US20150088399A1 - Exhaust system and method of estimating diesel particulate filter soot loading for same - Google Patents
Exhaust system and method of estimating diesel particulate filter soot loading for same Download PDFInfo
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- US20150088399A1 US20150088399A1 US14/034,626 US201314034626A US2015088399A1 US 20150088399 A1 US20150088399 A1 US 20150088399A1 US 201314034626 A US201314034626 A US 201314034626A US 2015088399 A1 US2015088399 A1 US 2015088399A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
- F01N9/005—Electrical control of exhaust gas treating apparatus using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/029—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/04—Methods of control or diagnosing
- F01N2900/0412—Methods of control or diagnosing using pre-calibrated maps, tables or charts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/08—Parameters used for exhaust control or diagnosing said parameters being related to the engine
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1606—Particle filter loading or soot amount
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
- F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
- F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0812—Particle filter loading
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Definitions
- the present teachings generally include a method of estimating soot loading in a diesel particulate filter and an exhaust system implementing the method.
- Diesel particulate filters are designed to remove soot from the exhaust flow of a diesel engine. When the accumulated soot reaches a predetermined amount, the filter is “regenerated” by burning off the accumulated soot. There is no mechanism available to directly measure the amount of soot in the exhaust flow from the engine, or to directly measure the amount of soot in the DPF when the vehicle is in use. Accordingly, mathematical and empirical soot models have been used to estimate the amount of soot present in the filter so that timely disposal or regeneration of the filter can be assured. Modeling the exhaust flow and resultant DPF loading is dependent on complex chemical reactions and physical flow dynamics. One mathematical soot model is dependent on engine operating conditions and an engine-out soot rate resulting from the engine operating conditions.
- Another soot model estimates the amount of soot in the filter based on the pressure drop in exhaust flow through the filter (i.e., a differential pressure across the filter). This soot model is thus based partly on a measured parameter (pressure differential). Accuracy of the soot model used is important, as the DPF functions optimally when the amount of soot present is below a predetermined amount. An accurate soot model ensures that the DPF is not regenerated unnecessarily at relatively low soot concentrations (grams of soot per volume of filter), thus enhancing fuel economy.
- a DPF soot loading estimate using a mathematical model implemented by an onboard computer as an algorithm can be less expensive than measurement-based models that require numerous and/or expensive sensing devices, and can be used under a greater range of operating conditions than a measurement-based system.
- the accuracy of such a mathematical model can be improved if the model is updated by comparison of a model-based result with a measurement-based result, such as the pressure-based model.
- accurate DPF soot loading has been determined from offboard testing, in which the DPF is periodically removed from the exhaust system and weighed,—since the pressure-based model is only an accurate predictor of soot loading under certain engine operation conditions, such as high speed steady driving.
- a method of estimating soot loading is presented that enables reliance on a mathematical soot loading model, referred to herein as a DPF soot loading model, by updating an engine-out soot rate used in the mathematical model based on a differential pressure-based model under all engine operating conditions.
- a method of estimating soot loading in a DPF in a vehicle exhaust system includes determining engine operating conditions of an engine in exhaust flow communication with the diesel particulate filter, and monitoring a pressure differential of the exhaust flow across the diesel particulate filter.
- the method includes estimating soot loading in the diesel particulate filter according to a pressure-based model using the monitored pressure differential when the engine operating conditions are within a predetermined first set of engine operating conditions (defining an enable mode), and estimating soot loading in the diesel particulate filter according to an engine-out soot model and a DPF soot loading model when the engine operating conditions are within a predetermined second set of operating conditions (defining a disable mode).
- the estimating is via an electronic controller.
- the engine-out soot model and the DPF soot loading model are stored on the electronic controller.
- the engine-out soot model is based on the engine operating conditions
- the DPF soot loading model is based at least partially on the engine-out soot model.
- the method includes updating the engine-out soot model based in part on a difference in estimated soot loading between the pressure-based model and the DPF soot loading model. Updating the engine-out soot model is done in real time during the enable mode. As used herein, updating in “real time” means updating the engine-out soot model based on the difference without first requiring the occurrence of a subsequent event or condition. Updating the engine-out soot model is done after a return to engine operating conditions within the enable mode after operation in the disable mode, and is based in part on a saved estimated soot rate loading value from an engine operating point in the enable mode prior to the operation in the disable mode. That is, updating is not in real time during the disable mode, and instead occurs only after a return to the enable mode, when a pressure-differential measurement is again considered to be sufficiently indicative of soot loading.
- FIG. 1 is a schematic illustration of a vehicle exhaust system including a diesel particulate filter and a controller.
- FIG. 2 is a schematic diagram of the controller of FIG. 1 , including a processor with an engine-out soot model, a DPF soot loading model based partly on the engine-out soot model, a DPF soot loading pressure-based model, and a learning algorithm for the engine-out soot model.
- FIG. 3 is a schematic three-dimensional plot of engine-out soot rate, showing engine-out soot rate at various engine operating points according to engine speed and quantity of fuel injected, and associated current and updated engine-out soot rate values at predetermined engine operating points.
- FIG. 4 is a schematic illustration of a soot rate table showing engine-out soot rate as a function of engine speed and injected fuel quantity rate, and showing updated engine-out soot rate values for various engine operating conditions.
- FIG. 5 is a schematic three-dimensional plot of operation time at various engine operating points according to engine speed and injected fuel quantity rate, and the distribution of operation at one engine operating point to predetermined engine operating points
- FIG. 6 is a schematic illustration of a time table showing an engine operating point and the distribution of operation time at predetermined engine operating points having various engine speeds and at different injected fuel quantity rates.
- FIG. 7 is a schematic flow diagram of a method of estimating soot loading carried out by the controller of FIG. 1 via the models and learning algorithm of FIG. 2 .
- FIG. 1 shows a vehicle 10 that includes an engine 11 with a representative exhaust system 12 that includes a diesel particulate filter (DPF) 14 .
- a monitoring system 16 for the DPF 14 is operable to monitor the amount of soot mass in the DPF 14 in order to ensure filter performance, enhance overall fuel economy and reduction of emissions, and provide for timely regeneration of the DPF 14 .
- the exhaust system 12 includes a diesel oxidation catalyst 18 that oxidizes and burns hydrocarbons in the exhaust flow 20 exiting the engine 11 . Exhaust then flows through a selective catalytic reduction catalyst 22 , which converts at least some of the nitrogen oxides in the exhaust flow 20 into water and nitrogen. Exhaust then flows from an inlet 24 of the DPF 14 to an outlet 26 of the filter 14 , and then exits the exhaust system 12 .
- the exhaust system 12 may instead be arranged with the selective catalytic reduction catalyst 22 downstream of the DPF 14 without affecting the function of the monitoring system 16 .
- the monitoring system 16 includes a controller 28 that has a processor 30 that executes stored algorithms from a tangible, non-transitory memory, as described further with respect to FIG. 2 to estimate the amount of soot in the DPF 14 and output a control signal 38 that causes engine operation at conditions (such as increased fuel amount) that initiate regeneration of the DPF 14 .
- the DPF 14 is a type that is actively regenerated by changing operating parameters to increase exhaust flow temperature to burn the soot
- the signal 38 may affect engine parameters to cause the increase in temperature of the exhaust flow 20 .
- the monitoring system 16 may include an engine speed sensor 32 positioned in operative communication with the engine crankshaft 34 and operable to monitor engine speed 36 (also referred to as a first engine operating condition) such as in revolutions per minute (rpm) and provide a signal representing engine speed to the processor 30 .
- the monitoring system 16 includes a sensor 37 that measures air fuel ratio in the engine 11 and provides an air fuel ratio 42 via a signal to the processor 30 .
- the monitoring system 16 also includes a sensor 39 that measures air flow into the engine 11 and provides an air flow measurement 43 via a signal to the controller 28 .
- a fuel flow measuring device 49 measures an injected fuel quantity rate 47 (also referred to as a second engine operating condition) such as the fuel flow in cubic millimeters per engine stroke (mm 3 /cycle) into a fuel injection system for the engine 11 .
- the fuel quantity rate 47 is provided as a signal to the processor 30 .
- Fuel quantity rate 47 is proportional to engine load (e.g., torque at the crankshaft 34 ).
- Additional engine operating parameters and exhaust system 12 operating parameters can also be provided to the controller 28 and used by the stored algorithms on the processor 30 to estimate the amount of soot loading in the DPF 14 . For example, exhaust temperature and other parameters can be monitored.
- the monitoring system 16 also includes a differential pressure measurement device 44 that is operable to measure a third operating parameter, which is a pressure differential between exhaust flow at the inlet 24 and exhaust flow at the outlet 26 of the DPF 14 .
- the differential pressure measurement device 44 is in fluid communication with the exhaust flow 20 at the inlet 24 and at the outlet 26 and emits a signal representative of a differential pressure 46 (also referred to as a pressure drop).
- the differential pressure 46 is utilized by the processor 30 as further described below.
- the processor 30 is shown in more detail to represent the algorithms executed by and the empirical data accessed by the processor 30 .
- the processor 30 includes a first stored algorithm, also referred to as a DPF soot loading pressure-based model 50 , that provides an inferred DPF soot loading estimate based in part on the differential pressure 46 provided by the pressure measurement device 44 .
- the engine operating conditions 36 , 47 are also provided to the pressure-based model 50 .
- the pressure-based model 50 represents the dynamics of engine-out soot and DPF soot loading inferred from the pressure differential across the DPF 14 .
- the pressure-based model 50 can include stored data based on prior testing, including offline weighings of the DPF 14 that are coordinated with measured pressure differentials and engine operating conditions.
- the processor 30 includes a second stored algorithm, also referred to as a DPF soot loading model 52 that provides an estimated DPF soot loading based on a mathematical model of the DPF kinetic process.
- the mathematical model is dependent on the engine operating conditions 36 , 47 , as well as an estimated engine-out soot rate 53 provided as a signal from an engine-out soot model 54 .
- the engine-out soot model 54 is an input to the DPF soot loading model 52 , as it provides an estimated engine-out soot rate 53 used by the DPF soot loading model 52 .
- the engine-out soot model 54 is a group of stored lookup tables of engine-out soot rate values correlated with the selected engine operating points. An engine operating point is represented by an engine speed and by an injected fuel quantity rate in grams.
- a learning algorithm 56 is utilized that provides an output 59 that is an adaptation of the engine-out soot model 54 to update the engine-out soot model 54 under all engine operating conditions using a comparison of the estimated soot loading by the pressure-based model 50 and the estimated soot loading by the DPF soot loading model 52 .
- the DPF soot loading model 52 can provide a more accurate estimated DPF soot loading estimate adapting to different engine operation conditions.
- the pressure-based model 50 more accurately reflects actual DPF soot loading than does the DPF soot loading model 52 under a first set of engine operating conditions (the enable mode), and can thus be used as a check to update the DPF soot loading model 52 .
- the pressure-based model 50 is less accurate under other engine operating conditions (a second set of engine operating conditions called the disable mode). For example, at low engine speeds, or non-steady (transient) driving, the differential pressure 46 is less correlated with DPF soot loading than at high-speed, steady driving.
- the learning algorithm 56 enables the engine-out soot model 54 to be updated to reflect engine operation in the disable mode as well as in the enable mode, as described herein.
- the learning algorithm 56 extends updating of the engine-out soot model 54 and the DPF soot loading model 52 to an entire engine operating range (which is defined as the total of the first set of engine operating conditions and the second set of engine operation conditions).
- the learning algorithm 56 continuously adapts the engine-out soot model 54 and the DPF soot loading model 52 to the pressure-based model 50 .
- the learning algorithm 56 thus operates in one of two different operating modes: the disable mode or the enable mode, dependent on the engine operating conditions.
- the disable mode is defined as the engine operating conditions 36 , 47 being within the second set of engine operating conditions.
- the second set of engine operating conditions reflects low speed driving and/or start-stop driving.
- the enable mode the measured differential pressure 46 is relatively accurate, and the learning algorithm 56 provides real-time learning of the engine-out soot model 54 as described herein.
- the learning algorithm 56 determines and saves certain operating parameters during the disable mode, and then updates the engine-out soot model 54 based on the saved operating parameters when the engine operating conditions return to the enable mode. Accordingly, the learning algorithm 56 is effective to update the engine-out soot model 54 for all engine operating conditions, either in real time or at a later time, as described herein.
- the learning algorithm 56 accomplishes different tasks depending on whether it is in the enable mode, the disable mode, or transitioning from the disable mode to the enable mode. These tasks are described in detail herein, and are included in the method of estimating DPF soot loading 100 carried out by the controller 28 and the processor 30 thereon, as schematically illustrated in FIG. 7 .
- the controller 28 monitors engine operating conditions, including engine speed 36 and fuel quantity rate 47 . That is, the controller 28 tracks actual engine operating points within the range of engine operating conditions by periodically analyzing the engine speed 36 and fuel quantity rate 47 provided.
- the controller 28 also has a timer that measures the time of operation at each monitored engine operating point in step 104 .
- the controller 28 also periodically monitors the pressure differential 46 provided by the pressure differential measurement device 44 in step 106 . Steps 102 , 104 , 106 are repeated periodically throughout the method 100 .
- the processor 28 determines in step 108 whether the current engine operating conditions (i.e., the most recent monitored engine operating conditions) are within the first set of engine operating conditions. If the engine operating conditions are within the first set of engine operating conditions, then the learning algorithm 56 is in the enable mode, and the processor 30 accomplishes steps 110 - 120 as described herein.
- a lookup table 57 included in the engine-out soot model 54 stores engine-out soot rate 53 (in grams per second) according to engine speed 36 (in revolutions per minute) and fuel quantity rate 47 (mm 3 /cycle).
- engine-out soot rate 53 in grams per second
- fuel quantity rate 47 mm 3 /cycle
- Various current soot rate values 60 are indicated with open circles (i.e., the soot rate values at each engine operating point as stored in a lookup table 57 of the engine-out soot model 54 prior to updating).
- the initial current soot rate values 60 are based on initial soot rate values determined during offline testing for a vehicle having the engine 11 and exhaust system 12 , and are then updated during vehicle use according to the method 100 carried out by the processor 30 as described herein.
- Incremental soot rate values 62 A, 62 B, 62 C as determined by the pressure-based model 50 at a series of actual engine operating points as periodically determined in step 102 are indicated in FIG. 3 .
- the current stored soot rate values 60 in the lookup table of the engine-out soot model 54 are updated using each of the soot rate values 62 A, 62 B, 62 C determined by the pressure-based model 50 as described herein.
- the soot rate value 62 A determined at an actual engine operating point P x,y is used to provide updated engine-out soot rate values 64 A, 64 B, 64 C, 64 D, as shown above four corresponding current soot rate values 60 (i.e., the soot rate values for four engine operating conditions P1, P2, P3, P4 within a predetermined distance of the actual engine operating point P x,y that corresponds with soot rate value 62 A).
- the predetermined distance is the increment between adjacent stored engine speed 36 values and between adjacent stored fuel quantity rate 47 values in the lookup table 57 , as further described with respect to FIG. 4 .
- the main steps in the enable mode include step 110 , calculating the inferred DPF soot loading ⁇ circumflex over (M) ⁇ ⁇ p (t) from the differential pressure 46 ( ⁇ P) measurement via the pressure-based model 50 .
- step 112 estimated DPF soot loading ⁇ circumflex over (M) ⁇ 1dk (t) is then calculated from the DPF soot loading model 52 .
- a soot loading error ⁇ circumflex over (M) ⁇ (t) (also referred to as a soot loading difference) is then calculated in step 114 by subtracting the DPF soot loading model ⁇ circumflex over (M) ⁇ 1dk (t) from the inferred DPF soot loading ⁇ circumflex over (M) ⁇ ⁇ p (t):
- ⁇ circumflex over ( M ) ⁇ ( t ) ⁇ circumflex over (M) ⁇ ⁇ p ( t ) ⁇ ⁇ circumflex over (M) ⁇ 1dk ( t )
- the estimated soot rate error ⁇ circumflex over (Z) ⁇ (also referred to as a soot rate difference) is determined in step 116 by dividing the soot loading error ⁇ circumflex over (M) ⁇ (t) by the accumulated time T:
- FIG. 4 shows a soot rate table as a two-dimensional plot of fuel quantity rate 47 on the Y-axis versus engine speed 36 on the X-axis.
- current soot rate values 60 in the engine-out soot table 57 of FIG. 3 are updated by distributing the estimated soot rate error ⁇ circumflex over (Z) ⁇ to the soot rate values 60 at the four adjacent junction points of the engine-out soot table 57 , based on respective distances between the current engine operation point (P x,y ) (corresponding to the operating point having the soot rate 62 A) and the four adjacent junction points P1, P2, P3, P4.
- the distance from the engine operating point P x,y to its four adjacent junction points P1, P2, P3, P4 are d i,j , d i,j+1 , d i+1,j , and d i+1,j+1 respectively, then these distances can be calculated in step 118 by the geometric distance formula for determining the distance between two points in a plane, e.g., for d i,j :
- d i,j ⁇ square root over (( x ⁇ i ) 2 +( y ⁇ j ) 2 ) ⁇ square root over (( x ⁇ i ) 2 +( y ⁇ j ) 2 ) ⁇ .
- d d i,j +d i,j+1 +d i+1,j +d i+1,j+1 .
- soot rate values 60 at each adjacent junction point in the engine-out soot rate table 57 are updated to soot rate values 64 A, 64 B, 64 C, 64 D at time t by:
- Z i , j ⁇ ( t ) Z i , j ⁇ ( t - 1 ) + k ⁇ Z ⁇ ⁇ d i , j d ;
- Z i , j + 1 ⁇ ( t ) Z i , j + 1 ⁇ ( t - 1 ) + k ⁇ Z ⁇ ⁇ d i , j + 1 d ;
- Z i + 1 , j ⁇ ( t ) Z i + 1 , j ⁇ ( t - 1 ) + k ⁇ Z ⁇ ⁇ d i + 1 , j d ;
- Z i + 1 , j + 1 ⁇ ( t ) Z i + 1 , j + 1 ⁇ ( t - 1 ) + k ⁇ Z ⁇ ⁇ d i + 1 , j d ; and
- soot rate values 60 in the lookup table 57 are updated in step 120 via the output 59 by distributing the estimated engine out soot-rate error ⁇ circumflex over (Z) ⁇ in the lookup table 57 of FIG. 2 via soot rate error values that are calculated in proportion to the proximity of the engine operating points of the stored values (i.e., the current soot rate values 60 ) to the engine operating point at which the difference ⁇ circumflex over (M) ⁇ (t) is calculated.
- the method 100 then returns to step 108 .
- step 108 if it is then determined in step 108 that the engine operating conditions are in the disable mode, then at this transition from the enable mode to the disable mode, the learning algorithm 54 accomplishes steps 126 - 138 of the method 100 .
- the method 100 moves to step 126 in which the last soot loading estimate based on the pressure-based model 50 during engine operation in the enable mode is saved.
- the last soot loading estimate based on the DPF soot loading model 52 during engine operation in the enable mode is saved in step 127 .
- a lookup table 68 shown in FIG. 5 (named “Operation Time Table”) is constructed under the method 100 to record the engine operation time 70 A, 70 B, 70 C at different engine operating points such as engine operating point P x,y (shown in FIG. 6 ).
- Engine operation time 69 as determined in step 104 is stored according to engine speed 36 and fuel quantity rate 47 . For example, at engine operating point P x,y (e. g., corresponding with the engine operating point at which time 70 A is spent), let the engine operation time be T x,y , and then T x,y will be distributed and recorded at the four adjacent junction points PA, PB, PC, PD surrounding P x,y as described below.
- the four adjacent junction points in the Operation Time Table 68 are PA, PB, PC, PD (referred to as T i,j , T i,j+1 , T i+1,j , and T i+1,j+1 .)
- the distance from the engine operating point P x,y to its four adjacent junction points P1, P2, P3, P4 is d i,j , d i,j+1 , d i+1,j , and d i+1,j+1 respectively, and these distances can be calculated in step 128 by using the geometric distance formula for determining the distance between two points in a plane.
- the distance d i,j from point P x,y to point P1 is:
- d i,j ⁇ square root over (( x ⁇ i ) 2 +( y ⁇ j ) 2 ) ⁇ square root over (( x ⁇ i ) 2 +( y ⁇ j ) 2 ) ⁇ .
- d d i,j +d i,j+1 +d i+1,j +d i+1,j+1 .
- step 130 the engine operation time 70 A at the engine operating point P x,y is distributed to the four adjacent engine operating points PA, PB, PC, PD according to the proximity of each of the four points to the engine operation point P x,y at which the time 70 A was measured. Then, corresponding to the engine operating point P x,y , the engine operation time distributed in step 130 at each adjacent point (i, j) in the Operation Time Table 68 is as follows:
- T i , j ⁇ ( t ) T i , j ⁇ ( t - 1 ) + k ⁇ ⁇ T x , y ⁇ d i , j d ;
- T i , j + 1 ⁇ ( t ) T i , j + 1 ⁇ ( t - 1 ) + k ⁇ ⁇ T x , y ⁇ d i , j + 1 d ;
- T i + 1 , j ⁇ ( t ) T i + 1 , j ⁇ ( t - 1 ) + k ⁇ ⁇ T x , y ⁇ d i + 1 , j d ;
- T i + 1 , j + 1 ⁇ ( t ) T i + 1 , j + 1 ⁇ ( t - 1 ) + k ⁇ ⁇ T x , y ⁇ d i
- 0 ⁇ k ⁇ 1 is a distribution gain determined by experiment to keep the learning process (i.e., the updating) stable.
- the prior accumulated time 75 (if any) for operation during the second set of engine operating conditions at each of these points is shown with open circles in FIG. 5 (only one of which is labeled 75 ).
- the updated accumulated time 77 A, 77 B, 77 C, 77 D is shown at each point.
- step 131 it is then determined whether the engine operating conditions have returned to the enable mode. If they have not, then the method 100 returns to step 128 and continues to distribute time accumulated at a subsequent periodic engine operating point into the Operation Time Table 68 as described.
- the pressure-based model 50 is used to calculate the DPF soot accumulated during the time when the DPF ⁇ P measurement is disabled (i.e., during the disable mode). Soot loading determined to have occurred during the disable mode is distributed into each engine operating point during the disable mode according to the time spent thereon.
- the soot loading increment error ⁇ circumflex over (M) ⁇ (t e ) also referred to as a soot loading increment difference
- ⁇ circumflex over ( M ) ⁇ ( t e ) [ ⁇ circumflex over (M) ⁇ ⁇ p ( t e ) ⁇ ⁇ circumflex over (M) ⁇ ⁇ p ( t d )] ⁇ [ ⁇ circumflex over (M) ⁇ 1dk ( t e ) ⁇ ⁇ circumflex over (M) ⁇ 1dk ( t d )];
- ⁇ circumflex over (M) ⁇ 1dk (t e ) is the output of the DPF soot loading model 52
- ⁇ circumflex over (M) ⁇ ⁇ p (t e ) is the output of the pressure-based model 50
- t d and t e are the time of entering the disable mode (i.e., time at the first recorded engine operating point in the second set of engine operating conditions as determined in step 108 after steps 110 - 112 ), and the time of entering the enable mode (i.e., time at the first recorded engine operating point in the first set of engine operating conditions after operation in the second set of engine operating conditions as determined in step 126 ), respectively.
- step 134 the average total soot rate error M (also referred to as the average total soot rate difference) during the disable mode is calculated as follows:
- ⁇ ⁇ M _ ⁇ ⁇ M ⁇ ⁇ ( t e ) t e - t d .
- step 136 the lookup table 57 of the engine-out soot model 54 is updated via the output 50 by soot rate error values that are calculated by distributing the average total soot rate error M to each junction point, where the accumulated time is recorded during the disable mode in the Operation Time Table 68 , proportionally to the recorded accumulated time as an average soot rate error Z i,j (t):
- step 138 the operation time table 68 is cleared so that it is ready for use during a subsequent occurrence of operating in the disable mode following operation in the enable mode.
- the method 100 then returns to step 108 , with steps 102 , 104 , and 106 continuing periodically.
Abstract
Description
- The present teachings generally include a method of estimating soot loading in a diesel particulate filter and an exhaust system implementing the method.
- Diesel particulate filters (DPFs) are designed to remove soot from the exhaust flow of a diesel engine. When the accumulated soot reaches a predetermined amount, the filter is “regenerated” by burning off the accumulated soot. There is no mechanism available to directly measure the amount of soot in the exhaust flow from the engine, or to directly measure the amount of soot in the DPF when the vehicle is in use. Accordingly, mathematical and empirical soot models have been used to estimate the amount of soot present in the filter so that timely disposal or regeneration of the filter can be assured. Modeling the exhaust flow and resultant DPF loading is dependent on complex chemical reactions and physical flow dynamics. One mathematical soot model is dependent on engine operating conditions and an engine-out soot rate resulting from the engine operating conditions. Another soot model estimates the amount of soot in the filter based on the pressure drop in exhaust flow through the filter (i.e., a differential pressure across the filter). This soot model is thus based partly on a measured parameter (pressure differential). Accuracy of the soot model used is important, as the DPF functions optimally when the amount of soot present is below a predetermined amount. An accurate soot model ensures that the DPF is not regenerated unnecessarily at relatively low soot concentrations (grams of soot per volume of filter), thus enhancing fuel economy.
- A DPF soot loading estimate using a mathematical model implemented by an onboard computer as an algorithm can be less expensive than measurement-based models that require numerous and/or expensive sensing devices, and can be used under a greater range of operating conditions than a measurement-based system. The accuracy of such a mathematical model can be improved if the model is updated by comparison of a model-based result with a measurement-based result, such as the pressure-based model. However, accurate DPF soot loading has been determined from offboard testing, in which the DPF is periodically removed from the exhaust system and weighed,—since the pressure-based model is only an accurate predictor of soot loading under certain engine operation conditions, such as high speed steady driving.
- A method of estimating soot loading is presented that enables reliance on a mathematical soot loading model, referred to herein as a DPF soot loading model, by updating an engine-out soot rate used in the mathematical model based on a differential pressure-based model under all engine operating conditions. A method of estimating soot loading in a DPF in a vehicle exhaust system includes determining engine operating conditions of an engine in exhaust flow communication with the diesel particulate filter, and monitoring a pressure differential of the exhaust flow across the diesel particulate filter. The method includes estimating soot loading in the diesel particulate filter according to a pressure-based model using the monitored pressure differential when the engine operating conditions are within a predetermined first set of engine operating conditions (defining an enable mode), and estimating soot loading in the diesel particulate filter according to an engine-out soot model and a DPF soot loading model when the engine operating conditions are within a predetermined second set of operating conditions (defining a disable mode). In both cases, the estimating is via an electronic controller. The engine-out soot model and the DPF soot loading model are stored on the electronic controller. The engine-out soot model is based on the engine operating conditions, and the DPF soot loading model is based at least partially on the engine-out soot model.
- The method includes updating the engine-out soot model based in part on a difference in estimated soot loading between the pressure-based model and the DPF soot loading model. Updating the engine-out soot model is done in real time during the enable mode. As used herein, updating in “real time” means updating the engine-out soot model based on the difference without first requiring the occurrence of a subsequent event or condition. Updating the engine-out soot model is done after a return to engine operating conditions within the enable mode after operation in the disable mode, and is based in part on a saved estimated soot rate loading value from an engine operating point in the enable mode prior to the operation in the disable mode. That is, updating is not in real time during the disable mode, and instead occurs only after a return to the enable mode, when a pressure-differential measurement is again considered to be sufficiently indicative of soot loading.
- The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings.
-
FIG. 1 is a schematic illustration of a vehicle exhaust system including a diesel particulate filter and a controller. -
FIG. 2 is a schematic diagram of the controller ofFIG. 1 , including a processor with an engine-out soot model, a DPF soot loading model based partly on the engine-out soot model, a DPF soot loading pressure-based model, and a learning algorithm for the engine-out soot model. -
FIG. 3 is a schematic three-dimensional plot of engine-out soot rate, showing engine-out soot rate at various engine operating points according to engine speed and quantity of fuel injected, and associated current and updated engine-out soot rate values at predetermined engine operating points. -
FIG. 4 is a schematic illustration of a soot rate table showing engine-out soot rate as a function of engine speed and injected fuel quantity rate, and showing updated engine-out soot rate values for various engine operating conditions. -
FIG. 5 is a schematic three-dimensional plot of operation time at various engine operating points according to engine speed and injected fuel quantity rate, and the distribution of operation at one engine operating point to predetermined engine operating points -
FIG. 6 is a schematic illustration of a time table showing an engine operating point and the distribution of operation time at predetermined engine operating points having various engine speeds and at different injected fuel quantity rates. -
FIG. 7 is a schematic flow diagram of a method of estimating soot loading carried out by the controller ofFIG. 1 via the models and learning algorithm ofFIG. 2 . - Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,
FIG. 1 shows avehicle 10 that includes anengine 11 with arepresentative exhaust system 12 that includes a diesel particulate filter (DPF) 14. Amonitoring system 16 for theDPF 14 is operable to monitor the amount of soot mass in theDPF 14 in order to ensure filter performance, enhance overall fuel economy and reduction of emissions, and provide for timely regeneration of theDPF 14. - The
exhaust system 12 includes adiesel oxidation catalyst 18 that oxidizes and burns hydrocarbons in theexhaust flow 20 exiting theengine 11. Exhaust then flows through a selectivecatalytic reduction catalyst 22, which converts at least some of the nitrogen oxides in theexhaust flow 20 into water and nitrogen. Exhaust then flows from aninlet 24 of theDPF 14 to anoutlet 26 of thefilter 14, and then exits theexhaust system 12. Theexhaust system 12 may instead be arranged with the selectivecatalytic reduction catalyst 22 downstream of theDPF 14 without affecting the function of themonitoring system 16. - The
monitoring system 16 includes acontroller 28 that has aprocessor 30 that executes stored algorithms from a tangible, non-transitory memory, as described further with respect toFIG. 2 to estimate the amount of soot in theDPF 14 and output acontrol signal 38 that causes engine operation at conditions (such as increased fuel amount) that initiate regeneration of theDPF 14. If theDPF 14 is a type that is actively regenerated by changing operating parameters to increase exhaust flow temperature to burn the soot, thesignal 38 may affect engine parameters to cause the increase in temperature of theexhaust flow 20. - Data reflecting real-time operating parameters in the
exhaust system 12 is input into thecontroller 28 and used by various ones of the stored algorithms as described herein. For example, themonitoring system 16 may include anengine speed sensor 32 positioned in operative communication with theengine crankshaft 34 and operable to monitor engine speed 36 (also referred to as a first engine operating condition) such as in revolutions per minute (rpm) and provide a signal representing engine speed to theprocessor 30. Additionally, themonitoring system 16 includes asensor 37 that measures air fuel ratio in theengine 11 and provides anair fuel ratio 42 via a signal to theprocessor 30. Themonitoring system 16 also includes asensor 39 that measures air flow into theengine 11 and provides anair flow measurement 43 via a signal to thecontroller 28. A fuelflow measuring device 49 measures an injected fuel quantity rate 47 (also referred to as a second engine operating condition) such as the fuel flow in cubic millimeters per engine stroke (mm3/cycle) into a fuel injection system for theengine 11. Thefuel quantity rate 47 is provided as a signal to theprocessor 30.Fuel quantity rate 47 is proportional to engine load (e.g., torque at the crankshaft 34). Additional engine operating parameters andexhaust system 12 operating parameters can also be provided to thecontroller 28 and used by the stored algorithms on theprocessor 30 to estimate the amount of soot loading in theDPF 14. For example, exhaust temperature and other parameters can be monitored. - The
monitoring system 16 also includes a differentialpressure measurement device 44 that is operable to measure a third operating parameter, which is a pressure differential between exhaust flow at theinlet 24 and exhaust flow at theoutlet 26 of theDPF 14. The differentialpressure measurement device 44 is in fluid communication with theexhaust flow 20 at theinlet 24 and at theoutlet 26 and emits a signal representative of a differential pressure 46 (also referred to as a pressure drop). Thedifferential pressure 46 is utilized by theprocessor 30 as further described below. - Referring to
FIG. 2 , theprocessor 30 is shown in more detail to represent the algorithms executed by and the empirical data accessed by theprocessor 30. Theprocessor 30 includes a first stored algorithm, also referred to as a DPF soot loading pressure-basedmodel 50, that provides an inferred DPF soot loading estimate based in part on thedifferential pressure 46 provided by thepressure measurement device 44. Theengine operating conditions model 50. The pressure-basedmodel 50 represents the dynamics of engine-out soot and DPF soot loading inferred from the pressure differential across theDPF 14. The pressure-basedmodel 50 can include stored data based on prior testing, including offline weighings of theDPF 14 that are coordinated with measured pressure differentials and engine operating conditions. - The
processor 30 includes a second stored algorithm, also referred to as a DPFsoot loading model 52 that provides an estimated DPF soot loading based on a mathematical model of the DPF kinetic process. The mathematical model is dependent on theengine operating conditions out soot rate 53 provided as a signal from an engine-out soot model 54. The engine-outsoot model 54 is an input to the DPFsoot loading model 52, as it provides an estimated engine-outsoot rate 53 used by the DPFsoot loading model 52. The engine-outsoot model 54 is a group of stored lookup tables of engine-out soot rate values correlated with the selected engine operating points. An engine operating point is represented by an engine speed and by an injected fuel quantity rate in grams. - Finally, a
learning algorithm 56 is utilized that provides anoutput 59 that is an adaptation of the engine-outsoot model 54 to update the engine-outsoot model 54 under all engine operating conditions using a comparison of the estimated soot loading by the pressure-basedmodel 50 and the estimated soot loading by the DPFsoot loading model 52. By updating the engine-outsoot model 54 under all engine operating conditions based on this comparison, the DPFsoot loading model 52 can provide a more accurate estimated DPF soot loading estimate adapting to different engine operation conditions. The pressure-basedmodel 50 more accurately reflects actual DPF soot loading than does the DPFsoot loading model 52 under a first set of engine operating conditions (the enable mode), and can thus be used as a check to update the DPFsoot loading model 52. However, the pressure-basedmodel 50 is less accurate under other engine operating conditions (a second set of engine operating conditions called the disable mode). For example, at low engine speeds, or non-steady (transient) driving, thedifferential pressure 46 is less correlated with DPF soot loading than at high-speed, steady driving. - The
learning algorithm 56 enables the engine-outsoot model 54 to be updated to reflect engine operation in the disable mode as well as in the enable mode, as described herein. In other words, thelearning algorithm 56 extends updating of the engine-outsoot model 54 and the DPFsoot loading model 52 to an entire engine operating range (which is defined as the total of the first set of engine operating conditions and the second set of engine operation conditions). Thelearning algorithm 56 continuously adapts the engine-outsoot model 54 and the DPFsoot loading model 52 to the pressure-basedmodel 50. - The
learning algorithm 56 thus operates in one of two different operating modes: the disable mode or the enable mode, dependent on the engine operating conditions. In the disable mode, measurement of the pressure differential 46 is relatively inaccurate. The disable mode is defined as theengine operating conditions soot model 54. The second set of engine operating conditions reflects low speed driving and/or start-stop driving. In the enable mode, the measureddifferential pressure 46 is relatively accurate, and thelearning algorithm 56 provides real-time learning of the engine-outsoot model 54 as described herein. Thelearning algorithm 56 determines and saves certain operating parameters during the disable mode, and then updates the engine-outsoot model 54 based on the saved operating parameters when the engine operating conditions return to the enable mode. Accordingly, thelearning algorithm 56 is effective to update the engine-outsoot model 54 for all engine operating conditions, either in real time or at a later time, as described herein. - The
learning algorithm 56 accomplishes different tasks depending on whether it is in the enable mode, the disable mode, or transitioning from the disable mode to the enable mode. These tasks are described in detail herein, and are included in the method of estimatingDPF soot loading 100 carried out by thecontroller 28 and theprocessor 30 thereon, as schematically illustrated inFIG. 7 . In afirst step 102, thecontroller 28 monitors engine operating conditions, includingengine speed 36 andfuel quantity rate 47. That is, thecontroller 28 tracks actual engine operating points within the range of engine operating conditions by periodically analyzing theengine speed 36 andfuel quantity rate 47 provided. Thecontroller 28 also has a timer that measures the time of operation at each monitored engine operating point instep 104. Thecontroller 28 also periodically monitors the pressure differential 46 provided by the pressuredifferential measurement device 44 instep 106.Steps method 100. - Based on the engine operating conditions determined in
step 102, theprocessor 28 determines instep 108 whether the current engine operating conditions (i.e., the most recent monitored engine operating conditions) are within the first set of engine operating conditions. If the engine operating conditions are within the first set of engine operating conditions, then thelearning algorithm 56 is in the enable mode, and theprocessor 30 accomplishes steps 110-120 as described herein. - In the enable mode, the
differential pressure measurement 46 can be relied upon to accurately reflect the amount of accumulated soot in theDPF 14, and the pressure-basedmodel 50 can thus be used to update the engine-outsoot model 54 directly. Referring toFIG. 3 , a lookup table 57 included in the engine-outsoot model 54 stores engine-out soot rate 53 (in grams per second) according to engine speed 36 (in revolutions per minute) and fuel quantity rate 47 (mm3/cycle). Various currentsoot rate values 60 are indicated with open circles (i.e., the soot rate values at each engine operating point as stored in a lookup table 57 of the engine-outsoot model 54 prior to updating). Only some of the currentsoot rate values 60 are labeled. The initial currentsoot rate values 60 are based on initial soot rate values determined during offline testing for a vehicle having theengine 11 andexhaust system 12, and are then updated during vehicle use according to themethod 100 carried out by theprocessor 30 as described herein. Incrementalsoot rate values model 50 at a series of actual engine operating points as periodically determined instep 102 are indicated inFIG. 3 . The current storedsoot rate values 60 in the lookup table of the engine-outsoot model 54 are updated using each of thesoot rate values model 50 as described herein. - The
soot rate value 62A determined at an actual engine operating point Px,y is used to provide updated engine-outsoot rate values soot rate value 62A). The predetermined distance is the increment between adjacent storedengine speed 36 values and between adjacent storedfuel quantity rate 47 values in the lookup table 57, as further described with respect toFIG. 4 . Currentsoot rate values 60 within a predetermined distance of the actual engine operating points corresponding with the engine-outsoot rate values soot model 54 to calculate the estimatedengine soot rate 53. - Referring again to
FIG. 7 , the main steps in the enable mode includestep 110, calculating the inferred DPF soot loading {circumflex over (M)}Δp(t) from the differential pressure 46 (ΔP) measurement via the pressure-basedmodel 50. - In
step 112, estimated DPF soot loading {circumflex over (M)}1dk(t) is then calculated from the DPFsoot loading model 52. A soot loading error {circumflex over (M)}(t) (also referred to as a soot loading difference) is then calculated instep 114 by subtracting the DPF soot loading model {circumflex over (M)}1dk(t) from the inferred DPF soot loading {circumflex over (M)}Δp(t): -
Δ{circumflex over (M)}(t)={circumflex over (M)} Δp(t)−{circumflex over (M)} 1dk(t) - Using the accumulated time T at the engine operating point (e.g., the point having the
soot rate value 62A) as determined instep 104, the estimated soot rate error {circumflex over (Z)} (also referred to as a soot rate difference) is determined instep 116 by dividing the soot loading error {circumflex over (M)}(t) by the accumulated time T: -
-
FIG. 4 shows a soot rate table as a two-dimensional plot offuel quantity rate 47 on the Y-axis versusengine speed 36 on the X-axis. As illustrated inFIG. 4 , currentsoot rate values 60 in the engine-out soot table 57 ofFIG. 3 are updated by distributing the estimated soot rate error {circumflex over (Z)} to thesoot rate values 60 at the four adjacent junction points of the engine-out soot table 57, based on respective distances between the current engine operation point (Px,y) (corresponding to the operating point having thesoot rate 62A) and the four adjacent junction points P1, P2, P3, P4. If the distance from the engine operating point Px,y to its four adjacent junction points P1, P2, P3, P4 are di,j, di,j+1, di+1,j, and di+1,j+1 respectively, then these distances can be calculated instep 118 by the geometric distance formula for determining the distance between two points in a plane, e.g., for di,j: -
d i,j=√{square root over ((x−i)2+(y−j)2)}{square root over ((x−i)2+(y−j)2)}. - The total distance d from the engine operating point Px,y to these four adjacent points is:
-
d=d i,j +d i,j+1 +d i+1,j +d i+1,j+1. - Corresponding to the engine operating point Pi,j, the current soot rates values 60 at each adjacent junction point in the engine-out soot rate table 57 (i.e.,
soot rate values 60 at time t−1) are updated tosoot rate values -
- where 0≦k≦1 is a distribution gain determined by experiment to keep the learning process (i.e., the updating process) stable. Accordingly, the
soot rate values 60 in the lookup table 57 are updated instep 120 via theoutput 59 by distributing the estimated engine out soot-rate error {circumflex over (Z)} in the lookup table 57 ofFIG. 2 via soot rate error values that are calculated in proportion to the proximity of the engine operating points of the stored values (i.e., the current soot rate values 60) to the engine operating point at which the difference {circumflex over (M)}(t) is calculated. Themethod 100 then returns to step 108. - After
steps 110 to 120, if it is then determined instep 108 that the engine operating conditions are in the disable mode, then at this transition from the enable mode to the disable mode, thelearning algorithm 54 accomplishes steps 126-138 of themethod 100. First, themethod 100 moves to step 126 in which the last soot loading estimate based on the pressure-basedmodel 50 during engine operation in the enable mode is saved. The last soot loading estimate based on the DPFsoot loading model 52 during engine operation in the enable mode is saved instep 127. - Once in the disable mode, a lookup table 68 shown in
FIG. 5 (named “Operation Time Table”) is constructed under themethod 100 to record theengine operation time FIG. 6 ).Engine operation time 69 as determined instep 104 is stored according toengine speed 36 andfuel quantity rate 47. For example, at engine operating point Px,y (e. g., corresponding with the engine operating point at whichtime 70A is spent), let the engine operation time be Tx,y, and then Tx,y will be distributed and recorded at the four adjacent junction points PA, PB, PC, PD surrounding Px,y as described below. - The four adjacent junction points in the Operation Time Table 68 are PA, PB, PC, PD (referred to as Ti,j, Ti,j+1, Ti+1,j, and Ti+1,j+1.) The distance from the engine operating point Px,y to its four adjacent junction points P1, P2, P3, P4 is di,j, di,j+1, di+1,j, and di+1,j+1 respectively, and these distances can be calculated in
step 128 by using the geometric distance formula for determining the distance between two points in a plane. For example, the distance di,j from point Px,y to point P1 is: -
d i,j=√{square root over ((x−i)2+(y−j)2)}{square root over ((x−i)2+(y−j)2)}. - The total distance d from the engine operating point Px,y to these four adjacent points is:
-
d=d i,j +d i,j+1 +d i+1,j +d i+1,j+1. - In
step 130, theengine operation time 70A at the engine operating point Px,y is distributed to the four adjacent engine operating points PA, PB, PC, PD according to the proximity of each of the four points to the engine operation point Px,y at which thetime 70A was measured. Then, corresponding to the engine operating point Px,y, the engine operation time distributed instep 130 at each adjacent point (i, j) in the Operation Time Table 68 is as follows: -
- where 0≦k≦1 is a distribution gain determined by experiment to keep the learning process (i.e., the updating) stable. The prior accumulated time 75 (if any) for operation during the second set of engine operating conditions at each of these points is shown with open circles in
FIG. 5 (only one of which is labeled 75). The updated accumulatedtime - In
step 131, it is then determined whether the engine operating conditions have returned to the enable mode. If they have not, then themethod 100 returns to step 128 and continues to distribute time accumulated at a subsequent periodic engine operating point into the Operation Time Table 68 as described. When monitoring understep 131 indicates that engine operating conditions have returned to the enable mode, reliance on the pressuredifferential measurement 46 is resumed. The pressure-basedmodel 50 is used to calculate the DPF soot accumulated during the time when the DPF ΔP measurement is disabled (i.e., during the disable mode). Soot loading determined to have occurred during the disable mode is distributed into each engine operating point during the disable mode according to the time spent thereon. In order to transition from the disable mode to the enable mode, instep 132, the soot loading increment error {circumflex over (M)}(te) (also referred to as a soot loading increment difference) - during the disable mode is calculated as follows:
-
Δ{circumflex over (M)}(t e)=[{circumflex over (M)} Δp(t e)−{circumflex over (M)} Δp(t d)]−[{circumflex over (M)} 1dk(t e)−{circumflex over (M)} 1dk(t d)]; - where, referring to
FIG. 2 , {circumflex over (M)}1dk(te) is the output of the DPFsoot loading model 52, {circumflex over (M)}Δp(te) is the output of the pressure-basedmodel 50; and td and te are the time of entering the disable mode (i.e., time at the first recorded engine operating point in the second set of engine operating conditions as determined instep 108 after steps 110-112), and the time of entering the enable mode (i.e., time at the first recorded engine operating point in the first set of engine operating conditions after operation in the second set of engine operating conditions as determined in step 126), respectively. - Next, in
step 134, the average total soot rate errorM (also referred to as the average total soot rate difference) during the disable mode is calculated as follows: -
- In
step 136, the lookup table 57 of the engine-outsoot model 54 is updated via theoutput 50 by soot rate error values that are calculated by distributing the average total soot rate errorM to each junction point, where the accumulated time is recorded during the disable mode in the Operation Time Table 68, proportionally to the recorded accumulated time as an average soot rate error Zi,j(t): -
Z i,j(t)=Z i,j(t−1)+[T i,j ΔM ]. - Finally, in
step 138, the operation time table 68 is cleared so that it is ready for use during a subsequent occurrence of operating in the disable mode following operation in the enable mode. Themethod 100 then returns to step 108, withsteps - While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.
Claims (17)
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US14/034,626 US20150088399A1 (en) | 2013-09-24 | 2013-09-24 | Exhaust system and method of estimating diesel particulate filter soot loading for same |
DE201410113474 DE102014113474A1 (en) | 2013-09-24 | 2014-09-18 | EXHAUST SYSTEM AND METHOD FOR ESTIMATING A SOIL LOADING OF A DIESEL PARTICLE FILTER THEREFOR |
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