Control system for regulating the exhaust gas recirculation rate using a virtual NOx sensor with adaptation via a NOx sensor

Abstract

Method for adjusting a mass flow rate of an exhaust gas recirculation system of an internal combustion engine taking into account NOx behavior, wherein a control system provides a coupling of a virtual NOx determination with a real NOx control system, and wherein the control system operates an inner and an outer cascade, wherein the inner cascade uses a lambda probe, while the outer cascade uses a real NOx sensor.

Description

[0001] The present invention relates to a method for adjusting the exhaust gas recirculation of an internal combustion engine taking into account NOx behavior, and to a diesel commercial vehicle internal combustion engine with at least one exhaust gas recirculation.

[0002] It is known that a portion of the exhaust gas is recirculated to reduce nitrogen oxide emissions in diesel engines. This is intended to reduce the oxygen concentration at the engine intake. The recirculation rate of this exhaust gas recirculation influences, among other things, the charge air temperature and the boost pressure, which is generated by turbocharging, particularly in large commercial vehicles. Especially in large commercial vehicles, there is a desire to directly measure and control nitrogen oxide and particulate emissions. While NOx sensors are already in series production, particulate sensors are still under development.A control system based on a signal from the NOx sensor is possible, but a problem can arise because the sensor signal generated in this way cannot show the current nitrogen oxide value under dynamic operating conditions, but only a delayed nitrogen oxide value.

[0003] DE 103 16 112 A1 discloses a method for operating a self-igniting internal combustion engine, wherein the method includes the determination of a mean gas temperature and its gradient and further provides for the determination of a raw nitrogen oxide emission from this and a control of the internal combustion engine for the purpose of reducing the nitrogen oxide emissions.

[0004] DE 101 26 580 A1 also describes a control system based on an engine model, whereby the control system includes a virtual or a real NOx sensor.

[0005] US 2003 / 0 216 855 A1 teaches a method for controlling NOx emissions of an engine, whereby a NOx model is used for control, which is adapted based on an evaluation of calculated NOx values, for example with the aid of a neural network.

[0006] DE 10 2005 032 623 A1 discloses a method for determining cylinder-selective NOx and soot particle emissions of a diesel engine.

[0007] DE 101 53 322 A1 teaches an EGR control system for a diesel engine which estimates changes in the oxygen density of the exhaust gas caused by an adjustment of the EGR valve, whereby a correction is carried out on the basis of a comparison of the estimated oxygen density with a target value.

[0008] JP 2005 180 219 A teaches a method for determining the NOx generation of an engine using a model and for fitting the model using experimentally determined values.

[0009] The object of the present invention is to enable a control system that takes into account a time delay caused by a NOx sensor.

[0010] This problem is solved by a method having the features of claim 1 and by a diesel commercial vehicle internal combustion engine having the features of claim 16. Further advantageous embodiments and developments are specified in the respective dependent claims.

[0011] It is proposed that a method for adjusting the exhaust gas recirculation of an internal combustion engine be implemented taking into account NOx behavior. This method involves a control system that couples a virtual NOx determination with a real NOx control system. The control system operates an inner and an outer cascade, with the inner cascade utilizing a lambda sensor and the outer cascade utilizing a real NOx sensor. This method can be particularly advantageously implemented in a specific diesel commercial vehicle internal combustion engine, which is also proposed. This engine includes at least exhaust gas recirculation, turbocharging, a diesel particulate filter, a catalytic converter, a NOx sensor, and a first control system for adjusting the exhaust gas recirculation rate to achieve a specific NOx value.A first control system comprises first control means that simulate a virtual NOx sensor, second control means that perform an adapted control of the virtual NOx sensor, and third control means that implement NOx control, wherein the first control system is structured such that the virtual NOx sensor provides a preset for the first control system, and wherein the first control system is structured, for example, as a higher-level outer control cascade that has a second, inner control cascade with a faster control time than that of the outer control cascade.

[0012] The proposed method aims to enable the control of an exhaust gas recirculation (EGR) mass flow rate. EGR mass flow rate is preferably used as the controlled variable. Controlling the EGR flow rate offers the advantage of faster response times compared to adjusting the boost pressure. However, boost pressure adjustment can be integrated into an overall control system. For example, the oxygen content in the intake manifold of the internal combustion engine is determined by adjusting the EGR mass flow rate, preferably measured at an inlet point. A virtual sensor, preferably a corresponding NOx model, analyzes a virtual oxygen content, which may have been corrected by an adapted value, allowing a virtual NOx value in the exhaust gas to be inferred.Using the lambda sensor in the inner cascade enables a faster signal flow. The lambda sensor is less sluggish than the real NOx sensors currently on the market.

[0013] An adaptation is performed, for example, with regard to the NOx model used. This model preferably has adaptive components. A further adaptation can be made, for example, in the area of ​​determining a mass flow rate. For instance, a mass loading model can be adapted. Preferably, the mass loading model is based on a cylinder mass. Its adaptation results in a more precise determination of the necessary values, particularly compared to a single cylinder filling derived from overall measurements. If, for example, an exhaust gas recirculation model is used, it can also have an adaptation according to one embodiment. Furthermore, it is possible to integrate a particle model, for example, a particulate filter model. This makes it possible, for example, to set a particle concentration in the exhaust gas.Preferably, the particle concentration in the exhaust gas is taken into account within the control system and can thus lead to an adjustment of the NOx limit value. According to a further development, the proposed particle model can also consider the particulate filter loading. From this, a strategy for regenerating a particulate filter can be derived. For example, the model can calculate when regeneration should be carried out from an NOx perspective. It is also possible to consider smoke development caused by particles during operation. The model or control system can define limit values ​​for smoke levels, particulate filter loading, and particle concentration in the exhaust gas, which are then taken into account.

[0014] The proposed combination of nitrogen oxide (NOx) control based on a virtually calculated fast NOx signal and adaptation of this virtual NOx signal via a NOx sensor offers the advantage of combining the transient benefits of virtual NOx control with the increased accuracy of direct control based on the NOx signal from a NOx sensor. Furthermore, it is proposed that a control variable for the NOx control be determined using a virtual NOx sensor. It is also advantageous to compare a virtual NOx-dependent control variable with a NOx setpoint determined from a characteristic map. For example, an exhaust gas recirculation (EGR) mass flow rate is used as a manipulated variable for a virtually determined NOx control variable. Further acceleration of the controller response is possible by utilizing an exhaust gas recirculation model.The exhaust gas recirculation (EGR) model can be present one or more times, depending in particular on whether the internal combustion engine has both low-pressure and high-pressure EGR systems. Preferably, the respective EGR model is calibrated in a quasi-steady-state operating condition of the internal combustion engine using a signal from the NOx sensor. This has the advantage that the EGR model can then be self-learning. On the one hand, necessary corrections are made during the calibration, and on the other hand, a base of learned values ​​is preferably increased. Based on these learned values, the EGR model can interpolate and extrapolate.The exhaust gas recirculation model can, for example, rely on simulation techniques of neural network technology, on fuzzy models, but especially also on systems of equations that result from the internal combustion engine, the components present or connected therein, and quantities determined via system boundaries.

[0015] The regulation further stipulates that a PID controller is used to regulate a virtually determined NOx value. Firstly, this allows existing control systems that already incorporate a PID controller to be expanded by integrating the virtual NOx sensor. Secondly, the use of the PID controller enables a particularly rapid response in transient situations.

[0016] It has proven advantageous to adjust a virtually determined NOx control variable within the framework of an adapted control system. Preferably, the adapted control system uses a real NOx sensor. However, the adaptation is suspended, for example, during rapid load changes. It has been found that the dynamics are often too high for the adapted control system to be able to provide a reasonable adjustment of the virtually determined NOx control variable. According to a further development, however, it is planned that an adaptation should also be performed during rapid load change reactions. This can, for example, be carried out in a mirrored system and the applicability of the adaptation checked after the load change(s). Thus, for example, an adaptation can be suspended for transients in the actual control system.By comparing the values ​​determined without adaptation and the virtual values ​​obtained in the mirrored system with adaptation, appropriate learning algorithms can be used to ensure that a certain level of performance is achieved in the mirrored system. This allows the control system to utilize the adapted model determined in the mirrored system, even during rapid load changes, provided a minimum level of performance is reached. The adaptation function preferably uses a real NOx sensor, but can also utilize other sensors or data.

[0017] The lambda sensor is primarily used to perform a calibration of air quality measurements. For example, the exhaust gas recirculation (EGR) model can simulate an airflow at various locations. The lambda sensor can be used to calibrate these virtually determined values. The external cascade is primarily used to calibrate NOx measurements. Here, the values ​​determined by the actual NOx sensor can be compared with those used or determined in the EGR model or by the virtual NOx sensor. In particular, the external cascade ensures that the model-based values ​​remain verifiable.

[0018] In addition to this configuration, a cascade control system has also proven effective, in which the outer cascade reacts faster than the inner cascade. For example, a real NOx sensor can be used in the inner cascade, while virtually determined values, preferably oxygen values, are used in the outer cascade.

[0019] In addition to cascade control, it is also possible to use pre-control, either as a supplement or instead of cascade control. For example, the model-generated virtual signal can provide an initial adjustment of the NOx value, which is then further processed by the corresponding control system using the values ​​from the actual NOx sensor. Furthermore, a manipulated variable, such as an auxiliary manipulated variable, can be applied, as can an auxiliary controlled variable. It is also possible to implement a follow-up control system with feedforward control, particularly by applying the derivative of the respective reference variables.

[0020] Another design involves placing a lambda sensor in the air path, for example, in the intake manifold. This allows for the measurement of the oxygen content upstream of the combustion engine. While this can still be calculated using a model, it is not strictly necessary. If a model is used to determine the oxygen content, such as a virtual oxygen sensor, it can also be adapted to the lambda sensor readings. Furthermore, a special lambda sensor, particularly suitable for cold starts, can be used in the air path or exhaust system. These are preferably wideband lambda sensors, especially improved wideband lambda sensors currently under development. The lambda sensor may, for example, incorporate a heating element.It can, for example, be structured and / or operated in the manner shown in DE 10 2004 057929 A1, which is referenced in the disclosure.

[0021] A preferred application of the method is particularly evident in a diesel commercial vehicle engine. With regard to this commercial vehicle internal combustion engine, it is preferably provided that the method includes means for determining the oxygen concentration at an engine inlet of the diesel internal combustion engine and for determining the oxygen content of a recirculated exhaust gas. This allows the model to be calibrated or, by directly determining correlations, a correlation of the nitrogen oxide concentration in the exhaust gas to be calculated. Such a correlation is, for example, found in the dissertation by OE Hermann at RWTH Aachen University. This dissertation is entitled "Emission Control in Commercial Vehicle Engines via the Air and Exhaust Gas Path." Reference is made to this dissertation regarding the correlation within the scope of this disclosure.The same applies to the basic structure of a control system with respect to a signal from a real NOx sensor, as can also be seen in this dissertation. In particular, reference is also made to an EGR controller, which is also described therein.

[0022] Preferably, the adaptation is designed to adjust one or more control models to align virtually determined values ​​of the models in the control system of the diesel commercial vehicle's internal combustion engine. These models are connected to a signal flow from both the lambda sensor and a NOx sensor. This enables continuous adjustment and, by utilizing the learning function, improved performance of the diesel commercial vehicle's internal combustion engine. A further development provides that the data determined, particularly by the model and the learning function, can also be read out. If this is implemented for multiple identical diesel commercial vehicle internal combustion engines, this data can be combined and merged into a single data set through appropriate processing, in particular by weighting the data against each other.This data set can then be stored as a default setting in new diesel commercial vehicle internal combustion engines.

[0023] Advantages and further features of the invention are explained in more detail below with reference to the drawings. However, the features described therein are not limited to the embodiment shown. Nor are the figures to be interpreted restrictively. Rather, the features shown therein can be combined with other features in other embodiments, as well as with those of the features described above, to form further developments not detailed here. The figures show: Fig. 1: A schematic view of a diesel commercial vehicle internal combustion engine with actuators and sensors, Fig. 2: a schematic overview of an adaptation of an EGR mass flow via a lambda sensor, Fig. 3: a schematic view of an adaptation of a NOx model via a NOx sensor, and Fig. 4: A schematic view of mass flow determination using a mass loading model.

[0024] Fig. Figure 1 shows a schematic representation of an internal combustion engine, in particular a diesel commercial vehicle internal combustion engine 1, with its associated connected components, sensors, and actuators. The diesel commercial vehicle internal combustion engine has a high-pressure exhaust gas recirculation system 2 and a low-pressure exhaust gas recirculation system 3. Various sensors or devices are installed in an air supply 4 to the diesel commercial vehicle internal combustion engine 1. Sensor locations or sensors are located in the Fig. Figure 1 with outlined numbers further clarifies this. When air is drawn in through the diesel commercial vehicle combustion engine 1, it can be measured directly at the point of entry by an air mass sensor 5, in particular a hot-film air mass sensor. If, as shown, the low-pressure exhaust gas recirculation 3 is present, additional exhaust gas is supplied from there. This may necessitate the provision of another air mass sensor 5. Preferably, a cooler 7 is arranged in the low-pressure exhaust gas recirculation 3 in addition to a control valve 6. This cools the recirculated exhaust gas to a temperature sufficient for a compressor 8 of an exhaust gas turbocharger to provide a sufficient compressed air mass flow to the combustion engine. A cooler 7 is preferably located downstream of the compressor 8 to dissipate the heat generated in the gas during compression.The cooled gas stream can then be supplied with further exhaust gas, cooled via a suitable cooler, through a further control valve 6 via the high-pressure exhaust gas recirculation (EGR) system 2. Additional sensors, which record parameters for control, are preferably arranged at an engine inlet 9. Exhaust gas from the diesel commercial vehicle combustion engine 1 can then be discharged, with a partial mass flow being supplied to the high-pressure EGR system 2 or the low-pressure EGR system 3. Furthermore, a main flow of the exhaust gas is used via a turbine 10 of the exhaust gas turbocharger to drive the compressor 8. Instead of an exhaust gas turbocharger, another type of boost pressure charging can also be used. For this purpose, for example, a mechanical supercharger or other means can be employed. Downstream of the turbine 10 are a diesel particulate filter 11 and a catalytic converter 12. For the sake of simplicity, only the diesel particulate filter 11 is shown.Furthermore, a NOx sensor and a lambda sensor are also located in the exhaust system.

[0025] The from Fig. The diesel commercial vehicle internal combustion engine 1 is used in the proposed method as follows: The EGR control concept preferably provides the illustrated combination of high-pressure EGR and low-pressure EGR, but can alternatively also be implemented with a separate high-pressure EGR or low-pressure EGR. The exhaust gas concentration is measured in the exhaust gas downstream of turbine 10 using a NOx sensor at position 2 in the circuit. The condition of the exhaust gas, in particular its density, is measured upstream of control valve 6, the high-pressure EGR valve, via an exhaust pressure sensor at position 3 in the circuit and an exhaust gas temperature sensor at position 4 in the circuit. A boost pressure P2 is measured with a boost pressure sensor at position 6 in the circuit. The position of the SEGR valve in control valve 6 of the high-pressure exhaust gas recirculation system 2 is determined.An EGR mass flow rate can then be calculated using the exhaust gas density upstream of the valve and the differential pressure between P3 and P2 across the valve. Furthermore, an air consumption model, not described in detail here, is available. This model is fed the boost pressure P2 and an intake manifold temperature T2, at positions 6 and 7 respectively in the circuit. From this, the air consumption model can calculate an engine mass flow rate. If low-pressure and high-pressure EGR are present, as shown, the low-pressure EGR mass flow rate must also be calculated or measured. If, however, no low-pressure EGR is present, the EGR rate and the fresh air mass flow rate can also be calculated using the air consumption model. A low-pressure EGR mass flow rate is determined by a differential pressure measurement DP at position 8 in the circuit. For this purpose, a pressure drop across an orifice in the exhaust stream of the low-pressure EGR path is preferably determined.Alternatively, an air mass meter upstream of the low-pressure EGR inlet (position 10 in the circle) and an air mass meter downstream of the low-pressure EGR inlet (position 11 in the circle) can be used. The low-pressure EGR rate can then be calculated from these measurements. If an air mass meter is present, the high-pressure exhaust gas recirculation model can potentially be omitted, and a high-pressure exhaust gas recirculation rate can be calculated from a fresh air mass flow measured at position 11 in the circle and an engine mass flow rate from an air consumption model. For example, an exhaust gas recirculation rate can also be determined using a model such as the one described in DE 102 42 234 A1, to which reference is made in this regard.

[0026] Using the sensors and models described above, it is possible to calculate the exhaust gas recirculation rate and, by utilizing the oxygen content of the recirculated exhaust gas, to calculate the oxygen concentration of the gas supplied to the internal combustion engine. The oxygen content of the recirculated exhaust gas can be determined, for example, at position 2 in the circuit, based on a lambda signal from the NOx sensor. Using the oxygen concentration at the engine inlet 9, a nitrogen oxide concentration in the exhaust gas can be calculated via correlations described in the dissertation cited above. Reference is made to the dissertation within the scope of this application regarding this correlation. With the provided setup, it is thus possible to operate an adaptive NOx controller with high-pressure and low-pressure exhaust gas recirculation. For this purpose, a virtual NOx signal is determined using a model.This is used as a control variable and compared with a NOx setpoint. This setpoint is preferably derived from a characteristic map, depending on engine speed and load. A conventional PID controller is then used to control any deviation of the virtual NOx signal from the setpoint. One manipulated variable of the PID controller is a desired EGR mass flow rate. This can be converted into a corresponding target EGR valve position using the EGR model. The EGR model takes into account, among other things, the condition of the respective EGR valve and can thus provide compensation for, for example, changing pressure upstream of the turbine. An internal position control of the EGR valve regulates the valve position and reports the actual position back to the EGR model, which in turn calculates the current actual EGR mass flow rate.An EGR controller structure can thus include an EGR model, a NOx model, and, connected to it, the internal combustion engine and the corresponding data streams between them. The pressures P2 and P3, as well as the TEGR temperature and the SEGR position value, are fed into the EGR model. The air consumption model, in turn, receives the temperature T2, a value from the lambda sensor, and the pressure P2. The EGR model provides the EGR mass flow rate determined by the model. The air consumption model calculates further values ​​from this, in particular a mass flow rate supplied to the internal combustion engine, an exhaust gas / air ratio, and values ​​from the NOx sensor. From this, the NOx model determines a virtual NOx signal. This is provided to the PID controller, which receives the virtual NOx signal combined with a desired NOx value. The desired NOx value as an input signal is derived from a characteristic map.From this, the PID controller determined a mass flow rate of the exhaust gas recirculation, from which the actuation range of the respective exhaust gas recirculation valve is derived via the EGR model.

[0027] The from Fig. The resulting virtual EGR rate, referred to there as the "virtual EGR rate", can thus be calculated via a mass flow balance. The virtual EGR rate on the high-pressure side is calculated using a model. Such an approach also makes it possible, in particular, to eliminate the need for an air mass meter.

[0028] A possible EGR control structure, as well as its respective adaptation within the framework of the EGR or NOx model, is explained in more detail below. However, this is only one of several ways in which a control system can be implemented.

[0029] Fig. Figure 2 shows a schematic view of an adaptation of an EGR mass flow via a lambda sensor. This adaptation is designed as follows: The data from the air requirement model, here referred to as the "engine-in-mass model", are fed into an air requirement model. Fig. The EGR model, referred to here as the "EGR model", incorporates the values ​​P2, P3, TEGR, and SEGR. The EGR model for low-pressure exhaust gas recirculation incorporates the pressure difference DP and the position SEGR. LPLP stands for "low pressure". Below the EGR model for low-pressure exhaust gas recirculation, a lambda sensor and the values ​​determined by the sensors located there are shown schematically. The control system is designed so that the mass flows determined from the respective models are linked and processed. To be able to capture the transient range within the control system, a learning function, referred to here as an "adaptive learner", is integrated. The virtually determined mass flows can be adjusted using this learning function. As described above, Fig. As already mentioned, the EGR mass flow rate recirculated in the low-pressure exhaust gas recirculation system is virtually determined and adapted via the learning function. This value is incorporated into the high-pressure exhaust gas recirculation model, which, in turn, is linked to the air consumption model to obtain the virtually determined mass flow rates for air and the exhaust gas recirculation rate. This results in a virtual lambda value, a virtual oxygen content, and an exhaust gas recirculation rate. These are the results that can now be transferred from the virtual exhaust gas recirculation models and the air mass sensors into the NOx model.

[0030] Fig. Figure 3 shows an adaptation of the NOx model based on the values ​​determined by the NOx sensor. The results are derived from... Fig. 2 determined virtual values ​​air consumption λ virtual virtual EGR rate X EGR, virtual and the virtual oxygen fraction Ψ O2,virtualis used, for example, to determine a virtual oxidation air ratio λ Ox , virtual to determine this. This is incorporated into a particle model. From this, a particle concentration C can be determined. PM can be determined in the exhaust gas. From the mole fraction Ψ O2, virtual Taking into account an adapted difference in the amount of oxygen, a corrected mole fraction of oxygen Ψ is calculated. O2, virtual, corrected The NOx is fed into a NOx model. From this, a virtual mole fraction of NOx can then be determined. The formula for determining the virtually corrected oxygen mole fraction is derived from the following: Fig. 3 emerging relationship. From the virtual oxygen molar fraction and the over a rotational speed N engineA target value for an oxygen mole fraction is applied to a load q defined by a characteristic curve. The same process is performed for a NOx mole fraction as a target value from a characteristic curve, whereby this value is also compared with the NOx mole fraction determined by the NOx sensor. While the comparison of the oxygen mole fraction yields a difference in the NOx mole fraction as a model-based, quickly determined value from a correlation, the comparison of the NOx mole fractions from the characteristic curve and from the NOx sensor results in a second difference value. These two values ​​are compared and then provided to a learning function. From this, an adjusted NOx value is then provided to an inverse correlation, from which a difference value for the oxygen mole fraction in the form of ΔΨ is derived. O2, adaptThe correlation preferably used here is derived from the aforementioned dissertation, in particular from equation 2-3 given on page 7. The determined difference value is then compared with the virtually determined oxygen mole fraction and corrected. This corrected value is then fed into the NOx model, from which the virtual NOx mole fraction Ψ is derived. NOx, virtual The aim here is that the NOx value determined by the NOx sensor provides an actual description of the condition and corresponds as closely as possible to the value that is defined as the NOx mole fraction Ψ. NOx, virtualThis could ultimately be determined using the NOx model. Due to the virtually faster availability of values, as well as the use of the learning function and thus the adaptation, a faster and, in particular, more precise adjustment of the mass flow at the exhaust gas recirculation system is possible in order to maintain the desired nitrogen oxide and particulate matter values.

[0031] Fig. Figure 4 shows another example, particularly in reference to the one from Fig. 2 emerging system, for determining mass flows using a mass loading model of a cylinder. In addition to the use of the individual models, the following also occurs in the Fig.4. The resulting implementation involves adjusting the mass loading from the "Engine-in Mass Model" via a depicted adaptation. The value determined in this way is then used to obtain a virtual air value. Simultaneously, this is linked to a virtual EGR mass flow and a load, so that the subsequent module calculates the virtual values ​​for air consumption λ. virtual the virtual EGR rate X EGR, virtual and the virtual oxygen fraction Ψ O2, virtual can determine.

[0032] Each figure illustrates various parameters, input and output variables, and logic operations. These are not explicitly described in detail but can be understood from the figures as shown. The figures and their contents are not meant to be restrictive but rather to serve as examples. Therefore, parts of the logic operations, parameters, input and output variables can be modified, omitted, or supplemented. Furthermore, new schemes can be created from individual parts or sections, including parameters, logic operations, and input and output variables, which can then be used to execute the process and configure the control system.

Claims

[1] Method for adjusting a mass flow rate of an exhaust gas recirculation system of an internal combustion engine taking into account NOx behavior, wherein a control system provides a coupling of a virtual NOx determination with a real NOx control system, and wherein the control system operates an inner and an outer cascade, wherein the inner cascade uses a lambda probe, while the outer cascade uses a real NOx sensor. [2] Method according to claim 1, characterized by , that a control variable of the NOx control is determined by means of a virtual NOx sensor. [3] Method according to claim 1 or 2, characterized by , that a virtual NOx-dependent control variable is compared with a NOx setpoint determined from a characteristic map. [4] Method according to claim 1, 2 or 3, characterized by , that an EGR mass flow is used as a control variable for a virtually determined NOx control variable. [5] Method according to any one of the preceding claims, characterized by that the regulation relies on an exhaust gas recirculation model. [6] Method according to any one of the preceding claims, characterized by , that an exhaust gas recirculation model of the control system is calibrated in a quasi-stationary operating state of the internal combustion engine using a signal from a real NOx sensor. [7] Method according to any one of the preceding claims, characterized by that the system uses a PID controller to regulate a virtually determined NOx value. [8] Method according to any one of the preceding claims, characterized by , that a virtually determined NOx control variable is adjusted within the framework of an adapted control system. [9] Method according to claim 8, characterized by that the adapted control system uses a real NOx sensor. [10] Method according to claim 9, characterized by that the inner cascade performs a comparison of an air determination. [11] Method according to claim 9 or 10, characterized by that the outer cascade performs a comparison of a NOx determination. [12] Method according to any one of the preceding claims 8 to 11, characterized by , that it is checked whether a prerequisite for the application of an adaptation of the regulation still exists and, if it is determined that the prerequisite no longer exists, the adaptation of the regulation is suspended. [13] Method according to any one of the preceding claims, characterized by that virtual NOx determination is faster than determining a NOx value using a real NOx sensor. [14] Method according to any one of the preceding claims, characterized by , that a parameter characterizing a particle flow is determined using a virtually determined oxygen content. [15] Application of a method according to one of the preceding claims to a diesel commercial vehicle engine. [16] Diesel commercial vehicle internal combustion engine with at least one exhaust gas recirculation, a boost pressure charging system, a diesel particulate filter, a catalyst, a NOx sensor and a first control system with respect to an exhaust gas recirculation rate for setting a NOx value, wherein the first control system comprises first control means that simulate a virtual NOx sensor, second control means that perform an adapted control of the virtual NOx sensor, and third control means that implement NOx control, wherein the first control system is designed such that the virtual NOx sensor provides a preset for the first control system, wherein the first control system is designed as a higher-level outer control cascade that includes a second, inner control cascade with a faster or slower control time than that of the outer control cascade. [17] Diesel commercial vehicle internal combustion engine according to claim 16, characterized by, that means are provided for determining an oxygen concentration at an engine inlet of the diesel internal combustion engine and for determining an oxygen content of a recirculated exhaust gas. [18] Diesel commercial vehicle internal combustion engine according to one of claims 16 or 17, characterized by , that an adaptation is provided for adjusting one or more models of the control system to match virtually determined values ​​of the models, wherein the adaptation is connected to a signal flow from the lambda probe as well as from a real NOx probe. [19] Diesel commercial vehicle internal combustion engine according to any one of claims 16 to 18, characterized by that low-pressure exhaust gas recirculation and / or high-pressure exhaust gas recirculation are provided, each of which is stored as a model in the regulation.

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