WO2020064161A1

WO2020064161A1 - Method for operating an ultrasonic sensor for a vehicle taking into account a frequency difference between a raw signal and a reference signal, computing device, and ultrasonic sensor apparatus

Info

Publication number: WO2020064161A1
Application number: PCT/EP2019/067925
Authority: WO
Inventors: Mathieu BAICRY; Jean Francois Bariant; Denis ASCHKENASI; Thomas Jung; Anto MICHAEL
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2018-09-28
Filing date: 2019-07-04
Publication date: 2020-04-02
Also published as: DE102018124050A1

Abstract

The invention relates to a method for operating an ultrasonic sensor (4) for a vehicle (1), in which method the ultrasonic sensor (4) is excited with an excitation signal (21) to emit an ultrasonic signal during a transmission phase, the excitation signal (21) having a frequency change with a predefined gradient as a function of time (t), and a raw signal (10) which describes the ultrasonic signal reflected in the area (9) surrounding the vehicle (1) is determined during a reception phase. The presence of an object (8) in the surrounding area (9) is checked using the raw signal (10) and at least one reference signal (R1, R2), wherein the at least one reference signal (R1, R2) has a frequency change with the predefined gradient as a function of time (t), a frequency difference (Δf) between the raw signal (10) and the at least one reference signal (R1, R2) is determined, and a distance between the ultrasonic sensor (4) and the object (8) is determined using the frequency difference (Δf).

Description

Method for operating an ultrasonic sensor for a vehicle, taking into account a frequency difference between a raw signal and a reference signal,

Computing device and ultrasonic sensor device

The present invention relates to a method for operating an ultrasound sensor for a vehicle, in which the ultrasound sensor is excited during a transmission phase to emit an ultrasound signal with an excitation signal, the excitation signal causing a frequency change with a predetermined gradient

Depends on the time. During a reception phase, a raw signal is determined which reflects that in a surrounding area of the vehicle

Ultrasound signal describes the presence of an object in the

Surrounding area is checked based on the raw signal and at least one reference signal. Furthermore, the present invention relates to a computing device and an ultrasonic sensor device. Finally, the present invention relates to a computer program product and a computer-readable medium.

In the present case, interest is directed to ultrasonic sensor devices for vehicles. Such ultrasonic sensor devices can be used, for example, to detect an object in a surrounding area of the vehicle. Such

Ultrasonic sensor device usually comprises several ultrasonic sensors, with each of which a distance to the object can be determined. For this purpose, an ultrasonic signal is sent out with the ultrasonic sensor and the ultrasonic signal reflected by the object is received again. Based on the transit time between the emission of the ultrasound signal and the reception of that reflected by the object

The ultrasound signal can then be determined taking into account the propagation speed of the ultrasound signal or the airborne sound speed, the distance to the object. A raw signal can be determined with the ultrasonic sensor to determine the transit time

are provided, which describes the ultrasound signal reflected from an object. This raw signal can be multiplied or mixed with at least one reference signal. Following this, the echo signal

are filtered accordingly, in addition, a correlation with an expected signal or pattern can be carried out in order to be able to check the presence of objects in the surrounding area. With this method, it is necessary that the entire echo or raw signal is used to at the output the correlator to get a usable signal. During the transmission phase, in which the ultrasound signal is emitted with the ultrasound sensor, the raw signal is saturated. During this transmission phase, no echoes of the transmitted ultrasound signal can be received. In other words, the ultrasonic sensor or the ultrasonic sensor device is blind during the transmission phase. So-called blind areas usually result for a distance of 45 cm from the vehicle.

In order to reduce the blind area, methods are known from the prior art in which the correlation is not carried out with the complete expected signal, but only with a part of the signal, for example the last 20% of the signal. In this way, the detection range in a close range can be improved. A disadvantage of such a method can be seen in the fact that it is less robust against external interference than in the correlation with the complete signal. This disadvantage arises in particular when several ultrasonic sensors emit at the same time. In this case, crosstalk between neighboring

Ultrasonic sensors take place.

In this context, DE 102 25 614 A1 describes a circuit arrangement for operating an ultrasonic transducer serving as a distance sensor. The

Circuit arrangement causes the ultrasound transducer to emit ultrasound pulses of different frequencies in succession. The transmission of these pulses with different frequencies enables the echoes to be clearly assigned to their transmission pulses. In this way, bandpass filters can be used to receive the echoes, which are tuned to the respective frequency and thus only filter out echoes of this frequency. The avoidance of "blind zones" is solved by appropriately selecting the time intervals between the individual transmission pulses.

In addition, DE 10 2013 211 846 A1 describes a method for operating an environment detection system of a vehicle with at least one transmitter / receiver unit. Here, instead of transmission signals with a fixed frequency, transmission signals with a changing frequency are selected, for example

Frequency-modulated signals with linear, logarithmic or quadratic modulation. The emitted frequency-modulated signal has at least a first section with increasing frequencies and a second section with falling frequencies. The received echo signals are assigned to reflection sources, and on the basis of the received echo signals, information about the

Speed of the reflection sources determined relative to the transmitter / receiver unit.

DE 10 2011 075 484 A1 also describes an ultrasonic measuring system for

Detection of an obstacle with an ultrasound sensor, which has a transducer element for emitting an ultrasound pulse and for generating a received signal. Furthermore, the ultrasound measuring system has an evaluation unit with a control device, which is designed to convert a transducer element of the

To excite the ultrasonic sensor to emit the ultrasonic pulse. The control device is designed to generate a frequency-modulated transmission signal by means of a modulation signal such that the signature of the ultrasound pulse differs from that of a decay signal. Furthermore, the evaluation unit comprises at least one correlation filter, the at least one correlation filter being designed to correlate the signal generated by the converter element with the transmission signal.

It is an object of the present invention to show a solution, such as the detection of objects in a surrounding area of a vehicle using a

Ultrasonic sensor can be carried out more robustly.

This object is achieved by a method by a

Computing device, by an ultrasonic sensor device, by a

Computer program product as well as through a computer readable medium with the

Features solved according to the independent claims. Advantageous developments of the present invention are the subject of the dependent claims.

A method according to the invention is used to operate an ultrasonic sensor for a vehicle. Here, the ultrasound sensor is excited during a transmission phase to emit an ultrasound signal with an excitation signal

Excitation signal a frequency change with a predetermined slope in

Depends on the time. During the reception phase, a raw signal is determined which reflects that in the area surrounding the vehicle

Ultrasound sensor describes. Furthermore, the presence of an object in the surrounding area is checked on the basis of the raw signal and at least one reference signal. It is provided here that the at least one reference signal is a

Frequency change with the predetermined slope as a function of time. In addition, there is a frequency difference between the raw signal and the determines at least one reference signal. In addition, a distance between the ultrasonic sensor and the object is determined based on the frequency difference.

With the aid of the method, the ultrasonic sensor can be operated. Of the

Ultrasonic sensor is in particular part of an ultrasonic sensor device that is used in the vehicle. The method can be carried out, for example, with an electronic computing device or an electronic control device. The ultrasonic sensor can detect objects or obstacles in the

Surrounding area of the vehicle can be detected. For this purpose, the ultrasonic signal is sent out with the ultrasonic sensor. For this purpose, a membrane of the

Ultrasonic sensor with a corresponding transducer element, for example a piezoelectric element, excited to mechanical vibrations. For this purpose, the transducer element can be supplied with the excitation signal in the form of a time-varying electrical voltage. This excitation signal has a time-dependent frequency change in a predetermined slope. In particular, it is provided that the frequency of the excitation signal changes linearly as a function of time. This means that the slope of the frequency change in

Depending on the time is preferably linear.

That in the surrounding area or from an object in the

Ultrasound signal reflected in the surrounding area can be received again during the reception phase of the ultrasound sensor. The ultrasound signal reflected by the object strikes the membrane of the ultrasound sensor, as a result of which the latter and the transducer element are excited to mechanical vibrations. With the aid of the converter element, a time-varying electrical voltage can then be output as a function of this mechanical vibration. This time-varying electrical voltage can then be used as the raw signal. In particular, it is provided that the time-varying electrical

Voltage that is output by the transducer element is amplified and sampled accordingly. The raw signal thus describes, in particular, the amplified and sampled electrical voltage that is output by the converter element.

This raw signal can be mixed or multiplied with at least one reference signal.

According to an essential aspect of the present invention, it is provided that this reference signal has a frequency change with the predetermined slope as a function of time. In other words, it is at least one reference signal is also a signal whose frequency changes as a function of time and with the same slope with which the frequency of the excitation signal changes as a function of time. With the at least one reference signal, the frequency can also change linearly as a function of time. The frequency change depending on the time, the excitation signal and the at least one reference signal can be the same or differ. It is crucial that the slope of the frequency change in

Dependence on the time for the excitation signal and the at least one

Reference signal are the same. The emitted and reflected by the object

Ultrasound signal also has the frequency change as a function of the time of the excitation signal. A frequency difference between the raw signal and the at least one reference signal can thus be determined. Based on the

Frequency difference can then be a time offset between the transmission of the ultrasound signal and the reception of that reflected by the object

Ultrasound signal can be determined. Based on this time offset

or the transit time, the distance between the ultrasonic sensor and the object can then be determined. For this purpose, the speed of propagation of the ultrasonic signal in the air or the speed of airborne sound

be taken into account. Overall, a reliable and robust method for operating an ultrasound sensor or for detecting objects in the area surrounding the vehicle can be provided with the aid of an ultrasound sensor.

To determine the frequency difference, at least one mixed signal is preferably determined, which is a multiplication of the raw signal by the at least one

Describes reference signal. Furthermore, it is preferably provided that the at least one mixed signal is filtered in order to determine the frequency difference. The at least one reference signal can be mixed with the raw signal. A multiplicative mixture is carried out in particular. The result of this

multiplicative mixture is a sum and a difference of the frequency of the raw signal and the frequency of the at least one reference signal. The difference between the two can be determined by appropriate filtering, for example low-pass filtering

Frequencies are determined. In particular, the cutoff frequency of the low-pass filter is determined in such a way that the filtered mixed signal describes the frequency difference between the at least one reference signal and the raw signal. It is therefore possible to determine the proportion of the mixed signal which is the difference in the frequency of the raw signal and describes the frequency of the at least one reference signal. The frequency difference can thus be determined in a simple and reliable manner.

In a further embodiment, the frequency difference is determined on the basis of a time duration between successive zeros of the at least one filtered mixed signal. As already explained, the filtered mixed signal preferably describes the difference between the frequency of the at least one reference signal and the frequency of the raw signal. The filtered mixed signal can describe a time-dependent oscillation, for example a sinusoidal oscillation. Based on the time duration between successive or neighboring ones

Zeros can then be used to determine the frequency of the filtered mixed signal, which corresponds to the frequency difference.

According to a further embodiment, the frequency difference can be determined on the basis of a time duration between successive maxima and / or minima of the at least one filtered mixed signal. The time duration between successive maxima, time duration between successive minima or both the time duration between successive maxima and minima can be determined in the filtered mixed signal in order to determine the frequency difference between the at least one reference signal and the raw signal. The determination of the frequency difference on the basis of the time duration between successive maxima and / or minima is characterized in that they are more robust against external interference, for example signals from neighboring ones

Ultrasonic sensors or signals in the surrounding area.

In a further embodiment, the raw signal is multiplied by a first reference signal and by a second reference signal, the first reference signal and the second reference signal having a phase difference of 90 ° with respect to one another. In other words, a so-called IQ mix can be carried out. In an IQ mixer, the raw signal can be combined with the first reference signal and with the second

Reference signal, which has a phase difference of 90 ° to the first reference signal, mixed or multiplied. In this case, it is preferably provided that a first mixed signal, which describes the multiplication of the raw signal by the first reference signal, and a second mixed signal, which describes the

Multiplication of the raw signal with the second reference signal describes can be determined. In addition, the frequency difference can depend on the first

Mixed signal and the second mixed signal can be determined. The first mixed signal and the second mixed signal can - as described above - be filtered with a low-pass filter. Furthermore, a first can then be based on the first mixed signal

Frequency difference can be determined, and a second frequency difference can be determined on the basis of the second mixed signal. In addition, from the first

Frequency difference and the second frequency difference are formed an average. The frequency difference between the raw signal and the at least one reference signal can then be derived from this. The raw signal can thus be processed in two separate channels or paths of signal processing, and the determination of the frequency difference can thus be carried out more robustly with respect to interference.

In a further embodiment, the frequency difference is determined if an amplitude of the at least one signal exceeds a predetermined threshold value. The frequency difference is preferably only determined if the amplitude of the at least one mixed signal exceeds the predetermined threshold value. It can also be provided that the frequency difference is only determined if an amplitude of the at least one filtered mixed signal exceeds the predetermined threshold value. It can thus be achieved that the method becomes more robust against noise or interference. If the amplitude of the filtered mixed signal is below the threshold value, the probability is low that the raw signal describes an echo of the ultrasound signal reflected by the object. In this case, it is not necessary to determine the frequency difference. The method can thus be carried out efficiently.

In a further embodiment, a frequency difference signal is determined, which describes the frequency difference between the raw signal and the at least one reference signal, and echoes of the ultrasound signal reflected by the object are recognized on the basis of the frequency difference signal. The frequency difference signal can describe the time course of the frequency difference, which was determined on the basis of the at least one filtered mixed signal. If a first mixed signal is determined on the basis of the first reference signal and a second mixed signal is determined on the basis of the second reference signal, the frequency difference signal can describe the mean value of certain frequency differences as a function of time. This frequency difference signal can now be used to echo the

Detect ultrasound signal or reflections of the ultrasound signal on objects in the surrounding area. Areas of the frequency difference signal at which an amplitude of the frequency difference signal is constant are preferably determined in order to recognize the echoes. If the raw signal describes echoes, the frequency difference signal is essentially constant or stable for a certain period of time or in a certain range. For example, the frequency difference signal can have a substantially constant value in these areas. These areas or time segments can then be assigned to signal segments in the raw signal that originate from an echo. The transit time is proportional to the frequency. Alternatively or additionally, a number of respective frequency components of the frequency difference signal can be determined. If one or more

Frequencies appear in the frequency difference signal more often, this means in particular that one or more echoes are present at a distance which corresponds to these frequencies. This enables detection of echoes, particularly in a close range.

The excitation signal and the at least one reference signal are preferably a chirp. For example, the excitation signal and the reference signal can be chirp-up signals. This means that the frequency increases linearly as a function of time. The excitation signal and the at least one reference signal can also be a chirp-down signal. In this case, the frequency of the signal decreases linearly as a function of time. With such chirp signals, the frequency difference can be determined in a simple and reliable manner.

In a further embodiment, the method is used in a short-range mode for detecting objects in a predetermined short range of the surrounding area. The method according to the invention is particularly suitable for recognizing objects in the predetermined close range. This close range can be at a distance from the vehicle or the ultrasonic sensor that is less than 45 cm. The at least one ultrasonic sensor can be operated in the short-range mode at predetermined times as a function of a detected object. Otherwise, the ultrasonic sensor can be operated in a normal mode. It can be provided that the received raw signal with a

Reference signal is multiplied or mixed, which has a constant frequency. The ultrasonic sensor can thus be operated as required.

It can also be provided that the short-range mode and the normal mode are used in parallel. If a distance less than a distance limit value is detected, the raw signal can be performed according to the method according to the invention be evaluated. If a distance greater than or equal to the distance limit value is recognized, the raw signal can be evaluated according to a known method. The distance limit can be 45 cm.

A computing device according to the invention for an ultrasonic sensor device of a vehicle is designed to carry out a method according to the invention and the advantageous refinements thereof. The computing device can be formed by a corresponding processor, a digital signal processor or the like. For example, the computing device can be part of an electronic control unit of the vehicle. It can also be provided that the

Computing device is part of the ultrasonic sensor. In this case it is

Computing device is preferably designed as an application-specific integrated circuit. Here, the computing device in a housing of the

Ultrasonic sensor can be arranged.

An ultrasonic sensor device according to the invention for a vehicle comprises a computing device according to the invention. In addition, the ultrasonic sensor device comprises at least one ultrasonic sensor. It can also be provided that the

Ultrasonic sensor device has a plurality of ultrasonic sensors, which can then be arranged distributed in the vehicle. An inventive

Driver assistance system comprises an ultrasonic sensor device according to the invention. With the help of the driver assistance system, objects in the area surrounding the vehicle can be recognized. The driver assistance system can be designed to issue a warning to the driver of the vehicle if there is an object in the vehicle

Surrounding area is recognized. It can also be provided that the

Driver assistance system is designed to maneuver the vehicle at least semi-autonomously depending on a detected object. The driver assistance system can also be designed as a parking assistance system or as a brake assistant.

A vehicle according to the invention comprises one according to the invention

Ultrasonic sensor device or an inventive

Driver assistance system. The vehicle is designed in particular as a passenger car. It can also be provided that the vehicle is designed as a commercial vehicle.

The invention also includes a computer program product with program code means which are stored in a computer-readable medium in order to achieve the invention Carrying out the method and the advantageous refinements thereof when the computer program product is processed on a processor of an electronic control unit.

Another aspect of the invention relates to a computer-readable medium, in particular in the form of a computer-readable floppy disk, CD, DVD, memory card, USB memory unit, or the like, in which program code means are stored in order to carry out the method according to the invention and the advantageous refinements thereof, if the

Program code means are loaded into a memory of an electronic control unit and processed on a processor of the electronic control unit.

The preferred presented with reference to the inventive method

Embodiments and their advantages apply accordingly to the computing device according to the invention, the ultrasonic sensor device according to the invention, for the driver assistance system according to the invention, for the vehicle according to the invention for the computer program product according to the invention and for the computer-readable medium according to the invention.

Further features of the invention result from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures are not only in the respectively specified combination but also in others

Combinations can be used without departing from the scope of the invention. Embodiments of the invention are thus also to be regarded as encompassed and disclosed, which are not explicitly shown and explained in the figures, but by separate ones

Combinations of features emerge from the explanations explained and can be generated. Versions and combinations of features are also to be regarded as disclosed, which therefore do not have all the features of an originally formulated independent claim. In addition, versions and combinations of features, in particular those explained above, are to be regarded as disclosed which go beyond or differ from the combinations of features set out in the references of the claims.

The invention will now be explained in more detail on the basis of preferred exemplary embodiments and with reference to the accompanying drawings. Show: Fig. 1 is a schematic representation of a vehicle which a

Ultrasonic sensor device having a plurality of ultrasonic sensors; 2 shows a schematic circuit diagram of a computing device for carrying out a method for operating an ultrasonic sensor;

3 shows a frequency of a raw signal provided with the ultrasonic sensor and a frequency of a reference signal as a function of time;

4 shows a frequency of the raw signal and a frequency of the reference signal according to a further embodiment as a function of time;

5 shows a time course of the raw signal, which is provided with the ultrasonic sensor; and

Fig. 6 shows a time course of a frequency difference signal, which a

Frequency difference between the raw signal and the reference signal describes.

In the figures, elements that are the same or have the same function are the same

Provide reference numerals.

1 shows a top view of a vehicle 1, which in the present case is designed as a passenger car. The vehicle 1 comprises a driver assistance system 2, which serves to assist a driver in driving the vehicle 1. The

Driver assistance system 2 can be designed as a brake assistant. Furthermore, the driver assistance system 2 can be designed as a parking assistance system, by means of which the driver can be assisted when parking the vehicle 1 in a parking space and / or when parking out of the parking space.

The driver assistance system 2 in turn comprises an ultrasonic sensor device 3. The ultrasonic sensor device 3 has at least one ultrasonic sensor 4. In the present exemplary embodiment, the ultrasonic sensor device 3 comprises twelve ultrasonic sensors 4. Six of the ultrasonic sensors 4 are in one

Front area 6 of vehicle 1 and six of ultrasonic sensors 4 in one Rear area 7 of the vehicle 1 arranged. The ultrasonic sensors 4 can in particular be mounted on the bumpers of the vehicle 1. Here, the ultrasonic sensors 4 can be arranged at least in certain areas in corresponding recesses or through openings of the bumpers. It can also be provided that the ultrasonic sensors 4 are arranged behind the bumpers. In principle, the ultrasonic sensors 4 can also be arranged on further trim parts or components of the vehicle 1. For example, the ultrasonic sensors 4 can be arranged on or hidden behind the doors of the vehicle 1.

The respective ultrasonic sensors 4 can be used to provide raw signals 10 (FIG. 5) which describe at least one object 8 in a surrounding area 9 of the vehicle 1. In the present case, an object 8 is schematically shown in the surrounding area 9. To determine the raw signal 10, an ultrasonic signal can be emitted with each of the ultrasonic sensors 4. The ultrasound signal or echo reflected by the object 8 can then be received again. Based on the transit time between the emission of the ultrasound signal and the

Receiving the ultrasound signal reflected by the object 8 can then determine a distance between the ultrasound sensor 4 and the object 8. It can also be provided that the ultrasound signal, which was emitted by one of the ultrasound sensors 4, is received with an adjacent ultrasound sensor 4. This is also known as a cross measurement.

In addition, the ultrasonic sensor device 3 comprises an electronic one

Computing device 5, which can be formed, for example, by an electronic control unit of vehicle 1. The computing device 5 is connected to the ultrasonic sensors 4 for data transmission. Corresponding data lines are not shown here for the sake of clarity. The respective ultrasonic sensors 4 can be excited by means of the computing device 5 to emit the ultrasonic signal with an excitation signal 21. In the present case, this excitation signal 21 is configured such that it exhibits a frequency change with a predetermined slope as a function of time. In particular, it is

Excitation signal 21 around a linear chirp signal. An ultrasonic signal is then emitted with the ultrasonic sensors 4, which essentially has the frequency response of the excitation signal 21. This ultrasonic signal is then reflected by the object 8 and then received by the ultrasonic sensor 4. With the

Ultrasonic sensor 4 then determines the raw signal 10 which is the received one or describes the ultrasound signal reflected by the object 8. These raw signals 10 can then be transmitted from the ultrasound sensors 4 to the computing device 5 in order to recognize the object 8 in the surrounding area 9. This information can then be used by the driver assistance system 2 to output an output to the driver of the vehicle 1. In addition, it can be provided that the driver assistance system 2 intervenes in a steering system, a braking system and / or a drive motor in order to at least semi-autonomously maneuver the vehicle 1 as a function of the detected object 8.

FIG. 2 shows a schematic circuit diagram of the computing device 5. The raw signal 10, which is provided in the ultrasonic sensor 4, is received at an input. The raw signal 10 describes one of a converter element of the

Ultrasonic sensor 4 provided electrical voltage, which was amplified and sampled accordingly. This raw signal is fed to a first mixer 1 1 a, by means of which the raw signal 10 is mixed with a first reference signal R1

or multiplied. This results in a first mixed signal 12a, which is fed to a first low-pass filter 13a. The cut-off frequency of the first low-pass filter 13a is determined such that the filtered mixed signal is the difference between the frequency of the raw signal 10 and the frequency f of the first

Describes reference signal R1. An optional downsampling is carried out in a block 14a, in which, for example, the sampling frequency is reduced. In the same way, the raw signal 10 is mixed or multiplied by a second mixer 11b with a second reference signal R2. The second reference signal R2 has a phase difference of 90 ° from the first reference signal R1. The first reference signal R1 can be described as cos (oo (t) t) and the second reference signal R2 can be described as cos (oo (t) t), where oo (t) describes the pulsation of the reference signal R1, R2, which is changes depending on the time t.

At the output of the second mixer 11b there is a second mixed signal 12b which is fed to a second low-pass filter 13b. In addition, downsampling is carried out in block 14b.

In a block 15, the amplitudes of the signals are determined and with a

predetermined threshold value 16 compared. If the amplitudes of the filtered

If mixed signals 12a, 12b exceed the threshold value 16, a frequency difference Af between the raw signal 10 and the first reference signal R1 is determined in a block 17a on the basis of the first mixed signal 12a. In the same way, the frequency difference Af between the raw signal 10 and the second is in a block 17b Reference signal R2 is determined on the basis of the second mixed signal 12b. It can also be provided that a period or a difference in the period is determined in blocks 17a and 17b. An average of the two determined frequency differences is then determined in a block 18. At the output of block 18 there is a frequency difference signal 19 which is the averaged one

Frequency difference Af depending on the time t describes. This

Frequency difference signal 19 is fed to an echo detection device 20.

3 shows a change in the frequency f of the reference signals R1, R2 as a function of the time t. It can be seen here that in the present exemplary embodiment the frequency f of the reference signals R1, R2 increases as a function of time. The reference signal R1, R2 is therefore a chirp-up signal. In addition, the

Change in frequency f of the excitation signal 21 as a function of time t is shown, the ultrasonic sensor 4 or the transducer element of the

Ultrasonic sensor 4 is excited with the excitation signal 21. The emitted ultrasound signal thus also has the frequency response of the excitation signal 21.

The frequency change of the raw signal 10 as a function of the time t is also shown. The raw signal 10 describes the ultrasonic signal reflected by the object 8 and received by the ultrasonic sensor 4. It can be clearly seen here that the frequency difference Af between the reference signal R1, R2 and the raw signal 10 is constant over the length of the echo. The frequency difference Af is proportional to a running time t _o .

In the example according to FIG. 3, the frequency of the first part of the reference signal R1, R2 is the same as the frequency of the excitation signal 21 or the emitted ultrasound signal. It can also be provided that the frequency f of the reference signals R1, R2 is greater or less than the frequency f of the excitation signal 21. This is illustrated by way of example in FIG. 4. It should be noted that an increase in the frequency f of the reference signal R1, R2 as a function of the time t corresponds to an increase in the frequency f of the excitation signal 21. It can thus be achieved that the frequency difference Af between the reference signal R1, R2 and the raw signal 10 remains constant.

The frequency difference Af between the reference signal R1, R2 and the raw signal 10 can be achieved by mixing the raw signal 10 with the reference signal R1, R2 and the subsequent low-pass filtering. After this operation, the filtered mixed signal describes the difference in frequency f of the reference signals R1, R2 and the frequency f of the raw signal 10. The frequency f of the filtered and mixed down mixed signals is then determined. The time period between successive zeros of the filtered mixed signal can thus be determined. It can also be provided that the time period between successive maxima and minima of the filtered mixed signals is determined.

In the example according to FIG. 2, the raw signal is mixed with the two reference signals R1, R2, which have a phase difference of 90 ° to one another. In principle, it can be provided that the raw signal 10 is mixed with a single reference signal R1, R2.

5 describes a time profile of the raw signal 10 as a function of the time t. The time t is on the abscissa and the amplitude A is on the ordinate

Raw signal 10 plotted. A region 22 can be seen in the raw signal 10, which is to be assigned to the transmission mode of the ultrasonic sensor 4. In this case, the membrane of the ultrasonic sensor 4 is excited to vibrate by means of the transducer element. Subsequently, an area 23 can be seen which originates from an echo or the reflected ultrasound signal from an object 8 which is at a distance of 20 cm from the ultrasound sensor 4. Furthermore, a region 24 of the raw signal 10 describes an echo of the emitted ultrasound signal from an object which is at a distance of 40 cm from the ultrasound sensor 4.

6 shows a profile of the frequency difference signal 19. Here, the time t is plotted on the abscissa and the frequency f is plotted on the ordinate. This

Frequency difference signal 19 is evaluated in the echo detection unit 20. The echoes can be recognized by the fact that the frequency difference signal 19 is stable or essentially constant in one area. Another possibility is to determine the number of appearances for each of the frequencies. If one or more frequencies are present in the frequency difference signal 19, this means that these frequency components come from echoes. In the present case, an area 25 can be seen in the frequency difference signal 19, which comes from the echo of the signal at a distance of 20 cm. This distance can be determined on the basis of the corresponding frequency f1. In a region 26, the frequency difference signal 19 essentially has the frequency f2. This area 26 originates from the object at a distance of 40 cm, which corresponds to the frequency f2. The method was explained on the basis of excitation signals 21 and reference signals R1, R2, which are designed as a chirp-up signal. It can also be provided that the excitation signal 21 and the reference signals R1, R2 are designed as a chirp-down signal. If adjacent ultrasound sensors 4 are to emit ultrasound signals at the same time, a chirp-up signal can be emitted with the ultrasound sensors 4, and a chirp-down signal can be emitted with the other ultrasound sensors 4. It can also be provided that the neighboring ones

Ultrasonic sensors 4 Send ultrasonic signals in different frequency bands. In these cases, two channels are used. Here the method can then be used for each of the channels. Overall, the method shown is preferably suitable for detecting objects 8 in a close range or in a range at a distance of less than 45 cm from the vehicle of an ultrasonic sensor 4.

Claims

1. A method for operating an ultrasonic sensor (4) for a vehicle (1), in which the ultrasonic sensor (4) is excited during a transmission phase to emit an ultrasonic signal with an excitation signal (21), the excitation signal (21) causing a frequency change with a predetermined slope in

Depending on the time (t), and during a reception phase a raw signal (10) is determined, which describes the ultrasound signal reflected in a surrounding area (9) of the vehicle (1), an object (8) being present in the surrounding area (9) is checked on the basis of the raw signal (10) and at least one reference signal (R1, R2), characterized in that

the at least one reference signal (R1, R2) exhibits a frequency change with the predetermined slope as a function of time (t)

Frequency difference (Af) between the raw signal (10) and the at least one reference signal (R1, R2) is determined and a distance between the

Ultrasonic sensor (4) and the object (8) is determined based on the frequency difference (Af).

2. The method according to claim 1,

characterized in that

To determine the frequency difference (Af), at least one mixed signal (12a, 12b) is determined, which describes a multiplication of the raw signal (10) by the at least one reference signal (R1, R2), and the at least one mixed signal (12a, 12b) by one Low pass filter (13a, 13b) is filtered.

3. The method according to claim 2,

characterized in that

the frequency difference (Af) based on a time duration between

successive zeros of the at least one filtered mixed signal is determined.

4. The method according to claim 2,

characterized in that

the frequency difference (Af) based on a time duration between

successive maxima and / or minima of the at least one filtered

Mixed signal is determined.

5. The method according to any one of the preceding claims,

characterized in that

the raw signal (10) with a first reference signal (R1) and with a second

Reference signal (R2) is multiplied, the first reference signal (R1) and the second reference signal (R2) having a phase difference of 90 ° with respect to one another.

6. The method according to claim 5,

characterized in that

a first mixed signal (12a), which describes the multiplication of the raw signal (10) by the first reference signal (R1), and a second mixed signal (12b), which describes the multiplication of the raw signal (10) by the second reference signal (R2) and the frequency difference (Af) is determined as a function of the first mixed signal (12a) and the second mixed signal (12b).

7. The method according to any one of claims 2 to 6,

characterized in that

the frequency difference (Af) is determined if an amplitude of the at least one mixed signal (12a, 12b) exceeds a predetermined threshold value.

8. The method according to any one of the preceding claims,

characterized in that

a frequency difference signal (19) is determined, which the

Frequency difference (Af) between the raw signal (10) and the at least one reference signal (R1, R2) describes, and on the basis of the frequency difference signal (19) echoes of the ultrasonic signal reflected by the object (8) can be detected.

9. The method according to claim 8,

characterized in that

areas (25, 26) of the frequency difference signal (19) in which an amplitude of the frequency difference signal (19) is constant and / or a number of respective frequency components of the

Frequency difference signal (19) is determined.

10. The method according to any one of the preceding claims,

characterized in that

the excitation signal (21) and the at least one reference signal (R1, R2)

Chirp is.

1 1. The method according to any one of the preceding claims,

characterized in that

the method is used in a close range mode for detecting objects (8) in a predetermined close range of the surrounding area (9).

12. Computing device (5) for an ultrasonic sensor device (3) of a vehicle (1), the computing device (5) being designed to carry out a method according to one of the preceding claims.

13. Ultrasonic sensor device (3) for a vehicle (1) comprising a

Computing device (5) according to claim 12 and at least one

Ultrasonic sensor (4).

14. Computer program product with program code means, which in one

computer-readable medium are stored in order to carry out a method according to one of claims 1 to 11 when the computer program product is processed on a processor of an electronic computing device (5).

15. Computer-readable medium, in particular in the form of a computer-readable floppy disk, CD, DVD, memory card, USB memory device, or the like, in which

Program code means are stored to carry out a method according to one of the

Claims 1 to 11 to perform when the program code means in a Memory of an electronic computing device (5) are loaded and processed on a processor of the electronic computing device (5).