阅读说明：本技术 借助由车辆上安装的超声波传感器所接收的超声波信号评估对象高度的方法和设备 (Method and device for estimating the height of an object by means of ultrasonic signals received by an ultrasonic sensor mounted on a vehicle ) 是由 C·马蒂斯 J·施密特 T·赖曼 M·舒曼 于 2020-04-09 设计创作，主要内容包括：提出一种借助由车辆上所布置的超声波传感器(12)检测到的超声波信号评估车辆周围环境中的对象(30)的对象高度(H)的方法。在一个测量周期内,检测作为对象的棱边反射或直行回波的第一超声波信号(13)。由此计算用于对应的内角反射的期望窗口。将在该期望窗口内所检测到的第二超声波信号(14)识别属于第一超声波信号的内角反射,并将第一超声波信号与第二超声波信号合并为一个信号组。随后为每个超声波信号确定显著性。通过比较该显著性,将信号组配属给第一回波组或第二回波组。随着确定数量的测量周期推移确定配属给第一回波组和第二回波组的比率,并根据第一比率和第二比率对对象高度(H)进行评估。(A method for estimating an object height (H) of an object (30) in the surroundings of a vehicle by means of ultrasonic signals detected by an ultrasonic sensor (12) arranged on the vehicle is proposed. During a measuring cycle, a first ultrasonic signal (13) is detected as an edge reflection or a straight echo of the object. From which the desired window for the corresponding internal angle reflection is calculated. The second ultrasonic signal (14) detected within the desired window is identified as belonging to an inner angle reflection of the first ultrasonic signal and the second ultrasonic signal are combined into one signal group. Significance is then determined for each ultrasonic signal. By comparing the significance, the signal group is assigned to the first echo group or the second echo group. The ratio assigned to the first echo group and the second echo group is determined over a defined number of measurement cycles, and the height (H) of the object is evaluated on the basis of the first ratio and the second ratio.)

1. A method for estimating a height (H) of an object by means of ultrasonic signals detected by an ultrasonic sensor (12) arranged on a vehicle, characterized by comprising the steps of:

during a measurement period:

a. detecting a first ultrasonic signal (13) as an edge reflection or a straight echo of the object (30);

b. calculating an expected window for the corresponding internal corner reflection;

c. detecting a second ultrasonic signal;

d. -if the second ultrasonic signal (14) is detected within the desired window, recognizing the second ultrasonic signal (14) as corresponding to an interior angle reflection of the first ultrasonic signal (13) and combining the first ultrasonic signal (13) and the second ultrasonic signal (14) into one signal combination;

e. determining a first significance of the first ultrasonic signal (13) and determining a second significance of the second ultrasonic signal (14), wherein the significance of each detected ultrasonic signal (13, 14) accounts for a probability that the detected ultrasonic signal (13, 14) is a reflection of the emitted ultrasonic signal at the at least one object;

f. assigning the set of signals to an object (30) in the surroundings of the vehicle;

g. comparing the first and second saliency and assigning the signal group to a first echo group or a second echo group based on the comparison;

determining a first ratio of signal groups belonging to the first echo group over a determined number of measurement periods (21, 22, 23, 24, 25);

determining a second ratio of signal groups belonging to the second echo group over a determined number of measurement periods (21, 22, 23, 24, 25);

-said evaluating said object height (H) according to said first and second ratios.

2. Method according to claim 1, characterized in that the desired window is calculated based on the propagation time of the first ultrasonic signal (13), the installation height (h) of the ultrasonic sensor and/or a height threshold (S).

3. Method according to claim 1 or 2, characterized in that the significance of the first ultrasonic signal (13) and/or the significance of the second ultrasonic signal (14) is determined from at least one parameter (a, R) which comprises information contained in a received signal (ES), in particular an amplitude (a) and/or a correlation coefficient (R), wherein the received signal is generated by the ultrasonic sensor (12) from the ultrasonic signal received by the ultrasonic sensor during the measurement period, and the significance is determined by:

the spatial region extending from the ultrasonic sensor to the maximum range of action of the ultrasonic sensor is divided into a plurality of successive partial regions (T1, T2, T3) and, depending on the position of the partial region (T1, T2, T3) in which the respective ultrasonic signal is present, at least one parameter (A, R) to be used for the evaluation of the significance of each received ultrasonic signal is selected from a predefined set of parameters.

4. Method according to one of claims 1 to 3, characterized in that the significance of each received ultrasonic signal is evaluated by means of a significance scale having a plurality of discrete significance levels, wherein the significance of the first ultrasonic signal and/or the significance of the second ultrasonic signal is determined by: assigning the determined significance level to the ultrasonic signal.

5. Method according to claim 4, characterized in that four significance levels are provided, comprising a first significance level "low", a second significance level "medium", a third significance level "high" and a fourth significance level "very high", wherein a significance level "low" corresponds to a low probability of an ultrasound signal (13, 14) coming from a reflection of the emitted ultrasound signal at the at least one object (30), wherein a significance level "medium" corresponds to a probability of an ultrasound signal (13, 14) coming from a reflection of the emitted ultrasound signal at the at least one object (30) of medium magnitude, wherein a significance level "high" corresponds to a high probability of an ultrasound signal coming from a reflection of the emitted ultrasound signal (13, 14) at the at least one object (30), wherein a significance level "very high" corresponds to an ultrasound signal (13, 14) a high probability of reflection from the emitted ultrasonic signal at the at least one object (30).

6. Method according to one of claims 1 to 5, characterized in that a signal group comprising a first ultrasonic signal (13) and a second ultrasonic signal (14) is assigned to the first echo group if the difference between the first significance and the second significance is small, in particular if both ultrasonic signals have the same significance level, or if the first ultrasonic signal has a very high significance, in particular has the significance level "very high".

7. Method according to one of claims 1 to 6, characterized in that a signal group comprising the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the second echo group if the first ultrasonic signal has a low significance, in particular has a significance level "low", and the second ultrasonic signal has a higher significance than the first ultrasonic signal, in particular has either a significance level "high" or "very high".

8. Method according to one of claims 1 to 7, characterized in that the signal group is assigned to an object (30) in the vehicle surroundings by trilateration.

9. The method according to any one of claims 1 to 8, characterized in that the assessment of the object height (H) is made by: comparing a determined first ratio of a signal set belonging to the first echo set with a first threshold value, and/or comparing a determined second ratio of a signal set belonging to the second echo set with a second threshold value, and/or comparing a sum of the first ratio and the second ratio with a third threshold value.

10. The method of claim 9, wherein the third threshold is greater than the first threshold, and wherein the third threshold is greater than the second threshold.

11. The method according to any one of claims 1 to 10, wherein the subject height is assessed as follows: whether the object can be safely rolled by a vehicle.

12. The method according to one of claims 1 to 11, characterized in that the evaluation of the object height (H) according to the first and second ratios is only carried out when the vehicle is moving or a higher evaluation threshold is used in the evaluation in the stationary state of the vehicle.

13. An ultrasonic sensor system for a vehicle, comprising:

at least one ultrasonic sensor (12) which is designed to emit an ultrasonic signal and to detect an ultrasonic signal (13, 14) of the emitted ultrasonic signal reflected at the object (30);

a computing unit configured for carrying out the method according to one of claims 1 to 12 for evaluating an object height (H) of the object (30) by means of the ultrasound signals detected by the ultrasound sensor (12).

14. A computer program comprising program code for performing the method according to any one of claims 1 to 12 when the computer program is executed on a computer.

Technical Field

The invention relates to a method and a corresponding device for estimating the height of an object during a plurality of successive measuring cycles by means of ultrasonic signals received by an ultrasonic sensor mounted on a vehicle.

Background

Driver assistance systems for vehicles are known from the prior art, which each provide an ultrasonic-based driver assistance function. Such a driver assistance system comprises, for example, the following driver assistance functions: this function provides, for example, a parking-in or parking-out aid which ensures autonomous parking-in or parking-out of the vehicle, with automatic intervention being carried out on the longitudinal and transverse guidance of the respective vehicle.

As the safety aspects of the driver assistance function described above have increased, it is very important to evaluate the height of an object detected by the vehicle ultrasonic sensor and whether the object can be safely passed by the vehicle.

In the case of objects having an extension in a direction perpendicular to the road plane, in particular in the case of objects having a wall shape, a plurality of echo signals are usually received on the basis of one emitted ultrasonic signal. For example, the object height can in principle be estimated by the propagation time difference. However, the problem arises precisely in the case of wall-shaped objects, because of the reflective properties of such objects, that the ultrasonic signal reflected back to the ultrasonic sensor from the upper edge of the wall may be much weaker than the ultrasonic signal reflected back to the ultrasonic sensor from the so-called internal angle (Kehle), i.e. the contact area of the object with the ground.

DE 102012211293 a1 discloses a method for operating a surroundings detection system of a vehicle having at least one ultrasonic sensor. In this case, the ultrasonic sensor emits a frequency-modulated ultrasonic signal. The ultrasonic sensor and/or the one or more further ultrasonic sensors also emit an ultrasonic signal which is an ultrasonic signal. In this method, it is provided that the ultrasonic signal is filtered such that the ground ultrasonic signal portion is suppressed. Here, amplitude information and phase information are determined from the received ultrasonic signal. Furthermore, a ground clutter curve associated with time is determined. A signal evaluation function is also determined which is associated with the amplitude information, the phase information and preferably also with the ground clutter curve. Corresponding ambient detection systems are also known from the same document.

DE 102015209939 a1 discloses a method for assessing the significance of ultrasonic signals, in which ultrasonic signals are received during a measuring cycle by means of an ultrasonic sensor mounted on a vehicle. The significance of the respective received ultrasonic signal is evaluated in accordance with at least one parameter, which comprises the information contained in the received signal. The received signal is generated by the ultrasonic sensor from an ultrasonic signal received by the ultrasonic sensor during a measurement period. The significance of the received ultrasonic signal indicates the probability of the ultrasonic signal originating from the emission of the emitted ultrasonic signal at the at least one object.

Disclosure of Invention

A method for estimating the height of an object in the surroundings of a vehicle is proposed, wherein the estimation is carried out by means of ultrasonic signals detected by ultrasonic sensors arranged on the vehicle.

During a measurement cycle, a first ultrasonic signal is detected as an edge reflection or a straight echo of the object. From this, the expected window for the corresponding internal angle reflection (Kehlenreflex) is calculated. The second ultrasonic signal detected within the desired window is identified as an interior angle reflection corresponding to the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are combined into a signal combination. The significance is now determined for each ultrasonic signal. By comparing the significance, the signal group is assigned to the first echo group or the second echo group. The ratio associated with the first echo group and with the second echo group is determined over a determined number of measurement cycles, and the height of the object is evaluated on the basis of the first ratio and the second ratio.

The method according to the invention has the following steps:

during a measurement cycle:

a. detecting a first ultrasonic signal of an edge reflection or a straight echo as an object;

b. calculating an expected window for the corresponding internal corner reflection;

c. detecting a second ultrasonic signal;

d. identifying the second ultrasonic signal as corresponding to an interior angle reflection of the first ultrasonic signal and combining the first ultrasonic signal and the second ultrasonic signal into one signal group if the second ultrasonic signal is detected within the desired window;

e. determining a first significance of the first ultrasonic signal and determining a second significance of the second ultrasonic signal, wherein each significance of the detected ultrasonic signal indicates a probability that the detected ultrasonic signal is a reflection of the emitted ultrasonic signal at the at least one object;

f. assigning the set of signals to objects in the vehicle surroundings;

g. comparing the first and second saliency and assigning a signal group to the first echo group or the second echo group based on the comparison;

after a determined number of measurement cycles have been performed:

determining a first ratio of signal groups belonging to a first echo group over a determined number of measurement cycles;

determining a second ratio of signal groups belonging to a second echo group over a determined number of measurement cycles; determining a second ratio of assigning the set of signals to a second set of echoes over a number of measurement cycles;

evaluating the height of the object according to the first ratio and the second ratio

The following facts are considered first: the object that reflects the detected ultrasonic signal back is a wall-like object. Wall-like means that the object has an extension perpendicular to the road plane and furthermore (for example opposite the pillar) has a certain extension in the longitudinal direction. Examples of wall-like objects are walls (Mauer), house walls or high curbs.

Therefore, the first ultrasonic signal is first detected during the measurement period. If the object to be reflected has a height which is less than the installation height of the sensor, the ultrasonic signal is an edge reflection. If the object has a height greater than the sensor mounting height, the ultrasonic signal represents a straight echo, i.e. an echo thrown on a direct path from the object surface. In both cases, the first echo signal detected in time is involved, since the sound wave which caused this signal in both cases travels the shortest path to the sensor. Next, an expected window for the corresponding internal angular reflection of the object is calculated. The desired window is a defined time interval within the measurement cycle during which, assuming that the previously detected first ultrasonic signal is an edge reflection or a so-called straight echo, an interior angle reflection is expected, i.e. an echo signal emanating from the spatial region in which the object stands on the ground. The boundary of the desired window can be calculated from the geometric conditions of the ultrasonic sensor (for example the installation height) and assuming that the object is a wall-like object. If a second ultrasonic signal is now detected that is located within the desired window previously calculated for the inner angle reflection, the second ultrasonic signal is identified as the inner angle reflection corresponding to the first ultrasonic signal and the second ultrasonic signal are combined into a signal combination.

Furthermore, a first significance of the first ultrasonic signal and a second significance of the second ultrasonic signal are determined, wherein each detected significance of an ultrasonic signal indicates a probability that the ultrasonic signal originates from a reflection of the emitted ultrasonic signal at the at least one object.

The signal group is associated with the object in the surroundings of the vehicle, for example by means of trilateration. In addition, the first significance and the second significance are compared. Based on the comparison, the signal group is assigned to the first echo group or the second echo group. Here, the first echo set may be defined such that a ratio and/or a difference between the first saliency and the second saliency indicates that there is a height of the object that is greater than a determined height threshold. The second echo set may be defined such that a ratio and/or difference between the first and second saliency indicates having a height of the object less than a determined height threshold.

The above steps a.to g. are carried out for a plurality of measurement cycles. Over a determined number x of measurement cycles, a first ratio of signal sets belonging to a first echo set and a second ratio of signal sets belonging to a second echo set are determined. For example, the first and second ratios may be determined over a number x-16 of measurement cycles. In particular, the first ratio and the second ratio are determined continuously (slidingly) over the last x measurement cycles. Based on the first ratio and the second ratio, the object height is now evaluated, in particular as follows: whether the object can be safely rolled by the vehicle.

The geometric relationship between the detected first ultrasonic signal (edge reflection or direct echo) and the detected second ultrasonic signal (interior angle) of the low wall is thus used in a targeted manner, taking into account the significance ratio or the poor significance of the detected ultrasonic signals.

Preferably, the desired window for the interior angle reflection is calculated on the basis of the propagation time of the first ultrasonic signal, the installation height of the ultrasonic sensor on the vehicle (measured above the road plane) and/or a minimum object height, wherein the minimum object height is determined in particular in dependence on the vehicle type and in particular specifies an upper limit value for the rollability of the object. For example, the minimum object height may be 30 centimeters for a typical passenger car. The installation height of the ultrasonic sensor may be, for example, 45 cm. Here, the propagation time of the first ultrasonic signal represents a distance, particularly a shortest distance, between the ultrasonic sensor and the object.

In one possible embodiment of the invention, the desired window is designed such that the lower limit of the desired window is calculated from the determined minimum object height, while the upper limit of the desired window is calculated assuming "that an object having a height greater than or equal to the sensor mounting height is present. These two variables are calculated with tolerances due to possible measurement errors. If the object has a height that is less than the sensor mounting height, the echo is within the desired window.

From the prior art, in particular from DE 102015209939 a1, various possibilities are known for assigning a significance to an ultrasonic signal, which indicates the probability that the ultrasonic signal is a reflection of the emitted ultrasonic signal at least one object.

Preferably, the significance of the first ultrasonic signal and/or the significance of the second ultrasonic signal is determined as a function of at least one parameter which comprises information contained in the received signal, in particular the amplitude and/or the correlation coefficient. In this case, the received signal is generated by the ultrasonic sensor from the ultrasonic signal received by the ultrasonic sensor during the measuring cycle.

Significance is determined in particular by:

the spatial region extending from the ultrasonic sensor to the maximum operating distance of the ultrasonic sensor is divided into a plurality of successive partial regions, and at least one parameter to be used for assessing the significance of each received ultrasonic signal is selected from a predefined set of parameters as a function of the position of the partial region in which the respective ultrasonic signal is present.

The significance of each received ultrasonic signal is particularly preferably evaluated by means of a significance scale having a plurality of discrete significance levels, wherein the significance of the first ultrasonic signal and/or the significance of the second ultrasonic signal is determined in the following manner: assigning the determined significance level to the ultrasonic signal.

In particular, four significance levels are provided, including a first significance level "low", a second significance level "medium", a third significance level "high" and a fourth significance level "very high", wherein the significance level "low" corresponds to a low probability of the ultrasound signal being reflected from the emitted ultrasound signal at the at least one object, wherein the significance level "medium" corresponds to a medium-sized probability of the ultrasound signal being reflected from the emitted ultrasound signal at the at least one object, wherein the significance level "high" corresponds to a high probability of the ultrasound signal being reflected from the emitted ultrasound signal at the at least one object, wherein the significance level "very high" corresponds to a very high probability of the ultrasound signal being reflected from the emitted ultrasound signal at the at least one object.

The significance level may for example correspond to the following probability:

low: 30 to 50 percent

The method comprises the following steps: 51 to 70 percent

High: 71 to 90 percent

Very high: 91% to 100%.

Further possibilities and embodiments for determining and evaluating the significance of the detected ultrasonic signals can be derived from DE 102015209939 Al.

In a preferred embodiment of the invention, a signal group comprising the first ultrasonic signal and the second ultrasonic signal is assigned to the first echo group if the difference between the first significance and the second significance is small, in particular if the two ultrasonic signals have the same significance level, or if the first ultrasonic signal has a very high significance, in particular a "very high" significance level. The assignment of a signal group to the first echo group indicates that the object is relatively high.

It is further preferred that the set of signals comprising the first ultrasonic signal and the second ultrasonic signal is assigned to the second echo group if the first ultrasonic signal has a low significance, in particular has a significance level "low", and the second ultrasonic signal has a higher significance than the first ultrasonic signal, in particular has either a significance level "high" or "very high".

In a preferred embodiment of the invention, the object height is evaluated by: the determined first ratio at which the signal set belongs to the first echo set is compared with a first threshold. Additionally or alternatively, the determined second ratio of the signal set belonging to the second echo set is compared with a second threshold value. Further, a sum of the first ratio and the second ratio may additionally or alternatively be compared to a third threshold. Preferably, the third threshold value is greater than the first threshold value and greater than the second threshold value. The following conditions are thus considered: even in the common case where all measurements relate to the same object, ratios greater than zero are measured for both echo sets, since the echo amplitude, and thus the significance, can vary depending on the viewing angle. By changing the echo groups of the individual signal groups, the respective other echo groups now lack these signal groups and may not reach the necessary ratio for exceeding the threshold value. For this reason, the sum of the two ratios is also preferably taken into account, wherein the respective third threshold value is selected higher than the first and second threshold values in order to avoid false evaluation results (false alarms).

In particular, strongly structured wall-like objects, such as walls, may also provide more than two echo signals. Advantageously, in this case more than one second ultrasonic signal is combined with the first ultrasonic signal as a signal group, wherein at least the second ultrasonic signal of the group detected last in time is intended to be located within the desired window. When such a signal group is assigned to one of these echo groups, the significance of all the ultrasound signals contained in the signal group can be evaluated and compared.

An alert may be triggered if the object is evaluated as an object above a determined minimum object height of, for example, 30 centimeters.

The evaluation of the object height based on the first ratio and the second ratio is preferably performed only when the vehicle is in motion. Alternatively, a higher evaluation threshold value for the first threshold value and/or the second threshold value and/or the third threshold value can be used for the evaluation when the measurement is carried out in a stationary state of the vehicle. This prevents erroneous evaluation of the height of the object.

According to a second aspect of the invention, an ultrasonic sensor system for a vehicle is specified, comprising at least one ultrasonic sensor which is designed to emit an ultrasonic signal and to detect an ultrasonic signal of the emitted ultrasonic signal which is reflected at an object, and comprising a computing unit which is designed to carry out the method designed as described above for estimating the height of the object by means of the ultrasonic signal detected by the ultrasonic sensor.

According to a third aspect of the invention, a computer program is proposed, comprising program code for performing the method according to the invention when the computer program is executed on a computer.

The invention makes it possible to classify non-rollable ground-securing objects robustly, such as small retaining walls (Stutzmauer) or walls, in particular objects having a height below the installation height of the sensor, and thus reliably helps to avoid damage to the vehicle.

Drawings

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 shows a profile of the ultrasonic signal reception signal occurring during a measurement cycle and the phase information contained in the reception signal, said profile being shown as a function of the distance from the ultrasonic sensor;

fig. 2 schematically shows an example of an ultrasonic sensor arranged close to a wall-like object on a vehicle;

FIG. 3 shows first and second ultrasonic signals for different measurement periods;

fig. 4 shows a method according to an embodiment of the invention in the form of a flow chart.

Detailed Description

In the following description of the embodiments of the present invention, the same elements are denoted by the same reference numerals, and repeated description of the elements is omitted as necessary. The figures only schematically show the content of the invention.

According to a first embodiment of the present invention, evaluation of the significance of each ultrasonic signal received by means of an ultrasonic sensor mounted on a vehicle during a measurement cycle is described with reference to fig. 1. The significance of each received ultrasonic signal indicates the probability of the ultrasonic signal originating from a reflection of the ultrasonic signal emitted by the ultrasonic sensor at the beginning of the measuring cycle at the at least one object. The at least one object is located in the surroundings of the vehicle. Each received ultrasonic signal resulting from the reflection of the emitted ultrasonic signal at the at least one object is also referred to below as an object echo signal.

Fig. 1 includes a graph 10, which shows a signal intensity of an ultrasonic sensor reception signal ES occurring during a measurement cycle as a function of the distance of the ultrasonic sensors. The distance from the ultrasonic sensor ranges here from a minimum distance value of zero to a maximum distance value dmax. The maximum distance value dmax corresponds to the maximum distance value dmax of the ultrasonic sensor. The reception signal ES is generated by the ultrasonic sensor from the ultrasonic signal received by the ultrasonic sensor during the measurement period. The amplitude a of the received signal, which is dependent on the distance from the ultrasonic sensor, is determined by means of the received signal ES.

Fig. 1 also includes a diagram 20, which shows a profile of the phase information R contained in the received signal ES as a function of the distance from the ultrasonic sensor. To generate the correlation signal, the received signal ES is correlated with the filter function of the optimization filter. The phase information R corresponds to a correlation coefficient R, which is determined by means of the correlation signal in relation to the distance from the ultrasonic sensor. The correlation coefficient R describes the phase relationship between each received ultrasonic signal and the emitted ultrasonic signal and has a value between 0 and 1. In other words, the correlation coefficient R is a measure of the similarity between each received ultrasound signal and the filter function of the optimization filter.

In fig. 1, a first axis of the unitless value, which may have a signal strength of the received signal ES normalized by means of a predefined normalization variable, is denoted by S. In fig. 1, the second axis, denoted RW, illustrates a phase information value, which may have a phase information R. In fig. 1, a third axis is denoted by d, which illustrates the distance values given in centimeters, which may have a distance from the ultrasonic sensor.

In FIG. 1, a minimum range value dmin and a maximum range value dmax of the ultrasonic sensor are also plotted.

According to the first embodiment, the spatial region extending from the ultrasonic sensor up to the maximum working distance of the ultrasonic sensor is divided into the first partial region T1, the second partial region T2, and the third partial region T3. The three partial regions T1, T2, T3 are each continuous and follow one another. The first partial region T1 directly adjoins the ultrasonic sensor. Furthermore, the third partial region T3 extends up to the maximum working distance of the ultrasonic sensor.

According to a first embodiment, a predefined set of parameters with three parameters A, R, A/BP is used. In this case, a first parameter a of the predefined parameter set corresponds to an amplitude a of the received signal ES which is dependent on the distance from the ultrasonic sensor. The second parameter R of the predefined parameter set also corresponds to the phase information R relating to the distance from the ultrasonic sensor. Furthermore, the third parameter a/BP of the predefined set of parameters coincides with the quotient between the first parameter a and the ground clutter level BP of the received signal ES. The ground clutter level BP does not change during the measurement period and is determined from the signal strength or amplitude of the received signal ES occurring in a predefined section of the received signal ES. The predefined section results from the reception of such an ultrasonic signal: the ultrasonic signal results from a reflection of the emitted ultrasonic signal on the ground on which the vehicle is located.

According to a first embodiment, for each of the three partial regions T1, T2, T3 of the spatial region, T1, T2, T3, at least one parameter A, R, A/BP of a predefined set of parameters is selected for evaluating the significance of each received ultrasonic signal generated in the respective partial region T1, T2, T3 of the spatial region. According to the first embodiment, the parameter value range of one of the three partial regions T1, T2, T3 of each parameter A, R, A/BP of the predefined set of parameters selected for the respective partial region, which is applicable to this spatial region, is also subdivided into a first, a second, a third and a fourth partial region. This is done for each of the three partial regions T1, T2, T3. The four part-areas of each parameter value range are respectively continuous and follow one another. Furthermore, the parameter values of each parameter value range are evaluated by means of the same parameter value scale with the first, second, third and fourth parameter value classes. In this case, a first parameter value class is assigned to the parameter values of the first subregion of each parameter value range. Thereby, the parameter values of the first partial region of each parameter value range are respectively ranked "low". In addition, a second parameter value class is associated with the parameter values of the second subregion of each parameter value range. The parameter values of the second partial region of each parameter value range are thereby respectively classified as "medium". The third parameter value class is associated with the parameter values of the third subregion of each parameter value range. The parameter values of the third partial region of each parameter value range are thereby each rated as "high". In addition, a fourth parameter value class is associated with the parameter values of the fourth partial region of each parameter value range. The parameter values of the fourth partial region of each parameter value range are thereby each rated as "very high".

According to a first embodiment of the invention, the significance of each received ultrasonic signal is also evaluated by means of a significance scale having a first, a second, a third and a fourth significance level. Here, the significance of the first significance level is ranked as "low". Here, the significance of the second significance level is ranked as "medium". The significance of the third significance level is ranked as "high". Further, the significance of the fourth significance level is ranked as "very high".

According to a first embodiment, the first parameter a and/or the second parameter R are selected to evaluate the significance of each received ultrasonic signal occurring in the first partial region T1 of the spatial region. In the following, each received ultrasonic signal occurring in the first partial region T1 of the spatial region is also referred to as a first ultrasonic signal. Here, if the parameter value of the first parameter a or of the second parameter R is rated as "very high" when each first ultrasonic signal is received, the significance of the first ultrasonic signal is rated as "very high". Further, if the parameter values of the first parameter a and the second parameter R are ranked as "high" at the time of receiving each first ultrasonic signal, the significance of that first ultrasonic signal is ranked as "high". Further, if the parameter value of the first parameter a is classified as "medium" and the parameter value of the second parameter R is classified as "high", "medium", or "low" at the time of receiving each first ultrasonic signal, the first ultrasonic signal is classified as "medium". Further, if the parameter value of the first parameter a is ranked as "low" and the parameter value of the second parameter R is ranked as "high", "medium", or "low" at the time of receiving each first ultrasonic signal, the significance of the first ultrasonic signal is ranked as "low".

According to the first embodiment, the second parameter R and/or the third parameter a/BP are/is selected to evaluate the significance of each received ultrasonic signal occurring in the second partial region T2 of the spatial region. In the following, each received ultrasonic signal occurring in the second partial region T2 of the spatial region is also referred to as a second ultrasonic signal. Here, if the parameter value of the second parameter R or the third parameter a/BP is ranked as "very high" when each second ultrasonic signal is received, the significance of each second ultrasonic signal is ranked as "very high". Further, if the parameter value of the second parameter R is ranked as "high" or "medium" and the parameter value of the third parameter a/BP is ranked as "high" at the time of receiving each second ultrasonic signal, the significance of the second ultrasonic signal is ranked as "high". In addition, if the parameter value of the second parameter R is ranked as "medium" and the parameter value of the third parameter a/BP is ranked as "medium" or "low" when each second ultrasonic signal is received, the significance of the second ultrasonic signal is ranked as "medium". Further, if the parameter value of the second parameter R is ranked as "low" and the parameter value of the third parameter a/BP is ranked as "high" or "medium" or "low" at the time of receiving each second ultrasonic signal, the significance of the second ultrasonic signal is ranked as "low".

According to the first embodiment, the second parameter R is selected for evaluating the significance of each received ultrasonic signal occurring in the third partial region T3 of the spatial region. In the following, each received ultrasonic signal occurring in the third partial region T3 of the spatial region is also referred to as a third ultrasonic signal. Here, if the parameter value of the second parameter R is rated as "very high" when each third ultrasonic signal is received, the significance of the third ultrasonic signal is rated as "very high". Further, if the parameter value of the second parameter R is ranked as "high" at the time of receiving each third ultrasonic signal, the significance of the third ultrasonic signal is ranked as "high". If the parameter value of the second parameter R is ranked as "medium" at the time of receiving each third ultrasonic signal, the significance of the third ultrasonic signal is ranked as "medium". Further, if the parameter value of the second parameter R is ranked as "low" at the time of receiving each third ultrasonic signal, the significance of the third ultrasonic signal is ranked as "low".

Fig. 1 also shows the profile of the first threshold value SW1 and the profile of the second threshold value SW 2. Here, upon receiving each object echo signal, the first threshold value SW1 is exceeded by the reception signal ES. The second threshold value SW2 is also exceeded by the phase information R upon reception of each object echo signal. As can be seen from fig. 1, a first object echo signal is received during the measurement cycle, which first object echo signal occurs in a second partial region T2 of the spatial region. As can also be seen from fig. 1, the location of the first object echo signal is at a distance from the ultrasonic sensor, which has a first distance value d1 of approximately 100 cm. It can further be seen from fig. 1 that the first amplitude value exhibited by the amplitude a of the received signal ES at the first distance value dl exceeds the first threshold value SW1 and is significantly greater than the ground clutter level BP. Here, the parameter value assumed by the third parameter a/BP at the first distance value dl is calculated as the quotient between the first amplitude value and the ground clutter level BP and is rated "high". It can further be seen from fig. 1 that the first phase information value represented by the amplitude AR of the second parameter R at the first distance value dl exceeds the second threshold value SW2 and is greater than 0.9. The first phase information value is ranked "high". This means that according to the first embodiment, the significance of the first object echo signal is ranked as "high".

The ultrasonic sensor 12 is schematically shown in fig. 2 a). The ultrasonic sensor 12 is arranged at a mounting height h above the lane plane 17, for example at the rear of the vehicle (not shown). In the surroundings of the vehicle there are wall-like objects 30, for example low walls. The object has a height H in this example which is greater than the mounting height H of the sensor 12.

At the beginning of the measurement cycle, the ultrasonic sensor 12 emits an ultrasonic signal. The ultrasonic signal is reflected at the object 30 and the reflected ultrasonic signal is sensed by the ultrasonic sensor 12. The first temporally sensed ultrasonic signal corresponds to the reflection of a point 32 on the surface of the object 30 directly opposite the ultrasonic sensor 12. The point 32 has a shortest distance d with respect to the ultrasonic sensor 12₂. The reflected ultrasonic signal emanating from this point thus has the shortest propagation time. Such ultrasonic signals are also referred to as direct signals or direct echoes.

By interior corner reflection is understood an ultrasonic signal emitted from an interior corner region 33, i.e. that region in which the wall-like structure of the object 30 stands on the ground and forms a substantially rectangularly shaped reflection region. The internal angle reflection is received later in time than the direct echo, because of the distance d between the ultrasonic sensor 12 and the internal angle region 33₁Is greater than the distance d between the ultrasonic sensor 12 and the point 32 directly opposite the ultrasonic sensor 12₂。

The mounting height h of the ultrasonic sensor 12 is known. Furthermore, the minimum object height S is known, from which the object is no longer evaluated as rollable. For geometrical considerations, an expected window for detecting internal angular reflections can be calculated from the detection time points of the straight echoes. If a second ultrasonic signal is actually received within the expected window, the second ultrasonic signal may be combined with the first ultrasonic signal into a signal combination.

The ultrasonic sensor 12 is schematically shown in fig. 2 b). The ultrasonic sensor 12 is also arranged at a mounting height h above the lane plane 17, for example in the rear of the vehicle (not shown). In the surroundings of the vehicle there are wall-like objects 30', for example low walls. The object has a height H' in this example which is less than the installation height of the sensor 12 but greater than a height threshold s, which specifies the height of the object: beyond which the object is no longer assessed as rollable.

At the beginning of the measurement cycle, the ultrasonic sensor 12 emits an ultrasonic signal. The ultrasonic signal is reflected at the object 30, and the reflected ultrasonic signal is detected by the ultrasonic sensor 12. The first detected ultrasonic signal in time corresponds to the reflection of the upper edge 34 of the object 30'. The point 34 has a shortest distance d to the ultrasonic sensor 12 in this case₂Even if this point is not directly opposite the ultrasonic sensor 12 as in the example according to fig. 2 a). The reflected ultrasonic signal originating from this point 34 thus has the shortest propagation time of the detected reflected ultrasonic signal. Such ultrasonic signals are also referred to as edge reflections.

Here too, for geometrical considerations and from the detection time of the edge reflection 15, an expected window for detecting the inner angle reflection from the inner angle region 33 at the distance d1 can be calculated. If a second ultrasonic signal is actually received within the desired window, the second ultrasonic signal may be combined with the first ultrasonic signal into a signal combination.

Fig. 3 schematically shows the first ultrasonic signal 13 and the second ultrasonic signal 14 detected in five measurement cycles 21, 22, 23, 24 and 25 following one another. In this case, the time is plotted on the x-axis and the distance d calculated from the corresponding echo travel time is plotted on the y-axis. In each of the measurement periods 21, 22, 23, 24 and 25The first ultrasonic signal 13 and the second ultrasonic signal 14 are received during each measurement period. The distances corresponding to the ultrasonic signals 13, 14 decrease for successive measurement periods, which means that the detecting ultrasonic sensor 12 has moved during the measurement toward the reflecting object 30. Furthermore, the desired windows 41, 42, 43, 44 and 45 calculated from the detected first ultrasonic signal 13 are shown for each measurement cycle 21, 22, 23, 24 and 25. The lower distance limit 40' of each of the desired windows 41, 42, 43, 44 and 45 is calculated from the minimum object height s and the upper distance limit 40 "of each desired window is calculated from an object assumption having a height H greater than the sensor mounting height H. These two limit values are preferably calculated on the basis of a possible measurement error with a tolerance tol for the upper distance limit 40 ″_maxOr with tolerance tol for the lower distance boundary 40_min。

In the vehicle, the actual sensor mounting height h varies depending on the loading state of the vehicle. If the vehicle is empty ("unloaded"), a higher sensor mounting height h may be obtained than in the loaded state ("loaded")_unloadedA smaller sensor mounting height h is obtained in the loaded state_loaded. Typically, the sensor mounting height h varies by about 5 to 10 centimeters depending on the type of vehicle. This effect can be taken into account when calculating the upper and lower distance boundaries 40' and 40", for example by: two heights are used, h for the upper distance boundary 40 ″_unloadedTo obtain a larger value, use h for the lower distance boundary 40_loadedTo obtain smaller values.

Thus, the calculation of the upper distance boundary 40 ″ can be carried out, for example, by means of the following formula:

upper distance boundary d_1,max-d_2,ref+tol_max

The calculation of the lower distance boundary 40' can be carried out, for example, by means of the following formula:

lower distance boundary ═ d_1,min-d_2,ref-tol_min

Wherein D is_2，refEach corresponds to a direct echo distance, i.e. the distance from the point 32 directly opposite the ultrasonic sensor 12.

During each of the measurement periods 21, 22, 23, 24 and 25, the second ultrasonic signal 14 is detected within the respective measurement window 41, 42, 43, 44 and 45. Thus, a signal group can be formed from the detected ultrasonic signals 13 and 14 for each measurement cycle 21, 22, 23, 24 and 25. By determining the significance of each of the ultrasonic signals 13 and 14, as is shown with reference to fig. 1, and subsequently comparing these significances, each signal group can be assigned to a first or a second echo group. The ratios of the first echo set and the second echo set over the measurement period can now be calculated separately. These ratios may be compared to the determined first and second thresholds in order to assess the height of the subject 30. Additionally, the sum of the first ratio and the second ratio may also be compared to a third threshold. For example, in one possible embodiment of the invention, a first threshold s (for a first ratio of the first echo group)₁Is determined as s₁40%. Second threshold s (for a second ratio of the second echo group)₂Is also determined as s in this example₂40%. Third threshold s of the sum of the first ratio and the second ratio₃Is determined as s₃＝60％。

If now the first ratio is measured to be 35% and the second ratio to be 30%, despite the first threshold value s₁And a second threshold value s₂Is not exceeded, however the sum of the ratios of 65% exceeds a third threshold value s₃So that the height of the object 30 is evaluated as not-passable.

A method according to one embodiment of the invention is shown in flow chart form in fig. 4.

At step 90, a measurement cycle begins. In this case, for example, an ultrasonic signal is emitted from an ultrasonic sensor arranged on the vehicle into the surroundings of the vehicle.

In step 100, a first ultrasonic signal is detected as an edge reflection or as a straight echo of a high object.

In step 200, a desired window for the reflection of the interior angle of the corresponding genus is calculated based on the detected first ultrasonic signal.

In step 300, the second ultrasonic signal is examined.

In step 400 it is checked whether the second ultrasonic signal is detected within an expected window. If so, the second ultrasonic signal is identified as an interior angle reflection corresponding to the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are combined into a signal group. If not, the result is output.

In step 500, a first significance of the first ultrasonic signal is determined and a second significance of the second ultrasonic signal is determined, wherein each significance of the detected ultrasonic signal indicates a probability that the detected ultrasonic signal is a reflection of the emitted ultrasonic signal at the at least one object.

In step 600, the signal group is assigned to an object in the surroundings of the vehicle.

In step 700, a first significance is compared to a second significance. Depending on the result of the comparison, the signal group is assigned to the first echo group or the second echo group. And outputting the attachment result. A new measurement cycle is then started.

The result of the assignment of the identified signal group is detected over a plurality of measurement cycles.

In step 800, a first ratio of the identified signal assembly belonging to the first echo set and a second ratio of the identified signal assembly belonging to the second echo set are determined for the last 16 measurement periods, respectively. In this case, all measurement cycles are counted, even those measurement cycles in which, for example, no second ultrasonic signal is detected within the desired window or a valid significance of an ultrasonic signal cannot be determined.

In step 900, a first ratio of signal groups belonging to a first echo group is compared with a first threshold s₁Comparing and combining the signal with a second ratio belonging to a second echo group with a second threshold value s₂And (6) comparing. Further, the sum of the first ratio and the second ratio is compared with a third threshold s₃A comparison, wherein the third threshold value is in particular greater than two threshold values s₁And s₂。

In step 1000, the height of the subject is evaluated based on the comparison. Especially if the threshold value s₁、s₂Or s₃Is exceeded, the subject may be assessed as non-rollable.