System and method for adjusting an exhaust gas recirculation valve based on multiple sensor outputs

Abstract

Method for an engine, comprising: Adjusting engine operation based on a final estimate of the gas flow parameters, wherein the final estimate of the gas flow parameters is based on a first gas flow parameter estimated with a first sensor, a second gas flow parameter estimated with a second sensor positioned in a gas channel of the engine at a distance from the first sensor, and accuracy values ​​of both the first and the second gas flow parameters, wherein the final estimate of the gas flow parameters is a final estimate of the exhaust gas recirculation (EGR) flow, and wherein adjusting the engine operation comprises adjusting an EGR valve (121) based on the final EGR flow estimate, and wherein the final EGR flow estimate is based on a first EGR flow estimated with a differential pressure sensor (125) across the EGR valve (121),a second EGR flow estimated with an intake oxygen sensor (168) and accuracy values ​​of both the first and second EGR flows.,

Description

Area

[0001] This description generally relates to methods and systems for an exhaust gas recirculation system of an internal combustion engine. Background / Summary

[0002] Engine systems may utilize the recirculation of exhaust gas from an engine exhaust system to an engine intake system (port), a process known as exhaust gas recirculation (EGR), to reduce regulated emissions and improve fuel economy. An EGR system, such as a low-pressure EGR system, may include various sensors for measuring and / or controlling EGR. As an example, an engine intake system may include an intake gas constituent sensor, such as an oxygen sensor, that may be used under non-EGR conditions to determine the oxygen content of fresh intake air. Under EGR conditions, the sensor may be used to divert EGR based on a change in oxygen concentration due to the addition of EGR as a diluent. An example of such an intake oxygen sensor is shown by Matsubara et al. in US Pat. No. 6,742,379 B2.

[0003] The accuracy of EGR estimates using the intake oxygen sensor may be reduced under certain engine operating conditions (for example, when the engine is boosted or when purge is activated and hydrocarbons are flowing through the intake system).

[0004] To increase the accuracy of the EGR flow estimation, it can be calculated in different ways, as described in US 2009 / 0 000 367 A1.

[0005] US 2013 / 0 061 831 A1 uses differential pressure sensors to combine a first determined EGR flow and a second determined EGR flow with a weighting factor to obtain a final EGR flow estimate. EGR flow can be estimated using alternative EGR sensors. For example, the EGR system can also include a differential pressure (DP) sensor positioned around an EGR valve to estimate EGR flow based on a pressure differential across the EGR valve and a flow area of ​​the EGR valve. EGR flow estimates can then be used to adjust a position of the EGR valve and therefore adjust an amount of EGR supplied to the engine. Thus, both the IAO2 sensor and the DP sensor can be used to provide independent EGR flow estimates. DE 10 2015 016 095 A1 provides methods and systems for diagnosing an oxygen sensor.The EGR flow is estimated using an intake oxygen sensor, although it is known that this estimate may be inaccurate and an alternative estimate of the EGR flow using a differential pressure sensor across the EGR valve may be more accurate.

[0006] However, the present inventors have recognized that the accuracies of the IAO2 and DP sensors may each change depending on engine operating conditions, thereby altering the accuracies of the resulting EGR flow estimates. Thus, the DP sensor may be more accurate than the IAO2 sensor under certain engine operating conditions, and vice versa. For example, the DP sensor may be more accurate than the IAO2 sensor when purge and / or PCV (Positive Crankcase Ventilation) gases are flowing through the intake system.

[0007] A method having the features of claims 1 and 11 and a system having the features of claim 17 are provided.

[0008] In one example, the problems described above may be addressed by a method for adjusting engine operation based on a final estimate of the gas flow parameters, wherein the final estimate of the gas flow parameters is based on a first gas flow parameter estimated with a first sensor, a second gas flow parameter estimated with a second sensor positioned in a gas passage of the engine away from the first sensor, and accuracy values ​​of both the first and second gas flow parameters. In this way, the final estimate of the gas flow parameters may have increased accuracy, thereby improving engine control.

[0009] As an example, the final estimate of the gas flow parameters may be a final estimate of the exhaust gas recirculation flow (final EGR flow estimate). For example, an engine may include an EGR passage that directs EGR from an exhaust passage to an intake passage of the engine via an EGR valve. An engine controller may estimate a first EGR flow based on a pressure differential across the EGR valve and a flow area of ​​the EGR valve. The engine controller may also estimate a second EGR flow based on an output of an intake oxygen sensor positioned in the intake passage downstream of the EGR passage. Furthermore, based on engine operating conditions during the estimation, the engine controller may assign a first accuracy value to the first EGR flow estimate and a second accuracy value to the second EGR flow estimate.For example, the first accuracy value may be based on compressor surge and / or a position of a compressor bypass valve and / or a differential pressure output by the differential pressure sensor, and the second accuracy value may be based on an intake oxygen sensor status and / or purge flow and / or PCV (Positive Crankcase Ventilation) flow. A final EGR flow estimate may then be determined based on the first EGR flow estimate, the second EGR flow estimate, the first accuracy value, and the second accuracy value. For example, the final EGR flow estimate may be based more heavily on one or the first or second EGR flow estimate based on the first and second accuracy values ​​with respect to each other. In this way, a more accurate EGR flow estimate may be determined.The engine control system can then adjust the EGR valve based on the final EGR flow estimate to deliver the requested EGR flow.

[0010] It should be understood that the above summary is intended to introduce, in a simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that resolve any of the disadvantages noted above or elsewhere in this disclosure. Short description of the drawings Fig. 1 is a schematic diagram of an example engine system including an intake oxygen sensor and an exhaust gas recirculation system. Fig. 2A-2B are flow diagrams of a method for determining a gas flow parameter of gases in an engine gas passage based on outputs from two sensors positioned at different locations of an engine. Fig. 3 is a flowchart of a method for determining the accuracy of outputs of a differential pressure sensor used to estimate an EGR fraction of intake air. Fig. 4 is a flowchart of a method for determining the accuracy of the outputs of an oxygen sensor used to estimate an EGR fraction in the intake air. Fig. Figure 5 is a block diagram for determining how to use outputs of an oxygen sensor and differential pressure sensor to estimate an EGR portion of intake air based on the accuracy of the sensors. Detailed description

[0011] The following description relates to systems and methods for determining a gas flow parameter of a gas flow in an engine of a vehicle based on estimates of the gas flow parameter from outputs of two sensors positioned at different locations in the engine system. As an example, the gas flow parameter may include a portion of exhaust gas recirculation (EGR) in the intake system of a turbocharged engine. A turbocharged engine, as described in Fig. 1, may include an intake oxygen sensor positioned in an intake passage of the engine and a differential pressure (DP) sensor positioned in an EGR passage. The DP sensor and the intake oxygen sensor may each be used to provide estimates of EGR flow through a low-pressure EGR system. The EGR flow may be regulated by an EGR valve, which, when open, may allow the recirculation of exhaust gas to an intake passage from downstream of a turbine to upstream of a compressor. However, the accuracy of the DP and oxygen sensors may change depending on engine operating conditions. As an example, the accuracy of the oxygen sensor may be lower than that of the DP sensor when purge and / or PCV gases are flowing through the intake system.On the other hand, the DP sensor may be less accurate than the oxygen sensor when compressor surge is active or a compressor bypass valve (CBV) is open. Thus, the accuracy of EGR flow estimates can be increased by a method for determining the accuracy of the sensors and incorporating measurements from both sensors into a final EGR flow estimate. Methods for determining the accuracy of EGR estimates by the DP and oxygen sensors are described in the . Fig. 3 and Fig. 4.

[0012] As in the Fig. As described in Figures 2-4, the accuracy of each of the sensors can be determined based on the engine operating conditions. Specifically, the accuracy of the sensors can be based on the presence of "pressure-side" purge and / or PCV gases in the intake system, pressure drop across the EGR valve, the presence of compressor surges, the position of a CBV valve, etc. Based on the accuracy of each of the sensors, a final EGR flow estimate can be obtained, as shown in Fig. 2. Furthermore, Fig. Figure 5 describes a method for incorporating oxygen and DP sensor outputs into an EGR flow estimate as a function of changes in sensor accuracy. By incorporating both oxygen and DP sensor outputs, the accuracy of the EGR flow estimate can be increased under a wide range of engine operating conditions.

[0013] Fig. 1 shows a schematic representation of an exemplary turbocharged engine system 100 including a multi-cylinder internal combustion engine 10 and dual turbochargers 120 and 130, which may be identical. As a non-limiting example, the engine system 100 may be included as part of a propulsion system for a passenger vehicle. Although not illustrated here, other engine configurations, such as a single-turbocharged engine, may be used without departing from the scope of the present disclosure.

[0014] The engine system 100 may be controlled at least in part by a controller 12 and by input from a vehicle operator 190 via an input device 192. In this example, the input device 192 includes an accelerator pedal and a pedal position sensor 194 for generating a proportional pedal position signal PP. The controller 12 may be a microcomputer including a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values ​​(e.g., a read-only memory chip), random access memory, maintain memory, and a data bus. The read-only memory storage medium may be programmed with computer-readable data representing non-transitory instructions executable by the microprocessor to perform the routines described herein, as well as other variations that are expected but not specifically recited.The controller 12 may be configured to receive information from a plurality of sensors 165 and send control signals to a plurality of actuators 175 (examples of which are described herein). Other actuators, such as various additional valves and throttles, may be coupled to various locations in the engine system 100. The controller 12 may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein according to one or more routines. Example control routines are described herein with reference to FIG. Fig. 2-4 described.

[0015] The engine system 100 may receive intake air via the intake passage 140. As in Fig. 1, the intake duct 140 may include an air filter 156 and an air induction system (AIS) throttle 115. The position of the AIS throttle 115 may be adjusted by the control system via a throttle actuator 117 communicatively coupled to the controller 12.

[0016] At least a portion of the intake air may be directed to a compressor 122 of the turbocharger 120 via a first branch of the intake passage 140, shown at 142, and at least a portion of the intake air may be directed to a compressor 132 of the turbocharger 130 via a second branch of the intake passage 140, shown at 144. Accordingly, the engine system 100 includes a low-pressure AIS (LP-AIS) system 191 upstream of the compressors 122 and 132 and a high-pressure AIS (HP-AIS) system 193 downstream of the compressors 122 and 132.

[0017] A positive crankcase ventilation (PCV) line 198 (e.g., a pressure-side pipe) may couple a crankcase (not shown) to the second intake passage branch 144 so that gases in the crankcase may be vented from the crankcase in a controlled manner. Furthermore, evaporative emissions from a fuel vapor canister (not shown) may be vented into the intake passage through a fuel vapor purge line 195 that couples the fuel vapor canister to the second intake passage branch 144.

[0018] The first portion of the total intake air may be compressed by compressor 122, from where it may be supplied to intake manifold 160 via intake duct 146. Thus, intake ducts 142 and 146 form a first branch of the engine's air intake system. Similarly, a second portion of the total intake air may be compressed by compressor 132, from where it may be supplied to intake manifold 160 via intake duct 148. Thus, intake ducts 144 and 148 form a second branch of the engine's air intake system. As shown in Fig. 1, intake air from intake passages 146 and 148 may be recombined via a common intake passage 149 before reaching intake manifold 160, from where the intake air may be delivered to the engine. In some examples, intake manifold 160 may include an intake manifold pressure sensor 182 for estimating a manifold air pressure (MAP) and / or an intake manifold temperature sensor 183 for estimating a manifold air temperature (MCT), each in communication with controller 12. In the depicted example, intake passage 149 further includes a charge air cooler (CAC) 154 and a throttle valve 158. The position of throttle valve 158 may be adjusted by the control system via a throttle actuator 157 communicatively coupled to controller 12.As shown, the throttle valve 158 may be disposed in the intake passage 149 downstream of the CAC 154 and configured to adjust the flow of an intake gas stream entering the engine 10.

[0019] As in Fig. 1, a compressor bypass valve (CBV) 152 may be disposed in a CBV (compressor bypass valve) passage 150, and a CBV 155 may be disposed in a CBV passage 151. In one example, the CBVs 152 and 155 may be electronic pneumatic CBVs (EPCBV). The CBVs 152 and 155 may be controlled to provide intake system depressurization when the engine is boosted. An upstream end of the CBV passage 150 may be coupled to the intake passage 148 downstream of the compressor 132, and a downstream end of the CBV passage 150 may be coupled to the intake passage 144 upstream of the compressor 132. Similarly, an upstream end of a CBV passage 151 may be coupled to the inlet passage 146 downstream of the compressor 122, and a downstream end of the CBV passage 151 may be coupled to the inlet passage 142 upstream of the compressor 122.Depending on a position of each CBV, the air compressed by the corresponding compressor may be recirculated to the intake port upstream of the compressor (e.g., intake port 144 for compressor 132 and intake port 142 for compressor 122). For example, CBV 152 may open to recirculate compressed air upstream of compressor 132, and / or CBV 155 may open to recirculate compressed air upstream of compressor 122 to relieve pressure in the intake system during selected conditions, thus reducing the effects of compressor surge loading. CBVs 155 and 152 may be controlled either actively or passively by the control system.

[0020] As shown, a compressor inlet pressure (CIP) sensor 196 is disposed in intake passage 142, and an HP AIS pressure sensor 169 is disposed in intake passage 149. However, in other possible embodiments, sensors 196 and 169 may be disposed at other locations within the LP AIS and HP AIS, respectively. Among other functions, CIP sensor 196 may be used to determine a pressure downstream of an EGR valve 121.

[0021] The engine 10 may include a plurality of cylinders 14. In the example shown, the engine 10 includes six cylinders arranged in a V configuration. More specifically, the six cylinders are arranged on two banks 13 and 15, with each bank containing three cylinders. In other examples, the engine 10 may include two or more cylinders, such as 3, 4, 5, 8, 10, or more cylinders. These various cylinders may be evenly split and arranged in other configurations, such as a V, inline, or horizontally opposed configuration, etc. Each cylinder 14 may be configured with a fuel injector 166. In the example shown, the fuel injector 166 is a direct-in-cylinder fuel injector. However, in other examples, the fuel injector 166 may also be configured as a port fuel injector.

[0022] Intake air supplied to each cylinder 14 (also referred to herein as combustion chamber 14) via a common intake port 149 may be used for fuel combustion, and combustion products may then be exhausted via bank-specific exhaust ports. In the example shown, a first bank 13 of cylinders of engine 10 may exhaust combustion products via a common exhaust port 17, and a second bank 15 of cylinders may exhaust combustion products via a common exhaust port 19.

[0023] The position of the intake and exhaust valves of each cylinder 14 may be controlled via hydraulically actuated lifters coupled to valve pushrods or via mechanical cup systems utilizing cam lobes. In this example, at least the intake valves of each cylinder 14 may be controlled by cam actuation using a cam actuation system. In particular, the intake valve cam actuation system 25 may include one or more cams and may utilize variable cam timing or variable cam lift for intake and / or exhaust valves. In alternative embodiments, the intake valves may be controlled by electric valve actuation. Likewise, the exhaust valves may be controlled by cam actuation systems or electric valve actuation. In yet another alternative embodiment, the cams may be non-adjustable.

[0024] Combustion products expelled by the engine 10 via the exhaust passage 17 may be directed through the exhaust turbine 124 of the turbocharger 120, which in turn may provide mechanical work to the compressor 122 via the shaft 126 to cause compression of the intake air. Alternatively, some or all of the exhaust gas flowing through the exhaust passage 17 may bypass the turbine 124 via the turbine bypass passage 123, as controlled by the wastegate 128. The position of the wastegate 128 may be controlled by an actuator (not shown) as commanded by the controller 12. As a non-limiting example, the controller 12 may adjust the position of the wastegate 128 via a pneumatic actuator controlled by a solenoid valve.For example, the solenoid valve may receive a signal to enable actuation of the wastegate 128 via the pneumatic actuator based on the difference in air pressures between the inlet passage 142 located upstream of the compressor 122 and the inlet passage 149 located downstream of the compressor 122. In other examples, other suitable approaches other than a solenoid valve may be used to actuate the wastegate 128.

[0025] Likewise, combustion products expelled by the engine 10 via the exhaust passage 19 may be directed through the exhaust turbine 134 of the turbocharger 130, which in turn may provide mechanical work to the compressor 132 via the shaft 136 to provide compression of the intake air flowing through the second branch of the engine intake system. Alternatively, some or all of the exhaust gas flowing through the exhaust passage 19 may bypass the turbine 134 via the turbine bypass passage 133, as controlled by the wastegate 138. The position of the wastegate 138 may be controlled by an actuator (not shown) as commanded by the controller 12. As a non-limiting example, the controller 12 may adjust the position of the wastegate 138 via a solenoid valve controlling a pneumatic actuator.For example, the solenoid valve may receive a signal to enable actuation of the wastegate 138 via the pneumatic actuator based on the difference in air pressures between the inlet passage 144 located upstream of the compressor 132 and the inlet passage 149 located downstream of the compressor 132. In other examples, other suitable approaches other than a solenoid valve may be used to actuate the wastegate 138.

[0026] In some examples, exhaust turbines 124 and 134 may be configured as variable geometry turbines, where controller 12 may adjust the position of the turbine impeller blades (or vanes) to vary the energy level received from the exhaust flow and applied to their respective compressor. Alternatively, exhaust turbines 124 and 134 may be configured as variable nozzle turbines, where controller 12 may adjust the position of the turbine nozzle to vary the energy level received from the exhaust flow and applied to their respective compressor. For example, the control system may be configured to independently vary the vane or nozzle position of exhaust turbines 124 and 134 via respective actuators.

[0027] Combustion products expelled by the cylinders via exhaust port 19 may be directed to the atmosphere via exhaust port 180 downstream of turbine 134, while combustion products expelled via exhaust port 17 may be directed to the atmosphere via exhaust port 170 downstream of turbine 124. Exhaust ports 170 and 180 may include one or more exhaust aftertreatment devices, such as a catalyst and one or more exhaust gas sensors. For example, exhaust port 170, as shown in Fig. 1, an exhaust gas purification device 129 arranged downstream of the turbine 124, and the exhaust passage 180 may include an exhaust gas purification device 127 arranged downstream of the turbine 134. The exhaust gas purification devices 127 and 129 may include SCR devices (Selective Catalytic Reduction), three-way catalysts (TWC), NO xTraps, various other emission control devices, or combinations thereof. Furthermore, in some embodiments, emission control devices 127 and 129 may be periodically regenerated during operation of engine 10, for example, by operating at least one cylinder of the engine at a particular air / fuel ratio.

[0028] Further, engine system 100 may include one or more exhaust gas recirculation (EGR) systems for recirculating at least a portion of the exhaust gas from the exhaust manifold to the intake manifold. These may include one or more high-pressure EGR systems for providing high-pressure EGR (HP EGR) and one or more low-pressure EGR circuits for providing low-pressure EGR (LP EGR). In one example, HP EGR may be provided in the absence of boost provided by turbochargers 120, 130, while LP EGR may be provided in the presence of turbocharger boost and / or when the exhaust gas temperature is above a threshold. In still other examples, both HP EGR and LP EGR may be provided simultaneously.

[0029] In the illustrated example, engine system 100 may include a low-pressure (LP) EGR system 108. LP EGR system 108 directs a desired portion of the exhaust gas from exhaust passage 170 to intake passage 142. In the illustrated embodiment, EGR in an EGR passage 197 is directed from downstream of turbine 124 to intake passage 142 at a mixing point located upstream of compressor 122. The amount of EGR supplied to intake passage 142 may be varied by controller 12 via EGR valve 121 coupled to LP EGR system 108. In the illustrated embodiment, Fig. In the exemplary embodiment shown in FIG. 1, the LP-EGR system 108 includes an EGR cooler 113 positioned upstream of the EGR valve 121. The EGR cooler 113 may transfer heat from the recirculated exhaust gas to, for example, an engine coolant. The LP-EGR system may include a Differential Pressure Over Valve (DPOV) (or DP) sensor 125. In one example, EGR flow may be estimated based on the DPOV system including the DP sensor 125 detecting a pressure differential between an upstream region of the EGR valve 121 and a downstream region of the EGR valve 121. The EGR flow determined by the DPOV system (e.g., LP EGR flow) may be further based on an EGR temperature detected by an EGR temperature sensor 135 located downstream of the EGR valve 121 and an EGR valve opening area detected by an EGR valve lift sensor 131.In other examples, EGR flow may be estimated based on differential pressure across a fixed orifice system. In still further examples, EGR flow may be estimated based on differential pressure across a switchable (e.g., discrete) orifice system. In another example, EGR flow may be determined based on outputs from an EGR measurement system including an intake oxygen sensor 168 (referred to herein as the IAO2 sensor), a mass air flow sensor (not shown), a manifold absolute pressure (MAP) sensor 182, and a manifold temperature sensor 183. In some examples, both EGR measurement systems (i.e., the DPOV system including the differential pressure sensor 125 and the EGR measurement system including the intake oxygen sensor 168) may be used to determine, monitor, and adjust EGR flow.

[0030] In an alternative embodiment, the engine system may include a second LP EGR system (not shown) that directs a desired portion of the exhaust gas from exhaust port 180 to intake port 144. In another alternative embodiment, the engine system may include both of the LP EGR systems described above (one directing exhaust gas from exhaust port 180 to intake port 144 and another directing exhaust gas from exhaust port 170 to intake port 142).

[0031] In another embodiment, the engine system 100, although in Fig. 1, may further include a high pressure EGR system that may direct a desired portion of the exhaust gas from the common exhaust passage 17 upstream of the turbine 124 to the intake manifold 160 downstream of the intake throttle 158.

[0032] The EGR valve 121 may include a body and a stem (not shown), wherein the stem is movable within the body of the EGR valve 121 such that the opening of the EGR valve 121 can be adjusted based on the relative position of the stem and the body. The EGR valve 121 may be configured to adjust an amount and / or rate of exhaust gas redirected through the EGR passage to achieve a desired EGR dilution percentage of the intake charge entering the engine, wherein an intake charge with a higher EGR dilution percentage has a greater ratio of recirculated exhaust gas to air than an intake charge with a lower EGR dilution percentage. It is understood that in addition to the EGR valve position, the AIS throttle position of the AIS throttle 115 and other actuators can also affect the EGR dilution percentage of the intake charge.For example, a position of the AIS throttle may increase the pressure drop across the LP EGR system, allowing more flow of LP EGR into the intake system. This may increase the EGR dilution percentage, whereas a lower LP EGR flow into the intake system may decrease the EGR dilution percentage (e.g., percentage of EGR). Accordingly, EGR dilution of the intake charge may be controlled by controlling EGR valve position and / or AIS throttle position, among other parameters. Thus, by adjusting the EGR valves 121 and / or the AIS throttle 115, an amount (or rate) of EGR flow and, subsequently, a percentage of EGR in the air mass (e.g., the air charge entering the intake manifold) may be adjusted.

[0033] The engine 10 may further include one or more oxygen sensors positioned within the common intake passage 149. Thus, the one or more oxygen sensors may be referred to as intake oxygen sensors. In the illustrated embodiment, an intake oxygen sensor 168 is positioned upstream of the throttle body 158 and downstream of the CAC 154. However, in other embodiments, the intake oxygen sensor 168 may be located elsewhere along the intake passage 149, such as upstream of the CAC 154. The intake oxygen sensor (IAO2) 168 may be a variable voltage (VVs) oxygen sensor or any suitable sensor for providing an indication of the oxygen concentration and EGR concentration of the intake charge air (e.g., the air flowing through the common intake passage 149).In one example, the inlet oxygen sensors 168 may be an inlet oxygen sensor that includes a heating element as a sensing element. During operation, the pumping current of the inlet oxygen sensor may indicate an amount of oxygen in the gas stream.

[0034] A pressure sensor 172 may be positioned adjacent to the oxygen sensor for estimating an intake pressure at which an oxygen sensor output is received. Since the oxygen sensor output is influenced by intake pressure, a reference oxygen sensor output may be learned at a reference intake pressure. In one example, the reference intake pressure is throttle inlet pressure (TIP), with pressure sensor 172 being a TIP sensor. In other examples, the reference intake pressure is manifold pressure (MAP) sensed by MAP sensor 182.

[0035] The engine system 100 may include various sensors 165 in addition to those mentioned above. As in Fig. 1, the common intake passage 149 may include a throttle inlet temperature sensor 173 for estimating throttle air temperature (TCT). Although not shown here, the intake passages 142 and 144 may each further include a mass air flow sensor, or alternatively, the mass air flow sensor may be located in the common passage 140.

[0036] A humidity sensor 189 may be included in only one of the parallel inlet channels. As in Fig. 1, the humidity sensor 189 is positioned in the intake passage 142 (e.g., non-PCV and non-purge bank of the intake passage) upstream of the CAC 154 and an outlet of the LP EGR passage 197 into the intake passage 142 (e.g., intersection between the LP EGR passage 197 and the intake passage 142 where LP EGR enters the intake passage 142). The humidity sensor 189 may be configured to estimate a relative humidity of the intake air. In one embodiment, the humidity sensor 189 is a UEGO sensor configured to estimate the relative humidity of the intake air based on the sensor's output at one or more voltages. Because purge air and PCV air can interfere with the humidity sensor readings, the purge port and PCV port are positioned in a different intake port than the humidity sensor.

[0037] The intake oxygen sensor 168 can be used to estimate an intake oxygen concentration and derive an amount of EGR flow through the engine based on a change in the intake oxygen concentration when the EGR valve 121 opens. In particular, a change in the sensor's output when the EGR valve 121 opens is compared to a reference point at which the sensor is operating without EGR (zero point). Based on the change (e.g., decrease) in the amount of oxygen from the time of operation without EGR, an EGR flow currently supplied to the engine can be calculated. For example, when a reference voltage (Vs) is applied to the sensor, a pumping current (Ip) is output by the sensor. The change in oxygen concentration can be proportional to the change in the pumping current output by the sensor in the presence of EGR relative to the sensor output in the absence of EGR (zero point).Based on a deviation of the estimated EGR flow from the expected (or target) EGR flow, further EGR control may be performed.

[0038] A zero point estimation of the intake oxygen sensor 168 may be performed under idle conditions where intake pressure fluctuations are minimal and when no PCV or purge air is admitted to the low-pressure intake system. Furthermore, idle adjustment may be performed periodically, such as at each initial idle after an engine start, to compensate for the effect of sensor aging and part-to-part variability on the sensor output.

[0039] Alternatively, intake oxygen sensor zero estimation can be performed under non-fueling engine conditions, such as during overrun fuel cut (SAS). Performing the adjustment under SAS conditions can reduce sensor reading fluctuations due to EGR valve leakage, in addition to reducing noise factors such as those achieved during idle adjustment.

[0040] Fig. 2A-2B are a flow diagram of a method 200 that can be used to estimate a parameter (e.g., operating parameter) of a gas flow in an engine system (e.g., engine system 100) based on separate estimates of the gas flow parameter from outputs of two sensors positioned at different locations in the engine system. Thus, method 200 can be used to combine signals derived from measurements or calculations in a flow that are separated by time and location. In particular, combining the signal outputs from two sensors can include taking into account axial diffusion of the gas between the sensor locations and the accuracy of each of the sensors. In describing method 200 in the Fig. 2A-2B, however, an exemplary application of method 200 is shown herein. In this example, method 200 is applied to a low-pressure EGR system for estimating EGR flow using an intake oxygen sensor (such as the one shown in Fig. 1 shown IAO2 sensor 168) and / or a DP sensor (for example the one shown in Fig. 1) of a DPOV system based on engine operating conditions. Instructions for performing method 200 may be stored in a memory of an engine control system, such as the memory of Fig. 1. Furthermore, method 200 may be performed by the controller. The controller may estimate the EGR mass flow using a DP sensor that measures the pressure differential across the EGR valve and a valve position sensor (such as EGR valve lift sensor 131), as described further below with reference to Fig. 3. Furthermore, the controller may estimate a proportion of EGR gas in the intake air from an oxygen sensor located downstream of the DP sensor (for example, the intake oxygen sensor 168), as will be explained below with reference to Fig. 4. Since large errors can occur in each of the oxygen and DP sensor signals depending on engine operating conditions (e.g., PCV and / or purge gases flowing through the intake system, compressor surges active, CBV valve open, etc.), the accuracies of the sensors vary under different engine operating conditions. Thus, method 200 further includes determining when to use the signals from each of the sensors to estimate EGR flow. Method 200 further includes determining the accuracy of the sensor signals. A combined final EGR flow estimate may be obtained by incorporating signals from both the DP and IAO2 sensors based on the accuracy of each sensor's signals. In other words, the accuracy of a sensor's signal (e.g., sensor output) may determine the extent to which its signal influences a final EGR flow estimate.

[0041] In other embodiments, method 200 may be used to make a final estimate of a gas flow parameter for non-EGR gases (e.g., PCV, purge, exhaust, etc.) based on outputs from two sensors positioned at separate locations of engine system 100. For example, the gas flow parameter may be a portion of PCV, purge, or exhaust flow in the engine. Additionally, or alternatively, the gas flow parameter may be a temperature of the gas flow measured at two different locations in the engine system. Thus, method 200 may be used to combine signals from sensors other than an intake oxygen sensor and a DP sensor positioned across an EGR valve.However, method 200 may still include assessing the accuracy of two sensors used to measure the selected gas flow parameter (e.g., the magnitude of a particular gas flow in the engine) based on engine operating conditions and making a final gas flow estimate by incorporating gas flow estimates from both sensors.

[0042] Method 200 begins at 202, and the controller (e.g., controller 12) estimates and / or measures engine operating conditions based on feedback from a plurality of sensors. Engine operating conditions may include engine speed and load, intake air mass, manifold pressure, a position of the CBV, a position of a PCV valve, a position of a purge valve, etc. Method 200 may proceed to 204, and the controller may estimate a first EGR fraction from the DP sensor and determine an accuracy and tolerance for the DP-EGR fraction estimate, as described below with reference to Fig. 3. The tolerance may be a range of EGR fractions based on the EGR fraction estimate. As an example, the accuracy may be an integer value between 0 and 3. In other embodiments, the accuracy value may include additional integer values ​​(e.g., 0, 1, 2, 3, 4, etc.). In still other embodiments, the accuracy may be another numerical value (such as a fractional or non-integer value) that represents a relative accuracy of the EGR fraction estimated with the DP sensor. In other words, the accuracy may be any numerical value along a continuous series of numbers. Finally, at 206, control may estimate a second EGR fraction from the oxygen sensor (e.g., the intake oxygen sensor) and determine a first baseline accuracy of the oxygen sensor outputs.Further, at 206, the controller may estimate the presence of PCV and purge gases in the intake system, as indicated below by the method illustrated in . Fig. 4 will be described in more detail. In other examples, the methods at 204 and 206 may be performed concurrently by the controller. In further examples, the controller may perform the method at 206 before 204.

[0043] After receiving signals from the DP and oxygen sensors, control may continue to 208 and may apply a spatial delay to the oxygen sensor position for all DP, PCV, and purge signals. Specifically, control may apply a first correction factor to the EGR fraction estimate from the DP sensor, along with the estimated DP tolerance and accuracy. The first correction factor may be applied to signals from the DP sensor to account for the time it takes for EGR gases to travel from the DPOV system position to the downstream oxygen sensor. Measurements taken simultaneously from the oxygen sensor and the DP sensor may represent different EGR gases because the oxygen sensor is positioned a distance downstream from the DP sensor.Thus, since it may take some time for the EGR gases flowing through the DPOV system to reach the downstream oxygen sensor, corresponding outputs from the oxygen sensor (e.g., outputs representing the same EGR gas content) may be delayed by the DP sensor. The correction factor may be used to align the DP signals (e.g., DP tolerance, DP accuracy, EGR fraction estimate) with the oxygen sensor signals so that the same, or relatively the same, EGR gases are measured by both sensors. In other words, the correction factor adjusts the DP measurements to represent the EGR flow currently measured by the oxygen sensor. The first correction factor may be the same for the DP tolerance, DP accuracy, and EGR fraction estimate from the DP sensor, as all originate from the position of the DP sensor. Furthermore, the first correction factor may be based on the total volume flow of gas in the intake system.The controller may calculate the correction factor based on a known relationship between the total volumetric flow and the volume of the intake system (e.g., piping, hoses, compressor, CAC) between the DP sensor and the oxygen sensor, which may be stored in the controller's memory. Likewise, a second and third correction factor may be applied to the PCV and purge quantities, respectively. The second correction factor may be calculated based on a known relationship between the total volumetric flow in the intake system and the volume between the PCV inlet (e.g., PCV line 198) and the oxygen sensor. The third correction factor may be calculated based on a known relationship between the total volumetric flow in the intake system and the volume between the purge inlet (e.g., fuel vapor purge line 195) and the oxygen sensor.Because the PCV inlet and purge inlet are positioned separately from each other and from the DP sensor, they can each be separated from the oxygen sensor by a different volume. Thus, the DP signal outputs, the PCV signal outputs, and the purge signal outputs can all have different correction factors.

[0044] After applying the correction factors to the DP, purge, and PCV signals, the controller may proceed to 210 to apply a filter to the DP tolerance and EGR fraction estimate signals from the DP sensor, representing the axial diffusion of the gas mixtures flowing from the EGR inlet pipe and the oxygen sensor. Thus, the digital signals related to the EGR fraction estimate and DP tolerance may be continuously processed by the controller. As an example, the filter may be a first-order moving average filter. For example, the primary filter may be a low-pass filter configured to reduce the impact of signal response frequencies above a threshold frequency on the overall DP tolerance and EGR fraction estimate signal. In one example, the time constant of the filter may be preset and stored in the controller's memory.In another example, the time constant of the filter may change depending on engine operating conditions (for example, whether a CBV valve (for example, CBVs 152 and 155) is open or closed, the total volume flow of gases in the intake system, etc.).

[0045] Control may then proceed to 212 to determine if the DP sensor accuracy is decreasing. If the DP sensor accuracy is increasing, then control may proceed to 216 and adjust the output of the first filter at 210 based on a first threshold. In particular, control may adjust the DP sensor accuracy such that the adjusted accuracy can only increase if the accuracy output not adjusted prior to 216 has increased above a higher first threshold. Thus, control may only increase the accuracy value assigned to the DP sensor from the currently assigned value if the accuracy increases above the first threshold. The first threshold may be closer to the next higher accuracy value from the current accuracy value than the current accuracy value to ensure that the DP sensor accuracy is not overestimated.In one example, at 216, the controller may adjust the output of the first filter of 210 using a comparator. Specifically, the controller may apply a comparator to the output of the filter in 210 that uses a threshold near the next higher integer value, such that the output of the comparator changes its integer state when the filtered output of 210 is within a small, calibratable value (fixed value or percentage) of the next higher integer value. As shown in FIG. Fig. 3, the accuracy of the DP sensor may be assigned an integer value from 0 to 3. The comparator at 216, which is applied to the filtered DP accuracy signal at 210 as it increases, uses a threshold value close to the next higher integer value to ensure that the accuracy of the DP sensor does not increase to the next integer value (state) until a majority of the gas in the axial diffusion volume has reached the oxygen sensor. Conversely, if control at 212 determines that the DP accuracy is decreasing, control may transfer to 216 to adjust the DP accuracy based on a lower second threshold value. Thus, if the accuracy decreases below the second threshold value, control may decrease the accuracy value assigned to the DP sensor from the currently assigned value.The second threshold may be closer to the current accuracy value than the next lower accuracy value to the current accuracy value to ensure that the accuracy of the DP sensor is not overestimated. In one example, the controller may apply a comparator to the output of the filter in 210 that uses a threshold that is far from the next lowest integer value, such that the comparator's output changes its integer state when the filtered output of 210 is within a large, calibratable value (fixed value or percentage) of the next lowest integer value. In other words, the comparator threshold is close to the current integer value, such that the comparator changes its integer state when the filtered output of 210 is within a small, calibratable value (fixed value or percentage) of the current integer value.Thus, the accuracy value assigned to the DP sensor may be reduced as the sensor's accuracy signal decreases. Applying a comparator threshold far removed from the current integer value to the filtered DP accuracy signal at 210 only when accuracy increases, in some examples, thus delays the time at which the DP accuracy signal increases to its integer value until the probability that the axial diffusion volume has passed the oxygen sensor and may limit overestimations of the DP sensor's accuracy.Conversely, applying a comparator threshold close to the current integer value to the filtered DP accuracy signal in 210 when the accuracy is decreasing does not delay the time at which the DP accuracy signal decreases its integer value and thus decreases its value when the onset of the axial diffusion volume has reached the oxygen sensor, and again limits overestimations of the accuracy of the DP sensor.

[0046] In another embodiment, for conditions where the integer value is increasing and decreasing, the controller may apply a comparator with thresholds that are far from and close to the current integer precision value, respectively, omit the filter in 210 for cases where the integer precision value is decreasing, and use a comparator threshold that is far from the current integer precision value, whereby the output of the comparator at 212 changes state to the next lower integer value immediately upon a change in the integer precision value entering the comparator.

[0047] Thus, once the controller has applied the spatial delay at 208, the filter at 210, and the comparator at 216, the EGR fraction estimate signals from the DP sensor, the DP sensor accuracy, the DP tolerance, the PCV flow, and the purge flow can all be timed to the signals from the oxygen sensor so that all signals can reflect the gases currently measured at the oxygen sensor.

[0048] The controller may then proceed from 216 or 214 to 218 to determine whether the accuracy of the DP sensor is equal to 1. As described below with reference to Fig. 3, the accuracy of the DP sensor may be assigned a value of 1 when compressor surge is active and / or the CBV is open. If the accuracy assigned to the DP sensor is 1 after the spatial delay at 208 and potential filtering at 216 and adjustments at 216, then the method 200 may continue to 222 to apply a second filter to the DP EGR fraction signal with a lower cutoff frequency than the first filter for a calibratable period of time when the controller has detected a change in compressor surge state and / or CBV valve command. Since surge may be active and / or the CBV may be open for relatively short time frames (e.g., 1 second), changes in the DP sensor EGR fraction signal due to surge and / or CBV position may be dampened with the second filter.Thus, the second filter for the EGR fraction signal from the DP sensor at 222 maintains a relatively stable EGR estimate even if the DP sensor accuracy may be low (e.g., an accuracy value of 1) while a CBV opening and closing event is occurring and / or surge is active. If control has not detected a compressor surge state change or CBV valve command at 218 (e.g., the DP accuracy is not equal to 1), then control may proceed to 220 and not apply a second filter to the DP EGR fraction signal.

[0049] The control can be switched from either 220 or 222 to Fig. 2B. Then the procedure 200 can be Fig. 2A to 224 in Fig. 2B, and control may determine if crankcase ventilation (PCV) flow (from an engine crankcase) is increasing. As described above, increases in PCV flow may then increase PCV flow through the intake passage and past the intake oxygen sensor. Increases in PCV and / or purge flow (for example, purge flow from an engine fuel purge canister) may decrease the accuracy of the oxygen sensor. In particular, EGR estimates from the oxygen sensor may be overestimated because the oxygen sensor may register the additional hydrocarbons from the PCV and / or purge gases as EGR gases. In particular, the increase in hydrocarbons from the PCV and / or purge gases may result in a decrease in the oxygen concentration registered by the oxygen sensor, which in turn may result in an overestimation of EGR flow.If control determines at 224 that PCV is increasing, then control transfers to 226 and may adjust the PCV signal based on a third threshold. Thus, control may increase the PCV signal output of the filter in 210 as the PCV signal increases above the third threshold. The third threshold may be closer to the current value than the next higher value to ensure that the accuracy of the oxygen sensor is not overestimated. In one example, control may adjust the PCV signal by applying a comparator to the output of the filter in 210 that uses a threshold that is far from the next higher integer value such that the comparator's output changes its integer state when the filtered output of 210 is within a large, calibratable value (fixed value or percentage) of the next higher integer value.In other words, the comparator threshold is close to the current integer value, so the comparator changes its integer state when the filtered output of 210 is within a small, calibratable value (fixed value or percentage) of the current integer value. Thus, the integer state assigned to the PCV-on signal can be increased upon a small increase in the filtered PCV-on signal of the sensor of 210. Applying a comparator threshold close to the current integer value to the filtered PCV-on signal at 210 only when the on flag increases from 0 to 1 does not delay the time at which the PCV-on signal increases its integer value until the probability that the axial diffusion volume has passed the oxygen sensor and can limit overestimations of the oxygen sensor's accuracy due to PCV.Conversely, applying a comparator threshold far removed from the current integer value to the filtered PCV-on signal in 210 as the signal decreases delays the time at which the PCV-on signal decreases its integer value and thus decreases its value when the end of the axial diffusion volume has reached the oxygen sensor, again limiting overestimations of the oxygen sensor's accuracy.

[0050] In another embodiment, in cases where the integer PCV-on value is increasing before the comparator is applied, the controller may omit the filter at 210 (or apply it with a filter constant of zero). The comparator threshold may be far from the current integer PCV-on value, causing the comparator output to change state to the next higher integer value immediately upon an increase to the integer PCV-on value entering the comparator at 224. As described below with reference to Fig. 4, PCV flow in the intake system may be estimated based on manifold inlet pressure and may be classified as on or off (e.g., by assigning an integer value, 0, or 1, to the PCV signal). As an example, PCV and / or purge may be determined as on or off (e.g., flowing or not flowing to the intake port and past the oxygen sensor) based on a position of a PCV valve and / or fuel canister purge valve. As another example, PCV and / or purge may be determined as on or off (e.g., flowing or not flowing to the intake port and past the oxygen sensor) based on engine boost (e.g., whether the engine is boosted or not boosted).Thus, by omitting the filter in 210, applying a filter with a time constant of 0, and using a comparator threshold far removed from the current integer PCV-on value, or applying a filter with the "normal" time constant and using a comparator threshold close to the current integer PCV-on value, any increase in PCV levels can be registered by the controller (e.g., registered immediately), and the PCV signal can be set to "on" (it can be assigned a value of 1), so that the oxygen sensor accuracy can be reduced accordingly. Thus, overestimations of the oxygen sensor accuracy can be reduced. Conversely, if the PCV current does not increase at 224, then the controller can proceed to 228 and can adjust the PCV signal based on a fourth threshold.Thus, the controller may decrease the PCV signal output of the filter at 210 when the PCV signal decreases by more than the third threshold. The fourth threshold may be farther from the current PCV value than the next lower value of the current value to ensure that the oxygen sensor accuracy is not overestimated. In one example, the controller may adjust the PCV signal by applying a comparator threshold far from the current integer value to the filtered PCV-on signal at 210 and will delay the time at which the PCV-on signal decreases its integer value, thus decreasing its value when the end of the axial diffusion volume has reached the oxygen sensor, again limiting overestimations of the oxygen sensor accuracy.The PCV signal filter and comparator can ensure that PCV hydrocarbons are no longer present in the intake system before the PCV signal is set to "off" (assigned a value of 0) and the oxygen sensor accuracy is subsequently adjusted (for example, increased).

[0051] From either 226 or 228, method 200 may proceed to 230, where control may determine if purge flow from a fuel canister purge system and to the intake passage upstream of the intake oxygen sensor is increasing. Similar to 224, if control determines that purge is increasing at 230, control proceeds to 232 and may adjust the purge signal based on a fifth threshold. Thus, control may increase the filter purge signal output at 210 if the purge signal increases by more than the fifth threshold. The fifth threshold may be closer to the current purge value than the next higher value to the current value to ensure that oxygen sensor accuracy is not overestimated.In one example, the controller may adjust the purge signal by applying a comparator to the output of the filter in 210 that uses a threshold far from the next higher integer value, such that the comparator's output changes its integer state when the filtered purge output from 210 is within a large, calibratable value (fixed value or percentage) of the next higher integer value. In other words, the comparator threshold is close to the current integer value, such that the comparator changes its integer state when the filtered purge output from 210 is within a small, calibratable value (fixed value or percentage) of the current integer value. Thus, the integer state assigned to the purge-on signal may be increased with a small increase in the filtered purge-on signal from the sensor of 210.Applying a comparator threshold close to the current integer value to the filtered purge-on signal in 210 only when the on flag increases from 0 to 1 does not delay the time at which the purge-on signal increases its integer value until the probability that the axial diffusion volume has passed the oxygen sensor and can limit overestimations of the oxygen sensor's accuracy due to purging.

[0052] In another example, the controller may omit the filter at 210 (or apply it with a filter constant of 0) in cases where the purge-on integer value increases. Further, the controller may use a comparator threshold that is far from the current purge-on integer value, causing the comparator output to change state to the next higher integer value immediately upon an increase to the purge-on integer value entering the comparator at 224.

[0053] If control determines at 230 that purge is not increasing, control may proceed to 234 and adjust the purge signal based on a sixth threshold. Thus, control may decrease the filter purge signal output at 210 if the purge signal decreases by more than the sixth threshold. The sixth threshold may be farther from the current purge value than the nearest lower value to the current value to ensure that oxygen sensor accuracy is not overestimated.In one example, the controller may adjust the purge signal by applying a comparator threshold far from the current integer value to the filtered purge-on signal in 210 as the signal decreases, and may delay the time at which the purge-on signal decreases its integer value and thus decreases its value when the end of the axial diffusion volume has reached the oxygen sensor, and may limit overestimations of the oxygen sensor's accuracy.

[0054] As explained below with reference to Fig. As described in more detail in Figure 4, the purge flow can be estimated based on the manifold inlet pressure and can be classified as on or off (for example, by assigning an integer value of 0 or 1 to the PCV signal). Thus, any increase in purge levels is immediately registered by the controller, allowing the purge signal to be set to "on" (assigning it an integer value of 1), and the oxygen sensor accuracy can be reduced accordingly. Thus, overestimations of the oxygen sensor accuracy can be reduced. The purge signal filter and comparator can ensure that purge hydrocarbons are no longer present in the intake system before the purge signal is set to "off" and the oxygen sensor accuracy is subsequently adjusted.It is important to note that, alternatively, the controller may perform steps 230-234 before performing steps 224-228. In other examples, the controller may perform both sets of steps at the same time (e.g., simultaneously).

[0055] After analyzing the PCV and purge signals, control may proceed to 236 and calculate a final oxygen sensor accuracy (e.g., a final accuracy value). The initial oxygen sensor baseline accuracy of 206 may be updated based on whether PCV and / or purge hydrocarbons are likely present or absent at the oxygen sensor location (i.e., using the PCV-on and purge-on integer signals). As described below with reference to Fig. 4, the oxygen sensor's first base accuracy may be an integer value from 0 to 2. If the oxygen sensor's first base accuracy is 0 (representing the case where the oxygen sensor is not ready, is faulty, or idle pressure compensation has not completed), then the controller may assign a final accuracy of 0 (not ready or faulty) for the oxygen sensor. If the oxygen sensor's first base accuracy is 1 or 2 (representing cases where the oxygen sensor has not completed its higher pressure compensation, or where it has completed it, respectively) and purge and PCV gases are determined not to be present at the oxygen sensor (indicated by the PCV on and purge on integer signals both being zero), then the final accuracy may increase by a value of one above the integer base accuracy value.For example, if purge and PCV gases are determined not to be present at the oxygen sensor and the oxygen sensor baseline accuracy is 1, then the final oxygen sensor accuracy would be assigned a value of 2. Thus, the final oxygen sensor accuracy can be assigned an integer value from 0 to 3. However, if either purge and / or PCV gases are determined to be present at the oxygen sensor, then the first baseline oxygen sensor accuracy is preserved in the final oxygen sensor accuracy. For example, if either purge and / or PCV are determined to be present at the oxygen sensor and the first baseline accuracy is 2, then the final accuracy assigned to the oxygen sensor can also be 2.

[0056] Thus, the controller may cycle through 224-236 to calculate a final oxygen sensor accuracy that accounts for the presence of purge and / or PCV hydrocarbons, which may affect the accuracy of the oxygen sensor signal output. Likewise, the controller may calculate a final DP accuracy from 212 to 222, which may be used to adjust the EGR fraction estimate from the DP sensor, depending on whether pumping is active and / or a CBV is open. After the controller calculates the final oxygen sensor accuracy at 236, all of the signals required to calculate the final EGR fraction, including the DP EGR fraction, the oxygen sensor EGR fraction, the DP tolerance, the DP accuracy, and the oxygen sensor accuracy, have been collected and timed, accounting for time delay and axial diffusion.These signals may then be used by the controller later in method 200 to determine a final proportion of EGR gas in the intake air, as discussed in more detail below. It is important to note that in other examples, the controller may perform 224-236 concurrently with 212-222. In further examples, the controller may perform 224-236 before executing 212-222.

[0057] Method 200 may transition from 236 to 238, and the controller may estimate the proportion of EGR gases in the intake air based on the DP estimate of the EGR flow, the oxygen sensor estimate of the EGR flow, the DP accuracy value, the DP EGR tolerance value, and the oxygen sensor accuracy value (e.g., the final accuracy value). For example, a table of arbitration rules, including DP sensor and oxygen sensor accuracy values, may be stored in the controller's memory, as described below with reference to Fig. 5. The arbitration rules may include commands for determining how the EGR fraction and DP tolerance estimates from the oxygen and DP sensors are to be used to obtain a final EGR fraction estimate. In particular, the accuracy values ​​assigned to the DP sensor at either 214 or 216 and the oxygen sensor at 236 may be assigned to a particular command or combination of EGR signals in the table stored in the controller's memory (for example, block diagram 500 in Fig. 5), which can then be used to determine a final fraction of EGR gases in the intake air. For example, if the accuracy values ​​of the DP sensor and the oxygen sensor are both 2, the controller may determine that the corresponding command in the lookup table specifies that the EGR fraction estimate from the oxygen sensor should be used for the final EGR flow estimate (see Fig. 5 for the command corresponding to the accuracy values ​​of 2). However, the EGR flow estimate may be limited to a value within the DP tolerance interval of the EGR fraction estimate from the DP sensor. If the EGR fraction estimate from the oxygen sensor is below the lower limit of the DP tolerance interval from the DP sensor, then the final EGR fraction estimate may thus be a value of the lower limit of the DP sensor's tolerance interval. In other words, the oxygen sensor EGR fraction estimate may be clipped to the limits of the DP sensor's tolerance interval if the EGR fraction estimate is outside the limits of the tolerance interval (see Fig. 5 for a more detailed description of the arbitration rules used to determine the final EGR fraction. Thus, the final EGR fraction estimate may be a combined EGR fraction estimate that may include signals from both the oxygen and DP sensors (e.g., EGR estimate from the oxygen sensor, EGR fraction from the DP sensor, oxygen sensor accuracy, DP sensor accuracy, and DP tolerance interval).

[0058] After determining the final fraction of EGR gas in the intake air at 238, control may proceed to 240 to evaluate whether the rate of change of the estimated EGR fraction is greater than a threshold or not greater than a threshold. In one example, the threshold rate of change of EGR fraction may be the difference between the currently measured EGR fraction and the last estimated EGR fraction (e.g., combined final EGR fraction). In other examples, the threshold rate of change of EGR fraction may be an extent to which the estimated EGR fraction fluctuates over a preset period of time. If the rate of change of EGR fraction at 240 is below the threshold, then control may proceed to 241 to maintain the final EGR fraction determined at 238.However, if at 240, control determines that the rate of change of the EGR fraction is greater than the threshold rate, then method 200 may proceed to 242, and control may limit the EGR rate of change to an upper threshold. If the EGR flow remains constant, the EGR flow estimated by control may still change because it is subject to accuracies of the DP and oxygen sensors. Thus, the estimated EGR flow may change depending on the accuracy state estimates of the sensors. Changes in the accuracies of any of the sensors may result in a change in the arbitration rule used to determine how the sensor signals may be incorporated into a final EGR flow estimate.Thus, the rate of change in EGR fraction may be limited to an upper threshold so that changes in the estimated EGR fraction can reflect actual changes in EGR flow rather than changes in the arbitration rules used to calculate a final EGR fraction estimate. In one example, the upper threshold may be a preset constant stored in the controller's memory. In another example, if there is a change in sensor accuracy and the arbitration rule dictates how the sensor signals are used to calculate the final EGR flow, the upper threshold may be the change in EGR fraction that would have occurred had there been no change in the arbitration rule.In another example, the upper threshold may be the greater of either a preset constant or the change in EGR fraction that would have occurred had there been no change in the arbitration rule. Controller 200 may transition from either 241 or 242 to 244, and controller may adjust the EGR valve (e.g., EGR valve 121) based on the final EGR fraction estimate. In particular, controller may adjust the position of the EGR valve based on the final EGR fraction estimate and a desired EGR fraction. If the estimated EGR fraction is below a desired EGR fraction, controller may adjust (e.g., open) the EGR valve to allow more EGR gases to be recirculated to the intake system.Conversely, if the estimated EGR fraction is below a desired EGR fraction, the controller may adjust the EGR valve (e.g., close it) so that less EGR gases are recirculated to the intake system. The desired EGR fraction may be based on engine operating conditions, such as engine speed and engine load. The process may then loop back.

[0059] Now on Fig. Referring to Figure 3, a flowchart of a method 300 for evaluating the accuracy of a DP sensor used to estimate EGR flow (e.g., DP sensor 125) under various engine operating conditions is shown. Instructions for performing method 300 may be stored in a memory of an engine controller, such as the memory shown in Fig. 1. Furthermore, method 200 may be performed by the controller. It is important to note that method 300 may run continuously during engine operation. Thus, the controller may continuously update the accuracy of the DP sensor. In some examples, the controller may also store accuracy values ​​in the controller's memory.

[0060] Method 300 begins at 302, and the controller (e.g., controller 12) estimates and / or measures engine operating conditions based on feedback from a plurality of sensors. The engine operating conditions may include engine speed and load, intake air mass, manifold pressure, a position of the CBV, a position of a PCV valve, a position of a purge valve, engine boost, etc. Control may proceed to 304 and may estimate a first EGR flow rate through an EGR valve (e.g., EGR valve 121) and a tolerance interval of a DP sensor (DP sensor 125). In particular, the EGR flow estimate may be based on an output of the DP sensor and the flow area of ​​the EGR valve. The passage area of ​​the EGR valve may be estimated based on a known cross-section of the EGR valve and an EGR valve position based on an output of an EGR valve position sensor (for example, the EGR valve lift sensor 131).Thus, signals from a DPOV system including the DP sensor, EGR valve, and EGR valve position sensor may be used jointly by the controller to determine EGR flow. The tolerance interval (e.g., the estimate tolerance) may be calculated based on a known relationship between the tolerance interval and the pressure change across the EGR valve and the estimated or known valve opening range. Thus, the controller may look up a tolerance interval corresponding to pressure changes across the EGR valve output by the DP sensor. The tolerance interval may specify a margin of error above and below the EGR flow estimate. In other words, the tolerance interval specifies an estimate of EGR flow within a range of values ​​based on the first EGR flow estimate.Once control has estimated the EGR flow using the DP sensor, method 300 may proceed to 306, and control may convert the EGR flow into a fraction of EGR gases in the intake air. This may be accomplished by dividing the EGR flow estimated at 304 by the total mixture flow at the compressor inlet (for example, at compressor 122). The fraction of EGR gases in the intake air and the DP tolerance calculated at 306 and 304, respectively, may then be used at 204 of method 200. Fig. 2A. Thus, the EGR flow may be converted to an EGR fraction since the EGR estimates from the DP sensor and an oxygen sensor (e.g., oxygen sensor 168) are combined as previously described with reference to method 200 of FIGS. Fig. 2A-2B, can be incorporated into a final EGR fraction estimate. Because oxygen sensor outputs provide a measurement of EGR flow in units of a fraction of EGR gases in the intake air, the EGR flow estimated by the DP sensor may need to be converted to units common to the oxygen sensor for direct comparison.

[0061] Method 300 may proceed to 308, and control may determine whether a DP sensor fault flag has been set or not set. A DP sensor fault flag may include indications when the DP sensor is not operational. For example, soot may accumulate on the EGR valve over time and with engine use and may affect the outputs of the DP sensor. If control detects soot buildup on the EGR valve outside of a certain limit for which compensation may be possible, then control may signal a DP sensor fault flag. Similarly, control may also signal a DP sensor fault flag if the DP sensor measuring pressure across the valve opening or the DP sensor measuring valve opening (or possibly valve lift) is faulty. If the controller determines that the DP sensor is faulty or inoperative, then the controller can proceed to 310 and set the DP accuracy to 0.From 310, the method may return. If control determines at 308 that no DP sensor fault flag has been set, then control may proceed to 312 to determine if compressor surge is active and / or the CBV valve (e.g., CBV 152 and / or 145) is open or opening. If either the CBV is opening and / or open or compressor surge is active (e.g., the compressor is surged), then control may proceed to 314 and set the DP sensor accuracy to 1. Then the method may return. However, if both the CBV is closed and surge is inactive, then method 300 may proceed to 316, and control may determine if the pressure change across the EGR valve (e.g., the differential pressure output by the DP sensor) is greater than a higher first threshold.If the pressure change across the EGR valve is greater than a higher first threshold, then control may continue to 318 and set the DP sensor accuracy to 3. Then, the method may loop back. If the pressure change across the EGR valve, as registered by the DP sensor, is less than the higher first threshold, then control may continue to 320 and determine if the pressure change across the EGR valve is less than a lower second threshold. The first and second thresholds may be preset and stored in the controller's memory, with the second threshold being less than the first threshold. If the pressure change across the EGR valve is less than the lower second threshold, then control may continue to 322 and set the DP sensor accuracy to 2. Then, the method may loop back.However, if the pressure change across the EGR valve is greater than the lower second threshold, then the pressure change may be between the first and second thresholds, and control may continue to 324 and determine whether the last DP accuracy value was a 0 or a 1. If the last recorded DP sensor accuracy was a 0 or a 1, then control may continue to 322 and set the DP sensor accuracy to 2. However, if control determines at 324 that the previous DP accuracy was 2 or 3, then control may maintain the previous accuracy value at 326. Then, the method may loop back. The accuracy values ​​assigned to the DP sensor signals may then be provided as inputs to 204 of method 200 in FIG. Fig. 2A can be used.

[0062] Thus, method 300 may include estimating a fraction of EGR gases in the intake air and further estimating a DP sensor tolerance indicating an allowable error margin for the EGR fraction estimate. Further, method 300 may include assigning an accuracy to the DP sensor signal based on a sensor fault flag, compressor surge, a status of the CBV, and the pressure change across the EGR valve. Thus, method 300 may include estimating the EGR fraction to within a range and calculating an accuracy for the EGR fraction estimate based on engine operating conditions. The accuracy value assigned to the DP sensor, the EGR fraction estimate, and the DP sensor tolerance may then be used in the manner described previously with reference to the Fig. 2A-2B may be used to calculate a final EGR fraction that includes both the DP sensor signals and signal outputs from an oxygen sensor (e.g., oxygen sensor 168). Specifically, the accuracy, tolerance, and EGR fraction signals from the DP sensor may be further processed by filtering and timing with the oxygen sensor. The processed signals may then be used to estimate a final EGR fraction based on arbitration rules, as described below with reference to Fig. 5 will be discussed in more detail.

[0063] Now on Fig. Referring to Figure 4, a flowchart of a method 400 for estimating a proportion of EGR gases in the intake air of an engine using an intake oxygen sensor (e.g., oxygen sensor 168) and evaluating the accuracy of oxygen sensor outputs is shown. Instructions for performing method 400 may be stored in a memory of an engine controller, such as the memory shown in Fig. 1. Further, method 400 may be executed by the controller. It is important to note that method 400 may run continuously during engine operation. Thus, the controller may continuously update the oxygen sensor accuracy. In some examples, the controller may also store accuracy values ​​in the controller's memory.

[0064] Method 400 begins at 402, and the controller (e.g., controller 12) estimates and / or measures engine operating conditions based on feedback from a plurality of sensors. Engine operating conditions may include engine speed and load, intake air mass, manifold pressure, a position of the CBV, a position of a PCV valve, a position of a purge valve, etc. After estimating and / or measuring engine operating conditions, the controller may proceed to 404 and estimate EGR flow using the oxygen sensor. The oxygen sensor may be used to estimate an intake oxygen concentration and infer a portion of EGR gases in the intake air based on a change in the intake oxygen concentration when the EGR valve (e.g., EGR valve 121) opens. In particular, a change in the sensor's output when the EGR valve opens is compared to a reference point where the sensor is operating without EGR (zero point).Based on the change (e.g., decrease) in the amount of oxygen from the time of operation without EGR, an EGR flow currently supplied to the engine may be calculated. For example, when a reference voltage (Vs) is applied to the sensor, a pumping current (Ip) is output from the sensor. The change in oxygen concentration may be proportional to the change in the pumping current output (delta Ip output) from the sensor in the presence of EGR relative to the sensor output in the absence of EGR (zero point). The fraction of EGR gases in the intake air estimated using the outputs from the oxygen sensor may then be used as inputs at 206 in method 200 of the . Fig. 2A-2B can be used. Thus, the EGR fraction estimated at 404 can be used in the manner described above with reference to the Fig. 2A-2B may be used to calculate a final EGR estimate that includes signals from both the oxygen sensor and a DP sensor (e.g., DP sensor 125).

[0065] Method 400 may continue to 406, and control may determine whether an oxygen sensor idle adjustment routine has ended. As an example, the idle adjustment routine may include learning a zero point and / or baseline oxygen sensor correction factors under a known pressure. In the example of an oxygen sensor positioned upstream of the throttle, the correction factor may be based on a known barometric pressure achieved at the oxygen sensor for idle conditions. If control determines that the oxygen sensor idle adjustment has not ended (or determines that the oxygen sensor is faulty), then control proceeds to 408 and sets the oxygen sensor base accuracy to 0. However, if the oxygen sensor idle adjustment has ended, then method 400 proceeds to 410 and determines whether the oxygen sensor pressure adjustment has ended.Pressure adjustment may include correcting the oxygen sensor outputs based on the measured values ​​at elevated inlet pressures at the oxygen sensor location up to the maximum expected operating pressures of the oxygen sensor in the application. Oxygen sensors may have a pressure dependence that may affect the diffusion characteristics of the sensing element, resulting in a gain error in the pumping current (Ip) of the sensor output. This can be a significant noise factor for variable voltage (VV) measurements. To correct such errors, the oxygen sensor output may be corrected based on a currently measured pressure, a dry air correction factor, and a pressure dependence factor based on the water vapor environment around the exhaust oxygen sensor. If pressure adjustment has not been completed, the controller may set the oxygen sensor base accuracy to 1 at 412.However, once pressure adjustment has been completed, the controller may set the oxygen sensor base accuracy to 2 at 414.

[0066] Thus, from 406 to 416, method 400 may include assigning a base accuracy value to the oxygen sensor based on whether an oxygen sensor fault has been detected and whether an idle adjustment routine and pressure adjustment routine have completed. However, purge flow and / or PCV flow hydrocarbons may also affect the oxygen sensor reading. In particular, the oxygen sensor may overestimate EGR flow when purge and / or PCV hydrocarbons are flowing through the intake system because the oxygen sensor may register the hydrocarbons from the purge and / or PCV gases as hydrocarbons from EGR gases. Thus, from 416 to 426, method 400 may include determining whether purge and / or PCV gases are flowing in the intake system and potentially affecting the oxygen sensor output.Because the purge and PCV inlets (e.g., fuel vapor purge line 195 and PCV line 198) are positioned a distance upstream of the oxygen sensor, the PCV and purge signals received by the controller in method 400 may be time-delayed and filtered before being incorporated into a final oxygen sensor accuracy. As described above with reference to method 200 in FIGS. Fig. 2A-2B, the PCV and purge signals may be specifically adjusted to account for the time it takes for the intake gas to flow from the PCV and purge inlet to the oxygen sensor.

[0067] Referring again to method 400, control may transition from 414 to 416 and determine if purge is active and hydrocarbons are flowing from the purge inlet through the engine's intake system. Purge may be active when the manifold air pressure is higher than a first threshold. The threshold may be preset and stored in the controller's memory. For example, the threshold may be a barometric pressure (e.g., ambient pressure). If the manifold air pressure is at or below the first threshold (e.g., the engine is not boosted) and purge is not active, then control may transition to 418 and set a purge flag to 0, indicating that no purge hydrocarbons are flowing through the purge passage. If control determines that purge is active, then control may transition to 420 and set the purge flag to 1, indicating that purge is active.Method 400 may transition to 422 from either 418 or 420, and control may determine if PCV is active and PCV hydrocarbons are flowing through the PCV passage. Control may determine PCV is active if manifold air pressure is greater than barometric pressure, indicating that the engine is boosted. If at 422, control determines that manifold air pressure is not above barometric pressure and PCV is not active, then method 400 may continue to 424, and control may set a PCV flag to 0, indicating PCV is not active. However, if at 422, control determines that manifold air pressure is above barometric pressure, then control may set a PCV flag to 1, indicating PCV is active. Thus, method 400 may include determining whether purge and PCV gases are flowing through the intake system or not flowing therethrough.The flow of purge and PCV gases in the intake system may then be stored in the controller's memory and used in method 200 to make a final estimate of the oxygen sensor accuracy, as described above with reference to FIG. Fig. 2A-2B. Further, it should be noted that in one example method, steps 422-426 may occur concurrently with steps 416-420. In another example, steps 422-426 may occur before steps 416-420. Further, control may calculate the oxygen sensor baseline accuracy (404-414) concurrently with estimating purge and / or PCV flows (416-426). In another example, control may estimate purge and / or PCV flows (416-426) prior to calculating the oxygen sensor baseline accuracy (404-414).

[0068] Now on Fig. 5, a block diagram 500 shows a table for determining how to estimate a proportion of EGR gases in the intake air using a DP sensor (e.g., DP sensor 125) and an oxygen sensor (e.g., oxygen sensor 168). As an example, the block diagram 500 may be implemented by a controller (e.g., controller 12) in the manner described above with reference to FIG. Fig. 2A-2B. In particular, the block diagram 500 may include the arbitration rules used in step 238 in method 200, as described above with reference to Fig. 2A-2B. However, it is important to note that the arbitration rules included in block diagram 500 are only example arbitration rules that may be used in method 200. In other embodiments, additional or alternative arbitration rules may be used by the controller to make a final EGR fraction estimate that includes outputs from both the oxygen and DP sensors and is based on accuracy values ​​of the two different sensor measurements. Thus, block diagram 500 may be used by the controller to determine the final estimate of the fraction of EGR gases in the intake air based on the accuracies of the oxygen and DP sensors, the EGR fractions estimated using both sensor signals, and the tolerance of the DP sensor.It is important to note that since block diagram 500 is used in step 238 in method 200, the EGR fraction estimate signals from the DP sensor, the DP sensor accuracy, and the DP tolerance may already be timed to the oxygen sensor and properly filtered before the arbitration rules in block diagram 500 are used to determine a final EGR fraction estimate. For example, if the DP accuracy is 1 (e.g., compressor surge is active and / or a CBV valve is open), the EGR fraction signal from the DP sensor may already have been filtered by the second filter (with a lower cutoff frequency) at 222 of method 200. In particular, the cutoff frequency and thus the frequency of the signals that can pass through the filter may be reduced in the second filter compared to the first filter applied to the EGR component signal when the DP sensor accuracy is greater than 1.At DP accuracies of 2 and 3, purge may be inactive, and a CBV may be closed. Furthermore, the final oxygen sensor accuracy has been calculated based on the timed and filtered PCV and purge signals. Thus, at step 238 in method 200, the final accuracy values ​​for both the DP sensor and the oxygen sensor may be known. Thus, the controller may look up the rule in block diagram 500 corresponding to the accuracy values ​​for the oxygen and DP sensors and determine the final EGR fraction based on the arbitration rule described in block diagram 500.

[0069] As mentioned above with reference to the Fig. 2A-2B, purge and / or PCV hydrocarbons may be present in the intake system (at the oxygen sensor location) at oxygen accuracy values ​​of 1 or 2. At an oxygen accuracy of 0, the oxygen sensor may be failing due to idle adjustment not being completed, as discussed with reference to Fig. 4, may be faulty. At an oxygen accuracy of 3, PCV and / or purge hydrocarbons may not be present in the intake system at the oxygen sensor location, as discussed in more detail in Fig. 2 and Fig. 4 discussed in more detail.

[0070] The oxygen sensor accuracies are sorted along the columns in the first row of block diagram 500 with decreasing accuracy from left to right. The DP accuracies are sorted along the rows in the first column of block diagram 500 with decreasing accuracy from top to bottom. The accuracy values ​​(e.g., 0 to 3) for the DP and oxygen sensors in block diagram 500 may be the same as described above with reference to the Fig. 2A-2B correspond to the 200 calculated accuracy values ​​for the DP and oxygen sensor.

[0071] Referring now to the rules included in block diagram 500 for calculating a final fraction of EGR gases in the intake air, the controller may not make (or determine) an EGR estimate if the accuracy of either the DP sensor or the oxygen sensor is 0, as shown at 505, 509, and 513-517.

[0072] If the oxygen sensor accuracy is 1 and the DP sensor accuracy is 3, as shown at 510, then control may use exclusively the EGR fraction estimate from the DP sensor for the final EGR fraction estimate. In other words, the final EGR estimate may equal the EGR fraction estimate from the DP sensor.

[0073] When the oxygen sensor accuracy is 1 and the DP sensor accuracy is 1 or 2, as shown at 511 and 512, or when the oxygen sensor accuracy is 2 and the DP sensor accuracy is greater than 0, as shown at 506-508, the controller may limit the oxygen sensor EGR fraction estimate to within the limits of the DP sensor tolerance interval. Thus, the final EGR fraction estimate may correspond to the oxygen sensor EGR fraction estimate determined from the oxygen sensor when the oxygen sensor EGR fraction estimate is within the DP sensor tolerance interval. However, if the EGR fraction estimate from the oxygen sensor is outside the DP sensor tolerance interval, then the final EGR fraction estimated by the controller may correspond to the upper or lower limit of the DP tolerance, whichever is closer to the oxygen sensor EGR fraction.

[0074] If the oxygen sensor accuracy is at the upper threshold (for example, at 3) and the DP sensor accuracy is greater than 0, as shown at 502-504, and the water vapor / droplets at the oxygen sensor are determined to be absent, then the controller may use the oxygen sensor EGR fraction estimate for the final estimate of the fraction of EGR gases in the intake air. The upper threshold oxygen sensor accuracy may be a maximum achievable accuracy for the oxygen sensor. The controller may determine that the upper accuracy threshold has been met when the PCV and purge gases are not bypassing the oxygen sensor, the sensor is not faulty and has completed an idle adjustment routine, and no water vapor / droplets are present at the oxygen sensor. Thus, the final EGR fraction estimate may correspond to the oxygen sensor EGR fraction estimate.In another example, if water droplets and / or vapors may be present at the oxygen sensor location (possibly due to condensate being discharged from an intercooler upstream of the oxygen sensor), then control may limit the oxygen sensor EGR estimate to within the boundary of the DP sensor tolerance interval, as previously discussed. Control may determine that water droplets and / or vapor may be present at the oxygen sensor location if condensate is being discharged from a charge air cooler located upstream of the oxygen sensor.

[0075] In other embodiments, the accuracy values ​​assigned to the DP and oxygen sensors may be different integer values ​​than those described in block diagram 500 (e.g., 0, 1, 2, and 3). Thus, the arbitration rules may be assigned different corresponding DP and oxygen sensor accuracy values ​​than those described in block diagram 500. In still other embodiments, other arbitration rules may be present besides those mentioned in block diagram 500. As an example, the final EGR fraction estimate may be a weighted average of the DP and oxygen sensor EGR fraction estimate based on the accuracy of the DP and oxygen sensors. Thus, the final EGR fraction estimate may be more heavily weighted toward a more accurate sensor EGR fraction estimate.For example, if the accuracy value of the DP sensor is higher than that of the oxygen sensor, the final EGR fraction estimate may be more similar to the EGR fraction estimate from the DP sensor than that from the oxygen sensor.

[0076] Thus, block diagram 500 may include conditions (e.g., rules) for determining how to use the signal outputs from an oxygen and DP sensor to calculate a fraction of EGR gases in the intake air, depending on the accuracy of the sensors under various engine operating conditions. Specifically, the controller may use either the DP sensor EGR fraction estimate, the oxygen sensor EGR fraction estimate, or the oxygen sensor EGR fraction estimate constrained within the DP tolerance interval to make a final estimate of the fraction of EGR gases in the intake air.

[0077] In this way, a method for an engine may include adjusting engine operation based on a final estimate of the gas flow parameters, wherein the final estimate of the gas flow parameters is based on a first gas flow parameter estimated with a first sensor, a second gas flow parameter estimated with a second sensor positioned in a gas passage of the engine away from the first sensor, and accuracy values ​​of both the first and second gas flow parameters.The final estimate of the gas flow parameters is a final estimate of the exhaust gas recirculation (EGR) flow, wherein adjusting engine operation comprises adjusting an EGR valve based on the final EGR flow estimate, wherein the final EGR flow estimate is based on a first EGR flow estimated using a differential pressure sensor across the EGR valve, a second EGR flow estimated using an intake oxygen sensor, and accuracy values ​​of both the first and second EGR flows. The accuracy values ​​may be based on engine operating conditions during the estimation of the first EGR flow and the second EGR flow, wherein the accuracy values ​​are integer values ​​between zero and three. Further, the method may comprise assigning a first accuracy value to the first EGR flow based on compressor surge, a position of a compressor bypass valve, and a differential pressure output by the differential pressure sensor.The method may further include assigning a second base accuracy value to the second EGR flow based on whether an idle adjustment and pressure adjustment routine has been performed to correct an output of the intake oxygen sensor. The method may further include modifying the second base accuracy value to determine a second final accuracy value of the second EGR flow based on purge and crankcase ventilation (PCV) flow past the intake oxygen sensor. The method may further include adjusting the first EGR flow and a first accuracy value of the first EGR flow by a time delay prior to determining the final EGR flow estimate, wherein the time delay is based on a spatial delay that accounts for a volume between the differential pressure sensor and the intake oxygen sensor.The final EGR flow estimate may further be based on an estimation tolerance of estimating the first EGR flow with the differential pressure sensor, wherein the estimation tolerance is based on a differential pressure measured with the differential pressure sensor and / or a valve lift of the EGR valve. Furthermore, the method may include determining the final EGR flow estimate based on the second EGR flow limited by the first EGR flow and the estimation tolerance when a second accuracy value of the second EGR flow is a first value, or the second accuracy value is a second value, or the second value is greater than the first value and water droplets are possible at the intake oxygen sensor, or when the second accuracy value is a third value, the third value is lower than the first value, and a first accuracy value of the first EGR flow is lower than the second value.The method may further include determining the final EGR flow estimate based on the second EGR flow and not on the first EGR flow when a second accuracy value of the second EGR flow is at an upper threshold and water droplets are not expected at the intake oxygen sensor. The method may further include determining the final EGR flow estimate based on the first EGR flow or the second EGR flow limited by the first EGR flow when a first accuracy value of the first EGR flow is at an upper threshold and a second accuracy value of the second EGR flow is a second value, the second value being less than the upper threshold.

[0078] In this way, a method may include estimating a first exhaust gas recirculation (EGR) flow with a differential pressure sensor across an EGR valve and a second EGR flow with an intake oxygen sensor, assigning a first accuracy value to the first EGR flow and a second accuracy value to the second EGR flow based on engine operating conditions and sensor conditions, and adjusting the EGR valve based on a final EGR flow estimate, wherein the final EGR flow estimate is based on the first EGR flow, the second EGR flow, the first accuracy value, and the second accuracy value. The first accuracy value may decrease when a differential pressure measured by the differential pressure sensor is below a threshold, during a compressor surge event, when a compressor bypass valve opens, and when a flag indicating a differential pressure sensor fault is set.The second accuracy value may decrease if adjustment routines to correct an output of the intake oxygen sensor have not been performed, if purge flow to the intake oxygen sensor increases, and if crankcase ventilation (PCV) flow to the intake oxygen sensor increases. The method may further include determining a tolerance interval of the first EGR flow, wherein the tolerance interval is based on a differential pressure measured by the differential pressure sensor and a valve lift of the EGR valve. The method may further include combining the first EGR flow and the second EGR flow into a final EGR flow estimate, wherein the combining is based on the first accuracy value, the second accuracy value, and the estimation tolerance.The method may further include limiting the second EGR flow to within the tolerance interval of the first EGR flow and determining the final EGR flow estimate based on the limited second EGR flow when the second accuracy value is less than the first value and / or the second accuracy value is the first value while water droplets are possible at the intake oxygen sensor. The method may further include determining the final EGR flow estimate as the second EGR flow and not the first EGR flow when the second accuracy value is a first value and water droplets are not possible at the intake oxygen sensor.

[0079] In this way, a system may include a turbocharger having an intake compressor and an exhaust turbine, a low-pressure exhaust gas recirculation (low-pressure EGR) passage coupled between an exhaust passage downstream of the exhaust turbine and the intake passage upstream of the intake compressor, the low-pressure EGR passage including an EGR valve and a differential pressure (DP) sensor for measuring EGR flow, an intake oxygen sensor disposed in an intake of the engine downstream of the low-pressure EGR passage, and a controller having computer-readable instructions for determining a final EGR flow estimate based on a first EGR flow estimate based on an output of the DP sensor, a second EGR flow estimate based on an output of the intake oxygen sensor, a first accuracy value of the first EGR flow estimate, and a second accuracy value of the second EGR flow estimate.The first accuracy value may be an integer value based on compressor surge and / or a position of a compressor bypass valve and / or a differential pressure output from the differential pressure sensor. The second accuracy value may be an integer value based on whether a sensor fault is present and / or an idle trim and pressure trim routine has been performed to correct an intake oxygen sensor output, and / or a purge flow rate past the intake oxygen sensor and / or a PCV flow rate past the intake oxygen sensor.

[0080] In this way, a method may include estimating a fraction of EGR gases in an engine's intake system based on outputs from both an intake oxygen sensor and a DPOV system including a delta pressure (DP) sensor. Both the DP sensor and the oxygen sensor may be used to provide separate estimates of the EGR fraction in the intake air of the intake system. Depending on the engine operating conditions, the accuracy of the outputs from each of the sensors may be evaluated. The accuracy of the oxygen sensor's outputs may be based on whether the oxygen sensor has performed an idle trim or pressure trim routine and / or whether purge and / or PCV gases are bypassing the oxygen sensor. The accuracy of the DP sensor may be determined based on whether pumping is active, a CBV is open or about to open, and a pressure differential across an EGR valve.The output signals reflecting the purge and PCV flows, as well as signals from the DP sensor, can be time-aligned to the position of the oxygen sensor to account for the time required for gases to flow from the PCV passage, purge passage, and DPOV system to the oxygen sensor positioned downstream. These output signals can be filtered to represent axial diffusion and modified by a comparator using calibratable thresholds to obtain final integer state values, as may be required by the arbitration rules, and to reduce overestimation of sensor accuracies.

[0081] Depending on the accuracy of the oxygen and DP sensors, the fraction of EGR gases in the intake air can be estimated differently. The oxygen and DP sensors can each be assigned a value from 0 to 3. If the accuracy of either the DP sensor or the oxygen sensor is 0, then the controller cannot perform an EGR estimate. If the oxygen sensor accuracy is 1 and the DP sensor accuracy is 3, then the controller can use exclusively the EGR fraction estimate from the DP sensor for the final EGR fraction estimate. If the oxygen sensor accuracy is 1 and the DP sensor accuracy is 1 or 2, or if the oxygen sensor accuracy is 2 and the DP sensor accuracy is greater than 0, the controller can limit the oxygen sensor EGR fraction estimate to within the limits of the DP sensor tolerance interval.If the oxygen sensor accuracy is 3 and the DP sensor accuracy is greater than 0, the controller may use the oxygen sensor EGR fraction estimate for the final estimate of the EGR fraction in the intake air. Thus, under certain engine operating conditions, the oxygen sensor may be used exclusively to estimate the EGR fraction. Under other engine operating conditions, the DP sensor may be used exclusively to estimate the EGR fraction. Under still other engine operating conditions, signal outputs from the oxygen sensor and the DP sensor, along with a DP sensor tolerance, may be included in the final EGR fraction estimate.

[0082] In this way, a technical effect of determining a more accurate EGR flow estimate based on the outputs and accuracies of both an oxygen sensor and a delta pressure sensor is achieved. As a result, EGR flow control via an EGR valve can be more accurate. By determining the accuracy of the outputs of both sensors based on engine operating conditions, a more accurate EGR flow estimate can be obtained by using outputs from the more accurate sensor for the EGR flow estimate. Furthermore, under some conditions, where the accuracies of the sensors may be the same or similar, a combination of the two sensor outputs can be included to provide a more accurate estimate of EGR flow in the intake system.Thus, under a wider range of engine operating conditions, not only can the overall accuracy of the EGR flow be increased, but the accuracy of the EGR flow estimation can also be maintained.

[0083] In another embodiment, a method comprises: estimating a first exhaust gas recirculation (EGR) flow with a differential pressure sensor across an EGR valve and a second EGR flow with an intake oxygen sensor, under a first condition, adjusting EGR based on the first EGR flow estimate and not the second EGR flow estimate, under a second condition, adjusting EGR based on the second EGR flow estimate and not the first EGR flow estimate, and under a third condition, combining the first EGR flow estimate and the second EGR flow estimate into a single, combined EGR estimate and adjusting EGR based on the combined EGR estimate.

[0084] It should be noted that the exemplary control and estimation routines included herein may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and may be performed by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The particular routines described herein may represent one or more of a number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various illustrated acts, operations, and / or functions may be performed in the order illustrated, in parallel, or in some cases, omitted.Likewise, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described acts, operations, and / or functions may graphically represent code to be programmed into the non-volatile memory of the computer-readable storage medium in the engine control system, wherein the described acts are performed by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.

[0085] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the above technology may be applied to V-6, I-4, I-6, V-12, horizontally opposed four, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or characteristics disclosed herein.

[0086] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims should be construed as encompassing the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether their scope is broader, narrower, the same, or different with respect to the original claims, are also considered to be included within the subject matter of the present disclosure.

Claims

[1] A method for an engine, comprising: Adjusting engine operation based on a final estimate of the gas flow parameters, wherein the final estimate of the gas flow parameters is based on a first gas flow parameter estimated with a first sensor, a second gas flow parameter estimated with a second sensor positioned in a gas channel of the engine at a distance from the first sensor, and accuracy values ​​of both the first and the second gas flow parameters, wherein the final estimate of the gas flow parameters is a final estimate of the exhaust gas recirculation (EGR) flow, and wherein adjusting the engine operation comprises adjusting an EGR valve (121) based on the final EGR flow estimate, and wherein the final EGR flow estimate is based on a first EGR flow estimated with a differential pressure sensor (125) across the EGR valve (121),a second EGR flow estimated with an intake oxygen sensor (168) and accuracy values ​​of both the first and second EGR flows., [2] The method of claim 1, wherein the accuracy values ​​are based on engine operating conditions during the estimation of the first EGR flow and the second EGR flow, and wherein the accuracy values ​​are integer values ​​between zero and three. [3] The method of claim 1, further comprising assigning a first accuracy value to the first EGR flow based on compressor surge, a position of a compressor bypass valve (152, 155), and a differential pressure output by the differential pressure sensor (125), respectively. [4] The method of claim 1, further comprising assigning a second base accuracy value to the second EGR flow based on whether an idle adjustment and pressure adjustment routine has been performed to correct an output of the intake oxygen sensor (168). [5] The method of claim 4, further comprising modifying the second base accuracy value to determine a second final accuracy value of the second EGR flow based on purge and crankcase ventilation (PCV) flow past the intake oxygen sensor (168). [6] The method of claim 1, further comprising adjusting the first EGR flow and a first accuracy value of the first EGR flow by a time delay prior to determining the final EGR flow estimate, the time delay being based on a spatial delay that accounts for a flow and a volume between the differential pressure sensor (125) and the intake oxygen sensor (168). [7] The method of claim 1, wherein the final EGR flow estimate is further based on an estimation tolerance of estimating the first EGR flow with the differential pressure sensor (125), the estimation tolerance being based on a differential pressure measured with the differential pressure sensor (125) and / or a valve lift of the EGR valve (121). [8] The method of claim 7, further comprising determining the final EGR flow estimate based on the second EGR flow limited by the first EGR flow and the estimation tolerance when a second accuracy value of the second EGR flow is a first value, or the second accuracy value is a second value, or the second value is greater than the first value and water droplets are possible at the intake oxygen sensor (168), or when the second accuracy value is a third value, the third value is lower than the first value, and a first accuracy value of the first EGR flow is lower than the second value. [9] The method of claim 1, further comprising determining the final EGR flow estimate based on the second EGR flow and not the first EGR flow when a second accuracy value of the second EGR flow is at an upper threshold and water droplets are not expected at the intake oxygen sensor (168). [10] The method of claim 1, further comprising determining the final EGR flow estimate based on the first EGR flow or the second EGR flow limited by the first EGR flow when a first accuracy value of the first EGR flow is at an upper threshold and a second accuracy value of the second EGR flow is a second value, the second value being less than the upper threshold. [11] A method comprising: Estimating a first exhaust gas recirculation (EGR) flow with a differential pressure sensor (125) across an EGR valve (121) and a second EGR flow with an intake oxygen sensor (168); Assigning a first accuracy value to the first EGR flow and a second accuracy value to the second EGR flow based on Engine operating conditions and sensor conditions; and Adjusting the EGR valve (121) based on a final EGR flow estimate, wherein the final EGR flow estimate is based on the first EGR flow, the second EGR flow, the first accuracy value, and the second accuracy value. [12] The method of claim 11, wherein the first accuracy value decreases when a differential pressure measured by the differential pressure sensor (125) is below a threshold value, during a compressor surge event, when a compressor bypass valve (152, 155) opens, and when a flag indicating a fault of the differential pressure sensor (125) is set. [13] The method of claim 11, wherein the second accuracy value decreases when adjustment routines to correct an output of the intake oxygen sensor (168) have not been performed, when purge flow to the intake oxygen sensor (168) increases, and when crankcase ventilation (PCV) flow to the intake oxygen sensor (168) increases. [14] The method of claim 11, further comprising determining a tolerance interval of the first EGR flow, wherein the tolerance interval is based on a differential pressure measured by the differential pressure sensor (125) and a valve lift of the EGR valve (121). [15] The method of claim 14, further comprising combining the first EGR flow and the second EGR flow into a final EGR flow estimate, wherein the combining is based on the first accuracy value, the second accuracy value, and the estimation tolerance. [16] The method of claim 14, further comprising limiting the second EGR flow to within the tolerance interval of the first EGR flow and determining the final EGR flow estimate based on the limited second EGR flow when the second accuracy value is less than the first value and / or the second accuracy value is the first value while water droplets are possible at the intake oxygen sensor (168), and further comprising determining the final EGR flow estimate as the second EGR flow and not the first EGR flow when the second accuracy value is a first value and water droplets are not possible at the intake oxygen sensor (168). [17] System comprising: a turbocharger having an intake compressor and an exhaust turbine (124, 134); a low-pressure exhaust gas recirculation (LOW-PRESSURE EGR) passage coupled between an outlet passage (170, 180) downstream of the exhaust turbine (124, 134) and the inlet passage upstream of the intake compressor, the low-pressure EGR passage including an EGR valve (121) and a differential pressure (DP) sensor (125) for measuring EGR flow; an intake oxygen sensor (168) disposed in an intake of the engine downstream of the low-pressure EGR passage; and a controller with computer-readable instructions for: Determining a final EGR flow estimate based on a first EGR flow estimate based on an output of the DP sensor (125), a second EGR flow estimate based on an output of the intake oxygen sensor (168), a first accuracy value of the first EGR flow estimate, and a second accuracy value of the second EGR flow estimate. [18] The system of claim 17, wherein the first accuracy value is an integer value based on compressor surge and / or a position of a compressor bypass valve (152, 155) and / or a differential pressure output by the differential pressure sensor (125). [19] The system of claim 17, wherein the second accuracy value is an integer value based on whether an idle adjustment and pressure adjustment routine has been performed to correct an output of the intake oxygen sensor (168), and / or based on a purge flow amount past the intake oxygen sensor (168) and / or a PCV flow amount past the intake oxygen sensor (168).

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