Method for determining the attenuation of an ultrasound signal, driver assistance system and motor vehicle

Abstract

Method for determining the attenuation (D) of an ultrasonic signal (8) from an ultrasonic sensor (4) for a motor vehicle (1) in an ambient area (7) of the motor vehicle (1), wherein in the method a current temperature (T) in the ambient area (7) of the motor vehicle (1) is detected by means of a vehicle-side temperature sensor (9), wherein a current position (P) of the motor vehicle (1) is detected, based on the current position (P) a current humidity (F) in the ambient area (7) of the motor vehicle (1) is determined from provided weather data (11) and based on the current humidity (F) and the current temperature (T) the attenuation (D) of the ultrasonic signal (8) in the ambient area (7) is determined, characterized by the fact that Additionally, a current calendar date and / or time is recorded. wherein an in-vehicle and / or external weather database (12) is provided within which humidity values ​​are specified for predetermined data sets, wherein each data set includes a predetermined position as well as a predetermined time and / or a predetermined calendar date, and the corresponding humidity value is determined as the current humidity (F) based on the recorded current position (P) as well as the recorded current time and / or the recorded current calendar date.

Description

[0001] The invention relates to a method for determining the attenuation of an ultrasonic signal from an ultrasonic sensor for a motor vehicle in an area surrounding the motor vehicle, wherein a temperature sensor is used to detect the current temperature in the area surrounding the motor vehicle. The invention also relates to a driver assistance system and a motor vehicle.

[0002] It is already known from the prior art to install ultrasonic sensors on a motor vehicle and use these sensors to detect objects in the vicinity of the vehicle. For this purpose, the ultrasonic sensors emit an ultrasonic signal and receive the ultrasonic signal reflected by the object. Information about the detected object, such as its distance from the vehicle, can be provided to a driver assistance system, such as a parking assistance system. However, attenuation of the ultrasonic signal in the vicinity of the vehicle, a phenomenon known as airborne sound attenuation, significantly impairs distance measurement; that is, objects in the vicinity of the vehicle may no longer be detected if airborne sound attenuation is high.

[0003] It is known that both ambient temperature and humidity have a significant influence on the airborne sound attenuation of the ultrasonic signal. To take the airborne sound attenuation of an ultrasonic sensor into account and improve its measurement reliability, DE 10 2008 054 047 A1 proposes installing temperature and humidity sensors on the vehicle to measure the temperature and humidity of the sound-transmitting medium, i.e., the ambient air. However, humidity sensors are generally very expensive.

[0004] German patent application DE 10 2013 219 680 A1 discloses a method for reducing obstacle detection errors in a parking assistance system, whereby information on humidity and temperature is used to compensate for signal attenuation. Weather information can also be received from remote sources via a wireless communication link.

[0005] The object of the present invention is to be able to determine the attenuation of an ultrasound signal in a particularly simple and cost-effective manner.

[0006] This task is solved as intended by a method, a driver assistance system and a motor vehicle with the features according to the independent patent claims.

[0007] A method according to the invention serves to determine the attenuation of an ultrasonic signal from an ultrasonic sensor for a motor vehicle in an area surrounding the vehicle. In this method, a vehicle-mounted temperature sensor is used to detect the current temperature in the area surrounding the vehicle. Furthermore, the current position of the vehicle is detected, and based on the current position and provided weather data, the current humidity in the area surrounding the vehicle is determined. Finally, based on the current humidity and temperature, the attenuation of the ultrasonic signal in the area surrounding the vehicle is determined.

[0008] The method according to the invention thus determines the airborne sound attenuation of the ultrasound signal in the vicinity of the motor vehicle. The attenuation of the ultrasound signal particularly affects the detection performance and / or detection range of the ultrasound sensor. The higher the airborne sound attenuation, the lower the detection performance and / or detection range of the ultrasound sensor.

[0009] To determine the attenuation of the ultrasonic signal, the parameters of the surrounding area that influence attenuation are recorded. One such parameter is the current temperature in the surrounding area, measured using the vehicle's temperature sensor. However, the other parameter, humidity, is not measured using a humidity sensor as is known in the prior art, but rather determined based on the vehicle's current position. This position can be recorded, for example, by a vehicle-mounted detection device. The current weather or climate data for the vehicle's current position, and thus the current weather or climate data for the surrounding area, are read from a provided weather database.The weather data includes the current humidity at the vehicle's current location. This also provides information about the current humidity in the vehicle's surrounding area. Based on the measured temperature and humidity, the attenuation of the ultrasound signal in this environment is then determined or calculated.

[0010] This method offers the advantage that no additional sensors need to be provided for the vehicle. The ambient temperature of the vehicle is typically measured using a temperature sensor already installed on the vehicle. The vehicle's current position is also usually recorded, for example, for a navigation system. Based on this data, which is generally collected as standard, the attenuation of the ultrasonic signal can then be determined very easily, especially without having to install an expensive humidity sensor in the vehicle.

[0011] The position of the motor vehicle is preferably determined using a global positioning system (GPS). For this purpose, the motor vehicle is equipped with a GPS device by which its current position in geographical coordinates can be recorded in a manner known per se, for example, for navigation purposes. GPS allows the position of the motor vehicle to be determined with particular accuracy, and consequently, the current humidity at that location can be recorded with particular accuracy.

[0012] Preferably, the current humidity is determined using an internet-based weather database that provides weather data. For this purpose, the vehicle can be equipped with an evaluation unit, such as an in-vehicle control unit, designed to access the internet. The current weather or weather information at the vehicle's location, recorded by a GPS device, can then be retrieved from the weather database, for example, via a website displaying the current weather. This weather information includes the current humidity at the vehicle's current location. An internet-based weather database offers the advantage of being constantly updated. Therefore, only the vehicle's current location needs to be determined.Using this current position, the current weather and thus the current humidity, as well as the current temperature to verify the measured temperature, can be read from the internet at any time.

[0013] According to the invention, a current calendar date and / or a current time is additionally determined, wherein an internal and / or external vehicle weather database is provided as the weather database, within which humidity values ​​are specified for predetermined data sets, wherein each data set includes a predetermined position as well as a predetermined time and / or a predetermined calendar date, and based on the recorded current positions as well as the recorded current time and / or the recorded current calendar date, the associated humidity value is determined as the current humidity.

[0014] Such a vehicle-internal and / or vehicle-external weather database is, in particular, an annual weather map that displays the humidity at a specific location or position over the course of a year and, especially, over the course of a day. This annual weather map can, for example, include weather data from the previous year or weather data averaged over several years. Based on the current location, the corresponding annual weather map can then be selected, and the weather, and thus the humidity, for the current time of year and / or day can be read from the selected annual weather map based on the recorded time and / or calendar date.This embodiment offers the advantage that the current humidity can be determined even if the vehicle is, for example, in a dead zone and has no access to the internet and therefore no access to an internet-based weather database.

[0015] According to a further development of the invention, a predetermined temperature value is additionally specified in each data record of the vehicle's internal and / or external database. Furthermore, the humidity value associated with the corresponding data record is determined as the current humidity based on the recorded temperature. Since the vehicle's internal and / or external database is designed as an annual weather map with predetermined weather data, the recorded temperature can be used to additionally verify whether the current humidity is plausible or realistic. This is particularly advantageous when reliable weather data cannot be provided for certain locations. This is the case, for example, at locations where high temperature fluctuations can occur within a month or at locations where several values ​​from the previous year, recorded at the same time, differ significantly from one another.At such a position, humidity values ​​can be specified for different temperatures, for example, whereby the humidity value corresponding to the recorded current temperature is selected as the current humidity.

[0016] Preferably, the detection range of the ultrasonic sensor in the surrounding area is adjusted based on the specific attenuation of the ultrasonic signal to detect objects in the vicinity of the vehicle. It is known that the detection range of the ultrasonic sensor decreases with increasing airborne sound attenuation of the ultrasonic signal. The detection range of the ultrasonic sensor can be adjusted to the airborne sound attenuation and advantageously maximized, particularly without so-called ground echoes, i.e., reflections of the ultrasonic signal from the road surface of the vehicle, being detected as signals and thus as objects in the vicinity of the vehicle.

[0017] It may be possible to adjust the detection range by determining a response threshold for the ultrasonic sensor based on the specific attenuation of the ultrasonic signal. The ultrasonic signal received by the sensor is only evaluated and used for object detection if it exceeds this threshold. In other words, the sensor does not respond to ultrasonic signals with a signal strength below the threshold, and therefore objects in the area where the signal is reflected are not detected.

[0018] Preferably, the response threshold is determined as a signal strength for the ultrasonic signal that the ultrasonic signal from the ultrasonic sensor, reflected from the road surface of the vehicle in its intended installation position at a specific attenuation, exhibits. In other words, this means that the signal strength, signal level, or signal amplitude of the ultrasonic signal at a ground echo is determined as the response threshold. Since the ground echo is not to be detected, a reflected ultrasonic signal is only detected when its signal strength exceeds the response threshold. This ensures that the ultrasonic signal was reflected from an object other than the road surface.This allows objects in the surrounding area to be detected with a high degree of reliability, and their distance to the vehicle to be determined. The information about the objects can then be provided, for example, to a parking assistance system, which supports the driver during a parking maneuver.

[0019] Preferably, threshold values ​​are specified for predetermined attenuation values, and the corresponding threshold value is selected based on the determined attenuation of the ultrasonic signal and defined as the response threshold for the ultrasonic sensor. In other words, this means that threshold sets are defined in which the predetermined attenuation values ​​are assigned to the corresponding threshold values, for example, in a list or a characteristic curve. This list or characteristic curve can, for example, be stored in an internal vehicle memory. Based on the attenuation of the ultrasonic signal, determined using the current humidity and temperature, the corresponding threshold value can then be easily read from the list or characteristic curve, for example, by the vehicle's evaluation unit, selected, and defined as the response threshold.Thus, the ultrasonic sensor, in particular its detection range, can be adapted particularly quickly and easily to environmental conditions, especially the climate in the surrounding area.

[0020] It may also be provided that the current air pressure is determined in the same way as the current humidity, and that the attenuation of the ultrasound signal in the surrounding area is determined or calculated based on the current temperature, the current humidity and the current air pressure.

[0021] The invention further relates to a driver assistance system for a motor vehicle for detecting objects in the vicinity of the vehicle, comprising an ultrasonic sensor for emitting an ultrasonic signal into the vicinity and / or for receiving the ultrasonic signal reflected by the object. The driver assistance system also includes an evaluation unit for determining the attenuation of the ultrasonic signal in the vicinity of the vehicle and a temperature sensor for detecting the current temperature in the vicinity of the vehicle. Furthermore, the driver assistance system includes a detection device designed to detect the current position of the vehicle.The evaluation unit of the driver assistance system is designed to determine the current humidity in the surrounding area based on the current position and provided weather data. Based on the current humidity and temperature, it then determines the attenuation of the ultrasonic signal in the surrounding area. The driver assistance system is preferably designed as a parking assistance system, whose ultrasonic sensor can be easily adapted to the ambient conditions using the measured attenuation.

[0022] A motor vehicle according to the invention comprises a driver assistance system according to the invention. The motor vehicle is in particular designed as a passenger car.

[0023] The preferred embodiments and their advantages presented with reference to the method according to the invention apply accordingly to the driver assistance system according to the invention as well as to the motor vehicle according to the invention.

[0024] The terms "top", "bottom", "front", "back", "horizontal", "vertical", "side", etc. indicate the positions and orientations of the ultrasonic sensor when used and positioned correctly on the motor vehicle and viewed by an observer standing in front of the vehicle and looking towards it.

[0025] Further features of the invention are evident from the claims, the figure, and the figure description. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the figure description and / or shown in the figure alone, are not only usable in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments not explicitly shown and explained in the figure, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.

[0026] The invention will now be explained in more detail below with reference to a preferred embodiment and the accompanying drawing.

[0027] The single figure shows a schematic representation of an embodiment of a motor vehicle according to the invention.

[0028] The figure shows a motor vehicle 1 according to an embodiment of the present invention. In this case, the motor vehicle 1 is designed as a passenger car. The motor vehicle 1 has a driver assistance system 2, which can, for example, be configured as a parking assistance system. The driver assistance system 2 comprises an evaluation unit 3, which can, for example, be formed by an electronic control unit of the motor vehicle 1. Furthermore, the driver assistance system 2 comprises at least one ultrasonic sensor 4.

[0029] Here, the driver assistance system 2 comprises eight ultrasonic sensors 4, four of which are arranged at the front 5 and four at the rear 6 of the vehicle 1. The ultrasonic sensors 4 are specifically designed to detect an object in the vicinity 7 of the vehicle 1. Furthermore, the ultrasonic sensors 4 can also be designed to determine the distance between the vehicle 1 and the object in the vicinity 7. To detect the object in the vicinity 7, each of the ultrasonic sensors 4 emits an ultrasonic signal 8 into the vicinity 7 and receives the ultrasonic signal 8 reflected by the object.To determine the distance, the ultrasonic sensors 4 can additionally measure the transit time of the ultrasonic signal 8, i.e., the time between the emission of the ultrasonic signal 8 and the reception of the reflected ultrasonic signal 8.

[0030] The accuracy of the distance determination between the object and the vehicle 1 depends in particular on the attenuation D experienced by the ultrasonic signal 8 in the area 7 surrounding the vehicle 1, which, for example, affects the detection range of the ultrasonic sensor 4. To adapt the detection range of the ultrasonic signal 8 to the attenuation D, the attenuation D in the area 7 must be determined. The attenuation D in the area 7 depends on the environmental conditions there and can vary by a factor of ten, for example, assuming a value between 0.37 dB / m and 3.98 dB / m, depending on the environmental conditions.

[0031] The attenuation D is particularly influenced by the temperature T in the ambient area 7 of the vehicle 1. To detect the temperature T in the ambient area 7, the driver assistance system 2 has a vehicle-mounted temperature sensor 9 or a temperature probe. The vehicle-mounted temperature sensor 9 detects the current temperature T in the ambient area 7 of the vehicle 1 and provides this information to the evaluation unit 3 of the vehicle 1. Furthermore, the attenuation D depends on the relative humidity F in the ambient area 7 of the vehicle 1. For example, the ultrasonic signal 8 experiences a higher attenuation D, for example 2.4 dB / m, in the ambient area 7 at a high temperature T, for example 40 degrees, and a low relative humidity F, for example 20% RH, than in the ambient area 7 at a high temperature T, for example 40 degrees, and a high relative humidity F, for example 90% RH.There, the attenuation D is, for example, only 1 dB / m.

[0032] The humidity F is not measured directly by a vehicle-mounted sensor. Instead, the humidity F in the surrounding area 7 of the vehicle 1 is determined using weather data 11, which characterizes the current weather or climate at a position P of the vehicle 1. To determine the position P of the vehicle 1, the vehicle 1 has a detection device 10 in the form of a GPS device, which is designed to determine the position P of the vehicle 1 in geographical coordinates in a manner known per se. The detected current position P of the vehicle 1 is also provided to the evaluation unit 3. Based on the current position P, the evaluation unit 3 determines the current humidity F from the weather data 11, which is provided, for example, in a database 12.Database 12 can be either an internal vehicle database and / or an external vehicle database, for example an internet-based database.

[0033] In an internet-based database 12, the weather data, and thus also the weather data 11 at position P, are constantly updated. Therefore, it is sufficient to only record the current position P of the vehicle 1 and, based on position P, to read the current humidity F in the surrounding area 7 from the constantly updated weather data 11 of database 12.

[0034] It can also be provided that the weather data 11 are stored in an annual weather map in an internal and / or external vehicle database, which can be read by the evaluation unit 3. This annual weather map displays humidity values ​​at a specific location over the course of a year and, for example, also over a day. According to the invention, in order to extract the current humidity F from the annual weather map, the vehicle 1 also records a current time and a current calendar date. Thus, the annual weather map corresponding to the recorded current location P can be identified, and the corresponding humidity value can be read from the annual and / or daily weather pattern depicted in the annual weather map, i.e., at the corresponding calendar date and / or time.Providing the annual weather map offers the advantage that the weather data 11 can also be provided when the vehicle 1 is located in a radio dead zone and has no internet access, for example to an internet-based weather database.

[0035] Based on the current humidity F and the current temperature T, the current attenuation D in the surrounding area 7 of the vehicle 1 can be determined in a particularly simple way. In addition to the humidity F, the current air pressure can also be read from the weather data 11 and taken into account when determining the attenuation D in the surrounding area 7.

[0036] Based on the determined attenuation D, the detection range of the ultrasonic sensor 4 can be adjusted. For this purpose, a response threshold for the ultrasonic sensor 4 is determined. The response threshold is a characteristic signal strength of a reflected ultrasonic signal 8 in a standard installation position on the vehicle 1, which the reflected ultrasonic signal 8 exhibits after reflection from the road surface of the vehicle 1. Since the road surface of the vehicle 1 is generally not to be detected, it is advantageous that the ultrasonic sensor 4 does not react to the reflection from the road surface, i.e., a so-called ground echo.

[0037] For example, threshold values ​​can be specified at predetermined damping values ​​and provided, for instance, in a list or a characteristic curve. Depending on the specified damping D, the corresponding threshold value can then be selected as the current response threshold and set for the ultrasonic sensor 4. This allows the detection range of the ultrasonic sensor 4 to be maximized without ground echoes being detected as objects in the vicinity 7 of the vehicle 1.

Claims

[1] Method for determining the attenuation (D) of an ultrasonic signal (8) of an ultrasonic sensor (4) for a motor vehicle (1) in an ambient area (7) of the motor vehicle (1), wherein in the method a current temperature (T) in the ambient area (7) of the motor vehicle (1) is detected by means of a vehicle-side temperature sensor (9), wherein a current position (P) of the motor vehicle (1) is detected, based on the current position (P) a current humidity (F) in the ambient area (7) of the motor vehicle (1) is determined from provided weather data (11) and based on the current humidity (F) and the current temperature (T) the attenuation (D) of the ultrasonic signal (8) in the ambient area (7) is determined, characterized by , that Additionally, a current calendar date and / or time is recorded. wherein an in-vehicle and / or external weather database (12) is provided within which humidity values ​​are specified for predetermined data sets, wherein each data set includes a predetermined position as well as a predetermined time and / or a predetermined calendar date, and the corresponding humidity value is determined as the current humidity (F) based on the recorded current position (P) as well as the recorded current time and / or the recorded current calendar date. [2] Method according to claim 1, characterized by , that the current position (P) of the motor vehicle (1) is determined by means of a global positioning system. [3] Method according to claim 1 or 2, characterized by , that the current humidity (F) at the current position (P) is determined by means of an internet-based weather database (12) providing weather data (11). [4] Method according to claim 1, characterized by , that in the vehicle-internal and / or vehicle-external database (12) a predetermined temperature value is additionally specified in each data record, whereby the humidity value associated with the corresponding data record is additionally determined as the current humidity (F) based on the recorded temperature (T). [5] Method according to any one of the preceding claims, characterized by , that depending on the specific attenuation (D) of the ultrasonic signal (8) a detection range of the ultrasonic sensor (4) in the surrounding area (7) is adapted to detect objects in the surrounding area (7) of the motor vehicle (1). [6] Method according to claim 5, characterized by, that the detection range is adjusted by determining a response threshold for the ultrasonic sensor (4) depending on the specific attenuation (D), wherein the ultrasonic signal (8) received by the ultrasonic sensor (4) is only evaluated if the ultrasonic signal (8) exceeds the response threshold. [7] Method according to claim 6, characterized by , that the response threshold is determined to be a signal strength for the ultrasonic signal (8) which the ultrasonic signal (8) of the ultrasonic sensor (4) reflected on a roadway of the motor vehicle (1) has in a standard installation position of the ultrasonic sensor (4) on the motor vehicle (1) at the specified attenuation (D). [8] Method according to claim 6 or 7, characterized by, that threshold values ​​are specified for predetermined damping values ​​and, depending on the determined damping (D), the corresponding threshold value is selected and determined as the response threshold for the ultrasonic sensor (4). [9] Driver assistance system (2) for a motor vehicle (1) for detecting objects in an ambient area (7) of the motor vehicle (1) comprising an ultrasonic sensor (4) for emitting an ultrasonic signal (8) into the ambient area (7) and / or for receiving the ultrasonic signal (8) reflected by the object, an evaluation unit (3) for determining an attenuation (D) of the ultrasonic signal (8) in the ambient area (7) of the motor vehicle (1) and a temperature sensor (9) for detecting a current temperature (T) in the ambient area (7) of the motor vehicle (1), wherein a detection device (10) of the driver assistance system (2) is designed to detect a current position (P) of the motor vehicle (1) and the evaluation unit (3) of the driver assistance system (2) is designed toto determine the current humidity (F) in the surrounding area (7) of the motor vehicle (1) based on the current position (P) from provided weather data (11) and to determine the attenuation (D) of the ultrasonic signal (8) in the surrounding area (7) based on the current humidity (F) and the current temperature (T), characterized by , that the acquisition device (10) of the driver assistance system (2) is designed to additionally acquire a current calendar date and / or a current time, wherein an internal and / or external vehicle weather database (12) is provided, within which humidity values ​​are specified for predetermined data sets, wherein each data set includes a predetermined position as well as a predetermined time and / or a predetermined calendar date, and the evaluation unit (3) of the driver assistance system (2) is designed to determine the corresponding humidity value as the current humidity (F) based on the recorded current position (P) and the recorded current time and / or the recorded current calendar date. [10] Motor vehicle (1) with a driver assistance system (2) according to claim 9.

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