Methods and system for ash detection in exhaust particulate filter

An exhaust particulate filter system for an internal combustion engine comprising:

• an exhaust particulate filter including a filter medium positioned fluidly between an exhaust inlet and an exhaust outlet in a filter housing, and being configured to trap soot and ash in exhaust from an internal combustion engine;
• a monitoring system including a transmitter for transmitting electromagnetic energy through the exhaust particulate filter, and a receiver for sensing a strength of the transmitted electromagnetic energy;
• the monitoring system further including a computer readable memory configured to store a filter monitoring history which includes data indicative of a difference between transmitted strength of the electromagnetic energy and sensed strength;
• the monitoring system further including a microprocessor coupled with the computer readable memory and being configured to determine a value indicative of an amount of ash contained within the exhaust particulate filter responsive to a pattern of electromagnetic energy attenuation defined by the stored filter monitoring history, and the pattern varying from a greater attenuation relative to soot amount at an earlier time where the exhaust particulate filter is in a lower soot loading state, to a lesser attenuation relative to soot amount at a later time where the exhaust particulate filter is in a higher soot loading state.

A method of operating an exhaust particulate filter system comprising the steps of:

• transmitting electromagnetic energy through an exhaust particulate filter containing soot and ash;
• sensing a strength of the transmitted electromagnetic energy after having been attenuated in response to the soot;
• electronically storing data indicative of a difference between the transmitted strength and the sensed strength on a computer readable memory, such that a filter monitoring history stored on the computer readable memory defines a pattern of electromagnetic energy attenuation over time;
• and
• detecting an amount of the ash contained within the exhaust particulate filter via a microprocessor, responsive to the pattern;
• and
• electronically storing filter temperature data coincident in time with the pattern of electromagnetic energy attenuation;
• wherein:
• the step of transmitting further includes transmitting a plurality of electromagnetic frequencies;
• the step of sensing further includes sensing a strength of each of the plurality of electromagnetic frequencies;
• and
• the method further comprises a step of calculating a mean value based upon a difference between transmitted strength and sensed strength at each of the plurality of electromagnetic frequencies.