Research On Transient Air-Fuel Ratio Control Of Engine Based On Model

For port fuel injection engines,high fuel economy and low emissions are largely dependent on the precise control of the air-fuel ratio(AFR).Aiming at the problem of fastly and accurately tracking of transient fuel-air ratio,a nonlinear control method of fuel-air ratio is proposed.Firstly,the engine mean value model is used to model the inlet air dynamic model,fuel dynamic model and engine output model,and the extended state observer is designed to compensate the modeling errors,and then the model with higher accuracy is obtained.The state feedback controller is designed under the framework of Lyapunov stability.Based on the model,the real-time prediction of the air volume into the cylinder compensates the execution delay of the oil circuit,and finally proves the robustness of the system.Taking an inlet jet engine developed on a school-enterprise cooperation project as the research object,the trial production of the engine has been initially completed,and the next step is to carry out the electronic control design of the engine.On the study of the requirements of increasingly stringent emission regulations,engine based on the actual situation in order to ensure the technical route of ternary catalyst conversion efficiency,with the method of numerical simulation technology combined with test,focuses on air-fuel ratio control problem,and refer to the actual test the concrete testing methods,to reduce the motorcycle exhaust emission targets.The main research contents are as follows:(1)Mainly introduces the construction process of the mean value engine model of the gasoline engine,including the sensors and actuators required for engine control,the air dynamic model of the intake manifold,the dynamic model of the oil film upstream of the intake valve,and the speed Torque model output and time lag model.Finally,the gasoline mean value engine model is calibrated using the test values collected by the bench to ensure that the error between the output value of MATLAB/Simulink simulation calculation and the test value obtained by the bench is within the engineering allowable range,in order to ensure the effectiveness of the control model practice used for engine air-fuel ratio control.(2)Firstly,the construction of the test bench for the four-stroke motorcycle engine,the specifications of the test equipment,the instrument parameters and the specifications of the sensors are described,and the engine fuel supply system is selected and tested for the response performance.According to the actual needs,the appropriate injector was selected.The volumetric efficiency of the whole working condition is calculated by the neural network on the part of the test working condition data.(3)According to the demand of air-fuel ratio control under transient conditions,a scheme for air-fuel ratio control is proposed.The feedforward compensation of the dynamic effect of the oil film is necessary for the quick response of the injector,and the oil film parameters are identified by the least square method.(4)Use the engine mean value model to model the intake air dynamic model,fuel dynamic model and engine output model,and design an expanded state observer to compensate the modeling error,and then obtain a model with higher accuracy;in Lyapunov stability,the state feedback controller is designed under the framework;based on the model,the real-time prediction of the air volume entering the cylinder compensates for the execution delay of the oil circuit,and finally proves the robustness of the system.The simulation results show that: the nonlinear fuel-air ratio control algorithm quickly track the expected value of air-fuel ratio;the steady-state time is 1.7s;the maximum error is within 4.5%;and it has good robustness under the disturbance of model mismatch and reduces.The influence of time delay and parameter uncertainty on the system is discussed.