Method and device for evaluating the height of an object by means of ultrasonic signals received by an ultrasonic sensor mounted on a vehicle

Abstract

A method for evaluating the object height (H) of an object (30) in the vehicle surroundings by means of an ultrasonic signal detected by an ultrasonic sensor (12) arranged on the vehicle is provided. In a measuring cycle, a first ultrasonic signal (13) is detected as an edge reflection or a straight echo of the object. From this, an expected window for the corresponding inner angle reflection is calculated. A second ultrasonic signal (14) detected within the expected window is used to identify the inner angle reflection belonging to the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are combined into a signal group. Subsequently, a significance is determined for each ultrasonic signal. By comparing the significance, the signal group is assigned to the first echo group or the second echo group. Over a certain number of measuring cycles, a ratio assigned to the first echo group and the second echo group is determined, and the object height (H) is evaluated based on the first ratio and the second ratio.

Description

Technical Field

[0001] The invention relates to a method and a corresponding device for evaluating 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 Art

[0002] Driver assistance systems for vehicles are known from the prior art, which each provide an ultrasound-based driver assistance function. Such driver assistance systems include, for example, driver assistance functions that provide, for example, parking assistance, which ensures autonomous parking of the vehicle, wherein automatic intervention is performed in the longitudinal and transverse guidance of the respective vehicle.

[0003] Due to the increasing safety aspects of the above-mentioned driver assistance functions, it is very important to evaluate the height of an object detected by the vehicle's ultrasonic sensors and whether the object can be safely driven over by the vehicle.

[0004] In the case of an object having an extension in a direction perpendicular to the road plane, in particular in the case of a wall-shaped object, a plurality of echo signals are usually received based on one emitted ultrasonic signal. For example, the height of the object can be estimated in principle by the propagation time difference. However, the following problem occurs precisely in the case of a wall-shaped object, because of the reflection characteristics of such an object, 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 inner corner (Kehle), that is, the contact area of ​​the object with the ground.

[0005] A method for operating a surroundings detection system of a vehicle having at least one ultrasonic sensor is known from document DE 10 2012 211 293 A1. In this case, the ultrasonic sensor emits a frequency-modulated ultrasonic signal. The ultrasonic sensor and / or one or more other ultrasonic sensors also receive an ultrasonic signal of the ultrasonic signal emitted. In this method, it is provided that the ultrasonic signal is filtered so that the ground ultrasonic signal is partially suppressed. In this case, amplitude information and phase information are determined based on the received ultrasonic signal. In addition, a ground clutter curve associated with time is also determined. A signal evaluation function associated with the amplitude information, the phase information and preferably also with the ground clutter curve is also obtained. A corresponding surroundings detection system is also known from the same document.

[0006] DE 10 2015 209 939 A1 discloses a method for evaluating the significance of ultrasonic signals, wherein ultrasonic signals are received during a measuring cycle by means of an ultrasonic sensor mounted on a vehicle. The significance of each received ultrasonic signal is evaluated as a function of at least one parameter, which comprises information contained in the received signal. The received signal is generated by the ultrasonic sensor from the ultrasonic signal received by the ultrasonic sensor during the measuring cycle. The significance of the received ultrasonic signal indicates the probability that the ultrasonic signal is derived from an emitted ultrasonic signal at at least one object. Summary of the invention

[0007] A method is proposed for assessing the height of objects in the surroundings of a vehicle, wherein the assessment is performed with the aid of ultrasonic signals detected by an ultrasonic sensor arranged on the vehicle.

[0008] In one measurement cycle, a first ultrasonic signal is detected as an edge reflection or a straight echo of an object. From this, an expected window for the corresponding internal angle reflection (Kehlenreflex) is calculated. The second ultrasonic signal detected in the expected window is identified as an internal angle reflection corresponding to the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are merged into a signal group. Now the significance is 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 ratio assigned to the second echo group is determined over a certain number of measurement cycles, and the object height is evaluated based on the first ratio and the second ratio.

[0009] The method according to the invention comprises the following steps:

[0010] In one measurement cycle:

[0011] a. detecting a first ultrasonic signal as an edge reflection or a straight echo of an object;

[0012] b. Calculate the desired window for the corresponding internal angle reflection;

[0013] c. detecting a second ultrasonic signal;

[0014] d. If a second ultrasonic signal is detected within the desired window, the second ultrasonic signal is identified as corresponding to the inner angle reflection of the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are combined into one signal group;

[0015] e. determining a first significance of the first ultrasonic signal and determining a second significance of the second ultrasonic signal, wherein the significance of each detected ultrasonic signal indicates a probability that the detected ultrasonic signal is a reflection of the emitted ultrasonic signal at at least one object;

[0016] f. assigning the signal group to an object in the vehicle's surroundings;

[0017] g. comparing the first significance with the second significance, and assigning the signal group to the first echo group or the second echo group based on the comparison;

[0018] After a certain number of measuring cycles:

[0019] determining a first ratio of the assignment of the signal group to the first echo group over a certain number of measuring cycles;

[0020] determining a second ratio for assigning the signal group to the second echo group over a certain number of measurement cycles; determining a second ratio for assigning the signal group to the second echo group during a certain number of measurement cycles;

[0021] Estimate the height of the object based on the first ratio and the second ratio

[0022] First of all, it is assumed that the object that reflects the detected ultrasonic signal is a wall-like object. Wall-like means that the object has an extension perpendicular to the road plane and also has a certain extension in the longitudinal direction (for example, in contrast to a pillar). Examples of wall-like objects are walls, house walls or high curbs.

[0023] Therefore, the first ultrasonic signal is first detected in the measurement cycle. If the reflecting object has a height less than the sensor installation height, the ultrasonic signal is an edge reflection. If the object has a height greater than the sensor installation height, the ultrasonic signal represents a straight echo, i.e. an echo thrown from the object surface on a direct path. In both cases, it is related to the first detected echo signal in time, because the sound wave causing the signal travels the shortest path relative to the sensor in both cases. Next, the expected window for the corresponding internal angle reflection of the object is calculated. The expected window is a limited time interval in the measurement cycle, in which, under the assumption that the first ultrasonic signal previously detected is an edge reflection or a so-called straight echo, an internal angle reflection is expected, i.e. an echo signal emitted from the spatial region where the object stands on the ground. Here, the boundaries of the expected window can be calculated based on the geometric given conditions of the ultrasonic sensor (e.g., the installation height) and assuming that the object is a wall-shaped object. If a second ultrasonic signal located in the expected window previously calculated for the internal angle reflection is now detected, the second ultrasonic signal is identified as an internal angle reflection corresponding to the first ultrasonic signal, and the first ultrasonic signal and the second ultrasonic signal are merged into a signal group.

[0024] Furthermore, a first significance of the first ultrasonic signal and a second significance of the second ultrasonic signal are determined, wherein the significance of each detected ultrasonic signal indicates the probability that the ultrasonic signal originates from a reflection of the emitted ultrasonic signal at at least one object.

[0025] The signal group is assigned to an object in the vehicle's surroundings, for example, by means of trilateration. In addition, a first significance and a second significance are compared. Based on the comparison, the signal group is assigned to a first echo group or a second echo group. The first echo group can be defined in such a way that a ratio and / or a difference between the first significance and the second significance indicates a height of an object greater than a certain height threshold. The second echo group can be defined in such a way that a ratio and / or a difference between the first significance and the second significance indicates a height of an object less than a certain height threshold.

[0026] The above steps a. to g. are implemented for a plurality of measurement cycles. Over a certain number x of measurement cycles, a first ratio of the signal group assigned to the first echo group and a second ratio of the signal group assigned to the second echo group are determined. For example, the first and second ratios can 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 most recent x measurement cycles. Based on the first ratio and the second ratio, the height of the object is now evaluated, in particular as follows: whether the object can be safely run over by a vehicle.

[0027] Therefore, the geometric relationship between the first detected ultrasonic signal (edge ​​reflection or direct echo) and the second detected ultrasonic signal (interior corner) of the low wall is used in a targeted manner taking into account the significance ratio or significance difference of the detected ultrasonic signals.

[0028] Preferably, the expected window of internal angular reflection is calculated based on the propagation time of the first ultrasonic signal, the installation height of the ultrasonic sensor on the vehicle (measured above the road surface) and / or the minimum object height, wherein the minimum object height is determined in particular in relation to the vehicle type and in particular indicates an upper limit value for the driveability 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 45 centimeters, for example. In this case, the propagation time of the first ultrasonic signal represents the distance of the ultrasonic sensor from the object, in particular the shortest distance.

[0029] In one possible embodiment of the invention, the expectation window is designed in such a way that the lower limit of the expectation window is calculated based on the determined minimum object height, while the upper limit of the expectation window is calculated under the assumption that an object with a height greater than or equal to the sensor installation height is present. Due to possible measurement errors, these two variables should be calculated with tolerances. If the object has a height less than the sensor installation height, the echo is within the expectation window.

[0030] From the prior art, in particular from DE 10 2015 209 939 A1, a number of different possibilities are known for assigning a significance to an ultrasonic signal, which indicates the probability that the ultrasonic signal is a reflection of an emitted ultrasonic signal at at least one object.

[0031] 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 an amplitude and / or a correlation coefficient. The received signal is generated by the ultrasonic sensor from the ultrasonic signal received by the ultrasonic sensor during a measuring cycle.

[0032] Significance is determined, inter alia, by:

[0033] A spatial area extending from the ultrasonic sensor to the maximum effective range of the ultrasonic sensor is divided into a plurality of continuous and successive partial areas, and at least one parameter to be used for evaluating the significance of each received ultrasonic signal is selected from a predefined parameter group based on the positioning of the partial area in which the corresponding ultrasonic signal appears.

[0034] Particularly preferably, 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 a specific significance level to the ultrasonic signal.

[0035] In particular, four significance levels are provided here, 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 that the ultrasonic signal comes from the reflection of the emitted ultrasonic signal at at least one object, wherein the significance level “medium” corresponds to a medium-sized probability that the ultrasonic signal comes from the reflection of the emitted ultrasonic signal at at least one object, wherein the significance level “high” corresponds to a high probability that the ultrasonic signal comes from the reflection of the emitted ultrasonic signal at at least one object, wherein the significance level “very high” corresponds to a very high probability that the ultrasonic signal comes from the reflection of the emitted ultrasonic signal at at least one object.

[0036] The significance level may correspond, for example, to the following probabilities:

[0037] Low: 30% to 50%

[0038] Medium: 51% to 70%

[0039] High: 71% to 90%

[0040] Very high: 91% to 100%.

[0041] Further possibilities and embodiments for determining and evaluating the significance of a detected ultrasonic signal can be found in DE 10 2015 209 939 A1.

[0042] In a preferred embodiment of the invention, the signal group including 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 high significance, in particular a significance level of "very high". The assignment of the signal group to the first echo group indicates that the object is relatively high.

[0043] Further preferably, if the first ultrasonic signal has a low significance, in particular a significance level of "low", and the second ultrasonic signal has a higher significance than the first ultrasonic signal, in particular a significance level of "high" or "very high", the signal group including the first ultrasonic signal and the second ultrasonic signal is assigned to the second echo group.

[0044] In a preferred embodiment of the present invention, the object height is evaluated in the following manner: a first ratio of a determination that a comparison signal group is assigned to a first echo group is compared with a first threshold value. Additionally or alternatively, a second ratio of a determination that a comparison signal group is assigned to a second echo group is compared with a second threshold value. In addition, or alternatively, the sum of the first ratio and the second ratio can be compared with a third threshold value. Preferably, the third threshold value is preferably greater than the first threshold value and greater than the second threshold value. Thus, the following situation is considered: even in the common case where all measurements involve the same object, a ratio greater than zero is measured for both echo groups, because the echo amplitude, and thus the significance, can vary depending on the observation angle. By changing the echo groups of individual signal groups, the corresponding other echo groups now lack these signal groups and may not reach the ratio required to exceed the threshold value. For this reason, the sum of the two ratios is also preferably considered, wherein the corresponding third threshold value is selected to be higher than the first and second threshold values ​​to avoid generating erroneous evaluation results (false alarms).

[0045] In particular, strongly structured wall-like objects, such as walls, can also provide more than two echo signals. Advantageously, in this case, more than one second ultrasonic signal is combined with the first ultrasonic signal to form a signal group, wherein at least the second ultrasonic signal of the group detected last in time should be located within the expected window. When such a signal group is assigned to one of the echo groups, the significance of all ultrasonic signals contained in the signal group can be evaluated and compared.

[0046] If an object is evaluated as being above a determined minimum object height of, for example, 30 centimeters, a warning can be triggered.

[0047] The evaluation of the height of the object based on the first ratio and the second ratio is preferably performed only when the vehicle is moving. Alternatively, when measuring when the vehicle is stationary, a higher evaluation threshold value can be used for the first threshold value and / or the second threshold value and / or the third threshold value during the evaluation. This can prevent an erroneous evaluation of the height of the object.

[0048] According to a second aspect of the present invention, an ultrasonic sensor system for a vehicle is proposed, comprising at least one ultrasonic sensor configured to emit an ultrasonic signal and detect an ultrasonic signal reflected at an object of the emitted ultrasonic signal, and comprising a computing unit configured to execute a method configured as described above for evaluating the height of an object with the aid of an ultrasonic signal detected by the ultrasonic sensor.

[0049] According to a third aspect of the present invention, a computer program is provided, comprising a program code for executing the method according to the present invention when the computer program is executed on a computer.

[0050] The invention allows for a robust classification of ground-fixed objects that cannot be driven over, such as small retaining walls or walls, in particular objects that are lower than the sensor installation height, and thus reliably helps to avoid damage to the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0052] Figure 1 shows a curve of an ultrasonic signal received signal and phase information contained in the received signal occurring during a measuring cycle as a function of the distance from the ultrasonic sensor;

[0053] Figure 2 Schematically shows an example of the arrangement of ultrasonic sensors on a vehicle when approaching a wall-like object;

[0054] Figure 3 showing first and second ultrasonic signals of different measurement periods;

[0055] Figure 4 A method according to an embodiment of the present invention is shown in the form of a flow chart. DETAILED DESCRIPTION

[0056] In the following description of the exemplary embodiments of the present invention, the same elements are marked with the same reference numerals, wherein a repeated description of these elements is omitted where necessary. The drawings merely schematically illustrate the content of the present invention.

[0057] According to the first embodiment of the present invention, Figure 1 The significance of each ultrasonic signal received by means of an ultrasonic sensor mounted on a vehicle during a measuring cycle is described below. The significance of each received ultrasonic signal indicates the probability that the ultrasonic signal comes from a reflection of an ultrasonic signal emitted by means of the ultrasonic sensor at the beginning of the measuring cycle at at least one object. The at least one object is located in the surroundings of the vehicle. Each received ultrasonic signal that comes from a reflection of an emitted ultrasonic signal at at least one object is also referred to below as an object echo signal.

[0058] Figure 1The invention comprises a graph 10 which shows the curve of the signal strength of an ultrasonic sensor reception signal ES occurring during a measuring cycle as a function of the distance from the ultrasonic sensor. In this case, the distance value range of the distance from the ultrasonic sensor extends from a minimum distance value zero to a maximum distance value dmax. In this case, the maximum distance value dmax corresponds to the value dmax of the maximum range 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 measuring cycle. The amplitude A of the reception signal is determined with the aid of the reception signal ES as a function of the distance from the ultrasonic sensor.

[0059] Figure 1 Also included is a graph 20 which shows the curve of the phase information R contained in the received signal ES as a function of the distance from the ultrasonic sensor. In order to generate the correlation signal, the received signal ES is correlated with the filter function of the optimization filter. In this case, the phase information R corresponds to a correlation coefficient R which is determined as a function of the distance from the ultrasonic sensor using the correlation signal. The correlation coefficient R describes the phase correlation 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 ultrasonic signal and the filter function of the optimization filter.

[0060] exist Figure 1 In , a first axis indicating unitless values ​​is labeled with S, which may include the signal strength of the received signal ES normalized by means of a predefined normalization variable. Figure 1 In FIG. 1 , a second axis indicating a phase information value is labeled with RW, and the phase information value may have phase information R. Figure 1 In FIG. 5 , a third axis is labeled with d, which indicates distance values ​​given in centimeters, which may be present at a distance from the ultrasonic sensor.

[0061] exist Figure 1 In FIG. 5 , the minimum range value dmin of the ultrasonic sensor and the maximum range value dmax of the ultrasonic sensor are also plotted.

[0062] According to the first embodiment, the spatial region extending from the ultrasonic sensor to the maximum range of the ultrasonic sensor is divided into a first sub-region T1, a second sub-region T2 and a third sub-region T3. The three sub-regions T1, T2 and T3 are respectively continuous and adjacent to each other. Here, the first sub-region T1 is directly adjacent to the ultrasonic sensor. In addition, the third sub-region T3 extends to the maximum range of the ultrasonic sensor.

[0063] According to a first embodiment, a predefined parameter set with three parameters A, R, A / BP is used. Here, the first parameter A of the predefined parameter set corresponds to the amplitude A of the received signal ES, which is related to the distance from the ultrasonic sensor. The second parameter R of the predefined parameter set also corresponds to the phase information R related to the distance from the ultrasonic sensor. In addition, the third parameter A / BP of the predefined parameter set corresponds to 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 cycle and is determined based on the signal strength or amplitude of the received signal ES that occurs in a predefined section of the received signal ES. The predefined section results from the reception of such an ultrasonic signal: the ultrasonic signal comes from the reflection of the emitted ultrasonic signal on the ground on which the vehicle is located.

[0064] According to a first embodiment, for each of the three partial regions T1, T2, T3 of the spatial region, at least one parameter A, R, A / BP in a predefined parameter group is selected to evaluate the significance of each received ultrasonic signal generated in the corresponding partial region T1, T2, T3 of the spatial region. According to a first embodiment, the parameter value range of each parameter A, R, A / BP selected for the corresponding partial region of the predefined parameter group for one of the three partial regions T1, T2, T3 of the spatial region is also subdivided into a first, second, third and fourth partial region. This is done for each of the three partial regions T1, T2, T3. The four partial regions of each parameter value range are respectively continuous and follow each other. In addition, 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 levels. Here, the first parameter value level is assigned to the parameter value of the first partial region of each parameter value range. As a result, the parameter value of the first partial region of each parameter value range is respectively classified as "low". In addition, the second parameter value level is assigned to the parameter value of the second partial area of ​​each parameter value range. As a result, the parameter value of the second partial area of ​​each parameter value range is respectively classified as "medium". The third parameter value level is assigned to the parameter value of the third partial area of ​​each parameter value range. As a result, the parameter value of the third partial area of ​​each parameter value range is respectively classified as "high". In addition, the fourth parameter value level is assigned to the parameter value of the fourth partial area of ​​each parameter value range. As a result, the parameter value of the fourth partial area of ​​each parameter value range is respectively classified as "very high".

[0065] According to a first embodiment of the present invention, the significance of each received ultrasonic signal is also evaluated by means of a significance scale having first, second, third and fourth significance levels. Here, the significance of the first significance level is graded as "low". Here, the significance of the second significance level is graded as "medium". The significance of the third significance level is graded as "high". In addition, the significance of the fourth significance level is graded as "very high".

[0066] According to a first embodiment, a first parameter A and / or a second parameter R are selected to evaluate the significance of each received ultrasonic signal appearing in a first partial region T1 of a spatial region. In the following, each received ultrasonic signal appearing in a first partial region T1 of a spatial region is also referred to as a first ultrasonic signal. Here, if the parameter value of the first parameter A or the second parameter R is graded as "very high" when each first ultrasonic signal is received, the significance of the first ultrasonic signal is graded as "very high". In addition, if the parameter values ​​of the first parameter A and the second parameter R are graded as "high" when each first ultrasonic signal is received, the significance of the first ultrasonic signal is graded as "high". In addition, if the parameter value of the first parameter A is graded as "medium" and the parameter value of the second parameter R is graded as "high", "medium" or "low" when each first ultrasonic signal is received, the first ultrasonic signal is graded as "medium". Furthermore, if the parameter value of the first parameter A is graded as “low” and the parameter value of the second parameter R is graded as “high”, “medium” or “low” when each first ultrasonic signal is received, the significance of the first ultrasonic signal is graded as “low”.

[0067] According to the first embodiment, the second parameter R and / or the third parameter A / BP are selected to evaluate the significance of each received ultrasonic signal appearing in the second partial region T2 of the spatial region. In the following, each received ultrasonic signal appearing 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 graded as "very high" when each second ultrasonic signal is received, the significance of each second ultrasonic signal is graded as "very high". In addition, if the parameter value of the second parameter R is graded as "high" or "medium" and the parameter value of the third parameter A / BP is graded as "high" when each second ultrasonic signal is received, the significance of the second ultrasonic signal is graded as "high". In addition, if the parameter value of the second parameter R is graded as "medium" and the parameter value of the third parameter A / BP is graded as "medium" or "low" when each second ultrasonic signal is received, the significance of the second ultrasonic signal is graded as "medium". Furthermore, if the parameter value of the second parameter R is graded as “low” and the parameter value of the third parameter A / BP is graded as “high” or “medium” or “low” when each second ultrasonic signal is received, the significance of the second ultrasonic signal is graded as “low”.

[0068] According to the first embodiment, the second parameter R is selected for evaluating the significance of each received ultrasonic signal appearing in the third partial region T3 of the spatial region. In the following, each received ultrasonic signal appearing 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 graded as "very high" when each third ultrasonic signal is received, the significance of the third ultrasonic signal is graded as "very high". In addition, if the parameter value of the second parameter R is graded as "high" when each third ultrasonic signal is received, the significance of the third ultrasonic signal is graded as "high". If the parameter value of the second parameter R is graded as "medium" when each third ultrasonic signal is received, the significance of the third ultrasonic signal is graded as "medium". In addition, if the parameter value of the second parameter R is graded as "low" when each third ultrasonic signal is received, the significance of the third ultrasonic signal is graded as "low".

[0069] Figure 1 In addition, the variation curve of the first threshold value SW1 and the variation curve of the second threshold value SW2 are also shown. Here, when each object echo signal is received, the first threshold value SW1 is exceeded by the received signal ES. When each object echo signal is received, the second threshold value SW2 is also exceeded by the phase information R. Figure 1 It can be seen from FIG. 1 that a first object echo signal is received during the measurement cycle, which first object echo signal appears in the second partial region T2 of the spatial region. Figure 1It can also be seen from FIG. 1 that the location where the first object echo signal appears is a distance from the ultrasonic sensor, and the distance has a first distance value d1 of about 100 cm. Figure 1 It can be further seen that the first amplitude value presented by the amplitude A of the received signal ES at the first spacing value d1 exceeds the first threshold value SW1 and is significantly greater than the ground clutter level BP. Here, the parameter value presented by the third parameter A / BP at the first spacing value d1 is calculated as the quotient between the first amplitude value and the ground clutter level BP and is classified as "high". Figure 1 It can be further seen that the first phase information value presented by the amplitude AR of the second parameter R at the first spacing value d1 exceeds the second threshold SW2 and is greater than 0.9. The first phase information value is classified as "high". This means that, according to the first embodiment, the significance of the first object echo signal is classified as "high".

[0070] Figure 2 In a), an ultrasonic sensor 12 is schematically shown. The ultrasonic sensor 12 is arranged at an installation height h above the road surface 17, for example at the rear of the vehicle (not shown). In the surroundings of the vehicle there is a wall-like object 30, for example a low wall. In this example, the object has a height H which is greater than the installation height h of the sensor 12.

[0071] At the beginning of the measuring 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 ultrasonic signal sensed first in time corresponds to the reflection of a point 32 on the surface of the object 30 that is directly opposite the ultrasonic sensor 12. Point 32 has the shortest distance d2 relative to the ultrasonic sensor 12. Therefore, the ultrasonic signal emitted from this point and reflected has the shortest propagation time. This ultrasonic signal is also called a straight signal or a direct echo.

[0072] The so-called inner corner reflection is understood to be an ultrasonic signal emitted from the inner corner area 33, that is, the area where the wall-like structure of the object 30 stands upright on the ground and forms a substantially rectangular reflection area. The inner corner reflection is received later in time than the direct echo because the distance d1 between the ultrasonic sensor 12 and the inner corner area 33 is greater than the distance d2 between the ultrasonic sensor 12 and the point 32 directly opposite the ultrasonic sensor 12.

[0073] The installation height h of the ultrasonic sensor 12 is known. In addition, the minimum object height S is known, from which an object is no longer evaluated as being run-over-able. For geometrical reasons, an expected window for detecting internal angle reflections can be calculated starting from the detection time of the straight echo. If a second ultrasonic signal is actually received within this expected window, it can be combined with the first ultrasonic signal to form a signal group.

[0074] Figure 2 b) shows schematically an ultrasonic sensor 12. The ultrasonic sensor 12 is also arranged at an installation height h above the road surface 17, for example at the rear of the vehicle (not shown). In the surroundings of the vehicle there is a wall-like object 30', for example a low wall. In this example, the object has a height H' which is less than the installation height of the sensor 12 but greater than a height threshold s, which indicates an object height above which the object is no longer evaluated as being drivable.

[0075] At the beginning of the measuring 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 ultrasonic signal detected first in time corresponds to the reflection of the upper edge 34 of the object 30'. Here, the point 34 has the shortest distance d2 to the ultrasonic sensor 12, even if it is not as large as the point according to Figure 2 a), directly opposite the ultrasonic sensor 12. As a result, the reflected ultrasonic signal originating from this point 34 has the shortest propagation time of the detected reflected ultrasonic signals. Such ultrasonic signals are also referred to as edge reflections.

[0076] Here too, an expected window for detecting the inner corner reflection from the inner corner region 33 at the distance d1 can be calculated for geometrical considerations and starting from the detection time of the edge reflection 15. If a second ultrasonic signal is actually received within this expected window, the second ultrasonic signal can be combined with the first ultrasonic signal to form a signal group.

[0077] Figure 3The first ultrasonic signal 13 and the second ultrasonic signal 14 detected in five successive measuring cycles 21, 22, 23, 24 and 25 are schematically shown. In this case, time is plotted on the x-axis and the distance d calculated from the corresponding echo propagation time is plotted on the y-axis. During each of the measuring cycles 21, 22, 23, 24 and 25, the first ultrasonic signal 13 and the second ultrasonic signal 14 are received. The distances corresponding to the ultrasonic signals 13, 14 decrease for successive measuring cycles, which means that the detecting ultrasonic sensor 12 has moved towards the reflecting object 30 during the measurement. In addition, the expected windows 41, 42, 43, 44 and 45 calculated from the detected first ultrasonic signal 13 are shown for each measuring 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 based on the minimum object height s and the upper distance limit 40" of each desired window is calculated based on the assumption of an object having a height H greater than the sensor installation height h. The two limit values ​​are preferably calculated based on possible measurement errors, which have a tolerance tol for the upper distance limit 40". max Or with a tolerance of tol for the lower distance boundary 40' min .

[0078] In a vehicle, the actual sensor installation height h varies depending on the loading state of the vehicle. If the vehicle is empty (“unloaded”), a higher sensor installation height h may be obtained than in a loaded state (“loaded”). unloaded , resulting in a smaller sensor installation height h in the loaded state loaded Typically, the sensor installation height h varies by about 5 to 10 cm depending on the vehicle type. This effect can be taken into account when calculating the upper and lower distance limits 40' and 40", for example by using two heights, using h for the upper distance limit 40". unloaded To get a larger value, use h for the lower distance boundary 40' loaded to obtain a smaller value.

[0079] Therefore, the calculation of the upper distance limit 40" can be performed, for example, with the aid of the following formula:

[0080]

[0081] Upper distance boundary = d 1,max -d 2,ref +tol max

[0082] The calculation of the lower distance limit 40' can be performed, for example, with the aid of the following formula:

[0083]

[0084] Lower distance boundary = d 1,min -d 2,ref -tol min

[0085] Among them, D 2，ref Each corresponds to the direct echo distance, ie the distance from point 32 which is directly opposite ultrasonic sensor 12 .

[0086] During each of the measurement cycles 21, 22, 23, 24 and 25, the second ultrasonic signal 14 is detected within the respective measurement windows 41, 42, 43, 44 and 45. Therefore, for each measurement cycle 21, 22, 23, 24 and 25, a signal group can be formed from the detected ultrasonic signals 13 and 14. By determining the significance of each of the ultrasonic signals 13 and 14, as shown in reference Figure 1 As shown, and then compare these significances, each signal group can be assigned to the first or second echo group. Now the ratio of the first echo group and the second echo group on the measurement cycle can be calculated respectively. These ratios can be compared with the determined first and second threshold values ​​in order to evaluate the height of the object 30. In addition, the sum of the first ratio and the second ratio can also be compared with the third threshold value. For example, in a possible embodiment of the present invention, the first threshold value s1 (for the first ratio of the first echo group) is determined to be s1=40%. The second threshold value s2 (for the second ratio of the second echo group) is also determined to be s2=40% in this example. The third threshold value s3 of the sum of the first ratio and the second ratio is determined to be s3=60%.

[0087] If a first ratio of 35% and a second ratio of 30% are now measured, although the first threshold s1 and the second threshold s2 are not exceeded, the sum of the ratios of 65% exceeds the third threshold s3, so that the height of the object 30 is assessed as being impossible to drive over.

[0088] Figure 4 A method according to an embodiment of the present invention is shown in the form of a flow chart.

[0089] A measuring cycle begins in step 90 , wherein an ultrasonic signal is emitted, for example, from an ultrasonic sensor arranged on the vehicle into the surroundings of the vehicle.

[0090] In step 100 , a first ultrasonic signal is detected as an edge reflection or as a straight echo of a tall object.

[0091] In step 200, a desired window for internal angle reflection of a corresponding genus is calculated based on the detected first ultrasonic signal.

[0092] In step 300, a second ultrasonic signal is detected.

[0093] In step 400, it is checked whether the second ultrasonic signal is detected within the expected window. If so, the second ultrasonic signal is identified as an inner 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.

[0094] In step 500 , a first significance of a first ultrasonic signal is determined and a second significance of a second ultrasonic signal is determined, wherein the significance of each detected ultrasonic signal indicates the probability that the detected ultrasonic signal is a reflection of the emitted ultrasonic signal at at least one object.

[0095] In step 600 , the signal set is assigned to an object in the vehicle's surroundings.

[0096] In step 700, the first significance is compared with the second significance. According to the result of the comparison, the signal group is assigned to the first echo group or the second echo group. The assignment result is outputted. Then a new measurement cycle is started.

[0097] The assignment of the identified signal group is detected over a plurality of measuring cycles.

[0098] In step 800, a first ratio of the assignment of the identified signal group to the first echo group and a second ratio of the assignment of the identified signal group to the second echo group are determined for the last 16 measurement cycles, respectively. In this case, all measurement cycles are counted, even those in which, for example, no second ultrasonic signal was detected within the expectation window or the effective significance of the ultrasonic signal could not be determined.

[0099] In step 900, a first ratio of the signal group to the first echo group is compared with a first threshold value s1 and a second ratio of the signal group to the second echo group is compared with a second threshold value s2. Furthermore, the sum of the first ratio and the second ratio is compared with a third threshold value s3, wherein the third threshold value is in particular greater than both threshold values ​​s1 and s2.

[0100] In step 1000 , the height of the object is evaluated based on the comparison result. In particular, if at least one of the thresholds s1 , s2 or s3 is exceeded, the object may be evaluated as not surmountable.

Claims

1. A method for evaluating the height (H) of an object by means of an ultrasonic signal detected by an ultrasonic sensor (12) arranged on a vehicle, characterized in that The following steps are involved: In one measurement cycle: a. detecting a first ultrasonic signal (13) as a reflection or a straight echo from an edge of an object (30); b. Calculate the expected window for the corresponding internal angle reflection; c. detecting a second ultrasonic signal; d. if the second ultrasonic signal (14) is detected within the expected window, the second ultrasonic signal (14) is identified as corresponding to the inner angle reflection of the first ultrasonic signal (13), and the first ultrasonic signal (13) and the second ultrasonic signal (14) are combined into one signal group; 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) indicates the probability that the detected ultrasonic signal (13, 14) is a reflection of the emitted ultrasonic signal at at least one object; f. assigning the signal group to an object in the vehicle's surroundings (30); g. comparing the first significance with the second significance, and assigning the signal group to the first echo group or the second echo group according to the comparison; determining a first ratio of signal groups to the first echo groups over a certain number of measurement cycles (21, 22, 23, 24, 25); determining a second ratio of the assignment of a signal group to the second echo group over a certain number of measurement cycles (21, 22, 23, 24, 25); The object height (H) is evaluated based on the first ratio and the second ratio, wherein the expected 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).

2. The method according to claim 1, characterized in that The significance of the first ultrasonic signal (13) and / or the significance of the second ultrasonic signal (14) is determined based on at least one parameter (A, R), the parameter comprising information contained in a received signal (ES), wherein the received signal is generated by the ultrasonic sensor (12) from ultrasonic signals received by the ultrasonic sensor during the measuring cycle, and the significance is determined by: A spatial area extending from the ultrasonic sensor to the maximum working range of the ultrasonic sensor is divided into a plurality of continuous and successive partial areas (T1, T2, T3), and 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 parameter group based on the positioning of the partial area (T1, T2, T3) in which the corresponding ultrasonic signal appears.

3. The method according to any one of claims 1 to 2, characterized in that The significance of each received ultrasonic signal is evaluated using 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 a specific significance level to the ultrasonic signal.

4. The method according to claim 3, characterized in that 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 that the ultrasonic signal (13, 14) comes from the reflection of the emitted ultrasonic signal at at least one object (30), wherein the significance level "medium" corresponds to a medium-sized probability that the ultrasonic signal (13, 14) comes from the reflection of the emitted ultrasonic signal at at least one object (30), wherein the significance level "high" corresponds to a high probability that the ultrasonic signal comes from the reflection of the emitted ultrasonic signal (13, 14) at at least one object (30), and wherein the significance level "very high" corresponds to a very high probability that the ultrasonic signal (13, 14) comes from the reflection of the emitted ultrasonic signal at at least one object (30).

5. The method according to claim 4, characterized in that If the difference between the first significance and the second significance is small or if the first ultrasonic signal has a high significance, a signal group including the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the first echo group.

6. The method according to claim 4, characterized in that If the first ultrasonic signal has a low significance and the second ultrasonic signal has a higher significance than the first ultrasonic signal, a signal group including the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the second echo group.

7. The method according to any one of claims 1 to 2, characterized in that The signal set is assigned to an object (30) in the vehicle's surroundings by means of trilateration.

8. The method according to any one of claims 1 to 2, characterized in that The object height (H) is evaluated by comparing a determined first ratio of a signal group assigned to the first echo group with a first threshold value, and / or comparing a determined second ratio of a signal group assigned to the second echo group with a second threshold value, and / or comparing a sum of the first ratio and the second ratio with a third threshold value.

9. The method according to claim 8, characterized in that The third threshold is greater than the first threshold, and the third threshold is greater than the second threshold.

10. The method according to any one of claims 1 to 2, characterized in that The object height is evaluated as to whether the object can be safely driven over by a vehicle.

11. The method according to any one of claims 1 to 2, characterized in that The evaluation of the height (H) of the object based on the first ratio and the second ratio is performed only when the vehicle is moving, or a higher evaluation threshold is used during the evaluation when the vehicle is stationary.

12. The method according to claim 2, characterized in that: The significance of the first ultrasonic signal (13) and / or the significance of the second ultrasonic signal (14) is determined based on the amplitude (A) and / or the correlation coefficient (R) of the received signal (ES).

13. The method according to claim 5, characterized in that If the two ultrasonic signals have the same significance level, a signal group comprising the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the first echo group.

14. The method according to claim 5, characterized in that If the first ultrasonic signal has the significance level "very high", a signal group including the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the first echo group.

15. The method according to claim 6, characterized in that If the first ultrasonic signal has a significance level of "low" and the second ultrasonic signal has a significance level of "high" or "very high", a signal group including the first ultrasonic signal (13) and the second ultrasonic signal (14) is assigned to the second echo group.

16. An ultrasonic sensor system for a vehicle, comprising: at least one ultrasonic sensor (12) configured to emit an ultrasonic signal and detect an ultrasonic signal (13, 14) reflected by the emitted ultrasonic signal at an object (30); A computing unit is configured to carry out the method according to claim 1 for evaluating an object height (H) of the object (30) by means of the ultrasonic signal detected by the ultrasonic sensor (12).

17. A computer program product comprising a program code for performing the method according to any one of claims 1 to 15 when the program code is executed on a computer.

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