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Presented in this paper is an on-line method for estimating the sulfation levels within a lean NOx trap (LNT). Sulfur poisoning plays a major role in the reduction of oxygen and NOx storage capacity in an LNT. Indicators of LNT degradation are LNT NOx absorption efficiency and capacity. The estimation of LNT oxygen and NOx storage capacity is an on-line method of monitoring LNT NOx absorption efficiency and capacity. The estimation provides information regarding the sulfation level of the LNT. This estimate may be used in conjunction with lean burn strategies to initiate an LNT sulfur purging mechanism and maintain maximum fuel economy. In addition, the estimation of LNT oxygen and NOx storage capacity may be used for on-board diagnostics, LNT NOx absorption efficiency estimation, NOx purge fuel estimation, and many other applications.

Presented in this paper is an on-line method for estimating the oxygen storage capacity contained within a catalyst. The oxygen storage capacity of a catalyst changes over time due to catalyst brick temperatures, poisoned catalyst sites, and thermal aging. Information regarding the current oxygen storage capacity of a catalyst is advantageous in the development of robust emission control strategies and on-board diagnostics. The method of collecting the oxygen storage capacity information is extremely important for measurement accuracy and repeatability. Furthermore, the information must be obtained in such a way that it is transparent to the operator and may be implemented on-line during normal drive cycles. This on-line method for estimation of oxygen storage capacity of a catalyst has been demonstrated on a Ford F150 platform with an underbody catalyst.