CN111308475B

CN111308475B - Method and device for sensing the surroundings of a vehicle and vehicle having such a device

Info

Publication number: CN111308475B
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: 2024-06-04
Anticipated expiration: 2039-12-12
Also published as: DE102018221517A1; CN111308475A

Abstract

The invention relates to a method for sensing vehicle surroundings, the method comprising the following steps: receiving at least one acoustic signal (36, 46) from the vehicle surroundings (30) by means of at least one vehicle-bound acoustic sensor (14); evaluating the received signal and determining at least one property of the surroundings (30) based on the 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) such that the received acoustic signal (16) is at least partially reflected by a road surface (20) from the region of the vehicle surroundings (30) to the vehicle-bound acoustic sensor (14), wherein the vehicle surroundings (30) in particular include the roadway in the vicinity of the vehicle body and/or include a region under the vehicle (10). The invention also relates to a device and a vehicle having the device.

Description

Method and device for sensing the surroundings of a vehicle and vehicle having such a device

Technical Field

The invention relates to a method for sensing the surroundings of a vehicle in such a way that: at least one acoustic signal reflected from the surroundings of the vehicle is received by means of at least one acoustic sensor and/or by means of an additional receiver bound to the vehicle, and the received echo signals are evaluated analytically and at least one characteristic of the surroundings is determined from the evaluation. The invention also relates to a device configured for carrying out the method of the invention. The invention also relates to a vehicle having such a device.

Background

Today, a large number of sensors are required for autonomous driving, among which there are lidar sensors, camera sensors, radar sensors and ultrasonic sensors. The ultrasonic sensor is typically mounted visibly on the bumper of the vehicle.

It is known from DE 10 2014 221 990 A1 to sense the surroundings of a vehicle by means of a vehicle-based surroundings sensor, to measure the geometry of a crash-related structure of the 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 vehicle floor and/or the spoiler of the vehicle. The ambient 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 of as low cost as possible. Furthermore, safety of special conditions, 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 surrounding environment from the analytical evaluation,

Wherein according to the invention at least one vehicle-bound acoustic sensor is arranged in the underbody region of the vehicle in such a way that the received acoustic signal is at least partially reflected by the roadway surface from the region of the vehicle surroundings to the vehicle-bound acoustic sensor.

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 bound to the vehicle, wherein the transmitting acoustic sensor is arranged in the region of the vehicle bottom 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 may also be used to receive acoustic signals from the surroundings of the vehicle. In other words, the sensor unit may function as both a transmitter and a receiver.

The surroundings of the vehicle refer here in particular to the traffic lane in the vicinity around the body or the outer contour of the vehicle. The surroundings of the vehicle may also comprise a surface adjoining this vicinity and/or an area underneath the vehicle, for example an area in front of the tire in the direction of travel, a so-called tire track (Reifenspur) to be driven over. The characteristics of the surrounding environment may be, for example, information about: whether or not there are obstacles in the surrounding environment, and what type of these obstacles are and/or how large these obstacles are relative to the distance of the host vehicle and in what position relative to the host vehicle. Alternatively or additionally, the characteristics of the surroundings may also comprise the current state of the surface of the roadway, such as roughness and/or friction values and/or wetness and/or snow and/or ice.

The acoustic sensor, which can be designed in particular as an ultrasonic sensor, is therefore fastened to the vehicle floor of the vehicle and is oriented in such a way that the Sound Cone (SCHALLKEGEL) of the acoustic sensor or its receiving range is oriented onto the traffic lane in such a way that the received and optionally transmitted sound is at least partially reflected by the traffic lane surface. The acoustic signals can thus pass largely unimpeded from the body region of the vehicle into the surroundings of the vehicle and from the surroundings to the sensor. The acoustic sensor is not directed vertically downward, but rather has an azimuth angle or inclination, as a result of which the transmitted acoustic signal is reflected by the roadway surface into the surroundings of the vehicle. If the acoustic signal impinges there, for example, on an object, an echo signal is generated, which is reflected back to the sensor substantially on the same path.

Preferably, the analytical evaluation of the received acoustic signal comprises determining at least one characteristic of the surface of the roadway. It is particularly preferred that the characteristics of the surface of the roadway are determined by ascertaining 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 if the acoustic sensor is arranged such that its acoustic cone is at least partially aligned with the tire track to be travelled over. Thus, the traffic lane condition can be sensed particularly effectively (e.g., moisture, ice and snow are sensed by tire noise and scattered ground echoes). It is furthermore possible to sense whether an obstacle (e.g. small animal, stone, human toe) is present in the tire track to be driven over. Furthermore, different roadway covers (e.g., cement, closed-cell or open-cell asphalt) may be sensed, wherein the impact of road shoulders, railway tracks or roadway markings may be reduced. Furthermore, traffic lane states (e.g., wet, frozen, snowy, soiled, etc.) that are decisive for frictional contact with the tire can be distinguished and identified.

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

In addition to acoustic sensors in the vehicle bottom, it is also advantageous to use sensors in the vehicle's bumper or in one side, for example in the door sill or in the door, for example, in a higher position, in order to thus sense objects and road states by 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 superimposed or negatively superimposed (interfered) with the directly transmitted sound. By additionally analyzing and evaluating these so-called cross echoes, the following opportunities are greater: can benefit from positive interference effects, i.e. positive superposition, of sound waves favoring a larger range of action.

Further preferably, the reflected acoustic echo signal may be received by at least one first receiver and a first transit time may be determined, and the reflected acoustic signal may be received by at least one second receiver and a second transit time may be determined. The first receiver may be the transmitting sensor itself and the second receiver may be an additional acoustic sensor 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 the acoustic sensor in the underbody region of the vehicle, and the second receiver is arranged on the outer surface of the vehicle, in particular on the side 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 performing the method configured as described above. The apparatus comprises:

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

-a control unit configured for manipulating the acoustic sensor;

-a computing unit configured for analytically evaluating the received acoustic echo signals and determining at least one characteristic of the surrounding environment from the analytical evaluation.

According to the invention, the at least one acoustic sensor can be arranged in the region of the vehicle bottom 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.

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

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 cover. Therefore, the ground clearance is preserved and the sensor is not scratched by an obstacle on the traffic lane. According to the invention, the sensor surface, i.e. the surface of the sensor (typically the diaphragm) that emits an acoustic signal and receives a reflected acoustic signal, is not mounted flat in the horizontal plane of the vehicle bottom, but is arranged obliquely to the roadway surface in such a way that the respective 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 or diaphragm face, which horn directs the received echo signals to the sensor face. The horn may be shaped, for example, in the form of a horn. For space reasons, the animal-horn-shaped member may be rolled or folded around itself. The sound is thus coupled by means of an exponential circuit (Exponentialleitung) through a sound channel between the sensor and the surrounding environment that continuously increases in cross section. In this case, the wave impedance of the sensor is preferably matched to the acoustic characteristic impedance of the surrounding air. In this way, a higher range of action can be achieved during echo localization and thus during object sensing, and the road state can also be distinguished more accurately.

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

Preferably, the acoustic sensor is arranged in a recess of the underbody covering and/or on a stiffening element on the underbody of the vehicle. Thus advantageously, the existing grooves and surface portions in the underbody shield (whose normal vectors are directed substantially in the desired direction of propagation) can be selected as sensor positions. The offset (Abweichung) for forming the optional horn is also easier to achieve here than on surfaces oriented parallel to the traffic lane, whereby an additional large recess for the horn must be realized. Advantageously, the installation location is selected to be less affected by large temperature fluctuations as occur in the vicinity of the engine and the exhaust system. Thereby, a better fatigue resistance of the sensor can be achieved.

Preferably, the plurality of acoustic sensors are arranged on a vehicle underbody of the vehicle, wherein the at least one first sensor is arranged in a vehicle front region on the vehicle underbody and the at least one second sensor is arranged in a vehicle rear region on the vehicle underbody. At least one third sensor is arranged in a first lateral area of the vehicle on the vehicle bottom of the vehicle and at least one fourth sensor is arranged in a second lateral area of the vehicle on the vehicle bottom of the vehicle. With this arrangement, it is achieved that the surroundings of the vehicle are largely completely covered by the acoustic sensor.

The following advantages are achieved in particular by the invention:

The sensor is not visible from a common location 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, thereby reducing costs when the system is applied to different vehicle variants.

The vehicle manufacturer obtains freedom in configuring the visible vehicle housing in that the acoustic sensor can be transferred from the visible bumper region into the invisible underbody region.

The acoustic sensor is better protected against scratches and damages.

By using further acoustic sensors mounted at a higher position on the vehicle, the range of action can be increased overall, since the signal component reflected on the surface of the traffic lane increases and the chance of positive interference occurring, in particular in the case of a combined evaluation by means of a higher-positioned sensor and an acoustic sensor mounted at a lower height, increases.

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

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

A horn can be used which intensifies the sound, as a result of which generally a higher sensitivity of the acoustic sensor and additionally a stronger focusing and thus a significantly higher range of action can be achieved.

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 echo and by echo reflected indirectly via the roadway surface.

Along with sensors not mounted in the vehicle bottom, the height position of the object can also be calculated by triangulation. Thus, it is possible to better distinguish between traversable obstacles and obstacles that cannot be traversed.

-A higher sensing robustness against so-called false objects (Geisterobjekt) caused by special traffic lane structures, such as manhole covers. Because the remote manhole cover often appears as an object to an acoustic sensor not mounted on the vehicle bottom and thus appears as an obstacle in error.

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

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 schematically shows a typical underbody of a motor vehicle with an installation 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 descriptions of these elements are omitted if necessary. The figures only schematically illustrate the subject matter of the invention.

Detailed Description

Fig. 1 shows a vehicle 10 in a front view. The vehicle has an acoustic sensor 14 configured as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10. The vehicle-bound acoustic sensor 14 is fastened to the underbody 12 of the vehicle 10 in such a way that it does not protrude beyond the outer contour 18 of the vehicle 10. The acoustic sensor 14 is tilted relative to the underbody surface 22 of the vehicle 10 such that the acoustic signal 16 transmitted by the sensor 14 is reflected at least partially by the roadway surface 20 into the vehicle's surroundings 30. Ultrasonic transducers typically transmit sound into a generally conical region. In this illustration, the transmitted signal 16 is schematically shown by lines 16a and 16b bounding the sound cone. As the transmitted signal 16 is reflected on the traffic surface 20, the sound cone expands, resulting in an increase in the measuring range. Echo signals may be received from the entire cone. The echo signals are returned to the sensor 14 in such a way that they are reflected again on the roadway surface 20 if necessary. Thus, the illustrated system senses objects in the surrounding environment 30 of the vehicle 10 and/or determines the current lane state by analyzing and evaluating echo signals generated by the lane 20, for example. For this purpose, a control unit 40 is provided, which is designed to operate the acoustic sensor 14, and a calculation unit 50 is provided, which is designed to evaluate the received acoustic echo signals and to determine at least one characteristic of the surroundings 30 as a function of the evaluation.

Fig. 2 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14 configured 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 transmitted by the sensor 14 is reflected partly by the roadway surface 20 into the surroundings 30 of the vehicle and partly directly into the surroundings 30 of the vehicle 10. For this purpose, a smaller installation angle and an installation point closer to the outer contour 18 of the vehicle are selected in the embodiment according to fig. 1. The installation angle or inclination of the sensor 14 is here also 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 surrounding environment 30 of the vehicle 10. The object 80 may be identified by: the first echo signal of the first signal component 16c of the transmitted acoustic signal is evaluated, wherein the first signal component 16c reflects 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 touches the object 80. With this arrangement, the signal can be enhanced by positive superposition and echoes of distant objects or weakly reflecting objects can still be sensed, especially in case of strong ambient noise generated by the tire, for example in case of road wetness and high speeds.

Fig. 3 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14 configured 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 tilted relative to the underbody surface 22 of the vehicle 10 such that the acoustic signal 16 transmitted by the sensor 14 is reflected at least partially by the roadway surface 20 into the vehicle's surroundings 30. The echo signal 46 generated by the roadway surface, for example in the region 26 of the roadway surface, is returned to the first acoustic sensor 14 and can be evaluated analytically by means of the computing unit 50. Additionally, the second echo signal 46 is reflected to the second acoustic sensor 44 by sound arriving on the roadway surface 20. The second echo signal 46 can also be evaluated analytically by means of the computing unit 50. By combined analytical evaluation, accurate information about the current state of the roadway surface 20 in the region 26 can be obtained.

An object 80 is also present in the surrounding environment 30 of the vehicle 10. The object 80 may be identified by: the first echo signal 36 'of the transmitted acoustic signal 16 is received by the acoustic sensor 14 and is then evaluated by the computing unit 50 in an analysis, wherein the echo signal 36' is reflected by the roadway surface 20 before it hits the sensor 14. The calculation unit may, for example, determine the transit time of the signal. Furthermore, the second echo signal 46' of the transmitted acoustic signal 16 is received by the receiver 44 and is also evaluated by the computing unit 50, wherein the two echo signals 36' and 46' can also be evaluated in a combined manner. In particular, by this arrangement, not only the distance to the object 80 in the surroundings 30 of the vehicle 10, but also the height and/or the relative position of the object 80 to the acoustic sensors 14 and 44 can be determined.

Fig. 4 shows the vehicle 10 in a front view. The vehicle has an acoustic sensor 14 configured as an ultrasonic sensor, which is arranged on the underbody 12 of the vehicle 10. In this embodiment, in contrast to the embodiment according to fig. 1, the installation site of the sensor 14 is moved in the direction of the central axis 11 of the vehicle. The following advantages are thus obtained: objects that are very close to the vehicle 10 can also be reliably detected, since the distance from the acoustic sensor 14 is always sufficiently large that the echo signals of such objects do not strike the sensor 14 until after a period of vibration attenuation of the sensor diaphragm of the acoustic sensor 14.

In the embodiment of the invention shown in fig. 5, a plurality of acoustic sensors 14a,14b,14c,14d, which can be configured, for example, as ultrasonic sensors, are arranged on the vehicle floor of the vehicle. Here, on the underbody 12 of the vehicle 10, five sensors 14a are arranged in a front region of the vehicle 10. The five sensors 14a are oriented at different angles relative to the longitudinal axis 13 of the vehicle and thus cover the area in front of the vehicle 10 in a planar manner with their measuring range. 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. The sensors 14b are also oriented at different angles relative to the longitudinal axis 13 of the vehicle and thus cover the area behind the vehicle 10 in a planar manner with their measuring range. On the underbody 12 of the vehicle 10, three further sensors 14c are arranged in a first lateral area of the vehicle 10. The three sensors 14c are oriented at different angles relative to the vehicle transverse axis 17 and therefore cover the area on the right side of the vehicle in a planar manner with their measuring range. On the underbody 12 of the vehicle 10, three further sensors 14d are arranged in a second lateral region of the vehicle 10. The three sensors 14d are likewise oriented at different angles relative to the vehicle transverse axis 17 and thus cover the area on the left of the vehicle 10 in a planar manner with their measuring range.

A vehicle component, such as a wheel 15, located in the acoustic cone region of one of the sensors produces a continuous echo signal and multiple echoes are produced in part. These components can be hidden (ausblenden) when the object is detected, since they are known, but they can be used for blind detection (Blindheitsdetektion) in order to detect, for example, adverse effects on the sensor area due to contamination and, if necessary, to compensate for said adverse effects.

In fig. 6, a typical underbody 12 of a motor vehicle 10 is shown. The vehicle bottom 12 has in a known manner a vehicle bottom covering 64 and a respective different covering element 65 and has a stiffening element 66, a sound attenuating element 69 and a flow shaping element 68. These elements may in turn have or constitute indentations 62 adapted to receive acoustic sensors 14 in order to construct the apparatus of the present invention.

Claims

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

Receiving at least one acoustic signal from the surroundings (30) of the vehicle by means of at least one acoustic sensor (14) bound to the vehicle,

Analytically evaluating the received acoustic signal and determining at least one characteristic of the surrounding environment (30) from the analytical evaluation,

Wherein the at least one vehicle-bound acoustic sensor (14) is arranged in the region of the vehicle bottom (12) of the vehicle (10) such that the received acoustic signal is at least partially reflected from the region of the surroundings (30) of the vehicle (10) by the roadway surface (20) to the vehicle-bound acoustic sensor (14),

Wherein, prior to the step of receiving the at least one acoustic signal from the surroundings (30) of the vehicle, an acoustic signal is transmitted by means of at least one vehicle-bound acoustic sensor (14), wherein the acoustic sensor (14) transmitting is arranged in the region of the vehicle bottom (12) of the vehicle (10) such that the transmitted acoustic signal is at least partially reflected by the roadway surface (20) into the region of the surroundings (30) of the vehicle (10), wherein the received acoustic signal comprises an echo signal of the transmitted acoustic signal,

Wherein the analytical evaluation of the received acoustic signal comprises determining a signal transit time of at least one echo signal of the transmitted acoustic signal,

Wherein a first echo signal (36 ') is received by at least one first receiver and a 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 acoustic sensor (14) and/or with respect to the receivers (14, 44) is determined by evaluating the first transit time and the second transit time analytically, wherein the first receiver is arranged as part of the acoustic sensor (14) in the region of the vehicle bottom (12) of the vehicle (10) and the second receiver (44) is arranged on the outer surface (25) of the vehicle (10).

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

3. The method according to claim 2, characterized in that the properties of the roadway surface (20) are determined by taking the noise level of the received acoustic signal, wherein the characteristics of the roadway surface (20) are determined from the noise level.

4. A method according to one of claims 1 to 3, characterized in that an object (80) is identified by evaluating the superposition of a first echo signal of a first signal component (16 c) of the transmitted acoustic signal and a second echo signal of a second signal component (16 d) of the transmitted acoustic signal, wherein the first signal component (16 c) is reflected on the roadway surface (20) before it hits the object (80), wherein the second signal component (16 d) directly hits the object (80).

5. A method according to one of claims 1 to 3, wherein a first acoustic signal is received from the region (26) of the roadway surface (20) by at least one first receiver and a second acoustic signal is received from the region (26) of the roadway surface (20) by at least one second receiver (44), 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 the outer surface (25) of the vehicle (10).

6. A method according to one of claims 1 to 3, wherein the surroundings (30) of the vehicle (10) comprise a roadway in a nearby area around the vehicle body and/or comprise an area under the vehicle (10).

7. A method according to one of claims 1 to 3, wherein an object (80) in the surroundings (30) of the vehicle (10) is identified.

8. The method of claim 5, wherein the second receiver (44) is arranged on a side of the vehicle (10).

9. A method according to claim 3, wherein the characteristic is the roughness and/or humidity of the roadway surface (20).

10. Apparatus for sensing an ambient environment (30) of a vehicle (10), wherein the apparatus is configured for performing the method according to one of claims 1 to 9, the apparatus comprising:

-at least one acoustic sensor (14) bound to the vehicle, configured for receiving an acoustic signal;

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

-a computing unit (50) configured for analytically evaluating the received acoustic signal and determining at least one characteristic of the surrounding environment (30) from the analytical evaluation;

Wherein the at least one acoustic sensor (14) bound to the vehicle can be arranged in the region of the vehicle bottom (12) of the vehicle (10) such that the received acoustic signal is at least partially reflected from the region of the surrounding environment (30) of the vehicle by the roadway surface (20) to the acoustic sensor (14).

11. The device according to claim 10, wherein the acoustic sensor (14) is configured as an ultrasonic sensor.

12. The device according to claim 10 or 11, wherein the acoustic sensor (14) has a sensor face, wherein a horn is arranged around the sensor face, which horn is configured for guiding sound to the sensor face and which horn is shaped such that the wave impedance of the sensor matches the sound characteristic impedance of the surrounding air and the received acoustic signal is thereby reinforced.

13. The apparatus of claim 10 or 11, wherein the acoustic signal is an ultrasonic signal.

14. The apparatus according to claim 10 or 11, wherein the surroundings (30) of the vehicle (10) comprise a roadway in a nearby area around the vehicle body and/or comprise an area under the vehicle (10).

15. The apparatus of claim 12, wherein the sensor face is a diaphragm.

16. A vehicle (10) having an apparatus according to one of claims 10 to 15.

17. The vehicle according to claim 16, characterized in that at least one acoustic sensor (14) is arranged on the vehicle floor (12) of the vehicle (10) such that the membrane of the acoustic sensor (14) has a certain minimum distance with respect to the outer contour (18) of the vehicle (10), wherein the minimum distance is determined by the vibration damping duration of the membrane of the acoustic sensor (14).

18. The vehicle according to claim 17, characterized in that the minimum distance relative to the outer contour (18) of the vehicle (10) is 12cm to 19cm.

19. Vehicle according to one of claims 16 to 18, characterized in that the acoustic sensor (14) is arranged in a cutout (62) of an underbody cover (64) and/or on a stiffening element (66) on the underbody (12) of the vehicle (10).

20. The vehicle according to one of claims 16 to 18, characterized in that a plurality of acoustic sensors are arranged on a vehicle bottom (12) of the vehicle (10), wherein at least one first sensor (14 a) is arranged on the vehicle bottom (12) of the vehicle (10) in a front region of the vehicle (10), at least one second sensor (14 b) is arranged on the vehicle bottom (12) of the vehicle (10) in a rear region of the vehicle (10), at least one third sensor (14 c) is arranged on the vehicle bottom (12) of the vehicle (10) in a first side region of the vehicle (10), and at least one fourth sensor (14 d) is arranged on the vehicle bottom (12) of the vehicle (10) in a second side region of the vehicle (10).