Method for calibrating an ultrasonic sensor of an ultrasonic-based driver assistance system of a vehicle and vehicle

Abstract

Method for calibrating, in particular an elevation angle (32), an ultrasonic sensor (16, 20) of an ultrasonic-based driver assistance system (12) of a vehicle (10).

Description

State of the art

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

[0002] Vehicles often have ultrasonic-based driver assistance systems, particularly in the form of ultrasonic-based parking aids, with several, for example 4 or 8, ultrasonic sensors arranged on the vehicle in a row.

[0003] A typical ultrasonic sensor in an ultrasonic parking aid emits an ultrasonic pulse that is reflected by an object as an echo. The ultrasonic sensor can detect this echo, and the distance between the sensor and the object can be determined based on the time interval between the emission of the ultrasonic pulse and the reception of the echo. Additionally, the ultrasonic sensor can detect the incident elevation and azimuth angles of the echo. Disclosure of the invention

[0004] The invention aims to provide a method for calibrating an ultrasonic sensor of an ultrasonic-based driver assistance system of a vehicle, enabling high-accuracy calibration of the ultrasonic sensor. Furthermore, the present invention aims to provide a vehicle equipped to perform the method.

[0005] The problem underlying the invention is solved by a method with the features of claim 1 and by a vehicle with the features of claim 10. Advantageous embodiments of the invention are specified in the dependent claims.

[0006] A method according to the invention is suitable for calibrating, in particular the elevation angle, of an ultrasonic sensor of an ultrasonic-based driver assistance system of a vehicle, wherein the vehicle is placed on a ground. The method comprises the steps of: a) specifying a height, in particular an installation height, of the ultrasonic sensor from the ground or determining the height of the ultrasonic sensor from the ground; b) detecting a plurality, for example 5 to 100, of ground echoes of an ultrasonic pulse from the ground with the ultrasonic sensor, wherein the detection of the ground echoes for each ground echo comprises measuring an elevation angle of the ground echo and measuring the duration of a period between the emission of the ultrasonic pulse and the reception of the ground echo with the ultrasonic sensor; c) determining target elevation angles of the ground echoes based on the durations measured in step b).d) Determining deviations of the elevation angles of the ground echoes measured in step b) from the target elevation angles of the ground echoes; and e) Determining a correction value for detecting the elevation angle with the ultrasonic sensor based on the deviations determined in step d).

[0007] Advantageously, using ground echoes allows for particularly cost-effective and highly accurate calibration of ultrasonic sensors for measuring elevation angles. Calibration of the ultrasonic sensors can be achieved by determining the correction values ​​for measuring elevation angles with the ultrasonic sensor. After calibration, the elevation angles of further echoes can be detected with high precision using the ultrasonic sensor and these correction values.

[0008] Another aspect of the invention is that the method can be carried out while using the ultrasonic sensor, for example while detecting an object.

[0009] Determining the height of the ultrasonic sensor from the ground in step a) can involve emitting an ultrasonic pulse towards the ground at the sensor's maximum elevation angle and receiving a ground echo. The height of the ultrasonic sensor from the ground is then determined based on the measured duration of the time between emitting the ultrasonic pulse and receiving the ground echo. The maximum elevation angle of the ultrasonic sensor can, for example, be 80°.

[0010] The procedure may include the step: r) Determine for each ground echo a distance of a reflection point of the ground echo, at which the ultrasonic pulse was reflected from the ground, from the ultrasonic sensor based on the duration of the period between the emission of the ultrasonic pulse and the reception of the ground echo with the ultrasonic sensor measured in step b), wherein the determination of the target elevation angles in step c) for each ground echo is based on the distance determined in step r) and the height specified in step a).

[0011] A ground echo whose reflection point is located at a distance from the ultrasonic sensor that is greater than a certain distance, for example 3 m (meters), can be filtered out.

[0012] Determining the deviations in step d) can be done for each ground echo by calculating the difference between the measured elevation angle and the target evolution angle.

[0013] Determining the correction value in step e) can be done by forming a median value or a mean value of the deviations determined in step d).

[0014] The procedure can include, after step b), the following step: s) filtering the ground echoes detected in step b) such that those ground echoes with a low signal-to-noise ratio, amplitude, significance, and / or correlation coefficients are filtered out. The filtering in step s) can be performed using an echo attribute, a threshold, and / or a model fitted by machine learning.

[0015] The floor can be level. The floor can be level. The floor can be level. The floor can be level with respect to the longitudinal axis of the vehicle. Preferably, the floor can be parallel to the longitudinal axis of the vehicle.

[0016] If the ultrasonic sensor detects ground echoes and other echoes, for example from objects, the procedure may include the following step before step d): filtering the ground echoes by identifying the echoes from the objects and filtering out the echoes from the objects.

[0017] After executing the procedure, the ultrasonic sensor can detect the elevation angle of an echo, the detected elevation angle being corrected by the correction value determined in step e). Advantageously, this allows elevation angles to be detected more precisely with the ultrasonic sensor.

[0018] In a further development of the method, detecting the plurality of ground echoes in step b) comprises detecting a plurality of ground echoes from a plurality, for example, 5 to 100, of ultrasonic pulses. The method comprises the following steps: f) assigning each deviation determined in step d) to a distance range of the ultrasonic sensor, such that a plurality of deviations determined in step d) are assigned to each distance range; and g) calculating a mean value of the deviations for each distance range. Determining the correction value in step e) is based on the mean values ​​of the deviations calculated in step g).

[0019] The ultrasonic sensor can, for example, have 4 to 10 distance ranges.

[0020] In a further development of the procedure, the process comprises the following steps: h) determining the variance of the deviations for each distance range; and i) determining a weighting factor based on the variance determined in step h) for each distance range. The correction value in step e) is determined by calculating the mean of the mean deviations calculated in step g), taking into account the weighting factors determined in step i).

[0021] The weighting factor can be inversely proportional to the variance value. For example, the weighting factor can be larger if the variance value is smaller. This advantageously allows deviations within a distance range that exhibit lower variance to be weighted more heavily.

[0022] In a further development of the procedure, the procedure includes the following step: j) Analyzing the mean values ​​calculated in step g) for the presence of an outlier and excluding the mean values ​​identified as outliers. Advantageously, this reduces the influence of inaccuracies, thereby enabling calibration of the ultrasonic sensor with particularly high accuracy.

[0023] An outlier can be identified in step j), for example, if a value of a slope in a course of means over the distance ranges differs from the values ​​of the other slopes by a factor of two.

[0024] In a further development of the procedure, the process includes the following step: k) Analyzing the mean values ​​calculated in step g) for the presence of a trend and / or a step, and terminating the procedure if a trend and / or a step is identified in the mean values. A trend and / or a step in the mean values ​​can occur due to the surface being unsuitable for the procedure for calibrating the ultrasonic sensor. Advantageously, this allows the procedure to be terminated if the vehicle is placed on such a surface.

[0025] In a further development of the procedure, the procedure includes the following step before step b): m) Emitting the ultrasound pulse and / or the plurality of ultrasound pulses using the ultrasound sensor. The echo detected in step b) can be a direct echo. A direct echo can be an echo detected by the ultrasound sensor that emitted the ultrasound pulse.

[0026] In a further development of the method, step b) involves detecting the majority of ground echoes using an additional ultrasonic sensor. Determining the correction value in step e) is based on the ground echoes detected in step b) by the additional ultrasonic sensor. Each ground echo detected by the additional ultrasonic sensor can be a cross-echo. A cross-echo can be an echo detected by an ultrasonic sensor that did not emit the ultrasonic pulse.

[0027] The preceding statements regarding the method with reference to the ground echoes detected by the ultrasonic sensor can apply accordingly to the ground echoes detected by the further ultrasonic sensor.

[0028] In a further development of the procedure, the procedure comprises the following steps: n) detecting a temperature during the execution of at least one of steps a) to e); and o) storing the correction value determined in step e) and the temperature detected in step n).

[0029] The correction value determined in step e) can be temperature-dependent. When the ultrasonic sensor is commissioned or after a reset, a temperature can be measured and the corresponding correction value loaded. The storage in step o) can be performed in the memory of a control unit for controlling the ultrasonic sensor.

[0030] In a further development of the procedure, the process includes the following step: p) Detecting an alignment error of the ultrasonic sensor by analyzing a history of the correction value determined in step e). Advantageously, the detection of the alignment error allows it to be determined whether a repair of the ultrasound-based driver assistance system is necessary.

[0031] The alignment error can occur, for example, due to an unintentional mechanical impact on the ultrasonic sensor, such as an accident.

[0032] Analyzing the history of the correction value determined in step e) can be an analysis of whether the values ​​of the correction value determined in step e) show a jump in the history.

[0033] The history of the correction value determined in step e) can contain 20 to 100 correction values.

[0034] The procedure may include the step: t) Issue a warning if an alignment error is detected in step p).

[0035] A vehicle according to the invention, in particular a motor vehicle, has an ultrasound-based driver assistance system which is configured to perform a previously described method.

[0036] The ultrasound-based driver assistance system can be designed as an ultrasound-based parking aid.

[0037] The ultrasound-based driver assistance system may include a control unit designed to perform the procedure described above.

[0038] Possible embodiments of the invention are explained below with reference to the accompanying drawings. These show: Fig. 1 A schematic top view of a vehicle with an ultrasound-based driver assistance system comprising an ultrasonic sensor array, Fig. 2 a schematic side view of the vehicle from Fig. 1, Fig. 3 A schematic top view of two ultrasonic sensors from the ultrasonic sensor series of Fig. 1, Fig. 4 a schematic representation of a table of the ultrasound-based driver assistance system of Fig. 1, and Fig. 5 An exemplary procedure for calibrating the ultrasonic sensors of the ultrasonic sensor series from Fig. 1.

[0039] Fig. Figure 1 shows a vehicle 10 with an ultrasound-based driver assistance system 12. The ultrasound-based driver assistance system 12 has a control unit 14 and eight ultrasound sensors 16. The ultrasound sensors 16 are connected to the control unit 14 via a signal connection.

[0040] The ultrasound-based driver assistance system 12 is designed as an ultrasound-based parking aid. The ultrasound sensors 16 are arranged at the rear of the vehicle 10. The ultrasound sensors 16 form an ultrasound sensor array 18.

[0041] The ultrasound-based driver assistance system 12 is designed to perform a procedure for calibrating an elevation angle of an ultrasonic sensor 16 of the ultrasonic sensor series 18.

[0042] Fig. Figure 2 shows the vehicle 10 with a first ultrasonic sensor 20 of the ultrasonic sensor series 18 in an xz-plane spanned by a longitudinal and a vertical direction of the vehicle 10. The vehicle 10 is placed on a floor 22. The floor 22 is flat. The floor 22 runs parallel to a longitudinal axis 24 of the vehicle 10.

[0043] The first ultrasonic sensor 20 is positioned at a height 26 above the base 22. This height 26 can be referred to as the installation height. A value for the height 26 is stored in a memory 28 of the control unit 14. At least one value for the heights of the remaining ultrasonic sensors 16 from the base 22 can be equal to or different from the height 26 of the first ultrasonic sensor 20. The values ​​for the heights of the remaining ultrasonic sensors 16 can be stored in the memory 28.

[0044] In an alternative embodiment not shown, the control unit determines the height of the first and second ultrasonic sensors from the ground. For this purpose, the control unit can activate the first ultrasonic sensor such that it emits an ultrasonic pulse towards the ground at its maximum evolution angle. The control unit can determine the height of the first ultrasonic sensor from the ground based on a measured duration of the time between the emission of the ultrasonic pulse and the reception of a ground echo of the ultrasonic pulse by the first ultrasonic sensor. Subsequently, the control unit can activate the second ultrasonic sensor such that it emits an ultrasonic pulse towards the ground at its maximum evolution angle.The control unit determines the height of the second ultrasonic sensor from the ground based on a measured duration of the period between the emission of the ultrasonic pulse and the reception of a ground echo of the ultrasonic pulse by the second ultrasonic sensor.

[0045] Each ultrasonic sensor 16 is designed to emit an ultrasonic pulse and a Fig. 2. Echo 30 of the ultrasonic pulse is shown as an example. Detecting the echo 30 involves measuring the elevation angle 32 of the echo 30 at which it strikes the ultrasonic sensor 16. The elevation angle 32 can be used to locate an object in the xz-plane.

[0046] Fig. Figure 2 shows that the first ultrasonic sensor is assigned 20 distance ranges. In the exemplary embodiment of the Fig. Figure 2 shows four distance ranges as examples. In an alternative embodiment not shown, the first ultrasonic sensor is assigned more or fewer distance ranges.

[0047] The first ultrasonic sensor 20 has a first distance range 34, a second distance range 36, a third distance range 38 and a fourth distance range 40.

[0048] Fig. Figure 3 shows a top view of the vehicle 10 during the execution of the procedure for calibrating the elevation angle of the first ultrasonic sensor 20 of the ultrasonic sensor series 18. A second ultrasonic sensor 42 of the ultrasonic sensor series 18 is arranged next to the first ultrasonic sensor 20.

[0049] The first ultrasonic sensor 20 emits a plurality, for example six, of ultrasonic pulses in succession. The ultrasonic pulses strike the ground 22 and are reflected from the ground 22 as echoes 46 at different reflection points 44. For example, an emitted ultrasonic pulse can be reflected as an echo 46 at one or more reflection points 44.

[0050] The echoes 46 are detected by the first ultrasonic sensor 20 as direct echoes and by the second ultrasonic sensor 42 as cross-echoes. Detecting the ground echoes 46 with the first ultrasonic sensor 20 and with the second ultrasonic sensor 42 comprises, for each ultrasonic sensor 20, 42, measuring an elevation angle 32 of each ground echo 46 and measuring the duration of a period between the emission of an ultrasonic pulse and the reception of the ground echoes 46 associated with the ultrasonic pulse.

[0051] In an alternative embodiment (not shown), the first and second ultrasonic sensors alternately emit an ultrasonic pulse. The emission of the ultrasonic pulses by the first and second ultrasonic sensors can be achieved through a repeating transmission pattern. This allows for particularly uniform coverage of the vehicle's surroundings.

[0052] The control unit 14 filters the detected ground echoes 46 such that those ground echoes with a low signal-to-noise ratio, amplitude, significance, and / or correlation coefficient are filtered out. A filtered-out ground echo 46 is no longer considered for calibrating the first ultrasonic sensor 20.

[0053] The control unit 14 determines, for each ground echo 46, the distance of the reflection point 44 from the first ultrasonic sensor 20 and the second ultrasonic sensor 42 based on the measured duration of the period between the emission of the ultrasonic pulse and the reception of the ground echo 46 and based on the heights 26 of the first ultrasonic sensor 20 and the second ultrasonic sensor 42 stored in the control unit 14. For this purpose, the control unit 14 can use a value of a speed of sound stored in the memory 28.

[0054] Based on the determined distances, the control unit 14 assigns each reflection point 40 to one of the distance ranges 34, 36, 38, 40. In the illustrated embodiment, four reflection points 40 are assigned to each distance range 34, 36, 38, 40.

[0055] Fig. Figure 3 shows that each distance region 34, 36, 38, 40 is rectangular. This is not mandatory. In an alternative embodiment not shown, the distance regions may not be rectangular. For example, the distance regions may be segments of a circular ring.

[0056] The control unit 14 determines a target elevation angle for each ground echo 46 and for each ultrasonic sensor 20, 42 based on the determined distance of the reflection point 44 and the stored height 26 of the first ultrasonic sensor 20 and the stored height of the second ultrasonic sensor 42.

[0057] The control unit 14 determines deviations between the measured elevation angles 32 and the determined target elevation angles by forming a difference between the measured elevation angles 32 and the respective corresponding target elevation angle.

[0058] Each detected deviation is assigned to the distance range 34, 36, 38, 40 of its corresponding reflection point 40. Each deviation is stored in the memory 28 of the control unit 14 with reference to the corresponding distance range 34, 36, 38, 40.

[0059] Fig. Figure 4 shows an example of Table 48 showing the stored deviations. The deviations for the first ultrasonic sensor 20 are stored separately from the deviations for the second ultrasonic sensor 42. In the illustrated embodiment, four deviations are stored for each ultrasonic sensor 20, 42 and for each distance range 34, 36, 38, 40.

[0060] The control unit 14 determines the variance of deviations from the target elevation angles for each ultrasonic sensor 20, 42 and for each distance range 34, 36, 38, 40. Based on this determined variance, the control unit 14 calculates a weighting factor for each distance range 34, 36, 38, 40 and for each ultrasonic sensor 20, 42. The weighting factor is higher the lower the variance. Therefore, distance ranges 34, 36, 38, 40 with lower variance receive a higher weighting factor.

[0061] The control unit 14 calculates a mean or median value of the deviations for each ultrasonic sensor 20, 42 and for each distance range 34, 36, 38, 40. In the illustrated embodiment, for example, the mean value for the first ultrasonic sensor 20 and for the distance range 34 is calculated from the four deviations of the distance range 34.

[0062] The control unit 14 analyzes the mean deviations for each ultrasonic sensor 20, 42 to determine whether a mean value for a distance range 34, 36, 38, 40 is an outlier. To do this, the control unit can determine the slope between each mean value and the mean value of an adjacent distance range 34, 36, 38, 40. If a slope value for a mean value deviates from the values ​​of the other slopes by a factor of 2, the control unit 14 identifies this mean value as an outlier. The mean value identified as an outlier is then ignored. In other words, the mean value identified as an outlier is not used for calibrating the first ultrasonic sensor 20.

[0063] The control unit 14 analyzes the mean values ​​of the deviations for each ultrasonic sensor 20, 42 to determine whether the mean values ​​follow a trend and / or exhibit a step. A trend can be present if the mean values ​​of the deviations increase or decrease with increasing distance of the distance ranges 34, 36, 38, 40 from the first ultrasonic sensor 20. If the control unit 14 identifies a trend or a step, it terminates the process. In the illustrated embodiment, the control unit 14 does not identify a trend or a step.

[0064] The control unit 14 determines a correction value for detecting an elevation angle with the first ultrasonic sensor 20 by calculating the mean of the deviations of the first ultrasonic sensor 20 and the second ultrasonic sensor 42, taking into account the determined weighting factors. In the illustrated embodiment, the mean values ​​of the distance ranges 34, 36, 38, 40 of the first ultrasonic sensor 20 and the second ultrasonic sensor 42 are multiplied by the corresponding weighting factors in order to then calculate the mean of the mean deviations.

[0065] In an alternative embodiment not shown, the control unit can determine the correction value for detecting the elevation angle with the first ultrasonic sensor by forming an average of the mean values ​​of the distance ranges of the first ultrasonic sensor, taking into account the associated weighting factors.

[0066] Additionally, the ultrasound-based driver assistance system 12 detects a temperature at which the correction value was determined. The temperature, together with the correction value for the first ultrasound sensor 20, is stored in memory 28.

[0067] The control unit 14 is designed to analyze a history of correction values ​​for the first ultrasonic sensor 20 to detect the presence of an alignment error of the first ultrasonic sensor 20. For example, an alignment error can be detected by a sudden jump in a correction value.

[0068] After executing the procedure, the first ultrasonic sensor 20 can detect an elevation angle of an echo, wherein the detected elevation angle is corrected by the stored correction value.

[0069] Fig. Figure 5 shows an exemplary procedure for calibrating the elevation angle of the first ultrasonic sensor 20.

[0070] The method comprises the steps of: a) specifying the height 26 of the first and second ultrasonic sensors 20, 42 from the ground 22; m) emitting the plurality of ultrasonic pulses by means of the first ultrasonic sensor 20; b) detecting the plurality of ground echoes 46 with the first and second ultrasonic sensors 20, 42, wherein the detection of the ground echoes 46 for each ground echo 46 comprises measuring an elevation angle 32 of the ground echo 46 and measuring a duration of a period between an emission of the ultrasonic pulse and a reception of the ground echo 46 with the first and second ultrasonic sensors 20, 42; s) Filtering the ground echoes 46 detected in step b) such that those ground echoes 46 with a low signal-to-noise ratio, amplitude, significance and / or correlation coefficients are filtered out;r) Determine, for each ground echo 46, the distance of the reflection point 44 of the ground echo 46, at which the ultrasonic pulse was reflected from the ground 22, from the first and second ultrasonic sensors 20, 42, based on the duration of the period between the emission of the ultrasonic pulse and the reception of the ground echo 46 by the first or second ultrasonic sensor 20, 42, as measured in step b); c) Determine the target elevation angles of the ground echoes 46 based on the durations measured in step b), wherein the determination of the target elevation angles for each ground echo 46 is based on the distance determined in step r) and the height 26 specified in step a); d) Determine deviations of the elevation angles 32 of the ground echoes 46 measured in step b) from the target elevation angles of the ground echoes 46;f) Assigning each deviation determined in step d) to a distance range 34, 36, 38, 40 of the first ultrasonic sensor 20, such that a plurality of deviations determined in step d) are assigned to each distance range 34, 36, 38, 40; h) Determining a standard deviation of the deviations for each distance range 34, 36, 38, 40; i) Determining a weighting factor based on the standard deviation determined in step h) for each distance range 34, 36, 38, 40; g) Calculating a mean of the deviations for each distance range 34, 36, 38, 40; j) Analyzing the means calculated in step g) for the presence of an outlier and excluding the means identified as outliers; k) Analyze the means formed in step g) for the presence of a trend and / or a stage and terminate the procedure if a trend and / or a stage is identified in the means;e) Determining the correction value by calculating the mean of the mean deviations calculated in step g), taking into account the weighting factors determined in step i); n) Detecting the temperature during the execution of at least one of steps a) to e); o) Storing the correction value determined in step e) and the temperature detected in step n).

Claims

[1] Method for calibrating, in particular an elevation angle (32), an ultrasonic sensor (16, 20) of an ultrasonic-based driver assistance system (12) of a vehicle (10), wherein the vehicle (10) is placed on a floor (22), the method comprising the steps: a) Specifying a height (26) of the ultrasonic sensor (16, 20) from the ground (22) or determining the height (26) of the ultrasonic sensor (16, 20) from the ground (22), b) Detecting a plurality of ground echoes (46) of an ultrasonic pulse from the ground (22) with the ultrasonic sensor (16, 20), wherein the detection of the ground echoes (46) for each ground echo (46) comprises measuring an elevation angle (32) of the ground echo (46) and measuring a duration of a period between an emission of the ultrasonic pulse and a reception of the ground echo (46) with the ultrasonic sensor (16, 20), c) Determining the target elevation angle of the ground echoes (46) based on the durations measured in step b), d) Determining deviations of the elevation angles (32) of the ground echoes (46) measured in step b) from the target elevation angles of the ground echoes (46), and e) Determining a correction value for detecting the elevation angle (32) with the ultrasonic sensor (16, 20) based on the deviations determined in step d). [2] Method according to claim 1, - wherein the detection of the plurality of ground echoes (46) of step b) comprises the detection of a plurality of ground echoes (46) from a plurality of ultrasonic pulses, - wherein the procedure includes the step: f) assigning each deviation determined in step d) to a distance range (34, 36, 38, 40) of the ultrasonic sensor (16, 20), such that for each distance range a plurality of deviations determined in step d) are assigned, - wherein the procedure includes the step: g) forming a mean of the deviations for each distance range (34, 36, 38, 40), - where the determination of the correction value in step e) is based on the mean values ​​of the deviations formed in step g). [3] Method according to claim 2, - wherein the procedure includes the step: h) Determining a dispersion of the deviations for each distance range (34, 36, 38, 40), - wherein the procedure includes the step: i) determining a weighting factor based on the dispersion determined in step h) for each distance range (34, 36, 38, 40), - where the correction value is determined in step e) by taking the mean of the mean values ​​of the deviations formed in step g), taking into account the weighting factors determined in step i). [4] Method according to claim 2 or 3, - wherein the procedure includes the step: j) Analyzing the means formed in step g) for the presence of an outlier and excluding the means identified as outliers. [5] Method according to any one of claims 2 to 4 above, - wherein the procedure includes the step: k) Analyzing the means formed in step g) for the presence of a trend and / or a stage and terminating the procedure if a trend and / or a stage is identified in the means. [6] Method according to any of the preceding claims, - wherein the procedure prior to step b) includes the step: m) emitting the ultrasound pulse and / or the plurality of ultrasound pulses by means of the ultrasound sensor (16, 20). [7] Method according to any of the preceding claims, - wherein step b) includes detecting the majority of ground echoes (46) using a further ultrasonic sensor (16, 42), - where the determination of the correction value in step e) is based on the ground echoes (46) detected in step b) by means of the further ultrasonic sensor (16, 42). [8] Method according to any of the preceding claims, - wherein the method comprises the steps: n) detecting a temperature during the execution of at least one of steps a) to e), and o) storing the correction value determined in step e) and the temperature detected in step n). [9] Method according to any of the preceding claims, - wherein the procedure includes the step: p) Detecting an alignment error of the ultrasonic sensor (16, 20) by analyzing a history of the correction value determined in step e). [10] vehicle (10), in particular motor vehicle, comprising: - an ultrasound-based driver assistance system (12) that is configured to perform a method according to one of the preceding claims.

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