METHOD AND SYSTEMS FOR AN EGR SYSTEM

Abstract

Procedures and systems for an exhaust gas recirculation (EGR) system are provided. One example procedure involves determining a current and a historical EGR valve offset and comparing the current and historical EGR valve offsets to determine the presence of an EGR leak.

Description

Field of TechnologyThe present description relates generally to diagnostic routines for an EGR system of a vehicle.General State of the ArtEngine systems may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system, a process referred to as exhaust gas recirculation (EGR), to reduce emissions. An EGR valve may be controlled to achieve a desired intake air dilution for a given engine operating condition. Typically, the amount of low pressure EGR (LP-EGR) and / or high pressure EGR (HP-EGR) directed through the EGR system may be measured and adjusted based on engine speed, engine temperature, and load during engine operation to maintain a desired combustion stability of the engine while providing emissions and fuel efficiency benefits. EGR effectively cools the temperature of the combustion chamber, thereby reducing the formation of NO x.In some existing implementations of EGR systems, EGR output may be measured across a fixed orifice and a pressure drop across the orifice sensed. The pressure drop of the orifice may be measured by a differential pressure sensor or two discrete pressure sensors, one on each side of the orifice. Measurement of the EGR flow of the orifice may be possible by characterizing a relationship between the flow and the pressure drop of the orifice. The relationship may be stored in memory and retrieved during future EGR flow conditions to adjust the measured EGR flow rate. The measured EGR flow rate may then be used by a controller to adjust an engine air flow, a combustion rate of the in-cylinder fuel-air mixture, and an engine output torque, and used as a feedback signal in a closed loop EGR flow control configuration, where the EGR flow is modulated by a valve separate from the fixed orifice.Other examples of EGR systems include measuring EGR flow provided by measuring or estimating a pressure drop of an EGR control valve. An EGR control valve measurement may characterize a relationship between flow and orifice pressure drop. The value may be stored and used to set conditions similar to those described above. Measurements of EGR flow in any of these configurations may be dependent on the accuracy of the pressure sensors and / or a position sensor of the EGR valve. While a diagnostic for the pressure sensors is present, a diagnostic for the position sensor remains desired. Further, since a duty cycle of the EGR valve may be based on feedback from the position sensor, recalibration of the position sensor based on the diagnostic may be desired.SummaryIn one example, the issues described above may be addressed by a method of operating an exhaust gas recirculation (EGR) system including applying a cooler pressure model to calculate a cooler pressure drop as a function of engine operating parameters with an EGR flow, and diagnosing an EGR pressure (EGRD) sensor based on a comparison of an EGRD sensor measurement value with a manifold air pressure (MAP) sensor measurement value and the cooler pressure drop. In this way, diagnosis of an EGRD sensor on the warm side may be performed.As one example, the EGR system may include multiple diagnostic routines for determining a state of the EGRD sensor. The routines may be executed separately or in tandem to check the state of the EGRD sensor. As such, mass flow of EGR to an engine may be equal to a requested amount, which may increase engine performance and decrease emissions.It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are described in more detail in the detailed description. It is not intended to identify key or key features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any of the disadvantages listed above or in any part of this disclosure.Brief Description of the DrawingsThe advantages described herein will become more fully apparent from reading an example of an embodiment referred to herein as the detailed description when taken alone or with reference to the drawings in which: FIG. 1 illustrates a schematic of an engine included in a hybrid vehicle; FIG. 2 illustrates a first routine for diagnosing an exhaust gas recirculation pressure (EGRD) sensor according to an embodiment of the present disclosure; FIG. 3 illustrates a second routine for diagnosing an exhaust gas recirculation pressure (EGRD) sensor according to an embodiment of the present disclosure; FIG. 4 illustrates a third routine for diagnosing an exhaust gas recirculation pressure (EGRD) sensor according to an embodiment of the present disclosure; FIG. 5 illustrates a fourth routine for diagnosing an exhaust gas recirculation pressure (EGRD) sensor according to an embodiment of the present disclosure; FIG. 6 illustrates a method for determining whether EGR valve displacement occurs with misfire, according to an embodiment of the present disclosure; FIG. 7 illustrates a method for determining a historical EGR valve displacement according to an embodiment of the present disclosure; FIG. 8 illustrates an engine operating sequence for comparing the EGR valve offset to the historical offset and determining if maintenance is desired, according to an embodiment of the present disclosure.Detailed DescriptionThe following description relates to systems and methods for an exhaust gas recirculation (EGR) system. In one example, the EGR system is configured to direct exhaust gas back to an engine, as shown in FIG. 1. The EGR system may include a valve and one or more sensors for dosing an EGR flow up to a certain amount based on operating conditions. Routines for diagnosing conditions of the one or more sensors are illustrated in FIGS. 2-5. Routines for determining a valve offset of the EGR system are shown in FIGS. 6-7. FIG. 8 illustrates an operating sequence graphically illustrating a current valve offset being compared to a historical EGR valve offset and determining whether the EGR valve offset results in an undesirable amount of EGR leakage.FIG. 1 illustrates an example configuration with relative positioning of the various components. When shown as being directly contacting or directly coupled to each other, such elements may be referred to as being directly contacting or directly coupled to each other, respectively, in at least one example. Similarly, elements shown contiguous or adjacent to each other may be contiguous or adjacent to each other, at least in one example. As an example, components that are in face sharing contact with each other may be referred to as face sharing contact. As another example, elements positioned apart from each other with only a space therebetween and no other components may be so referred to in at least one example. As yet another example, elements shown above / below each other, on opposite sides of each other, or left / right of each other may be referred to relative to each other. Further, as shown in the figures, a top element or point of an element may be referred to as a "top" of the component and a bottom element or point of the element may be referred to as a "bottom" of the component in at least one example. As used herein, top / bottom, top / bottom, above / below relative to a vertical axis of the figures may be and may be used to describe the positioning of elements of the figures relative to each other. Thus, in one example, elements shown above other elements are positioned vertically above the other elements. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as circular, straight, planar, curved, rounded, beveled, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another in at least one example. Still further, an element shown within another element or outside another element may be referred to as such in an example. It should be appreciated that one or more components referred to as "substantially similar and / or identical" differ from one another depending on manufacturing tolerances (e.g., within 1-5% deviation).FIG. 1 shows a schematic illustration of a hybrid vehicle system 6 that may draw motive power from an engine system 8 and / or from an on-board energy storage device. An energy conversion device, such as a generator, may be operated to absorb energy from vehicle motion and / or engine operation and then convert the absorbed energy to a form of energy suitable for storage by the energy storage device.The engine system 8 may include an engine 10 having a plurality of cylinders 30. The engine 10 includes an engine inlet 23 and an engine outlet 25. the engine inlet 23 includes an air intake throttle 62 fluidly coupled to the engine intake manifold 44 via an intake passage 42. Air may enter intake passage 42 via air filter 52. Engine intake manifold 44 may further include a manifold absolute pressure (MAP) sensor 95. The engine outlet 25 includes an exhaust manifold 48 leading to an exhaust passage 35 that directs exhaust gas to the atmosphere. The engine outlet 25 may include at least one emission control device 70 mounted at a close-coupled position or at a remote underbody position. The emission control device 70 may include a three-way catalyst, a lean NOx trap, a particulate filter, an oxidation catalyst, etc. It should be appreciated that other components may be included in the engine, such as a variety of valves and sensors as further set forth herein. In some embodiments where engine system 8 is a boosted engine system, the engine system may further include a boosting device, such as a turbocharger (not shown).In the example of the present disclosure, the emission control device 70 is a particulate filter 70. In another example, the particulate filter 70 is a diesel particulate filter.Engine system 8 further includes a turbocharger having a compressor 82 and a turbine 84. The compressor 82 and the turbine 84 are mechanically coupled via a shaft 86. Turbine 84 may be driven via exhaust gases flowing through exhaust passage 35. The exhaust gases may rotate a rotor of the turbine 84, which may rotate the shaft 86, resulting in rotation of a rotor of the compressor 82. The compressor 82 is configured to receive and compress intake air.The engine system 8 further includes an exhaust gas recirculation (EGR) system 130. In the example of FIG. 1, the EGR system 130 is a high pressure EGR system in which exhaust gases are drawn from a location of the engine outlet 25 that is upstream of the turbine 84. The EGR system 130 includes an EGR valve 134 disposed upstream of a heat exchanger 138 relative to a direction of exhaust flow in an EGR passage 132.The EGR system 130 further includes a first pressure sensor 135, referred to herein as an exhaust pressure (EXP) sensor 135, a second pressure sensor 136, referred to herein as an EGR pressure (EGRD) sensor 136, and a temperature sensor 139. Relative to an exhaust flow direction, the EXP sensor 135 may be disposed upstream of the EGR valve 134, and the EGRD sensor 136 may be disposed downstream of the EGR valve. The temperature sensor 139 may be disposed downstream of the heat exchanger 138. Each of the EXP sensor 135, the EGRD sensor 136, and the temperature sensor 139 may be configured to provide feedback to the controller 12. As illustrated, the EGR system 130 is a high pressure EGR system that does not include a fixed orifice differential pressure sensor. In one example, the EGR system 130 is a Delta Pressure Over Valve (DPOV) EGR system 130, the differential pressure determined via feedback from the EXP sensor 135 and the EGRD sensor 136.An EGR valve position sensor 137 may be configured to provide feedback to the controller 12 regarding a position of the EGR valve 134. In some examples, an accuracy of the EGR valve position sensor 137 and / or the EGRD sensor 136 may deteriorate over time. This may result in EGR flow rates differing from a requested amount, which may reduce engine performance. Included herein are routines for diagnosing a condition of the EGRD sensor 136.In one example, the heat exchanger 138 may be a liquid-to-liquid or an air-to-liquid cooler. The heat exchanger 138 may be configured to receive coolant from a cooling system of the hybrid vehicle 6, such as an engine cooling system or other similar cooling system. The heat exchanger 138 (interchangeably referred to herein as a cooler) is disposed downstream of the EGRD sensor 136 relative to a direction of EGR flow. In one example, the EGR system 130 including the EGR valve 134 upstream of the heat exchanger 138 is a warm side configuration of the EGR system.Additionally or alternatively, the heat exchanger 138 may comprise a cooling system that is separate from another cooling system of the hybrid vehicle 6. In some examples, a bypass passage may be included in the EGR system 130, the bypass passage configured to flow pressurized exhaust gases around the heat exchanger 138 under conditions where cooling may not be desired. In one example, cooling may not be desired during conditions where an engine temperature is lower than a desired temperature, such as during a cold start.In the example of FIG. 1, the hybrid vehicle 6 further includes a low pressure (LP) EGR passage 142. The LP EGR passage 142 is configured to redirect exhaust gases from downstream of the turbine 84 to a portion of the intake passage 42 upstream of the compressor 82. Additionally or alternatively, in some examples, the hybrid vehicle 6 may be configured without the LP-EGR passage 142 without departing from the scope of the present disclosure.The hybrid vehicle 6 may further include a control system 14. As shown, the control system 14 receives information from a plurality of sensors 16 (various examples of which are described herein) and sends control signals to a plurality of actuators 81 (various examples of which are described herein). As one example, sensors 16 may include an exhaust gas sensor 126 located upstream of the emission control device, a temperature sensor 128, and a pressure sensor 129. The sensors 16 may further include an air pressure (BP) sensor 98 (e.g., a barometer). Other sensors, such as additional pressure, temperature, air-fuel ratio, and composition sensors, may be coupled to various locations in the vehicle system 6. As another example, the actuators may include the throttle 62.The controller 12 may be configured as a conventional microcomputer including a microprocessor unit, input / output ports, read only memories, random access memories, keep alive memories, a controller area network (CAN) bus, etc. The controller 12 may be configured as a powertrain control module (PCM). For additional energy efficiency, control may be switched between sleep and wake-up modes. The controller 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 an instruction or code programmed therein corresponding to one or more routines.In some examples, the hybrid vehicle 6 includes a plurality of torque sources available to one or more vehicle wheels 59. In other examples, the vehicle 6 is a conventional vehicle with only one engine or an electric vehicle with only one (one) electric machine(s). In the example shown, the vehicle 6 includes an engine 10 and the electric machine 51. the electric machine 51 may be an electric motor or a motor / generator. A crankshaft of engine 10 and electric machine 51 may be connected to vehicle wheels 59 via transmission 54 when one or more clutches 56 are engaged. In the depicted example, a first clutch 56 is provided between a crankshaft and the electric machine 51, and a second clutch 56 is provided between the electric machine 51 and the transmission 54. The controller 12 may send a signal to an actuator of each clutch 56 to engage or disengage the clutch, to connect or disconnect the crankshaft to and from the electric machine 51 and the components connected thereto, and / or to connect or disconnect the electric machine 51 to and from the transmission 54 and the components connected thereto. The transmission 54 may be a manual transmission, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle.The electric machine 51 receives electrical power from a traction battery 61 to provide torque to vehicle wheels 59. The electric machine 51 can also be operated as a generator in order to provide electrical power for charging the battery 61, for example during a braking process.Referring now to FIG. 2, a method 200 for diagnosing an EGRD sensor of an EGR system via a first diagnostic routine is shown therein. Instructions for carrying out method 200 and the remaining methods included herein may be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to FIG. 1. The controller may employ engine actuators of the engine system to adjust engine operation according to methods described below.In one example, method 200 and the remaining methods included herein may be used in combination with the components illustrated in FIG. 1. The diagnosis of the EGRD 136 may be performed via, for example, the methods described herein. The diagnostic of the routines of the methods included herein may further include the other sensors and actuators of the EGR system and vehicle system of FIG. 1, including the MAP sensor 95, the EXP sensor 135, the temperature sensor 139, and the EGR valve 134.Method 200 begins at 202, which includes monitoring a radiator pressure drop at different operating points. The radiator pressure drop (e.g., a pressure difference across the radiator) may be determined based on feedback from a pressure sensor upstream of the radiator (e.g., the EGRD sensor) and a pressure sensor downstream of the radiator (e.g., the MAP sensor 95). Additionally or alternatively, the radiator pressure drop may be determined based on a coolant temperature in the radiator and a temperature of EGR exiting the radiator. Operating points where the radiator pressure drop includes two or more of an idle load, a low load, a high load, an average load between the low and high loads, a rate of change of speed of the vehicle, a vehicle tow condition, a coast-down event, and other similar operating parameters.A cooler pressure model may be used to estimate the cooler pressure drop at the different operating points based on the empirically collected data. The radiator pressure model may estimate radiator fouling over time based on the collected data.At 204, method 200 may include mapping the cooler pressure drop. The radiator pressure drop may be stored in a multiple input look-up table in a memory of the controller. The inputs may include the different operating points, where the output may include the radiator pressure drop.At 206, method 200 may include sensing a pressure between the EGR valve and the intake. In one example, pressure may be sensed by the EGRD sensor located between the EGR valve and the radiator.At 208, method 200 may include determining if the EGRD sensor reading is equal to a threshold. In one example, the threshold is equal to a sum of the MAP and the radiator pressure drop. In some examples, additionally or alternatively, the EGRD sensor reading may be compared to a range based on the threshold. For example, the range may be based on ±5% of the threshold. As discussed above, the radiator pressure drop is monitored at different operating points. Here, the threshold is a dynamic value that changes based on a current operating point of the vehicle.If the EGRD sensor measurement is equal to or within the range of the threshold, then at 210, method 200 may include determining that the EGRD sensor is not degraded. Herein, estimates of EGR flow based on feedback from the EGRD sensor may be accurate and the feedback of the EGRD sensor may not be modified.If the EGRD sensor measurement is not equal to or outside the range of the threshold, then at 212, method 200 may include determining that the EGRD sensor is degraded.At 214, method 200 may include turning on a warning light.At 216, method 200 may include applying a correction value. The correction value may be applied to the EGRD sensor reading, which may provide a more accurate estimate of the EGR flow.In some examples, additionally or alternatively, if the EGRD sensor reading is outside the range by a certain value (e.g., 10% outside a lower or upper limit of the range), then turning on the indicator light may further include requesting maintenance and / or replacement of the EGRD sensor.Referring now to FIG. 3, a method 300 for diagnosing the EGRD sensor when the EGR valve is closed is shown therein. At 302, method 300 may include determining if the EGR valve is closed. The EGR valve may be determined to be closed based on feedback from the MAP sensor, the EGRD sensor, and the like. Additionally or alternatively, the EGR valve may be closed based on an engine operating condition where EGR is not requested during the engine operating condition.If the EGR valve is not closed, then the diagnostic of method 400 of FIG. 4 may be carried out.If the EGR valve is closed, then at 304, method 300 may include receiving a MAP sensor feedback. The MAP sensor may provide an indication of manifold pressure.At 306, method 300 may include receiving EGRD feedback.At 308, method 300 may include determining if the MAP sensor feedback is equal to the EGRD feedback. When the EGR valve is closed, the measurements of the MAP sensor and the EGRD sensor may be the same.Additionally or alternatively, the MAP sensor reading and the EGRD sensor reading may be compared to the mapped radiator pressure drop. For example, the radiator may be soiled or include a restriction therein that may affect the comparison between the MAP sensor reading and the EGRD sensor reading. In this regard, in some embodiments, the cooler pressure model may be used during the diagnostic routine of method 300.If the MAP sensor feedback is equal to the EGRD sensor feedback, then at 310, method 300 may include determining that the EGRD sensor is not degraded. Adjustments to EGRD sensor feedback may not be initiated.If the MAP sensor feedback is not equal to the EGRD sensor feedback, then at 312, method 300 may include determining that the EGRD sensor is degraded.At 314, method 300 may include turning on a warning light.At 316, method 300 may include applying a correction value. The correction value may be applied to the EGRD sensor reading, which may provide a more accurate estimate of the EGR flow.Referring now to FIG. 4, shown therein is method 400 for diagnosing the EGRD sensor when the EGR valve is open and EGR flows to the engine. Method 400 begins at 402 following a NO at 302 of method 300 of FIG. 3. at 402, method 400 may include receiving a MAP sensor feedback.At 404, method 400 may include receiving EGRD sensor feedback.At 406, method 400 may include determining a calibration factor based on a current speed and load. In one example, the EGRD sensor and MAP sensor readings track each other along a quadratic function. However, at certain speeds and loads, the EGRD sensor reading may deviate from the quadratic function and the MAP sensor reading. The calibration factor may take into account the deviation such that a sum of the calibration factor and the MAP sensor reading is equal to the EGRD sensor reading when the EGRD sensor is not degraded. In one example, the calibration factor is equal to or based on the radiator pressure drop. Additionally or alternatively, the calibration factor may be determined empirically based on monitored deviations of EGRD sensor readings from MAP sensor readings during different engine speeds and loads.At 408, method 400 may include determining if a difference between the MAP and EGRD measurement values is within the calibration factor to zero. In other words, the difference between the MAP and EGRD readings is compared to zero ± the calibration factor.If the difference is equal to or is within the calibration factor to zero, at 410, method 400 may include determining that the EGRD sensor is not degraded. Adjustments to EGRD sensor feedback may not be initiated.If the difference is not within the calibration factor to zero, then at 412, method 400 may include determining that the EGRD sensor is degraded.At 414, method 400 may include turning on a warning light.At 416, method 400 may include applying a correction value. The correction value may be applied to the EGRD sensor reading, which may provide a more accurate estimate of the EGR flow.Referring now to FIG. 5, a method 500 for diagnosing the EGRD sensor when the EGR valve is open beyond a threshold position is shown therein. Method 500 begins at 502, which includes determining if the EGR valve is open beyond a threshold position. In one example, the threshold position may correspond to a position where the EGR valve is at least 50%, or at least 70%, or at least 80%, or at least 90% open. Herein, the threshold position may include the EGR valve being closed to a fully open position instead of a fully closed position.If the EGR valve is not open beyond the threshold position, then at 504, method 500 may include not using the EGRD / EXP pressure ratio to diagnose the EGRD sensor. In one example, the diagnostic routine of method 400 of FIG. 4 may be used when the EGR valve is open but not open beyond the threshold position. If the EGR valve is closed, then the diagnostic routine of method 300 of FIG. 3 may be used to diagnose the EGRD.If the EGR valve is open beyond the threshold position, then at 506, method 500 may include receiving an EXP sensor feedback. The EXP sensor may be positioned upstream of the EGR valve relative to the direction of EGR flow.At 508, method 500 may include receiving EGRD feedback.At 510, method 500 may include determining an EGRD / EXP ratio.At 512, method 500 may include determining if the EGRD / EXP ratio is equal to one. In some examples, additionally or alternatively, it may be determined whether the EGRD / EXP ratio is within a range of 1 (e.g., within 5% of 1).If the EGRD / EXP ratio is 1, then at 514, method 500 may include determining that the EGRD sensor is not degraded. Adjustments to EGRD sensor feedback may not be initiated.If the EGRD / EXP ratio is not equal to 1, then at 516, method 500 may include determining that the EGRD sensor is not degraded.At 518, method 500 may include turning on a warning light.At 520, method 500 may include applying a correction value. The correction value may be applied to the EGRD sensor reading, which may provide a more accurate estimate of the EGR flow.In this way, multiple routines may be used to diagnose accuracy of the feedback provided by the EGRD sensor. The routines may be adjusted relative to each other to check whether a diagnostic of the EGRD sensor is correct. Two or more routines may be executed to determine a validity and / or accuracy of a state of the EGRD sensor. As a result, the EGR mass flow may be closer to a requested value, which may improve combustion efficiency of the engine and reduce emissions.Referring now to FIG. 6, a method 600 for determining EGR valve displacement during one or more drive cycles is shown therein. Method 600 further includes determining if EGR valve offset results in engine misfires.Method 600 begins at 602, which includes determining whether a keep alive memory (KAM) of the controller is reset. In one example, if the KAM reset is active, the memory stored therein may be cleared.If the KAM reset is active, then at 604, method 600 may include not monitoring for EGR leakage through the EGR valve.If the KAM reset is not active, then at 606, method 600 may include determining current operating conditions. The current operating conditions may be operating conditions of a current drive cycle. The current operating conditions may include mass air flow, manifold pressure, engine load, engine speed, EGR flow rate, and air-fuel ratio.At 608, method 600 may include detecting a particular number of valve displacement samples during a current drive cycle. The determined number of valve offset samples may be a fixed number or a dynamic number. The dynamic number may be adjusted based on the current operating conditions, EGR valve positions, and the like. For example, at least one offset sample may be acquired for each EGR valve position used during the current drive cycle. The offset may be determined based on a comparison between a requested EGR flow rate and an actual EGR flow rate. If the actual EGR flow rate is less than the requested EGR flow rate, then the EGR valve offset may be a negative value indicating that less EGR is flowing than requested. If the actual EGR flow rate is greater than the requested EGR flow rate, then the EGR valve offset may be a positive value indicating that more EGR is flowing than requested. The fixed number may be equal to one sample per EGR valve position, two samples per EGR valve position, or so forth. If two samples per position are requested, one sample may be collected on entering the position and another before leaving the position.In one example, additionally or alternatively, the offset may be based at least in part on the cooler pressure model and / or the EGRD / EXP ratio. For example, the amount of offset may be based on the radiator pressure model and the EGRD / EXP ratio. For example, if the EGRD / EXP ratio is equal to 1 during a partially open position of the EGR valve, then there may be an EGR leakage. The commanded EGR position may be adjusted to a more closed position to account for EGR leakage. The commanded EGR position may be adjusted until the EGRD / EXP ratio is equal to a desired value.At 610, method 600 may include determining whether the drive cycle is complete. The drive cycle is completed when the engine is shut down due to an ignition key being turned on or an ignition button being pressed. Additionally or alternatively, the drive cycle may be completed when a start-stop is initiated.If the drive cycle is not complete, then method 600 may continue to monitor operating conditions and detect valve displacement values. If the drive cycle is complete, then at 612, method 600 may include calculating an average offset of the drive cycle. The average offset may include the positive and negative values. Additionally or alternatively, to determine an average EGR leakage through the EGR valve due to the position offset of the EGR valve, the average offset may include only positive values.At 614, method 600 may include comparing the average offset to a historical offset average. The historical offset average may be based on an average offset of offsets that were collected during previous drive cycles. The historical offset is described in more detail with reference to FIG. 7.At 616, method 600 may include determining whether the average offset is less than or equal to the historical offset average. If the average offset is less than or equal to the historical offset average, then at 618, method 600 may include determining that there is no EGR leakage. This allows the diagnosis to be passed. Additionally or alternatively, the historical offset average may be updated based on the average offset determined during the drive cycle of method 600.If the average offset is not less than or equal to (e.g., greater than) the historical offset average, then at 620, method 600 may include detecting a misfire event. In one example, the misfire event may correspond to a time when an EGR valve displacement was detected. Additionally or alternatively, the misfire event may occur at an EGR valve position where an EGR valve displacement has been detected. Engine misfire may include a desired amount of combustion not occurring in at least one engine cylinder. Engine misfire may be detected based on a cylinder pressure, temperature, and / or output being less than an expected corresponding value.At 622, method 600 may include determining if a misfire event is present. If there is no misfire event, then at 624, method 600 may include not indicating EGR leakage through the EGR valve.If a misfire event is present, then at 626, method 600 may include indicating that an EGR leakage is present. In one example, method 600 may include turning on a warning light at 628. Additionally or alternatively, engine operating parameters may be adjusted to account for EGR leakage and the position(s) at which the EGR valve leaks. For example, if the EGR valve leaks, then when the EGR valve is commanded to a fully closed position, adjustments may only occur during engine operating parameters where the EGR valve is commanded to a fully closed position. Additionally or alternatively, if EGR leakage occurs during partially open positions of the EGR valve, a commanded position of the EGR valve may be adjusted to account for the EGR leakage. In one example, a degree of EGR valve opening may be decreased in proportion to a degree of EGR leakage. In the fully closed position including EGR leakage, engine operating conditions may be adjusted, where the adjustments may include increasing fuel delivery and / or a number of fuel injections, increasing a number and / or timing of spark, and the like. Additionally or alternatively, when boost is provided, a cooler may be bypassed to maintain higher boost temperatures.In some examples, additionally or alternatively, if the engine is a multi-fuel engine and the EGR valve leaks, an alternative fuel may be supplied. For example, if the multi-fuel engine is a diesel and hydrogen engine, then hydrogen and diesel may be provided to the engine during conditions where EGR leakage occurs to mitigate a likelihood of misfire.Referring now to FIG. 7, a method 700 for determining a historical average EGR valve offset is shown therein. The method 700 begins at step 702, which includes determining current operating conditions. The current operating conditions may be operating conditions of a current drive cycle. The current operating conditions may include mass air flow, manifold pressure, engine load, engine speed, EGR flow rate, and air-fuel ratio.At 704, method 700 may include monitoring valve displacement during a plurality of conditions during a drive cycle. For example, valve displacement may be monitored during different engine loads, EGR valve positions, vehicle speeds, and the like.At 706, method 700 may include applying a first order low pass filter to detected valve offsets.At 708, method 700 may include storing the filtered valve offset as a learned offset history in the KAM.At 710, method 700 may include computing an average offset history for a given condition. For example, a particular engine speed and a requested EGR valve position may include an average offset history that is different than an average offset history at a different engine speed and requested EGR valve position. The different engine conditions and corresponding EGR valve positions may each include a mean offset plot.At 712, method 700 may include updating the average offset history based on future offset values, such as values acquired during method 600 of FIG. 6. In one example, only offset values less than or equal to the average offset history may be used for updating. Offset values that are greater than the average offset history associated with misfire cannot be used because these offset values correspond to a failed diagnostic test. In one example, if an offset value is greater than the average offset history and there is no misfire, the offset value may be used to update the average offset history. Additionally or alternatively, the offset value that is greater than the average offset history in the absence of misfire may be flagged and / or flagged. If future offset values are below the average offset history, then the flagged offset value may be ignored.Referring now to FIG. 8, a diagram 800 is shown graphically illustrating various conditions for determining whether an EGR leakage is present. Plot 810 illustrates a current average valve offset and the dashed line illustrates a historical average valve offset. Plot 820 illustrates whether a misfire event occurs. Plot 830 illustrates whether a flag is set. The time increases from a left to a right side of the figure.Prior to t 1, multiple mean valve offsets are determined and compared to the historical mean offset. In particular, two average valve offsets are determined over two separate drive cycles. Peaks of plot 810 represent an average valve displacement value and valleys represent conditions where the drive cycle does not occur and no valve displacement is detected.At t 1, an average valve offset is determined. Between t 1 and t 2, the average valve offset is greater than the historical average offset. However, since no misfire is detected, the flag is then not set and the diagnostic is passed. Between t 2 and t 3, more mean valve offsets are determined and the historical mean offset is updated. As illustrated, the historical mean offset may follow the determined mean valve offsetsAt t 3, a misfire and an average valve offset are determined. Between t 3 and t 4, the flag is not activated due to the average valve offset being less than the historical average offset. At t 4, the drive cycle ends.Between t 4 and t 5, more driving cycles occur. Thus, the historical average offset is updated based on the determined average valve offsets.At t 5, a drive cycle begins. Between t 5 and t 6, the average valve offset is greater than the historical average offset in combination with a misfire being detected. At t 6, the flag is activated and the drive cycle ends. After t 6, the flag remains active.The disclosure provides support for a method of operating an exhaust gas recirculation (EGR) system including applying a cooler pressure model to calculate a cooler pressure drop as a function of engine operating parameters with an EGR flow, and diagnosing an EGR pressure (EGRD) sensor based on a comparison of an EGRD sensor measurement with a manifold air pressure (MAP) sensor measurement and the cooler pressure drop. A first example of the method further includes where the EGRD sensor is disposed between an EGR cooler and an EGR valve. A second example of the method, optionally including the first example, further comprises where the EGR cooler is disposed between an inlet and the EGRD sensor. A third example of the method, optionally including one or more of the preceding examples, further includes wherein diagnosing comprises closing an EGR valve. A fourth example of the method, optionally including one or more of the preceding examples, further includes diagnosing the EGRD sensor when the EGR valve is open based on a ratio of the EGRD sensor measurement to an exhaust gas sensor measurement. A fifth example of the method, optionally including one or more of the preceding examples, further includes where, relative to a direction of EGR flow, the exhaust gas sensor is disposed upstream of the EGR valve and the EGRD sensor is disposed downstream of the EGR valve. A sixth example of the method, optionally including one or more of the preceding examples, further includes determining that the EGRD sensor is degraded responsive to the EGRD sensor measurement being different than a sum of the MAP sensor measurement and the radiator pressure drop.The disclosure provides additional support for a system including an exhaust gas recirculation (EGR) system including an EGR valve upstream of an EGR cooler relative to a direction of EGR flow through the EGR system to an intake system, an exhaust gas sensor upstream of the EGR valve, and an EGR pressure (EGRD) sensor between the EGR valve and the EGR cooler, and a controller including computer readable instructions stored on a memory thereof that enable upon execution of the controller, a state of the EGRD sensor based on a sum of a radiator pressure drop and a manifold air pressure (MAP) sensor reading compared to an EGRD sensor reading via a first routine, diagnosing the state of the EGRD sensor based on a comparison of the MAP sensor reading with the EGRD sensor reading via a second routine when the EGR valve is closed, diagnosing the state of the EGRD sensor based on the comparison of the MAP sensor reading with the EGRD sensor reading via a third routine when the EGR valve is open, and diagnosing the state of the EGRD sensor based on a ratio of the EGRD sensor measurement and an exhaust sensor measurement via a fourth routine when the EGR valve is open beyond a threshold position. A first example of the system further includes where the instructions further enable the controller to determine a correction value in response to a diagnostic indicating that the EGRD sensor is degraded. A second example of the system, optionally including the first example, further includes where the instructions further enable the controller to map the radiator pressure drop across a plurality of operating motors of an engine coupled to the intake system. A third example of the system, optionally including one or more of the preceding examples, further includes where the instructions further enable the controller to determine that the EGRD sensor is degraded responsive to the EGRD sensor measurement being different than the sum of the MAP sensor measurement and the cooler pressure drop. A fourth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further enable the controller to determine that the EGRD sensor is degraded responsive to the EGRD sensor measurement being different than the MAP sensor measurement. A fifth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further enable the controller to determine that the EGRD sensor is degraded, the calibrated value based on a quadratic curve, responsive to the EGRD sensor measurement differing from the MAP sensor measurement by a calibrated value during the third routine. A sixth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further enable the controller to determine that the EGRD sensor is degraded responsive to the ratio deviating from a value of 1 during the fourth routine. A seventh example of the system, optionally including one or more of the preceding examples, further includes where the instructions further enable the controller to validate a diagnostic of the EGRD sensor by executing two or more of the first, second, third, and fourth routines.The disclosure further provides support for a method for an exhaust gas recirculation (EGR) system of a vehicle, including mapping a cooler pressure model at a plurality of operating conditions of the vehicle and determining degradation of an EGR pressure (EGRD) sensor based on a comparison of an EGRD sensor measurement to a sum of a manifold air pressure (MAP) sensor measurement and the cooler pressure drop. A first example of the method further includes indicating no degradation of the EGRD sensor in response to the EGRD sensor measurement being equal to the sum of the MAP sensor measurement and the radiator pressure drop. A second example of the method, optionally including the first example, further includes indicating degradation of the EGRD sensor in response to the EGRD sensor measurement being different than the sum of the MAP sensor measurement and the radiator pressure drop. A third example of the method, optionally including one or more of the preceding examples, further includes checking degradation of the EGRD sensor by comparing the EGRD sensor reading to the MAP sensor reading only when an EGR valve is fully closed. A fourth example of the method, optionally including one or more of the preceding examples, further includes checking degradation of the EGRD sensor by comparing a ratio of the EGRD sensor measurement to an exhaust gas sensor measurement to one.The disclosure provides support for a method that includes determining that there is an exhaust gas recirculation (EGR) leak based on a comparison of a current average valve offset with a historical average EGR valve offset. A first example of the method further includes determining that EGR leakage is present based on a presence of engine misfire. A second example of the method, optionally including the first example, further includes where the EGR leakage is responsive to the current average valve offset being greater than the historical average EGR valve offset. A third example of the method, optionally including one or more of the preceding examples, further includes where determining that the EGR leakage is present is not performed when a keep alive memory of a controller is actively reset. A fourth example of the method, optionally including one or more of the preceding examples, further includes where the EGR leakage is not present in response to the current average valve offset being less than or equal to the historical average EGR valve offset. A fifth example of the method, optionally including one or more of the preceding examples, further includes updating the historical average EGR valve offset based on the current average valve offset. A sixth example of the method, optionally including one or more of the preceding examples, further includes where the current average valve offset is based on a difference of the requested EGR flow rate and the actual EGR flow rate. A seventh example of the method, optionally including one or more of the preceding examples, further includes where the current average valve offset is based on a ratio of EGR pressure sensor (EGRD) / exhaust pressure sensor (EXP).The disclosure provides additional support for a system including an exhaust gas recirculation (EGR) system including an EGR valve upstream of an EGR cooler relative to a direction of EGR flow through the EGR system to an intake system, an exhaust gas sensor upstream of the EGR valve, and an EGR pressure (EGRD) sensor between the EGR valve and the EGR cooler, and a controller including computer readable instructions stored on a memory thereof that when executed enable the controller to detect a plurality of EGR valve offsets during a plurality of drive cycles, determine an average historical EGR valve offset based on previous EGR valve offsets, detected during a plurality of previous drive cycles, determining a current average EGR valve offset during a current drive cycle, comparing the current average EGR valve offset to the average historical EGR valve offset, and including an EGR leakage responsive to the current average EGR valve offset being greater than the average historical EGR valve offset in combination with engine misfire being detected. A first example of the system further includes where the average historical EGR valve offset is one of a plurality of average historical EGR valve offsets, each of the plurality of average historical EGR valve offsets based on operating parameters of a previous drive cycle of the plurality of previous drive cycles. A second example of the system, optionally including the first example, further includes where the current average EGR valve offset is determined based on an EGR cooler pressure model. A third example of the system, optionally including one or more of the preceding examples, further includes where the instructions further cause the controller to adjust engine operating parameters responsive to the EGR leakage occurring when the EGR valve is commanded closed. A fourth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further cause the controller to adjust an EGR valve position responsive to the EGR leakage occurring when the EGR valve is in an at least partially open position. A fifth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further cause the controller to determine that the EGR leakage is not present in response to the current average EGR valve offset being less than or equal to the historical average EGR valve offset. A sixth example of the system, optionally including one or more of the preceding examples, further includes where the instructions further cause the controller to determine that the EGR leakage is not present responsive to the engine misfire not being present.The disclosure further provides support for a method for an exhaust gas recirculation (EGR) system, the method including calculating a historical average offset of an EGR valve during a plurality of previous drive cycles, wherein an offset is based on a difference between a commanded position and an actual position of the EGR valve, determining a current average offset of the EGR valve during a current drive cycle, monitoring a presence of an engine misfire, and indicating that an EGR leakage exists responsive to the presence of the engine misfire in combination with the current average offset being greater than the historical average offset. A first example of the method further includes where the offset is further based on one or more of a cooler pressure drop model and a ratio of EGR pressure / exhaust pressure. A second example of the method, optionally including the first example, further includes where, relative to a direction of exhaust flow, EGR pressure is sensed downstream of the EGR valve and exhaust pressure is sensed upstream of the EGR valve. A third example of the method, optionally including one or more of the preceding examples, further includes adjusting operating conditions responsive to indicating that EGR leakage is present, wherein the adjusting comprises adjusting one or more of a commanded position of the EGR valve, adjusting a fuel amount delivered to an engine, adjusting an ignition timing, adjusting a fuel injection timing, adjusting a charge air routing, and adjusting an air mass flow. A fifth example of the method, optionally including one or more of the preceding examples, further includes updating the historical average offset based on the current average offset.It should be appreciated that the example 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-transitory memory and may be executed by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various illustrated acts, operations, and / or functions may be performed in the illustrated sequence, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example 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 repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described acts are performed by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.It should be 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 V6, I4, I6, V12, 4-cylinder boxer, 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, as well as other features, functions, and / or characteristics disclosed herein.As used herein, the term "about" is intended to mean plus or minus five percent of the span, unless otherwise specified.The following claims particularly emphasize specific combinations and sub-combinations considered novel and non-obvious. These claims may refer to "a" element or "a first" element or the equivalent thereof. Such claims are to be understood to include inclusion of one or more such elements and neither require nor exclude two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by altering the present claims or by filing novel claims in this or a related application. Such claims, whether broader, narrower, equal or different in scope from the original claims, are also considered to be included within the subject matter of the present disclosure.According to the present invention, a method includes: determining that there is an exhaust gas recirculation (EGR) leak based on a comparison of a current average valve offset with a historical average EGR valve offset.In one aspect of the invention, the method includes determining that EGR leakage is present based on a presence of engine misfire.In one aspect of the invention, the EGR leakage is responsive to the current average valve offset being greater than the historical average EGR valve offset.In one aspect of the invention, the determination that the EGR leakage is present is not performed when a keep alive memory of a controller is actively reset.In one aspect of the invention, the EGR leakage is not present in response to the current average valve offset being less than or equal to the historical average EGR valve offset.In one aspect of the invention, the method includes updating the historical average EGR valve offset based on the current average valve offset.In one aspect of the invention, the current average valve offset is based on a difference of the requested EGR flow rate and the actual EGR flow rate.In one aspect of the invention, the current average valve offset is based on a ratio of EGR pressure sensor (EGRD) / exhaust pressure sensor (EXP).According to the present invention, there is provided a system comprising: an exhaust gas recirculation (EGR) system comprising an EGR valve upstream of an EGR cooler relative to a direction of EGR flow through the EGR system to an intake system, an exhaust gas sensor upstream of the EGR valve, and an EGR pressure (EGRD) sensor between the EGR valve and the EGR cooler; and a controller comprising computer readable instructions stored on a memory thereof that, when executed, enable: detecting a plurality of EGR valve offsets during a plurality of drive cycles; determining a mean historical EGR valve offset based on previous EGR valve offsets detected during a plurality of previous drive cycles; determining a current mean EGR valve offset during a current drive cycle; comparing the current mean EGR valve offset to the mean historical EGR valve offset; and determining an EGR leakage in response to the current mean EGR valve offset being greater than the mean historical EGR valve offset in combination with detecting an engine misfire.According to one embodiment, the average historical EGR valve offset is one of a plurality of average historical EGR valve offsets, each of the plurality of average historical EGR valve offsets based on operating parameters of a previous drive cycle of the plurality of previous drive cycles.According to one embodiment, the current average EGR valve offset is determined based on an EGR cooler pressure model.According to one embodiment, the instructions further cause the controller to adjust engine operating parameters responsive to the EGR leakage occurring when the EGR valve is commanded closed.According to one embodiment, the instructions further cause the controller to adjust an EGR valve position responsive to the EGR leakage occurring when the EGR valve is in an at least partially open position.According to one embodiment, the instructions further cause the controller to determine that the EGR leakage is not present in response to the current average EGR valve offset being less than or equal to the historical average EGR valve offset.According to one embodiment, the instructions further cause the controller to determine that EGR leakage is not present in response to engine misfire not being present.According to the present invention, a method for an exhaust gas recirculation (EGR) system includes: calculating a historical average offset of an EGR valve during a plurality of previous drive cycles, wherein an offset is based on a difference between a commanded position and an actual position of the EGR valve; determining a current average offset of the EGR valve during a current drive cycle; monitoring a presence of an engine misfire; and indicating that an EGR leakage exists responsive to the presence of the engine misfire in combination with the current average offset being greater than the historical average offset.In one aspect of the invention, the offset is further based on one or more of a cooler pressure drop model and a ratio of EGR pressure / exhaust pressure.In one aspect of the invention, in relation to a direction of exhaust flow, the EGR pressure is sensed downstream of the EGR valve and the exhaust pressure is sensed upstream of the EGR valve.In one aspect of the invention, the method includes adjusting operating conditions responsive to indicating that EGR leakage is present, wherein the adjusting comprises adjusting one or more of a commanded position of the EGR valve, adjusting a quantity of fuel delivered to an engine, adjusting an ignition timing, adjusting a fuel injection timing, adjusting a charge air routing, and adjusting a mass air flow.In one aspect of the invention, the historical average offset is updated based on the current average offset.

Claims

A method comprising: determining that there is an exhaust gas recirculation (EGR) leak based on a comparison of a current average valve offset to a historical average EGR valve offset.The method of claim 1, further comprising determining that the EGR leakage is present based on a presence of engine misfire.The method of claim 2, wherein the EGR leakage is in response to the current average valve offset being greater than the historical average EGR valve offset.The method of claim 1, wherein determining that the EGR leakage is present is not performed when a keep alive memory of a controller is actively reset.The method of claim 1, wherein the EGR leakage is absent in response to the current average valve offset being less than or equal to the historical average EGR valve offset.The method of claim 5, further comprising updating the historical average EGR valve offset based on the current average valve offset.The method of claim 1, wherein the current average valve offset is based on a difference of a requested EGR flow rate and an actual EGR flow rate.The method of claim 1, wherein the current average valve offset is based on a ratio of EGR pressure sensor (EGRD) / exhaust pressure sensor (EXP).A system, comprising: an exhaust gas recirculation (EGR) system comprising an EGR valve upstream of an EGR cooler relative to a direction of EGR flow through the EGR system to an intake system, an exhaust gas sensor upstream of the EGR valve, and an EGR pressure (EGRD) sensor between the EGR valve and the EGR cooler; and a controller comprising computer readable instructions stored on a memory thereof that, when executed, enable the controller to: detect a plurality of EGR valve offsets during a plurality of drive cycles; determine an average historical EGR valve offset based on previous EGR valve offsets detected during a plurality of previous drive cycles; determining a current average EGR valve offset during a current drive cycle; comparing the current average EGR valve offset to the average historical EGR valve offset; and determining an EGR leakage in response to the current average EGR valve offset being greater than the average historical EGR valve offset in combination with detecting an engine misfire.The system of claim 9, wherein the average historical EGR valve offset is one of a plurality of average historical EGR valve offsets, each of the plurality of average historical EGR valve offsets based on operating parameters of a previous drive cycle of the plurality of previous drive cycles.The system of claim 9, wherein the current average EGR valve offset is determined based on an EGR cooler pressure model.The system of claim 9, wherein the instructions further cause the controller to adjust engine operating parameters in response to the EGR leakage occurring when the EGR valve is commanded closed.The system of claim 9, wherein the instructions further cause the controller to adjust an EGR valve position in response to the EGR leakage occurring when the EGR valve is in an at least partially open position.The system of claim 9, wherein the instructions further cause the controller to determine that the EGR leakage is not present in response to the current average EGR valve offset being less than or equal to the average historical EGR valve offset.The system of claim 9, wherein the instructions further cause the controller to determine that the EGR leakage is not present in response to the engine misfire not being present.

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