Method and system for contamination signature detection diagnostics of a particulate matter sensor
View Patent ↗A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate with electrical resistance that varies with temperature and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, R elect . The diagnosis is performed by heating the substrate in the area between the electrodes and using the resistance between the electrodes to determine detecting whether contamination is present on the surface of the sensor. Heat may be maintained on the sensor to attempt to burn off a detected contaminant, and a subsequent resistance reading may be used to determine if the contaminant was successfully burned off.
1. A method of diagnosing an operating condition of an electrically conductive particulate matter sensor, said sensor comprising a substrate having an electrical resistance that varies with temperature and two electrodes on said substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, R elect , said method comprising the steps of:
(a) commanding the provision of heat to the sensor in an amount sufficient to modify the electrical resistance of the substrate, and detecting whether R elect changes in a manner consistent with heating of a contaminant on the substrate;
(b) if R elect changes in a manner consistent with heating of a contaminant on the substrate in step (a), then diagnosing a contamination condition for the sensor;
wherein said sensor includes a heater element adapted to heat an area between said electrodes, and step (a) comprises the steps of:
(1) measuring R elect before activating the heater element and storing the value as R OBD — init ;
(2) activating the heater element for a first period of time; while periodically measuring R elect , and storing the value as R OBD —R hot ;
(3) comparing R OBD —R hot to a predetermined percentage K R —R OBD —R init ;
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct of R OBD —R init , then determining that R elect did not change in a manner consistent with heating a contaminated substrate; and
(5) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with heating a contaminated substrate.
2. A method of diagnosing an operating condition of an electrically conductive particulate matter sensor, said sensor comprising a substrate having an electrical resistance that varies with temperature and two electrodes on said substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, R elect , said method comprising the steps of:
(a) commanding the provision of heat to the sensor in an amount sufficient to modify the electrical resistance of the substrate, and detecting whether R elect changes in a manner consistent with heating of a contaminant on the substrate;
(b) if R elect changes in a manner consistent with heating of a contaminant on the substrate in step (a), then diagnosing a contamination condition for the sensor;
(c) if R elect changes in a manner consistent with heating of a contaminant on the substrate in step (a), then (i) maintaining the provision of heat for a predetermined time, (ii) determining after the lapse of the predetermined time whether R elect changes in a manner consistent with the contaminant being removed from the sensor, then (iii) if R elect changes in a manner consistent with the contaminant being removed from the sensor diagnosing that the contaminant was removed from the sensor, or if R elect does not change in a manner consistent with the contaminant being removed from the sensor diagnosing that the contaminant was not removed from the sensor.
3. The method according to claim 2 wherein said sensor includes a heater element adapted to heat an area between said electrodes, wherein step (a) comprises the steps of:
(1) measuring R elect before activating the heater element and storing the value as R OBD —R init ;
(2) activating the heater element for a first period of time; while periodically measuring R elect , and storing the value as R OBD —R hot ;
(3) comparing R OBD —R hot to a predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init ;
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init , then determining that R elect did not change in a manner consistent with heating a contaminated substrate; and
(5) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with heating a contaminated substrate;
and step (c) comprises the steps of:
(1) maintaining activation of the heater element for a second period of time; while periodically measuring R elect , and storing the value as R OBD —R hot ;
(2) comparing R OBD —R hot a predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init ;
(3) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init , then determining that R elect did not change in a manner consistent with a contaminant being removed from the substrate; and
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with a contaminant being removed from the substrate.
4. A diagnostic system for an electrically conductive particulate matter sensor comprising a substrate and two electrodes on said substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, R elect , said system comprising a microprocessor in communication with the sensor and a storage medium including instructions for causing the microprocessor to implement a method comprising the steps of:
(a) commanding the provision of heat to the sensor in an amount sufficient to modify the electrical resistance of the substrate, and detecting whether R elect , changes in a manner consistent with heating of a contaminant on the substrate;
(b) if R elect changes in a manner consistent with heating of a contaminant on the substrate in step (a), then diagnosing a contamination condition for the sensor;
wherein said sensor includes a heater element adapted to heat an area between said electrodes, and step (a) comprises the steps of:
(1) measuring R elect before activating the heater element and storing the value as R OBD —R init ;
(2) activating the heater element for a first period of time; while periodically measuring R elect , and storing the value as R OBD —R hot ;
(3) comparing R OBD —R hot to a predetermined percentage K R —R OBD —R cont —R pct of R OBD —R init ;
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct of R OBD —R init , then determining that R elect did not change in a manner consistent with heating a contaminated substrate; and
(5) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with heating a contaminated substrate.
5. A diagnostic system for an electrically conductive particulate matter sensor comprising a substrate and two electrodes on said substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, R elect , said system comprising a microprocessor in communication with the sensor and a storage medium including instructions for causing the microprocessor to implement a method comprising the steps of:
(a) commanding the provision of heat to the sensor in an amount sufficient to modify the electrical resistance of the substrate, and detecting whether R elect , changes in a manner consistent with heating of a contaminant on the substrate;
(b) if R elect changes in a manner consistent with heating of a contaminant on the substrate in step (a), then diagnosing a contamination condition for the sensor;
(c) if R elect , changes in a manner consistent with heating of a contaminant on the substrate in step (a), then (i) maintaining the provision of heat for a predetermined time, (ii) determining after the lapse of the predetermined time whether R elect , changes in a manner consistent with the contaminant being removed from the sensor, then (iii) if R elect changes in a manner consistent with the contaminant being removed from the sensor diagnosing that the contaminant was removed from the sensor , or if R elect does not change in a manner consistent with the contaminant being removed from the sensor diagnosing that the contaminant was not removed from the sensor.
6. The diagnostic system according to claim 5 wherein said sensor includes a heater element adapted to heat an area between said electrodes, wherein step (a) comprises the steps of:
(1) measuring R elect before activating the heater element and storing the value as R OBD —R init ;
(2) activating the heater element for a first period of time; while periodically measuring R elect , and storing the value as R OBD —R hot ;
(3) comparing R OBD —R hot to a predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init ;
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init , then determining that R elect did not change in a manner consistent with heating a contaminated substrate; and
(5) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct1 of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with heating a contaminated substrate;
and step (c) comprises the steps of:
(1) maintaining activation of the heater element for a second period of time while periodically measuring R elect , and storing the value as R OBD —R hot ;
(2) comparing R OBD —R hot a predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init ;
(3) if R OBD —R hot is less than the predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init , then determining that R elect did not change in a manner consistent with a contaminant being removed from the substrate; and
(4) if R OBD —R hot is not less than the predetermined percentage K R —R OBD —R cont —R pct2 of R OBD —R init as determined in step (3) during said first period of time, then determining that R elect changed in a manner consistent with a contaminant being removed from the substrate.