Method for determining positions of ultrasonic sensors of an ultrasonic sensor array of a vehicle

Abstract

Method for determining positions (I, II, III) of ultrasonic sensors (16) of an ultrasonic sensor row (12, 14) of a vehicle (10) placed on a surface (36).

Description

State of the art

[0001] The invention relates to a method for determining positions of ultrasonic sensors of an ultrasonic sensor array of a vehicle.

[0002] Vehicles often have ultrasonic-based driver assistance systems, especially ultrasonic parking aids, with multiple, for example, four or six, ultrasonic sensors. The individual ultrasonic sensors can be connected to a control unit, particularly for signal transmission, via a sensor bus. Disclosure of the invention

[0003] The object of the invention is to provide a method for determining positions of ultrasonic sensors of an ultrasonic sensor row of a vehicle, which method enables automatic determination of the positions of the ultrasonic sensors and the determination of the positions of the ultrasonic sensors with a high degree of accuracy and is cost-effective.

[0004] The object underlying the invention is achieved by a method for determining positions of ultrasonic sensors of an ultrasonic sensor array of a vehicle having the features of claim 1. Advantageous developments of the invention are mentioned in the subclaims.

[0005] A method according to the invention is suitable for determining the positions of ultrasonic sensors in an ultrasonic sensor array of a vehicle positioned on a surface. The ultrasonic sensor array comprises at least a first ultrasonic sensor, a second ultrasonic sensor, and a third ultrasonic sensor.

[0006] The positions of the ultrasonic sensors can determine an order or sequence of the ultrasonic sensors, for example, along the ultrasonic sensor array. A position of an ultrasonic sensor can be understood as a geographical address of the ultrasonic sensor.

[0007] It is also conceivable for the ultrasonic sensor array to comprise, for example, four or six ultrasonic sensors. All ultrasonic sensors can be of identical design. The ultrasonic sensors can be connected to a vehicle control unit via a serial sensor bus or a two-wire or three-wire bus, particularly for signaling purposes.

[0008] The method comprises the steps of: a) generating a first ultrasonic pulse using the first ultrasonic sensor; b) measuring a first echo of the first ultrasonic pulse from the ground using the first ultrasonic sensor, the second ultrasonic sensor, and the third ultrasonic sensor; c) generating a second ultrasonic pulse using the second ultrasonic sensor; d) measuring a second echo of the second ultrasonic pulse from the ground using the first ultrasonic sensor, the second ultrasonic sensor, and the third ultrasonic sensor; e) generating a third ultrasonic pulse using the third ultrasonic sensor; f) measuring a third echo of the third ultrasonic pulse from the ground using the first ultrasonic sensor, the second ultrasonic sensor, and the third ultrasonic sensor;g) determining the positions of the ultrasonic sensors of the ultrasonic sensor array as a function of the measured first, second and third echoes, in particular as a function of the measured echo magnitudes of the first echo, the measured echo magnitudes of the second echo and the measured echo magnitudes of the third echo;

[0009] Advantageously, this eliminates the need for additional electronics to determine the positions of the ultrasonic sensors, as the method uses the echo detection mechanisms of the ultrasonic sensors to determine the positions, making the method cost-effective. Also advantageous is that no disruptive voltage drops occur in a line during execution of the method, improving undervoltage behavior and enabling, for example, the use of a two-wire bus with power-over-data line or a serial bus. In addition, the method can advantageously make it possible to verify the wiring configured in the vehicle with the actual wiring in the case of point-to-point wired ultrasonic sensors.

[0010] Each echo can be an ultrasonic pulse reflected from the ground.

[0011] An echo magnitude can be understood as the volume of the echo.

[0012] Measuring the echoes can each be a measurement of the echo magnitude. For example, measuring the first echo with the first ultrasonic sensor can be a measurement of the echo magnitude, measuring the first echo with the second ultrasonic sensor can be a measurement of the echo magnitude, and measuring the first echo with the third ultrasonic sensor can be a measurement of the echo magnitude.

[0013] The position in step g) can be determined by comparing the measured echo magnitudes. The largest measured echo magnitude for an ultrasonic pulse can indicate that the ultrasonic sensor that received the echo and did not generate the ultrasonic pulse is located adjacent to the ultrasonic sensor that did generate the ultrasonic pulse. Thus, for each ultrasonic sensor that emits an ultrasonic pulse, the adjacent ultrasonic sensors can be determined using the echo magnitudes. The positions of the ultrasonic sensors in the ultrasonic sensor array can be determined based on the determined adjacent ultrasonic sensors.

[0014] The measured echo magnitudes can be an indication of the positions of the ultrasonic sensors. For each measured echo, the positions of the ultrasonic sensors can be predetermined based on the strength of the echo magnitudes. For example, a position can be predetermined for an ultrasonic sensor that received the echo and did not generate the ultrasonic pulse and is not located adjacent to the ultrasonic sensor that emitted the ultrasonic pulse. The predetermined position can depend on the strength of the echo magnitude. For example, a predetermined position for a large echo magnitude can be closer to the position of the ultrasonic sensor that emitted the ultrasonic pulse than a predetermined position for a small echo magnitude.

[0015] The predetermined position of the ultrasonic sensor can be confirmed when a neighboring ultrasonic sensor emits an ultrasonic pulse and the ultrasonic sensor arranged at the predetermined position is determined to be a neighboring ultrasonic sensor.

[0016] The method can be performed after the vehicle has been manufactured. For example, the method can be performed at one end of a vehicle manufacturer's production line. Additionally or alternatively, the method can be performed after replacing an ultrasonic sensor.

[0017] In a further development of the method, each ultrasonic sensor has an adjustable effective direction. Advantageously, this allows the ultrasonic sensors to be designed to be controllable in their directional characteristics during transmission and / or reception. Each effective direction can, for example, be a direction in which the ultrasonic sensor emits a generated ultrasonic pulse and / or receives an echo. In other words, the angle of an orientation of a sound cone of the ultrasonic sensor and the angle of an orientation of a reception sensitivity, in particular a maximum one, of the ultrasonic sensor can be adjustable.

[0018] Each ultrasonic sensor can be designed as a piezoelectric micromachined ultrasonic transducer. Each ultrasonic sensor can have an ultrasonic array. The ultrasonic array can allow for adjustable effective directions.

[0019] The method can comprise the step before step a): h) specifying an azimuth angle that is not equal to 0°. The method can comprise the steps before step a): a.1) directing the effective direction of the first ultrasonic sensor at the positive value of the azimuth angle towards the ground; and a.2) directing the effective directions of the second and third ultrasonic sensors at the negative value of the azimuth angle towards the ground. The method can comprise the steps before step c): c.1) directing the effective direction of the second ultrasonic sensor at the positive value of the azimuth angle towards the ground; and c.2) directing the effective directions of the first and third ultrasonic sensors at the negative value of the azimuth angle towards the ground. The method can comprise the steps before step e): e.1) directing the effective direction of the third ultrasonic sensor at the positive value of the azimuth angle towards the ground; and e.2) Directing the effective directions of the first and second ultrasonic sensors towards the ground at the negative amount of the azimuth angle.

[0020] By aiming the ultrasonic sensors at the substrate at an azimuth angle, the echo measurement can be ensured. In particular, the azimuth angle allows the ultrasonic sensors to more clearly measure differences in echo magnitude.

[0021] Aligning the effective direction of an ultrasonic sensor toward the ground can involve adjusting the effective direction in an elevation plane of the ultrasonic sensor by an elevation angle of more than 85°. The azimuth angle can have a value in a range from 2° to 90°. An azimuth angle other than 0° can result in the effective direction of the ultrasonic sensor being rotated in its azimuthal plane.

[0022] In a further development of the method, the azimuth angle satisfies the condition α = arctan(avg(d / 2) / avg(h)), where α is the azimuth angle, where avg(d / 2) is an average half-distance between two adjacent ultrasonic sensors, where d is a distance between two adjacent ultrasonic sensors, where avg(h) is the average distance of the ultrasonic sensors from the background, where h is a distance between the background and an ultrasonic sensor. This allows the echoes to be measured particularly clearly. The average half-distance between two adjacent ultrasonic sensors and / or the average distance of the ultrasonic sensors from the background can be predetermined. The average half-distance between two adjacent ultrasonic sensors avg(d / 2) can have a value in the range from 40 cm (centimeters) to 60 cm. The average distance of the ultrasonic sensors from the background avg(h) can have a value in the range from 40 cm to 60 cm.

[0023] In a further development of the method, the method comprises the following steps before step h): i) directing the effective direction of the ultrasonic sensors at an azimuth angle of 0° towards the substrate; j) measuring distances of the ultrasonic sensors from the substrate using the ultrasonic sensors; k) determining the average distance of the ultrasonic sensors from the substrate based on the distances measured in step j); and m) determining the azimuth angle using the conditions α = arctan(avg(d / 2) / avg(h)). This allows the echoes to be measured particularly clearly.

[0024] In a further development of the method, steps a.1) to g) are performed multiple times, for example, three times, for different azimuth angles. This allows the positions of the ultrasonic sensors to be determined more reliably. For example, objects in the vehicle's surroundings or crosstalk between the ultrasonic sensors, which could distort the result, can be excluded.

[0025] In a further development of the method, the method comprises the following step before step a.1): n) Detection of an object using the ultrasonic sensors. The object is spaced from the ultrasonic sensors at a certain distance. The distance between the object and the ultrasonic sensors is at most twice the average distance of the ultrasonic sensors from the ground. Steps a.1) to g) are carried out depending on the object detected in step n). This can reduce or completely avoid the risk of incorrect positioning due to an echo from the object.

[0026] The effective direction of each ultrasonic sensor can have an elevation angle of 0° and an azimuth angle of 0° upon detection of the object. If an object is detected in step n), the method can comprise the step: p) masking the ultrasonic sensors that are at a distance from the object that is twice the average distance of the ultrasonic sensors from the ground. Additionally or alternatively, the method can comprise the step: q) outputting an error message and / or aborting the method.

[0027] In a further development of the method, step g) comprises normalizing the measured first echo to a maximum measured echo magnitude of the first echo. Step g) comprises normalizing the measured second echo to a maximum measured echo magnitude of the second echo. Step g) comprises normalizing the measured third echo to a maximum measured echo magnitude of the third echo.

[0028] In a further development of the method, the method comprises the step after step g): o) storing the determined positions of the ultrasonic sensors in a memory of the vehicle.

[0029] This advantageously allows the stored positions of the ultrasonic sensors to be used by a user of the vehicle by reading the memory, thus eliminating the need to repeat the process.

[0030] Advantageously, by storing the determined positions, the vehicle can be operational more quickly, whereby, in particular, only the predetermined echo magnitudes of the addressing need to be confirmed. If a discrepancy between the actual positions and the stored positions is detected, the method can be executed.

[0031] The memory may be designed as a non-volatile memory of a control unit of the vehicle.

[0032] In a further development of the method, each measurement of the echoes includes a measurement of the directional angles of the echoes. The positions are determined based on the directional angles. A directional angle of an echo can be an angle that occurs between a propagation direction of the echo and the array of ultrasonic sensors. The directional angles of the echoes can be measured by measuring phase shifts using the ultrasonic sensors. The positions can be determined based on the phase shifts. A phase shift can be a temporal sequence of echo measurements using the array of ultrasonic sensors.

[0033] For example, the effective direction of the ultrasonic sensors can be spherical. The ultrasonic sensor closest to the ultrasonic sensor generating the ultrasonic pulse can measure the smallest directional angle. The smallest directional angle can be measured by measuring the echo before the ultrasonic sensors located further away from the ultrasonic sensor generating the ultrasonic pulse. Each ultrasonic sensor located further away from the ultrasonic sensor generating the ultrasonic pulse can measure a larger directional angle of the echo. The positions of the ultrasonic sensors can be determined based on the ascending order of the directional angles of the echoes.

[0034] Possible embodiments of the invention are explained below with reference to the accompanying drawings. They show: Fig. 1 a schematic representation of a vehicle with one row of ultrasonic sensors and another row of ultrasonic sensors, Fig. 2 a schematic representation of the ultrasonic sensor series of Fig. 1, Fig. 3 another schematic representation of the ultrasonic sensor series of Fig. 1, and Fig. 4 to 6 a schematic flow of a method for determining positions of ultrasonic sensors of the ultrasonic sensor series of Fig. 1.

[0035] Fig. 1 shows a vehicle 10. The vehicle 10 has an ultrasonic sensor array 12 and another ultrasonic sensor array 14. The ultrasonic sensor array 12 is arranged at a front of the vehicle 10. The other ultrasonic sensor array 14 is arranged at a rear of the vehicle 10.

[0036] Each ultrasonic sensor row 12, 14 has six ultrasonic sensors 16. The ultrasonic sensors 16 of the ultrasonic sensor row 12 and the ultrasonic sensors 16 of the further ultrasonic sensor row 14 are each connected to a control unit 22 of the vehicle 10 by means of a two-wire serial sensor bus 18, 20.

[0037] Fig. 2 shows, by way of example, three ultrasonic sensors 16 of the ultrasonic sensor series 12 in a front view of the vehicle 10. Each ultrasonic sensor 16 is a piezoelectric micromachined ultrasonic transducer.

[0038] An effective direction 24 of each ultrasonic sensor 16 is adjustable. The effective direction 24 of an ultrasonic sensor 16 indicates the direction in which the ultrasonic sensor 16 emits an ultrasonic pulse and in which the ultrasonic sensor 16's maximum reception sensitivity is directed for receiving an echo. The control unit 22 is configured to adjust the effective direction 24 of each ultrasonic sensor 16.

[0039] Fig. 2 shows that the effective direction 24 can be adjusted by an azimuth angle 26 by rotating the effective direction 24 in an azimuthal plane of the ultrasonic sensor 16.

[0040] Fig. Figure 3 shows the ultrasonic sensor array 12 from the side. The effective direction 24 can be adjusted by an elevation angle 28 by rotating the effective direction 24 in an elevation plane of the ultrasonic sensor 16.

[0041] The effective direction 24 is aligned parallel to a longitudinal axis of the vehicle 10 for an azimuth angle 26 of 0° and an elevation angle 28 of 0°.

[0042] Fig. 1 shows that each ultrasonic sensor 16 of the ultrasonic sensor row 12 and each ultrasonic sensor 16 of the further ultrasonic sensor row 14 is located at one of the positions I to VI. The logical addressing of the ultrasonic sensors 16 has already taken place, so that each ultrasonic sensor 16 can be addressed by the control unit 22. The number of ultrasonic sensors per ultrasonic sensor row 12, 14 is predetermined by the control unit 22. The control unit 22 does not know which ultrasonic sensor 16 is located at which position I to VI. In order to determine the positions I to VI of each ultrasonic sensor 16, the control unit 22 executes a method for determining the positions of the ultrasonic sensors 16 for each ultrasonic sensor row 12, 14.

[0043] A sequence of the procedure is set out in the Fig. 4 to 6. In Fig. 4 to 6, the sequence of the method is shown by way of example for three ultrasonic sensors 16 of the ultrasonic sensor row 12, wherein the sequence for determining the positions for the remaining ultrasonic sensors 16 of the ultrasonic sensor row 12 and the further ultrasonic sensor row 14 can be expanded accordingly or is the same.

[0044] Fig. 4 to 6 show that a first ultrasonic sensor 30 of the ultrasonic sensor array 12 is located at position III. A second ultrasonic sensor 32 of the ultrasonic sensor array 12 is located at position II, and a third ultrasonic sensor 34 of the ultrasonic sensor array 12 is located at position I.

[0045] Each ultrasonic sensor 30, 32, 34 is spaced apart from a ground 36 on which the vehicle 10 is placed by a distance 38. The distances 38 of the ultrasonic sensors 30, 32, 34 from the ground 36 differ from one another. The method comprises the step of: i) directing each effective direction 24 of the ultrasonic sensors 16 at an azimuth angle 26 of 0° and an elevation angle of over 85° toward the ground 36; j) measuring the distances 38 of the ultrasonic sensors 30, 32, 34 from the ground 36 using the ultrasonic sensors 30, 32, 34; k) Determining an average distance avg(h) of the ultrasonic sensors 30, 32, 34 from the ground 36 by forming an average value of the distances 38 measured in step j). In the illustrated initial example, the average distance avg(h) of the ultrasonic sensors 30, 32, 34 from the ground 36 is 50 cm.

[0046] The first ultrasonic sensor 30 is spaced 40 from the second ultrasonic sensor 32. The second ultrasonic sensor 32 is spaced 42 from the third ultrasonic sensor 34. The distances 40, 42 are stored in the control unit 22 as predefined values. The control unit 22 determines an average half-distance avg(d / 2) between two adjacent ultrasonic sensors by calculating an average of the distances 40, 42 divided by a factor of two. In the illustrated initial example, the average half-distance avg(d / 2) is 25 cm.

[0047] In a step m) of the method, the control unit 22 determines an azimuth angle 26 using the conditions α = arctan(avg(d / 2) / avg(h)), where α is the azimuth angle 26. In the illustrated embodiment, the azimuth angle 26 is 27°.

[0048] The method comprises the step: n) Detection of an object by means of the ultrasonic sensors 30, 32, 34, which is spaced from the background 36 by a distance of at most twice the average distance of the ultrasonic sensors 30, 32, 34. In the illustrated embodiment of the Fig. 4 to 6, no object is detected. If an object is detected within this distance by an ultrasonic sensor 30, 32, 34, the method is executed without this ultrasonic sensor 30, 32, 34. In other words, the ultrasonic sensor 30, 32, 34 that detects an object is masked.

[0049] Fig. 4 shows that the method comprises the steps: a.1) Directing the effective direction 24 of the first ultrasonic sensor 30 at the positive value of the determined azimuth angle 26, i.e., 27°, and an elevation angle of more than 85° toward the substrate 36; a.2) Directing the effective directions 24 of the second and third ultrasonic sensors 32, 34 at the negative value of the determined azimuth angle 26, i.e., -27°, and an elevation angle of more than 85° toward the substrate 36; a) Generating a first ultrasonic pulse by means of the first ultrasonic sensor 30; b) Measuring a first echo of the first ultrasonic pulse from the substrate 36 with the first, second, and third ultrasonic sensors 30, 32, 34.

[0050] By measuring the first echo with the first ultrasonic sensor 30, it is confirmed that the first ultrasonic sensor 30 is functional.

[0051] Measuring the echoes involves measuring the magnitude of the echoes, in particular the volume of the echoes. Because the second ultrasonic sensor 32 is positioned closer to the first ultrasonic sensor 30 than the third ultrasonic sensor 34, the second ultrasonic sensor 32 measures a higher volume of the first echo than the third ultrasonic sensor 34.

[0052] Fig. 5 shows that the method comprises the steps: c.1) Directing the effective direction 24 of the second ultrasonic sensor 32 at the positive value of the determined azimuth angle 26, i.e., 27°, and an elevation angle of more than 85° toward the substrate 36; c.2) Directing the effective directions 24 of the first and third ultrasonic sensors 30, 34 at the negative value of the determined azimuth angle 26, i.e., -27°, and an elevation angle of more than 85° toward the substrate 36; c) Generating a second ultrasonic pulse by means of the second ultrasonic sensor 32; d) Measuring a second echo of the second ultrasonic pulse from the substrate 36 with the first, second, and third ultrasonic sensors 30, 32, 34.

[0053] By measuring the second echo with the second ultrasonic sensor 32, it is confirmed that the second ultrasonic sensor 32 is functional.

[0054] Because the effective direction 24 of the second ultrasonic sensor 32 is directed towards the third ultrasonic sensor 34, the effective direction 24 of the third ultrasonic sensor 34 is directed towards the second ultrasonic sensor 32 and the effective direction 24 of the first ultrasonic sensor 30 is directed away from the second ultrasonic sensor 32, a higher volume of the second echo is measured by the third ultrasonic sensor 34 than by the first ultrasonic sensor 30.

[0055] Fig. 6 shows that the method comprises the steps: e.1) Directing the effective direction 24 of the third ultrasonic sensor 34 at the positive value of the determined azimuth angle 26, i.e., 27°, and an elevation angle of more than 85° toward the substrate 36; e.2) Directing the effective directions 24 of the first and second ultrasonic sensors 30, 32 at the negative value of the determined azimuth angle 26, i.e., -27°, and an elevation angle of more than 85° toward the substrate 36; e) Generating a third ultrasonic pulse by means of the third ultrasonic sensor 34; f) Measuring a third echo of the third ultrasonic pulse from the substrate 36 with the first, second, and third ultrasonic sensors 30, 32, 34.

[0056] By measuring the third echo with the third ultrasonic sensor 34, it is confirmed that the third ultrasonic sensor 34 is functional.

[0057] Because the effective directions 24 of the first and second ultrasonic sensors 30, 32 are directed away from the third ultrasonic sensor 34 and the effective direction 24 of the third ultrasonic sensor 34 is directed away from the first and second ultrasonic sensors 30, 32, the third echo is not detected by the first and second ultrasonic sensors 30, 32.

[0058] The method comprises the step: g) determining the positions of the ultrasonic sensors 30, 32, 34 depending on the measured first, second, and third echoes. In the illustrated initial example, the control unit 22 concludes that the third ultrasonic sensor 34 is located at position I, since the third echo was not measured by the first and second ultrasonic sensors 30, 32. The control unit 22 concludes that the second ultrasonic sensor 32 is located at position II, since the second echo was measured by the third ultrasonic sensor 34 at a higher volume than by the first ultrasonic sensor 30. The control unit 22 concludes that the first ultrasonic sensor 30 is located at position III, since the first echo was measured by the second ultrasonic sensor 32 at a higher volume than by the third ultrasonic sensor 34.As a result, the method has determined the positions I, II, III of the ultrasonic sensors 30, 32, 34 of the ultrasonic sensor series 12.

[0059] After determining the positions I, II, III of the ultrasonic sensors 30, 32, 34, the method comprises the step: o) storing the determined positions I, II, III of the ultrasonic sensors 30, 32, 34 in a non-volatile memory of the control unit 22.

[0060] The determination of the positions of the remaining ultrasonic sensors 16 of the vehicle 10 is carried out in the same way as in Fig. 4 to 6 or in Fig. 7 in the process shown.

Claims

[1] Method for determining positions (I, II, III) of ultrasonic sensors (16) of an ultrasonic sensor row (12, 14) of a vehicle (10) placed on a ground (36), wherein the ultrasonic sensor row (12, 14) comprises at least a first ultrasonic sensor (30), a second ultrasonic sensor (32) and a third ultrasonic sensor (34), the method comprising the steps of: a) generating a first ultrasonic pulse by means of the first ultrasonic sensor (30), b) measuring a first echo of the first ultrasonic pulse from the substrate (36) with the first ultrasonic sensor (30), the second ultrasonic sensor (32) and the third ultrasonic sensor (34), c) generating a second ultrasonic pulse by means of the second ultrasonic sensor (32), d) measuring a second echo of the second ultrasonic pulse from the substrate (36) with the first ultrasonic sensor (30), the second ultrasonic sensor (32) and the third ultrasonic sensor (34), e) generating a third ultrasonic pulse by means of the third ultrasonic sensor (34), f) measuring a third echo of the third ultrasonic pulse from the substrate (36) with the first ultrasonic sensor (30), the second ultrasonic sensor (32) and the third ultrasonic sensor (34), g) determining the positions (I, II, III) of the ultrasonic sensors (30, 32, 34) of the ultrasonic sensor row (12, 14) as a function of the measured first echo, measured second echo and measured third echo, in particular as a function of the measured echo magnitudes of the first echo, the measured echo magnitudes of the second echo and the measured echo magnitudes of the third echo. [2] Method according to claim 1, - wherein each ultrasonic sensor (16) has an adjustable direction of action (24), - wherein the method comprises the step before step a): h) specifying an amount of an azimuth angle (26) which is not equal to 0°, - wherein the method before step a) comprises the steps of: a.1) directing the effective direction (24) of the first ultrasonic sensor (30) at the positive azimuth angle (26) towards the ground; and a.2) directing the effective directions (24) of the second and third ultrasonic sensors (32, 34) at the negative azimuth angle (26) towards the ground (36); - wherein the method before step c) comprises the steps of: c.1) directing the effective direction (24) of the second ultrasonic sensor (32) at the positive azimuth angle (26) towards the ground (36); and c.2) directing the effective directions (24) of the first and third ultrasonic sensors (30, 34) at the negative azimuth angle (26) towards the ground (36); - wherein the method comprises the steps before step e): e.1) directing the effective direction (24) of the third ultrasonic sensor (34) at the positive azimuth angle (26) towards the substrate (36); and e.2) directing the effective directions (24) of the first and second ultrasonic sensors (30, 32) at the negative azimuth angle (26) towards the substrate (36). [3] Method according to claim 2, - wherein the azimuth angle (26) satisfies the condition α = arctan(avg(d / 2) / avg(h)), where α is the azimuth angle (26), where avg(d / 2) is a mean half distance between two adjacent ultrasonic sensors (16), where avg(h) is the mean distance of the ultrasonic sensors (16) from the ground (36). [4] Method according to claim 3, - wherein the method, prior to step h), comprises the steps of: i) directing the effective directions (24) of the ultrasonic sensors (16) at an azimuth angle of 0° onto the substrate (36); j) measuring distances of the ultrasonic sensors (16) from the substrate (36) using the ultrasonic sensors (16); k) determining the average distance of the ultrasonic sensors (16) from the substrate (36) based on the distances measured in step j); and m) determining the azimuth angle (26) using the conditions α = arctan(avg(d / 2) / avg(h)). [5] Method according to claim 2, - wherein steps a.1) to g) are carried out several times for mutually different azimuth angles (26). [6] Method according to one of the preceding claims 2 to 5, - wherein the method comprises the step before step a.1): n) detection of an object by means of the ultrasonic sensors (16), - wherein the object is spaced from the ultrasonic sensors (16), - wherein the distance between the object and the ultrasonic sensors (16) is at most twice the average distance of the ultrasonic sensors from the substrate (36), - wherein steps a.1) to g) are carried out depending on the object detected in step n). [7] Method according to one of the preceding claims 2 to 6, - wherein step g) comprises a normalization of the measured first echo to a maximum measured echo magnitude of the first echo, - wherein step g) comprises normalizing the measured second echo to a maximum measured echo magnitude of the second echo, - wherein step g) comprises normalizing the measured third echo to a maximum measured echo magnitude of the third echo. [8] Method according to one of the preceding claims 2 to 7, - wherein the method after step g) comprises the step: o) storing the determined positions (I, II, III) of the ultrasonic sensors (16) in a memory of the vehicle (10). [9] Method according to one of the preceding claims 1 to 8, - each measurement of the echoes comprises a measurement of directional angles of the echoes, - whereby the positions (I, II, III) are determined based on the direction angles.

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