Exhaust particulate filter system and methods

Abstract

A method of operating an exhaust particulate filter system for an internal combustion engine includes transmitting electromagnetic energy, for example having a frequency above about 2 GHz through an exhaust particulate filter containing trapped soot. The transmitted electromagnetic energy may be attenuated in response to the trapped soot, and a filter soot loading value calculated based at least in part upon a correlation among an attenuation of the electromagnetic energy, a temperature of the filter, and a mass of the trapped soot. An algorithm based upon a partial derivative of an equation representing the correlation may be used in calculating the filter soot loading value, and a resulting soot mass. Responsive to determining the calculated soot mass satisfies regeneration suitability conditions, a regeneration initiation command may be outputted.

1 . A method of detecting particulate matter in an exhaust filter for an internal combustion engine comprising the steps of:
 receiving data indicative of an attenuation of electromagnetic energy transmitted through the exhaust particulate filter and attenuated in response to trapped soot;   receiving data indicative of a temperature of the exhaust particulate filter;   calculating a filter soot loading value based at least in part upon a correlation among the attenuation, the temperature, and a mass of the trapped soot; and   electronically recording the filter soot loading value.   
     
     
         2 . The method of  claim 1  wherein the filter soot loading value is indicative of the mass of the trapped soot, a change in the mass of trapped soot, or a rate of change in the mass of trapped soot. 
     
     
         3 . The method of  claim 2  wherein the step of calculating further includes calculating the change in the mass of trapped soot in a time interval. 
     
     
         4 . The method of  claim 3  further comprising a step of determining the mass of the trapped soot at least in part by numerically integrating the change in the mass of trapped soot with changes in mass of trapped soot for a plurality of preceding time intervals. 
     
     
         5 . The method of  claim 3  further comprising a step of determining suitability of filter regeneration responsive to a ratio between the mass of the trapped soot and available filter volume, at least in part by comparing a value indicative of the ratio with a reference value. 
     
     
         6 . The method of  claim 3  wherein the correlation includes a correlation among the rate of change in mass, a rate of change in attenuation, and the temperature, in the time interval. 
     
     
         7 . The method of  claim 6  wherein the step of calculating further includes executing an algorithm based at least in part upon the equation: 
       
         
           
             
               S 
               = 
               
                 
                   A 
                   * 
                   
                     10 
                     
                       ( 
                       
                         
                           
                             - 
                             
                               soot 
                                
                               
                                 ( 
                                 g 
                                 ) 
                               
                             
                           
                           * 
                           
                             T 
                              
                             
                               ( 
                               K 
                               ) 
                             
                           
                         
                         B 
                       
                       ) 
                     
                   
                 
                 + 
                 C 
               
             
           
         
         where: 
         S=attenuation; 
         A=effective filter volume; and 
         B and C are constants. 
       
     
     
         8 . The method of  claim 7  wherein the algorithm is based at least in part upon a partial derivative of the equation varying attenuation with respect to soot mass but not with respect to temperature. 
     
     
         9 . The method of  claim 2  wherein the step of receiving data indicative of attenuation includes receiving a mean attenuation value for a collection of electromagnetic frequencies. 
     
     
         10 . The method of  claim 9  wherein the mean attenuation value includes a mean attenuation value for a collection of electromagnetic frequencies transmitted at a later time, and wherein the method further comprises a step of receiving a mean attenuation value for the collection of electromagnetic frequencies transmitted at an earlier time. 
     
     
         11 . The method of  claim 10  wherein the collection of electromagnetic frequencies includes a frequency band greater than about 2 GHz, and wherein the step of calculating further includes a step of calculating the change in mass of the trapped soot responsive to a difference between the mean attenuation values. 
     
     
         12 . An exhaust particulate filter system for an internal combustion engine comprising:
 an exhaust particulate filter having a filter housing, and a filter medium positioned between an exhaust inlet and an exhaust outlet of the filter housing; and   a control system for the exhaust particulate filter including a transmitter configured to transmit electromagnetic energy through the exhaust particulate filter, a receiver configured to receive transmitted electromagnetic energy, and a temperature sensor coupled with the exhaust particulate filter;   the control system further including a data processor coupled with the transmitter, the receiver, and the temperature sensor, the data processor being configured to calculate a filter soot loading value for the exhaust particulate filter based at least in part upon a correlation among an attenuation of transmitted electromagnetic energy, a temperature of the exhaust particulate filter, and a mass of trapped soot within the exhaust particulate filter.   
     
     
         13 . The exhaust particulate filter system of  claim 12  wherein the filter soot loading value is indicative of a change in the mass of trapped soot, and wherein the data processor is further configured to calculate a mass of the trapped soot responsive to the filter soot loading value. 
     
     
         14 . The exhaust particulate filter system of  claim 13  wherein the data processor is further configured to compensate the calculated filter soot loading value responsive to temperature. 
     
     
         15 . The exhaust particulate filter system of  claim 13  wherein the data processor is further configured to calculate the mass of the trapped soot from the calculated change in the mass of trapped soot via numerical integration. 
     
     
         16 . The exhaust particulate filter system of  claim 13  wherein the data processor is further configured to output a filter regeneration initiation command responsive to the calculated mass of trapped soot and responsive to an ash value indicative of a quantity of trapped ash within the exhaust particulate filter. 
     
     
         17 . The exhaust particulate filter system of  claim 12  wherein the correlation includes a non-linear correlation among a rate of change in the mass of trapped soot, a rate of change in the attenuation, and the temperature. 
     
     
         18 . The exhaust particulate filter system of  claim 17  wherein the transmitter is configured to transmit a band of electromagnetic frequencies greater than about 2 GHz, and wherein the data processor is further configured to determine the filter soot loading value responsive to a mean attenuation value for the band of electromagnetic frequencies. 
     
     
         19 . A method of operating an exhaust particulate filter system for an internal combustion engine comprising the steps of:
 receiving data indicative of a change in attenuation of electromagnetic energy transmitted through an exhaust particulate filter;   receiving data indicative of a temperature within the exhaust particulate filter;   determining a change in soot loading of the exhaust particulate filter responsive to the determined change in attenuation and the temperature; and   outputting a signal responsive to the determined change in soot loading.   
     
     
         20 . The method of  claim 19  wherein the step of determining further includes the steps of determining a value indicative of a change in a mass of trapped soot. 
     
     
         21 . The method of  claim 19  further comprising a step of compensating for temperature dependent variation in the attenuation, during the determining step.