Air Fuel Ratio Control Of A Gasoline Engine Based On Air Charge Estimation

Nowadays,pollution is increasingly serious so that some related rules have been formulated.Some researches show that the air-fuel ratio is one of the most important factor which impacts on engine power,economy and emission performance directly.This paper summarizes the engine air-fuel ratio control problem and analyzes the research status of the engine air-fuel ratio control.The most important thing which influences air-fuel ratio control is the estimation of the air mass flow into cylinder.A feed forward and output feedback control method was proposed.It has good control results with quick response and little deviation.Firstly,the paper modelled the throttle subsystem and the intake manifold dynamic subsystem.Even the dynamic of exhaust gas oxygen sensor was taken into consideration.Secondly,the cylinder intake air mass determines the cylinder fuel injection,which determines the engine output torque and has a direct impact on the engine air-fuel ratio output.Taking into account the actual engine control system,the transient phase of the cylinder intake air mass estimation of the engine signal real-time requirements are higher,so this paper used the faster updated intake manifold pressure and air flow sensor output signal as the cylinder intake estimate input of the algorithm.Then,taking into account the real-time performance of the engine system,the causes of the delay of the engine injection instruction are analyzed in detail.In addition,PI closed-loop error compensator based on oxygen sensor-based cylinder intake air mass estimation was designed.In order to eliminate the deviation caused by the fuel path delay and improve the control accuracy of the air-fuel ratio of the engine,engine cylinder air intake forecasting algorithm was proposed.Then,considering the uncertainty of the parameters and the uncertainty of the model,the feedback control is necessary for the system.This paper used the output feedback control strategy based on mixed sensitivity function and weight functions,which has good robustness.Finally,the controller is designed based on feed forward control and feedback control.Simulations of AFR control were carried out on en-DYNA and Simulink joint simulation platform.The feed forward and output feedback control method which is proposed can reduce the deviation.For practical engineering of air-fuel ratio control,this method has certain reference significance.