Gain/amplitude diagnostics of NOx sensors
First Claim
1. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
- (a) sensing that an exhaust gas recirculating (EGR) valve is closed and that fuel flow to a vehicle engine is above a predetermined rate using an electronic control unit (ECU) located on a vehicle and programmed to carry out the method steps;
(b) recording the output received from an NOx sensor relative to an amount of fuel consumption in response to step (a) over a period of time using the ECU;
(c) calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time using the ECU;
(d) repeating steps (a) and (b) at least once;
(e) performing a least-squares estimation (LSE) using the ECU for more than one calculated mean based on an expected NOx sensor output;
(f) generating a NOx sensor gain for the NOx sensor using the ECU based on the LSE; and
(g) determining whether the NOx sensor gain is above or below predetermined a threshold.
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Abstract
A method of diagnosing vehicle NOx sensor faults that includes sensing that an exhaust gas recirculating (EGR) valve is closed and that fuel flow to a vehicle engine is above a predetermined rate using an electronic control unit (ECU) located on a vehicle; recording the output received from an NOx sensor relative to an amount of fuel consumption over a period of time using the ECU; calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time using the ECU; performing a least-squares estimation (LSE) using the ECU for more than one calculated mean based on an expected NOx sensor output; generating a NOx sensor gain for the NOx sensor using the ECU based on the LSE; and determining whether the NOx sensor gain is above or below a predetermined threshold.
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Citations
18 Claims
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1. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
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(a) sensing that an exhaust gas recirculating (EGR) valve is closed and that fuel flow to a vehicle engine is above a predetermined rate using an electronic control unit (ECU) located on a vehicle and programmed to carry out the method steps; (b) recording the output received from an NOx sensor relative to an amount of fuel consumption in response to step (a) over a period of time using the ECU; (c) calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time using the ECU; (d) repeating steps (a) and (b) at least once; (e) performing a least-squares estimation (LSE) using the ECU for more than one calculated mean based on an expected NOx sensor output; (f) generating a NOx sensor gain for the NOx sensor using the ECU based on the LSE; and (g) determining whether the NOx sensor gain is above or below predetermined a threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
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(a) determining that an exhaust gas recirculating (EGR) valve is closed and that fuel flow on the vehicle is above a predetermined rate using an electronic control unit (ECU) located on a vehicle and programmed to carry out the method steps; (b) recording output from a NOx sensor using the ECU when the EGR valve is closed and the fuel flow is above the predetermined rate; (c) calculating the mean of the recorded output using the ECU; (d) repeating step (b) and step (c) more than once to generate a plurality of means; (e) performing a least squares estimate (LSE) on the plurality of means using the ECU based on expected NOx output data values included in a lookup table; (f) comparing the output of the LSE with a maximum gain or a minimum gain for a healthy NOx sensor using the ECU; and (g) determining if the output of the LSE is greater than or less than the data values included in the lookup table using the ECU. - View Dependent Claims (12, 13, 14, 15)
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16. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
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(a) determining that an exhaust gas recirculating (EGR) valve is closed and that the fuel flow to a vehicle engine is above a predetermined threshold using an electronic control unit (ECU) located on a vehicle and programmed to carry out the method steps; (b) recording the output from an NOx sensor over a predetermined amount period of time while the EGR valve is closed and fuel flow is above the predetermined threshold using the ECU; (c) calculating the mean value of the recorded output using the ECU; (d) performing step (b) and step (c) a plurality of times thereby generating a plurality of mean values; (e) calculating a least squares estimate (LSE) of the plurality of mean values with respect to expected output from a healthy NOx sensor using the ECU; (f) detecting an offset between the actual output from the NOx sensor and the expected output based on the calculated LSE using the ECU; and (g) monitoring output from the NOx sensor to determine if the output rises above the high-gain threshold or falls below the low gain threshold. - View Dependent Claims (17, 18)
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Specification