Method and assistance system for detecting and handling possible false detection situations of a vehicle ultrasonic sensor and a correspondingly equipped motor vehicle

Abstract

The invention relates to a method for detecting false detection situations of a vehicle ultrasonic sensor (9). In this method, first sensor signals recorded at the beginning of a parking period are compared with second sensor signals recorded at the end of the parking period from the ultrasonic sensor (9) for static objects (2, 7) in the immediate vicinity. If this comparison reveals a deviation of the second sensor signals from the first sensor signals, it is concluded that the ultrasonic sensor (9) is covered with snow, and a predetermined safety measure is executed. The invention also relates to an assistance system (11) for carrying out the method and a correspondingly equipped motor vehicle (4).

Description

[0001] The present invention lies in the field of automotive engineering and relates to a method and an assistance system for detecting and handling possible false detection situations of an ultrasonic sensor in a motor vehicle. The invention also relates to a correspondingly equipped motor vehicle.

[0002] Modern motor vehicles can utilize a wide variety of sensors and driver assistance systems. However, these can exhibit different behaviors or limitations under varying conditions. Therefore, there is a need for solutions that allow for the simple, reliable, and practical handling of such situations.

[0003] US Patent 10,330,644 B2 describes a method in which a single sensor transmits a multitude of signals at different frequencies and receives corresponding reflections. Attenuation values ​​are then determined only for the reflected signals that have the same travel time. Differences between pairs of attenuation values ​​are then converted into a reading of relative humidity.

[0004] US Patent 6,492,902 B2 describes an ultrasound-based obstacle detector. This detector comprises several ultrasonic sensors arranged such that one of them can directly receive waves emitted by another of the ultrasonic sensors. Depending on the received level of these direct waves, foreign matter adhering to at least one of the ultrasonic sensors is then to be detected.

[0005] US Patent 8,502,653 B2 describes an object detection device with a plurality of ultrasonic sensors mounted on a vehicle. Based on received reflected versions of waves emitted by the ultrasonic sensors, the device is designed to detect whether an object is in the vicinity of the vehicle or whether snow is adhering to an ultrasonic sensor. The latter is detected based on the length of an echo wave exceeding a predefined threshold.

[0006] DE 101 42 075 A1 relates to an obstacle detection system which detects obstacles for a vehicle by using an ultrasonic wave.

[0007] DE 10 2014 106 011 A1 relates to a method for detecting a blocked state of an ultrasonic sensor of a motor vehicle, in which a current actual value of at least one vibration parameter of the ultrasonic sensor is recorded and compared with at least one limit value by means of an evaluation device to detect the blocked state. The disclosure also relates to an ultrasonic sensor device configured to carry out such a method, as well as a motor vehicle with such an ultrasonic sensor device.

[0008] DE 10 2010 021 960 A1 relates to a method for detecting a blocked state of an ultrasonic sensor in a motor vehicle. In a single measurement cycle of the ultrasonic sensor, the following steps are performed: A diaphragm of the ultrasonic sensor is excited for a predetermined excitation duration to emit a sound signal. An electrical reception signal characterizing a vibration of the diaphragm is also generated. The blocked state is then detected by a control unit based on the reception signal. The disclosure also relates to a driver assistance system for a motor vehicle configured to perform such a method, as well as to a motor vehicle with such a driver assistance system.

[0009] The object of the present invention is to enable improved handling of conditions that are at least potentially problematic for ultrasonic sensors.

[0010] This problem is solved by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0011] The method according to the invention can be used to detect and handle potential false detection situations of at least one ultrasonic sensor for environmental sensing of a motor vehicle. Thus, situations in which the ultrasonic sensor does not provide reliable data or measured values ​​can be detected, and appropriate action can then be taken. In one step of the method according to the invention, a probability of snowfall is determined for a parking period of the motor vehicle. The parking period is defined here as the period during which the motor vehicle is expected to be parked. The probability of snowfall for the respective parking period can be determined, in particular, before or at the beginning of the parking period, for example, during a parking maneuver.For example, relevant data can be retrieved from a weather service and / or relevant environmental or weather measurement data from corresponding sensors of the vehicle, such as temperature, humidity, air pressure, cloud cover or solar radiation and / or the like, can be recorded and evaluated.

[0012] The process continues only if the probability of snowfall exceeds a predetermined threshold. In a further step of the inventive method, initial sensor signals from the ultrasonic sensor are then detected, particularly immediately before the vehicle is switched off for parking (i.e., during the parking period), but already in a final parking position. These initial sensor signals are detected for static objects or areas in the immediate vicinity of the vehicle. These initial sensor signals are thus recorded by the ultrasonic sensor when the vehicle is already stationary at the beginning of the parking period. For example, the initial sensor signals can be recorded after a parking mode or parking state has been selected, such as the usual gear or drive position P, before the vehicle is completely switched off.Since these initial sensor signals are captured or recorded at the beginning of the parking period, they can also be referred to as initial sensor signals. These initial sensor signals, or parameter values ​​determined through automatic evaluation of these initial sensor signals for one or more predefined parameters or properties of the signals or the vehicle's environment represented by them, can then be stored, for example, in the vehicle's data storage system.

[0013] Static objects here are fixed, i.e., non-moving objects, such as permanently installed parts of road infrastructure, curbs, guardrails, posts, bollards, walls, buildings, and / or the like. In contrast, non-static objects can be moving objects, such as other vehicles or road users, regardless of whether they actually move during the parking period.

[0014] A further process step of the method according to the invention is then carried out while the vehicle is still in the same parking position at the end of the parking period when it is restarted. In this process step, sensor signals from the ultrasonic sensor are again recorded, i.e., second sensor signals from the ultrasonic sensor, at least, i.e., also or only for the same static objects or areas. Since these second sensor signals are recorded at the end of the parking period, they can also be referred to as end sensor signals. These end sensor signals are then compared with the initial sensor signals. Various predefined quantities or parameters can be considered, such as a signal propagation time, a distance to the respective reflecting object or area measured or calculated using the sensor signals, a signal strength, a signal energy, etc.an area under a recorded signal curve, a decay time of a detection membrane of the ultrasonic sensor and / or the like.

[0015] In a further step of the inventive method, if this comparison, for example according to at least one predetermined criterion, indicates a change, i.e., a deviation of the second sensor signals from the first sensor signals, then it is concluded that the ultrasonic sensor is covered with snow. Such snow cover can lead to false detections or incorrect distance measurements by the ultrasonic sensor. Therefore, at least one predetermined safety measure is then automatically implemented. The predetermined criterion could, for example, be the reaching or – depending on the implementation – the exceeding or falling below of a predetermined absolute or percentage deviation threshold, i.e., a corresponding difference.Depending on the thickness or density of the snow cover, it may not completely block the ultrasonic signals, allowing them to continue being transmitted into the environment and enabling the ultrasonic sensor to detect signals reflected from the environment. However, the snow cover can lead to signal attenuation or, for example, affect the signal travel time to and from a specific static object—that is, an object located at a fixed or unchanging distance from the vehicle or the ultrasonic sensor. Therefore, a single distance measurement alone is not necessarily sufficient to reliably detect snow cover, although this may be possible under certain circumstances or conditions, or it can be used as an additional indicator. The automatically executed safety measure may be a single action or comprise several sub-measures.The security measure to be implemented can be fixed or, for example, automatically selected from several possible predefined security measures depending on the situation, for example according to a corresponding specification or allocation table or the like.

[0016] As a safety measure, for example, a corresponding warning can be issued to the driver of the vehicle, specifically including information, identification, or a display of the affected ultrasonic sensor. This can make it easier for the driver to clean the affected ultrasonic sensor manually or semi-automatically. Similarly, as a safety measure, the warning threshold of the ultrasonic sensor for approach or collision warnings can be adjusted so that a warning is triggered earlier compared to normal operation without snow covering the ultrasonic sensor. Additional or alternative safety measures are also possible, which will be discussed elsewhere.

[0017] Although only one ultrasonic sensor is mentioned here as a representative example, the procedure can be applied accordingly to several or all of the vehicle's ultrasonic sensors intended for environmental sensing. If necessary, the implemented safety measure can be selected or adapted depending on which of the vehicle's multiple ultrasonic sensors are covered with snow or what limitations this imposes on environmental sensing.

[0018] Since the recording and evaluation of the first and second sensor signals are carried out at the same parking position but with a time interval, and since sensor signals for and from static objects are used, a reference value comparison can be implemented, with the first sensor signals serving as the reference value for the second sensor signals. This allows for particularly reliable and accurate detection of changes in the situation that occurred during the parking period. In conjunction with the considered probability of snowfall, this also enables the detection of potentially interfering snow buildup on the ultrasonic sensor, which cannot be detected, or cannot be reliably detected, with previous approaches to detecting contamination of the ultrasonic sensor.Since ultrasonic sensors can be important sources of information, especially for parking maneuvers, such as exiting the parking space after the parking period, which other assistance systems or functions and / or the driver of the motor vehicle often rely on, the present invention can be particularly useful in order to avoid collisions or damage when exiting the parking space.

[0019] Specifically, only sensor signals from static objects at a distance of no more than 2.5 m or no more than 2 m from the respective ultrasonic sensor can be used. This allows for particularly reliable and accurate detection of any snow cover. This is based on the understanding that sensor signals or reflected ultrasonic signals from objects located at a greater distance are often noisier, and therefore may have a poorer signal-to-noise ratio.

[0020] In one possible embodiment of the present invention, objects in the vicinity of the parked position, or in the vicinity of the vehicle while it is parked, are automatically detected, particularly by means of sensors, i.e., by means of appropriate environmental sensors in the vehicle. In other words, the respective environment is scanned or recorded, for example, by sensors. Similarly, high-resolution or high-precision map data and / or data or signals emitted by objects in the environment, for example, received via a Car2X connection, can be used. The detected objects are then classified, i.e., categorized, into moving objects, stationary objects, and unknown objects.For the comparison of the second sensor signals with the first sensor signals of the ultrasonic sensor, only the ultrasonic sensor signals for objects classified as static are used. If no static objects, or at least no suitable ones (i.e., objects located at a predetermined distance or in a spatial relationship to the ultrasonic sensor), are present or detected in the respective environment, then, specifically, only the ultrasonic sensor signals for a ground area in the vicinity of the vehicle are used for comparison. For example, a ground echo test can be performed, and an envelope of the respective environment or scene can be recorded or stored. However, this envelope would typically also represent any moving objects that might be present. Therefore, the envelope can then be reduced to the ground area.Corresponding ground echoes can be detected, for example, based on the known, i.e., predetermined, position and orientation of the ultrasonic sensor in or on the vehicle, in conjunction with the detected signal propagation time and direction. The embodiment of the present invention proposed here enables reliable detection of snow accumulation on the ultrasonic sensor even in situations where there are no suitable static objects in the immediate vicinity of the vehicle or its parking position. Sensor signals from ground areas as well as from other static objects can be used for this purpose. This allows for a correspondingly larger signal quantity or data set to be obtained and evaluated, thus enabling particularly reliable detection of any snow accumulation on the ultrasonic sensor.

[0021] In a further possible embodiment of the present invention, the static objects are detected or identified by means of a camera of the vehicle arranged to capture its surroundings. In other words, image or camera data from a corresponding environmental or environmental detection camera of the vehicle can be used to detect static objects. For this purpose, for example, appropriate predefined image processing or object recognition methods can be applied, in particular a suitably trained machine learning system. Static objects can be detected with particular accuracy and reliability using a suitable camera. Likewise, a combination of data or signals from the ultrasonic sensor and data or signals from the camera—and / or other environmental sensors—can also be used to detect the static objects. For this purpose, for example, a sensor or...Signal or data fusion can be applied. This can enable even more accurate and robust detection of static objects.

[0022] In a further possible embodiment of the present invention, the criterion for the deviation, i.e., for the detection of such a deviation or a significant deviation of the end sensor signals from the initial sensor signals, is at least also evaluated as to whether a difference between the detected signal energy of the first sensor signals and the detected signal energy of the second sensor signals corresponds to at least a predetermined threshold value or magnitude. For example, it can be checked here whether the signal energy of the second sensor signals is lower than the signal energy of the first sensor signals by at least a predetermined value or magnitude. This could indicate a corresponding attenuation due to snow accumulation or thickening during the parking period. Here, for example, the area under a signal curve or signal envelope, i.e., its integral, can be used or evaluated.In this context, the assumption or boundary condition can be used that the signal propagation time between the ultrasonic sensor and a specific static object for the final sensor signals lies or remains within a predefined interval around the signal propagation time between the ultrasonic sensor and the same static object for the initial sensor signals. Such a predefined interval can, for example, take into account measurement accuracy or tolerance as well as any change in the signal propagation time due to snow accumulation, whereby the latter effect, if present, is typically small compared to the total signal propagation time.Because the initial and final sensor signals are recorded while the vehicle and the respective static object are in the same fixed relative spatial position, it can be ruled out that a change in signal energy is caused by a change in distance, such as an increased signal path. Therefore, under the described circumstances, a change in signal energy can be a suitable criterion for detecting snow buildup on the ultrasonic sensor. If, for example, a significantly altered signal propagation time were also detected, this could be due to a different type of buildup or contamination of the ultrasonic sensor, or to a misclassification of the respective object as a static object.

[0023] In a further possible embodiment of the present invention, the actual duration of the parking period is also determined when the vehicle is put into operation at or towards the end of the parking period. This allows the time elapsed since the vehicle came to a stop in the parked position to be determined. This time, i.e., the actual duration of the parking period, is then taken into account as a constraint for inferring whether the ultrasonic sensor is covered with snow. If, for example, the vehicle was parked for only a relatively short period, such as 5 minutes, particularly in relatively light snowfall, the probability of snow covering the ultrasonic sensor, or at least of a disruptive snow cover, may be lower than after a longer parking period, for example, if the vehicle was parked overnight, particularly in relatively heavy snowfall.Taking the actual duration of the parking period into account, a plausibility check of snow cover or snow cover detection can be performed. Similarly, a confidence level, or measure of trust, for the detection of snow cover can be determined based on the actual duration of the parking period. This confidence level can then be considered, for example, when selecting or adjusting security measures. For instance, certain security measures can only be implemented if the confidence level is above a predefined threshold, and / or the driver can be informed of the determined confidence level or measure, or a corresponding probability of snow cover being detected.The embodiment of the present invention proposed here allows the detection of snow cover to be improved and any reaction to it to be selected or designed in a particularly situation-appropriate manner.

[0024] In a further possible embodiment of the present invention, any moving objects in the vicinity of the parked vehicle or the vehicle are automatically detected both before the vehicle is switched off and immediately after it is started up, i.e., at the beginning and end of the parking period. In other words, the environment can be examined for moving objects, for example, using sensors, particularly those integrated into the vehicle's environmental sensors. Based on this, changes in the number, position, and / or type of moving objects detected before the vehicle is switched off (i.e., at the beginning of the parking period) and immediately after it is started up (i.e., at the end of the parking period) are then determined.In other words, the system evaluates whether, during the parking period, at least one moving object has moved away from its initial position and / or whether a moving object not present at the beginning of the parking period has entered the area. If such changes are detected, or if the detected changes reach or exceed a predefined threshold, the comparison of the end sensor signals with the initial sensor signals to detect potential snow accumulation on the ultrasonic sensor—and consequently the corresponding safety measure—will not be executed.

[0025] This takes into account that the movements of moving objects, especially other vehicles or road users, could disrupt the process. For example, if no other moving objects were detected when the vehicle was parked (i.e., at the beginning of the parking period), but several moving objects are detected in the vicinity of the vehicle at the end of the parking period (i.e., when the vehicle is restarted), these moving objects can interfere with or influence the end sensor signals. For instance, such newly added moving objects could obscure a static object for which initial sensor signals were recorded, from the perspective of the ultrasonic sensor, or lead to altered signal paths, for example, through multiple reflections or similar effects.Accordingly, a confidence level or measure of trust can be determined based on the detected changes. As soon as moving objects are detected in the environment—and thus a risk of interference exists—the confidence level or measure of trust can decrease. If the confidence level or measure of trust falls below a predetermined threshold, the process can be terminated. The proposed embodiment of the present invention allows for a significantly higher frequency of correct detection of snow cover, thereby minimizing false positives. Consequently, inappropriate implementation of at least one predetermined safety measure can be largely avoided.

[0026] In a further possible embodiment of the present invention, the safety measure, or part thereof, involves downgrading or deactivating a maneuvering assistance system of the motor vehicle. Such a maneuvering assistance system can, for example, be or include an assistance system for assisted or automated parking maneuvers and / or, for example, an assistance system for other automated driver interventions, such as sensor-triggered emergency braking or the like. Downgrading can, for example, mean or include adjusting warning or intervention thresholds, reducing the intensity of the intervention, or excluding only certain interventions or types of intervention. The embodiment of the present invention proposed here can prevent or reduce automated error reactions based on faulty or inaccurate sensor data.

[0027] In a further possible embodiment of the present invention, a different type of environmental sensor of the vehicle is used as the safety measure or as part thereof for detecting obstacles, i.e., for the task of the ultrasonic sensor, instead of this ultrasonic sensor. In particular, this can only be done for the detection range of the respective ultrasonic sensor that is at least apparently covered with snow. Thus, if the vehicle has, for example, several ultrasonic sensors, such as front and rear ultrasonic sensors, and snow cover is detected for only one of these ultrasonic sensors or only for some of these ultrasonic sensors, the remaining ultrasonic sensors can continue to be used as intended. As a different type of environmental sensor, i.e., as an alternative to the apparently snow-covered ultrasonic sensor, for example, a suitably arranged or aligned environmental camera can be used.The vehicle's environmental sensing camera is used. The embodiment of the present invention proposed here allows a function that normally relies on data or signals from an ultrasonic sensor to continue to operate, i.e., be used, even when the ultrasonic sensor is covered in snow. This can improve driving or passenger comfort and / or prevent or reduce safety limitations caused by snow covering the ultrasonic sensor. By replacing affected ultrasonic sensors with other environmental sensors only where necessary, the behavior of the vehicle and its corresponding functions can be affected as little as possible.

[0028] The present invention also relates to an assistance system for a motor vehicle. The assistance system according to the invention comprises a data processing unit for acquiring sensor signals from at least one ultrasonic sensor of the respective motor vehicle, for example via a corresponding input interface. The data processing unit is also configured to process corresponding sensor signals and to generate and output corresponding control signals, for example via a corresponding output interface, for executing or initiating a predetermined safety measure. According to the invention, the assistance system is configured to execute the method according to the invention, in particular automatically.The assistance system, in particular its data processing unit, can, for example, comprise a process unit, such as a microchip, microprocessor, microcontroller, or the like, and a computer-readable data storage device coupled to it. This data storage device can then contain, for example, a corresponding operating or computer program that encodes or implements the process steps, measures, or sequences, or corresponding control instructions, described in conjunction with the method according to the invention. This operating or computer program can then be executed by means of the process unit in order to carry out the corresponding method or to effect its execution. Depending on the configuration, the assistance system according to the invention can have further functions or be integrated into a more comprehensive vehicle system.The assistance system may also include other components, such as at least one ultrasonic sensor and / or an output device for issuing a warning or notification to the driver of the motor vehicle, which may be intended as the safety measure or as part thereof.

[0029] The present invention also relates to a motor vehicle comprising at least one ultrasonic sensor for environmental sensing and the assistance system according to the invention, which is directly or indirectly coupled to or encompasses the sensor. The motor vehicle according to the invention can, in particular, be the motor vehicle mentioned in connection with the method according to the invention and / or in connection with the assistance system according to the invention, or correspond to it. Accordingly, the motor vehicle can have some or all of the features mentioned in these contexts, such as, for example, in addition to the at least one ultrasonic sensor, further environmental sensors, or at least one further environmental sensor, and / or at least one driver assistance function, or the like.

[0030] Further features of the invention may become apparent from the following description of the figures and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0031] The drawing shows in the single figure a schematic overview of a traffic scene with a parked motor vehicle to illustrate a method for recognizing and handling possible false detection situations of an ultrasonic sensor of the motor vehicle.

[0032] Fig.Figure 1 shows a partial schematic overview of a traffic scene at a parking lane 1. This parking lane 1 is bordered laterally by a raised curb 2 and comprises several parking spaces arranged in a row. A motor vehicle 4 is parked in one of these parking spaces, which is referred to here as parking space 3. Parking spaces adjacent to this parking space 3 are referred to here as neighboring parking spaces 5. By way of example, a different vehicle 6 is parked in one of the neighboring parking spaces 5. In addition, some immovable, i.e., static, objects are schematically indicated next to the parking lane 1; these could, for example, be bollards 7.

[0033] The motor vehicle 4 can be driven by a driver 8, for example, parked in and out of parking space 3. To assist the driver 8, the motor vehicle 4 is equipped with several ultrasonic sensors 9 for environmental sensing. These ultrasonic sensors 9 can detect objects or obstacles at a certain distance from the motor vehicle 4 or within a certain radius, such as the curb 2, the other vehicle 6, and the bollards 7. The motor vehicle 4 can also be equipped with a maneuvering assistance system 10. This maneuvering assistance system 10 can intervene in the longitudinal and / or lateral guidance of the motor vehicle 4, i.e., control the motor vehicle 4 accordingly, for example, for assisted or automated parking maneuvers. For this purpose, the maneuvering assistance system 10 can use data or signals from the ultrasonic sensors 9.

[0034] To ensure that the ultrasonic sensors 9 can be used without interference for the described functions, they must not be dirty or covered with foreign matter. Coverage or encrustation of the ultrasonic sensors 9, for example with mud or other substances that strongly reflect or block the emitted ultrasonic signals, can typically be reliably detected, for example by an almost instantaneous reflection of the emitted ultrasonic signals. Snow cover, on the other hand, can be poorly reflective to ultrasonic signals and at least partially permeable, so that it cannot be reliably detected using such conventional methods.

[0035] To address this problem, the vehicle 4 is also equipped with an assistance system 11. This assistance system 11 is represented schematically and by way of example by an interface 12, a processor 13, and a data storage device 14 coupled to it. Furthermore, the vehicle 4 has, by way of example, an output device 15 for issuing warnings to the driver 8 and several other environmental sensors 16. The environmental sensors 16 can be of a different type than the ultrasonic sensors 9. In particular, the environmental sensors 16 can be or include one or more cameras. The aforementioned devices and components can be interconnected via the vehicle 4's electrical system, as schematically indicated here.

[0036] At the beginning of a parking period, i.e., when the vehicle 4 is positioned in parking space 3 or has just been positioned, the assistance system 11 can automatically determine the probability of snow for the subsequent period. For this purpose, the assistance system 11 can use, for example, relevant weather data, sensor data from the environmental sensors 16, such as camera images and / or weather data, and / or audio data recorded by at least one external microphone of the vehicle 4. For example, an external microphone can be used to detect sounds produced when snow is compressed by a passing vehicle.Similarly, the assistance system 11 can use or evaluate, for example, operating or condition data of the vehicle 4, such as the use or setting of heating devices, such as a windshield heater or a parking heater, and / or data from other vehicles or infrastructure facilities, which can be received via a Car2X data connection, to determine or estimate the probability of snow.

[0037] Furthermore, objects that may be present in the vicinity of the vehicle 4 can be automatically detected by sensors, for example, using the ultrasonic sensors 9 and / or the other environmental sensors 16. For example, objects can be detected by optical image processing of camera data or automatic object recognition and / or based on audio data recorded by the external microphone. For example, vehicle noises or the starting or stopping of engines of vehicles in the vicinity can be detected by the external microphone. In particular, audio-based object tracking, i.e., object localization, is also possible using a directional or stereo microphone. In this case, such objects in the vicinity of the vehicle 4 can be detected and located, for example, the curb 2, the other vehicle 6, and the bollards 7. The detected objects are then classified as fixed or moving.Static objects and at least potentially moving objects are categorized, and—if such identification is not unambiguous, reliable, or sufficiently secure—unknown objects are classified. In this case, for example, the assistance system 11 classifies the curb 2 and the bollards 7 as static objects and the foreign vehicle 6 as a moving object. Objects classified as unknown can be ignored for the procedure, i.e., not considered.

[0038] As soon as the vehicle 4 reaches its final position when parking in parking space 3, the ultrasonic sensors 9 record initial sensor signals for the detected static objects, in this case, for example, the curb 2 and the bollards 7. These initial sensor signals, or values ​​derived or determined from them, can then be stored by the assistance system 11 in the data storage device 14.

[0039] If the vehicle 4 is reopened or put back into operation at the end of the parking period and the probability of snow is or was greater than a predetermined threshold, then second sensor signals for the same static objects can be recorded by the ultrasonic sensors 9 and captured or processed by the assistance system 11 while the vehicle 4 is still in the same position.

[0040] The sensor signals recorded at the beginning and end of the parking period are then compared by the assistance system 11, for example, to compare calculated distances to static objects and / or signal energies and / or similar parameters. If corresponding parameter values ​​according to the second set of sensor signals recorded at the end of the parking period differ from the corresponding data or values ​​stored at the beginning of the parking period, which were determined based on the first set of sensor signals, the assistance system 11 can automatically execute or initiate a corresponding safety measure.

[0041] For example, as a safety measure, a warning or notification can be issued to the driver 8 via the output device 15, for example, regarding a potentially limited functionality of the ultrasonic sensors 9 or functions dependent on them, and / or as a request to clean the ultrasonic sensors 9. Likewise, warning thresholds of the ultrasonic sensors 9 or functions based on their sensor signals can be adjusted. Similarly, for environmental sensing or obstacle detection, the system can switch from the ultrasonic sensors 9 to the use of the environmental sensors 16, particularly only for affected ultrasonic sensors 9, i.e., those covered with snow, or for corresponding environmental areas. If, for example, snow cover is detected only for the right front ultrasonic sensor 9, the system can switch to the environmental sensors 16 for further environmental sensing or obstacle detection.For obstacle detection, at least in the immediate vicinity of an area to the right front of the vehicle 4, the corresponding ambient sensor 16, which is aligned with this area, is now used instead of the corresponding ultrasonic sensor 9. The remaining ultrasonic sensors 9 can still be used for other areas. Likewise, as a safety measure, the maneuvering assistance system 10 can be downgraded or deactivated. This means that systems or functions that rely on precise data or signals from the ultrasonic sensors 9, such as assisted or automatic parking systems, can be deactivated. Similarly, as a safety measure, an emergency braking system or maneuvering assistant of the vehicle 4 can be downgraded or deactivated to prevent, for example, automated false braking.

[0042] A complete deactivation of the maneuvering assistance device 10, i.e., for example, a corresponding parking assistant, can be carried out, for example, if the probability of snow exceeding a specified threshold is present on all sides of the vehicle 4, or if snow cover is detected by all ultrasonic sensors 9 with a specified minimum probability or minimum confidence.

[0043] Likewise, the time between a parking maneuver of motor vehicle 4 and a corresponding exit maneuver or its beginning can be taken into account.

[0044] Similarly, actual or potential disturbances caused by moving objects in the environment, such as the foreign vehicle 6, can be taken into account.

[0045] Overall, the examples described show how a method for improving false detections of ultrasonic sensors 9 of a vehicle can be implemented and applied. Reference symbol list 1 parking lane 2. Curbstone 3 parking spaces 4 Motor vehicle 5 neighboring parking spaces 6 foreign vehicle 7 bollards 8 drivers 9 ultrasonic sensors 10 Maneuver assistance equipment 11 Assistance systems 12 Interface 13 processor 14 Data storage 15 Output device 16 environmental sensors

Claims

[1] Method for detecting and handling possible false detection situations of an ultrasonic sensor (9) of a motor vehicle (4), wherein automatically - for a parking period of the motor vehicle (4) a probability of snow is determined and only if the probability of snow is greater than a specified threshold, - before the motor vehicle (4) is switched off, but already in a parking position (3) of the motor vehicle (4) the first sensor signals of the ultrasonic sensor (9) for static objects (2, 7) in the vicinity of the motor vehicle (4) are detected, - while the motor vehicle (4) is still in the same parking position (3) at the end of the parking period when the motor vehicle (4) is started, second sensor signals from the ultrasonic sensor (9) for the static objects (2, 7) are detected and compared with the first sensor signals, - if this comparison reveals a deviation of the second sensor signals from the first sensor signals, it is concluded that the ultrasonic sensor (9) is covered with snow and a specified safety measure is carried out. [2] Method according to claim 1, characterized by , that first objects (2, 6, 7) in the vicinity of the parking position (3) are automatically detected and classified into moving objects (6), static objects (2, 7) and unknown objects, and for comparison only sensor signals from the ultrasonic sensor (9) for objects (2, 7) classified as static objects (2, 7) are used, wherein in the case that no static objects (2, 7) were detected, for comparison only sensor signals from the ultrasonic sensor (9) for a ground area in the vicinity of the motor vehicle (4) are used. [3] Method according to any one of the preceding claims, characterized by, that the static objects (2, 7) are detected by means of a camera (16) of the motor vehicle (4) arranged to detect the respective surroundings of the motor vehicle (4). [4] Method according to any one of the preceding claims, characterized by , that the criterion for the deviation is evaluated as whether a difference between the detected signal energy of the first sensor signals and the detected signal energy of the second sensor signals corresponds to at least a predefined threshold value. [5] Method according to any one of the preceding claims, characterized by , that when the motor vehicle (4) is put into operation at the end of the parking period its actual duration is determined and is taken into account as a secondary condition for concluding that the ultrasonic sensor (9) is covered with snow. [6] Method according to any one of the preceding claims, characterized by , that - moving objects (6) in the vicinity of the parking position (3) are detected both before switching off and immediately after starting up the motor vehicle (4), - Changes in the number and / or position and / or type of moving objects (6) detected before the motor vehicle (4) is switched off and after the motor vehicle (4) is started are determined, and - in the event that corresponding changes are detected or these changes reach or exceed a predetermined level, the comparison to detect the occupancy of the ultrasonic sensor (9) with snow is not carried out. [7] Method according to any one of the preceding claims, characterized by , that as a safety measure a maneuvering assistance system (10) of the motor vehicle (4) is downgraded or deactivated. [8] Method according to any one of the preceding claims, characterized by, that as a safety measure, in particular only for the detection range of the snow-covered ultrasonic sensor (9), a different type of environmental sensor of the motor vehicle (4), in particular a camera (16) of the motor vehicle (4), is used to detect obstacles instead of this ultrasonic sensor (9). [9] Assistance system (11) for a motor vehicle (4), comprising a data processing device (12, 13, 14) for acquiring sensor signals from an ultrasonic sensor (9) of the respective motor vehicle (4), for processing the sensor signals and for generating and outputting corresponding control signals for executing or initiating a predetermined safety measure, wherein the assistance system (11) is configured to execute the method according to one of the preceding claims. [10] Motor vehicle (4) comprising at least one ultrasonic sensor (9) for environmental detection and the assistance system (11) according to claim 9.

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