Method for characterizing objects in the surroundings of a motor vehicle

Abstract

The invention relates to a method (100) for characterizing an object in the surroundings of a motor vehicle by means of a motor vehicle assistance system, wherein the motor vehicle is moving relative to the object in question, and an ultrasonic signal is emitted by an ultrasonic sensor of the assistance system. Echoes of the ultrasonic signal reflected by the object are received at this time, wherein the respective amplitudes of the received echoes are determined by means of a control device, and a classification of the height of the object is determined on the basis of the amplitudes in question. According to the invention, the classification of the height of the object is determined on the basis of a first amplitude change determined by comparing a first amplitude of a first echo with a second amplitude of a second echo received after the first echo. Furthermore, the invention also discloses an assistance system comprising an ultrasonic sensor and a control device, which assistance system is designed to carry out such a method (100).

Description

Technical Field

[0001] This invention relates to a method for characterizing objects in the environment surrounding a motor vehicle using a vehicle assistance system, wherein the motor vehicle moves relative to the object and emits ultrasonic signals using an ultrasonic sensor of the assistance system. Simultaneously, echoes of the ultrasonic signals reflected from the object are received, and the corresponding amplitude of the received echoes is determined using a control device, wherein the object's height is classified based on the amplitude. Furthermore, the invention also relates to an assistance system comprising an ultrasonic sensor and a control device designed to perform such a method. Background Technology

[0002] Ultrasonic sensors typically include a transmitting device that emits ultrasonic signals that propagate through the air at a speed of approximately 340 meters per second. For this purpose, the ultrasonic sensor diaphragm is usually excited into mechanical vibration using a corresponding transducer. The ultrasonic signal is reflected as an echo by an object in the surrounding environment and detected by the receiving device of the ultrasonic sensor. Based on the time difference between the emission and reception times, and taking into account the propagation speed of the ultrasonic signal, the distance, or in other words, the distance to the object, can be determined. The amplitude of the reflected ultrasonic signal or echo can also be determined here.

[0003] Typically, ultrasonic sensors in motor vehicles are used to detect the surrounding environment up to approximately 7 meters away. Ultrasonic sensors play a particularly important role in semi-autonomous or autonomous driving operations, especially in parking applications such as parking distance measurement, parking space search, and parking maneuvers. In these situations, the motor vehicle typically moves relative to objects, and measurement cycles are performed at predetermined time points during the movement. In each measurement cycle, the ultrasonic sensor emits ultrasonic signals. Existing technology provides drivers with various information about the vehicle's surroundings using ultrasonic sensors, assisting them in maneuvering the vehicle, especially in locating a parking position and parking it in a parking space. For example, existing assistance systems are equipped with parking positioning devices that display to the driver whether there is a parking space in the immediate vicinity of the vehicle, or whether the existing parking space is large enough for the vehicle. For reliable positioning and measurement of parking positions, such assistance systems require information about objects in the vehicle's surroundings, such as the vehicle to be parked, curbs, sidewalls, and walls.

[0004] Besides the distance between the vehicle and the object, the height of the object is usually also important. Height is a crucial factor in determining whether it is permissible to drive over an object or obstacle. This is especially true when the vehicle is operating at least semi-automatically based on measurements from ultrasonic sensors; it is best to be able to determine the height of the detected object.

[0005] Due to physical limitations, one-dimensional (1D) ultrasonic sensors commonly used in the automotive field, specifically those for determining distance, face considerable difficulty in determining height. These sensors cannot directly measure the height of an object. Therefore, to determine height, an additional camera device must be used, and height estimation must be performed based on two-dimensional (2D) images, or a multi-sensor-based method must be employed to estimate height using triangulation. However, camera-based or multi-sensor-based methods lack the cost and robustness advantages of using one-dimensional (1D) ultrasonic sensors.

[0006] Methods and auxiliary systems of the above type are known, for example, in DE 10 2004 047 479 A1. Here, when a motor vehicle passes an object located to the side of the vehicle, an ultrasonic sensor of the vehicle transmits an ultrasonic signal, classifies the object's height, and receives the echo of the ultrasonic signal reflected by the object. Based on the amplitude of the received echo, the classification of the object's height is determined. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an alternative method for characterizing objects in the environment surrounding a motor vehicle, and an auxiliary system that can reliably classify the height of corresponding objects at the lowest possible cost.

[0008] In the following description, embodiments and other structural forms of the invention for the intended use are described.

[0009] In the method for characterizing objects in the environment surrounding a motor vehicle using a motor vehicle assistance system according to the present invention, the motor vehicle moves relative to a designated object, and ultrasonic signals are transmitted by an ultrasonic sensor of the assistance system, particularly a one-dimensional (1D) ultrasonic sensor. Simultaneously, echoes of ultrasonic signals reflected by the object are received, wherein the corresponding amplitude of the received echo is determined by means of a control device, and the object height is classified based on the amplitude.

[0010] According to the present invention, the classification of object height is determined by comparing the first amplitude of the first echo with the second amplitude of the second echo received after the first echo.

[0011] Here, the present invention is first based on the consideration that if a cost-effective classification of object height can be achieved using existing sensors in motor vehicles, and because no other sensors are used, or more precisely, no other types of sensors, especially cameras, are used, and there is no need for complex calculations and interference-prone fusion of the corresponding sensor data, this further promotes a particularly cost-effective and robust classification of object height. Furthermore, the present invention is based on the consideration that the radiation mode of an ultrasonic sensor is, in principle, an elevation angle function, meaning that the power of the ultrasonic signal emitted by the ultrasonic sensor towards an object within its detection range depends on the elevation angle. When an object is at a certain height, especially when its height is below the installation height of the ultrasonic sensor in the motor vehicle, and particularly below a certain distance between the object and the motor vehicle, or more precisely, the ultrasonic sensor, the elevation angle and the power of the reflected ultrasonic signal, or in other words, the amplitude of the reflected ultrasonic signal, will vary depending on the distance between the motor vehicle or ultrasonic sensor and the object. This fact can be used to determine the classification of object height.

[0012] Therefore, the present invention predefines the classification of object height based solely on sensor data from an ultrasonic sensor, particularly a one-dimensional (1D) ultrasonic sensor, which is used to measure the motion of an object. This classification is based on the change in first amplitude determined by comparing the first amplitude of the first echo with the second amplitude of the second echo received after the first echo.

[0013] According to the design scheme of the present invention, its advantage is that it provides a method that can reliably classify the height of relevant objects while being cost-effective.

[0014] The object to be represented can be an object that extends from the ground, such as the surface of a driveway or other terrain, and extends substantially orthogonally to the ground. It can also be an object that does not extend from the ground, such as the crossbar of a fence, or an object that does not extend orthogonally to the ground, such as a ramp.

[0015] Ultrasonic sensors, especially one-dimensional (1D) ultrasonic sensors, can be installed, for example, inside or behind a vehicle bumper. Alternatively, ultrasonic sensors, especially one-dimensional (1D) ultrasonic sensors, can be installed inside or behind body parts such as doors of a vehicle.

[0016] A single ultrasonic sensor, especially a one-dimensional (1D) ultrasonic sensor, can be used. Alternatively, multiple ultrasonic sensors, especially multiple one-dimensional (1D) ultrasonic sensors, can also be used.

[0017] In a preferred embodiment, the first echo and the second echo are echoes that occur sequentially in time.

[0018] Specifically, the categories "high" and "low" are used to classify object height. If an object is at least at the installation height of the ultrasonic sensor, meaning its height at least corresponds to the installation height of the ultrasonic sensor, then the object is classified as "high." If an object is below the installation height of the ultrasonic sensor, especially if its height is lower than the installation height of the ultrasonic sensor, then the object is classified as "low."

[0019] In another advantageous embodiment, the object is located in the vicinity of the motor vehicle, preferably within two meters of the vehicle's ultrasonic sensor. When the motor vehicle approaches the object, if a decrease in amplitude over time is determined as a first amplitude change, the object is classified as short; if an increase in amplitude over time is determined as a first amplitude change, the object is classified as tall. In this case, objects below the installation height of the ultrasonic sensor, i.e., objects whose height is lower than the installation height of the ultrasonic sensor, are classified as short. For example, curb stones are such objects. Objects at least at the installation height of the ultrasonic sensor, i.e., objects whose height at least corresponds to the installation height of the ultrasonic sensor, are classified as tall. For example, walls, fences, or vehicles are such objects.

[0020] This is based on the fact that for objects at least at the installation height of the ultrasonic sensor, the elevation angle does not change as a vehicle or ultrasonic sensor moves toward the object. Therefore, the power of the reflected ultrasonic signal or echo, or in other words, the amplitude of the reflected ultrasonic signal or echo, depends only on the distance between the object and the ultrasonic sensor. In this case, the amplitude of the reflected ultrasonic signal increases as the vehicle, or more precisely, as the ultrasonic sensor approaches such an object—that is, as the distance between the object and the ultrasonic sensor decreases. Conversely, for objects below the installation height of the ultrasonic sensor, within a defined distance between the object and the ultrasonic sensor, the elevation angle changes and decreases as a vehicle or ultrasonic sensor moves toward the object. In this case, the amplitude of the reflected ultrasonic signal decreases as the vehicle or ultrasonic sensor approaches such an object. Moreover, the amplitude increases as the distance between the object and the ultrasonic sensor decreases. In contrast, the dominant factor here is that the elevation angle decreases with decreasing distance, thus reducing the overall amplitude of the reflected ultrasonic signal.

[0021] In another advantageous embodiment, the classification of object height is determined based on a comparison of a first amplitude change and a second amplitude change. The second amplitude change is determined by comparing the third amplitude of the third echo received after the second echo with the second amplitude of the second echo, or by comparing it with the fourth amplitude of the fourth echo received after the second echo and before the third echo. Comparing the two amplitude changes here further improves the robustness of the object height classification.

[0022] Meanwhile, in another advantageous embodiment, when a motor vehicle approaches a relevant object, if an increase in amplitude over time is determined to be a first amplitude change, and a decrease in amplitude over time is determined to be a second amplitude change, then the object is classified as short.

[0023] It is based on the fact that objects such as curbs, located below the installation height of ultrasonic sensors, especially those whose height is lower than the installation height of the ultrasonic sensors, preferably at a distance of more than two meters from the ultrasonic sensors of motor vehicles, have an elevation angle of at least approximately 90 degrees, provided that the object is not yet within close proximity to a motor vehicle. In this case, the power of the reflected ultrasonic signal, or in other words, the amplitude of the reflected ultrasonic signal, depends primarily on the distance between the object and the ultrasonic sensor. If the motor vehicle or ultrasonic sensor approaches such an object, i.e., the distance between the object and the ultrasonic sensor decreases, the amplitude of the reflected ultrasonic signal or echo will initially increase. This initial amplitude change results in an increase in amplitude over time. If the motor vehicle or ultrasonic sensor continues to approach the object, and the object is particularly within close proximity to the motor vehicle, preferably less than two meters from the ultrasonic sensor, the elevation angle changes as the vehicle or ultrasonic sensor further approaches the object, where the elevation angle becomes less than 90 degrees and gradually decreases as the vehicle or ultrasonic sensor approaches the object further or the distance between the vehicle or ultrasonic sensor and the object further decreases. This causes the amplitude of the reflected ultrasonic signal to gradually decrease as the vehicle or ultrasonic sensor gets closer to the object. More precisely, the amplitude increases as the distance between the object and the ultrasonic sensor decreases. Conversely, the dominant factor here is that the elevation angle decreases with decreasing distance, thus reducing the overall amplitude of the reflected ultrasonic signal. Here, the second amplitude change causes the amplitude to decrease over time. If, based on a comparison of the first and second amplitude changes, the increase in amplitude over time is determined to be the first amplitude change, and the decrease in amplitude over time is determined to be the second amplitude change, then the object is classified as short.

[0024] In another advantageous embodiment, the relevant object is located in the vicinity of the motor vehicle, preferably at most two meters away from the ultrasonic sensor of the motor vehicle. When the motor vehicle approaches the relevant object, if a corresponding decrease in amplitude over time is determined as a first amplitude change and a second amplitude change, and if the second amplitude change is greater than the first amplitude change, the relevant object is classified as short. A measure of amplitude decrease is taken into consideration here.

[0025] It is based on the fact that in objects such as curbs, which are below the installation height of ultrasonic sensors—especially those whose height is lower than the installation height of ultrasonic sensors—if the object is in the vicinity of a motor vehicle, preferably less than two meters from the ultrasonic sensor, the elevation angle gradually decreases as the vehicle or ultrasonic sensor moves further towards the object. This results in a gradual decrease in the amplitude of the reflected ultrasonic signal or echo as the vehicle or ultrasonic sensor approaches the object. Moreover, the amplitude increases as the distance between the object and the ultrasonic sensor decreases. In contrast, the dominant factor here is that the elevation angle decreases with decreasing distance, thus reducing the overall amplitude of the reflected ultrasonic signal. Here, the second amplitude change causes a decrease in amplitude over time, and the decrease in amplitude over time caused by the second amplitude change is greater than the decrease in amplitude caused by the first amplitude change; therefore, the object is classified as short.

[0026] In another advantageous embodiment, the relevant object is located in the vicinity of the motor vehicle, preferably at most two meters away from the ultrasonic sensor of the motor vehicle. When the motor vehicle approaches the relevant object, if a corresponding increase in amplitude over time is determined as a first amplitude change and a second amplitude change, and if the second amplitude change is greater than the first amplitude change, the relevant object is classified as high. A measure of amplitude decrease is also considered here.

[0027] It is based on the fact that when an object, such as a wall, fence, or vehicle, is at least at the installation height of the ultrasonic sensor, and especially when its height is at least equal to the installation height of the ultrasonic sensor, is within close range of a motor vehicle, preferably less than two meters from the ultrasonic sensor, the elevation angle will not change as the motor vehicle or ultrasonic sensor moves toward the object. Therefore, the power of the reflected ultrasonic signal, or more precisely, the amplitude of the reflected ultrasonic signal, depends only on the distance between the object and the ultrasonic sensor. Here, when the motor vehicle or ultrasonic sensor approaches such an object, i.e., when the distance between the object and the ultrasonic sensor decreases, the amplitude of the reflected ultrasonic signal or echo increases. Here, the second amplitude change leads to an increase in amplitude over time, and this increase in amplitude over time due to the second amplitude change is greater than the increase in amplitude due to the first amplitude change; thus, the object is classified as high.

[0028] In another advantageous embodiment, if the magnitude of the first amplitude change is also higher than a predetermined threshold in terms of value, then the object height classification is determined. This further improves the reliability of determining the object height classification. In another embodiment, where a second amplitude change is considered as an additional measure or alternative, if, as an additional measure or alternative, the second amplitude change is higher than a predetermined threshold in terms of value, then the object height classification is preferably determined.

[0029] In another advantageous implementation, the relevant threshold is predetermined based on the vehicle's current speed and / or the temperature and / or humidity in the vehicle's surrounding environment and / or the installation height of the ultrasonic sensors on the vehicle. Since temperature and the ambient temperature significantly affect sound attenuation in the air, temperature can be detected using appropriate sensors, and the threshold can be adjusted accordingly. The same applies to humidity. This results in more reliable classification of object height.

[0030] In another advantageous implementation, the comparison of amplitudes is based on the difference and / or ratio of amplitudes.

[0031] In another advantageous implementation, the comparison of amplitude changes is based on the difference and / or ratio of amplitude changes.

[0032] In another advantageous embodiment, the relevant method is applied to assisted parking methods and / or semi-automatic parking methods and / or automatic parking methods.

[0033] In another advantageous implementation, the classification of object height is based solely on sensor data from an ultrasonic sensor. Therefore, it is particularly unnecessary to use other types of sensors, such as cameras or radar sensors, to determine the height classification.

[0034] Furthermore, the present invention also includes an auxiliary system with an ultrasonic sensor and a control device. Here, the control device is configured to implement the method according to the present invention.

[0035] The advantages and various preferred embodiments described in the method according to the present invention are also applicable to the auxiliary system according to the present invention. Attached Figure Description

[0036] The invention will now be described in detail with reference to the accompanying drawings. Wherein:

[0037] Figure 1 The radiation diagram is shown, which illustrates the radiation pattern of the ultrasonic sensor according to the elevation angle.

[0038] Figure 2 Showing the elevation angle and according to Figure 1 The graph shows the functional relationship between the ultrasonic sensor and the object.

[0039] Figure 3 A flowchart of a method for characterizing objects in the environment surrounding a motor vehicle is shown.

[0040] The same reference numerals are used for the corresponding parts in all figures. Detailed Implementation

[0041] Figure 1 The diagram shows the radiation pattern 1 of the ultrasonic sensor, which is determined by the elevation angle. It can be seen that the radiation pattern 1 of the ultrasonic sensor is an elevation angle function, meaning that the power of the ultrasonic signal emitted by the ultrasonic sensor towards the object within its detection range depends on the elevation angle.

[0042] If the object is at a 90-degree elevation angle, that is, at least within the installation height of the ultrasonic sensor inside the vehicle, then as the vehicle, and more precisely, as the ultrasonic sensor approaches the object, the elevation angle remains constant. The reflected ultrasonic signal, or echo power, or in other words, the amplitude of the reflected ultrasonic signal or echo, depends only on the distance between the ultrasonic sensor and the object. Therefore, if the vehicle or ultrasonic sensor approaches a taller object, the amplitude of the reflected ultrasonic signal gradually increases.

[0043] For objects whose height is lower than the installation height of the ultrasonic sensor inside the vehicle, the elevation angle and the power or amplitude of the reflected ultrasonic signal will change depending on the distance between the vehicle or ultrasonic sensor and the object. As the vehicle or ultrasonic sensor approaches the object, the elevation angle gradually decreases, reaching approximately 0 degrees when the ultrasonic sensor is directly next to the object.

[0044] Figure 2 Showing the elevation angle as a basis Figure 1 The graph shows the distance function between the ultrasonic sensor and the object. Here, the height of the object is 40 cm lower than the installation height of the ultrasonic sensor in the motor vehicle. The object in this case is a curbstone.

[0045] As shown in the diagram, when an object is not yet within close range of a motor vehicle, especially when it is more than two meters away from the ultrasonic sensor, the elevation angle is approximately 90 degrees. Therefore, in this region, the power of the reflected ultrasonic signal, or more precisely, the amplitude of the reflected ultrasonic signal, depends primarily on the distance between the object and the ultrasonic sensor. If the motor vehicle or ultrasonic sensor approaches the object, i.e., if the distance between the object and the ultrasonic sensor decreases, the amplitude of the reflected ultrasonic signal will increase.

[0046] If the vehicle or ultrasonic sensor moves closer to the object, and the object is within close range of the vehicle, especially within two meters of the ultrasonic sensor, the elevation angle will gradually decrease as the vehicle or sensor approaches the object. This results in a gradual decrease in the amplitude of the reflected ultrasonic signal as the vehicle or sensor gets closer to the object. Furthermore, the amplitude increases as the distance between the object and the ultrasonic sensor decreases. In contrast, the dominant factor here is that the elevation angle decreases with decreasing distance, thus reducing the overall amplitude of the reflected ultrasonic signal.

[0047] Figure 3 This is a flowchart of a method 100 for characterizing objects in the environment surrounding a motor vehicle. Here, the relevant motor vehicle includes an auxiliary system with control devices and a one-dimensional (1D) ultrasonic sensor, which is mounted on the front bumper of the motor vehicle and has features such as... Figure 1 The radiation pattern is shown. Here, the front of the vehicle continues to approach the object from a distance of approximately 2.5 meters, while the ultrasonic sensor continuously sends ultrasonic signals. The object is a curbstone, and its height is approximately 40 centimeters lower than the installation height of the ultrasonic sensor in the vehicle.

[0048] In step 101, the first echo is received and the first amplitude of the first echo is determined.

[0049] In the subsequent step 102, the second echo that follows the first echo in time is received, and the second amplitude of the second echo is determined.

[0050] In step 103, the change in the first amplitude is determined by comparing the first amplitude and the second amplitude. Simultaneously, an increase in amplitude is determined in this case. Since the object is not yet within close range of the vehicle at the measurement time, i.e., more than two meters away from the ultrasonic sensor, the elevation angle is approximately 90 degrees. At this point, the power of the reflected ultrasonic signal, or more precisely, the amplitude of the reflected ultrasonic signal, depends primarily on the distance between the object and the ultrasonic sensor. If the vehicle or ultrasonic sensor approaches such an object, i.e., the distance between the object and the ultrasonic sensor decreases, the amplitude of the reflected ultrasonic signal will increase. Here, the first amplitude change leads to an increase in amplitude over time.

[0051] Since the object was not yet within close range of the vehicle at the measurement time, the final classification of the object's height based on the determined amplitude change has not yet been performed, and method 100 returns to step 102. Therefore, the third echo, which follows the second echo in time, is received, and the third amplitude of the third echo is determined.

[0052] Then, in step 103, the change in the second amplitude is determined by comparing the second and third amplitudes. Since the vehicle moves further toward the object during this period, and at the point of further measurement, the object is within close range of the vehicle—specifically, 0.5 meters from the vehicle or the ultrasonic sensor—the amplitude decrease is determined as the second amplitude change. This is based on the fact that the elevation angle in this region is significantly less than 90 degrees, which causes an overall reduction in the amplitude of the reflected ultrasonic signal, thus the third amplitude of the third echo is less than the second amplitude of the second echo. Here, the second amplitude change leads to a decrease in amplitude over time.

[0053] In step 104, the classification of the object's height is determined. For this, the first amplitude change is compared with the second amplitude change. Since, in this case, an increase in amplitude over time is determined as the first amplitude change, and a decrease in amplitude over time is determined as the second amplitude change, the relevant object is classified as short.

[0054] Based on this method 100, the height of objects can be classified in a cost-effective and reliable manner, in this case referring to the classification of the height of relevant curb stones.

Claims

1. A method (100) for characterizing objects in the environment surrounding a motor vehicle using a motor vehicle assistance system, wherein, A motor vehicle moves relative to the object and continuously transmits ultrasonic signals using an ultrasonic sensor of an auxiliary system, wherein echoes of ultrasonic signals reflected by the object are received, wherein the corresponding amplitude of the received echoes is determined by means of a control device, and a classification of the object's height is determined based on the amplitude, characterized in that the classification of the object's height is determined based on a change in a first amplitude determined by comparing the first amplitude of the first echo of the first reflected ultrasonic signal with the second amplitude of the second echo of the second reflected ultrasonic signal received after the first echo, the classification of the object's height is determined based on a comparison of the change in the first amplitude with the change in the second amplitude, the change in the second amplitude being determined by comparing the third amplitude of the third echo of the third reflected ultrasonic signal received after the second echo with the second amplitude of the second echo, or with the fourth amplitude of the fourth echo of the fourth reflected ultrasonic signal received after the second echo and before the third echo.

2. The method (100) according to claim 1, characterized in that, The first and second echoes are sequential echoes in time.

3. The method (100) according to claim 1 or 2, characterized in that, The object is within two meters of the ultrasonic sensor of the motor vehicle. When the motor vehicle approaches the object, if a decrease in amplitude over time is determined as the first amplitude change, the object is classified as short; if an increase in amplitude over time is determined as the first amplitude change, the object is classified as tall.

4. The method (100) according to claim 1, characterized in that, When a motor vehicle approaches an object, if an increase in amplitude over time is identified as a first amplitude change, and a decrease in amplitude over time is identified as a second amplitude change, then the object is classified as short.

5. The method (100) according to claim 1, characterized in that, When an object is within two meters of the ultrasonic sensor of a motor vehicle, if the corresponding decrease in amplitude over time is determined as a first amplitude change and a second amplitude change when the motor vehicle approaches the object, and if the second amplitude change is greater than the first amplitude change, the object is classified as short.

6. The method (100) according to claim 1, characterized in that, When an object is within two meters of the ultrasonic sensor of a motor vehicle, if the corresponding increase in amplitude over time is determined as a first amplitude change and a second amplitude change when the motor vehicle approaches the object, and if the second amplitude change is greater than the first amplitude change, the object is classified as high.

7. The method (100) according to claim 1 or 2, characterized in that, If the first amplitude change is numerically higher than a predetermined threshold, the object height is classified.

8. The method (100) according to claim 7, characterized in that, The threshold is predetermined based on the current speed of the vehicle and / or the temperature and / or the air humidity in the environment surrounding the vehicle and / or the installation height of the ultrasonic sensor of the vehicle.

9. The method (100) according to claim 1 or 2, characterized in that, The comparison of amplitudes is based on the difference and / or ratio of amplitudes.

10. The method (100) according to claim 1, characterized in that, Comparison of amplitude changes is based on the differences and / or ratios of amplitude changes.

11. The method (100) according to any of the preceding claims, characterized in that, The method is applied to assisted parking methods and / or semi-automatic parking methods and / or automatic parking methods.

12. The method (100) according to any one of the preceding claims, characterized in that, The classification of object height is based solely on sensor data from ultrasonic sensors.

13. An auxiliary system comprising an ultrasonic sensor and a control device, the auxiliary system being designed to perform the method (100) according to any of the preceding claims.

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