Patent ID: 6314952
Filing Date: 2001-11-13
Classification: F02D

Abstract:
A control method for fueling N individual cylinders of a multi-cylinder internal combustion engine based on an output signal of an oxygen sensor positioned to respond to a combination of exhaust gases generated in the individual cylinders, the control method comprising the steps of:sampling the oxygen sensor output signal sampling events that occur in synchronism with firing events in each of the individual cylinders;filtering the oxygen sensor signal samples to define a nominal air/fuel ratio trajectory;utilizing an observer model to define N state variables estimating air/fuel imbalances in each of the N different cylinders, and an additional state variable estimating a deviation of the sensed A/F ratio from said nominal air/fuel ratio trajectory;measuring a deviation of the sensed air/fuel ratio from the nominal air/fuel ratio trajectory at each sampling event, and updating all of the state variables based on a difference between such measured deviation and the estimated deviation given by said additional state variable;retrieving a previously stored index that associates the N state variables with corresponding individual cylinders;fueling the individual cylinders based on the associated observer state variables using a closed-loop feedback control;computing a control performance measure based on a sum of the indicated air/fuel ratio imbalances; andif the performance measure indicates unstable air/fuel ratio control, identifying a new index value associating the N state variables with the individual cylinders, and storing the new index value in place of the retrieved index.