requirements.These problems increase the difficulty of real-time control of the air fuel ratio.Based on the above background,this paper has carried out the research on the air fuel ratio control of electronic controlled gasoline engine.The main work is as follows:1.Analyzed the correlation principle of gasoline engine air fuel ratio control system,the effect of air fuel ratio and fuel economy,the control mode of air fuel ratio,the signal of oxygen sensor,and system composition in detail.2.Designed modified Smith air fuel ratio delay compensator,solving the process control of delay and Smith prediction model mismatch problem.Designed fuzzy adaptive PID air fuel ratio controller,to achieve dynamic adjustment of PID parameters,which has stronger adaptability to system.Designed air fuel ratio control strategy on different working conditions.Built simulation models,verified the air fuel ratio algorithm and strategy which are compared and analyzed with traditional PID algorithm.3.Designed gasoline engine ECU,whose hardware includes processing circuit for sensors,electronic control unit,drive circuit for actuators and interface wiring harness matching.Finished and programmed system software architecture,task state,control software and calibration software.Built engine test bench and verified the correctness and validity of the system.4.Completed some functions,including sequential fuel injection,ignition,idle speed closed loop and air fuel ratio control.The experimental results show that the fuel injection pulse width can be accurate to 1°CA;under low load,high load,and transient working conditions,the system can stably control air fuel ratio in the range of stoichiometric 14.7±0.5,three way catalyst has maximum conversion efficiency of harmful gases which meets emissions requirements.