Method for Determining a Speed of an Object Using an Ultrasonic Pulse

Abstract

A method is for determining a speed of an object based on an ultrasonic pulse. The method includes emitting the ultrasonic pulse using a first ultrasonic transducer. The ultrasonic pulse having a defined signal profile. The method further includes receiving an ultrasonic signal using a second ultrasonic transducer, calculating a cross-correlation, with respect to frequency, of the ultrasonic signal with a filter signal which at least partially correlates with the defined signal profile, and determining a frequency shift between the filter signal and the received ultrasonic signal using a result of the calculated cross-correlation. The method also includes determining the speed of the object which reflected the emitted ultrasonic pulse using the determined frequency shift.

Claims

1. A method for determining a speed of an object based on an ultrasonic pulse, comprising: emitting the ultrasonic pulse using a first ultrasonic transducer, the ultrasonic pulse having a defined signal profile; receiving an ultrasonic signal using a second ultrasonic transducer; calculating a frequency-related cross-correlation of the ultrasonic signal with a filter signal which at least partially correlates with the defined signal profile; determining a frequency shift between the filter signal and the received ultrasonic signal based on a result of the calculated cross-correlation; and determining the speed of the object which reflected the emitted ultrasonic pulse based on the determined frequency shift.

2. The method according to claim 1, wherein calculating the frequency-related cross-correlation includes calculating a temporal and frequency-related cross-correlation of the ultrasonic signal with the filter signal.

3. The method according to claim 1, wherein a frequency of the defined signal profile changes over time.

4. The method according to claim 2, wherein the defined signal profile has a temporal change and/or a temporal change in the frequency which is such that, during the calculation of the temporal and frequency-related cross-correlation of the ultrasonic signal with the filter signal, a clear maximum results with respect to the temporal and frequency-related cross-correlation.

5. The method according to claim 1, wherein the first ultrasonic transducer is the same as the second ultrasonic transducer.

6. The method according to claim 2, wherein a transit time of the ultrasonic pulse is determined based on an amplitude of a temporal component of the calculated temporal and frequency-related cross-correlation in order to locate the object that reflected the emitted ultrasonic pulse.

7. The method according to claim 1, further comprising: using the frequency shift of the ultrasonic signal to assign the object to the ultrasonic signal.

8. The method according to claim 1, wherein the speed of the object is determined using a relevant frequency shift of a relevant ultrasonic signal of an ultrasonic pulse received by a plurality of the ultrasonic transducers.

9. The method according to claim 1, further comprising: determining reflection points based on lateration from a plurality of the ultrasonic pulses and a plurality of the ultrasonic signals, wherein the plurality of the ultrasonic signals for determining reflection points are grouped based on the frequency shift of the respective ultrasonic signals.

10. The method according to claim 1, further comprising: providing a control signal for controlling an at least partially automated vehicle based on the determined frequency shift; and/or providing a warning signal for warning a vehicle occupant based on the determined frequency shift.

11. The method according to claim 1, wherein a device is configured to carry out the method.

12. The method according to claim 1, wherein a computer program comprises instructions which, when the computer program is executed by a computer, cause the computer to carry out the method.

13. The method according to claim 12, wherein the computer program is stored on a non-transitory machine-readable storage medium.

Description

EMBODIMENTS

[0052] Embodiments of the invention are illustrated with reference to FIGS. 1 and 2 and explained in more detail below. In the drawings:

[0053] FIG. 1 shows a defined signal profile of an ultrasonic pulse and an ultrasonic signal which is shifted in frequency;

[0054] FIG. 2 shows a plot of a two-dimensional cross-correlation and projections.

[0055] FIG. 1 shows a time profile of an emitted ultrasonic pulse 120, i.e., a defined signal profile in which the frequency f of the ultrasonic pulse 120 starting at the point in time t.sub.-1 increases linearly from a value fMIN with the time t up to the point in time t.sub.0 to a value fMAX and then the frequency decreases linearly back to the value fMIN up to the point in time t.sub.1.

[0056] As a result of the Doppler effect, an ultrasonic signal 110 that is shifted in frequency can result from this ultrasonic pulse 120, which ultrasonic signal is additionally plotted in the graph 100 of FIG. 1. Since, in this example, the profile of the frequency of the ultrasonic pulse 120 is shifted toward higher frequencies, the object moves to the receiving ultrasonic transducer.

[0057] A possible filter signal 135 is shown in the graph 130, which has a frequency profile corresponding to the ultrasonic pulse over time, which is indicated in the graph 130 by a shape of the frequency profile 135 over time that corresponds to the profile of the signal of the ultrasonic pulse.

[0058] It can be seen in FIG. 1 that a temporal cross-correlation of the ultrasonic signal 110 with the filter signal 135 allows for unambiguous assignment of the ultrasonic signal 110 in time with this defined signal profile of the ultrasonic signal. This figure shows that a temporal cross-correlation of the ultrasonic signal 110 with the filter signal 135 would produce at the point in time t.sub.0.

[0059] FIG. 2 outlines one possible result of a two-dimensional cross-correlation in time and frequency. The result, i.e., the value, of such a cross-correlation over time t and frequency f is plotted in the graph 210. Here, five ultrasonic signals 211, 212, 213, 214, 215 can be seen, each having a maximum 211 m, 212 m, 213 m, 214 m, 215 m, which is shifted for the ultrasonic signals 212, 213, 214, 215 with respect to an ultrasonic signal 211 from a non-moving static object with the maximum 211 m at the frequency f.sub.0. Here, the maximum of the ultrasonic signal 211 from a static object is therefore at a frequency f.sub.s that corresponds to that of the emitted ultrasonic pulse f.sub.0. The two next echo signals 212, 213 in the center were reflected by an object at a negative relative speed, resulting in a decrease in frequency. The two echo signals 214, 215 on the right in the plot were reflected by an object at a positive relative speed and therefore show an increase in frequency.

[0060] This frequency shift Δf is plotted over the value K.sub.F of the frequency-related cross-correlation as a projection onto the frequency axis for the ultrasonic signal 212 in the graph 230 of FIG. 2 for the purpose of clarification.

[0061] The graph 220 of FIG. 2 outlines the profile of a value K.sub.T of a correlation of ultrasonic signals with the filter signal, it being possible to convert the transit times t.sub.2, t.sub.3, t.sub.4, t.sub.5, t.sub.6 of the different ultrasonic signals 211, 212, 213, 214, 215 into a distance of the object from the relevant receiving ultrasonic transducer. In other words, the graph 220 shows a projection of the result of the two-dimensional cross-correlation onto the time range and the graph 230 shows the projection onto the frequency range.

[0062] This means that, using this method for determining a speed of an object by means of an ultrasonic pulse, an ultrasonic pulse is emitted by means of a first ultrasonic transducer which has a defined signal profile. The ultrasonic signal reflected by an object is received by a second ultrasonic transducer which may be identical to the first ultrasonic transducer. A frequency shift between the filter signal and the received ultrasonic signal can be determined as described by means of a frequency-related cross-correlation of the ultrasonic signal with the filter signal which at least partially correlates with the defined signal profile. The speed of the object that reflected the ultrasonic pulse can then be calculated according to the Doppler effect.