DE102020200365A1 - Method for correcting a differential pressure signal for a mass flow - Google Patents

Abstract

Method for correcting a differential pressure signal for a mass flow, wherein a characteristic map with at least two interpolation points for correcting the differential pressure signal is stored in a control unit (100) for the differential pressure signal, with a deviation depending on a temperature being stored for each interpolation point, with an actual temperature (TIst) is determined at the location of a differential pressure sensor (50), an actual deviation (ΔIst) for the differential pressure signal depending on the actual temperature (TIst) at the location of the differential pressure sensor (50) being determined, depending on the actual temperature (TIst) a second deviation (ΔKenn) is determined from the map, with a new deviation (Δnew) being determined as a function of the determined actual deviation (ΔIst) and the second deviation (ΔKenn) determined from the map, the new deviation being determined (Δnew) is taken over as a deviation in the map for the current actual temperature (Tact), with a mass flow (ṁair) is determined as a function of the new deviation (Δnew) for the differential pressure signal.

Description

State of the art

The invention is based on a method and a device for correcting a differential pressure signal of a sensor according to the preamble of the independent claims.

It is known that the drift that occurs over the service life of a hot film air mass meter installed in an air supply to an internal combustion engine is corrected as a reference value by comparing the signal from the hot film air mass meter with an air mass value modeled from a charge pressure, a charge air temperature and an engine speed.

The DE 10 2005 025 884 A1 discloses a method and a device for correcting a signal of a sensor ( 1 ), which provides the most accurate possible drift compensation of a characteristic curve of the sensor ( 1 ) enable. At least one characteristic variable of the sensor signal ( 1 ) compared with a reference value. The signal from the sensor ( 11 ) is corrected depending on the comparison result. As a reference value, a signal from the sensor ( 1 ) Derived value for the at least one characteristic variable of the sensor signal ( 1 ) educated.

Disclosure of the invention

In a first aspect, a method for correcting a differential pressure signal for a mass flow is presented, a characteristic map with at least two support points for correcting the differential pressure signal being stored in a control device for the differential pressure signal, with a deviation depending on a temperature being stored for each support point an actual temperature is determined at the location of a differential pressure sensor, an actual deviation for the differential pressure signal being determined as a function of the actual temperature at the location of the differential pressure sensor, a second deviation being determined from the characteristic map as a function of the actual temperature, wherein in Depending on the determined actual deviation and the second deviation determined from the map, a new deviation is determined, the new deviation being adopted as a deviation in the map for the current actual temperature, with a mass flow depending on the new deviation for the Differential pressure signal is determined.

The method has the particular advantage that the temperature dependency of the differential pressure signal can be transferred directly to a characteristic diagram by determining the new deviation, and a direct correction can thus be carried out.

Furthermore, the differential pressure signal can correspond to a dynamic pressure, in particular a difference between a total pressure at a stagnation point of the differential pressure sensor and a static pressure.

Furthermore, if the new deviation exceeds a first threshold value, the new deviation is limited. Limiting the new deviation is advantageous in order to limit deviations that are too large and possibly implausible. This increases the robustness of the method.

The new deviation is advantageously limited by a predeterminable first step size. By using a specifiable first step size, a maximum change can be made for the deviation. This increases the robustness of the method against unexpected and therefore implausible changes in the deviation.

Furthermore, a minimum temperature difference between the actual temperature and each temperature of the support points can be calculated and the determined temperature of the support point can be adapted with the minimum distance to the actual temperature as a function of the actual temperature.

Using this method step, the interpolation point closest to the actual temperature is determined and its temperature position is then adjusted to the new actual temperature. By adapting the map with current temperature and deviation data, an optimized correction for the determined differential pressure can be made over the long term. External influences such as the change of seasons and / or local temperature changes can thus be robustly covered.

Furthermore, the actual temperature can be adopted as the new temperature for the support point. By adapting the temperature for the support point, an optimized correction for the determined differential pressure signal can be made over the long term. External influences such as the change of seasons and / or local temperature changes can thus be robustly covered.

Furthermore, if the minimum temperature difference exceeds a second threshold value, the new temperature for the support point can be limited. The limitation has the advantage that changes in the temperature that are too great, in particular due to incorrect measurements, can be restricted. This increases the robustness of the method.

It is advantageous that the new temperature for the support point is limited by a specifiable temperature for the new temperature of the support point, the limitation being performed by adding or subtracting the specifiable temperature with the temperature of the support point determined from the map. It is advantageous to predetermine a temperature that can be specified, since this can limit changes to the new temperature of the interpolation point that are too rapid. This increases the robustness of the method.

It is advantageous that the number of support points is not increased. This has the particular advantage that memory resources in the control unit remain the same due to the constant number of support points for the characteristic diagram. Another advantage is that the values at the individual support points are updated more frequently with current values.

Furthermore, the actual deviation for the differential pressure signal can be carried out in an operating state in which the internal combustion engine is not started. Determining the actual deviation for the differential pressure signal in an operating state in which the internal combustion engine has not started has the advantage that the expected differential pressure signal is known precisely because there is no mass flow at the location of the differential pressure sensor. A temperature-dependent offset signal for the differential pressure sensor can thus be determined in a simple manner.

In further aspects, the invention relates to a device, in particular a control device and a computer program, which are set up, in particular programmed, to execute one of the methods. In yet another aspect, the invention relates to a machine-readable storage medium on which the computer program is stored.

Description of the exemplary embodiments

• 1 eine schematische Darstellung einer Verbrennungskraftmaschine mit Hochdruck-Abgasrückführung,
• 2 einen beispielhaften Ablauf des Verfahrens zur Korrektur eines Differenzdrucksignals für einen Massenstrom.

The invention is described in more detail below with reference to the accompanying drawings and on the basis of exemplary embodiments. Show it

• 1 a schematic representation of an internal combustion engine with high pressure exhaust gas recirculation,
• 2 an exemplary sequence of the method for correcting a differential pressure signal for a mass flow.

The 1 shows a schematic representation of a motor vehicle 1 with an internal combustion engine 2 , the air via an air duct system 61 is supplied and exhaust gas via an exhaust gas discharge 71 can be traced back.

In the air supply system 61 is in the direction of air flow 51 seen the following arranged: A compressor 30th of an exhaust gas turbocharger 6th , an intercooler 40 , a differential pressure sensor 50 , especially a Pressure Based Air Flow Meter Sensor (PFM sensor) 50 , a throttle valve 60 and an internal combustion engine 2 . The air mass sensor 50 is included as a Pressure Based Air Flow Meter Sensor 50 formed, which can determine a total pressure at the stagnation point of the PFM sensor p _tot , a temperature T _sens at the location of the sensor in the intake manifold and a static pressure p _s . Furthermore, a cross-sectional area A _{eff of} the intake manifold pressure section in which the pressure-based air flow meter sensor 50 is built into the control unit 100 saved.

In the exhaust gas discharge 71 is based on the internal combustion engine 2 in the direction of flow of the exhaust gas 52 Arranged as follows: an exhaust gas turbine 70 , an exhaust aftertreatment system 80 . The exhaust aftertreatment system 80 can z. B. include various exhaust gas cleaning systems, such. B. a three-way catalyst, a particulate filter and a nitrogen oxide catalyst.

Upstream of the exhaust turbine 70 , ie on a high pressure side of the exhaust system 71 , branches from the exhaust system 71 a high pressure exhaust gas recirculation line 47 (HP-EGR line) from the upstream of the internal combustion engine 2 and the downstream of the throttle 60 in the fresh air system 61 flows out. Downstream of the internal combustion engine 2 are located along the HP-EGR line 47 a high pressure EGR cooler 43 , a temperature sensor 44 , a pressure sensor 45 and a HP EGR valve 46 . By means of z. B. the temperature sensor 44 can be a temperature T _EGR between the HP EGR cooler 43 and the HP EGR valve 46 to be determined. Furthermore, by means of the pressure sensor 45 a pressure p _EGR between the HP EGR valve 46 and the HP EGR cooler 43 be determined. The sizes described can, for. B. are available as sensor values or as model values. The recirculation of exhaust gas serves to reduce the peak temperatures in the combustion chamber of the internal combustion engine 2 .

mit Δp dem Differenzdruck, p_tot dem Gesamtdruck am Staupunkt am Körper des PFM-Sensors 50, p_s dem statischen Druck, R der allgemeinen Gaskonstante, T der Temperatur und A_eff dem effektiven Querschnitt des Saugrohrdruckabschnitts, in dem der PFM-Sensor 50 verbaut ist. Der Differenzdruck Δp ergibt sich aus der Differenz zwischen dem Gesamtdruck am Staupunkt p_tot des PFM-Sensors 50 und dem statischen Druck p_s. Der Differenzdruck Δp kann entweder durch zwei Sensoren oder eine gemeinsame Sensormembran ermittelt werden.The air mass flow ṁ _air can be calculated using the well-known Bernoulli equation using the Pressure Based Air Flow Meter Sensor 50 can be calculated as follows: $$\begin{array}{l}{\dot{m}}_{\text{air}}=\sqrt{\frac{2\cdot \Delta \text{p}\cdot p_s}{\mathrm{R.}\cdot T}}\cdot {\mathrm{A.}}_{eff}\\ mit\Delta {\text{p = p}}_{\text{dead}}-p_s\end{array}$$

with Δp the differential _{pressure, p tot} the total pressure at the stagnation point on the body of the PFM sensor 50 , p _{s is} the static pressure, R is the general gas constant, T is the temperature and A _{eff is} the effective cross section of the intake manifold pressure section in which the PFM sensor 50 is installed. The differential pressure Δp results from the difference between the total pressure at the stagnation point p _{tot of} the PFM sensor 50 and the static pressure p _s . The differential pressure Δp can be determined either by two sensors or a common sensor membrane.

2 shows a function diagram to illustrate the method. In a first step 500 a release condition for the procedure is checked. The correction method is released when there is an operating state for the internal combustion engine such that the motor vehicle 1 is started that the internal combustion engine 10 but not running or being fired. Alternatively or additionally, the operating state is also present when there is no mass flow in the air duct system 61 and / or in the exhaust gas discharge 71 is present. If the release condition is met, the process is carried out in one step 510 continued.

Is the release condition from the step 510 is not met, the procedure in step 500 started over. If the release condition is met, step 510 using the PFM sensor 50 a current differential pressure signal and the current actual temperature T _{Ist are} determined and sent to the control unit 100 transferred and saved. The actual temperature T _ist is preferably measured with a temperature sensor, which is in the PFM sensor 50 is installed, determined. The determined differential pressure signal corresponds to the actual deviation Δ _ist for the PFM sensor 50 for the actual temperature T _ist .

Then in one step 520 as a function of the actual temperature T _Ist, a second deviation Δ _Kenn from one on the control unit 100 stored map determined. The map has support points with associated temperatures for correcting the differential pressure signal. The deviations for the characteristic map are preferably determined in a test phase for the differential pressure sensor 50 , especially for the PFM sensor 50 , be determined. Alternatively, the deviations for the characteristic map can be stored for all support points during initial start-up of the system. It is advantageous if a currently determined actual deviation is stored for all support points. The map contains at least two support points.

In one step 530 a first amount of the difference between the actual deviation Δ _Ist and the second deviation Δ _{Kenn is} determined. If the absolute value of the difference exceeds a predeterminable first threshold value S _1, the actual deviation Δ _{is new} as a new deviation Δ in the control unit 100 saved.
If the first amount of the difference exceeds the predeterminable threshold value S ₁ , acceptance of the actual deviation Δ _{ist is newly} limited for the new deviation Δ. The limitation can be carried out, for example, using a specifiable first step size x _{1 in} such a way that the first step size x _{1 is} added or subtracted from the second deviation Δ _Kenn.
The first step size x _{1 is added} to the second deviation Δ _Kenn if the actual deviation Δ _{Ist is} greater than the second deviation Δ _Kenn . The result of this addition is then shown as a new deviation Aneu in the control unit 100 saved. If the actual deviation Δ _{ist is} smaller than the second deviation Δ _Kenn , a subtraction of the first step size x ₁ with the second deviation Δ _{Kenn is} carried out and a new deviation Δ _new in the control unit 100 saved.

In one step 540 a minimum temperature difference between the actual temperature T _ist and each temperature of the support points is determined from the characteristics map and the determined temperature T _{support of} the support point is determined with the minimum distance from the actual temperature T _ist .

In one step 550 a second amount of the difference between the actual temperature T _actual and the temperature T _{support of} the support point with the minimum distance from the actual temperature T _{actual is} determined. If the second amount of the difference falls below a predeterminable second threshold value S ₂ , the actual temperature T _{Ist is adopted} as the new temperature T _New for the support point with the minimum difference to the actual temperature T _Ist . The support point shifts accordingly.
If the second amount of the difference exceeds the predeterminable threshold value S ₂ , acceptance of the actual temperature T _ist for the temperature T _{support of} the support point is limited.
The limitation can be carried out, for example, using a predeterminable second step size x _{2 in} such a way that the temperature T _{support of} the support point with the minimum distance from the actual temperature T _{actual is} added or subtracted with the second step size x _2.

The second step size x _{2 is added} to the temperature T _{support of} the support point if the actual temperature T _{ist is} greater than the temperature T _{support of} the support point. The result of the addition is then used as the new temperature T _New in the control unit 100 saved.
If the actual temperature T _{ist is} less than the temperature T _{support of} the support point, a subtraction of the second step size x ₂ from the temperature T _{support of} the support point is carried out and as a new temperature T _new in the control unit 100 saved.
Then in one step 560 the air mass flow ṁ _air as a function of the corrected map for the internal combustion engine 10 can be determined and fed to a control system, for example.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102005025884 A1 [0003]

Claims (13)

Method for correcting a differential pressure signal for a mass flow, wherein a characteristic map with at least two interpolation points for correcting the differential pressure signal is stored in a control unit (100) for the differential pressure signal, with a deviation depending on a temperature being stored for each interpolation point, with an actual temperature (T _actual ) is determined at the location of a differential pressure _{sensor (50), an actual deviation (Δ actual} ) for the differential pressure signal depending on the actual temperature (T _actual ) at the location of the differential pressure sensor (50) being determined, depending on the actual temperature (T _actual) is determined, a second deviation (Δ _{characteristic)} from the map, wherein the determined in dependence actual deviation _(Δ), and the from the map determined second deviation (Δ _{characteristic)} a new deviation (Δ _new ) is determined, the new deviation (Δ _new ) being taken over as a deviation in the map for the current actual temperature (T _actual ), where at a mass flow (ṁ _air ) depending on the new deviation (Δ _new ) for the differential pressure signal is determined. Procedure according to Claim 1 , characterized in that the differential pressure signal corresponds to a dynamic pressure, in particular a difference between a pressure at a stagnation point of the differential pressure sensor and a static pressure. Method according to one of the preceding claims, characterized in that if the new deviation (Δ _new ) exceeds a first threshold value (S ₁ ), the new deviation (Δ _new ) is limited. Procedure according to Claim 3 , characterized in that the limitation of the new deviation (Δ _new ) is carried out by a predeterminable first step size (x ₁ ). Method according to one of the preceding claims, characterized in that a minimum temperature difference between the actual temperature (T _Ist ) and each temperature of the support points is calculated and the determined temperature (T _support ) of the support point with the minimum distance to the actual temperature (T _{Actual ) is} adjusted depending on the actual temperature (T Ist). Procedure according to Claim 5 , characterized in that the actual temperature (T _actual ) is adopted as the new temperature (T _new ) for the support point. Procedure according to Claim 6 , characterized in that when the minimum temperature difference (Δ _Tmin ) exceeds a second threshold value (S ₂ ), the new temperature (T _new ) is limited for the support point. Procedure according to Claim 7 , characterized in that the new temperature (T _new ) for the support point is limited by a second step size (x ₂ ) for the new temperature (T _new ) of the support point, the limitation being carried out by adding or subtracting the second support point ( x ₂ ) is carried out on the temperature (T _support ) of the support point determined from the characteristics map. Method according to one of the preceding claims, characterized in that the number of support points is not increased. Method according to one of the preceding claims, characterized in that the actual deviation (Δ _actual ) for the differential pressure signal is carried out in an operating state in which the internal combustion engine (10) is not started. Computer program which is set up to implement a method according to one of the Claims 1 to 10 perform. Electronic storage medium with a computer program according to Claim 11 . Device, in particular control device (100), which is set up to implement a method according to one of the Claims 1 to 10 to execute.

Images