Method for determining an effective prevailing uncertainty value for an emission value for a given time point when operating a drivetrain of a motor vehicle

Abstract

The invention relates to a method for determining an effective prevailing uncertainty value (304, 305) for an emission value (301, 302) for a given time point when operating a drivetrain (100) of a motor vehicle with an internal-combustion engine (110), wherein, at different times (n), one prevailing emission value (301) and one prevailing uncertainty value (303) are determined for the emission value, wherein the effective prevailing uncertainty value (304, 305) for the given time point is determined from prevailing uncertainty values (303) and prevailing emission values (301) prior to the given time point.

Claims

1. A method for determining an effective prevailing uncertainty value (304, 305) for an emission value (301, 302) for a given time point when operating a drivetrain (100) of a motor vehicle with an internal-combustion engine (110), the method comprising: determining, for the emission value (301,302) at an initial phase (0<t<t.sub.0) immediately after starting the internal-combustion engine (t>0), prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are tolerances of a computational model (130, 132) determining the prevailing emission values (301), determining, for the emission value (301,302) at different times (n) following the initial phase, prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are respective tolerances of a sensor (112, 121, 123, 127) or the computational model (130, 132) determining the prevailing emission values (301), determining the effective prevailing uncertainty value (304, 305) for the given time point based on the prevailing uncertainty values (303) and the prevailing emission values (301) prior to the given time point, controlling operation of the drivetrain (100) by outputting a control value to the drive train (100) based on the effective prevailing uncertainty value (304, 305).

2. The method according to claim 1, wherein the effective prevailing uncertainty value (304, 305) for the given time point is determined based on the prevailing uncertainty values (303) weighted with the respective prevailing emission values (301) before the given time point.

3. The method according to claim 1, wherein the effective prevailing uncertainty value (304, 305) for the given time point is determined based on at least one selected from a group consisting of: a sliding average, a weighted average, and exponential smoothing.

4. The method according to claim 1, wherein the effective prevailing uncertainty value (304, 305) is used for the given time point upon an actuation of the drivetrain (100) and/or upon an evaluation of the prevailing emission value.

5. The method according to claim 4, the method further comprising: wherein a prevailing actual value of an emission component is the prevailing emission value (301), determining a regulation range (201) of the emission component, wherein the regulation range (201) includes a minimum value range (202) and a maximum value range (203), wherein the maximum value range (203) is an upper limit and based on a maximum value (203a), wherein the minimum value range (202) is determined is a lower limit and based on a minimum value (202a), and regulating an actual value of the emission component to a target value by outputting the control value to the drivetrain (100) when an actual value of the emission component is in the regulation range (201) above the minimum value range (202) and below the maximum value range (202), wherein the effective prevailing uncertainty value (304, 305) is below the maximum value range, and/or wherein the effective prevailing uncertainty value (304, 305) is above minimum value range (202).

6. The method according to claim 5, the method further comprising: outputting a maximum control value to the drivetrain (100) when the actual value is at least in the maximum value range (203), and/or outputting a minimum control value to the drivetrain (100) when the actual value is at most within the minimum value range (202).

7. The method according to claim 1, wherein the drivetrain (100) comprises an internal-combustion engine (110) and an associated exhaust gas system (120), wherein the actual value of the emission component is determined in the exhaust gas system (120).

8. The method according to claim 1, wherein the prevailing emission value is determined by at least one selected from a group consisting of: the sensor (112, 121, 123, 127) and the computational model (130, 132).

9. A computing unit for determining an effective prevailing uncertainty value (304, 305) for an emission value (301, 302) for a given time point when operating a drivetrain (100) of a motor vehicle with an internal-combustion engine (110), the computing unit configured to: determine, for the emission value (301,302) at an initial phase (0<t<t.sub.0) immediately after starting the internal-combustion engine (t>0), prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are tolerances of a computational model (130, 132) determining the prevailing emission values (301), determine, for the emission value at different times (n) following the initial phase, prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are respective tolerances of a sensor (112, 121, 123, 127) or the computational model (130, 132) determining the prevailing emission values (301), determine the effective prevailing uncertainty value (304, 305) for the given time point based on the prevailing uncertainty values (303) and the prevailing emission values (301) prior to the given time point, and control operation of the drivetrain (100) by outputting a control value to the drive train (100) based on the effective prevailing uncertainty value (304, 305).

10. The method according to claim 1, wherein the respective tolerances relate to an accuracy of the sensor (112, 121, 123, 127) or the computational model (130, 132) when determining the prevailing emission values (301).

11. A non-transitory computer-readable medium for determining an effective prevailing uncertainty value (304, 305) for an emission value (301, 302) for a given time point when operating a drivetrain (100) of a motor vehicle with an internal-combustion engine (110), the non-transitory computer-readable medium including instructions executable by an electronic processor to perform a set of functions, the set of functions comprising: determine, for the emission value (301,302) at an initial phase (0<t<t.sub.0) immediately after starting the internal-combustion engine (t>0), prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are tolerances of a computational model (130, 132) determining the prevailing emission values (301), determining, for the emission value at different times (n) following the initial phase, prevailing emission values (301) and prevailing uncertainty values (303), wherein the prevailing uncertainty values (303) are respective tolerances of a sensor (112, 121, 123, 127) or the computational model (130, 132) determining the prevailing emission values (301), determining the effective prevailing uncertainty value (304, 305) for the given time point based on the prevailing uncertainty values (303) and the prevailing emission values (301) prior to the given time point, and controlling operation of the drivetrain (100) by outputting a control value to the drive train (100) based on the effective prevailing uncertainty value (304, 305).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is illustrated schematically in the drawing on the basis of embodiment examples and is described in detail in the following with reference to the drawing.

(2) FIG. 1 schematically shows a vehicle having an internal-combustion engine and a catalyst, as can be used in the context of the present invention.

(3) FIG. 2 shows a regulation range for an emission component as a function of time, as can arise in the context of a preferred embodiment of the invention.

(4) FIG. 3A-3B show an exemplary progression of an emission component and tolerance and derived values, as can arise in the context of a preferred embodiment of the invention.

DETAILED DESCRIPTION

(5) In FIG. 1, a drivetrain of a vehicle, as can be used in the context of the invention, is shown schematically and bears the overall reference number 100. The drivetrain 100 comprises an internal-combustion engine 110, for example having six indicated cylinders, an exhaust gas system 120 having multiple cleaning components 122, 124, such as catalysts and/or particulate filters, and a computing unit 130 configured so as to control the internal-combustion engine 110 and exhaust gas system 120 and connected to them in a data-conducting manner. Further, in the illustrated example, the computing unit 130 is connected to sensors 112, 121, 123, 127 in a data-conducting manner, which record operating parameters of the internal-combustion engine 110 and/or the exhaust gas system 120. It is understood that there can be other sensors that are not shown.

(6) In the example shown here, the computing unit 130 comprises a data memory 132 in which, for example, computational instructions and/or parameters (e.g. threshold values, characteristics of the internal-combustion engine 110 and/or the exhaust gas system 120, or the like) can be stored.

(7) The internal-combustion engine 110 drives wheels 140 and can also be driven by the wheels in certain operating phases (e.g. so-called coasting mode)

(8) In FIG. 2, a regulation range for an emission component as a function of time is shown, as can arise in the context of a preferred embodiment of the invention. In a diagram 200, the regulation behavior for different actual values E of an emission component is plotted against time t. A regulation range as it arises in the context of the invention bears the reference number 201. The regulation range 201 defines the range in which a respective prevailing actual value of the emission component E is to be located at a respective time point and is limited downward by a minimum value range 202 and upward by a maximum value range 203.

(9) The minimum value range 202 in turn is limited downward by a minimum value 202a and upward by a minimum tolerance value 202b corresponding to a sum of a prevailing tolerance and the minimum value 202a. Likewise, the maximum value range 203 is limited upward by a maximum value 203a and downward by a maximum tolerance value 203b, the difference between which also corresponds to the prevailing tolerance.

(10) Expediently, the minimum value 202a is determined by engine conditions in order to ensure combustion, and the maximum value 203a is determined by statutory provisions in order to avoid high emissions.

(11) For example, the upper tolerance value 203b, Limit.sub.upper, can be calculated from the maximum value 203a, Emission limit.sub.upper, and the time-based tolerance Tol.sub.eff according to the following equation:

(12) ${\mathrm{Limit}}_{\mathrm{upper}}=\frac{\mathrm{emission}{\mathrm{limit}}_{\mathrm{upper}}}{\left(1+{\mathrm{Tol}}_{\mathrm{eff}}\right)}$

(13) For example, the lower tolerance value 202b, Limit.sub.lower, can be calculated from the minimum value 202a, Emission limit and the time-based tolerance Tol.sub.eff according to the following equation:
Limit.sub.lower=emission limit.sub.lower.Math.(1+TOl.sub.eff)

(14) Beyond the limits, either compliance with the statutory limit values is no longer guaranteed, or there is an unnecessarily frequent intervention of the emissions-based regulator, leading to a deterioration of driveability and consumption, or even both at the same time.

(15) It can be seen that, at the start of operation between a time point t=0 and a time point t=t.sub.0, the minimum value range 202 and maximum value range 203 together (or the tolerance Tol.sub.eff) are so great that no regulation range exists. From the time point t=t.sub.0, at which the lower tolerance value 202b and the upper tolerance value 203b intersect, the regulation range 201 is present, which then grows with time and continues increasing. The tolerance Tol.sub.Sp at the intersection t=t.sub.0 is calculated accordingly according to the following equation:

(16) $\frac{\mathrm{emission}{\mathrm{limit}}_{\mathrm{upper}}}{\left(1+{\mathrm{Tol}}_{\mathrm{Sp}}\right)}=\mathrm{emission}{\mathrm{limit}}_{\mathrm{lower}}.Math.\left(1+{\mathrm{Tol}}_{\mathrm{Sp}}\right)$$\frac{\mathrm{emission}{\mathrm{limit}}_{\mathrm{upper}}}{\mathrm{emission}{\mathrm{limit}}_{\mathrm{lower}}}={\left(1+{\mathrm{Tol}}_{\mathrm{Sp}}\right)}^2$${\mathrm{Tol}}_{\mathrm{Sp}}=\sqrt{\frac{\mathrm{emission}{\mathrm{limit}}_{\mathrm{upper}}}{\mathrm{emission}{\mathrm{limit}}_{\mathrm{lower}}}-1}$

(17) The time-dependent calculation of the tolerance is based on the finding that tolerance or uncertainty of the emission determination is different at various time points in the travel cycle. This is especially true when the emissions are determined via a low tolerance sensor (which substantially corresponds to a measurement in accuracy), which is however not ready at the start of the journey. It can therefore be provided that the emission value is determined on the basis of a model for this initial phase immediately after starting the internal-combustion engine (t>0) and that a model tolerance is assumed that is usually significantly above a sensor tolerance.

(18) How strongly a single tolerance Tol(i) (i.e. tolerance or tolerance range at step or time point i) influences the overall tolerance Tol.sub.overall, depends on how high the generated emission mass is within the individual tolerances in relation to the total mass. The overall tolerance Tol.sub.overall on the other hand, results from the following equation:

(19) $\begin{array}{cc}To{l}_{\mathrm{overall}}=\frac{{.Math.}_{i=k}^{i=k}mEm{i}_i.Math.{\mathrm{Tol}}_i}{mEm{i}_{overall}}& \left(1\right)\end{array}$

(20) Here, mEmi(i) stands for the emission mass that was generated at the time i. The index k corresponds to the number of different tolerance ranges and, in the borderline case, the number of measurement points.

(21) By weighting the single tolerance with the emission amount, the effect on the overall tolerance is correctly represented. A high tolerance at low mass emission flow has a significantly lower effect on the overall tolerance than in the case of a high mass flow. Therefore, the calculation is discretized over the travel path.

(22) To assess the effective tolerance Tol.sub.ExpSmotng(t) at a time point t (within a shorter interval than the overall travel distance), the effective tolerance is calculated based on an exponential smoothing:

(23) $\begin{array}{cc}\mathrm{Tol}\mathrm{Exp}\mathrm{Smotng}\left(t\right)=\frac{.Math.\mathrm{mEmi}\left(t\right).Math.\mathrm{Tol}\left(t\right)+{.Math.}_{i=1}^{t-1}\left[{\left(1-\right)}^i.Math.\left(\mathrm{mEm}i\left(t-i\right).Math.\mathrm{Tol}\left(t-i\right)\right)\right]}{.Math.\mathrm{mEmi}\left(t\right)+{.Math.}_{i=1}^{t-1}\left[{\left(1-\right)}^i.Math.\mathrm{mEmi}\left(t-i\right)\right]}& \left(2\right)\end{array}$

(24) Here, a stands for the smoothing factor or present factor and i indicates how far in the past the respective time step is. This calculation allows for a lower weighting of emissions and tolerances that are further in the past, and thus the response is better to changes in the prevailing tolerance level than if all measurement points were only weighted in a mass-dependent manner, as in equation (1). However, other methods of smoothing, such as a sliding or weighted average, can also be used.

(25) The calculation shown in equation (2) corresponds to an exponential smoothing. In so doing, the distance section emissions mEmi are multiplied by the average tolerance Tol for this path section and then integrated/summed. The respective tolerances result from the tolerance of the sensor (usually dependent on the concentration of the emission: the lower the concentration, the higher the tolerance) or from the error of the emission model used (usually dependent on the operating point, e.g. less precise in the cold engine than in the warm engine).

(26) The individual parameters mEmi and Tol for the distance section i are calculated continuously. The further these lie in the past, the less influence they have on the prevailing tolerance after distance section t.

(27) The smoothing serves to properly evaluate the tolerance of the prevailing (and likewise smoothed) emissions: Overall emissions require an overall tolerance Smoothed emissions require a smoothed tolerance

(28) In FIG. 3a, an exemplary progression of an emission value in any desired units is plotted against a number n of measurement points and bears the reference number 301. An exponentially smoothed progression bears the reference number 302.

(29) In FIG. 3b, a respective prevailing tolerance bears the reference number 303, an effective overall tolerance for the entire travel path according to equation 1 bears the reference number 304, and an effective tolerance based on exponential smoothing according to equation 2 bears the reference number 305.

(30) The prevailing tolerance is known for a sensor, e.g. from its technical data (e.g. 10% deviation for a measured value>100 ppm) and for a model from its verification during the model creation (e.g. it is possible for a model to have a higher tolerance in a cold engine than in a warm one).

(31) Based on the tolerances in FIG. 3b, the intervention limits in FIG. 2 can then be calculated, or diagnoses can be evaluated in the concrete case of application.