Patent ID: 6233922
Filing Date: 2001-05-22
Classification: F02D

Abstract:
A fuel control for an internal combustion engine including an open-loop air/fuel ratio command, a fuel pulse width command corresponding to said air/fuel ratio command, an oxygen sensor for measuring an exhaust gas air/fuel ratio, a periodically updated estimator for estimating an output of the oxygen sensor based on the commanded air/fuel ratio and characteristic parameters of the engine and oxygen sensor and generating a leading control error signal based on a difference between the estimated and actual outputs of the oxygen sensor, and a periodically updated controller responsive to the control error signal for developing a feedback signal for adjusting the commanded fuel pulse width so as to produce the commanded air/fuel ratio, the improvement wherein:the estimator includes an engine delay model periodically updated at a variable rate in synchronism with engine cooperation and responsive to the commanded air/fuel ratio for estimating an air/fuel ratio at the oxygen sensor, and a sensor model periodically updated at a fixed rate and responsive to the estimate of the engine delay model for estimating the output of the oxygen sensor; andthe feedback signal developed by the controller is adjusted to account for differences between said variable update rate and said fixed update rate.