# US 2016/0258371 A1 · Methods and systems for estimating exhaust pressure with a variable voltage oxygen sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0258371 A1 - Document ID: US20160258371A1 - Status: Published application - Kind: A1 - Application number: 14/637,060 - Filed: 2015-03-03 - Published: 2016-09-08 - Earliest claimed: 2015-03-03 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Daniel A. Makled; Gopichandra Surnilla; Richard E. Soltis; Michael McQuillen - Web page: https://patentgrep.com/patent/US20160258371A1 ## CPC - F02D 41/145: {with determination means using an estimation} - F02D 21/08: the other gas being the exhaust gas of engine - F02D 41/0007: {for control of turbo-charged or super-charged engines (control of the pumps per se F02B37/12)} - F02D 41/0235: {in relation with the state of the exhaust gas treating apparatus (control of exhaust gas treating apparatus per se F01N)} - F02D 41/029: {the exhaust gas treating apparatus being a particulate filter} - F02D 41/1402: {Adaptive control} - F02D 41/1448: {the characteristics being an exhaust gas pressure} - F02D 41/1455: {with sensor resistivity varying with oxygen concentration (F02D41/1456 takes precedence)} - F02D 41/1456: {with sensor output signal being linear or quasi-linear with the concentration of oxygen} - F02D 41/26: using computer, e.g. microprocessor - F02D 41/3011: {according to or using specific or several modes of combustion} - F02M 26/47: the characteristics being temperatures, pressures or flow rates - G01M 15/104: {using oxygen or lambda-sensors (testing catalytic converters F01N3/18, F01N11/007)} - F02D 35/0015: {using exhaust gas sensors (F02D41/14 takes precedence)} - F02D 41/0025: {Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures} - F02D 41/123: {the fuel injection being cut-off} - F02D 41/3094: {the fuel injection being effected by at least two different injectors, e.g. one in the intake manifold and one in the cylinder} - F02D 2041/001: {for engines with variable valve actuation} - F02D 2041/1433: {using a model or simulation of the system} - F02D 2200/0404: Throttle position - F02D 2200/0406: Intake manifold pressure - F02D 2200/0414: Air temperature - F02D 2200/0418: Air humidity - F02D 2200/0612: determined by estimation - F02D 2200/0802: Temperature of the exhaust gas treatment apparatus - F02D 2200/1002: Output torque - F02D 2200/101: Engine speed - F02D 2200/501: Vehicle speed - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract Methods and systems are provided for estimating an engine exhaust pressure based on outputs from an exhaust oxygen sensor. In one example, a method may include estimating an exhaust pressure of exhaust gas flowing through an engine exhaust passage based on a difference between a first output of an oxygen sensor disposed in the exhaust passage and a second output of the oxygen sensor and then adjusting engine operation based on the estimated exhaust pressure. As one example, both the first and second outputs may be taken while operating the sensor in a variable voltage mode, after increasing a reference voltage of the oxygen sensor from a lower, first voltage to a higher, second voltage. ## Claims ### Claim 1 A method, comprising: adjusting engine operation based on an exhaust pressure of exhaust gas flowing through an engine exhaust passage estimated based on a difference between a first output of an oxygen sensor disposed in the engine exhaust passage and a second output of the oxygen sensor, both the first and second outputs taken after increasing a reference voltage of the oxygen sensor from a lower, first voltage to a higher, second voltage. ### Claim 2 (depends on 1) The method of claim 1, further comprising generating the second output during engine operation at a same air-fuel condition and at a same second voltage as during generating the first output. ### Claim 3 (depends on 2) The method of claim 2, further comprising generating the second output during engine fueling while air-fuel ratio control is enabled. ### Claim 4 (depends on 1) The method of claim 1, further comprising estimating a change in exhaust pressure based on a difference between the first and second outputs. ### Claim 5 (depends on 1) The method of claim 1, further comprising correcting each of the first and second outputs based on ambient humidity and estimating the exhaust pressure based on the corrected first and second outputs. ### Claim 6 (depends on 1) The method of claim 1, wherein the first and second outputs of the oxygen sensor are pumping currents output while the oxygen sensor is operating at the second voltage. ### Claim 7 (depends on 6) The method of claim 6, wherein estimating the exhaust pressure includes estimating the exhaust pressure based on a difference between the first and second outputs and a conversion factor, where the conversion factor converts a change in pumping current into an equivalent exhaust pressure. ### Claim 8 (depends on 1) The method of claim 1, wherein estimating the exhaust pressure is responsive to one or more of engine operation conditions being outside a window for modeling the exhaust pressure using an exhaust pressure model based on selected engine operating conditions and a request to confirm a modeled exhaust pressure determined with the exhaust pressure model. ### Claim 9 (depends on 1) The method of claim 1, further comprising estimating an air-fuel ratio based on the second output during the estimating the exhaust pressure, while operating the oxygen sensor at the second voltage. ### Claim 10 (depends on 1) The method of claim 1, wherein adjusting engine operation includes one or more of adjusting engine fueling, engine air charge, and engine boosting. ### Claim 11 (depends on 1) The method of claim 1, wherein the first voltage is a voltage at which water molecules are not dissociated at the oxygen sensor and the second voltage is a voltage at which water molecules are dissociated. ### Claim 12 (depends on 1) The method of claim 1, wherein the oxygen sensor is disposed in the engine exhaust passage upstream of a catalyst. ### Claim 13 A method, comprising: during engine fueling conditions: generating a first output of an oxygen sensor operating at a target reference voltage where water molecules are dissociated when an air-fuel ratio is at a first level, the oxygen sensor disposed in an engine exhaust passage; subsequently generating a second output of the oxygen sensor operating at the target reference voltage when the air-fuel ratio is at the first level; and estimating an exhaust pressure of exhaust gas flowing though the engine exhaust passage based on a difference between the first output and the second output. ### Claim 14 (depends on 12) The method of claim 12, wherein generating the first output includes generating a first pumping current output with the oxygen sensor at the target reference voltage at a known exhaust pressure. ### Claim 15 (depends on 13) The method of claim 13, wherein the second output of the oxygen sensor is a second pumping current output by the oxygen sensor at the target reference voltage and wherein estimating the exhaust pressure includes estimating the exhaust pressure based on a change in exhaust pressure between a time of generating the first output and the second output and the known exhaust pressure, where the change in exhaust pressure is based on the difference between the first output and the second output. ### Claim 16 (depends on 12) The method of claim 12, further comprising adjusting the first output and the second output based on ambient humidity and estimating the exhaust pressure based on a difference between the adjusted first output and the adjusted second output. ### Claim 17 (depends on 16) The method of claim 16, further comprising estimating the ambient humidity based on a change in pumping current output by the oxygen sensor while continuously modulating a reference voltage of the oxygen sensor between a lower, first voltage and a higher, second voltage while fuel is not being injected into cylinders of an engine including the engine exhaust passage. ### Claim 18 (depends on 12) The method of claim 12, further comprising adjusting engine operation based on the estimated exhaust pressure, where adjusting engine operation includes one or more of adjusting engine fueling, engine air charge, engine boosting, and regeneration of a particulate filter. ### Claim 19 A system for an engine, comprising: an exhaust oxygen sensor disposed in an exhaust passage of the engine upstream of a catalyst; and a controller with computer readable instructions for: adjusting engine operation based on an exhaust pressure of exhaust gas flowing through the exhaust passage, where the exhaust pressure is estimated based on a first output of the exhaust oxygen sensor while operating the exhaust oxygen sensor in a variable voltage mode where a reference voltage of the sensor is at a target voltage where water molecules are dissociated and while operating the engine at a first air-fuel ratio and a second output of the exhaust oxygen sensor obtained a duration after the first output, while operating the exhaust oxygen sensor at the target voltage and while operating the engine at the first air-fuel ratio. ### Claim 20 (depends on 19) The system of claim 19, wherein the duration is based on a time between generating the first output and a request received by the controller to estimate the exhaust pressure, where the request is responsive to one or more of the exhaust oxygen sensor operating at the target voltage, the engine operating outside an update window for an exhaust pressure model based on alternate engine operating parameters, and a request to confirm a modeled exhaust pressure determined from the exhaust pressure model.