Model-based Gasoline Engine Air-fuel Ratio Control Technology Research

In order to improve the performance of power, economy and emissions, the accurate control of air-fuel ratio is a key point of the control technique for modern vehicle gasoline engines. In the traditional control, the control parameters obtained by large numbers of calibrating experiments are made the tables, and they are looked up as engine is running. The model based control strategy and algorithm is applied to air-fuel ratio control under steady conditions and transient conditions, which not only can reduce the calibrating work, but also can improve the robustness of the control system.On the base of analyzing the dynamic characteristics of air intake and fuel film evaporation, the air-fuel ratio's mean value engine models (MVEM) composed by air intake model and fuel dynamic model are constructed. The pressure losing term and the design parameter replace the volumetric efficiency in the air intake model, which is favor of not only designing controller but also predigesting the calibrating work for different engines. The simple and effective calibrating method for parameters of fuel dynamic model is attained by theoretical analysis and simulating experiments. The complicated non-MVEM is constructed so as to validate MVEM. The bench experiments are used to identify the MVEM's parameters and to validate the complicated non-MVEM. Then, the scheme that combines the method of complicated model validating simple model and bench experiments is used to validate the air-fuel ratio's MVEM. The validated results of MVEM indicate that the MVEM are accurate enough for air-fuel ratio's control, furthermore, it has a simple structure.After analyzing the signals of the manifold pressure sensor, the sampling algorithm is received by the spectrum characteristics. Air-fuel ratio needs accurate control under steady conditions and needs the real time control under transient conditions. The state observer of air mass per cycle under steady conditions and the intake pressure observer and fuel compensator under transient conditions are designed after considering the characteristics of the engine sensors, which form the model based control strategy. According to the strategy, the revised Sage adaptive algorithm for the observer of air mass per cycle and the prediction algorithm for intake pressure observer are confirmed after analyzing the Kalman filter and simulating experiments.In order to validate the control strategy and algorithm, the design of control and calibration system is achieved for a 495 EFI gasoline engine. In addition, the...