Method for checking the plausibility of a pressure sensor

Abstract

A method for checking the plausibility of a pressure sensor that, during the measurement of a differential pressure, records measured values, whereby the measured values from the pressure sensor are compared to reference values for the differential pressure calculated on the basis of a model; whereby in order to determine the plausibility, at least one deviation of the measured values from the reference values and a difference between a first slope of the changing measured values and a second slope of the changing reference values over the curve of the measured values are taken into account.

Claims

1. A method for checking the plausibility of a pressure sensor of an engine or vehicle that, during the measurement of a differential pressure over a period of time, records measured values, comprising: determining reference values for expected differential pressure over the period of time based on: a model of reference values expected at certain operating points of the engine or the vehicle, and actual operating points of the engine or the vehicle over the period of time; calculating a correlation factor, by, for each of a plurality of times in a range of the period of time, comparing: a deviation of the measured value for the time to a reference value for the time, and a difference between a first slope of changes of the measured values in the range and a second slope of changes in the reference values in the range; and determining the plausibility of the pressure sensor, taking into account values of the correlation factor.

2. The method according to claim 1, wherein the at least one deviation or the difference is an absolute value.

3. The method according to claim 1, wherein: calculating the correlation factor comprises, for each of the plurality of times within a first time interval of the period of time, calculating a cross-correlation between: a deviation of the measured value for the time to a reference value for the time, and a difference between a first slope of changes of the measured values in the first time interval and a second slope of changes in the reference values in the first time interval, and if the calculated correlation factor falls below a limit value for the correlation factor, an implausible measured value is assumed to be present.

4. The method according to claim 3, wherein, for each of the plurality of times within the first time interval, the deviation is given a greater weight than the difference when calculating the cross-correlation.

5. The method according to claim 3, calculating the cross-correlations for the first time interval further takes into account deviations and a difference determined within at least a second time interval of the period of time preceding the first time interval.

6. The method according to claim 5, wherein, when calculating the cross-correlations for the first time interval: the deviations and the differences for the first time interval are given a greater weight than the deviations and difference for the second time interval, and if there is a time interval preceding the second time interval in the period of time, the deviations and the difference for the second time interval are given a greater weight than deviations and difference for the interval preceding the second time interval.

7. The method according to claim 1, whereby the measured values from the pressure sensor are only taken into account for other applications if the plausibility has been recognized.

8. The method according to claim 1, further comprising determining the differential pressure that is present in an exhaust gas treatment unit by the pressure sensor.

9. A motor vehicle, comprising: an internal combustion engine, an exhaust gas line for discharging the exhaust gas from the internal combustion engine, an exhaust gas treatment unit that is arranged in the exhaust gas line and that has a pressure sensor for determining a differential pressure that is present in the exhaust gas treatment unit, and a control unit that is configured for carrying out the method according to claim 1.

10. The motor vehicle according to claim 9, whereby the exhaust gas treatment unit is a particulate filter.

11. A motor vehicle, comprising: an internal combustion engine, an exhaust gas line for discharging the exhaust gas from the internal combustion engine, an exhaust gas treatment unit that is arranged in the exhaust gas line and that has a pressure sensor for determining a differential pressure that is present in the exhaust gas treatment unit, and a control unit that is configured: determine reference values for expected differential pressure over a period of time based on: a model of reference values expected at certain operating points of the internal combustion engine or the motor vehicle, and actual operating points of the internal combustion engine or the motor vehicle over the period of time; determine the plausibility of the pressure sensor by, for each of a plurality of times in a first time interval of the period of time, comparing: a deviation of the measured value for the time to a reference value for the time, and a difference between a first slope of changes of the measured values in the first interval and a second slope of changes in the reference values in the first interval.

12. The motor vehicle according to claim 11, wherein determining the plausibility of measured values includes: the control unit calculating a correlation factor over the time interval by, for each of the plurality of times within the first time interval, calculating a cross-correlation between the deviation for the time and the difference for the first time interval; and the control unit determining that the pressure sensor measured an implausible value if a value of the correlation factor falls below a predetermined limit value for the correlation factor.

13. The motor vehicle according to claim 12, wherein, for each of the plurality of times within the first time interval, the control unit is configured to give the deviation a greater weight than the difference when calculating the cross-correlation.

14. The motor vehicle according to claim 12, wherein the control unit is configured to, when calculating the cross-correlations for the first time interval, additionally take into account deviations and a difference determined within at least a second time interval preceding the first time interval, wherein the deviations and difference for each of the at least second time interval is given decreasing weight as a function of how much further back in time the preceding time interval is.

15. The motor vehicle according to claim 11, wherein, for other applications, the control unit is configured to only take into account the measured values from the pressure sensor if the control unit determines that the measured values are plausible.

16. The motor vehicle according to claim 11, wherein the exhaust gas treatment unit is a particulate filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention as well as the technical realm are explained in greater detail below on the basis of the accompanying figures. It should be pointed out that the invention should not be construed as being limited by the cited embodiments. In particular, unless explicitly indicated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other elements and insights from the present description. In particular, it should be pointed out that the figures and especially the size ratios given are only exemplary.

(2) The following is shown:

(3) FIG. 1: a motor vehicle 2 with a drive train 1;

(4) FIG. 2: first diagrams; and

(5) FIG. 3: second diagrams.

DETAILED DESCRIPTION OF THE INVENTION

(6) The motor vehicle 16 has an internal combustion engine 17, an exhaust gas line 18 for discharging exhaust gas from the internal combustion engine 17, and an exhaust gas treatment unit 15 that is arranged in the exhaust gas line 18 and that has a pressure sensor 1 for determining a differential pressure 2 that is present in the exhaust gas treatment unit 15. In addition, a control unit 19 is provided, which is configured so as to be suitable for carrying out the described method. In the control unit 19, a model 4 is stored by means of which reference values 5 for the differential pressure 2 can be determined mathematically (and theoretically) as a function of the operating point that is present.

(7) FIG. 2 shows first diagrams. In the uppermost diagram, the differential pressure 2 is plotted on the vertical axis. The time 20 is plotted on the horizontal axis. Furthermore, the curves 6 of the measured values 3 and of the reference values 5 are plotted over the time 20.

(8) The curves 6 show that, on the one hand, at certain points in time, the first slope 9 of the curve 6 of the measured values 3 exceeds the second slope 10 of the curve 10 of the reference values 5 (e.g. between the values 0 and approx. 120 of the time 20). Beyond the value 800 of the time 20, the curve 6 of the measured values 3 diverges increasingly from the curve 6 of the reference values 5.

(9) In the middle diagram, the correlation factor 2 (between −1 and 1) is plotted on the vertical axis. The time 20 is plotted on the horizontal axis. Furthermore, the curve of the correlation factor 11 is plotted over the time 20.

(10) The correlation factor 11 is determined as a function of the correlation of the deviation 7 and the difference 8. It can be seen that the correlation factor 11 is already significantly lower at the occurring difference 8 between the values of 0 and approx. 120 of the time 20 due to the fluctuation of the curve 6 of the measured values 3. However, a limit value of 12 of the correlation factor 11 at which the state 21 would indicate icing of the pressure sensor 2 is not reached.

(11) Due to the pronounced deviation 7 between the measured values 3 and the reference values 5 beyond the value 800 of the time 20 and due to the difference 8 of the slopes 9, 10 in this range, the correlation factor 11 here falls below the limit value 12, so that a state 21 of icing (see the lowermost diagram) is detected.

(12) From this point onward, the measured values 3 are recognized as being implausible and are no longer used for other applications.

(13) In the lower diagram, the state 21 is plotted on the vertical axis (zero=no icing; 1=icing detected). The time 20 is plotted on the horizontal axis. Furthermore, the curve of the state 21 identified on the basis of the curve of the correlation factor 11 is plotted over the time 20.

(14) FIG. 3 shows second diagrams. In the uppermost diagram, the differential pressure 2 is plotted on the vertical axis. The time 20 is plotted on the horizontal axis. Furthermore, the curves 6 of the measured values 3 and of the reference values 5 are plotted over the time 20.

(15) In the middle diagram, the correlation factor 2 (between −1 and 1) is plotted on the vertical axis. The time 20 is plotted on the horizontal axis. Furthermore, the curve of the correlation factor 11 is plotted over the time 20.

(16) In the lowermost diagram, the state 21 is plotted on the vertical axis (zero=no icing; 1=icing detected). The time 20 is plotted on the horizontal axis. Furthermore, the curve of the state 21 identified by the curve of the correlation factor 11 is plotted over the time 20.

(17) It can be seen here that the state 21 of icing is detected several times (between the values of zero and 500 and above the value of 950 of the time 20).

(18) It should be noted that a different limit value of 12 has been determined here for the correlation factor 11.

LIST OF REFERENCE NUMERALS

(19) 1 pressure sensor 2 differential pressure 3 measured value 4 model 5 reference value 6 curve 7 deviation 8 difference 9 first slope 10 second slope 11 correlation factor 12 limit value 13 time interval 14 distance 15 exhaust gas treatment unit 16 motor vehicle 17 internal combustion engine 18 exhaust gas line 19 control unit 20 time 21 state