Study on Optimum Estimate Method for Gasoline Engine Intake Flowrate Based on State Observer

The accurate air-fuel ratio control of electronic fuel injection system is based on exact measurement of intake flowrate, which is the important measure of reducing exhaust emission and improving fuel economy. Taking the nonlinear character of intake system into account, an intake dynamic model is studied based on the mean value engine model, and the relation between manifold pressure and intake system parameters is given. According to the application trait of Kalman filter, an estimated method of engine intake flowrate is put forward based on extended Kalman filter (EKF). The iterative equation is obtained by simple linearization of nonlinear system. Intake pressures with different transient operation condition are computed. The study shows that the calculated value and the measurement value possess the characteristics of good tracing with little deviation. The predictive effect is satisfactory