METHOD FOR OPERATING AN ULTRASOUND SENSOR DEVICE FOR MONITORING AN UNDERBODY AREA OF A MOTOR VEHICLE, COMPUTER PROGRAM PRODUCT, COMPUTER-READABLE STORAGE MEDIUM AND ULTRASOUND SENSOR DEVICE

Description

[0001] The invention relates to a method for operating an ultrasonic sensor device for monitoring the underbody area of ​​a motor vehicle using the vehicle's ultrasonic sensor device, in which ultrasonic signals are emitted into the underbody area by means of at least one ultrasonic sensor of the ultrasonic sensor device, and in which the reflected ultrasonic signals are received and evaluated by means of the ultrasonic sensor. The invention further relates to a computer program, a computer-readable storage medium, and an ultrasonic sensor device.

[0002] Checking and monitoring the undercarriage of a vehicle before driving is a task that, in the context of autonomous driving, must be performed by the vehicle itself. The primary goal is to detect vulnerable objects, such as children or animals, before the vehicle starts moving, thus preventing them from being injured. Various sensor systems can be used to detect these objects. For example, cameras or lidar sensors can be employed, although these may require additional precautions due to challenging environmental conditions. Alternatively or additionally, radar and / or ultrasonic sensors can be used. However, ultrasonic sensors often lack sufficient lateral spatial resolution.This leads to a situation where multiple reflections from the underbody cannot be distinguished from relevant object reflections. Furthermore, this can also cause occlusions, meaning that, for example, the vehicle's wheels produce stronger reflections than the actual object, and the object is then no longer detectable in the ultrasound signal.

[0003] Furthermore, calibration can generally be assumed to maintain a constant distance between the sensor and the road surface, as calibration typically only considers the settling time and reflections from the road surface. However, current technology does not account for changes in the vehicle's load. In particular, the load can significantly impact the calibration. Additionally, different vehicle models have varying heights between the underbody and the road surface.

[0004] WO 03 / 016941 A2 discloses an echo signal monitoring device with a plurality of transmitting and receiving units for transmitting signals and receiving the echoes reflected by an external object, and an evaluation unit for estimating the distance from the monitoring device to the external object based on the received echoes, wherein it has an operating state for calculating the relative position of the transmitting and receiving units to each other based on the reflected echoes.

[0005] DE 10 2018 / 130914 A1 relates to a method for operating an ultrasonic sensor device in which an ultrasonic signal is emitted into the floor area of ​​a motor vehicle and an ultrasonic signal is received, and an object is detected by means of an electronic computing device depending on the received ultrasonic signal, wherein a first ultrasonic signal is received in the floor area at a first time and a second ultrasonic signal is received at a second time, and the first ultrasonic signal is compared with the second ultrasonic signal as a comparison curve, and depending on the comparison, wherein a first threshold range is generated depending on the received first amplitudes, the object is detected when a predetermined first number of received first amplitudes of the comparison curve are detected outside the threshold range.

[0006] DE 10 2017 208 268 B3 proposes a method for determining the load state of a vehicle and / or for determining the installation height of at least one ultrasonic sensor of the vehicle, wherein an ultrasonic sensor of the vehicle has at least a first operating mode and a second operating mode, which differs from the first operating mode in at least one operating parameter. The ultrasonic sensor is operated in the first operating mode for environmental sensing. This first operating mode can also be referred to as normal operation or measurement mode. To determine the load state of the vehicle and / or to determine the installation height, the ultrasonic sensor is operated in the second operating mode.The second operating mode is designed to control the ultrasonic sensor in such a way that, compared to the first operating mode, it emits more sound towards the roadway, i.e., the surface on which the vehicle is standing. To determine the vehicle's load and / or its installation height, echo signals reflected from the roadway, known as ground echoes, are evaluated.

[0007] From DE 10 2019 115 133 A1, a method for monitoring an underbody area beneath a vehicle is known, in which measurements are carried out using an ultrasonic sensor device, wherein in each of the measurements at least one ultrasonic sensor is activated to emit an ultrasonic signal into the underbody area and a sensor signal is determined which describes a temporal profile of the received ultrasonic signal, wherein a reference signal is determined on the basis of a first sensor signal determined in a first measurement and the presence of an object in the underbody area is checked by comparing a second sensor signal determined in a subsequent, second measurement with the reference signal, wherein the first sensor signal for determining the reference signal is scaled with a scaling function, wherein an amplitude of the scaling function varies depending on time.

[0008] The object of the present invention is to provide a method, a computer program product, a computer-readable storage medium and an ultrasonic sensor device by means of which more reliable monitoring of an underbody area of ​​a motor vehicle can be achieved.

[0009] This problem is solved by a method, a computer program product, a computer-readable storage medium, and an ultrasonic sensor device according to the independent claims. Advantageous embodiments are specified in the dependent claims.

[0010] One aspect of the invention relates to a method for monitoring the underbody area of ​​a motor vehicle using an ultrasonic sensor device of the motor vehicle. Ultrasonic signals are emitted into the underbody area by means of at least one ultrasonic sensor of the ultrasonic sensor device, and the reflected ultrasonic signals are received and evaluated by means of the ultrasonic sensor. After the motor vehicle is switched off at a first time point, a reference measurement curve for the underbody area is generated and stored as a function of at least one ultrasonic signal.

[0011] It is intended that a measuring range is determined in the reference measurement curve, in which an evaluation is carried out for monitoring the subfloor area, whereby the measuring range is determined as a function of a decay time of the ultrasonic sensor and a ground reflection on the ground surface.

[0012] This allows for more reliable monitoring of the underbody area of ​​a motor vehicle.

[0013] In particular, the measuring range between the vehicle's underbody and the road surface is defined, specifically between the reverberation time and the road surface reflection. This measuring range can be reliably determined by considering the reverberation time and the road surface reflection, thus enabling improved monitoring of the underbody area. Within this measuring range, the system can then be configured to search for objects.

[0014] According to the invention, after a restart of the motor vehicle, a comparison measurement curve is generated at a second time later than the first time, depending on at least one further ultrasound signal, and the reference measurement curve is compared with the comparison measurement curve in the measuring range, and depending on the comparison, the monitoring of the underbody area is carried out by means of an electronic computing device of the ultrasound sensor device.

[0015] According to the invention, it is provided that, depending on the comparison, a change in height between an underbody of the motor vehicle and a ground surface in the underbody area is determined and the change in height is taken into account during the evaluation and monitoring, whereby the change in height between the first time point and the second time point is determined.

[0016] This enables reliable monitoring of the vehicle's underbody. The underbody refers specifically to the area between the road surface on which the vehicle is located and the vehicle's underbody. The proposed method allows the ultrasonic sensor device to be used with various vehicle models, under different load conditions, and even with chassis modifications. This results in greater flexibility for the ultrasonic sensor device, both for fully autonomous operation, such as valet parking, and for assisted operation where the load is significantly influenced by the vehicle's occupants.

[0017] In particular, the invention utilizes the fact that when a vehicle is parked, it can be assumed that no object is present in the underbody area. For this purpose, a reference measurement curve is generated after the vehicle is parked, which is created without any objects present. This allows the height of the vehicle's underbody relative to the road surface to be determined. When the vehicle is restarted, another ultrasonic signal is emitted, and a comparison measurement curve is generated. If an object is now present in the underbody area, it can be detected by comparison. Additionally, a further height can be determined, which might result, for example, from a change in the vehicle's load compared to the first measurement. This change in height is then taken into account when searching for objects in the underbody area.

[0018] According to an advantageous embodiment, the reflected ultrasound signal of the reference measurement curve determines the ground reflection of the road surface, and a first height relative to the road surface is determined based on this ground reflection at the first time point. In the further reflected ultrasound signal of the comparison measurement curve, a ground reflection of the road surface is determined, and a second height relative to the road surface is determined based on this ground reflection at the second time point. By comparing the first and second heights, the change in height is determined. In particular, this allows the ground clearance to be determined for the ultrasound sensor. For this purpose, a measurement signal from the ultrasound sensor is recorded. When the vehicle is parked, it can be assumed that no objects are present in the critical areas, so that the first maximum in the ultrasound signal can be attributed to the road surface.In addition to this reflection, the duration of the decay time can be determined. From these two points, the range for evaluating signals for underbody detection can be adaptively determined. Furthermore, additional parameters can be derived from these two points and their amplitudes. In particular, by determining the first height at the first time point and the second height at the second time point, changes in the load state, for example, can be reliably detected. This makes the method robust to load states, enabling reliable monitoring of the underbody area.

[0019] It is also advantageous to consider the decay time of the ultrasonic sensor when determining height changes. Particularly during the decay time, when the transducer of the ultrasonic sensor device is still oscillating and therefore unsuitable for receiving signals, object detection is impossible. This is now taken into account. Specifically, the ultrasonic sensor is essentially "deaf" during the decay time. By considering this inactivity, reliable monitoring of the vehicle's underbody can be achieved.

[0020] Furthermore, it has proven advantageous to capture at least one environmental condition when generating the reference measurement curve and / or to capture at least one environmental condition when generating the comparison measurement curve, and to consider both the first and / or the second environmental condition when determining the change in height. Environmental conditions, in particular, have a significant influence on the ultrasonic signals. For example, temperature or humidity can significantly affect the corresponding measurement curves. By considering these environmental conditions, the determination of the change in height and object detection can be improved. This allows for reliable monitoring of the subsurface area.

[0021] In a further advantageous embodiment, the ultrasonic signal is emitted from at least one ultrasonic sensor into an area behind a wheel of the vehicle. In particular, the vehicle can have a plurality of ultrasonic sensors distributed throughout the vehicle. These are specifically located behind each wheel. Since the area behind the wheels is a critical zone for driving over objects, it is particularly advantageous to perform appropriate monitoring in this area. Thus, the ultrasonic sensors can improve monitoring of the underbody area. The arrangement of the ultrasonic sensors can also be implemented on other components of the vehicle, for example, in the area of ​​the bumper. In this case, the ultrasonic sensors are specifically oriented from the underbody towards the road surface.

[0022] It is also advantageous if the ultrasonic sensor device comprises a plurality of ultrasonic sensors on the vehicle, whereby the underbody area of ​​the vehicle is monitored by means of the plurality of ultrasonic sensors. Thus, the ultrasonic sensors can perform improved monitoring of the underbody area. This arrangement can be implemented on various components of the vehicle, for example, in the area of ​​the bumper. In particular, the ultrasonic sensors are oriented directly from the underbody towards the road surface.

[0023] It is further advantageous if each reference measurement curve and / or each comparison measurement curve of an ultrasonic sensor from the multitude of ultrasonic sensors is compared and verified with at least one reference measurement curve and / or each comparison measurement curve of another ultrasonic sensor from the multitude of ultrasonic sensors. For example, if the ultrasonic sensor is covered by an object during the generation of the measurement curves, the change in height can still be determined based on the other ultrasonic sensors. In particular, the evaluation of the ultrasonic sensor can then be verified.For example, if multiple ultrasonic sensors detect a corresponding clearance beneath the vehicle, but another ultrasonic sensor does not, this can be verified and appropriate countermeasures, such as generating a warning message for the vehicle's occupant, can be initiated. This enables reliable monitoring of the underbody area.

[0024] According to a further advantageous embodiment, objects driven over within the measurement area during the generation of the reference measurement curve are taken into account during monitoring. For example, if objects such as pieces of wood or stones are present and driven over within the underbody area during the generation of the reference measurement curve, these can be stored in the reference measurement curve as objects that can be driven over and are also taken into account during the monitoring of the underbody area when the vehicle departs. This allows for comprehensive monitoring of the underbody area.

[0025] Furthermore, it has proven advantageous to define a measurement range in the reference measurement curve, increasing the weighting for samples within that range compared to samples outside the range. In particular, adaptive weighting of the samples is proposed for evaluating the measurement signals used in underbody monitoring to enable reliable object detection. A challenge in object detection lies in the varying distances of objects from the ground, as well as their differing reflection characteristics. For example, soft objects tend to "swallow" echoes in the ultrasonic signal, while hard objects generate new reflection peaks. Appropriate weighting can better compensate for this effect and thus significantly improve object detection.

[0026] According to a further advantageous embodiment, a ground reflection range and a decay time of the ultrasonic sensor are determined in the reference measurement curve, whereby the weighting for samples within the ground reflection range is increased compared to samples within the decay time. In particular, since the ultrasonic sensor is essentially inactive during the decay time, little information is available for monitoring the subsoil area during this period. In contrast, the ground reflection range contains potential information, so the weighting is increased in the region of the defined ground reflection range. Thus, improved evaluation and monitoring of the subsoil area can be carried out.

[0027] Furthermore, it has proven advantageous to perform nonlinear weighting over the decay time, the measurement range, and the ground reflection range for monitoring the subsurface area. In particular, this allows information about an object from the decay time, but especially from the ground reflection range, to be integrated into object detection, and the sampled values ​​to be weighted across the entire evaluation range. The entire evaluation range is defined as extending from the decay time through the measurement range to the ground reflection range. Specifically, the influence of each range on object detection is taken into account. The decay time contains very little information about an object, while the area between the decay time and the ground reflection range—in other words, the measurement range—contains the majority of the information, and the ground reflection range itself contains significantly less.Depending on the object's location—for example, very close to the sensor or the settling time, or very close to the ground reflection—the object information can be distributed differently. Therefore, an adaptive weighting approach is proposed. During calibration, both the settling time and ground reflection are measured, with particular attention paid to the amplitude and position, as well as the fluctuations of the corresponding peaks and widths during the calibration period. When examining the subsurface, the settling time and the height of the ground reflection can then be analyzed. Depending on the value of the features, a non-linear weighting of the sampling points can be applied, thus significantly increasing both the sensitivity and robustness of object detection.

[0028] The procedure is, in particular, a so-called computer-implemented procedure.

[0029] Another aspect of the invention relates to a computer program product with program code means which are stored in a computer-readable storage medium in order to carry out the method for monitoring an underfloor area according to the preceding aspect when the computer program product is executed on a processor of an electronic computing device.

[0030] A further aspect of the invention relates to a computer-readable storage medium containing a computer program product according to the preceding aspect. The computer-readable storage medium can, in particular, be configured as part of an electronic computing device.

[0031] The electronic computing device includes, in particular, circuits, such as integrated circuits, processors and other electronic components, which are necessary for processing the computer program product.

[0032] Another aspect of the invention relates to an ultrasonic sensor device for monitoring an underbody area of ​​a motor vehicle, comprising at least one ultrasonic sensor and an electronic computing device, wherein the ultrasonic sensor device is configured to carry out a method according to the preceding aspect. In particular, the method is carried out using the ultrasonic sensor device.

[0033] A further aspect of the invention relates to a motor vehicle with an ultrasonic sensor device according to the preceding aspect. The motor vehicle can be designed to be partially autonomous, and in particular, fully autonomous.

[0034] Advantageous embodiments of the method are to be regarded as advantageous embodiments of the ultrasonic sensor device and the motor vehicle. The ultrasonic sensor device and the motor vehicle possess tangible features that enable the implementation of the method or an advantageous embodiment thereof.

[0035] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims.

[0036] This shows: Fig. 1 a schematic side view of an embodiment of a motor vehicle with an embodiment of an ultrasonic sensor device; Fig. 2 a schematic diagram of a reference measurement curve; Fig. 3 a schematic diagram of a comparison measurement curve; and Fig. 4 a further schematic diagram of a plurality of reference measurement curves.

[0037] In the figures, identical or functionally identical elements are provided with the same reference symbols.

[0038] Fig. 1 Figure 1 shows a schematic side view of an embodiment of a motor vehicle 1 with an embodiment of an ultrasonic sensor device 2. The ultrasonic sensor device 2 comprises, in particular, an electronic computing unit 3 and at least one ultrasonic sensor 4, 5, 6, 7. In the following exemplary embodiment, the ultrasonic sensor device 2 comprises a first ultrasonic sensor 4, a second ultrasonic sensor 5, a third ultrasonic sensor 6, and a fourth ultrasonic sensor 7. The ultrasonic sensor device 2 can also have more than four ultrasonic sensors 4, 5, 6, 7. This is purely exemplary in the exemplary embodiment and should by no means be considered exhaustive.

[0039] Furthermore, in the Fig. 1 It has been shown that the first ultrasonic sensor 4 can be located, for example, in the front area of ​​the motor vehicle 1, for instance, on a bumper of the motor vehicle 1. The second ultrasonic sensor 5 is located behind a front wheel 8. The third ultrasonic sensor 6 is located behind a rear wheel 9. The fourth ultrasonic sensor 7 is located at the rear of the motor vehicle 1, for example, on a bumper of the motor vehicle 1. The locations of the different ultrasonic sensors 4, 5, 6, 7 are also to be understood as purely exemplary. Preferably, however, the ultrasonic sensors 4, 5, 6, 7 are located at least partially in front of and behind the corresponding wheels 8, 9, since these represent the critical areas for driving over objects.It is also advantageous that the ultrasonic sensors 4, 5, 6, 7 are directly aligned from an underbody 10 of the vehicle 1 towards a ground surface 11 on which the vehicle 1 is located. In particular, an underbody area 12 is formed between the underbody 10 and the ground surface 11.

[0040] In a method for monitoring the underbody area 12 of the motor vehicle 1, an ultrasonic signal U ( Fig. 2 ) emitted, and the reflected ultrasonic signals U are received and evaluated by means of the ultrasonic sensor 4, 5, 6, 7, wherein after the motor vehicle 1 is switched off at a first time t 1 ( Fig. 2 ) a reference measurement curve 13 ( Fig. 2 ) for the underbody area 12 is generated and stored depending on at least one ultrasonic signal U. A measuring range 18 ( Fig. 2 ) in the reference measurement curve 13, in which an evaluation for monitoring the underbody area 12 is carried out, wherein the measurement range 18 depends on a settling time 16 ( Fig. 2 ) of the ultrasonic sensor 4, 5, 6, 7 and a ground reflection 19 ( Fig. 2 ) is determined on the floor area 11.

[0041] Furthermore, after a restart of motor vehicle 1 at a second time t 2 later than the first time t 1 ( Fig. 3 ) a comparative measurement curve 14 ( Fig. 3 ) depending on at least one further ultrasound signal U is generated, and the reference measurement curve 13 is compared with the comparison measurement curve 14 and depending on the comparison, the monitoring of the subfloor area 12 is carried out by means of the electronic computing device 3.

[0042] It is provided that, depending on the comparison, a height change Δh between the underbody 10 of the motor vehicle 1 and the ground surface 11 in the underbody area 12 is determined and the height change Δh is taken into account during the evaluation and monitoring, whereby the height change Δh is determined between the first time t 1 and the second time t 2.

[0043] Fig. 2 Figure 1 shows a schematic diagram of a reference measurement curve 13, which was generated at the first time t1. The abscissa shows, in particular, sampled values ​​15 of the ultrasound signals U. The ordinate shows, in particular, the corresponding amplitudes of the ultrasound signal U. The reference measurement curve 13 has the decay time 16, the ground reflection range 17, and the measurement range 18.

[0044] In particular, the ground reflection area 18 exhibits a peak as the ground reflection 19, which, for example, represents the ground itself. Based on the measurement area 18, a first height h1 can be determined, wherein the first height h1 is determined between the subsoil 10 and the ground surface 11 at the first time t 1. A second height h2 ( Fig. 3 ) can be determined in particular during the second time point t 2.

[0045] In particular, the Fig. 2 A typical signal from an ultrasonic sensor 4, 5, 6, 7 when used in the underbody area 12 of the motor vehicle 1. Two areas are particularly clearly identifiable. Firstly, the area of ​​the decay time 16 at the beginning of the signal, and secondly, a distinct signal peak. This signal peak can in turn be attributed to the ground reflection 19. The distance between the two signal characteristics thus determines the area to be evaluated, in particular the measuring range 18, for object detection in the underbody area 12.

[0046] In particular, the end of the decay time 16 is marked by the reference numeral 20 at sample values ​​15, and the peak for the ground reflection 19 is marked by the reference numeral 21 at sample values ​​15. This is the case here at the first time t 1.

[0047] Fig. 3 shows a schematic diagram of the comparison measurement curve 14 at the second time point t 2. In comparison to the ultrasound signal U according to Fig. 2 A difference in the decay time 16 is already apparent. In addition, it is even more clearly visible that the shape, but also the distance of the ground reflection 19, differs significantly from the Fig. 2 In particular, the end of the decay time 16 is marked by reference numeral 22 at sample values ​​15, and the peak for the ground reflection 19 is marked by reference numeral 23 at sample values ​​15. This is shown here for the second time t2. For illustration, reference numerals 20 and 21 are also shown according to Fig. 2 depicted.

[0048] If one were to use the same evaluation or the same evaluation areas or measurement areas 18 as in the Fig. 2 Applying this would lead to errors in the determination and thus also to false detections or the overlooking of objects.

[0049] It is therefore particularly proposed that in the reflected ultrasound signal U of the reference measurement curve 13 the ground reflection 19 of the ground surface 10 is determined and the first height h1 to the ground surface 11 is determined on the basis of the determined ground reflection 19 at the first time t 1 and in the further reflected ultrasound signal U of the comparison measurement curve 14 the ground reflection 19 of the ground surface 11 is determined and the second height h2 to the ground surface 11 is determined on the basis of the determined ground reflection 19 at the second time t 2 and the height change Δh is determined by comparing the first height h1 and the second height h2.

[0050] As already mentioned, the settling time 16 of the ultrasonic sensor 4, 5, 6, 7 can be taken into account when determining the change in height Δh. In particular, it can also be provided that at least one first environmental condition is recorded when generating the reference measurement curve 13 and / or at least one second environmental condition is recorded when generating the comparison measurement curve 14, and that the first environmental condition and / or the second environmental condition are taken into account when determining the change in height Δh. For example, temperatures or humidity values ​​can be considered as environmental conditions.It may further be provided that a respective reference measurement curve 13 and / or a respective comparison measurement curve 14 of an ultrasonic sensor 4, 5, 6, 7 of the plurality of ultrasonic sensors 4, 5, 6, 7 is compared and verified with at least one respective reference measurement curve 13 and / or a respective comparison measurement curve 14 of another ultrasonic sensor 4, 5, 6, 7 of the plurality of ultrasonic sensors 4, 5, 6, 7. In particular, objects that can be driven over can also be taken into account when generating the reference measurement curve 13.

[0051] Fig. 4 Figure 1 shows another schematic diagram, in particular of a large number of different reference measurement curves 13. Specifically, it shows that a large number of different decay times 16 are recorded for the reference measurement curve 13. Furthermore, a large number of ground reflection ranges 17 can be determined.

[0052] In particular, the Fig. 4 Monitoring of the subfloor area 12 is only carried out in a very limited signal range, as typically only 20 cm are available between the ultrasonic sensor 4, 5, 6, 7 and the ground surface 11. This range is further limited by the decay time 16 and the ground reflection range 17. While the decay time 16 normally contains little information about an object, with the exception of when an object touches the ultrasonic sensor 4, 5, 6, 7 or is only a few centimeters away from it, the ground reflection range 17 may also contain reflections from the object. Since ground reflections 19 can have a significantly higher reflection amplitude than vulnerable objects, a corresponding method is proposed.To integrate the object information from the decay time 16, but especially from the ground reflection 19, into the object detection, a weighting 24 of the sample values ​​15 across the entire evaluation range is suitable. The evaluation range is defined in particular by the decay time 16, the measurement range 18, and the ground reflection range 17. The influence of each range on object detection is taken into account.

[0053] As previously described, the decay time 16 typically contains very little information about an object. However, the majority of this information is found in the region between the decay time 16 and the ground reflection 19, while the ground reflection 19 itself contains significantly less. Depending on the object's location, the object information can be distributed differently. Therefore, an adaptive weighting 24 is proposed. For this purpose, the decay time 16 and the ground reflection 19 are measured during the generation of the reference measurement curve 13. In addition to the amplitude and position, the fluctuations of the corresponding peaks with their widths during the calibration period are also of interest. When examining the subsurface area 12, the decay time 16, as well as the height of the ground reflection 19, can again be investigated.Depending on the value of the features, a non-linear weighting 24 of the sampling points 15 can be applied, thus significantly increasing both the sensitivity and robustness of the objects. The adaptive weighting 24 of the sample values ​​15 in the evaluation of the corresponding measurement signals for underbody monitoring is advantageous for enabling reliable object detection in the first place. The challenges in object detection include the varying distances of the objects from the ground surface 11, as well as the different reflective properties of the objects. With the help of adaptive weighting 24, these effects can be better accommodated, thereby significantly improving object detection.

[0054] The Fig. 4 Figure 1 shows, in particular, a family of curves for the reference measurement curves 13. Additionally, the weighting 24 of the sampled values ​​15 is applied. This weighting 24 was determined as a function of the corresponding family of curves. It is clearly shown that the measurement range 18 is most crucial for object detection in the subsoil area 12 and lies precisely between the decay time 16 and the ground reflection 19. Furthermore, it can be provided that the decay time 16 is weighted significantly less than the ground reflection 19, which at least partially contributes a higher weight to the evaluation. In particular, the weighting 24 in measurement range 18 is thus significantly higher than in the decay time 16 and the ground reflection range 17.

[0055] In particular, it can be provided that the weighting 24 is adapted to the relevant conditions during the generation of the reference measurement curve 13 and thus represents a function precisely tailored to the respective environmental scenario. With the adaptive weighting 24, object recognition can therefore be improved overall, among other things by the fact that the evaluation adapts much better to the conditions.

[0056] The Fig. 4This shows, in particular, that a measurement range 18 is determined in the comparison measurement curve 14, whereby the weighting 24 for the sample values ​​15 in the measurement range 18 is increased compared to the sample values ​​15 outside the measurement range 18. Specifically, the ground reflection range 17 and the settling time 16 of the ultrasonic sensor 4, 5, 6, 7 can be determined in the reference measurement curve 13, whereby the weighting 24 for the sample values ​​15 in the ground reflection range 17 is increased compared to sample values ​​15 within the settling time 16. For monitoring the subsoil area 12, a non-linear weighting 24 can be applied over the settling time 16, the measurement range 18, and the ground reflection range 17, as represented by the weighting 24.

[0057] The invention also relates to a computer program product not shown and a computer-readable storage medium not shown.

Claims

1. Method for operating an ultrasonic sensor device (2) for monitoring an underbody region (12) of a motor vehicle (1) by means of the ultrasonic sensor device (2) of the motor vehicle (1), in which method ultrasonic signals (U) are emitted into the underbody region (12) by means of at least one ultrasonic sensor (4, 5, 6, 7) of the ultrasonic sensor device (2), and the reflected ultrasonic signals (U) are received and evaluated by means of the ultrasonic sensor (4, 5, 6, 7), wherein, after the motor vehicle (1) has been parked at a first point in time (t1), a reference measurement curve (13) for the underbody region (12) is generated as a function of at least one ultrasonic signal (U) and stored, wherein a measurement region (18) is determined in the reference measurement curve (13), in which region the process of monitoring the underbody region (12) is evaluated, wherein the measurement region (18) is determined on the basis of a decay time (16) of the ultrasonic sensor (4, 5, 6, 7) and a ground reflection (19) on the ground surface (11), wherein, after a restart of the motor vehicle (1), at a second point in time (t2) later than the first point in time (t1), a comparison measurement curve (14) is generated as a function of at least one further ultrasonic signal (U) and the reference measurement curve (13) is compared with the comparison measurement curve (14) in the measurement region (18) and, based on the comparison, the underbody region (12) is monitored by means of an electronic computing device (3) of the ultrasonic sensor device, characterized in that, based on the comparison, a change in height (Δh) between an underbody (10) of the motor vehicle (1) and a ground surface (11) in the underbody region (12) is determined, and the change in height (Δh) is taken into account in the evaluation and monitoring, wherein the change in height (Δh) between the first point in time (t1) and the second point in time (t2) is determined.

2. Method according to Claim 1, characterized in that in the reflected ultrasonic signal (U) of the reference measurement curve (13), a ground reflection (19) of the ground surface (11) is determined and a first height (h1) relative to the ground surface (11) is determined on the basis of the determined ground reflection (19) at the first point in time (t1), and in the further reflected ultrasonic signal (U) of the comparison measurement curve (14), a ground reflection (19) of the ground surface (11) is determined and a second height (h2) relative to the ground surface (11) is determined on the basis of the determined ground reflection (19) at the second point in time (t2), and the change in height (Δh) is determined by comparing the first height (h1) and the second height (h2) .

3. Method according to Claim 1 or 2, characterized in that a decay time (16) of the ultrasonic sensor (4, 5, 6, 7) is taken into account when determining the change in height (Δh).

4. Method according to one of Claims 1 to 3, characterized in that at least one first environmental condition is detected when generating the reference measurement curve (13) and at least one second environmental condition is detected when generating the comparison measurement curve (14) and the first environmental condition and the second environmental condition are taken into account when determining the change in height (Δh).

5. Method according to one of the preceding claims, characterized in that the ultrasonic signal (U) is emitted by the at least one ultrasonic sensor (4, 5, 6, 7) in a region behind a wheel (8, 9) of the motor vehicle (1).

6. Method according to one of the preceding claims, characterized in that the ultrasonic sensor device (2) has a plurality of ultrasonic sensors (4, 5, 6, 7) on the motor vehicle (1), wherein the underbody region (12) of the motor vehicle (1) is monitored by means of the plurality of ultrasonic sensors (4, 5, 6, 7).

7. Method according to Claim 6, characterized in that a respective reference measurement curve (13) and / or a respective comparison measurement curve (14) of an ultrasonic sensor (4, 5, 6, 7) of the plurality of ultrasonic sensors (4, 5, 6, 7) is compared with at least one respective reference measurement curve (13) and / or a respective comparison measurement curve (14) of a further ultrasonic sensor (4, 5, 6, 7) of the plurality of ultrasonic sensors (4, 5, 6, 7) and verified.

8. Method according to one of the preceding claims, characterized in that objects in the measurement region that have been driven over during the generation of the reference measurement curve (13) are taken into account during monitoring.

9. Method according to one of the preceding claims, characterized in that a weighting (24) for samples (15) in the measurement region (18) is increased compared to samples (15) outside the measurement region (18).

10. Method according to one of the preceding claims, characterized in that a ground reflection region (17) and a decay time (16) of the ultrasonic sensor (4, 5, 6, 7) are determined in the reference measurement curve (13), wherein a weighting (24) for samples (15) in the ground reflection region (16) is increased compared to samples (15) within the decay time (16).

11. Method according to Claims 9 and 10, characterized in that to monitor the underbody region (12), a non-linear weighting (24) is carried out over the decay time (16), the measurement region (18) and the ground reflection region (17).

12. Computer program product having program code means that are stored in a computer-readable storage medium in order to carry out the method according to one of the preceding Claims 1 to 11 on an ultrasonic device according to Claim 14 when the computer program product is executed on a processor of an electronic computing device (3) of the ultrasonic device.

13. Computer-readable storage medium having a computer program product according to Claim 12.

14. Ultrasonic sensor device (2) for monitoring an underbody region (12) of a motor vehicle (1), having at least one ultrasonic sensor (4, 5, 6, 7) and having an electronic computing device (3), the ultrasonic sensor device (2) being designed to carry out a method according to one of Claims 1 to 11.