Method of estimating the fuel/air ratio in a cylinder of an internal-combustion engine by means of an extended Kalman filter

A method of estimating a fuel/air ratio in cylinders of an internal combustion engine comprising a gas exhaust circuit including the cylinders being connected to a manifold and a detector measuring the fuel/air ratio downstream from the manifold, comprising:

• performing a modelling of a transfer function of the detector wherein an estimation of the fuel/air ratio measured by the detector is utilized;
• providing a physical model representing in real time expulsion of the gases from the cylinders and travel of the gases in the gas exhaust circuit up to the detector, wherein the modelling of the transfer function is utilized and includes a physical model of expulsion of the gases from the cylinders, a physical model of the manifold, a physical model of a flow rate passing through a turbine and a physical model of a lag time due to a transportation of gases from the cylinders to the detector;
• coupling the models with an extended Kalman type non-linear estimator;
• and
• performing a real-time estimation of the fuel/air ratio in the cylinders from the extended Kalman type non-linear estimator.