Method for operating an ultrasonic sensor device with an evaluation of a first ultrasonic signal and a second ultrasonic signal, as well as an ultrasonic sensor device

Abstract

Method for operating an ultrasonic sensor device (2) for a motor vehicle (1), in which an ultrasonic signal (10) is emitted into a ground area (6) below the motor vehicle (1) and an ultrasonic signal (10) is received from the ground area (6) and, depending on the emitted and / or the received ultrasonic signal (10), an object (7) in the ground area (6) is detected by means of an electronic computing device (11) of the ultrasonic sensor device (2), characterized in thatthat a first ultrasound signal (12) is emitted and received by means of a first ultrasound sensor (8) of the ultrasound sensor device (2) at a first time (t1) in the ground area (6) and a second ultrasound signal (13) is emitted and received by means of the first ultrasound sensor (8) at a second time (t2) different from the first time (t1) and the first received ultrasound signal (12) is compared with the second received ultrasound signal (13) as a comparison curve (V) by means of the electronic computing device (11) and the object (7) is detected depending on the comparison, wherein the first reference curve (R1) is evaluated by means of the electronic computing device (11) in such a way thatthat, depending on the received first amplitudes (A1) of the first received ultrasound signal (12), a first threshold range (S') with an upper threshold limit (G1) and a lower threshold limit (G2) for the first received ultrasound signal (12) is generated, and the object (7) is detected when a predetermined first number of received echo amplitudes (A3) of the comparison curve (V) are detected outside the first threshold range (S').

Description

[0001] The invention relates to a method for operating an ultrasonic sensor device for a motor vehicle. In this method, an ultrasonic signal is emitted into a ground area beneath the motor vehicle, and an ultrasonic signal is received from this ground area. Depending on the emitted and / or received ultrasonic signal, an object in the ground area is detected by means of an electronic processing unit of the ultrasonic sensor device. The invention further relates to an ultrasonic sensor device.

[0002] The focus here is on ultrasonic sensor devices for motor vehicles. Ultrasonic sensor devices comprising multiple ultrasonic sensors are known from the prior art. Such ultrasonic sensors can be used to monitor the area surrounding the motor vehicle. In particular, the ultrasonic sensors can be used to determine the distance between the motor vehicle and objects in the surrounding area. Such an ultrasonic sensor device can, for example, be part of a driver assistance system that supports the driver when parking in and / or exiting a parking space.

[0003] The invention takes advantage of the fact that objects beneath the vehicle can also be detected using the ultrasonic sensor device. Particularly in at least partially autonomous, and especially in fully autonomous, driving mode, monitoring the underbody can, for example, prevent the vehicle from being affected by the object when it starts moving, or vice versa.

[0004] Ultrasonic sensor devices for monitoring the ground beneath a motor vehicle are already known in the prior art. For example, DE 10 2013 001 119 A1 discloses a driver assistance system for assisting a driver when parking and / or maneuvering a vehicle, wherein the driver assistance system comprises at least one sensor device for detecting the area surrounding the motor vehicle and a control unit for evaluating the signals from the sensor device. The signals can be used, for example, to determine the distance between the ground and the underside of the vehicle. The sensor device and the control unit are configured such that the detection range of the sensor device includes at least a definable area of ​​the ground beneath the motor vehicle. The sensor device can include at least one ultrasonic sensor.

[0005] From publication JP H11-321497 A, a safety device for vehicles is known which also serves to detect obstacles under the vehicle before starting, in which, after the vehicle has been parked, the envelope of a received ultrasonic signal is stored as a reference waveform and, for obstacle detection, a current waveform is compared with the stored reference, whereby an obstacle is detected when there is a formal change in the waveform geometry.

[0006] Furthermore, German patent application DE 10 2005 059 907 A1 discloses a method and an ultrasonic sensor in which the sensor's sensitivity characteristic can be dynamically configured for a measurement. This is achieved by a time-varying threshold curve defined by a series of so-called support points, the temporal position of which can be changed by a control signal in order to, for example, switch the sensor's range or to suppress known interference echoes, such as ground echoes, by selectively raising the threshold in the corresponding time range.

[0007] The object of the present invention is to provide a method and an ultrasonic sensor device by means of which a ground area below the motor vehicle can be monitored more reliably.

[0008] This problem is solved by a method and by an ultrasonic sensor device according to the independent patent claims.

[0009] One aspect of the invention relates to a method for operating an ultrasonic sensor device for a motor vehicle, in which an ultrasonic signal is emitted in a ground area beneath the motor vehicle. An ultrasonic signal is received from the ground area, and depending on the emitted and / or received ultrasonic signal, an object in the ground area is detected by means of an electronic computing unit of the ultrasonic sensor device.

[0010] The system is designed so that a first ultrasonic signal is transmitted and received in the ground area at a first time point by means of a first ultrasonic sensor of the ultrasonic sensor device, and a second ultrasonic signal is transmitted and received by the first ultrasonic sensor at a second time point different from the first. The first received ultrasonic signal is then compared with the second received ultrasonic signal as a comparison curve by means of the electronic processing unit. The object is detected based on the comparison.By means of the electronic computing device, the first reference curve is evaluated in such a way that, depending on the received first amplitudes of the first received ultrasound signal, a first threshold range with an upper threshold limit and a lower threshold limit for the first received ultrasound signal is generated, and the object is detected when a predetermined first number of received echo amplitudes of the comparison curve are detected outside the first threshold range.

[0011] This allows the reference curve at the first time point to be used as a reference for the absence of the object beneath the vehicle. In particular, since the vehicle, for example, moved into a parking space during the first time point in such a way that the ground area was clear, this can be considered a reference for the absence of the object. To compare whether the situation beneath the ground area has changed at the second time point, a second ultrasonic signal is emitted by the first ultrasonic sensor, and the received second ultrasonic signal is compared with the reference curve. If a change has occurred, it can be assumed that an object is located beneath the vehicle, specifically within the ground area.This enables reliable object detection, particularly improving monitoring of the ground area. This, in turn, prevents the vehicle from being affected by the object, or vice versa. Specifically, it allows for the provision of a driver assistance system that reliably monitors the vehicle's position on the ground.

[0012] In the present case, "number" refers in particular to at least one amplitude, preferably a multitude of amplitudes, where "much" in particular means more than one amplitude.

[0013] In particular, it is intended that the object is defined by a multitude of echoes within the ultrasound signal. In other words, a multitude of echoes can be captured as echo amplitudes within the ultrasound signal, which then, in turn, describe the object. Especially since the object has a corresponding geometric extent, multiple echoes are captured, for example, at different distances from the ultrasound sensor, and evaluated accordingly. In other words, it is intended that a multitude of different echoes are captured within the comparison curve, which can be assigned to the object in order to identify it. In other words, it is preferably intended that the object is only recognized when the comparison curve deviates at several points / amplitudes, particularly at several times or distances, within the comparison curve.In particular, this embodiment leads to misinterpretations when comparing the first ultrasound signal with the second ultrasound signal.

[0014] It may preferably be provided that the method can also detect a large number of objects, in particular more than one object, within the ground area.

[0015] The underbody is defined as the area directly beneath the vehicle. Specifically, the underbody can be defined, for example, by the vehicle's external shape and / or the positioning of its tires.

[0016] It is preferable that, depending on the comparison, a corresponding warning signal can be issued, for example, to a driver. If, for instance, it is detected that an object is located under the vehicle's underbody, a driver assistance system can issue a corresponding warning signal, which is made available to the driver of the vehicle before driving. In particular, this can inform the driver of the presence of the object under the vehicle.

[0017] For example, if the vehicle is operating in at least partially autonomous, and especially fully autonomous, mode, the driver assistance system can preferably be configured to generate a stop signal if an object is detected below the vehicle, thus preventing the partially autonomous, and especially the fully autonomous, vehicle from starting to move. This increases the safety of both the vehicle and the object.

[0018] For example, an object could be a stone or branch that, due to environmental conditions, was positioned under the vehicle while it was stationary. Furthermore, an animal located under the vehicle at the second point in time could also be considered an object.

[0019] Preferably, it may be provided that there is a longer period of time between the first time and the second time, for example at least two minutes.

[0020] The first point in time is defined in particular by the moment the vehicle is parked after being driven. The second point in time is defined in particular by the moment the vehicle is put back into operation after it has been parked.

[0021] Furthermore, it is preferable that the ultrasonic sensor is arranged on the vehicle in such a way that an area in front of or behind at least one tire of the vehicle can be monitored. This has the particular advantage that, since the object could be driven over by the at least one tire, potentially damaging it, precisely this critical area can be monitored. Thus, the critical part by which the vehicle would drive over the object can be reliably observed.

[0022] In particular, the raw data is used to detect the object. In other words, the reference curve is generated using the raw data from the first ultrasonic sensor. This reference curve consists of a specific number of values ​​that describe the signal amplitudes over the specified transit time of the ultrasonic sensor. For example, if the ultrasonic sensor is designed to monitor a distance of 0 to 1 meter, the number of values ​​is prescribed accordingly. Specifically, the values ​​at predefined discrete time intervals or distance intervals are then receivable as echo signals. The received echo signal then exhibits a multitude of different corresponding echo values ​​with varying amplitudes at the different times or distances.These different amplitudes at the different times are then taken as the raw data curve, reference curve, and comparison curve, respectively.

[0023] The second ultrasound signal behaves similarly. The comparison curve is recorded, just like the reference curve. However, if an object is located beneath the vehicle, the values ​​in the distance range of the object change. Specifically, the amplitudes in the area of ​​the object change, which can then be detected through comparison. By generating a threshold range, it can be reliably determined that an object is located beneath the vehicle if the amplitudes in the comparison curve fall outside this threshold range.

[0024] Preferably, it can be provided that a minimum number of echoes, for example at least two, at least five, at least ten, at least 50, at least 100, or at least 150, must be received to detect the object, and these echoes must lie outside the threshold range. In particular, this prevents a corresponding detection signal for an object from being issued upon the detection of a single outlier, even though no object is present in the vicinity, especially in the underbody area of ​​the vehicle. This, in particular, prevents false object detection.

[0025] According to an advantageous embodiment, the first reference curve is generated by emitting the first ultrasound signal for a predetermined initial period, and the first threshold range is generated by evaluating the received ultrasound signal over the same predetermined initial period. In other words, not only is an ultrasound signal emitted into the environment, but the first ultrasound signal is emitted for a predetermined period, for example, one second, two seconds, or five seconds, whereby the reference curve is then generated over the specified period by a multitude of amplitudes during several ultrasound measurements.In particular, the threshold limits, both the upper and lower limits, can then be determined within each period, thereby defining the threshold range for the first ultrasound signal during that period. For example, the maximum amplitudes during the entire first period are set as the upper threshold, and the minimum amplitudes during the entire first period as the lower threshold. If the amplitude of the second ultrasound signal then falls outside this threshold range above the predetermined first period, the object can be detected. This has the particular advantage that the subsoil can be reliably monitored over a longer period by providing the threshold range.

[0026] It has also proven advantageous to generate the first reference curve as a hysteresis window using the electronic processing unit. In other words, the reference curve is not derived directly from the raw data of the first ultrasound signal, but rather a hysteresis window is created from the data of the first ultrasound signal, which can then be used to generate the reference curve. This has the advantage of allowing for improved evaluation of the first ultrasound signal for generating the reference curve, whereby, by utilizing the hysteresis window, the upper and lower thresholds can be appropriately considered. This enables improved operation of the ultrasound sensor device and improved detection of the object below the vehicle's underbody.

[0027] It is also advantageous to generate the hysteresis window by averaging the received initial amplitudes of the first ultrasonic signal. In other words, an average can be calculated from the respective lower and upper threshold values ​​of the first ultrasonic signal, which is then used to generate the reference curve. This allows the threshold range to be reliably determined using the reference curve, resulting in improved operation of the ultrasonic sensor device and, consequently, improved object detection within the ground area.

[0028] For example, the hysteresis window (HF) can be calculated using the formula: HR=±(Meanref+Maxref−Minref2) be determined, whereby Mean ref corresponds to the mean and max refthe upper threshold limit and min ref correspond to the lower threshold limit.

[0029] In a further advantageous embodiment, the second ultrasound signal is emitted for a predetermined second period, and the object is detected by comparing the received amplitudes over this period with the first reference curve. In other words, the second ultrasound signal is also emitted for a predetermined period, for example, one second, two seconds, three seconds, or five seconds. In particular, the second ultrasound signal is then evaluated multiple times, specifically by multiple ultrasound measurements, over this predetermined period. Specifically, it can be provided that if a detected amplitude lies outside the threshold range, it must repeatedly fall outside the threshold range over the predetermined period to be considered a significant indicator of the object's presence.In other words, the second period determines whether the echo repeatedly falls outside the threshold range at a predetermined interval. Only if this occurs a predetermined number of times outside the threshold range is the echo recognized as an object. This reliably prevents the misinterpretation of a non-existent object.

[0030] It has also proven advantageous if the first and second ultrasonic signals are additionally received by at least one second ultrasonic sensor of the ultrasonic sensor device, and a second reference curve with a second threshold range is generated depending on the second amplitudes of the first ultrasonic signal received by the second ultrasonic sensor. This second reference curve is then compared with the second amplitudes of the second ultrasonic signal received by the second ultrasonic sensor as a second comparison curve. The object is detected when a predetermined second number of received second amplitudes of the second comparison curve are detected outside the second threshold range. In other words, a direct measurement can be performed with the first ultrasonic sensor, and an indirect measurement can be performed with the second ultrasonic sensor.The second ultrasonic sensor is therefore specifically designed to receive the first and second ultrasonic signals from the first ultrasonic sensor. In other words, the second ultrasonic sensor does not emit an ultrasonic signal, but merely receives the ultrasonic signals from the first ultrasonic sensor. This allows for the detection of whether the object detected by the direct measurement is actually located beneath the vehicle or merely beside it. The indirect measurement using the second ultrasonic sensor thus prevents an object from being classified as critical or present if it is not actually beneath the vehicle, but rather beside it, despite being detected by the direct measurement.This prevents, for example, a stop signal from being generated for the vehicle even though the object is not underneath it, but merely positioned parallel to it. This allows for reliable object detection, determining whether the object is underneath the vehicle and therefore potentially affecting its operation. Furthermore, the measurement result from the first ultrasonic sensor can be compared with the measurement from the second ultrasonic sensor. For instance, the object can only be identified if both ultrasonic sensors, or the evaluation of both comparisons, indicate that the object is underneath the vehicle. This results in improved operation of the ultrasonic sensor device and enhanced monitoring of the vehicle's undercarriage.

[0031] According to a further advantageous embodiment, the object is detected when the first number of echoes received by the first ultrasonic sensor is equal to or greater than the second number of echoes received by the second ultrasonic sensor. In particular, as already described, a plurality of echo amplitudes is assigned to the object. Since the transit time of the ultrasonic signal to the first ultrasonic sensor is shorter than to the second, it is therefore crucial that the number of echoes received by the first ultrasonic sensor is at least equal to, and preferably greater than, the second number of echoes received by the second ultrasonic sensor. This allows, in particular, validation of whether the object is actually located within the underbody area. This enables improved monitoring of the vehicle's underbody.

[0032] Furthermore, it has proven advantageous if the object is detected when both the first and second ultrasonic sensors have detected it by comparison. In other words, the electronic processing unit evaluates whether the object was detected by the first and second ultrasonic sensors. Only when both the first and second ultrasonic sensors, and specifically only when the evaluation of the corresponding received signal from the first and second ultrasonic sensors indicates that an object is located below the vehicle's underbody, is the system output indicating the presence of the object.This prevents, for example, a faulty evaluation by the first and / or second ultrasonic sensor from leading to a misinterpretation of the object's presence. Thus, the evaluations from the first and second ultrasonic sensors can be validated against each other. This results in improved and more reliable operation of the ultrasonic sensor device and, consequently, improved detection of objects below the vehicle's underbody.

[0033] Furthermore, it has proven advantageous to emit the first ultrasound signal when the vehicle comes to a standstill, particularly when parked. In other words, the first time point is chosen to be when the vehicle is stationary. Specifically, the first ultrasound signal is emitted after the vehicle is parked. Since the underbody is already monitored by a user before the vehicle comes to a standstill, it is crucial that the underbody is monitored during the standstill period, when, for example, no user monitoring is taking place. Specifically, the first ultrasound signal is evaluated when the vehicle is parked or stationary, and it can then be planned, for example, that the underbody is monitored again for this period of inactivity before the vehicle is driven again.This allows the ground area to be monitored, particularly while the vehicle is stationary, in preparation for the next driving operation.

[0034] Furthermore, it has proven advantageous to emit the first ultrasound signal when the vehicle is locked by a user. In other words, the system is designed so that the first ultrasound signal is emitted and ground monitoring begins only after the user has left the vehicle and it is locked. This is particularly important because, for example, the vehicle's height or load changes when it is vacated or unloaded. Specifically, the load can also alter the distance to the ground. Therefore, if the first ultrasound signal were emitted simply because the vehicle was loaded or the user was present, the comparison would be inaccurate.This would lead to a misinterpretation of the object's presence. Therefore, it is planned that underbody monitoring will only be carried out once the user has locked the vehicle, which then implies that the vehicle will remain in this state for at least a certain period of time. This allows for a reliable comparison when monitoring the underbody area.

[0035] In a further advantageous embodiment, the second ultrasonic signal is emitted when the vehicle is started by a user. In particular, it can also be provided that the second ultrasonic signal is emitted as soon as the user unlocks the vehicle. Thus, the corresponding comparison curve can be reliably generated even before the journey begins. This enables reliable monitoring of the underbody area. Specifically, monitoring can be carried out before the journey begins and thus before any potential hazard to the vehicle by the object or vice versa. Furthermore, changes in the vehicle's load after unlocking but before the journey begins have no negative impact on the monitoring. This leads to improved operation of the ultrasonic sensor device and improved monitoring of the underbody area of ​​the vehicle.

[0036] Another aspect of the invention relates to an electronic computing device with a computer program product, wherein the electronic computing device is configured to carry out the method according to the preceding aspect. In particular, the method is carried out using the electronic computing device. The computer program product especially comprises program code means which can be stored on a computer-readable medium and executed using the electronic computing device.

[0037] A further aspect of the invention relates to an ultrasonic sensor device for a motor vehicle, comprising at least one first ultrasonic sensor and an electronic computing device according to the preceding aspect, wherein the ultrasonic sensor device is configured to carry out the method according to a previously mentioned aspect. In particular, the method is carried out using the ultrasonic sensor device. The ultrasonic sensor device is specifically configured to monitor the underbody of the motor vehicle.

[0038] An advantageous embodiment of the ultrasonic sensor device comprises at least the first ultrasonic sensor for transmitting and receiving ultrasonic signals and a second ultrasonic sensor, which is designed at least for receiving ultrasonic signals.

[0039] A further aspect of the invention relates to a motor vehicle with an ultrasonic sensor device according to the preceding aspect. The motor vehicle is specifically designed as a passenger car.

[0040] Advantageous embodiments of the method are to be regarded as advantageous embodiments of the ultrasonic sensor device and the motor vehicle. For this purpose, the ultrasonic sensor device and / or the motor vehicle possess material features that are necessary for carrying out the method or an advantageous embodiment thereof.

[0041] 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 or on their own, without departing from the scope of the invention. Thus, embodiments of the invention are also to be considered as encompassed and disclosed 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. Embodiments and combinations of features are also to be considered disclosed that do not exhibit all the features of an originally formulated independent claim.

[0042] The invention will now be explained in more detail with reference to preferred embodiments and the accompanying drawings.

[0043] This shows: Fig. 1 a schematic top view of a motor vehicle with an embodiment of an ultrasonic sensor device; Fig. 2 a schematic side view of the motor vehicle with an embodiment of an ultrasonic sensor device according to Fig. 1; Fig. 3 a schematic view of an embodiment of a reference curve; Fig. 4 another schematic view of a reference curve; and Fig. 5 a schematic flowchart of an embodiment of the method.

[0044] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0045] Fig. Figure 1 shows a schematic top view of a motor vehicle 1 with an embodiment of an ultrasonic sensor device 2. In the present embodiment, the motor vehicle 1 is shown in particular from an underside 3 of the motor vehicle 1.

[0046] In the present embodiment, the motor vehicle 1 further comprises a driver assistance system 4, wherein the ultrasonic sensor device 2 can be part of the driver assistance system 4. The motor vehicle 1 also has four tires 5 in the present embodiment.

[0047] The ultrasonic sensor device 2 can be used to monitor a ground area 6 beneath the motor vehicle 1. In particular, the ultrasonic sensor device 2 can be used to check whether an object 7 ( Fig. 2) is located in floor area 6.

[0048] In the present embodiment, the ultrasonic sensor device 2 comprises a plurality of ultrasonic sensors 8, 9. In particular, the ultrasonic sensor device 2 has at least one first ultrasonic sensor 8. In the present embodiment, the ultrasonic sensor device 2 has at least one first ultrasonic sensor 8 and one second ultrasonic sensor 9. In the present embodiment, the ultrasonic sensor device 2 has six first ultrasonic sensors 8 and six second ultrasonic sensors 9, whereby, in particular, the entire underbody area 6 of the motor vehicle 1 can be monitored by means of this embodiment.

[0049] One aspect of the invention relates to a method for operating the ultrasonic sensor device 2 for the motor vehicle 1. In the method, an ultrasonic signal 10 ( Fig. 2) emitted into the ground area 6 below the motor vehicle 1 and an ultrasonic signal 10 is received from the ground area 6 and, depending on the emitted and / or the received ultrasonic signal 10, the object 7 in the ground area 6 is detected by means of an electronic computing device 11 of the ultrasonic sensor device 2.

[0050] It is planned that a first ultrasound signal will be received 12 ( Fig. 3) using the first ultrasonic sensor 8 of the ultrasonic sensor device 2 at a first time t1 ( Fig. 3) is emitted and received in the ground area 6 and a second ultrasound signal 13 ( Fig. 4) using the first ultrasonic sensor 8 at a second time t2 different from the first time t1 ( Fig. 4) is transmitted and received, and the first received ultrasound signal 12 serves as the reference curve R1, R2 with the second received ultrasound signal 13 as the comparison curve V ( Fig. 3) are compared with each other using the electronic computing device 11, and the object 7 is recognized depending on the comparison. The reference curve R1, R2 is evaluated by the electronic computing device 11 in such a way that, depending on the received amplitudes A1, A2 ( Fig. 3) of the first ultrasound signal 12 a threshold range S', S'' with an upper threshold limit G1 and with a lower threshold limit G2 is generated for the first ultrasound signal 12, and the object 7 is detected when a predetermined first number of received amplitudes A1, A2 of the comparison curve V is detected outside the threshold range S', S''.

[0051] This allows the reference curve R1, R2 at the first time t1 to be used as a reference for the absence of object 7 beneath vehicle 1. In particular, since vehicle 1, for example, moved into a parking space during the first time t1 in such a way that the ground area 6 was clear, this can be considered a reference for the absence of object 7. To compare whether the situation beneath the ground area 6 has changed at the second time t2, a second ultrasonic signal 13 is emitted by the first ultrasonic sensor 8, and the received second ultrasonic signal 13 is compared with the reference curve R1, R2. If a change has occurred, it can be assumed that object 7 is located beneath vehicle 1, specifically within the ground area 6.This enables reliable detection of object 7, which in turn allows for improved monitoring of the ground area 6. This, in particular, prevents the vehicle 1 from being affected by object 7, or vice versa. Specifically, this enables the provision of a driver assistance system 4, which allows for reliable ground monitoring of the vehicle 1.

[0052] In the present case, "number" means in particular at least one amplitude A1, A2, preferably a plurality of amplitudes A1, A2, where "plurality" in particular means more than one amplitude A1, A2.

[0053] In particular, it is provided that object 7 is defined by a multitude of echoes within the ultrasound signal 10. In other words, a multitude of echoes can be detected as echo amplitudes in the ultrasound signal 10, which then in turn describe object 7. Especially since object 7 has a corresponding geometric extent, several echoes are detected, for example at different distances from the ultrasound sensor 8, 9, and evaluated accordingly. In other words, it is provided that a multitude of different echoes are detected within the comparison curve V, which can be assigned to object 7 in order to identify object 7. In other words, it is preferably provided that object 7 is only detected when the comparison curve V deviates at several points / amplitudes, especially at several times or distances, within the comparison curve V.In particular, this embodiment leads to misinterpretations within the comparison of the first ultrasound signal 12 with the second ultrasound signal 13.

[0054] Preferably, it may be provided that the method can also detect a large number of objects 7, in particular more than one object 7, within the ground area 6.

[0055] Ground area 6 is defined in particular as the area located directly beneath the motor vehicle 1. Specifically, ground area 6 can be defined, for example, by the external shape of the motor vehicle 1 and / or by the positioning of the tires 5 of the motor vehicle 1.

[0056] Preferably, it can be provided that, depending on the comparison, a corresponding warning signal can be issued, for example, to a driver. If, for example, it is detected that an object 7 is located beneath the vehicle floor, a driver assistance system 4 can issue a corresponding warning signal, which is made available to the driver of the vehicle 1 before the vehicle 1 is driven. In particular, this can inform the driver of the presence of the object 7 beneath the vehicle 7.

[0057] For example, if the vehicle 1 is operating in at least partially autonomous, and in particular fully autonomous, mode, the driver assistance system 4 can preferably be configured to generate a stop signal if an object 7 is detected below the vehicle 1, thus preventing the at least partially autonomous, and in particular the fully autonomous, vehicle 1 from starting to move. This increases the safety of both the vehicle 1 and the object 7.

[0058] For example, object 7 could be a stone or branch that, for instance, was positioned beneath vehicle 1 due to environmental conditions while the vehicle 1 was stationary. Furthermore, object 7 could be an animal that was located beneath vehicle 1 at the second time point t2.

[0059] Preferably, it can be provided that there is a longer period of time, for example at least two minutes, between the first time t1 and the second time t2.

[0060] The first time point t1 is defined in particular by the parking of motor vehicle 1 after driving. The second time point t2 is defined in particular by the start of operation of motor vehicle 1 after it has been parked.

[0061] Furthermore, it is preferable that the first and / or the second ultrasonic sensor 8, 9 is arranged on the motor vehicle 1 in such a way that an area in front of or behind at least one tire 5 of the motor vehicle 1 can be monitored. This has the particular advantage that, since the object 7 could be driven over by the at least one tire 1, thereby potentially damaging it, precisely this critical area can be monitored. Thus, the critical part by which the motor vehicle 1 would drive over the object 7 can be reliably observed.

[0062] In particular, the raw data is used to detect object 7. In other words, the reference curve R1, R2 is generated using the raw data from the first ultrasonic sensor 8. This curve consists of a specific number of values ​​that describe the amplitudes A1, A2 of the signal over the specified transit time of the ultrasonic sensor 8, 9. For example, if the ultrasonic sensor 8, 9 is designed to monitor a distance of 0 to 1 meter, the number of values ​​is prescribed accordingly. Specifically, the values ​​can then be received as echo signals at specified discrete time intervals or distance intervals. The received echo signal then exhibits a multitude of different corresponding echo values ​​with different amplitudes A1, A2 at the different times t1, t2 or distances.These different amplitudes A1, A2 at the different times t1, t2 are then taken as the raw data curve or reference curve R1, R2 and comparison curve V.

[0063] The second ultrasound signal 13 behaves similarly. The comparison curve V is recorded, just like the reference curves R1, R2. However, if an object 7 is located below the vehicle 1, the values ​​in the distance range of object 7 change. Specifically, the amplitudes A1, A2 in the area of ​​object 7 change, which can then be detected by comparison. In particular, by generating the threshold range S', S'', it can be reliably determined that if the amplitudes A1, A2 in the comparison curve V are outside this threshold range S', S'', then an object 7 is located below the vehicle floor.

[0064] Preferably, it can be provided that a minimum number of echoes, for example at least two, at least five, at least ten, at least 50, at least 100, or at least 150, must be received to detect object 7, and these echoes must lie outside the threshold range S', S''. In particular, this prevents a corresponding detection signal for object 7 from being issued upon detection of a single outlier, even though no object 7 is present in the vicinity, especially in the floor area 6 of the vehicle 1. This, in particular, prevents false detection of object 7.

[0065] As in the Fig. As shown in Figure 1, the ultrasonic sensor device 2 can have a different number of ultrasonic sensors 8, 9. Different configurations of the other ultrasonic sensors 8, 9 offer different advantages. For example, it may be possible to monitor only a section of the tires 5 using the ultrasonic sensors 8, 9. Since these tires can drive over the object 7, it is particularly advantageous to monitor the ground area 6 in the vicinity of the tires 5.

[0066] Fig. Figure 2 shows a schematic side view of an embodiment of the motor vehicle 1 with an embodiment of the ultrasonic sensor device 2. In the present embodiment, the ultrasonic sensor device 2 comprises the first ultrasonic sensor 8 and the second ultrasonic sensor 9. The first ultrasonic sensor 8 is designed, in particular, for directly detecting the object 7, and the second ultrasonic sensor 9 is designed for indirectly detecting the object 7. In particular, it is thus provided that the first ultrasonic signal 12 and the second ultrasonic signal 13 are additionally received by at least the second ultrasonic sensor 9 of the ultrasonic sensor device 2, and a second reference curve R2 ( Fig. 4) with a second threshold range S'' ( Fig. 4) depending on the amplitudes A2 of the first ultrasound signal 12 received by the second ultrasound sensor 9 and compared with the amplitudes A2 of the second ultrasound signal 13 received by the second ultrasound sensor 9 as a second comparison curve V and the object 7 is detected when a predetermined second number of received amplitudes A2 of the second comparison curve V are detected outside the second threshold range S''.

[0067] In other words, the first ultrasonic sensor 8 can perform a direct measurement, and the second ultrasonic sensor 9 can perform an indirect measurement. The second ultrasonic sensor 9 is therefore specifically designed only to receive the first ultrasonic signal 12 and the second ultrasonic signal 13 from the first ultrasonic sensor 8. In other words, the second ultrasonic sensor 9 does not emit an ultrasonic signal 10, but merely receives the ultrasonic signals 12 and 13 from the first ultrasonic sensor 8. This makes it possible, in particular, to detect whether the object 7 detected by the direct measurement is actually located beneath the vehicle 1 or merely next to it.The indirect measurement using the second ultrasonic sensor 9 prevents an object 7 from being classified as critical or present if it is not located beneath the vehicle 1, but rather next to it, even though it was detected by direct measurement. This prevents, for example, a stop signal from being generated for the vehicle 1 when the object 7 is not actually beneath it, but merely parallel to it. This allows for reliable detection of the object 7, determining whether it is located beneath the vehicle 1 and thus potentially affecting it.Furthermore, this allows the measurement result from the first ultrasonic sensor 8 to be compared with the measurement from the second ultrasonic sensor 9, and, for example, the object 7 can only be determined if both ultrasonic sensors 8 and 9, or if the evaluation of both comparisons shows that the object 7 is located below the vehicle 1. This enables improved operation of the ultrasonic sensor device 2 and improved monitoring of the underbody area 6 of the vehicle 1.

[0068] Fig. Figure 3 shows a schematic diagram of a received ultrasound signal 12 using the first ultrasound sensor 8. In particular, the Fig. 3 a direct measurement. In particular, it can be seen that a raw data curve is used as the first reference curve R1. This can also be done for the second reference curve R2 ( Fig. 4) can be used. The raw data curve has a specific number of values ​​that represent the amplitude A1, which in particular correspond to the received amplitudes A1 of the first ultrasonic sensor 8 in a direct measurement. In particular, the Fig. Figure 3 shows how a direct measurement is carried out using the first ultrasonic sensor 8. Furthermore, the figure shows that the first reference curve R1 is generated by emitting the first ultrasonic signal 12 over a predetermined first period t1, and a first threshold range S' is generated by evaluating the received ultrasonic signal 12 over the predetermined period t1 using the first ultrasonic sensor 8.

[0069] Fig. Figure 4 shows a schematic view of another diagram of an indirect ultrasound signal 12 received by the second ultrasound sensor 9. In particular, it shows Fig. 4, that based on the time difference, corresponding amplitudes A2 are only received later. Furthermore, the Fig. 4, the comparison curve V, which was generated at the second time t2 by the second ultrasound signal 13. In particular, the comparison curve V can lie outside the second threshold range S'' in this example, which allows conclusions to be drawn about object 7. This is shown in particular by the arrows with the reference symbol 7. The comparison of the first reference curve R1 can be analogous. Here, the evaluation or comparison with the second reference curve generated by the second ultrasound sensor 9 is shown purely as an example.

[0070] For example, it may be provided that a hysteresis window is generated using the electronic computing device 11 to create the reference curve R1, R2. In particular, the hysteresis window can be generated by averaging the received amplitudes A1, A2 of the ultrasound signal 12, 13.

[0071] For example, the hysteresis window (HF) can be calculated using the formula: HR=±(Meanref+Maxref−Minref2) be determined, whereby Mean ref corresponds to the mean and max ref the upper threshold limit G1 and Min ref correspond to the lower threshold limit G2.

[0072] Fig. Figure 4 shows in particular that the echo amplitude A3 of the second ultrasound signal 13 can, for example, lie within the second threshold range S'' or outside the threshold range S''. In particular, if the echo amplitude A3 of the second ultrasound signal 13 lies outside the second threshold range S'', it can thus be concluded that there is an object 7 in the floor area 6 of the motor vehicle 1.

[0073] In particular, the echo amplitudes A3 in the comparison curve V are to be detected to recognize the object 7 at an equal distance 15 to the first ultrasonic sensor 8 and / or at an equal transit time of the second ultrasonic signal 13.

[0074] Furthermore, it can be provided that the object 7 is detected if the first ultrasonic sensor 8 and the second ultrasonic sensor 9 each detect the object 7 by comparison. Fig. Figure 4 shows in particular the second reference curve R2 for the indirect detection of the object 7 using the second ultrasonic sensor 9. The same applies analogously to the first reference curve R1 of the first ultrasonic sensor 8.

[0075] Fig.Figure 5 shows a schematic flowchart of the method according to the invention. The figure shows in particular that the first ultrasound signal 12 is emitted when the motor vehicle 1 is brought to a standstill, specifically when it is parked, in step S1. In step S2, the first ultrasound signal 12 is emitted and the reference curves R1 and R2 are generated. The figure further shows that the first ultrasound signal 12 is emitted when the motor vehicle 1 is locked by a user, also in step S1. The figure further shows that the second ultrasound signal 13 is emitted when the motor vehicle 1 is started by a user, also in step S3, in step S3.

[0076] In step S1, it is checked whether vehicle 1 is parked. This is repeated accordingly if it is determined that vehicle 1 is not parked. In step S2, the first ultrasonic sensor 8 emits the ultrasonic signal 12, and the reference curves R1 and R2 are generated accordingly using the first ultrasonic sensor 8 and the second ultrasonic sensor 9. In step S2', the raw data of the ultrasonic signal 10, in particular the first ultrasonic signal 12, are provided. Specifically, the maximum and minimum amplitudes in the reference curves R1 and R2 are recorded as values ​​and evaluated, for example, using the hysteresis window.

[0077] In step S3, it is checked whether, for example, a key has been inserted. If a key is detected, the second ultrasound signal 13 is emitted in step S4. If no key is detected, step S3 is repeated. In step S4', the raw data of the amplitudes A1 and A2 are compared with the values ​​of the second ultrasound signal 13.

[0078] In step S5, the first ultrasound signal 12 is compared with the second ultrasound signal 13. If, for example, a value lies outside the threshold range S', S'', represented by step S6.1, a counter is incremented. In step S6.2, those amplitudes A1, A2 that are within the threshold range S', S'' are checked. In step S7, the measurement is terminated. Steps S5 and S6.1 or S6.2 can be repeated.

[0079] In step S8, it is checked whether the values ​​are within the specified threshold range S', S'' and whether it is sufficient to reliably detect that one of these values ​​is, in particular permanently, below the floor area 6.

[0080] In step S9.1, the detection probability is increased accordingly by one of the ultrasonic sensors 8, 9, and in step S9.2, the detection probability is decreased accordingly. The number of detected amplitudes A3 outside the threshold ranges S', S" is provided as input values ​​for this evaluation in step S9'.

[0081] In step S10, it is checked and evaluated whether object 7 is located below the ground area, specifically by verifying whether the number of detected values ​​is sufficient for object 7 detection. Then, in step S11.1, if object 7 has been detected below ground area 6, a stop signal is issued, for example, for the driver assistance system 3. Conversely, if no object 7 has been detected below ground area 6, no stop signal is issued in step S11.2; in other words, the vehicle 1 is not authorized to proceed.

[0082] Overall, the invention shows a method for protecting the underbody 6 of the motor vehicle 1 with the ultrasonic sensor device 2 before the motor vehicle 1 is started.

Claims

[1] Method for operating an ultrasonic sensor device (2) for a motor vehicle (1), in which an ultrasonic signal (10) is emitted into a ground area (6) below the motor vehicle (1) and an ultrasonic signal (10) is received from the ground area (6) and, depending on the emitted and / or the received ultrasonic signal (10), an object (7) in the ground area (6) is detected by means of an electronic computing device (11) of the ultrasonic sensor device (2), characterized by, that a first ultrasound signal (12) is emitted and received by means of a first ultrasound sensor (8) of the ultrasound sensor device (2) at a first time (t1) in the ground area (6) and a second ultrasound signal (13) is emitted and received by means of the first ultrasound sensor (8) at a second time (t2) different from the first time (t1) and the first received ultrasound signal (12) is compared with the second received ultrasound signal (13) as a comparison curve (V) by means of the electronic computing device (11) and the object (7) is detected depending on the comparison, wherein the first reference curve (R1) is evaluated by means of the electronic computing device (11) in such a way thatthat, depending on the received first amplitudes (A1) of the first received ultrasound signal (12), a first threshold range (S') with an upper threshold limit (G1) and a lower threshold limit (G2) for the first received ultrasound signal (12) is generated, and the object (7) is detected when a predetermined first number of received echo amplitudes (A3) of the comparison curve (V) is detected outside the first threshold range (S'). [2] Method according to claim 1, characterized by , that the first reference curve (R1) is generated by emitting the first ultrasound signal (12) over a predetermined first period (t1) and the first threshold range (S') is generated by evaluating the received ultrasound signal (12) over the predetermined first period (t1). [3] Method according to any one of the preceding claims, characterized by, that the first reference curve (R1) is generated as a hysteresis window by means of the electronic computing device (11). [4] Method according to claim 3, characterized by , that to generate the hysteresis window, an averaging of the received first amplitudes (A1) of the first ultrasound signal (12) is carried out. [5] Method according to any one of the preceding claims, characterized by , that the second ultrasound signal (13) is emitted over a predetermined second period (t2) and the object (7) is detected by comparing the received first amplitudes (A1) over the predetermined second period (t2) with the first reference curve (R1). [6] Method according to any one of the preceding claims, characterized by, that the echo amplitudes (A3) in the comparison curve (V) are detected to recognize the object (7) at the same distance (15) to the first ultrasonic sensor (8) and / or at the same transit time of the second ultrasonic signal (13). [7] Method according to any one of the preceding claims, characterized by, that the first ultrasound signal (12) and the second ultrasound signal (13) are additionally received by at least one second ultrasound sensor (9) of the ultrasound sensor device (2) and a second reference curve (R2) with a second threshold range (S") is generated depending on the second amplitudes (A2) of the first ultrasound signal (12) received by the second ultrasound sensor (9) and are compared with the second amplitudes (A2) of the second ultrasound signal (13) received by the second ultrasound sensor (9) as a second comparison curve (V) and the object (7) is detected when a predetermined second number of received echo amplitudes (A3) of the second comparison curve (V) are detected outside the second threshold range (S"). [8] Method according to claim 7, characterized by, that the object (7) is detected when a first echo count of received echo amplitudes (A3) from the first ultrasonic sensor (8) is equal to or greater than a second echo count of received echo amplitudes (A3) from the second ultrasonic sensor (9). [9] Method according to one of claims 7 or 8, characterized by , that the object (7) is detected if the first ultrasonic sensor (8) and the second ultrasonic sensor (9) each detect the object (7) by comparison. [10] Method according to any one of the preceding claims, characterized by , that the first ultrasound signal (12) is emitted at the first time (t1) when the motor vehicle (1) is brought to a standstill, in particular when it is parked. [11] Method according to claim 10, characterized by , that the first ultrasonic signal (12) is emitted at the first time (t1) when the motor vehicle (1) is locked by a user. [12] Method according to any one of the preceding claims, characterized by , that the second ultrasonic signal (13) is emitted at the second time (t2) when the motor vehicle (1) is started by a user. [13] Electronic computing device (11) with a computer program product, wherein the electronic computing device (11) is configured to perform the method according to any one of claims 1 to 12. [14] Ultrasonic sensor device (2) for a motor vehicle (10) comprising at least one first ultrasonic sensor (8) and an electronic computing device (11) according to claim 13, wherein the ultrasonic sensor device (2) is configured to carry out the method according to any one of the preceding claims 1 to 12. [15] Ultrasonic sensor device (2) according to claim 14, wherein at least the first ultrasonic sensor (8) is configured for sending and receiving ultrasonic signals (12, 13) and the ultrasonic sensor device (2) has at least a second ultrasonic sensor (9) which is configured at least for receiving ultrasonic signals (12, 13).

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