CN111308475A

CN111308475A - Method and apparatus for sensing surroundings of vehicle and vehicle having the same

Info

Publication number: CN111308475A
Application number: CN201911272995.6A
Authority: CN
Inventors: S·魏森迈尔; C·文德尔; S·奥尔布里希; T·柯尼希
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-12-12
Filing date: 2019-12-12
Publication date: 2020-06-19
Also published as: DE102018221517A1

Abstract

The invention relates to a method for sensing the surroundings of a vehicle, comprising the following steps: receiving at least one acoustic signal (36,46) from the vehicle surroundings (30) by means of at least one acoustic sensor (14) that is secured to the vehicle; evaluating the received signal analytically and determining at least one characteristic of the surroundings (30) from the analytical evaluation; characterized in that the at least one vehicle-bound acoustic sensor (14) is arranged in the region of the underbody (12) of the vehicle (10) in such a way that the received acoustic signals (16) are reflected at least partially by the roadway surface (20) from a region of the surroundings (30) of the vehicle (10) to the vehicle-bound acoustic sensor (14), wherein the surroundings (30) of the vehicle (10) comprise in particular a roadway in the vicinity of the body surroundings and/or a region below the vehicle (10). The invention also relates to a device and a vehicle having the device.

Description

Method and apparatus for sensing surroundings of vehicle and vehicle having the same

Technical Field

The invention relates to a method for sensing the surroundings of a vehicle by: at least one acoustic signal reflected from the vehicle surroundings is received by means of at least one acoustic sensor and/or by means of an additional receiver that is secured to the vehicle, and the received echo signals are evaluated analytically and at least one property of the surroundings is determined from the evaluation. The invention also relates to a device which is designed to carry out the method according to the invention. The invention further relates to a vehicle having such a device.

Background

Nowadays, a large number of sensors are required for autonomous driving, among them lidar sensors, camera sensors, radar sensors and ultrasonic sensors. Ultrasonic sensors are typically mounted visually on the bumper of a vehicle.

It is known from DE 102014221990 a1 to sense the surroundings of a vehicle by means of a vehicle-based surroundings sensing device, to measure the geometry of a crash-related structure of a roadway surface in the surroundings, to compare the geometry of the crash-related structure with the current configuration of the vehicle, and to output a signal if the comparison yields that a crash is expected between the structure and the rim of the vehicle and/or the underside of the vehicle and/or the spoiler of the vehicle. The surroundings sensor device is preferably arranged on the vehicle housing, i.e. in the region of the vehicle bumper, and can be configured as an ultrasonic sensor.

Disclosure of Invention

For autonomous driving, the environment recognition should be improved by sensors that are as inexpensive as possible. In addition, the safety of special situations, such as the start of autonomous driving, should be better ensured.

According to a first aspect of the present invention, a method for sensing the surroundings of a vehicle is presented, the method comprising the steps of:

-receiving at least one acoustic signal from the vehicle surroundings by means of at least one vehicle-bound acoustic sensor and optionally by means of a vehicle-bound additional receiver,

-analytically evaluating the received signal and determining at least one characteristic of the surroundings from the analytical evaluation,

in accordance with the invention, at least one acoustic sensor that is bound by the vehicle is arranged in the underbody region of the vehicle in such a way that the received acoustic signals are reflected at least partially by the roadway surface from the region of the vehicle surroundings to the acoustic sensor that is bound by the vehicle.

Preferably, before the step of receiving at least one acoustic signal from the vehicle surroundings, the acoustic signal is transmitted by means of at least one acoustic sensor that is secured to the vehicle, wherein the transmitting acoustic sensor is arranged in the underbody region of the vehicle in such a way that the transmitted acoustic signal is at least partially reflected by the roadway surface into the region of the vehicle surroundings, wherein the received signal comprises an echo signal of the transmitted signal. In particular, the transmitting acoustic sensor can also be used to receive acoustic signals from the surroundings of the vehicle. In other words, the sensor unit can function both as a transmitter and as a receiver.

The surroundings of the vehicle are in particular a traffic lane in the vicinity around the vehicle body or around the outer contour of the vehicle. The surroundings of the vehicle may also include surfaces adjoining this vicinity and/or include regions below the vehicle, for example regions in front of a tire (the so-called tire track to be driven over (reifenpur)) in the direction of travel. The characteristic of the surroundings can be, for example, information about: whether obstacles are present in the surroundings and what type of obstacles and/or how large the distance of the obstacles with respect to the own vehicle and at which position with respect to the own vehicle are. Alternatively or additionally, the characteristics of the surroundings may also comprise the current state of the roadway surface, for example roughness and/or friction values and/or wetness and/or snow and/or ice.

The acoustic sensor, which may be designed in particular as an ultrasonic sensor, is therefore fastened to the underbody of the vehicle and is oriented in such a way that the acoustic cone (Schallkegel) of the acoustic sensor, or the reception range thereof, is oriented on the traffic lane in such a way that the received and, if necessary, transmitted sound is at least partially reflected by the traffic lane surface. The acoustic signal can thus pass largely unhindered from the body region of the vehicle into the surroundings of the vehicle and from there to the sensor. In particular, the acoustic sensor does not point vertically downward, but rather has an azimuth angle or an inclination angle, as a result of which the transmitted acoustic signals are reflected by the roadway surface into the surroundings of the vehicle. If the acoustic signal impinges there on an object, for example, an echo signal is generated which is reflected back to the sensor on substantially the same path.

Preferably, the evaluation of the received acoustic signals includes determining at least one property of the roadway surface. In particular, the characteristics of the roadway surface are preferably determined by determining the noise level of the received signal. From the noise level, characteristics of the roadway surface, in particular the roughness and/or the humidity of the roadway surface and/or other characteristics of the roadway surface, can be determined.

It is also particularly advantageous for the acoustic sensor to be arranged such that its acoustic cone is at least partially aligned with the tire track to be traveled over. Thereby, the traffic lane conditions can be sensed particularly effectively (e.g. wet, ice and snow by tire noise and scattered ground echoes). It is furthermore possible to sense whether an obstacle (for example a small animal, a stone, a human toe) is present in the track of the tire to be driven over. Furthermore, different roadway coverings (e.g. cement, closed-pore or open-pore bitumen) can be sensed, wherein the influence of shoulders, railway tracks or roadway markings can be reduced. Furthermore, lane conditions (e.g. wet, icy, snowy, dirty, etc.) which are decisive for the frictional contact with the tires can be distinguished and identified.

In a preferred embodiment of the invention, the evaluation of the received echo signals includes the determination of the signal transit time, wherein in particular objects in the surroundings of the vehicle are identified. It is sufficient here that, when the sound cone is directed partially directly at the object to be recognized, this results in a particularly large range of action of the sensor, since the sound can reach the sensor itself both directly and via reflections from the roadway surface, wherein the reflections from the object likewise return to the sensor both directly and indirectly via the roadway reflections. The object can therefore preferably be identified by evaluating a first echo signal of a first signal component of the transmitted acoustic signal, which is reflected on the roadway surface before it strikes the object, and evaluating a second echo signal of a second signal component of the transmitted acoustic signal, which directly strikes the object.

It is also advantageous to use, in addition to the acoustic sensor in the underbody, a sensor which is located higher, for example in the bumper of the vehicle or in one side, for example in a door sill or a door of the vehicle, in order to thus sense objects and road conditions by means of scattered cross echoes of the roadway surface. This has the following advantages: not only the direct reflection characteristic but also the indirect reflection characteristic of the traffic lane can be measured, and further information about the road state can be obtained from the proportional relationship of the two parts and thus the road state can be determined more accurately and more reliably. Further, due to the different sound propagation paths, the sound reflected at the road surface may be positively or negatively superimposed (interfered) with the directly transmitted sound. By additionally evaluating these so-called cross echoes, the following opportunities are even greater: benefits can be gained from the positive interference effect of the sound waves, i.e. positive superposition, which favors a larger range of action.

Further preferably, the reflected acoustic echo signal may be received by at least one first receiver and the first time of flight may be determined, and the reflected acoustic signal may be received by at least one second receiver and the second time of flight may be determined. The first receiver may be the transmitting sensor itself and the second receiver may be an additional acoustic sensor, which is located at another location on the vehicle. By evaluating the first and second transit times analytically, the relative position of the reflecting object with respect to the transmitter and/or receiver can be determined. For example, the first receiver is arranged as part of an acoustic sensor in the underfloor region of the vehicle, and the second receiver is arranged on an outer surface of the vehicle, in particular on a side face of the vehicle.

According to a second aspect of the invention, a device for sensing the surroundings of a vehicle is proposed, wherein the device is configured for carrying out the method configured as described above. The apparatus comprises:

at least one acoustic sensor, in particular an ultrasonic sensor, which is fastened to the vehicle and is designed for transmitting acoustic signals, in particular ultrasonic signals, and for receiving acoustic signals, in particular ultrasonic signals;

a control unit configured for operating the acoustic sensor;

a computing unit, which is designed to evaluate the received acoustic echo signals and to determine at least one property of the surroundings from the evaluation.

According to the invention, the at least one acoustic sensor may be arranged in a underbody region of the vehicle in such a way that the transmitted acoustic signals are reflected at least partially by the surface of the traffic lane into the region of the vehicle surroundings.

According to another aspect of the invention, a vehicle having such an apparatus is proposed.

Particularly advantageous is the position of the acoustic sensor in the underbody of the vehicle: in this position, the sensor does not protrude beyond the underbody covering. Thus, the ground clearance is preserved and the sensor is not scratched by obstacles on the traffic lane. According to the invention, the sensor surface, i.e. the surface of the sensor (usually a diaphragm) that emits the acoustic signal and receives the reflected acoustic signal, is not mounted flat in the horizontal plane of the vehicle floor, but is arranged at an inclination relative to the roadway surface in such a way that the corresponding acoustic cone is at least partially reflected by the roadway surface into the region of the vehicle surroundings.

Preferably, a horn (Trichter) is also arranged around the sensor surface or the diaphragm surface, which horn directs the received echo signals to the sensor surface. The horn may be shaped, for example, in an animal-horn like manner. For space reasons, the animal-like member may be rolled or folded around itself. The sound is thus coupled by means of an index line (exponentialleiituung) through the sound channel, which is located between the sensor and the surroundings and which increases continuously in cross section. Here, it is preferable to match the wave impedance of the sensor to the acoustic characteristic impedance of the ambient air. In this way, a higher range of action can be achieved in echo location and thus in the sensing of objects and the road state can also be distinguished more accurately.

Acoustic sensors typically used in motor vehicles have a diaphragm as the sensor surface, which serves both for generating and receiving acoustic signals. To generate an acoustic signal, the diaphragm is excited by the transducer elements to vibrate, thereby generating an acoustic signal. In order to receive acoustic signals, the vibrations of the membrane caused by incident sound are sensed by means of transducer elements. After the acoustic signal has been generated, the diaphragm must first return to a rest state before an incoming acoustic signal can be received by means of the diaphragm. The time from the end of the excitation of the membrane until the state of rest is reached is referred to as the vibration decay time (Ausschwingzeit). The vibration decay time of the diaphragm causes that objects which are particularly close to the acoustic sensor cannot be identified or can only be identified with low reliability. However, firstly, it should be possible to reliably detect before the start of autonomous driving, for example, whether an object is present on the track of the tire to be driven over or very close to the vehicle, so that it can be prevented from being rolled over. For example, a person leaning against the vehicle before the start of driving is identified, so that the person can thus be prevented from being run over. For this reason, it is advantageous to move the acoustic sensor in the horizontal plane as far away from the vehicle contour in the direction of the center axis, so that the distance between the sensor or the sensor surface or the diaphragm and the object to be detected is greater than a minimum distance for object detection, which is derived in a known manner from the vibration damping time of the sensor after the transmission of the acoustic signal. The minimum distance is dependent on the structure of the sensor and on the transmission frequency and transmission mode and can be, for example, 12cm to 19cm in conventional ultrasonic sensors. The acoustic sensor is preferably arranged on the underbody of the vehicle in such a way that the sensor surface or the diaphragm of the sensor has a defined minimum distance to the outer contour of the vehicle or to the tire path to be traveled over, wherein the minimum distance is determined by the vibration damping time of the acoustic sensor.

Preferably, the acoustic sensor is arranged in a recess in the underbody covering and/or on a reinforcing element on the underbody of the vehicle. Advantageously, therefore, already existing recesses and surface portions in the underbody shield (whose normal vectors point approximately in the desired propagation direction) can be selected as sensor positions. Here, the offset (abbeichung) for forming the optional horn is also easier to achieve than on surfaces oriented parallel to the roadway, so that an additional large recess for the horn must be implemented. Advantageously, an installation location is selected which is less affected by large temperature fluctuations as occur in the vicinity of the engine and the exhaust system. Thereby, a better fatigue strength of the sensor may be achieved.

Preferably, the plurality of acoustic sensors are arranged on the underbody of the vehicle, wherein the at least one first sensor is arranged in a vehicle front region on the underbody of the vehicle and the at least one second sensor is arranged in a vehicle rear region on the underbody of the vehicle. At least one third sensor is arranged in a first lateral region of the vehicle on the underbody of the vehicle and at least one fourth sensor is arranged in a second lateral region of the vehicle on the underbody of the vehicle. By this arrangement, a largely complete coverage of the vehicle surroundings by the acoustic sensor is obtained.

The following advantages are obtained in particular by the invention:

the sensor is not visible from the usual position when viewing the vehicle and thus does not limit the design of the vehicle.

The functional capability of the method or device according to the invention is independent of the vehicle design, so that the costs are reduced when the system is used in different vehicle variants.

The vehicle manufacturer gains freedom in the configuration of the visible vehicle skin in such a way that the acoustic sensor can be transferred from the visible bumper region into the invisible underbody region.

The acoustic sensor is better protected against parking scratches and damage.

By using a further acoustic sensor mounted at a higher position on the vehicle, the range of action can be increased overall, since the signal components reflected on the roadway surface increase and the chance of positive interference increases in particular in the case of combined evaluation by means of a higher-position sensor and a lower-mounted acoustic sensor.

The opening angle of the acoustic sensor in the vicinity is greater, since the sound component scattered at the surface of the traffic lane increases with lower height.

Blindness detection (that is to say identification of whether the individual sensors are defective or soiled) is more robust, since ground and vehicle components return clearer echoes and multiple echoes that can be taken into account for comparison measurements.

The use of a sound-reinforcing horn makes it possible to achieve a higher sensitivity of the acoustic sensor in general and additionally a stronger focusing and thus a significantly higher range of action.

Particularly effective and reliable object recognition can be achieved in the immediate vicinity of the reflecting roadway surface, since these objects can be recognized both by direct echoes and by echoes reflected indirectly via the roadway surface.

Together with sensors not installed in the vehicle bottom, the height position of the object can also be calculated by triangulation. It is thus possible to better distinguish between drivable obstacles and non-drivable obstacles.

Higher sensing robustness against so-called false objects (geosterobjekt) caused by special traffic lane structures, such as manhole covers. Since the remote manhole cover often appears as an object and thus erroneously as an obstacle for an acoustic sensor that is not mounted on the vehicle bottom.

It is also possible to identify objects which are in close proximity to the vehicle or which are in contact with the vehicle at a very small distance.

Drawings

Fig. 1 schematically shows a vehicle according to a first embodiment of the invention in a front view.

Fig. 2 schematically shows a vehicle according to a second embodiment of the invention in a front view.

Fig. 3 schematically shows a vehicle according to a third embodiment of the invention in a front view.

Fig. 4 schematically shows a vehicle according to a fourth embodiment of the invention in a front view.

Fig. 5 schematically shows a bottom view of a vehicle according to a fifth embodiment of the invention.

Fig. 6 shows a schematic representation of a typical underbody of a motor vehicle with a mounting location for an acoustic sensor according to the invention.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the embodiments of the present invention, the same elements are denoted by the same reference numerals, and repeated description of these elements is omitted as necessary. The figures only schematically show the subject matter of the invention.

Detailed Description

Fig. 1 illustrates a vehicle 10 in a front view. The vehicle has an acoustic sensor 14, which is designed as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10. The vehicle-bound acoustic sensor 14 is attached to the floor 12 of the vehicle 10 in such a way that it protrudes beyond the outer contour 18 of the vehicle 10. The acoustic sensor 14 is inclined relative to the floor plane 22 of the vehicle 10 in such a way that the acoustic signal 16 emitted by the sensor 14 is at least partially reflected by the roadway surface 20 into the surroundings 30 of the vehicle. Ultrasonic sensors typically transmit sound into a generally conical region. In this diagram, the transmitted signal 16 is schematically illustrated by

lines

16a and 16b bounding the cone of sound. As a result of the reflection of the transmitted signal 16 on the roadway surface 20, the sound cone expands, which leads to an increase in the measuring range. The echo signal can be received from the entire acoustic cone. The echo signals are returned to the sensor 14 by being reflected again, if necessary, on the roadway surface 20. The illustrated system thus senses objects in the surroundings 30 of the vehicle 10 and/or determines the current traffic lane state by evaluating the echo signals generated by the traffic lane 20, for example. For this purpose, a control unit 40 is provided, which is designed to control the acoustic sensor 14, and a computation unit 50 is provided, which is designed to evaluate the received acoustic echo signals and to determine at least one property of the surroundings 30 from the evaluation.

Fig. 2 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14, which is designed as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10. In contrast to the exemplary embodiment according to fig. 1, in this exemplary embodiment the installation location and the installation angle or the inclination of the sensor 14 are selected such that the acoustic signal 16 emitted by the sensor 14 is partially reflected by the roadway surface 20 into the surroundings 30 of the vehicle and partially emitted directly into the surroundings 30 of the vehicle 10. For this purpose, in the exemplary embodiment according to fig. 1, a smaller mounting angle and a mounting location closer to the outer contour 18 of the vehicle are selected. Here, the mounting angle or inclination of the sensor 14 refers to the angle between the vehicle floor plane 22 and the main radiation direction of the acoustic sensor 14. An object 80 is present in the surroundings 30 of the vehicle 10. The object 80 may be identified by: a first echo signal of a first signal component 16c of the transmitted acoustic signal is evaluated, wherein the first signal component 16c is reflected on the roadway surface 20 before it strikes the object 80. Furthermore, a second echo signal of a second signal component 16d of the transmitted acoustic signal 16 is evaluated, wherein the second signal component 16d directly strikes the object 80. By this arrangement, the signal can be enhanced by positive superposition and echoes of distant or weakly reflecting objects can still be sensed, in particular in the case of strong ambient noise generated by the tire, for example in the case of wet roads and high speeds.

Fig. 3 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14, which is designed as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10, in particular in the same way as shown in fig. 1. Additionally, in this embodiment, the vehicle 10 also has a second acoustic sensor 44 on the side 25 of the vehicle 10. The acoustic sensor 14 is inclined relative to the floor plane 22 of the vehicle 10 in such a way that the acoustic signal 16 emitted by the sensor 14 is reflected at least partially by the roadway surface 20 into the surroundings 30 of the vehicle. For example, echo signals 46 generated by the roadway surface in the region 26 of the roadway surface are returned to the first acoustic sensor 14 and can be evaluated by evaluation using the computing unit 50. Additionally, by the sound reaching the roadway surface 20, the second echo signal 46 is reflected to the second acoustic sensor 44. The second echo signal 46 can also be evaluated by evaluation unit 50. By combined evaluation, accurate information about the current state of the roadway surface 20 in the region 26 can be obtained.

There are also objects 80 in the surroundings 30 of the vehicle 10. The object 80 may be identified by: a first echo signal 36 'of the transmitted acoustic signal 16 is received by the acoustic sensor 14 and subsequently evaluated by the evaluation unit 50, wherein the echo signal 36' is reflected by the roadway surface 20 before it strikes the sensor 14. The calculation unit may for example determine the transit time of the signal. Furthermore, a second echo signal 46 ' of the transmitted acoustic signal 16 is received by the receiver 44 and is also evaluated by the computation unit 50, wherein the two echo signals 36 ' and 46 ' can also be evaluated in a combined manner. In particular, with this arrangement, it is possible to determine not only the distance from an object 80 located in the surroundings 30 of the vehicle 10, but also the height and/or the relative position of this object 80 with respect to the

acoustic sensors

14 and 44.

Fig. 4 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14, which is designed as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10. In contrast to the exemplary embodiment according to fig. 1, in this exemplary embodiment the mounting location of the sensor 14 is shifted in the direction of the vehicle center axis 11. The following advantages are thereby obtained: objects that are very close to the vehicle 10 can also be reliably detected, since the distance to the acoustic sensor 14 is always sufficiently large that the echo signal of such an object does not hit the sensor 14 until after the vibration of the sensor diaphragm of the acoustic sensor 14 has decayed for a long time.

In the exemplary embodiment of the invention shown in fig. 5, a plurality of

acoustic sensors

14a,14b,14c,14d, which may be embodied as ultrasonic sensors, for example, are arranged on the underbody of the vehicle. In this case, five sensors 14a are arranged in the front region of the vehicle 10 on the underbody 12 of the vehicle 10. The five sensors 14a are oriented at different angles to the longitudinal axis 13 of the vehicle and therefore cover the area in front of the vehicle 10 in a planar manner with their measuring ranges. In a similar manner, on the underbody 12 of the vehicle 10, five further ultrasonic sensors 14b are also arranged in the rear region of the vehicle 10. These sensors 14b are also oriented at different angles to the longitudinal axis 13 of the vehicle and therefore cover the area behind the vehicle 10 in a planar manner with their measuring range. On the floor 12 of the vehicle 10, three further sensors 14c are arranged in a first lateral region of the vehicle 10. The three sensors 14c are oriented at different angles to the transverse axis 17 of the vehicle and therefore cover the area on the right side of the vehicle in a planar manner with their measuring range. On the floor 12 of the vehicle 10, three further sensors 14d are arranged in the second lateral region of the vehicle 10. The three sensors 14d are likewise oriented at different angles to the transverse vehicle axis 17 and therefore cover the area on the left side of the vehicle 10 in a planar manner with their measuring range.

A vehicle component, such as a wheel 15, located within the acoustic cone region of one of the sensors produces a continuous echo signal and, in part, multiple echoes. These components can be concealed (ausblenden) when identifying objects, since they are known, but they can be used for blindness detection (blindeitsdetection), in order to identify, for example, the adverse effect on the sensor range due to contamination and, if necessary, also to be able to compensate for this.

Fig. 6 shows a bottom 12 of a typical motor vehicle 10. The underbody 12 has, in a known manner, an underbody covering 64 and respectively different covering elements 65 and has reinforcing elements 66, sound-attenuating elements 69 and flow-shaping elements 68. These elements may in turn have or constitute a notch 62 suitable for accommodating the acoustic sensor 14 in order to construct the device of the invention.

Claims

1. A method for sensing a surrounding environment (30) of a vehicle (10), the method comprising the steps of:

-receiving at least one acoustic signal (36,46) from the surroundings (30) of the vehicle by means of at least one acoustic sensor (14) that is tethered to the vehicle,

-analytically evaluating the received signals and determining at least one characteristic of the surroundings (30) from the analytical evaluation,

characterized in that the at least one vehicle-bound acoustic sensor (14) is arranged in the region of the underbody (12) of the vehicle (10) in such a way that the received acoustic signals (36,46) are reflected at least partially by a roadway surface (20) from a region of the surroundings (30) of the vehicle (10) to the vehicle-bound acoustic sensor (14), wherein the surroundings (30) of the vehicle (10) comprise in particular a roadway in the vicinity around the body of the vehicle and/or comprise a region below the vehicle (10).

2. Method according to claim 1, characterized in that, prior to the step of receiving the at least one acoustic signal (36,46) from the surroundings (30) of the vehicle, an acoustic signal (16) is transmitted by means of at least one vehicle-bound acoustic sensor (14), wherein the transmitting acoustic sensor (14) is arranged in the region of the underbody (12) of the vehicle (10) in such a way that the transmitted acoustic signal (16) is reflected at least partially by the roadway surface (20) into the region of the surroundings (30) of the vehicle (10), wherein the received signal (36,36 ', 46, 46') comprises an echo signal of the transmitted signal (16).

3. The method according to claim 1 or 2, characterized in that the analytical evaluation of the received signals (16) comprises determining at least one characteristic of the roadway surface (20).

4. Method according to claim 3, characterized in that the property of the traffic lane surface (20) is determined by ascertaining a noise level of the received signal (16), wherein a property of the traffic lane surface (20), in particular a roughness and/or a humidity of the traffic lane surface (20), is determined from the noise level.

5. Method according to one of claims 2 to 4, characterized in that the evaluation of the received signals comprises a determination of the signal transit time of at least one echo signal of the transmitted acoustic signals (16), wherein in particular objects (80) in the surroundings (30) of the vehicle (10) are identified.

6. Method according to claim 5, characterized in that an object (80) is identified by evaluating the superposition of a first echo signal of a first signal component (16c) of the transmitted acoustic signal (16) and a second echo signal of a second signal component (16d) of the transmitted acoustic signal (16), wherein the first signal component (16c) is reflected on the roadway surface (20) before it strikes the object (80), wherein the second signal component (16d) directly strikes the object (80).

7. The method according to claim 5 or 6, characterized in that the first echo signal (36') is received by at least one first receiver and the first transit time is determined, and a second echo signal (46') is received by at least one second receiver (44) and a second transit time is determined, wherein the relative position of the reflecting object (80) with respect to the transmitting sensor (14) and/or with respect to the receiver (14,44) is determined by evaluating the first and second times of flight, wherein the first receiver is arranged as part of an acoustic sensor (14) in the region of the underbody (12) of the vehicle (10), and the second receiver (44) is arranged on an outer surface (25) of the vehicle (10), in particular on a side of the vehicle (10).

8. Method according to one of claims 1 to 7, wherein a first acoustic signal is received by at least one first receiver from a region (26) of the traffic lane surface (20) and a second acoustic signal is received by at least one second receiver (44) from the region (26) of the traffic lane surface (20), wherein the first receiver is arranged as part of an acoustic sensor (14) in the region of the underbody (12) of the vehicle (10) and the second receiver (44) is arranged on an outer surface (25) of the vehicle (10), in particular on a side of the vehicle (10).

9. An apparatus for sensing the surroundings (30) of a vehicle (10), wherein the apparatus is configured for performing the method according to one of claims 1 to 8, the apparatus comprising:

-at least one acoustic sensor (14) that is vehicle-bound and is designed for receiving acoustic signals, in particular ultrasonic signals;

-a control unit (40) configured for manipulating the acoustic sensor (14) restrained by the vehicle;

a computing unit (50) configured for the analytical evaluation of the received acoustic signals and for the determination of at least one characteristic of the surroundings (30) from the analytical evaluation;

characterized in that the at least one acoustic sensor (14) which is bounded by the vehicle can be arranged in the region of the underbody (12) of the vehicle (10) in such a way that the received acoustic signals (16) are reflected at least partially from the region of the surroundings (30) of the vehicle by the roadway surface (20) to the acoustic sensor (14), wherein the surroundings (30) of the vehicle (10) comprise in particular a roadway in the vicinity of the body surroundings and/or a region below the vehicle (10).

10. The device according to claim 9, characterized in that the acoustic sensor (14) is configured as an ultrasonic sensor.

11. The device according to claim 9 or 10, wherein the acoustic sensor (14) has a sensor surface, in particular a diaphragm, wherein a funnel is arranged around the sensor surface, which funnel is designed to guide sound to the sensor surface and is in particular shaped in such a way that the wave impedance of the sensor is matched to the sound characteristic impedance of the surrounding air and the received signal is thus intensified.

12. Vehicle (10) having a device according to one of claims 9 to 11.

13. Vehicle according to claim 12, characterized in that at least one acoustic sensor (14) is arranged on the underbody (12) of the vehicle (10) in such a way that the diaphragm of the sensor (14) has a defined minimum distance to the outer contour (18) of the vehicle (10), wherein the minimum distance is determined by the vibration damping time of the diaphragm of the acoustic sensor (14).

14. Vehicle according to claim 12 or 13, characterized in that the minimum spacing relative to an outer contour (18) of the vehicle (10) is 12-19 cm.

15. Vehicle according to one of claims 12 to 14, characterized in that the acoustic sensor (14) is arranged in a cutout (62) of a floor covering (64) and/or on a stiffening element (66) on the floor (12) of the vehicle (10).

16. Vehicle according to one of claims 12 to 15, characterized in that a plurality of acoustic sensors (14a,14b,14c,14d) are arranged on the floor (12) of the vehicle (10), wherein at least one first sensor (14a) is arranged on the floor (12) of the vehicle (10) in a front region of the vehicle (10), at least one second sensor (14b) is arranged on the floor (12) of the vehicle (10) in a rear region of the vehicle (10), at least one third sensor (14c) is arranged on the floor (12) of the vehicle (10) in a first lateral region of the vehicle (10), and at least one fourth sensor (14d) is arranged on the floor (12) of the vehicle (10) in a second lateral region of the vehicle (10).