Study On The Air Fuel Ratio Control For PFI Gasoline Engine Based On Model

With the flourishing in the global automotive industry today, the automobile production and sales records continue to be broken. Although car offers us convenience, it also leads power crisis and environment pollution. So Energy-saving and emission reduction have been put on the important agenda, which has caught the major automobile manufacturers and engine technology company's attention to update technology and optimize the product.Based on the MVEM(Mean Value Engine Model)model, the AFR(air-fuel ratio) control strategy was carried out in the PFI(intake-port fuel injection)engine. First, analyzing the existing AFR control's difficult problems, such as the air charge and exhaust effect, oil film dynamic effect, access to other nonlinear parameters. After deeply analyzing the above-mentioned factors, some solutions were put forward one by one. In order to obtain the nonlinear parameters, using nonlinear parameters of BP network prediction model, the efficient flow of cross-sectional area of the throttle valve and volumetric efficiency can be accurately available. To improve the air--inlet model, based on the MVEM model, considering the PCV (Positive Crankcase Ventilation) system, an improved MVEM model was established. Simulation results show that the accuracy of the improved model can be improved; Considered the dynamic effects of oil film on intake port, summed up a major deviation reason in air-fuel ratio control of gasoline engine under the transient condition, designed the film compensator. Using least squares method and generalized least squares method to identify the dynamic parameters, recognition results show that: generalized least squares identification accuracy is higher than that in the parameter identification accuracy, sampling points and sampling period of less accuracy of identification; Finally, the AFR model, oil film compensation model, film model were put forward. Simulation results show that: film compensator with the transient air-fuel ratio control accuracy AFR model is significantly better than non-film compensator AFR model. it is very significant to carry out the following work, such as subsequent code generation, hardware-in-loop simulation and model calibration.