Method for determining load on particulate filter for engine exhaust, including estimation of ash content

A method of estimating the amount of inert material accumulated in a particulate filter for an internal combustion engine exhaust, comprising the steps of:

• (A) regenerating said filter by increasing the temperature of exhaust gas entering said filter to a level sufficient to incinerate combustible particulates trapped in said filter and representing a backpressure load;
• (B) detecting the end point of step (A);
• (C) after completing step (B), determining the remaining load in said particulate filter, said remaining load being related to the accumulated amount of said inert material in said filter;
• (D) successively repeating steps (A)-(C);
• and
• (E) determining the minimum amount of remaining load determined over the successively repeated steps.

A method of determining the load in a particulate filter for an internal combustion engine resulting from the accumulation of incombustible particulates in said filter over a preselected interval, wherein the total load in said filter includes both said incombustible and combustible particulates, comprising the steps of:

• (A) determining the value of the load in said filter at a first time point during said preselected interval;
• (B) storing the value determined in step (A) in a memory;
• (C) determining the value of said load in said filter at each of a plurality of time points during said subsequent to said first time point;
• (D) comparing the values determined in step (C) with the value stored in step (B);
• and
• (E) updating said memory based on the comparison performed in step (D) when the comparison performed in step (D) indicates that the value of the load determined at a subsequent time point is less than the previously stored load value, the value stored in said memory at the end of said interval representing said incombustible particulate load.