| 主权项 |
1. A method of controlling an air-fuel ratio (AFR) in an engine system, the engine system including a nitrogen oxide (NOx) sensor positioned downstream of a three-way catalyst with respect to a flow of an exhaust gas, the method comprising:
receiving a current NOx value of the exhaust gas from the NOx sensor; comparing the current NOx value with a first predetermined NOx target; selectively adjusting an AFR set-point from a lean AFR towards a rich AFR if the current NOx value is greater than the first predetermined NOx target, such that the AFR set-point is adjusted by a first predetermined value, wherein the first predetermined value varies according to a difference between the current NOx value and the first predetermined NOx target; and selectively controlling the AFR set-point by a second predetermined value if the current NOx value is lesser than the first predetermined NOx target, such that the second predetermined value is relatively smaller than the first predetermined value, wherein controlling the AFR set-point further includes:
determining a first average of NOx values of the exhaust gas over a first predetermined time;adjusting the AFR set-point by the second predetermined value;determining a second average of NO values of the exhaust gas over a second predetermined time;determining a delta NOx value, wherein the delta NOx value is a difference between the first average and the second average; andcomparing the delta NOx value with a second predetermined NOx target,wherein the AFR set-point is repeatedly controlled if the delta NOx value is greater than the second predetermined NOx target. |
