The Research On The Air-Fuel Ratio Adaptive Hybrid Control Strategy In The Transient Conditions Of Gasoline Engine Based On Chaotic Sequence

With the development of the economic, the car is no longer a luxury in people’s eyes, the car has entered the ordinary people’s life as a kind of daily consumer goods-transportation. China is accelerating into the automobile society also, which with encouraging data behind caused our further thinking also. With the development of transportation, the increasing perfectness of transportation network and the transportation network has brought us infinite convenience; however the vehicle emissions have become one of the important sources of urban air pollution, which has seriously affected our lives and the sustainable development of environmental protection. At present, the increasing shortage of global energy reversed transmission to improve the world automobile exhaust emission standards and regulations, auto environmental protection and energy saving, reducing the discharge of pollution are a looming problem of the transportation industry, the study on the energy saving and emission control of gasoline engine has important practical significance. The Port Fuel Injection (PFI) gasoline engine is still a dominant position in the market of commercial engine in our country; gasoline engine performance, fuel economy, emissions and optimum air-fuel ratio control research are always the most critical and difficult problems for researchers. Air-fuel ratio is one of the important reflect indicators of emissions, performance and fuel economy of gasoline engine, the precise control of air-fuel ratio can improve the overall performance of the gasoline engine, reduce harmful emissions effectively as well; But under transient conditions, many factors such as the throttle mutation, transmission time delay of oxygen sensor, the oil film dynamic, which would make air-fuel ratio control deviation, and greatly affect the three-way catalytic conversion efficiency; Therefore, how to control the transient air-fuel ratio to meet the highest conversion efficiency requirements accurately, have important realistic meanings.Based on the Port Fuel Injection (PFI) engine whose market is the biggest in current, this paper studied the transient air-fuel ratio fluctuation, the results obtained in the following aspects:(1) According to the characteristics of the transient air-fuel ratio control system, combined with the physical properties of engine established automobile engine average model. And with the tools of MATLAB/SIMULINK, formatted the structured simulation model, using the experimental data of engine in steady/transient conditions, verified the engine model by simulation experiment.(2) Based on the multidimensional nonlinear characteristics of engine air intake flow, using chaos theory identified the chaos time series of gasoline engine transient condition of inlet flow rate, and also using phase space reconstruction technique resume the multidimensional nonlinear characteristics of intake flow time series, set up a new kind of chaotic time series BP neural network predictive model, and applied to the engine air intake flow, reduce the deviation of air-fuel ratio control for the intake flow measurement error.(3) In transient conditions, the oil film dynamic effect makes the air-fuel ratio deviation from the theoretical value, and it is hard to measure the oil film dynamic parameter directly by the method of the determination, which should estimate accurately through effective indirect method, the fuel dynamic compensation scheme is put forward effectively. Therefore, in order to improve the control accuracy of transient air-fuel ratio, the writer using the chaos sequence support vector machine (SVM) model to simulate the oil film dynamic parameter online identification, designed a new online identification model based on the oil film parameters of fuel dynamic compensator, to fuel dynamic compensation of the oil film effects.(4) In the feedback control system of transient air-fuel ratio, because the sensor transmission is delay, and the feedback data is the value of the after burning, which make the control system not correct system deviation timely before combustion, not meet the real-time requirements, and not improve control accuracy. In order to improve the real-time performance of control system, and reduce the Air-Fuel ratio deviation caused by sensor transmission delay, this paper puts forward a new kind of chaotic time series BP neural network predictive model of the transient air-fuel ratio. Finally, gasoline engine transient air-fuel ratio composite adaptive control model which based on chaotic sequence has been set up, this model is mainly making up of the inlet flow prediction model, the oil film dynamic compensation model and transient air-fuel ratio prediction model, the effectiveness of the proposed control model is verified by test bench.