# US 2015/0143884 A1 · Method and Apparatus for Estimating a Dosing-Error in a Selective Catalytic Reduction System > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0143884 A1 - Document ID: US20150143884A1 - Status: Published application - Kind: A1 - Application number: 14/403,090 - Filed: 2013-06-20 - Published: 2015-05-28 - Earliest claimed: 2012-06-20 - Assignees: Perkins Engines Company Limited - Applicants: Perkins Engines Company Limited - Inventors: David Heaton; Michail Soumelidis; Bastian Maass; Thomas Steffen - Web page: https://patentgrep.com/patent/US20150143884A1 ## CPC - F01N 3/2066: {Selective catalytic reduction [SCR]} - F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent} - F01N 11/007: {the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus} - G01M 15/102: {by monitoring exhaust gases} - F01N 2560/026: for measuring or detecting NOx - F01N 2610/02: the substance being ammonia or urea - F01N 2900/0411: using a feed-forward control - F01N 2900/0416: using the state of a sensor, e.g. of an exhaust gas sensor - F01N 2900/0601: being estimated - F01N 2900/1402: Exhaust gas composition - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - Y02C 20/10: of nitrous oxide (N2O) - Y02T 10/12: Improving ICE efficiencies - Y02T 10/40: Engine management systems - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE - Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG] - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method for determining if a selective catalytic reduction (SCR) device that is dosed with a reductant is being mis-dosed by considering an expected exhaust gas output state from the SCR device and measured exhaust gas output state, a NOx sensor sensitivity figure that is an indication of how sensitive the measured exhaust gas output state is to dosing errors and performing cross-correlation operations. ## Claims ### Claim 1 A method for determining if a selective catalytic reduction (SCR) device that is dosed with a reductant is being mis-dosed, the method comprising the steps of: determining a first cross-correlation figure by cross-correlating a measured exhaust gas output state with a NOx sensor sensitivity figure, wherein the NOx sensor sensitivity figure is an indication of how sensitive the measured exhaust gas output state is to dosing errors; determining a second cross-correlation figure by cross-correlating an expected exhaust gas output state from the SCR device with the NOx sensor sensitivity figure; and determining a mis-dosing indication figure which indicates if the SCR device is being under-dosed, correctly dosed or over-dosed from the difference between the first cross-correlation figure and the second cross-correlation figure. ### Claim 2 A method for determining if a selective catalytic reduction (SCR) device that is dosed with a reductant is being mis-dosed, the method comprising the steps of: determining a NOx readout difference figure from the difference between an expected exhaust gas output state from the SCR device and a measured exhaust gas output state from the SCR device; and determining a mis-dosing indication figure which indicates if the SCR device is being under-dosed, correctly dosed or over-dosed by cross-correlating the NOx readout difference with a NOx sensor sensitivity figure, wherein the NOx sensor sensitivity figure is an indication of how sensitive the measured exhaust gas output state is to dosing errors. ### Claim 3 (depends on 1) The method of claim 1, wherein a dosing error figure is determined by dividing the mis-dosing indication figure by an auto-correlation of the expected exhaust gas output state. ### Claim 4 (depends on 3) The method of claim 3, wherein the NOx sensor sensitivity figure is determined by differentiating the expected exhaust gas output state by the dosing error figure. ### Claim 5 (depends on 1) The method of claim 1, wherein the NOx sensor sensitivity figure is determined by dividing the difference between the expected exhaust gas output state and the measured exhaust gas output state by the difference between the expected exhaust gas output state and an estimated exhaust gas output state determined by a mis-dosing model which estimates the exhaust gas output state based upon a notional under-dosing or over-dosing condition. ### Claim 6 (depends on 1) The method of claim 1, wherein the NOx sensor sensitivity figure is determined by dividing the difference between the expected exhaust gas output state and the measured exhaust gas output state by the difference between an exhaust gas output state estimated by a notional over-dosing model and an exhaust gas output state estimated by a notional under-dosing model. ### Claim 7 (depends on 1) The method of claim 1, wherein the mis-dosing indication figure is determined a plurality of times over a period of time and the average of the plurality of mis-dosing indication figures is found. ### Claim 8 (depends on 7) The method of claim 7, wherein the plurality of mis-dosing indication figures is low-pass filtered in order to remove high-frequency noise. ### Claim 9 (depends on 1) The method of claim 1, wherein the expected exhaust gas output state from the SCR device is determined from at least one of a measured state of the exhaust gas input to the SCR device, the level of reductant dosing applied to the SCR device and an estimate, or measurement, of the catalyst temperature. ### Claim 10 (depends on 1) The method of claim 1, wherein the measured state of the exhaust gas input to the SCR device comprises at least one of the amount of NOx in the exhaust gas, the temperature of the exhaust gas and the mass flow rate of the exhaust gas. ### Claim 11 (depends on 1) A controller to determine if a selective catalytic reduction (SCR) device that is dosed with a reductant is being mis-dosed, the controller being configured to perform the method of claim 1. ### Claim 12 (depends on 2) A controller to determine if a selective catalytic reduction (SCR) device that is dosed with a reductant is being mis-dosed, the controller being configured to perform the method of claim 2. ### Claim 13 (depends on 11) An SCR system comprising: an SCR device that is dosed with a reductant, and the controller defined in claim 11, the controller being arranged to determine if the SCR device is being mis-dosed. ### Claim 14 (depends on 13) An internal combustion engine comprising the SCR system defined in claim 13. ### Claim 15 (depends on 14) A vehicle comprising the internal combustion engine defined in claim 14. ### Claim 16 (depends on 12) An SCR system comprising: an SCR device that is dosed with a reductant, and the controller defined in claim 12, the controller being arranged to determine if the SCR device is being mis-dosed. ### Claim 17 (depends on 2) The method of claim 2, wherein a dosing error figure is determined by dividing the mis-dosing indication figure by an auto-correlation of the expected exhaust gas output state. ### Claim 18 (depends on 17) The method of claim 17, wherein the NOx sensor sensitivity figure is determined by differentiating the expected exhaust gas output state by the dosing error figure. ### Claim 19 (depends on 2) The method of claim 2, wherein the NOx sensor sensitivity figure is determined by dividing the difference between the expected exhaust gas output state and the measured exhaust gas output state by the difference between the expected exhaust gas output state and an estimated exhaust gas output state determined by a mis-dosing model which estimates the exhaust gas output state based upon a notional under-dosing or over-dosing condition. ### Claim 20 (depends on 2) The method of claim 2, wherein the NOx sensor sensitivity figure is determined by dividing the difference between the expected exhaust gas output state and the measured exhaust gas output state by the difference between an exhaust gas output state estimated by a notional over-dosing model and an exhaust gas output state estimated by a notional under-dosing model.