Method for characterising an object in an environment of a motor vehicle
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-03
- Publication Date
- 2026-03-04
AI Technical Summary
Existing methods for determining the height of objects using one-dimensional distance sensors in motor vehicles are inaccurate and costly, as they rely on fixed thresholds that are influenced by environmental conditions and object reflectivity, and require additional sensors or cameras for reliable classification.
A method that uses a control device to determine the classification of an object's height based on the echo density parameter, which is derived from the number of received echoes, without relying on absolute thresholds or limit values, by analyzing the course of the echo density parameter as the vehicle moves relative to the object, allowing for cost-effective and reliable classification.
Enables accurate and reliable classification of object height using a single distance sensor, independent of environmental conditions, without the need for threshold comparisons, effectively distinguishing between 'high' and 'low' objects that can or cannot be driven over.
Smart Images
Figure EP2024058993_31102024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Method for characterizing an object in a motor vehicle environment
[0003] The invention relates to a method for characterizing an object in the environment of a motor vehicle by means of an assistance system of the motor vehicle, wherein the motor vehicle is moved relative to the object and measurement signals are emitted by a distance sensor of the assistance system, and wherein echoes of the measurement signals reflected by the object are received. A control device of the assistance system determines a classification of a height of the object based on an echo density parameter determined from a number of received echoes. The invention further relates to an assistance system having a distance sensor and a control device designed to carry out such a method.
[0004] A distance sensor in a motor vehicle is typically used for environmental detection. A distance, or in other words, the distance to an object, is determined based on the propagation time between a transmitted measurement signal and a received echo of the measurement signal reflected from an object. Such a distance sensor is usually designed as a radar sensor or an ultrasonic sensor, with ultrasonic sensors being particularly widespread and installed in almost all passenger vehicles today.
[0005] Ultrasonic sensors typically comprise a transmitter that emits ultrasonic signals as measurement signals, which propagate through the air at the speed of sound of approximately 340 meters per second. For this purpose, a membrane of the ultrasonic sensor is usually excited to mechanical vibrations using a corresponding transducer element. The ultrasonic signal is reflected as an echo from surrounding objects and detected by a receiver of the ultrasonic sensor. Based on the time of flight between the time of transmission and the time of reception, the distance to the object can be determined, taking into account the propagation speed of the ultrasonic signal. The amplitude of the reflected ultrasonic signal or echo can also be determined.
[0006] Ultrasonic sensors are typically used in motor vehicles to detect the surroundings within a range of up to approximately 7 meters. Ultrasonic sensors are particularly important in semi-automatic or automatic driving maneuvers, especially in connection with parking applications, such as parking distance measurement, parking space searches, or parking. The vehicle is typically moved relative to the objects, with a measurement cycle being performed at predetermined times during the movement. During each measurement cycle, an ultrasonic sensor emits an ultrasonic signal.Methods and corresponding assistance systems are already known from the state of the art that use ultrasonic sensors to provide the driver with various information about the vehicle's surroundings and assist the driver in maneuvering the vehicle, particularly in locating a parking space and parking the vehicle in the space. For example, there are
[0007] Assistance systems equipped with parking space location 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 park the vehicle. To reliably locate and measure a parking space, such assistance systems require information about objects in the vicinity of the vehicle, which can include parked vehicles, curbs, walls, and other obstacles.
[0008] In addition to the distance of the motor vehicle to an object, the height of the object is usually also important. Height is an important factor in deciding whether or not an object or obstacle can be driven over. Especially if the motor vehicle is maneuvered at least semi-autonomously based on the measurements of a distance sensor, it is desirable to determine the height of the detected object. Determining the height with one-dimensional (1D) distance sensors, i.e. distance sensors for distance determination, which are regularly used in the automotive sector, is fundamentally quite difficult due to physical limitations. The height of an object cannot be measured directly using such a distance sensor.For height determination, for example, an additional camera is used and the height is estimated based on a 2D image, or a multi-sensor-based method is used to estimate the height based on triangulation. However, methods based on a single camera or multiple sensors do not exploit the advantages of a 1D distance sensor in terms of cost and robustness.
[0009] A method and an assistance system of the type mentioned above are known, for example, from DE 10 2007 039 348 A1. Ultrasonic signals are emitted using an ultrasonic sensor of the motor vehicle, and the echoes, formed as ultrasonic pulses, of the ultrasonic signals reflected from an object are received. For a received ultrasonic pulse, a center of gravity is determined as a point in time between a first point in time when the ultrasonic pulse exceeds a first threshold value and a subsequent second point in time when the ultrasonic pulse falls below a second threshold value. A distance to the object is determined based on the determined center of gravity.In addition, a classification of a height of the object is determined based on a pulse width of the reflected, received ultrasonic pulses, the ratio of the number of received ultrasonic pulses to the number of emitted ultrasonic pulses and / or a distribution of the distances from a plurality of reflected ultrasonic pulses determined by time-of-flight measurements.
[0010] From DE 10 2004 047 479 A1, a further method for characterizing an object in the environment of a motor vehicle is known, in which, in order to classify the height of the object as the motor vehicle passes by the object located to the side of the motor vehicle, ultrasonic signals are emitted by means of an ultrasonic sensor, wherein the classification of the height of the object is determined based on a comparison of an amplitude of a received echo with a predefinable threshold value.
[0011] The present invention is based on the object of providing an alternative method for characterizing an object in the environment of a motor vehicle and a corresponding assistance system which enables the height of the object to be classified as cost-effectively as possible and at the same time as accurately and reliably.
[0012] The above object is achieved by the entire teaching of claim 1 and the independent claim 12. Advantageous embodiments and further developments of the invention are set forth in the subclaims and the following description.
[0013] In the method according to the invention for characterizing an object in the environment of a motor vehicle using an assistance system of the motor vehicle, the motor vehicle is moved relative to the object, and a distance sensor of the assistance system transmits measurement signals and receives echoes of the measurement signals reflected by the object. A control device of the assistance system determines a classification of the height of the object based on an echo density parameter determined from the number of received echoes.
[0014] According to the invention, a course of the echo density parameter is determined, wherein the classification of the height of the object is determined based on the course of the echo density parameter.
[0015] The invention is based on the consideration that the use of absolute or fixed threshold or limit values, in particular those defined in advance, for example, for a specific framework or situation, when determining the classification regularly yields inaccurate or even incorrect classification results. This is because, for example, the current temperature and humidity in the environment of the motor vehicle, which each have a noticeable impact on airborne sound attenuation, as well as the current speed of the motor vehicle, have a strong influence on the number of reflected or receivable echoes. In contrast, the use of threshold or limit values that can be adjusted during operation of the motor vehicle, for example, to the current temperature, current humidity and / or current speed of the motor vehicle, results in a very high evaluation and computational effort.Furthermore, the number of reflected or receivable or received echoes generally also depends on the material or the reflectivity of the material of the object, which is usually unknown and cannot be determined and therefore cannot be used to set or adjust threshold or limit values. Furthermore, the invention is based on the consideration that a particularly cost-effective and reliable classification of the height of an object is made possible if, when determining the classification, the use of thresholds or limit values, in particular the use of thresholds or limit values for comparison with the echo density parameter or a value derived therefrom, is avoided as far as possible. Therefore, the invention provides that a profile of the echo density parameter is determined, and that the classification of the object's height is determined based on the profile of the echo density parameter.
[0016] The embodiment according to the invention has the advantage that it provides a method by means of which a cost-effective, yet accurate and reliable classification of the height of the object is possible.
[0017] The objects to be characterized can be, in particular, stationary objects that extend from the ground, for example a road surface or other terrain, and extend essentially orthogonally to the ground, such as a curb, a wall or a vehicle. However, they can also be objects that do not extend from the ground, such as a crossbar of a fence, or that do not extend orthogonally to the ground, such as a ramp. Advantageously, the motor vehicle is moved towards the object or away from the object, i.e. the motor vehicle approaches the object or moves away from the object. During the corresponding movement of the motor vehicle, the echo density parameter is determined continuously or continuously.
[0018] The course of the echo density parameter is advantageously a time course and / or a distance-dependent course, i.e. a course dependent on the distance or the distance of the motor vehicle from the object.
[0019] The distance sensor can be arranged at various positions on the vehicle, for example, at the front, rear, or side, and is advantageously designed as a 1D distance sensor. A single distance sensor can be used. However, multiple distance sensors can also be used.
[0020] The two classes “high” and “low” are used in particular to classify the height of the object. The object is classified as “high” if it is an object that cannot be driven over by a motor vehicle, in particular if it is relevant to a collision, and the object is classified as “low” if it is an object that can be driven over by a motor vehicle. Alternatively, the object is classified as “high” if the object is at least at the installation height of the distance sensor, i.e. in particular if the object has a height that is at least equal to the installation height of the distance sensor. The object is classified as “low” if the object is below the installation height of the distance sensor, i.e. in particular if the object has a height that is less than the installation height of the distance sensor.
[0021] In an advantageous embodiment, the course of the echo density parameter is not compared with a, in particular predetermined, threshold value to determine the classification of the object's height. In order to determine the classification of the object's height, the course of the echo density parameter is therefore not compared with a, in particular predetermined, threshold or limit value; a comparison with a threshold or limit value therefore does not take place. The corresponding determination is therefore carried out in particular independently of a threshold or limit value being exceeded or undershot. Advantageously, in order to determine the classification of the object's height, a determined echo density parameter is also not compared with a, in particular predetermined, threshold or limit value; the determination is therefore carried out in particular independently of a threshold or limit value being exceeded or undershot.
[0022] In a further advantageous embodiment, the classification of the height of the object is determined based on a change, preferably an increase and / or decrease, in the course of the echo density parameter. The classification of the height of the object is therefore determined based on the change in the course, in particular with a distance or a separation of the motor vehicle or distance sensor from the object. Preferably, the classification of the height of the object is determined based on an increase and / or a decrease in the course, wherein in particular it is determined whether there is an increase or a decrease in the course of the echo density parameter, and wherein the classification of the object is determined depending on this determination, in particular the object is classified as "high" or "low".
[0023] In a further advantageous embodiment, the object is located in the immediate vicinity of the motor vehicle, preferably at a distance of up to three, more preferably up to two, meters from the distance sensor of the motor vehicle, wherein as the motor vehicle approaches the object, the object is classified as low if a decrease in the course of the echo density parameter is determined, and wherein the object is classified as high if an increase in the course of the echo density parameter is determined. The classification as low is determined in particular for an object that is below the installation height of the distance sensor, i.e. which in particular has a height that is less than the installation height of the distance sensor. Such an object is, for example, a curb.The classification as high is determined in particular for an object that is at least at the installation height of the distance sensor, i.e., that has a height that is at least equal to the installation height of the distance sensor. Such an object is, for example, a wall, a fence, or a vehicle.
[0024] This is based in particular on the fact that an object with a height that is at least equal to the installation height of the distance sensor in the motor vehicle has a higher reflectivity for the measurement signals than an object with a height that is less than the installation height of the distance sensor. Thus, the measurement signals from an object with a height that is at least equal to the installation height of the distance sensor in the motor vehicle are reflected by several points on the object's surface that are orthogonal and non-orthogonal to the distance sensor. In contrast, the measurement signals from an object with a height that is less than the installation height of the distance sensor are only reflected by those points on the object's surface that are not orthogonal to the distance sensor, resulting in a smaller number of reflected measurement signals or echoes.Furthermore, the radiation pattern of a distance sensor, particularly an ultrasonic sensor, is fundamentally a function of the elevation angle. Therefore, the power of a measurement signal emitted by a distance sensor to an object in the detection range depends on the object's elevation angle relative to the distance sensor. For an object with a height less than the installation height of the distance sensor in the motor vehicle, the elevation angle and thus the power, or in other words, the amplitude of the reflected measurement signal, change depending on the distance between the motor vehicle or distance sensor and the object, particularly below a certain distance between the object and the motor vehicle, or more precisely, between the object and the distance sensor.If the distance decreases, i.e. if the motor vehicle approaches the object further, the elevation angle decreases, which can lead to the amplitude of the reflected measurement signal decreasing so sharply that a measurement signal reflected from the object is not detected. In a further advantageous embodiment, the classification of the height of the object is determined based on a gradient of the curve of the echo density parameter. In order to classify the height of the object, the gradient or (several) gradients of the curve of the echo density parameter are evaluated, and the height of the object is classified based on this. The gradient of the curve of the echo density parameter represents in particular the temporal (first) derivative of the curve of the echo density parameter. Based on the determined gradient, the height of the object can be determined in particular even more precisely or finely or.be determined in a more differentiated manner, whereby in addition to or instead of the two classes “high” and “low”, more than two and / or more differentiated classes can be used to classify the height of the object, for example a classification as (among others) “high, not driveable”, “low, not driveable”, “low, driveable” and “low, vehicle door can be opened without damage”.
[0025] Advantageously, the object is located in close proximity to the motor vehicle, preferably at a distance of up to three, preferably up to two, meters from the distance sensor of the motor vehicle, wherein, as the motor vehicle approaches the object, the object is classified as low if a negative gradient of the echo density parameter curve is determined, and wherein the object is classified as high if a positive gradient of the echo density parameter curve is determined. Preferably, a finer or more differentiated classification of the height of the object is additionally carried out based on a specific (absolute) value of the respectively determined gradient, wherein in particular more than two classes and a differentiated classification as merely "high" and "low" are used here.
[0026] In particular, the echo density parameter can correspond to the number of echoes received.
[0027] In a further advantageous embodiment, however, the echo density parameter is determined as a ratio of the number of received echoes to a predetermined temporal measurement window, wherein the number of received echoes is preferably normalized to a temporal duration of the measurement window. The number of echoes is therefore preferably normalized to a predetermined period of time, wherein the predetermined period of time corresponds in particular to the temporal duration in which the corresponding object is detected by the distance sensor, i.e., in which measurement signals are transmitted from the distance sensor to the object. If, for example, the temporal measurement window with respect to a first object is larger than the temporal measurement window with respect toof a second object, wherein the area, in particular surface, of the first object detected or detectable by the distance sensor is the same size as the area, in particular surface, of the second object detected or detectable by the distance sensor, and wherein the same number of echoes are received from the first object as from the second object, the echo density parameter of the first object is smaller than the echo density parameter of the second object.
[0028] Alternatively or additionally, in a further advantageous embodiment, the echo density parameter is determined as a ratio of the number of received echoes to a predetermined area within the environment, wherein the number of received echoes is preferably normalized to the predetermined area within the environment. The number of echoes is therefore preferably normalized to a predetermined environmental region or a predetermined area unit. The predetermined area is preferably the area, in particular the surface, of the object detected or detectable by means of the distance sensor. For example, the echo density parameter of a first object with such a large area, from which the same number of echoes are received as from a second object with a smaller area, is smaller than the echo density parameter of the second object.
[0029] Advantageously, the echo density parameter is determined as a ratio of the number of received echoes to a predetermined temporal measurement window and a predetermined area within the environment, wherein the number of received echoes is preferably normalized to a temporal duration of the measurement window and to the predetermined area within the environment. Alternatively or in addition to determining the echo density parameter as a ratio of the number of received echoes to a predetermined temporal measurement window and / or determining the echo density parameter as a ratio of the number of received echoes to a predetermined area within the environment, in a further advantageous embodiment the echo density parameter is determined as a ratio of the number of received echoes to the number of transmitted measurement signals, wherein the number of received echoes is preferably normalized to the number of transmitted measurement signals.
[0030] In a further advantageous embodiment, respective distance values are determined based on the received echoes, wherein the number of received echoes is weighted as a function of at least one distance value, and wherein the echo density parameter is determined based on the weighted number of echoes. Advantageously, the number of received echoes is weighted as a function of more than one distance value, in particular as a function of all distance values of the corresponding echoes. By taking the distance and such weighting into account, the fact that the detection behavior of objects varies depending on the distance is taken into account. This can increase the reliability of the height classification.
[0031] The distance sensor is advantageously designed as a radar sensor. In a preferred embodiment, however, the distance sensor is designed as an ultrasonic sensor, wherein the measurement signals are in the form of ultrasonic signals. 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. In a further advantageous embodiment, the method is applied to an assisted and / or semi-automatic and / or automatic parking method.
[0032] The present invention further comprises an assistance system with a distance sensor and a control device. The control device is configured to carry out the method according to the invention.
[0033] The advantages and preferred embodiments described for the method according to the invention also apply accordingly to the assistance system according to the invention.
[0034] Embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings:
[0035] Fig. 1 is a radiation diagram showing a radiation pattern of an ultrasonic sensor as a function of the elevation angle,
[0036] Fig. 2a shows a curve of the echo density parameter for a low object when the motor vehicle approaches,
[0037] Fig. 2b shows a curve of the echo density parameter for a high object when the motor vehicle approaches, and
[0038] Fig. 3 is a flowchart of a method for characterizing an object in the environment of a motor vehicle.
[0039] Fig. 1 shows a radiation pattern diagram illustrating the radiation pattern 1 of an ultrasonic sensor of a motor vehicle as a function of the elevation angle. This shows 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 to an object in the detection range depends on the elevation angle.
[0040] If an object is at an elevation angle of 90°, i.e., at least at the installation height of the ultrasonic sensor in a motor vehicle, the elevation angle 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 essentially on the distance between the ultrasonic sensor and the object. Therefore, the amplitude of the reflected ultrasonic signal becomes progressively larger as the motor vehicle or ultrasonic sensor approaches a tall object.
[0041] For an object that is less high than the installation height of the ultrasonic sensor in the motor vehicle, the elevation angle and thus the power or amplitude of the reflected ultrasonic signal change depending on the distance between the motor vehicle or ultrasonic sensor and the object. As the motor vehicle or ultrasonic sensor approaches the object, the elevation angle becomes successively smaller until it reaches almost 0° as soon as the ultrasonic sensor is directly next to the object. As the distance decreases, i.e. as the motor vehicle gets closer and closer to the object, the elevation angle decreases, which can lead to the amplitude of the reflected ultrasonic signal decreasing so drastically that an ultrasonic signal reflected from the object is not detected.
[0042] Fig. 2a shows a plurality of curves 2, each representing a course of an echo density parameter for a low object, for example, a curb, as the motor vehicle approaches the object. Fig. 2b correspondingly shows a plurality of curves 3, each representing a course of an echo density parameter for a tall object, for example, a wall that is significantly higher than the curb, as the motor vehicle approaches the object. The distance of the object from the motor vehicle is plotted on the abscissa, and the value of the echo density parameter is plotted on the ordinate.
[0043] As can be clearly seen in Figs. 2a and 2b, when the motor vehicle or the ultrasonic sensor of the motor vehicle is at a distance of approximately 2.4 meters from the respective object, the echo density parameter for the curb and for the wall has a similar value in a range of approximately 0.8 to 0.9. As can be seen further from Fig. 2a, when the motor vehicle or the ultrasonic sensor of the motor vehicle is at a distance of approximately or just over 2 meters from the curb, the echo density parameter initially drops significantly or steeply down to a distance of approximately 0.5 meters as the motor vehicle approaches the curb. As the vehicle approaches the curb further, the echo density parameter continues to drop and (ideally) approaches the value 0. In contrast, the echo density parameter increases when the motor vehicle or the ultrasonic sensor is at a distance of approximatelyThe echo density parameter increases significantly or steeply from the wall of approximately or just over 2 meters as the vehicle approaches the wall (further) up to a distance of approximately 0.5 meters. As the vehicle approaches the curb further, the echo density parameter continues to increase, approaching (ideally) the value 1.
[0044] Based on the decreasing echo density parameter curve as the vehicle approaches the curb as shown in Fig. 2a, particularly within the distance range of approximately or just over 2 meters to 0.5 meters, the object or curb is classified as low. In contrast, based on the increasing echo density parameter curve as the vehicle approaches the wall as shown in Fig. 2b, particularly within the distance range of approximately or just over 2 meters to 0.5 meters, the object or wall is classified as high.
[0045] Based on the course of the echo density parameter, the height of an object can thus be classified cost-effectively, accurately and reliably, in particular without the use of thresholds or limit values for comparison with the echo density parameter, the course of the echo density parameter or a value derived therefrom.
[0046] Fig. 3 shows 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 device and a 1D ultrasonic sensor, which has a radiation pattern according to Fig. 1. The motor vehicle approaches the object in close proximity, for example, at or from a distance of approximately 2.5 meters.
[0047] In a step 101, ultrasonic signals are continuously emitted by the ultrasonic sensor and echoes of the ultrasonic signals reflected by the object are received.
[0048] In a step 102, which can also be carried out, at least partially, in parallel to step 101, the number of echoes received from the object and an echo density parameter based on the number of echoes received are determined continuously over time, in particular using a sliding window, wherein, for example, the echo density parameter is determined as a ratio of the number of echoes received to the number of ultrasonic signals emitted.
[0049] In step 103, a classification of the object's height is determined. For this purpose, the distance-dependent course of the echo density parameter is evaluated, and depending on an increase or decrease in the course of the echo density parameter, the object is classified as a tall object that cannot be driven over by the motor vehicle, or as a short object that can be driven over by the motor vehicle.
[0050] In this way, the height of the object can be classified cost-effectively and reliably without the need to use thresholds or limit values for comparison with the echo density parameter, the echo density parameter curve, or a value derived therefrom.
Claims
Patent claims 1. Method (100) for characterizing an object in an environment of a motor vehicle by means of an assistance system of the motor vehicle, wherein the motor vehicle is moved relative to the object and measurement signals are emitted by a distance sensor of the assistance system, wherein echoes of the measurement signals reflected by the object are received, and wherein a classification of a height of the object is determined by means of a control device of the assistance system based on an echo density parameter determined on the basis of a number of the received echoes, characterized in that a profile of the echo density parameter is determined and in that the classification of the height of the object is determined based on the profile of the echo density parameter.
2. Method (100) according to claim 1, characterized in that in order to determine the classification of the height of the object, no comparison of the course of the echo density parameter with a, in particular predetermined, threshold value is carried out.
3. Method (100) according to claim 1 or 2, characterized in that the classification of the height of the object is determined based on a change, preferably an increase and / or decrease, in the course of the echo density parameter.
4. Method (100) according to claim 3, characterized in that the object is located in a close range of the motor vehicle, preferably at a distance of up to three meters from the distance sensor of the motor vehicle, that when the motor vehicle approaches the object, the object is classified as low if a decrease in the course of the echo density parameter is determined, and that the object is classified as high if an increase in the course of the echo density parameter is determined.
5. Method (100) according to one of the preceding claims, characterized in that the classification of the height of the object is determined based on a gradient of the course of the echo density parameter.
6. Method (100) according to one of the preceding claims, characterized in that the echo density parameter is determined as a ratio of the number of received echoes to a predetermined temporal measurement window, wherein preferably the number of received echoes is normalized to a temporal duration of the measurement window.
7. Method (100) according to one of the preceding claims, characterized in that the echo density parameter is determined as a ratio of the number of received echoes to a predetermined area within the environment, wherein preferably the number of received echoes is normalized to the predetermined area within the environment.
8. Method (100) according to one of the preceding claims, characterized in that the echo density parameter is determined as a ratio of the number of received echoes to the number of transmitted measurement signals, wherein preferably the number of received echoes is normalized to the number of transmitted measurement signals.
9. Method (100) according to one of the preceding claims, characterized in that respective distance values are determined on the basis of the received echoes, and in that the number of received echoes is weighted as a function of at least one distance value, wherein the echo density parameter is determined on the basis of the weighted number of echoes.
10. Method (100) according to one of the preceding claims, characterized in that the distance sensor is an ultrasonic sensor and that the measurement signals are designed as ultrasonic signals.
11. The method (100) according to one of the preceding claims, characterized in that the method is applied to an assisted and / or semi-automatic and / or automatic parking method.
12. An assistance system with a distance sensor and a control device designed to carry out a method (100) according to one of the preceding claims.