Patent ID: 8701390

Claim:
A method of operation for a vehicle comprising an engine and an exhaust aftertreatment system, comprising: operating the engine through a series of ignition cycles to produce exhaust; treating the exhaust with a lean NOx trap (LNT) within the exhaust aftertreatment system; operating the exhaust aftertreatment system in deNOx cycles each comprising a lean phase in which NOx accumulates within the LNT and a deNOx operation comprising a rich phase in which accumulated NOx is reduced and released; operating the exhaust aftertreatment system in deSOx cycles each comprising a plurality of deNOx cycles over which SOx accumulates within the LNT and a deSOx operation in which accumulated SOx is reduced or released; measuring NOx concentration in the exhaust at a position downstream from the LNT over intervals corresponding to at least one entire deNOx cycle, or the greater part thereof; using the measurements to determine NOx treatment effectiveness data in which each data point characterizes NOx treatment effectiveness for a distinct interval and is determined from a plurality of the measurements made over the interval; sorting the data into categories according to operating conditions under which the data was collected, each category corresponding to a distinct range of operating conditions, there being at least four different categories; analyzing the NOx treatment effectiveness data on a category-by-category basis, the analysis comprising comparing the data to a target value or value range applicable to data in that category; adapting the numerical values of one or more parameters on the basis of the comparison, the parameters relating to one or more of the timing or conduct of deNOx or deSOx operations beyond the immediate future; accumulating the sorted data; and wherein the adaptations are contingent on a category having at least a minimum number of data points that have accumulated over at least a minimum period, the minimum number being at least three and the minimum period spanning at least one ignition cycle or one deSOx cycle.