METHOD FOR CHARACTERIZING AN OBJECT IN THE ENVIRONMENT OF A MOTOR VEHICLE

Description

[0001] The invention relates to a method for characterizing an object in the environment of a motor vehicle by means of a vehicle assistance system, in which the motor vehicle is moved relative to the object and ultrasonic signals are emitted by an ultrasonic sensor of the assistance system. Echoes of the ultrasonic signals reflected by the object are received, and the respective amplitudes of the received echoes are determined by means of a control unit, whereby a classification of the object's height is determined based on the amplitudes. The invention further relates to an assistance system with an ultrasonic sensor and a control unit designed to carry out such a method.

[0002] Ultrasonic sensors typically comprise a transmitter that emits ultrasonic signals which propagate through air at the speed of sound, approximately 340 meters per second. This is usually achieved by exciting a diaphragm within the ultrasonic sensor, which is then mechanically vibrated by a transducer element. The ultrasonic signal is reflected as an echo by objects in the vicinity and detected by a receiver within the ultrasonic sensor. Based on the time difference between the transmission and reception times, and taking into account the propagation speed of the ultrasonic signal, the distance to the object can be determined. The amplitude of the reflected ultrasonic signal, or echo, can also be calculated.

[0003] Ultrasonic sensors are typically used in motor vehicles for environmental sensing within a range of up to approximately 7 meters. They are particularly important for semi-automatic or automatic driving maneuvers, especially in parking applications such as parking distance measurement, parking space search, and parking maneuvers. In these applications, the vehicle is usually moved relative to the objects, with a measurement cycle being performed at predetermined intervals during this movement. During each measurement cycle, an ultrasonic signal is emitted by the sensor.Methods and corresponding assistance systems are already known from the prior art that use ultrasonic sensors to provide the driver with various pieces of information about the vehicle's surroundings, supporting the driver in maneuvering the vehicle and, in particular, in locating and parking the vehicle. For example, assistance systems exist that are equipped with parking space localization and indicate to the driver whether a parking space is available in the immediate vicinity of the vehicle, or whether an existing parking space is large enough to accommodate the vehicle. Such assistance systems require information about objects in the vehicle's vicinity for the reliable localization and measurement of a parking space. These objects can include parked vehicles, curbs, walls, and fences.

[0004] In addition to the distance of the vehicle to an object, the object's height is usually also important. Height is a crucial factor in determining whether an object or obstacle can be driven over. Especially when the vehicle is maneuvered at least semi-autonomously based on measurements from an ultrasonic sensor, it is desirable to determine the height of the detected object.

[0005] Determining height using the one-dimensional (1D) ultrasonic sensors commonly used in the automotive sector, i.e., ultrasonic sensors for distance measurement, is inherently quite difficult due to physical limitations. Such an ultrasonic sensor cannot directly measure the height of an object. Therefore, height determination is achieved, for example, by using an additional camera and estimating the height based on a 2D image, or by employing a multi-sensor method for estimating the height using triangulation. However, methods based on a single camera or multiple sensors do not utilize the advantages of a 1D ultrasonic sensor in terms of cost and robustness.

[0006] A method and an assistance system of the type mentioned above are known, for example, from DE 10 2004 047 479 A1. In this method, to classify the height of an object as a motor vehicle passes an object located to the side of the vehicle, ultrasonic signals are emitted by means of an ultrasonic sensor on the motor vehicle, and the echoes of the ultrasonic signals reflected by the objects are received. The classification of the object's height is determined based on the amplitude of a received echo. DE 10 2018 102 786 A1, DE 10 2005 044 050 A1, and DE 10 2018 103 560 A1 relate to the classification of the height of objects in the vicinity of a vehicle using ultrasonic sensors. US 2008 / 111733 A1 describes a radar for detecting low objects.

[0007] The present invention is based on the objective of providing an alternative method for characterizing an object in the environment of a motor vehicle and a corresponding assistance system which enables the most cost-effective and reliable classification of the object's height.

[0008] The foregoing problem is solved by the entire teaching of claim 1 and dependent claim 13. Advantageous embodiments and further developments of the invention are set forth in the dependent claims and the following description.

[0009] In the inventive method for characterizing an object in the environment of a motor vehicle by means of a motor vehicle assistance system, the motor vehicle is moved relative to the object, and ultrasonic signals are emitted by an ultrasonic sensor, in particular a 1D ultrasonic sensor, of the assistance system. Echoes of the ultrasonic signals reflected by the object are received, the respective amplitudes of the received echoes are determined by means of a control unit, and a classification of the object's height is determined based on the amplitudes.

[0010] According to the invention, the classification of the object's height is determined based on a first amplitude change by comparing the first amplitude of a first echo with the second amplitude of a second echo received after the first echo. Furthermore, according to the invention, the classification of the object's height is determined by comparing the first amplitude change with a second amplitude change, wherein the second amplitude change is determined by comparing the third amplitude of a third echo received after the second echo with the second amplitude of the second echo or with the fourth amplitude of a fourth echo received after the second echo and before the third echo.

[0011] The invention is based on the premise that cost-effective classification of an object's height is possible by utilizing a sensor already installed in the vehicle. Furthermore, this cost-effective and robust classification is enhanced by eliminating the need for an additional sensor, or more precisely, an additional sensor type, particularly a camera, and the associated computationally intensive and error-prone fusion of the corresponding sensor data. The invention is further based on the premise that the radiation pattern of an ultrasonic sensor is fundamentally a function of the elevation angle; that is, the power of an ultrasonic signal emitted by an ultrasonic sensor to an object within its detection range depends on the elevation angle.For an object located at a height lower than the installation height of the ultrasonic sensor in the vehicle, the elevation angle, and therefore the power (or in other words, the amplitude of the reflected ultrasonic signal), changes depending on the distance between the object and the vehicle (or more precisely, the ultrasonic sensor), particularly below a certain distance. This fact can be used to determine the height classification of an object.

[0012] Therefore, the invention provides that the classification of the height of the object is determined solely based on the sensor data of an ultrasonic sensor moving relative to the object, in particular a 1D ultrasonic sensor, by means of a determined first amplitude change by comparing a first amplitude of a first echo with a second amplitude of a second echo received after the first echo.

[0013] The embodiment according to the invention has the advantage that it provides a method by which a cost-effective and reliable classification of the height of the object is made possible.

[0014] The objects to be characterized can be objects that extend from a ground, such as a road surface or other terrain, and are essentially perpendicular to the ground. However, they can also be objects that do not extend from the ground, such as a fence rail, or that are not perpendicular to the ground, such as a ramp.

[0015] The ultrasonic sensor, in particular a 1D ultrasonic sensor, can be arranged, for example, in or behind a bumper of the motor vehicle. Alternatively, the ultrasonic sensor, in particular a 1D ultrasonic sensor, can be arranged in or behind a body component, for example, a door of the motor vehicle.

[0016] Either a single ultrasonic sensor, in particular a 1D ultrasonic sensor, can be used, or multiple ultrasonic sensors, in particular multiple 1D ultrasonic sensors, can be used.

[0017] In an advantageous embodiment, the first echo and the second echo are successive echoes.

[0018] The two classifications used to categorize the object's height are "high" and "low." An object is classified as "high" if it is at least at the installation height of the ultrasonic sensor, meaning it has a height that is at least equal to the sensor's installation height. An object is classified as "low" if it is below the installation height of the ultrasonic sensor, meaning it has a height that is less than the sensor's installation height.

[0019] In a further advantageous embodiment, the object is located in the immediate vicinity of the motor vehicle, preferably at a distance of up to two meters from the vehicle's ultrasonic sensor. As the motor vehicle approaches the object, the object is classified as low if the first amplitude change is a decrease over time, and as high if the first amplitude change is an increase over time. The low classification is determined particularly for an object that is located below the installation height of the ultrasonic sensor, i.e., one that has a height less than the installation height of the ultrasonic sensor. A curb, for example, is such an object.The classification as "high" is determined specifically for an object that is located at least at the installation height of the ultrasonic sensor, i.e., that has a height at least equal to the installation height of the ultrasonic sensor. Such an object could be, for example, a wall, a fence, or a vehicle.

[0020] This is based on the fact that for an object located at least at the installation height of the ultrasonic sensor, the elevation angle does not change as the vehicle or the ultrasonic sensor moves towards the object. Therefore, the power, or in other words, the amplitude of the reflected ultrasonic signal or echo, depends solely on the distance between the object and the ultrasonic sensor. The amplitude of the reflected ultrasonic signal increases as the vehicle, or more precisely, the ultrasonic sensor, approaches such an object, i.e., as the distance between the object and the ultrasonic sensor decreases. Conversely, for an object located below the installation height of the ultrasonic sensor, the elevation angle changes below a certain distance between the object and the ultrasonic sensor and decreases continuously as the vehicle or the ultrasonic sensor moves towards the object.The amplitude of the reflected ultrasound signal decreases as the vehicle or ultrasound sensor approaches such an object. While the amplitude generally increases as the distance between the object and the ultrasound sensor decreases, the dominant factor here is that the elevation angle decreases with decreasing distance, consequently reducing the overall amplitude of the reflected ultrasound signal.

[0021] According to the invention, two amplitude changes are compared, thereby further promoting the robustness of the classification of the object's height.

[0022] In a further advantageous embodiment, when the motor vehicle approaches the object, the object is classified as low if the first amplitude change is an increase in amplitude over time and the second amplitude change is a decrease in amplitude over time.

[0023] This is based on the fact that for an object, such as a curb, located below the installation height of the ultrasonic sensor—that is, one that has a height less than the sensor's installation height—and especially when this object is not yet in close proximity to the vehicle, preferably at a distance greater than two meters from the vehicle's ultrasonic sensor, the elevation angle is at least approximately 90°. Consequently, the power, or in other words, the amplitude of the reflected ultrasonic signal, depends essentially only on the distance between the object and the ultrasonic sensor. The amplitude of the reflected ultrasonic signal or echo initially increases as the vehicle or the ultrasonic sensor approaches such an object, i.e., as the distance between the object and the ultrasonic sensor decreases.The initial amplitude change thus results in an increase in amplitude over time. As the vehicle or the ultrasonic sensor approaches the object, and the object is then in close proximity to the vehicle, preferably at a distance of less than two meters from the vehicle's ultrasonic sensor, the elevation angle changes with further approach, becoming less than 90° and decreasing progressively with further approach or reduction in distance. This leads to a progressive decrease in the amplitude of the reflected ultrasonic signal as the distance decreases. While the amplitude generally increases as the distance between the object and the ultrasonic sensor decreases, the dominant factor here is that the elevation angle decreases with decreasing distance, consequently reducing the overall amplitude of the reflected ultrasonic signal.The second amplitude change therefore results in a decrease in amplitude over time. If, based on a comparison of the first and second amplitude changes, the first amplitude change shows an increase over time and the second amplitude change shows a decrease over time, then the object is classified as low.

[0024] In a further advantageous embodiment, the object is located in the immediate vicinity of the motor vehicle, preferably at a distance of up to two meters from the vehicle's ultrasonic sensor. When the motor vehicle approaches the object, the object is classified as having a low amplitude if both the first and second amplitude changes show a decrease in amplitude over time, and if, in addition, the second amplitude change is greater than the first. Thus, a measure of amplitude decrease is taken into account.

[0025] This is based on the fact that when an object, such as a curb, is located below the installation height of the ultrasonic sensor—that is, when the object is in close proximity to the vehicle, preferably at a distance of less than two meters from the vehicle's ultrasonic sensor—the elevation angle gradually decreases as the vehicle or the ultrasonic sensor moves closer to the object. This results in a gradual decrease in the amplitude of the reflected ultrasonic signal or echo as the object approaches. While the amplitude generally increases as the distance between the object and the ultrasonic sensor decreases, the dominant factor here is that the elevation angle decreases with decreasing distance, consequently reducing the overall amplitude of the reflected ultrasonic signal.The second amplitude change therefore results in a decrease in amplitude over time, which is greater than the decrease in amplitude of the first amplitude change, thus classifying the object as low.

[0026] In a further advantageous embodiment, the object is located in the immediate vicinity of the motor vehicle, preferably at a distance of up to two meters from the vehicle's ultrasonic sensor. When the motor vehicle approaches the object, the object is classified as high-level if both the first and second amplitude changes show an increase in amplitude over time, and if, in addition, the second amplitude change is greater than the first. Thus, a measure of amplitude increase is taken into account.

[0027] This is based on the fact that for an object, such as a wall, fence, or vehicle, located at least at the installation height of the ultrasonic sensor—that is, in particular, having a height at least equal to the installation height of the ultrasonic sensor—even if this object is in close proximity to the vehicle, preferably at a distance of less than two meters from the vehicle's ultrasonic sensor, the angle of elevation does not change as the vehicle or ultrasonic sensor moves toward the object. Thus, the power, or more precisely, the amplitude of the reflected ultrasonic signal depends solely on the distance between the object and the ultrasonic sensor. The amplitude of the reflected ultrasonic signal or echo increases as the vehicle or ultrasonic sensor approaches such an object, i.e., as the distance between the object and the ultrasonic sensor decreases.The second amplitude change therefore results in an increase in amplitude over time that is greater than the increase in amplitude of the first amplitude change, which classifies the object as high.

[0028] In a further advantageous embodiment, the height classification of the object is determined if, in addition, the first amplitude change exceeds a predetermined threshold. This further increases the reliability of determining the object's height classification. In an embodiment that additionally or alternatively considers the second amplitude change, the height classification of the object is preferably determined if, in addition or alternatively, the second amplitude change exceeds a predetermined threshold.

[0029] In a further advantageous embodiment, the threshold is predetermined depending on the current speed of the vehicle and / or the temperature in the vehicle's environment and / or the humidity in the vehicle's environment and / or the installation height of the ultrasonic sensor on the vehicle. Since the temperature in the vehicle's environment has a significant impact on airborne sound attenuation, the temperature can be measured using a suitable sensor and the threshold adjusted accordingly. The same applies to humidity. This leads to an even more reliable classification of the object's height.

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

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

[0032] In a further advantageous embodiment, the method is applied in an assisted and / or semi-automatic and / or automatic parking procedure.

[0033] In a further advantageous embodiment, the classification of the object's height is based solely on sensor data from the ultrasonic sensor. In particular, no other type of sensor, such as a camera or radar sensor, is used to determine the height classification.

[0034] Furthermore, the present invention comprises an assistance system with an ultrasonic sensor and a control unit. The control unit is designed to carry out the method according to the invention.

[0035] The advantages and preferred embodiments described for the method according to the invention also apply accordingly to the assistance system according to the invention.

[0036] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 is a radiation diagram showing the radiation pattern of an ultrasonic sensor as a function of the altitude angle; Fig. 2 is a diagram showing the altitude angle as a function of the distance of the ultrasonic sensor according to Fig. 1 of an object, and Fig. 3 a flowchart of a method for characterizing an object in the environment of a motor vehicle.

[0037] Corresponding parts in all figures are always marked with the same reference symbols.

[0038] In Fig. 1 A radiation diagram is shown, representing the radiation pattern 1 of an ultrasonic sensor as a function of the elevation angle. It can be seen that the radiation pattern 1 of the ultrasonic sensor is a function of the elevation angle, meaning that the power of an ultrasonic signal emitted by an ultrasonic sensor towards an object in the detection range depends on the elevation angle.

[0039] If an object is at an angle of 90° to the ground, meaning at least at the installation height of the ultrasonic sensor in a motor vehicle, then the angle of elevation does not change as the motor vehicle, or more precisely, the ultrasonic sensor, approaches the object. The 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, the amplitude of the reflected ultrasonic signal increases progressively as the motor vehicle, or rather the ultrasonic sensor, approaches a taller object.

[0040] For an object that is lower than the installation height of the ultrasonic sensor in the vehicle, the elevation angle, and therefore the power or amplitude of the reflected ultrasonic signal, changes depending on the distance between the vehicle / ultrasonic sensor and the object. As the vehicle / ultrasonic sensor approaches the object, the elevation angle gradually decreases until it reaches approximately 0° as soon as the ultrasonic sensor is in close proximity to the object.

[0041] Fig. 2 shows a diagram that plots the elevation angle as a function of the distance of the ultrasonic sensor according to Fig. 1 The image depicts an object. This object has a height that is 40 cm lower than the installation height of the ultrasonic sensor in the vehicle. Here, the object is represented as a curb.

[0042] The diagram shows that when the object is not yet in close proximity to the vehicle, particularly at a distance greater than two meters from the vehicle's ultrasonic sensor, the elevation angle is approximately 90°. In this range, the power, or more precisely, the amplitude of the reflected ultrasonic signal, depends essentially only on the distance between the object and the ultrasonic sensor. The amplitude of the reflected ultrasonic signal increases as the vehicle or the ultrasonic sensor approaches such an object, i.e., as the distance between the object and the ultrasonic sensor decreases.

[0043] As the vehicle or the ultrasonic sensor approaches the object, and the object is then in the vehicle's immediate vicinity, particularly at a distance of less than two meters from the vehicle's ultrasonic sensor, the elevation angle decreases noticeably with increasing proximity. This results in a progressive decrease in the amplitude of the reflected ultrasonic signal. While the amplitude generally increases as the distance between the object and the ultrasonic sensor decreases, the dominant factor here is that the elevation angle decreases with decreasing distance, consequently reducing the overall amplitude of the reflected ultrasonic signal.

[0044] Fig. 3 A flowchart of a method 100 for characterizing an object in the environment of a motor vehicle. The motor vehicle comprises an assistance system with a control unit and a 1D ultrasonic sensor, which is arranged on a front bumper of the motor vehicle and which emits a radiation pattern according to Fig. 1 The vehicle approaches the object from a distance of approximately 2.5 meters, with its front end moving closer, while the ultrasonic sensor continuously emits ultrasonic signals. The object is a curb, which is approximately 40 cm lower than the installation height of the ultrasonic sensor in the vehicle.

[0045] In step 101, a first echo is received and the first amplitude of the first echo is determined.

[0046] In a subsequent step 102, a second echo following the first echo in time is received and a second amplitude of the second echo is determined.

[0047] In step 103, an initial change in amplitude is determined by comparing the first amplitude with the second amplitude. In this case, an increase in amplitude is observed. Since the object is not yet in close proximity to the vehicle at the time of measurement, i.e., still at a distance greater than two meters from the vehicle's ultrasonic sensor, the elevation angle is approximately 90°. Consequently, the power, or more precisely, the amplitude of the reflected ultrasonic signal depends essentially only on the distance between the object and the ultrasonic sensor. The amplitude of the reflected ultrasonic signal thus increases as the vehicle or the ultrasonic sensor approaches such an object, i.e., as the distance to the object and the ultrasonic sensor decreases. The initial change in amplitude therefore results in an increase in amplitude over time.

[0048] Since the object was not yet in close proximity to the vehicle at the time of measurement, no final classification of the object's height takes place based on the determined amplitude change, and procedure 100 returns to step 102. Thus, a third echo, following the second echo in time, is received, and a third amplitude of the third echo is determined.

[0049] Subsequently, in step 103, a second amplitude change is determined by comparing the second amplitude with the third amplitude. Since the vehicle has moved further towards the object in the meantime, and the object is now in close proximity to the vehicle at the time of the next measurement—specifically, at a distance of 0.5 meters from the vehicle or ultrasonic sensor—the second amplitude change is determined to be a decrease in amplitude. This is because the elevation angle in this area is now significantly less than 90°, which results in a decrease in the overall amplitude of the reflected ultrasonic signal. Consequently, the third amplitude of the third echo is smaller than the second amplitude of the second echo. Therefore, the second amplitude change here results in a decrease in amplitude over time.

[0050] In step 104, the object's height is classified. This involves comparing the first and second amplitude changes. Since the first amplitude change is an increase over time and the second is a decrease over time, the object is classified as low.

[0051] Based on this method 100, the height of the object, in this case the curb, can be classified in a cost-effective and reliable manner.

Claims

1. A method (100) for characterising an object in an environment of a motor vehicle by means of an assistance system of the motor vehicle, in which the motor vehicle is moved relative to the object and ultrasound signals are continuously emitted by means of an ultrasonic sensor of the assistance system, wherein echoes of the ultrasound signals reflected by the object are received, wherein respective amplitudes of the received echoes are determined by means of a control device, and a classification of a height of the object is determined on the basis of the amplitudes, wherein the classification of the height of the object is determined on the basis of a determined first change in amplitude by comparing a first amplitude of a first echo of a first reflected ultrasound signal with a second amplitude of a second echo of a second reflected ultrasound signal received after the first echo, wherein the classification of the height of the object is determined on the basis of a comparison of the first change in amplitude with a second change in amplitude, and in that the second change in amplitude is determined by comparing a third amplitude of a third echo of a third reflected ultrasonic signal received after the second echo with the second amplitude of the second echo or with a fourth amplitude of a fourth echo of a fourth reflected ultrasound signal which was received after the second echo and before the third echo.

2. The method (100) as claimed in claim 1, characterised in that the first echo and the second echo are temporally successive echoes.

3. The method (100) as claimed in claim 1 or 2, characterised in that the object is located in a proximity of the motor vehicle, preferably at a distance of up to two metres from the ultrasonic sensor of the motor vehicle, in that, when the motor vehicle approaches the object, the object is classified as low if a decrease in amplitude over time is determined as the first change in amplitude, and in that the object is classified as high if an increase in amplitude over time is determined as the first change in amplitude.

4. The method (100) as claimed in any one of the preceding claims, characterised in that, when the motor vehicle approaches the object, the object is classified as low if an increase in amplitude over time is determined as the first change in amplitude and a decrease in amplitude over time is determined as the second change in amplitude.

5. The method (100) as claimed in any one of claims 1 to 3, characterised in that the object is located in a proximity of the motor vehicle, preferably at a distance of up to two metres from the ultrasonic sensor of the motor vehicle, and in that, when the motor vehicle approaches the object, the object is classified as low if a decrease in amplitude over time is determined in each case as the first change in amplitude and as the second change in amplitude, and if, additionally, the second change in amplitude is greater than the first change in amplitude.

6. The method (100) as claimed in any one of the preceding claims, characterised in that the object is located in a proximity of the motor vehicle, preferably at a distance of up to two metres from the ultrasonic sensor of the motor vehicle, and in that, when the motor vehicle approaches the object, the object is classified as high if in each case an increase in amplitude over time is determined as the first change in amplitude and as the second change in amplitude, and if, additionally, the second change in amplitude is greater than the first change in amplitude.

7. The method (100) as claimed in any one of the preceding claims, characterised in that the classification of the height of the object is determined if, in addition, the amount of the first change in amplitude lies above a predefined threshold value.

8. The method (100) as claimed in claim 7, characterised in that the threshold value is predetermined depending on a current speed of the motor vehicle and / or a temperature in the environment of the motor vehicle and / or an air humidity in the environment of the motor vehicle and / or an installation height of the ultrasonic sensor on the motor vehicle.

9. The method (100) as claimed in any one of the preceding claims, characterised in that the comparison of the amplitudes is based on a difference and / or a ratio of the amplitudes.

10. The method (100) as claimed in any one of the preceding claims, characterised in that the comparison of the changes in amplitude is based on a difference and / or a ratio of the changes in amplitude.

11. The method (100) as claimed in any one of the preceding claims, characterised in that the method is applied during an assisted and / or semi-automatic and / or automatic parking method.

12. The method (100) as claimed in any one of the preceding claims, characterised in that the classification of the height of the object is based exclusively on sensor data from the ultrasonic sensor.

13. An assistance system having an ultrasonic sensor and a control device which is designed to carry out a method (100) as claimed in any one of the preceding claims.