Study of fuel film parameter identification in gasoline engine transient conditions based on weighted recursive instrumental variable method

It is very important for transient air-fuel ratio control to obtain the fuel film dynamic parameters precisely. The fuel film identification equation based on the inlet fuel film dynamic model is built under the consideration of random errors. In order to eliminate the effect of random errors on the fuel film parameter estimation, instrumental variable (IV) method is put forward. At the same time, considering that each set of measurement data have different confidence coefficient in terms of parameters estimation, the weighted term is introduced to the instrumental variable equation. An engine model is set up using EN-DYNA. Parameter identification applying the proposed algorithm, least squares and Markov recursive least squares are conducted respectively at 1500-3000r/min and the throttle opening from 10%-80%. The identification results are compared and analyzed with the calibration value. The results show that maximum deviation of X and τ applying the weighted recursive instrumental variable method are 1.58% and 4.5% respectively. However, the maximum deviation of X and τ are 2.37% and 6.18% in Markov recursive least squares method meanwhile the value are 4.08% and 9.16% in least squres method.