A method for calibrating ultrasonic sensors in an ultrasonic-based driver assistance system of a vehicle, and the vehicle

Abstract

This invention provides a method for calibrating ultrasonic sensors in an ultrasonic-based driver assistance system for a vehicle. [Solution] The vehicle 10 is placed on the ground 22. This method comprises: a) setting or determining the height 26 of the ultrasonic sensor 16 from the ground 22; b) transmitting several ultrasonic pulses 30, each ultrasonic pulse 30 being transmitted while forming a main lobe 32 and a sub-lobe 34, with the sub-lobe 34 being transmitted so as to face the ground 22; c) detecting a plurality of sub-lobe-ground-echoes 44; and d) determining and saving a correction value for the elevation angle detection by the ultrasonic sensor 16, and / or determining and saving a correction value for the azimuth angle detection by the ultrasonic sensor 16, based on some of the plurality of sub-lobe-ground-echoes 44 detected in step c).

Description

Technical Field

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[0001] The present invention relates to a method for calibrating an ultrasonic sensor of an ultrasonic-based driver assistance system of a vehicle and to a vehicle.

Background Art

[0002] Vehicles often equip an ultrasonic-based driver assistance system, especially in the form of ultrasonic-based parking assistance, having a plurality of, for example, four or eight ultrasonic sensors arranged on the vehicle while forming an ultrasonic sensor array.

[0003] A typical ultrasonic sensor for ultrasonic-based parking assistance emits an ultrasonic pulse, which is reflected as an echo by an object. This echo can be detected by the ultrasonic sensor, and the distance between the ultrasonic sensor and the object can be determined based on the duration of the time period from the emission of the ultrasonic pulse to the reception of the echo. In addition to this, the ultrasonic sensor can detect the elevation angle and azimuth angle at which the echo impinges, thereby enabling accurate determination of the position of the object.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present invention is to provide a method for calibrating an ultrasonic sensor of an ultrasonic-based driver assistance system of a vehicle that enables calibration of the ultrasonic sensor with high accuracy. Furthermore, the problem of the present invention is to provide a vehicle configured to implement this method.

Means for Solving the Problems

[0005] The problem underlying the present invention is solved by a method having the constituent features of claim 1 and also by a vehicle having the constituent features of claim 10. Preferred developments of the present invention are described in the dependent claims.

[0006] The method according to the present invention is used to calibrate an ultrasonic sensor of an ultrasonic-based driver assistance system in a vehicle. The vehicle is placed on the ground. The method includes the following steps: a) setting or determining the height of the ultrasonic sensor from the ground, in particular the mounting height; b) transmitting several, for example, 1 to 50, ultrasonic pulses, each ultrasonic pulse being transmitted in such a way that it forms a primary lobe and a secondary lobe, with each secondary lobe facing the ground; c) detecting a plurality of, for example, 5 to 100 secondary lobe-ground-echoes with the ultrasonic sensor; and d) determining and storing a correction value for the elevation angle detection by the ultrasonic sensor and / or determining and storing a correction value for the azimuth angle detection by the ultrasonic sensor, based on some, in particular all, of the plurality of secondary lobe-ground-echoes detected in step c).

[0007] The use of secondary lobes for ultrasonic sensor calibration offers the advantage of achieving exceptionally accurate calibration. In particular, because secondary lobes can have a shorter width compared to the primary lobe, they strike the ground in a narrower area and are reflected as secondary lobe-ground-echoes. Therefore, any detected secondary lobe-ground-echoes that do not originate from this narrow area can be excluded. This allows for the reliable identification and exclusion of measurements containing errors, thereby enabling more accurate calibration.

[0008] Another aspect of this method is that, traditionally, secondary lobes have been considered undesirable, and various strategies have been developed to typically avoid, or even suppress, them. In contrast, in the implementation of this method, secondary lobes are generated and used for calibration.

[0009] Another aspect of this method is that the use of secondary lobe-ground echoes for ultrasonic sensor calibration can be particularly low-cost and highly accurate.

[0010] Another aspect of this method is that it may be possible to implement it while the vehicle is in use, for example, during parking operations.

[0011] The ultrasonic sensor can be calibrated by saving correction values. After calibration, the elevation angle and / or azimuth angle of subsequent echoes can be detected with special precision by the ultrasonic sensor using these correction values.

[0012] The ground may be flat. The ground cannot have steps. The ground cannot have an extension that is inclined with respect to the long axis of the vehicle. Preferably, the ground can extend parallel to the long axis of the vehicle.

[0013] The secondary lobe-ground-echo can be understood as the proportion of the ultrasonic pulse forming the secondary lobe that is reflected by the ground. The secondary lobe is reflected by the ground at the reflection point and can propagate as a secondary lobe-ground-echo.

[0014] Each secondary lobe, ground, and echo can strike the ultrasonic sensor at an elevation angle, which ranges from 65° to 75°, particularly between 70° and 72°.

[0015] The determination of the height of the ultrasonic sensor from the ground in step a) may include transmitting an ultrasonic pulse towards the ground at the maximum elevation angle of the ultrasonic sensor and receiving a ground echo, and the determination of the height of the ultrasonic sensor from the ground is based on the duration of the measured time period from the transmission of the ultrasonic pulse to the reception of the ground echo.

[0016] The generation of some ultrasonic pulses in step b) can be performed by an ultrasonic sensor.

[0017] The transmission in step b) can be performed so that each main lobe is facing away from the ground.

[0018] The method may include each of the following steps: f) detecting the temperature during the execution of at least one of steps b) and c), and g) saving the temperature detected in step f).

[0019] The correction values ​​determined for the elevation angle detection in step d), and / or the correction values ​​determined for the azimuth angle detection, may be temperature-dependent.

[0020] The ultrasonic sensor can have a detection range of 180°. This allows the ultrasonic sensor to detect echoes whose elevation angle and / or azimuth angle are within the range of +90° to -90°.

[0021] This method may include the following steps: checking a correction value for detecting the elevation angle, and checking a correction value for detecting the azimuth angle. This check can be performed using a reference object placed in front of the sensor at a defined angle.

[0022] After this method is implemented, the ultrasonic sensor can detect the elevation angle and / or azimuth angle of the echo, and the detected elevation angle is corrected by the correction value for the detected elevation angle determined in step d), and / or the detected azimuth angle is corrected by the correction value for the detected azimuth angle determined in step d).

[0023] In an advanced version of this method, the detection of multiple sub-lobe-ground-echoes in step c) includes measuring the amplitude of each sub-lobe-ground-echo. The determination of the correction value for the elevation angle detection and / or the correction value for the azimuth angle detection in step d) is performed depending on the amplitude of the sub-lobe-ground-echoes measured in step c). This has the advantage of being able to fade out artifacts. Furthermore, it can ensure a high signal-to-noise ratio.

[0024] For example, this method may, before step d), include determining, in particular selecting, the sublobe-ground echo whose amplitude measured in step c) is greater than a predetermined amplitude limit in the next step, h). The determination and storage of the correction value for elevation angle detection by the ultrasonic sensor in step d), and / or the determination and storage of the correction value for azimuth angle detection by the ultrasonic sensor, can be performed based on the sublobe-ground echo determined in step h). The remaining sublobe-ground echoes can be faded out. Fading out of sublobe-ground echoes can be understood as the faded-out sublobe-ground echoes not being considered for the determination of the correction value in step d).

[0025] In an advanced form of this method, the detection of multiple sub-lobe-ground-echoes in step c) includes measuring the elevation angle and / or azimuth angle of each sub-lobe-ground-echo, and measuring the duration of the time period from the transmission of the ultrasonic pulse generating the sub-lobe-ground-echo to the reception of the sub-lobe-ground-echo by the ultrasonic sensor. The determination of the correction value for the elevation angle detection in step d) is based on the elevation angle and duration measured in step c). Alternatively, the determination of the correction value for the azimuth angle detection in step d) is based on the azimuth angle and duration measured in step c). This has the advantage of allowing the ultrasonic sensor to be calibrated in a particularly simple manner.

[0026] For example, from this duration, the distance between the ultrasonic sensor and the ground reflection point can be calculated. The reflection point may be a point on the ground where the sidelobe is reflected. The sidelobe-ground-echo can propagate from the reflection point. The determination of the correction value for the detection of the elevation angle in step d) and / or the determination of the correction value for the detection of the azimuth angle can be performed based on the calculated distance.

[0027] In an advanced form of the method, the method has, before step d), the following step, e) determining, in particular selecting, the elevation angle and / or the azimuth angle measured for the sidelobe-ground-echo which the duration measured in step c) above represents, particularly corresponds to, represents, or describes a distance between the ultrasonic sensor and the ground having a value within a predetermined distance value range. The determination of the correction value for the detection of the elevation angle in step d) and / or the determination of the correction value for the detection of the azimuth angle is performed based on the elevation angle and / or the azimuth angle determined, in particular selected, in step e).

[0028] By limiting the sidelobe-ground-echo in step e), there is an advantage that the requirements related to the ground for the success of calibration are reduced. In particular, the area of the ground from which the sidelobe-ground-echo used for calibration is derived can be reduced in terms of its size. Only the area of the ground from which the sidelobe-ground-echo used for calibration is derived can meet the requirements related to the ground for the success of calibration. For example, the method can successfully calibrate the ultrasonic sensor even when only the area of the ground from which the sidelobe-ground-echo used for calibration is derived is formed flat.

[0029] In an advanced form of this method, the determination of the correction value for the elevation angle detection in step d) and / or the determination of the correction value for the azimuth angle detection are based on the measured elevation angle and / or azimuth angle of the sidelobe-ground echo, where the elevation angle has a value within a predetermined elevation angle value range and / or the azimuth angle has a value within a predetermined azimuth angle value range. Thereby, there is an advantage that outliers outside the predetermined elevation angle value range and / or azimuth angle value range can be faded out. Thereby, for example, measurement errors generated based on disturbances can also be faded out. Disturbances can occur, for example, due to small objects, holes in the road, or the influence from other ultrasonic sensors.

[0030] In an advanced form of this method, the determination of the correction value for the elevation angle detection in step d) includes calculating the elevation angle median value and calculating the elevation angle standard deviation based on several measured elevation angles. As an alternative or addition thereto, the determination of the correction value for the azimuth angle detection in step d) includes calculating the azimuth angle median value and calculating the azimuth angle standard deviation based on several measured azimuth angles.

[0031] The elevation angle median value and the elevation angle standard deviation can be calculated for a predetermined number, for example 30 or 50, of sidelobe-ground echoes. As an alternative or addition thereto, the elevation angle median value and the elevation angle standard deviation can be calculated for a predetermined travel distance or time interval. The azimuth angle median value and the azimuth angle standard deviation can be calculated for a predetermined number, for example 30 or 50, of sidelobe-ground echoes. As an alternative or addition thereto, the azimuth angle median value and the azimuth angle standard deviation can be calculated for a predetermined travel distance or time interval.

[0032] In step d), the elevation angle product can be saved as a correction value for detecting the elevation angle, and / or the azimuth angle product can be saved as a correction value for detecting the azimuth angle. The elevation angle product can be formed by multiplying the elevation angle median by a predetermined elevation angle weighting coefficient. The azimuth angle product can be formed by multiplying the azimuth angle median by a predetermined azimuth angle weighting coefficient.

[0033] The elevation angle and weighting coefficient can have values ​​within the range of -1 to +1, preferably +0.3 to +0.7. The azimuth angle and weighting coefficient can have values ​​within the range of -1 to +1, preferably +0.3 to +0.7.

[0034] The elevation angle weighting coefficient and / or azimuth angle weighting coefficient may be negative. This allows the correction value for elevation angle detection to have an inverted sign, particularly an inverted sign, relative to the elevation angle median, and / or the correction value for azimuth angle detection to have an inverted sign, particularly an inverted sign, relative to the azimuth angle median. This allows the correction of the measured elevation angle and / or azimuth angle to be performed by addition.

[0035] In an advanced form of this method, the method includes the calculation of the elevation angle difference and / or azimuth angle difference for each sub-lobe ground echo determined in step e) before step d). Each elevation angle difference is formed by subtracting the measured elevation angle from a given target elevation angle. Each azimuth angle difference is formed by subtracting the measured azimuth angle from a given target azimuth angle. The median elevation angle is the median of the elevation angle differences, and the standard deviation of the elevation angle is the standard deviation of the elevation angle differences. The median azimuth angle is the median of the azimuth angle differences, and the standard deviation of the azimuth angle is the standard deviation of the azimuth angle differences. This has the advantage of enabling particularly simple determination of correction values ​​for elevation angle detection and / or particularly simple determination of correction values ​​for azimuth angle detection.

[0036] In an advanced version of this method, in step d), the elevation median, preferably inverted and especially having an inverted positive / negative sign, is stored as a correction value for elevation detection. As an addition or alternative, in step d), the azimuth median, preferably inverted and especially having an inverted positive / negative sign, is stored as a correction value for azimuth detection. For example, the elevation median may have a positive value, which is stored as a negative value as a correction value for elevation detection.

[0037] In an advanced version of this method, if the elevation angle standard deviation is smaller than a predetermined maximum elevation angle standard deviation, a correction value for elevation angle detection is saved. As an addition or alternative, if the azimuth angle standard deviation is smaller than a predetermined maximum azimuth angle standard deviation, a correction value for azimuth angle detection is saved in step d).

[0038] This has the advantage of preventing the storage of erroneous correction values ​​for elevation angle detection and / or erroneous correction values ​​for azimuth angle detection. If the elevation angle standard deviation is greater than or equal to a predetermined maximum elevation angle standard deviation, at least steps b) and c) can be repeated. If the azimuth angle standard deviation is greater than or equal to a predetermined maximum azimuth angle standard deviation, at least steps b) and c) can be repeated.

[0039] A vehicle, in particular an automobile, according to the present invention has an ultrasonic-based driver assistance system configured to carry out the method described above.

[0040] An ultrasonic-based driver assistance system may be configured as an ultrasonic-based parking helper.

[0041] An ultrasonic-based driver assistance system may have a control device configured to carry out the method described above.

[0042] Next, possible embodiments of the present invention will be described with reference to the attached drawings. The drawings are as follows: [Brief explanation of the drawing]

[0043] [Figure 1] This is a schematic plan view showing a vehicle equipped with an ultrasonic-based driver assistance system. [Figure 2] This is a schematic side view of the vehicle shown in Figure 1. [Figure 3] This is another schematic side view showing the vehicle in Figure 1. [Figure 4] This is a schematic rear view of the vehicle shown in Figure 1. [Figure 5] Figure 1 is a schematic plan view showing the ultrasonic sensor of the ultrasonic-based driver assistance system. [Modes for carrying out the invention]

[0044] Figure 1 shows a vehicle 10 having an ultrasonic-based driver assistance system 12. The ultrasonic-based driver assistance system 12 comprises a control device 14 and eight ultrasonic sensors 16. The ultrasonic sensors 16 are signal-engineered to the control device 14.

[0045] The ultrasonic-based driver assistance system 12 is configured as an ultrasonic-based parking assist system. The ultrasonic sensor 16 is located at the rear of the vehicle 10. The ultrasonic sensor 16 may be arranged as an ultrasonic sensor array 18.

[0046] The ultrasonic-based driver assistance system 12 is configured to implement a method for calibrating the ultrasonic sensors 16 of an ultrasonic sensor array 18. In particular, the ultrasonic sensors 16 are sequentially calibrated by this method.

[0047] Figure 2 shows a vehicle 10 having ultrasonic sensors 16 of an ultrasonic sensor array 18 in the xz plane extending through the longitudinal and perpendicular directions of the vehicle 10. Below, as an example, the calibration of the ultrasonic sensor 16 shown in Figure 2 using this method will be described. Other ultrasonic sensors 16 can also be calibrated in accordance with this method.

[0048] The vehicle 10 is positioned on the ground 22. The ground 22 is flat. The ground 22 extends parallel to the long axis 24 of the vehicle 10.

[0049] The ultrasonic sensor 16 is spaced above the ground 22 at a height 26. This height 26 may be referred to as the mounting height. The value of the height 26 is stored in the storage device 28 of the control device 14.

[0050] In alternative embodiments not shown, the control device determines the height of the ultrasonic sensor from the ground. To this end, the control device controls the ultrasonic sensor to emit ultrasonic pulses toward the ground at the maximum elevation angle. The control device can determine the height of the ultrasonic sensor from the ground based on the measured duration of the time between the emission of the ultrasonic pulse by the ultrasonic sensor and the reception of the ground echo of the ultrasonic pulse having the shortest duration among all received ground echoes.

[0051] Figure 2 shows an ultrasonic sensor 16 configured to emit ultrasonic pulses 30.

[0052] The ultrasonic sensor 16 emits several ultrasonic pulses 30, for example, from 1 to 50. The ultrasonic sensor 16 emits ultrasonic pulses 30 such that each ultrasonic pulse 30 forms a main lobe 32 and a sub-lobe 34. The sub-lobe 34 is pointed towards the ground 22. The main lobe 32 is not pointed towards the ground 22. In other words, the main lobe 32 is pointed away from the ground 22.

[0053] The secondary robe 34 has a width of 36. The primary robe 32 has a width of 38. The width of the secondary robe 34 (36) is smaller than the width of the primary robe 32 (38). As a result, the secondary robe 34 reaches the ground 22 in a relatively narrow area 40.

[0054] A proportion of the ultrasonic pulses 30 forming the sub-lobe 34 strike the ground 22 and are reflected by the ground 22 as sub-lobe-ground echoes 44. A proportion of the single ultrasonic pulses 30 forming the sub-lobe 34 can be reflected from the ground 22 at one or more reflection points 42, thereby generating one or more sub-lobe-ground echoes 44. The reflection points 42 are separated from the ultrasonic sensor 16 by a reflection point interval 46.

[0055] Figure 3 shows the vehicle 10 in another side view similar to Figure 2, and for the sake of clarity, the main lobe 32 and secondary lobe 34 of the ultrasonic pulse 30 are not shown. Figure 3 shows that the secondary lobe, ground, and echo 44 strike the ultrasonic sensor 16 at an elevation angle 48.

[0056] Figure 4 shows the vehicle 10 from Figures 1 to 3 in a rear view. For ease of viewing, only the ultrasonic sensor 16 shown in Figure 2 is shown, and the other ultrasonic sensors 16 are faded out. The secondary lobe, ground, and echo 44 strike the ultrasonic sensor 16 at the azimuth angle 52 shown in Figure 5.

[0057] The ultrasonic sensor 16 is configured to detect sublobe-ground echoes 44 of several ultrasonic pulses 30. Detection of the sublobe-ground echoes 44 includes measuring the amplitude of each sublobe-ground echo 44, measuring the elevation angle 48 of the sublobe-ground echo 44, measuring the azimuth angle 52 of the sublobe-ground echo 44, and measuring the duration of the time period from the emission of the ultrasonic pulse 30 that generates the sublobe-ground echo 44 to the detection of the sublobe-ground echo 44 by the ultrasonic sensor 16. In addition, the ultrasonic sensor 16 detects the temperature when the sublobe-ground echo 44 is detected.

[0058] The control device 14 determines and specifically selects sub-lobes, grounds, and echoes 44 whose measured amplitude is greater than a predetermined amplitude limit. The remaining sub-lobes, grounds, and echoes 44 are faded out. Sub-lobes, grounds, and echoes 44 that have been faded out are not included in the consideration after that point.

[0059] Figure 5 shows a schematic plan view of the ultrasonic sensor 16. The control device 14 determines and specifically selects sublobes, ground, and echoes 44 whose reflection points 42 are within a predetermined distance and value range 54.

[0060] To this end, the control device 14 calculates the distance between the ultrasonic sensor 16 and the reflection point 42 from the duration of the time period from the transmission of the ultrasonic pulse 30 to the detection of the secondary lobe / ground / echo 44. Based on a predetermined height 26 of the ultrasonic sensor 16 and the calculated distance between the ultrasonic sensor 16 and the reflection point 42, the control device 14 calculates the interval 46 of the reflection points 42. The control device 14 compares this interval 46 to determine whether it is greater than a predetermined lower limit value 56 and less than a predetermined upper limit value 58. The predetermined distance-value range 54 is delimited by the lower limit value 56 and the upper limit value 58.

[0061] If the reflection point 42 is outside the predetermined distance / value range 54, the other secondary lobes / ground / echoes 44 fade out.

[0062] The control device 14 calculates the elevation angle difference for each determined sub-lobe / ground / echo 44 by subtracting the elevation angle 48 measured from a predetermined target elevation angle. The target elevation angle may be, for example, 71°. The control device 14 also calculates the azimuth angle difference for each determined sub-lobe / ground / echo 44 by subtracting the azimuth angle 52 measured from a predetermined target azimuth angle. The target azimuth angle may be, for example, 90°.

[0063] The control device 14 determines whether the sublobe / ground / echo 44 has an elevation angle / difference within a predetermined range, and / or an azimuth angle / difference within a predetermined range. Any other sublobe / ground / echo 44 is faded out. This has the advantage of fading out abnormal values ​​or erroneous measurements.

[0064] The control device 14 calculates the median elevation and standard deviation of the elevation for the elevation difference of the determined secondary lobes, ground, and echoes 44 that have not yet faded out. The median elevation and standard deviation of the elevation are calculated, for example, when the number of determined secondary lobes, ground, and echoes 44 is greater than or equal to a predetermined value, for example, 30 or 50. The median elevation and standard deviation of the elevation can be calculated, for example, when the number of determined secondary lobes, ground, and echoes 44 is greater than or equal to a predetermined value, for example, 30 or 50.

[0065] The control device 14 compares the elevation angle standard deviation value with a predetermined maximum elevation angle standard deviation value. If the elevation angle standard deviation value is greater than the predetermined maximum elevation angle standard deviation value, the control device 14 stops the method of calibrating the elevation angle. In the illustrated embodiment, the elevation angle standard deviation value is less than the predetermined maximum elevation angle standard deviation value, and therefore, the determination of the correction value for detecting the elevation angle 48 continues.

[0066] The control device 14 compares the value of the azimuth angle standard deviation with a predetermined maximum azimuth angle standard deviation. If the value of the azimuth angle standard deviation is greater than the predetermined maximum azimuth angle standard deviation, the control device 14 stops the method of calibrating the azimuth angle. In the illustrated embodiment, the value of the azimuth angle standard deviation is less than the predetermined maximum azimuth angle standard deviation, and therefore, the determination of the correction value for detecting the azimuth angle 52 continues.

[0067] The control device 14 calculates the elevation angle, temperature, and mean value based on the measured temperature detected during the detection of the secondary lobe, ground, and echo 44, which are used for calculating the elevation angle, median, and elevation angle, standard deviation. The control device 14 calculates the azimuth angle, temperature, and mean value based on the measured temperature detected during the detection of the secondary lobe, ground, and echo 44, which are used for calculating the azimuth angle, median, and azimuth angle, standard deviation.

[0068] The control device 14 calculates the azimuth angle product by multiplying the median elevation angle by a predetermined elevation angle weighting coefficient. The elevation angle weighting coefficient can have a value within the range of -1 to +1, preferably +0.3 to +0.7. The control device 14 calculates the azimuth angle product by multiplying the median azimuth angle by a predetermined azimuth angle weighting coefficient. The azimuth angle weighting coefficient can have a value within the range of -1 to +1, preferably +0.3 to +0.7.

[0069] The control device 14 stores the elevation angle-product as a correction value for the detection of the elevation angle 48 by the ultrasonic sensor 16, and / or the azimuth angle-product as a correction value for the detection of the azimuth angle 52 by the ultrasonic sensor 16, in the storage device 28 and / or the storage device of the ultrasonic sensor 16.

[0070] The control device 14 stores the elevation angle, temperature, average value, and / or azimuth angle, temperature, and average value in the storage device 28 and / or the storage device of the ultrasonic sensor 16.

[0071] The calibration of the ultrasonic sensor 16 is completed when the elevation angle product and / or azimuth angle product are saved.

[0072] This method is repeated for the remaining ultrasonic sensors 16 in the ultrasonic sensor array 18.

[0073] After calibration, the ultrasonic sensor 16 can detect the echo. At this time, the measured elevation angle and / or azimuth angle of the echo are corrected by the amount of the stored elevation angle-product and / or stored azimuth angle-product. This correction can be made, for example, by creating a difference between the measured elevation angle and the stored elevation angle-product, and / or by creating a difference between the measured azimuth angle and the stored azimuth angle-product. This allows the elevation angle and / or azimuth angle of the echo to be detected with particular accuracy.

[0074] In embodiments not shown, correction values ​​for elevation angle detection and azimuth angle detection can be stored separately for different temperature ranges. This allows different correction values ​​to be applied to different temperature ranges. For example, temperature can be measured while elevation angle and / or azimuth angle are being detected, and the correction values ​​for elevation angle detection and / or azimuth angle detection can be determined based on the measured temperature, and the measured elevation angle and / or azimuth angle can be corrected accordingly.

Claims

1. A method for calibrating an ultrasonic sensor (16) of an ultrasonic-based driver assistance system (12) of a vehicle (10), wherein the vehicle (10) is placed on the ground (22), and the method comprises the following steps: a) Setting the height (26) of the ultrasonic sensor (16) from the ground (22), or determining the height (26) of the ultrasonic sensor (16) from the ground (22), b) Transmitting several ultrasonic pulses (30), wherein each ultrasonic pulse (30) is transmitted while forming a main lobe (32) and a secondary lobe (34), and the transmission is carried out such that the secondary lobe (34) faces the ground (22). c) Detecting multiple secondary lobes, ground, and echoes (44), and d) Based on some of the multiple sub-lobes, ground, and echoes (44) detected in step c), determine and save a corrected value for the detection of the elevation angle (48) by the ultrasonic sensor (16), and / or determine and save a corrected value for the detection of the azimuth angle (52) by the ultrasonic sensor (16). Methods that include...

2. The detection of the plurality of sub-lobe ground echoes (44) in step c) includes measuring the amplitude of each sub-lobe ground echo (44), The determination of the correction value for the detection of the elevation angle (48) in step d) and / or the determination of the correction value for the detection of the azimuth angle (52) is performed depending on the amplitude of the secondary lobe ground echo (44) measured in step c). The method according to claim 1.

3. The detection of the plurality of sublobe-ground echoes (44) in step c) includes, for each sublobe-ground echo (44), measuring the elevation angle (48) and / or the azimuth angle (52) of the sublobe-ground echo (44), and measuring the duration of the time period from the transmission of the ultrasonic pulse (30) that generates the sublobe-ground echo (44) to the reception of the sublobe-ground echo (44) by the ultrasonic sensor (16), The determination of the correction value for the detection of the elevation angle (48) in step d) is made based on the elevation angle (48) measured in step c) and the measured duration, and / or The determination of the correction value for the detection of the azimuth angle (52) in step d) is performed based on the azimuth angle (52) measured in step c) and the measured duration. The method according to claim 1 or 2.

4. The method has the following steps prior to step d): e) determining the measured elevation angle (48) and / or azimuth angle (52) for a sublobe ground echo (44) that represents the distance between the ultrasonic sensor (16) and the ground (22), wherein the duration measured in step c) has a value within a predetermined distance-value range, particularly by selecting The determination of the correction value for the detection of the elevation angle (48) and / or the determination of the correction value for the detection of the azimuth angle (52) in step d) is performed on a particularly selected elevation angle (48) and / or azimuth angle (52) determined in step e). The method according to claim 3.

5. The determination of the correction value for the detection of the elevation angle (48) and / or the determination of the correction value for the detection of the azimuth angle (52) in step d) is as follows: The measurement is performed based on the measured elevation angle (48) and / or azimuth angle (52) of the sublobe ground echo (44), wherein the elevation angle (48) is within a predetermined elevation angle-value range, and / or the azimuth angle (52) is within a predetermined azimuth angle-value range. The method according to claim 3 or 4.

6. The determination of the corrected value for the detection of the elevation angle (48) in step d) includes calculating the elevation median and the elevation standard deviation based on several measured elevation angles (48). The determination of the corrected value for the detection of the azimuth angle (52) in step d) includes calculating the azimuth angle median and the azimuth angle standard deviation based on several measured azimuth angles (52). The method according to any one of claims 3 to 5.

7. The method has the following step before step d): calculating the elevation angle difference and / or azimuth angle difference for each sub-lobe ground echo (44) determined in step e), Each elevation angle and difference is formed by subtracting the measured elevation angle (48) from a predetermined target elevation angle. Each azimuth angle difference is formed by subtracting the measured azimuth angle (52) from a predetermined target azimuth angle. The median elevation angle is the median of the elevation angle difference, and the standard deviation of the elevation angle is the standard deviation of the elevation angle difference. The median azimuth angle is the median of the difference in azimuth angles, and the standard deviation of azimuth angles is the standard deviation of the difference in azimuth angles. The method according to claim 6.

8. In step d) above, the elevation angle median, in particular having an inverted positive / negative sign, is stored as a corrected value for detecting the elevation angle (48), and / or In step d) above, the azimuth angle median, which in particular has an inverted positive / negative sign, is stored as a corrected value for detecting the azimuth angle (52). The method according to claim 7.

9. In step d), if the elevation angle standard deviation is smaller than a predetermined maximum elevation angle standard deviation, the correction value for the detection of the elevation angle (48) is saved, and / or In step d), if the azimuth angle standard deviation is smaller than a predetermined maximum azimuth angle standard deviation, the corrected value for the detection of the azimuth angle (52) is saved. The method according to any one of claims 6 to 8.

10. In vehicles (10), especially automobiles, An ultrasonic-based driver assistance system (12) configured to carry out the method described in any one of the prior claims. A vehicle (10) having the following features.

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