DE102023201660B3 - Method for operating a drive device for a motor vehicle and corresponding drive device - Google Patents

Abstract

The invention relates to a method for operating a drive device (1) for a motor vehicle, which has a drive unit (2) that generates exhaust gas and an exhaust gas aftertreatment device (3) for aftertreatment of the exhaust gas, using a first lambda probe (5) upstream of the exhaust gas aftertreatment device (3 ) a first measured value and a second measured value is measured by means of a second lambda probe (6) downstream of the first lambda probe (6), and wherein an exit concentration of at least one exhaust gas component downstream of the exhaust gas aftertreatment device (3) is determined by means of an exhaust gas aftertreatment model, the input variables being one for a Entry concentration determined at the entry point (14) and an entry combustion air ratio determined for the entry point (14) are supplied. It is provided that the inlet combustion air ratio is determined from the second measured value independently of the first measured value. The invention further relates to a drive device (1) for a motor vehicle.

Description

The invention relates to a method for operating a drive device for a motor vehicle, which has a drive unit that generates exhaust gas and an exhaust gas aftertreatment device for aftertreatment of the exhaust gas. The invention further relates to a drive device for a motor vehicle.

For example, the publication is from the prior art US 2013 / 0 245 919 A1 known. This discloses a method in which a fuel injection amount is adjusted based on an oxidation state of a catalyst. The oxidation state is based on reaction rates of a large number of exhaust gas species over a catalyst longitudinal axis and a set of axially averaged mass balance and energy balance equations for a fluid phase and a washcoat of the catalyst.

The publication DE 196 06 652 B4 discloses a method for adjusting the fuel-air ratio for an internal combustion engine with a downstream catalytic converter capable of storing oxygen, in which the oxygen components in the exhaust gas of the internal combustion engine are detected in front of and behind the catalytic converter and influence the setting of the fuel-air ratio. It is provided that the current oxygen filling level of the catalytic converter is determined based on an oxygen model of the catalytic converter and based on the detected oxygen proportions in the exhaust gas of the internal combustion engine before and after the catalytic converter, that parameters of the oxygen model are changed based on the oxygen proportion measured behind the catalytic converter, that a A setpoint value for the oxygen filling level of the catalyst lying between a lower limit and an upper limit is specified, and that the fuel-air ratio is set depending on the determined actual oxygen filling level.

Furthermore, the publications are from the prior art DE 10 2017 208 671 B4 and DE 10 2018 132 466 A1 known.

It is the object of the invention to propose a method for operating a drive device for a motor vehicle, which has advantages over the prior art, in particular reliably monitoring pollutant emissions from the drive device in order to ensure compliance with limit values.

This is achieved according to the invention with a method for operating a drive device for a motor vehicle with the features of claim 1. It is provided that the inlet combustion air ratio is determined from the second measured value independently of the first measured value.

Advantageous embodiments with useful developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not restrictive; Rather, any variations of the features disclosed in the description, the claims and the figures can be realized.

The drive device serves to drive the motor vehicle, i.e. to provide a drive torque aimed at driving the motor vehicle. The drive device is preferably part of the motor vehicle, but can of course also be present separately from it. To provide the drive torque, the drive direction has the drive unit, which is preferably designed as an internal combustion engine. The drive unit is supplied with fuel and fresh gas at least temporarily during operation of the drive device, the fresh gas containing fresh air at least temporarily. In addition, the fresh gas can have exhaust gas, provided that exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially returned to the drive unit, namely as a component of the fresh gas. The fuel and the fresh gas that are supplied to the drive unit form a fuel-fresh gas mixture with a specific composition, which is reacted in the drive unit.

During operation of the drive unit, due to the chemical reaction between fuel and fresh gas, exhaust gas is produced, which is discharged towards an external environment of the drive device or the motor vehicle. Since pollutants are contained in the exhaust gas generated by the drive unit, the exhaust gas is first fed to the exhaust gas aftertreatment device before being released into the external environment. In the exhaust gas aftertreatment device, the pollutants are at least partially converted into less dangerous products. Only after passing through the exhaust gas aftertreatment device is the exhaust gas discharged into the outside environment. The exhaust gas aftertreatment device is present, for example, as a vehicle catalytic converter, in particular as a three-way catalytic converter, oxidation catalytic converter, NO _x storage catalytic converter or SCR catalytic converter. However, it can also be designed as a particle filter, in particular as a gasoline particle filter or as a diesel particle filter, preferably with an integrated vehicle catalytic converter, for example with a catalytic coating.

In order to determine the pollutant emissions of the drive device, i.e. the amount of the at least one exhaust gas component released into the external environment, the exhaust gas aftertreatment model is used. The exhaust gas aftertreatment model models the conversion of the at least one exhaust gas component using the exhaust gas aftertreatment device. For this purpose, the inlet concentration of the at least one exhaust gas component that is present at the inlet point is supplied to the exhaust gas aftertreatment model as a first input variable.

The entry point is to be understood in particular as meaning the point at which the exhaust gas enters the exhaust gas aftertreatment device. Alternatively, the entry point refers to the point at which the exhaust gas enters a specific section of the exhaust gas aftertreatment device, in particular into one of several sections. Based on the inlet concentration, the exhaust gas aftertreatment model calculates an outlet concentration, which is present at an exit point. Analogous to the entry point, the exit point refers to the point at which the exhaust gas exits the exhaust gas aftertreatment device or the section of the exhaust gas aftertreatment device.

The inlet concentration can in principle be determined in any way, for example it is determined depending on an operating point of the drive unit, the operating point being characterized, for example, by the drive torque currently provided by the drive unit and/or a current speed of the drive unit. If the entry point is the point at which the exhaust gas enters the exhaust gas aftertreatment device, the entry concentration present at the entry point is equal to a raw emission of the drive unit, i.e. equal to the amount of the at least one exhaust gas component generated or emitted by the drive unit. If the entry point is downstream of this point, the entry concentration present at the entry point is preferably determined using the exhaust gas aftertreatment model. For example, in this case, the inlet concentration for one of the sections corresponds to the outlet concentration for a section of the exhaust gas aftertreatment device preceding the section.

As an additional input variable, the inlet combustion air ratio is supplied to the exhaust gas aftertreatment model, which is determined analogously to the inlet concentration for the inlet point. For example, it could be provided that the inlet combustion air ratio is set equal to a combustion air ratio which is determined from the first measured value, which is measured using the first lambda sensor upstream of the exhaust gas aftertreatment device. The first measured value describes the combustion air ratio present in the exhaust gas upstream of the exhaust gas aftertreatment device or an amount of residual oxygen present there in the exhaust gas.

However, the first measured value is usually subject to a comparatively large measurement error, especially if a broadband lambda sensor is used as the first lambda sensor. Even a measurement error of less than one percent leads to an intolerable loss in the accuracy of the exhaust gas aftertreatment model. For this reason, it can be provided to correct the first measured value using a trim control based on the second measured value. The second measured value is measured using the second lambda sensor and describes the combustion air ratio or the amount of residual oxygen downstream of the first lambda sensor, in particular downstream of the exhaust gas aftertreatment device. For example, it is provided to regulate the second measured value to a setpoint and to determine from this an offset with which the first measured value is applied, in particular to carry out a lambda control based on the first measured value.

However, the applicant's investigations have shown that the first measured value after carrying out the trim control has sufficient accuracy for the lambda control, but not necessarily for the exhaust gas aftertreatment model. In addition, the broadband lambda probe does not have ideal dynamic properties. This becomes noticeable, for example, after the drive unit is overrun, in that after a sudden change in the composition of the fuel-fresh gas mixture, the probe follows this change over a certain period of time. This leads to errors in the exhaust aftertreatment model.

For this reason, it is now provided that the inlet combustion air ratio is determined from the second measured value independently of the first measured value. This means that the inlet combustion air ratio only depends on the second measured value measured downstream of the first lambda sensor, but not on the first measured value. In other words, the first measured value is not taken into account when determining the inlet combustion air ratio, but - of the two measured values - only the second measured value is taken into account. As a result, the inlet combustion air ratio can be determined with such high precision that the exhaust gas aftertaste can also be determined Action model can be carried out with good results, so that the exit concentration describes the concentration of the at least one exhaust gas component actually present in the exhaust gas at the exit point with high accuracy.

A further development of the invention provides that a broadband lambda probe is used as the first lambda probe and/or a jump lambda probe is used as the second lambda probe. While the broadband lambda probe has a comparatively wide measuring range, this is not the case for the jump lambda probe. The jump lambda probe is, for example, in the form of a single Nernst cell and can also be referred to as a voltage jump probe. The broadband lambda probe, on the other hand, consists of a Nernst cell and a pump cell. The pump cell is set in such a way that a combustion air ratio of λ = 1 is measured using the Nernst cell. The current intensity and/or the voltage of the electrical current used to operate the pump cell then represents a measure of the combustion air ratio actually present in the exhaust gas. The use of the broadband lambda probe as the first lambda probe and the jump lambda probe as the second lambda probe enables, in particular, precise implementation of the lambda control.

A further development of the invention provides that the second measured value is converted into a combustion air ratio using a probe characteristic curve, from which the inlet combustion air ratio is determined. The second measured value is therefore first converted into the combustion air ratio, namely using the probe characteristic curve. The probe characteristic curve is tailored to the second lambda probe and describes its behavior. In particular, values for the combustion air ratio are stored in the probe characteristic curve, which are available for different measured values. The probe characteristic curve can be stored in any way, for example using a mathematical relationship, a characteristic map and/or a table. The inlet combustion air ratio is then determined from the combustion air ratio. The use of the probe characteristic curve to convert the second measured value into the combustion air ratio can, on the one hand, be implemented with little computational effort and, on the other hand, is sufficiently accurate to operate the exhaust gas aftertreatment model on the basis of the combustion air ratio.

A further development of the invention provides that the inlet combustion air ratio is determined based on a time derivative of the combustion air ratio. The inlet combustion air ratio does not correspond directly to the combustion air ratio determined from the second measured value, but a correction is made. This consists of determining the time derivative of the combustion air ratio. On this basis, the inlet combustion air ratio is then determined so that it is present as a function of at least the time derivative of the combustion air ratio. This allows the inlet combustion air ratio to be determined with high accuracy in a comparatively simple manner.

A further development of the invention provides that the time derivative, subjected to a correction factor describing an influence of the exhaust gas aftertreatment device, is used when determining the inlet combustion air ratio. Since the second measured value is measured downstream of the first lambda sensor and in particular downstream of the entry point, the exhaust gas aftertreatment device significantly influences the inlet combustion air ratio determined from the second measured value. In particular, the inlet combustion air ratio is dependent on the oxygen storage capacity of the exhaust gas aftertreatment device and/or the exhaust gas mass flow of the exhaust gas flowing through the exhaust gas aftertreatment device. For this reason, the time derivative of the combustion air ratio is first applied with the correction factor before it is incorporated into the inlet combustion air ratio. This allows the accuracy of the exhaust gas aftertreatment model to be further increased.

A further development of the invention provides that the correction factor is determined as a function of at least one of the variables mentioned below: an oxygen storage capacity of the exhaust gas aftertreatment device, an exhaust gas mass flow of the exhaust gas and a position variable describing a position of the entry point. This has already been pointed out. The oxygen storage capacity describes the ability of the exhaust gas aftertreatment device to temporarily store oxygen. The oxygen storage capacity stands for the maximum amount of oxygen that can be temporarily stored. The exhaust gas mass flow, on the other hand, describes the mass flow of the exhaust gas currently flowing through the exhaust gas aftertreatment device. The position variable relates to the arrangement of the entry point, in particular relative to the exhaust gas aftertreatment device and/or relative to the second lambda sensor.

The correction factor can be determined from the oxygen storage capacity, the exhaust gas mass flow or both the oxygen storage capacity and the exhaust gas mass flow. Taking both parameters into account has a special This has a significant impact on the accuracy of the exhaust aftertreatment model. Additionally or alternatively, the position variable is used, particularly if several sections of the exhaust gas aftertreatment device are modeled.

A further development of the invention provides that the inlet combustion air ratio is determined based on the combustion air ratio and the time derivative. Overall, the inlet combustion air ratio is present as a function of the combustion air ratio, with this being incorporated into the inlet combustion air ratio several times, namely once directly and once in the form of the time derivative.

The inlet combustion air ratio preferably results from the sum of the combustion air ratio and the time derivative of the combustion air ratio, preferably applied to the correction factor. This results in a particularly high accuracy of the inlet combustion air ratio and consequently a high accuracy of the exhaust gas aftertreatment model.

ermitteln, wobei λ₁ das Eintrittsverbrennungsluftverhältnis, λ₂ das Verbrennungsluftverhältnis, k der Korrekturfaktor und t die Zeit ist.For example, the inlet combustion air ratio can be determined using the relationship $${\lambda }_{}$$$${}_1=k\frac{d{\lambda }_2}{dt}+{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="DE102023201660B3\_0002.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}_2$$

determine, where λ ₁ is the inlet combustion air ratio, λ ₂ is the combustion air ratio, k is the correction factor and t is the time.

A further development of the invention provides that the exhaust gas aftertreatment model comprises a plurality of exhaust gas aftertreatment partial models for modeling different sections of the exhaust gas aftertreatment device, with each of the exhaust gas aftertreatment partial models being supplied as input variables with one of several inlet concentrations comprising the inlet concentration and one of several inlet combustion air ratios comprising the inlet combustion air ratio, the respective inlet concentration being supplied and the respective inlet combustion air ratio is determined for one of a plurality of inlet points comprising the inlet point and each of the inlet combustion air ratios is determined from the second measured value independently of the first measured value.

This means that the exhaust gas aftertreatment device is not considered as a whole, but rather the exhaust gas aftertreatment device is divided into several sections. The sections preferably extend from a beginning to an end of the exhaust gas aftertreatment device and particularly preferably directly adjoin one another. For example, the exhaust gas aftertreatment device is divided into at least two, at least three, at least four or - preferably - at least five sections. There is an exhaust gas aftertreatment submodel for each of these sections, with the exhaust gas aftertreatment submodels of the several sections forming the exhaust gas aftertreatment model as a whole.

Each of the exhaust gas aftertreatment submodels has one of the inlet concentrations and one of the inlet combustion air ratios as input variables. The inlet concentration mentioned at the beginning is part of these several inlet concentrations and the inlet combustion air ratio mentioned is part of the several inlet combustion air ratios. The inlet concentration and the inlet combustion air ratio for each section are determined for a respective inlet point of that section.

Using the respective exhaust gas aftertreatment submodel, a respective outlet concentration for an outlet point of the respective section is determined from the respective inlet concentration and the respective inlet combustion air ratio. Preferably, the exit concentration of a section preceding it in terms of flow is used as the inlet concentration of a section immediately following this section in terms of flow. The exhaust gas aftertreatment model is based on a step-by-step calculation of the exit concentration of the at least one exhaust gas component across the exhaust gas aftertreatment device. This allows a particularly high level of accuracy to be achieved.

A further development of the invention provides that one of the inlet combustion air ratios is determined from the second measured value by means of filtering. Basically, all inlet combustion air conditions are determined from the second measured value and independently of the first measured value. Preferably, the procedure already described is used for at least one of the inlet combustion air ratios, so that the corresponding inlet combustion air ratio is determined using the time derivative of the combustion air ratio.

However, at least one other of the inlet combustion air ratios is determined from the second measured value by means of filtering. It is particularly preferred to determine the combustion air ratio from the second measured value again using the probe characteristic curve. This combustion air ratio is then filtered and the result of the filtering used as the inlet combustion air ratio. A low-pass filter in particular is used as a filter.

The inlet combustion air ratio is particularly preferably determined based on the time derivative, provided that the entry point of the respective section is arranged upstream of the second lambda sensor. However, filtering is used if the entry point of the respective section is downstream of the second lambda sensor. Such a procedure enables the use of the method described even when the second lambda sensor is arranged not downstream of the exhaust gas aftertreatment device, but in the exhaust gas aftertreatment device.

The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the statements in this description, wherein the drive device has a drive unit that generates exhaust gas and an exhaust gas aftertreatment device for aftertreatment of the exhaust gas, with a first lambda probe upstream of the exhaust gas aftertreatment device Measured value and a second measured value is measured by means of a second lambda probe downstream of the first lambda probe, and wherein the outlet concentration of at least one exhaust gas component downstream of the exhaust gas aftertreatment device is determined by means of an exhaust gas aftertreatment model, to which an inlet concentration determined for an entry point and an inlet combustion air ratio determined for the entry point are supplied as input variables . The drive device is intended and designed to determine the inlet combustion air ratio from the second measured value independently of the first measured value.

The advantages of such a design of the drive device or such a procedure have already been pointed out. Both the drive device and the method for operating it can be developed in accordance with the statements in the context of this description, so that reference is made to this in this respect.

The features and combinations of features described in the description, in particular the features and combinations of features described in the following description of the figures and/or shown in the figures, can be used not only in the combination specified in each case, but also in other combinations or on their own, without the scope of to abandon invention. Embodiments which are not explicitly shown or explained in the description and/or the figures, but which emerge from the explained embodiments or can be derived from them are therefore also to be considered to be included in the invention.

• 1 eine schematische Darstellung einer Antriebseinrichtung für ein Kraftfahrzeug mit einem Antriebsaggregat und eine Abgasnachbehandlungseinrichtung, sowie
• 2 ein Diagramm, in welchem Verläufe für ein Verbrennungsluftverhältnis über der Zeit aufgetragen sind.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without restricting the invention. This shows:

• 1 a schematic representation of a drive device for a motor vehicle with a drive unit and an exhaust gas aftertreatment device, and
• 2 a diagram in which curves for a combustion air ratio are plotted over time.

The 1 shows a schematic representation of a drive device 1, which has an exhaust gas generating drive unit 2 and an exhaust gas aftertreatment device 3, here in the form of a vehicle catalytic converter. Fuel and fresh gas are supplied to the drive unit 2, which form a fuel-fresh gas mixture and react chemically with one another to produce exhaust gas. The exhaust gas is fed to the exhaust gas aftertreatment device 3 and flows through it in the direction of arrow 4.

Upstream of the exhaust gas aftertreatment device 3, a first measured value is measured by means of a first lambda probe 5 and downstream of the exhaust gas aftertreatment device 3, a second measured value is measured by means of a second lambda probe 6. The two measured values describe a residual oxygen content of the exhaust gas or a combustion air ratio at the respective location.

A lambda controller 7 is operated using the first measured value and a trim controller 8 is operated using the second measured value. Output variables of the two controllers 7 and 8 are offset against a setpoint supplied via an input 9, namely in a calculation module 10. The result of the calculation becomes the composition of the fuel-fresh gas mixture is determined.

Furthermore, the composition of the exhaust gas downstream of the exhaust gas aftertreatment device 3 is determined using an exhaust gas aftertreatment model. This is done for at least one exhaust gas component, but preferably for several exhaust gas components. The exhaust aftertreatment model includes several exhaust aftertreatment submodels, in the exemplary embodiment shown here five exhaust aftertreatment submodels. By means of each of the exhaust aftertreatment One of several sections 11 of the exhaust gas aftertreatment device 3 is calculated using partial models. The sections 11 extend from an inlet 12 to an outlet 13 of the exhaust gas aftertreatment device 3 and directly adjoin one another. The sections 11 extend continuously and uninterrupted from the inlet 12 to the outlet 13.

For each of the sections 11, an inlet concentration and an inlet combustion air ratio are determined, namely at a respective inlet point 14. Using the respective exhaust gas aftertreatment submodel, an outlet concentration of the respective exhaust gas component is subsequently determined at a respective outlet point 15 of the corresponding section 11. Preferably, the inlet concentration for a section 11 located further downstream is used equal to the outlet concentration of the section 11 located immediately upstream. The inlet concentration of the most upstream section 11 is equal to the inlet concentration of the exhaust gas aftertreatment device 3 and the outlet concentration of the exhaust gas aftertreatment device 3 is equal to the outlet concentration of the most downstream section 11.

The exhaust gas aftertreatment model or each of the exhaust gas aftertreatment submodels determines a conversion rate for the respective exhaust gas component depending on the respective inlet combustion air ratio. The conversion rate is stored, for example, in a map or the like, namely for different inlet combustion air conditions. For example, one or more of the following exhaust gas components is used as the exhaust gas component: hydrocarbon, carbon oxide, in particular carbon monoxide, hydrogen, in particular molecular hydrogen, nitrogen oxide, in particular nitrogen monoxide and/or nitrogen dioxide, and oxygen, in particular molecular oxygen.

The respective inlet combustion air ratio is not determined based on the first measured value, but rather from the second measured value independently of the first measured value. In this respect, the inlet combustion air ratio for each of the sections 11 is determined based on a measured value which is measured downstream of the respective inlet point 14. For this purpose, a combustion air ratio is first determined from the second measured value, namely using a probe characteristic curve for the second lambda probe 6. The combustion air ratio determined in this way is derived in time and the time derivation is multiplied by a correction factor. The inlet combustion air ratio is the sum of the inlet combustion air ratio and the result of multiplying the correction factor by the time derivative of the combustion air ratio.

The correction factor is proportional to the oxygen storage capacity and inversely proportional to the exhaust gas mass flow. The position of the respective section 11 of the exhaust gas aftertreatment device 3 is taken into account in the correction factor. The further away the entry point 14 is from the second lambda sensor 6, the greater the correction factor. For example, a position variable included in the correction factor is one for the inlet 12 and zero for the outlet 13 and is determined for the entry points 14 located between the inlet 12 and the outlet 13 by means of linear interpolation. For the five sections 11 shown here, whose entry points 14 are equidistant from one another, this results in position sizes of 1.0, 0.8, 0.6, 0.4 and 0.2. The respective position size is multiplied by the time derivative, for example as part of the correction factor.

The 2 shows a diagram in which curves 16, 17, 18, 19, 20 and 21 describe combustion air conditions over time t. The curve 16 corresponds to a combustion air ratio calculated from the second measured value, the further curves 17 to 21 are derived from this curve 16, namely in the manner described. The curve 16 therefore shows the exit concentration of the at least one exhaust gas component of the most downstream section 11. The curve 17 describes the inlet concentration for this section 11 and correspondingly the outlet concentration of the immediately upstream section 11. The curves 18 to 21 describe the inlet concentrations for the Sections 11 located further upstream. At the latest from the course 21 it becomes clear that the courses 16 to 21 are shown as an example of a sudden change in the composition of the fuel-fresh gas mixture. At a time t ₁ there is a switch from a rich to a lean mixture and at a time t ₂ from the lean to the rich mixture.

REFERENCE SYMBOL LIST:

1

Drive device

2

Drive unit

3

Exhaust gas aftertreatment device

4

Arrow

5

1. Lambda sensor

6

2. Lambda sensor

7

Lambda controller

8th

Trim control

9

Entrance

10

Calculation module

11

Section

12

inlet

13

outlet

14

Entry point

15

Exit point

16

Course

17

Course

18

Course

19

Course

20

Course

21

Course

Claims (10)

Method for operating a drive device (1) for a motor vehicle, which has an exhaust gas-generating drive unit (2) and an exhaust gas aftertreatment device (3) for aftertreatment of the exhaust gas, wherein a first measured value is obtained by means of a first lambda probe (5) upstream of the exhaust gas aftertreatment device (3). and a second measured value is measured by means of a second lambda probe (6) downstream of the first lambda probe (6), and an outlet concentration of at least one exhaust gas component downstream of the exhaust gas aftertreatment device (3) is determined by means of an exhaust gas aftertreatment model, the input variables being one for an entry point (14). determined inlet concentration and an inlet combustion air ratio determined for the inlet point (14) are supplied, characterized in that the inlet combustion air ratio is determined from the second measured value independently of the first measured value. Procedure according to Claim 1 , characterized in that a broadband lambda probe is used as the first lambda probe (5) and/or a jump lambda probe is used as the second lambda probe (6). Method according to one of the preceding claims, characterized in that the second measured value is converted into a combustion air ratio using a probe characteristic curve, from which the inlet combustion air ratio is determined. Procedure according to Claim 3 , characterized in that the inlet combustion air ratio is determined based on a time derivative of the combustion air ratio. Procedure according to Claim 4 , characterized in that the time derivative, subjected to a correction factor describing an influence of the exhaust gas aftertreatment device (3), is used when determining the inlet combustion air ratio. Procedure according to Claim 5 , characterized in that the correction factor is determined as a function of at least one of the following variables mentioned: an oxygen storage capacity of the exhaust gas aftertreatment device (3), an exhaust gas mass flow of the exhaust gas and a position variable describing a position of the entry point. Procedure according to one of the Claims 4 until 6 , characterized in that the inlet combustion air ratio is determined based on the combustion air ratio and the time derivative. Method according to one of the preceding claims, characterized in that the exhaust gas aftertreatment model comprises a plurality of exhaust gas aftertreatment submodels for modeling different sections (11) of the exhaust gas aftertreatment device (3), each of the exhaust gas aftertreatment submodels having as input variables one of several inlet concentrations comprising the inlet concentration and one of several inlet combustion air ratios comprehensive inlet combustion air ratios are supplied, the respective inlet concentration and the respective inlet combustion air ratio being determined for one of several entry points (14) comprising the inlet point (14) and each of the inlet combustion air ratios being determined from the second measured value independently of the first measured value. Procedure according to Claim 8 , characterized in that one of the inlet combustion air ratios is determined from the second measured value by means of filtering. Drive device (1) for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, wherein the drive device (1) has an exhaust gas generating drive unit (2) and an exhaust gas aftertreatment device (3) for aftertreatment of the exhaust gas, by means of a first lambda sensor (5) upstream the exhaust gas aftertreatment device (3) a first measured value and a second measured value is measured by means of a second lambda probe (6) downstream of the first lambda probe (5), and wherein an outlet concentration of at least one exhaust gas component downstream of the exhaust gas aftertreatment device (3) is determined by means of an exhaust gas aftertreatment model, which is as Input variables are supplied with an inlet concentration determined for an inlet point (14) and an inlet combustion air ratio determined for the inlet point (14), characterized in that the drive device (1) is provided and designed to produce the inlet combustion air ratio from the second measured value independently of the first measured value determine.

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