초록 ▼

An improved closed-loop feedback fuel control with a model-based A/F ratio estimator, wherein the estimator, controller and portions of the model are updated on a fixed time interval basis, thereby minimizing the impact of the control on event-based throughput. Engine transport delays and oxygen sen

An improved closed-loop feedback fuel control with a model-based A/F ratio estimator, wherein the estimator, controller and portions of the model are updated on a fixed time interval basis, thereby minimizing the impact of the control on event-based throughput. Engine transport delays and oxygen sensor dynamics are modeled to estimate the sensed A/F ratio, and the estimate is compared with the sensed A/F ratio to adaptively adjust the model and to develop a closed-loop adjustment of the commanded fuel amount. The engine transport delay model is carried out on an engine event basis, but the sensor dynamics model is carried out on a time basis to accurately reflect the analog nature of the sensor. The estimator and the controller are also carried out on a time basis to reduce throughput requirements at higher engine speeds, and the control gain is scheduled to account for differences between the engine event and time update rates. The control enables numerous control enhancements, including flexibility to topology variations (such as sensor placement, sensor type and sensor characteristics), ease of calibration, and the ability to easily calibrate and schedule A/F ratio perturbations for catalytic conversion efficiency optimization.

대표청구항 ▼

[ What is claimed is:] [1.]1. 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 es

[ What is claimed is:] [1.]1. 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 synchronismwith 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.