DE10327055A1 - Determining exhaust feedback mass flow of internal combustion engine involves deriving it from measured fresh air mass flow using adapted cylinder mass flow characteristic - Google Patents

Abstract

The method involves determining the characteristic of the cylinder mass flow (dmZYL) of the gas mixture fed to at least one cylinder of the engine (1), which depends on various engine operating parameters, and measuring the fresh air mass flow. The characteristic is adapted to the known fresh air mass flow (dmHFM) for various engine operating points and the exhaust feedback mass flow (dmAGR) is derived from the measured fresh air mass flow using the adapted characteristic. Independent claims are also included for the following: (a) a method of determining model parameters of a model for a physical parameter of an internal combustion engine (b) an arrangement for determining the exhaust feedback mass flow of an internal combustion engine (c) and an arrangement for determining model parameters of a model for a physical parameter of an internal combustion engine.

Description

The The present invention relates to a method and a device for determining the exhaust gas recirculation mass flow an internal combustion engine, such as a diesel engine. Especially The present invention relates to such a method and Such a device, wherein with the help of the thus obtained information about the exhaust gas recirculation mass flow the exhaust gas recirculation rate correct can be determined.

Farther The present invention relates to a method and a device for determining model parameters of a model for physical Sizes like for example, the exhaust gas recirculation mass flow or a cylinder mass flow in an internal combustion engine. With a such model can the physical quantities in dependence determined by measured operating parameters of the internal combustion engine without direct measurement.

For a particular Emission-optimal control of an internal combustion engine, eg. B. one charged diesel engine, the exact knowledge of one is possible huge Number of operating parameters of the engine system of decisive Importance. Such an operating parameter is in an internal combustion engine with exhaust gas recirculation, for example the exhaust gas recirculation mass flow, d. H. the mass flow of the exhaust gas discharged from the internal combustion engine, which over an exhaust gas recirculation line fed to a mixing point where the exhaust gas is mixed with fresh intake air the resulting fresh air / exhaust gas mixture the combustion chambers of Supply combustion engine. Also the so-called exhaust gas recirculation rate, i.e. the quotient of the intake fresh air mass flow and the exhaust gas recirculation mass flow, is for Compliance with emission regulations is important.

One other operating parameters or a physical size, which for the Control of the internal combustion engine is relevant, for example the cylinder filling. A model showing the cylinder filling and other sizes in the fresh air and / or exhaust tract of the internal combustion engine in dependence of (to be measured) operating parameters is also called filling model designated.

Currently is the exhaust gas recirculation mass flow measurable only with expensive or short-lived sensors. Empirical or physically based models with which the exhaust gas recirculation mass flow derived from other operating parameters of the engine system can, have an insufficient accuracy.

such Models for determining a physical quantity, such as exhaust gas recirculation mass flow, typically include a number of model parameters based on individual measurements this physical quantity in dependence be adjusted by respective values of the operating parameters, so that the model depends on the behavior of the respective physical quantity from the operating parameters via a desired one Area as possible exactly describes. Such a model can be represented by a function y (a →, x →) where y is the physical quantity, the vector a → as components the n model parameters and the vector x → as components the operating parameters contains. In principle, such a model can also do more than a physical one Describe size, y (a →, x →) would then designate several physical quantities.

This results in each of the individual measurements an equation. By solving the equation system resulting from all these measurements from m equations y i = y (a →, x → i i = 1 ... m (1) In this case, the model parameters are determined, where y _{i are} the values of the physical variable measured at respective operating parameters x → _i and m is the number of measurements.

With a correspondingly large number of measurements (in particular if m> n, ie the number of measurements exceeds the number of model parameters), the system of equations ( 1 ) overdetermined. Since the measurements are generally associated with a certain measurement error, this leads to contradictions in the solution of the equation system ( 1 ).

This problem has been solved by either ignoring a corresponding number mn of equations or, equivalently, fitting a corresponding number of equations in this way was that the contradictions are eliminated and the system of equations ( 1 ) was clearly solvable.

This has disadvantages, in particular, if the different measurements y _{i were obtained} from sensors of different accuracy or at operating points of different accuracy. By simply ignoring (or adjusting) a certain number of measurements, it may be that even the most inaccurate measurements ultimately determine the model. Failure to ignore the most inaccurate or, in the case of dynamic value changes, slowest measurements will degrade the accuracy or dynamics of the model over ideal processing of the measurement data.

Also the determination of the exhaust gas recirculation rate is in conventional Procedure strongly erroneous.

Implicitly, the total or cylinder _{mass flow dm.sub.zyl taken} in the respective cylinder or combustion chamber of the internal combustion engine is first determined for its determination by means of test bench _measurements from various operating _parameters . For this purpose, as an operating parameter in particular the pressure and the temperature in the connection (the so-called intake manifold) between the aforementioned mixing point and the cylinder and the injection quantity of the air / fuel mixture and the engine speed in question, wherein the test bench measurements of the cylinder mass flow, which in principle the sum of the fresh air mass _flow dm _HFM and the exhaust gas recirculation mass _flow dm _AGR is determined as a function of these operating parameters in the form of a characteristic map, ie it is known at which operating parameter values which cylinder mass flow occurs. The aspirated fresh air mass flow is measured by means of an air mass sensor, such as a hot-film air mass sensor in the intake. The exhaust gas recirculation _{mass flow} dm _AGR results from the cylinder _{mass flow} dm _cyl and the fresh air _{mass flow} dm _HFM measured during operation as the difference: dm AGR = dm cyl - dm HFM (2)

The sought exhaust gas recirculation rate r _EGR then follows by quotient formation: r AGR = dm AGR /dm HFM (3)

Just the completeness It should be noted that the actual implementation is true something may differ from the procedure described above however basically attributed to this algorithm.

The method described above is sensitive to tolerances of the measurement signals and production-related tolerances of the inlet area. A difference of the absolute errors of the two specific mass flows dm _HFM and dm _cyl is directly in the exhaust gas recirculation mass flow dm _AGR , which is determined as a relatively small difference of two relatively large sizes and therefore with high sensitivity, for example, the error in the detection of the cylinder mass flow dm _cyl essentially composed of manufacturing _{tolerances of} the charge air path and measurement errors of the boost pressure and charging temperature sensor, while the error in the detection of the fresh air mass flow dm _HFM essentially due to measurement error of the air mass sensor. An error of -5% in the determination of the cylinder _{mass flow} dm _cyl and an error of + 5% in the determination of the fresh air _{mass flow} dm _HFM erroneously provide an additional exhaust gas recirculation _{mass flow} dm _AGR of 10% of the fresh air _{mass flow} .

Thus, not only the exhaust gas recirculation mass _flow dm _AGR but also the exhaust gas recirculation rate r _{AGR is} determined to be faulty, and future stricter exhaust gas determinations may not be met.

Of the The present invention is therefore based on the object, a method and a correspondingly designed device for determination the exhaust gas recirculation mass flow to provide an internal combustion engine, which one possible accurate determination of the exhaust gas recirculation mass flow and in particular one possible accurate determination of the exhaust gas recirculation rate is possible.

Farther The present invention is based on the object, a method and provide a corresponding device with the model parameters a model for an internal combustion engine as possible can be determined exactly.

These Tasks are performed according to the invention a method having the features of claim 1 or 7 or a Device with the features of claim 16 or 18 solved. The under claims each define preferred and advantageous embodiments of the present invention.

to Determination of exhaust gas recirculation mass flow is according to the invention as in the conventional one described above Procedure of fresh air mass flow measured to depend on it Evaluation of the cylinder mass flow, which the exhaust gas recirculation mass flow and the fresh air mass flow includes the exhaust gas recirculation mass flow to be determined during operation of the internal combustion engine. It will However, during operation, the cylinder mass flow in dependence descriptive of various operating parameters of the internal combustion engine Characteristic which is e.g. before commissioning of the internal combustion engine through test bench measurements has been determined, so at the for various operating points the internal combustion engine measured and thus known fresh air mass flow adapted, i. adapted that the above equation (2) the bis to a percentage error of measuring the fresh air mass flow used air mass meter correct exhaust gas recirculation mass flow in the appropriate Operating points. In principle, can also on the previous ones test bench measurements be waived. The starting values for the characteristic are arbitrary and only affect the duration of the adaptation.

With Help this adapted characteristic of the cylinder mass flow and the measured fresh air mass flow can then reliably the Exhaust gas recirculation mass flow be determined, in contrast to the above-described State of the art Fault in the charge air temperature sensor, the boost pressure sensor or manufacturing tolerances of the charge air passage during operation of the respective Vehicle automatically be calibrated out and thus in no the specific gas mass flows to enter more. In addition, responding to a driver's request faster because of a very fast adaptation of the required operating parameters the internal combustion engine possible is, i. The present invention not only allows for increased static Reliability, but also improved dynamic operation.

There the characteristic of the cylinder mass flow is adjusted in such a way that the percentage error of the cylinder mass flow and the fresh air mass flow is the same size also has the exhaust gas recirculation mass flow the same percentage error. In the quotient formation for determining the exhaust gas recirculation rate this percentage error cut out and thus eliminated, so that the exhaust gas recirculation rate according to the invention in principle can be determined without errors.

to Determining model parameters of a model for a physical quantity, such as for example, the cylinder mass flow, in an internal combustion engine, where the model is the physical quantity depending on the model parameters and operating parameters of the internal combustion engine is proposed according to the invention, at least one value of the physical quantity for at least one set of Measure values of the operating parameters and the model parameters so to determine that a measure of error, which is a deviation of the at least one measured value of physical size of one corresponding by the model with each the same sentence value of the physical value determined from values of the operating parameters Size describes is minimized.

The Measuring the at least one value of the physical quantity can doing so directly or indirectly during the operation of the internal combustion engine or for example also before the installation of the internal combustion engine in a motor vehicle on a appropriate test bench respectively.

Preferably, the sum of the squares of the differences of the at least one measured value and the corresponding value determined by the model is used as the error measure. If, as in equation system (1) above, y represents the model, y _i measured values of the physical quantity at values x → _{i of} the operating parameters and a → the model parameters, where the index i runs from 1 to m and m indicates the number of measurements, Thus, the error measure F results in:

The use and minimization of such a measure of error is also referred to as a least squares method. Then, with a minimum of the error measure F, depending on the model parameters, the derivative of F must disappear according to the model parameters. Thus, the following equation system can be set up for the model parameters:

The summation in equation (5) can also be realized with the aid of low-pass filtering. As a result, old values are "forgotten" as a result of continuous measurement of new measuring points y _i and an adaptation to changing characteristics of the internal combustion engine can thus be achieved.

Be y (a →, x → _i) by a weighting factor b _i multiplied to different accuracies of the values of y _i to be considered - In addition, each difference y _i can. This is particularly advantageous when the measurements y _i originate from sensors with different accuracy and / or different dynamics, since measurement errors of different magnitudes can thus be taken into account.

The Model is preferably linear in the model parameters. This is in particular the equation system (5) a linear system of equations, which be solved using known algorithms such as the Gauss algorithm can. For example, the model may have a polynomial in the operating parameters, but also a hyperbolic series or a sum of harmonic ones Functions, depending on whether an aperiodic or periodic physical size described becomes. The model parameters then each represent the coefficients represents.

The But the model does not have to be in the form of an explicit equation it can also be a characteristic that depends on the model parameters act.

Of the completeness half it should be noted that the two previously described Invention aspects of the determination of the exhaust gas recirculation mass flow and the determination the model parameters are in principle independent of each other, but of course also used in combination in an engine control unit for an internal combustion engine can be.

The The present invention will become more apparent by referring to the attached drawings explained with reference to a preferred embodiment.

The single figure shows a simplified representation of a simulation model for simulating the gas flow in a motor vehicle or a corresponding internal combustion engine according to the present invention.

In the figure is an internal combustion engine 1 shown with four combustion chambers or cylinders. The internal combustion engine 1 is coupled to an exhaust gas turbocharger (ATL), which is a turbine 2 and a compressor 7 includes, the turbine 2 and the compressor 7 on a common wave 14 , the so-called turbocharger shaft, are mounted. The turbine 2 uses the exhaust gas of the internal combustion engine 1 contained energy to drive the compressor 7 which sucks in fresh air via an intake tract and precompressed air into the individual combustion chambers of the internal combustion engine 1 suppressed. The sucked fresh air mass flow is from a relatively far in front arranged in the intake air mass meter 6 measured and thus during operation of the internal combustion engine 1 or of the motor vehicle. The one by the turbine 2 , the compressor 7 and the turbocharger shaft 14 formed exhaust gas turbocharger is fluidly with the internal combustion engine only by the air and exhaust gas mass flow 1 coupled.

The of the compressor 7 sucked in and pre-compressed fresh air is via a charge air cooler (LLK) 8th , which reduces the exhaust gas temperature and thus the NO _x emission as well as the fuel consumption, a so-called replacement volume (ERS) 9 fed. By reducing the exhaust gas temperature in the intercooler 8th The air is compressed by oxygen enrichment, but without increasing the pressure. The individual combustion chambers of the internal combustion engine 1 is an inlet collector (ELS) 10 upstream. That in the combustion chambers of the internal combustion engine 1 generated exhaust gas is from an exhaust gas collector (ASA) 11 collected and the turbine 2 fed. The turbine 2 is in the exhaust gas flow direction the exhaust system (APU) 12 downstream of the motor vehicle, which the pollutant components during operation of the internal combustion engine 1 degrades resulting exhaust gases and derived the remaining exhaust gases as quietly as possible. Part of the in the combustion chambers of the internal combustion engine 1 generated exhaust gas is from the exhaust gas collector 11 via exhaust gas recirculation (EGR) 16 with an exhaust gas recirculation valve 17 to the inlet collector 10 recycled, where the recirculated exhaust gas mixed with the intake fresh air and the fresh air / exhaust gas mixture to the corresponding cylinder of the internal combustion engine 1 is supplied.

Furthermore, there is a control unit 4 which is a component of a corresponding engine management system of the motor vehicle. From the controller 4 various sizes or operating parameters of the illustrated engine system are monitored, which are detected by means of corresponding sensors and via an interface 3 the control unit 4 be supplied. This may be in particular the from the air mass meter 6 measured fresh air mass flow, the engine speed, the density of the fresh air / exhaust gas mixture in the connection between the inlet header 10 and the internal combustion engine 1 , the so-called intake manifold, etc. act. The way this is from the controller 4 acquired measured variables are evaluated in order to generate different control signals for the engine management system dependent thereon. As indicated in the figure, the over the interface 3 from the controller 4 output control signals, for example, the duty cycle of arranged in the exhaust gas recirculation exhaust gas recirculation valve 17 , the vane adjustment 15 the turbine 2 or also the injection time and the injection quantity of the into the individual combustion chambers of the internal combustion engine 1 via an injection system 5 control injected air-fuel mixture etc.

With the reference numerals 13 are in 1 Designated arranged in corresponding air or gas paths valves.

Before commissioning of the internal combustion engine 1 is by test bench _measurements a map or a characteristic of the cylinder mass flow dm _cyl , ie the mass flow of the intake _manifold 10 , which has the mixing point for the fresh air and the recirculated exhaust gas, the individual cylinders of the internal combustion engine via the designated as a suction pipe connecting line supplied fresh air / exhaust gas mixture, determined in dependence on various operating parameters of the internal combustion engine. As has been described initially, the cylinder _{mass flow} dm _{cyl is} known to _depend , inter alia, on the intake manifold pressure, the intake manifold _temperature , the density in the intake manifold and the engine speed. The cylinder _{mass flow} dm _cyl can thus be modeled as follows: dm cyl = f (p 0 , p 1 , p 2 , ..., a 0 , a 1 , a 2 , ...) (6)

In this case, p ₀ , p ₁ , p _{2 designate} different measured values or operating parameters which enter into the model, while a ₀ , a ₁ , a _{2 designate} model parameters or coefficients which describe the model. The physical relationship of the individual operating parameters and coefficients need not necessarily be known as an equation. It is also sufficient only the presence of a mapable in a polynomial characteristic or a map or Kennraums.

During operation of the internal combustion engine 1 or the corresponding motor vehicle is continuously the fresh air mass flow dm _HFM of the air mass meter 6 measured and the control unit 4 fed. In the control unit 4 is the previously described characteristic of the cylinder _{mass flow} dm _cyl stored, so that this characteristic to the control unit 4 is known.

The control unit adapts this characteristic during operation so that at each operating point of the internal combustion engine 1 at known values of the exhaust gas recirculation mass _flow dm _AGR, the above equation is satisfied.

Thus, for example, the fresh air mass _flow dm _{HFH can} always be measured if that in the exhaust gas recirculation 16 included exhaust gas recirculation valve 17 is closed, so that applies: dm _AGR = 0. In this case, adapted the controller 4 the characteristic of the cylinder _{mass flow} dm _cyl such that for each operating point of the internal combustion engine 1 if possible: 0 = dm cyl - dm HFM , ie dm cyl = dm HFM (7)

Of the Relationship according to equation (7) is sought as described. However, this is due to random error in certain circumstances not reachable, at least not for all measurements in the overdetermined Case, so that therefore a statistical method, e.g. the method of least squares, can be used to the standard deviation to the right of the left equation side of equation (7) minimize.

wobei der Index i die i-te Messung von insgesamt m Messungen bezeichnet. Daraus kann wiederum gemäß Gleichung (5) durch Ableiten ein Gleichungssystem zur Bestimmung der einzelnen Modellparameter ermittelt werden. Entsprechende Algorithmen zum Aufstellen und Lösen des Gleichungssystems sind dabei beispielsweise in dem Steuergerät 4 implementiert.Such an overdetermined case occurs, for example, when the illustrated measurement of the fresh air _{mass flow} dm _HFM and the equation (7) associated measurement of the cylinder _{mass flow} dm _cyl is repeated so often that the number of measurements the number of parameters a ₀ , a ₁ , ... exceeds. According to equation (4), an error measure F then results as the expression to be minimized, namely

where the index i denotes the i-th measurement of a total of m measurements. This can in turn according to Equation (5) can be determined by deriving an equation system for determining the individual model parameters. Corresponding algorithms for setting up and releasing the equation system are, for example, in the control unit 4 implemented.

However, the adjustment of the characteristic curve of the cylinder mass flow can also with open exhaust gas recirculation valve 17 carried out, since, for example, methods are known from certain measured operating parameters of the internal combustion engine 1 determine the instantaneous value of exhaust gas recirculation mass _flow dm _AGR . Important for the _above- described adjustment of the characteristic curve of the cylinder _{mass flow} dm _cyl is in principle only that the most reliable or estimated information about the valid in the respective operating point value of Abgasrückführmassenstroms dm _AGR independent of the previously described, possibly faulty sensors, in particular independent of the air mass meter 6 , are known. At least the degree of unreliability of the information used should be known.

The adjustment of the characteristic curve of the cylinder _{mass flow} dm _cyl can, for example, be carried out by corresponding adaptation of the coefficients a ₀ , a ₁ , a ₂ ... _Of the model according to equation (6) during operation.

When _adjusting the characteristic curve for the cylinder _{mass flow} dm _cyl , the above equation (2) using this adjusted characteristic curve for all operating conditions, in particular for relatively small exhaust gas recirculation _rates, provides up to a possibly existing percentage error of the hot-film air mass meter 6 corrected mass flow through the inlet valve. An additional error due to the difference formation according to equation (2) no longer occurs, so that the exhaust gas recirculation mass flow dm _AGR at each operating point only the percentage error of the hot-film air mass meter 6 having. Failure of a charge air _{temperature sensor} , a boost pressure sensor or manufacturing tolerances of the charge air route, which as described conventionally can lead to errors in the determination of the cylinder _{mass flow} dm _cyl , automatically by the above adjustment method in the operation of the motor vehicle by the control unit 4 eliminated or calibrated out and no longer enter into any of the specific mass flows, as long as the display of the participating sensors remains unique.

The previously described balancing method is also particularly advantageous with regard to the determination of the exhaust gas recirculation rate r _AGR according to equation (3). Since the characteristic curve of the cylinder _{mass flow} dm _cyl as described is just adjusted so that the percentage error of the cylinder _{mass flow} dm _cyl and the fresh air _{mass flow} dm _{HFM are} equal, also derived according to equation (2) derived from exhaust gas recirculation _{mass flow} dm _AGR the same percentage error. In the quotient formation according to equation (3) for determining the exhaust gas recirculation rate r _AGR , this percentage error is reduced and is thus eliminated, ie the exhaust gas recirculation rate r _AGR can be determined without errors in principle.

1

internal combustion engine

2

turbine

3

interface

4

control unit

5

injection

6

Hot-film air mass meter

7

compressor

8th

Intercooler

9

spare volume

10

Inlet header

11

Outlet header

12

exhaust system

13

Valve

14

turbocharger shaft

15

Guide Vane the turbine

16

Exhaust gas recirculation line

17

Exhaust gas recirculation valve

dm _AGR

Exhaust gas recirculation mass flow

dm _HFM

Fresh air mass flow

dm _cyl

Cylinder mass flow

Claims (20)

Method for determining the exhaust gas recirculation mass flow of an internal combustion engine, fresh air having an exhaust gas recirculation ( 16 ) recirculated exhaust gas of the internal combustion engine ( 1 ) and the resulting gas mixture at least one cylinder of the internal combustion engine ( 1 ), wherein for determining the exhaust gas recirculation mass flow (dm _EGR ) of the exhaust gas recirculation ( 16 ) recirculated exhaust gas one of various operating parameters of the internal combustion engine ( 1 ) dependent characteristic of the cylinder _{mass flow} (dm _cyl ) of the at least one cylinder of the internal combustion engine ( 1 ) and the fresh air _{mass flow} (dm _HFM ) of the fresh air is measured, characterized in that the characteristic of the cylinder _{mass flow} (dm _cyl ) at the for various operating points of the internal combustion engine ( 1 ) Known fresh-air mass flow (dm _HFM) is adjusted and that the exhaust gas recirculation mass flow (dm _EGR) as a function of which, in a respective instantaneous operating point of the internal combustion engine ( 1 ) measured fresh air _{mass flow} (dm _HFM ) using the adjusted characteristic of the cylinder _{mass flow} (dm _cyl ). A method according to claim 1, characterized in that the characteristic curve of the cylinder mass flow in such a way for the various operating points of the internal combustion engine ( 1 is adapted for each of these operating points at least one known exhaust gas recirculation _{mass flow} at least approximately the relationship dm _AGR = dm _cyl - dm _HFM , where dm _EGR the known exhaust gas recirculation _{mass flow} , dm _cyl the cylinder _{mass flow} according to the adjusted characteristic and dm _HFM each referred to known fresh air mass flow. A method according to claim 2, characterized in that the characteristic of the cylinder mass flow in such a way for the various operating points of the internal combustion engine ( 1 ) is adapted for each of these operating points at a known exhaust gas recirculation _{mass flow} of zero, the relationship dm _zyl = dm _HFM applies. Method according to one of the preceding claims, characterized in that from the exhaust gas recirculation mass flow (dm _EGR ) and the respectively measured fresh air mass _flow (dm _HFM ) determined by the method in each case by quotient formation, the exhaust gas recirculation rate of the exhaust gas recirculation ( 16 ) recirculated exhaust gas is determined. Method according to one of the preceding claims, characterized in that the characteristic of the cylinder _{mass flow} (dm _cyl ) during operation of the internal combustion engine ( 1 ) is adjusted. Method according to one of the preceding claims, characterized in that the exhaust gas recirculation mass flow in each operating point of the internal combustion engine ( 1 ) is determined from the adapted characteristic curve for the cylinder _{mass flow} and the fresh air _{mass flow} respectively measured at this operating point according to the relationship dm _AGR = dm _cyl - dm _HFM , where dm _EGR the exhaust gas recirculation _{mass flow} to be determined, dm _cyl the cylinder _{mass flow} according to the adapted characteristic and dm _HFM the respectively measured fresh air mass flow. Method for determining model parameters of a model for a physical quantity ( _dmzyl ) of an internal combustion engine, the model representing the physical quantity ( _dmzyl ) as a function of the model parameters and operating parameters of the internal combustion engine, wherein at least one value of the physical variable ( _dmzyl ) is measured at at least one set of values of the operating parameters, characterized in that the model parameters are determined such that an error measure representing a deviation of the at least one measured value of the physical quantity ( _dmzyl ) from a corresponding one by the model Set of values of the operating parameters determined value of the physical quantity (dm _zyl ) is minimized. Method according to claim 7, characterized in that that as the error measure the Sum of the squares of the differences between the at least one measured value and the corresponding value determined becomes. Method according to claim 7 or 8, characterized that as the error measure the Sum of the squares of multiplied by a respective weighting factor Dif differences between the at least one measured value and the corresponding determined value is used, wherein the weighting factor dependent is determined by a measurement error of the respective measured value. Method according to one of claims 7 to 9, characterized that by deriving the error measure according to the model parameters a system of equations for the determination of the model parameters is created. Method according to claim 8 or 9 and claim 10, characterized in that a sum in the equation system is formed by means of a low-pass filtering. Method according to one of claims 7 to 11, characterized in that a number of the measured values of the physical quantity (dm _zyl ) is greater than a number of the model parameters. Method according to one of claims 7 to 12, characterized that the model is linear in the model parameters. Method according to one of claims 1 to 6 and one of claims 7 to 12, characterized in that the characteristic of the cylinder _{mass flow} (dm _cyl ) is the model and the cylinder _{mass flow} (dm _cyl ) is the physical quantity. A method according to claim 14, characterized in that the measurement of the cylinder _{mass flow} (dm _cyl ) takes place indirectly via a measurement of the fresh air _{mass flow} (dm _HFM ). Device for determining the exhaust gas recirculation mass flow of an internal combustion engine, fresh air having an exhaust gas recirculation ( 16 ) recirculated exhaust gas of the internal combustion engine ( 1 ) and the resulting gas mixture at least one cylinder of the internal combustion engine ( 1 ), with fresh air mass flow measuring means ( 6 ) for measuring the fresh air mass _flow (dm _HFM ) of the fresh air, and with exhaust gas recirculation mass flow determining means ( 4 ) for determining the exhaust gas recirculation mass flow (dm _EGR ) of the exhaust gas recirculation ( 16 ) recirculated exhaust gas, wherein the exhaust gas recirculation mass flow determination means ( 4 ) are configured such that they the exhaust gas recirculation mass flow on the basis of one of various operating parameters of the internal combustion engine ( 1 ) dependent characteristic of the cylinder _{mass flow} (dm _cyl ) of the at least one cylinder of the internal combustion engine ( 1 ) supplied gas mixture and on the basis of the fresh air mass flow measuring means ( 6 ) measured fresh air mass _flow (dm _HFM ), characterized in that the exhaust gas recirculation mass flow determination means ( 4 ) are configured such that they the characteristic of the cylinder _{mass flow} (dm _cyl ) to the for various operating points of the internal combustion engine ( 1 ) Known adjust fresh air mass flow (dm _HFM) and the exhaust-gas recirculation mass flow (dm _EGR) as a function of which, in a respective instantaneous operating point of the internal combustion engine ( 1 ) measured fresh air _{mass flow} (dm _HFM ) using the adjusted characteristic of the cylinder _{mass flow} (dm _cyl ). Apparatus according to claim 16, characterized in that the exhaust gas recirculation mass flow determining means ( 4 ) are configured for carrying out the method according to one of claims 1-6 or 14-15. Device for determining model parameters of a model for a physical quantity ( _dmzyl ) of an internal combustion engine, the model representing the physical quantity ( _dmzyl ) as a function of the model parameters and operating parameters of the internal combustion engine, the device _comprising at least one measuring device ( 6 ) for determining a value of the physical quantity ( _dm.sub.zyl ) as a function of at least one set of values of the operating parameters, characterized in that the apparatus further comprises an evaluation device ( 4 ) which is configured to determine the model parameters such that an error measure representing a deviation of the at least one measured value of the physical quantity ( _dm.sub.zyl ) from a corresponding one respectively by the model with the corresponding set of values of the operating parameters determined value of the physical quantity (dm _zyl ) is minimized. Device according to claim 18, characterized in that that the device is carrying of the method according to any one of claims 7 to 15 is configured. Device according to one of claims 16-18, characterized in that the evaluation device in a control unit ( 4 ) of the internal combustion engine is integrated.