DEVICE FOR ASCERTAINING A MISALIGNMENT OF A DETECTION UNIT FASTENED ON A VEHICLE

Abstract

A method and a device for ascertaining a misalignment of at least one detection unit fastened on a vehicle with respect to the intended sensor main beam direction. The device includes at least one detection unit which emits signals and receives partial signals which have been reflected on objects, and ascertains the distance and the azimuth angle of the reflecting objects, and further includes an evaluation unit, to which the ascertained positions of the at least one detection unit are forwarded, and the determination of a misalignment takes place in the evaluation unit by comparing the stored alignment of the sensor main beam direction and the ascertained angle of the object extension with respect to the sensor main beam direction, this taking place under the assumption that the vehicle is moving on average, in parallel to the object extension, for the period during which the misalignment is ascertained.

Claims

1. A device for ascertaining a misalignment of at least one detection unit fastened on a vehicle with respect to an intended sensor main beam direction, the device comprising: at least one detection unit which emits signals and receives partial signals which have been reflected on objects, and ascertains a distance and an azimuth angle of the reflecting objects; and an evaluation unit to which the ascertained distance and azimuth angle are forwarded, wherein the determination of a misalignment takes place in the evaluation unit by comparing stored alignment of the sensor main beam direction and an ascertained angle of an object extension with respect to a sensor main beam direction, and under the assumption that the vehicle is moving on average in parallel to the object extension for a period during which the misalignment is ascertained.

2. The device as recited in claim 1, wherein the detection unit is a radar sensor which operates in the microwave range or the millimeter-wave range.

3. The device as recited in claim 1, wherein multiple detection units are mounted on the vehicle.

4. The device as recited in claim 3, wherein the detection areas of adjacent detection units at least partially overlap.

5. The device as recited in claim 3, wherein knowledge of the instantaneous misalignment angle of a detection unit is utilized for ascertaining the misalignment angle of an adjacently situated detection unit.

6. A method for ascertaining a misalignment of at least one detection unit fastened on a vehicle with respect to an intended sensor main beam direction, the method comprising: emitting signals, by at least one detection unit, and receiving partial signals reflected on objects; ascertaining a distance and an azimuth angle of the reflecting objects, the ascertained distance and azimuth angle of the objects being forwarded to the at least one detection unit with the aid of an evaluation unit, wherein the determination of a misalignment takes place in the evaluation unit by comparing stored alignment of the sensor main beam direction and an ascertained angle of an object extension with respect to a sensor main beam direction, and under the assumption that the vehicle is moving on average in parallel to the object extension for a period during which the misalignment is ascertained.

7. The method as recited in claim 6, wherein, in order to ascertain the misalignment angle, a comparison of the stored alignment of the sensor main beam direction and the ascertained angle of the object extension with respect to the sensor main beam direction is carried out by ascertaining a difference angle between a vehicle longitudinal axis and the sensor main beam direction, and, from this, subtracting the angle value at which the detection unit ascertains the reflected partial signals of the transmission signals reflected on the extended object.

8. The method as recited in claim 7, wherein the misalignment is ascertained when specific object situations are detected.

9. The method as recited in claim 8, wherein the specific object situation is one of: a detection of an extended object next to the host vehicle on the right in a direction of travel of the host vehicle; a detection of an extended object next to the host vehicle on the left in the direction of travel; or a detection of extended objects next to the host vehicle on the left and on the right in the direction of travel.

10. The method as recited in claim 9, wherein an extended object is inferred when one of a guardrail, a concrete wall, a bridge railing, or a tunnel wall, is detected.

11. The method as recited in claim 6, wherein the ascertained misalignment angle is utilized for correcting an instantaneously measured object angle.

12. The method as recited in claim 6, wherein a shutoff of the detection unit takes place when the ascertained misalignment angle exceeds a predefined threshold value.

13. The method as recited in claim 11, wherein the misalignment angle used for correcting the instantaneously measured object angle is ascertained with the aid of a long-term filtering of measured values.

14. The method as recited in claim 12, wherein the misalignment angle to be ascertained for the shutoff is ascertained with the aid of a short-term filtering of the measured values.

15. The method as recited in claim 6, wherein positions of stationary objects detected in a range having the highest measuring quality are utilized for ascertaining a misalignment.

16. The method as recited in claim 15, wherein a detection unit has the highest measuring quality in a subarea of a detection area where the detection unit has at least one of: i) the greatest range, and ii) the highest angular accuracy.

17. The method as recited in claim 6, wherein, when multiple detection units are mounted on a vehicle, whereby when the detection areas of adjacent detection units at least partially overlap, knowledge of the instantaneous misalignment angle of a detection unit is utilized for ascertaining the misalignment angle of an adjacently situated detection unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Exemplary embodiments of the present invention are described in below with reference to the figures.

[0025] FIG. 1 shows a schematic top view of a vehicle including the system according to the present invention.

[0026] FIG. 2 shows a schematic block diagram of one specific embodiment of the device according to the present invention.

[0027] FIG. 3 shows one exemplary driving situation for describing the method according to the present invention and the device according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0028] FIG. 1 schematically shows a top view of a vehicle 1 which includes one detection unit 2 on each of the four vehicle corners. Detection units 2 may be, for example, ultrasonic sensors, radar sensors or laser sensors which emit transmission signals (Tx) 6 and receive received signals (Rx) 7 reflected on objects within detection areas 4. Due to the transceiver characteristics of detection units 2, a detection area 4 results for each sensor. The direction in which detection unit 2 has the greatest range within detection area 4 is mostly defined as sensor main beam direction 3. Sensor main beam directions 3, which mostly also form the axis of symmetry of detection area 4, are represented as lines through origin, through detection units 2, in FIG. 1. The alignments of sensor main beam directions 3 in this case are not intended to be in parallel to vehicle longitudinal axis 16, which would then be aligned in parallel to direction of travel v of vehicle 1, but rather deviate at an angle between 0° and 90° with respect to vehicle longitudinal axis 16. In this case, the alignment angles on the left vehicle side are mostly mirror-symmetrical with respect to the alignment angles of the sensors on the right vehicle side, so that vehicle longitudinal axis 16 advantageously forms an axis of symmetry with respect to the sensor arrangement of detection units 2 and with respect to their sensor main beam directions 3.

[0029] Detection areas 4 of front detection units 2 and detection areas 4 of rear detection units 2 overlap ahead of vehicle 1 in direction of travel v and behind vehicle 1, respectively, and form overlap areas 5. Detection areas 4 of detection units 2 may also be configured, of course, in such a way that overlap areas 5 may also form next to vehicle 1, on the left and on the right as viewed in direction of travel v, which is not represented in FIG. 1, however, for the sake of clarity. Moreover, with respect to detection units 2 mounted on the rear of the vehicle, two vehicle longitudinal axes 17, shifted in parallel, are aligned in parallel to vehicle longitudinal axis 16, and each extend through detection units 2. These vehicle longitudinal axes 17, shifted in parallel, form an angle γ with the particular assigned sensor main beam directions 3, which may be defined, in each case, as the angular difference between vehicle longitudinal axis 16 and sensor main beam direction 3. Within the scope of the present invention, deviations of the actual sensor main beam directions 3 from the alignments of sensor main beam directions 3 provided due to the design are to be detected and gathered in terms of the order of magnitude thereof. Depending on the extent of the deviation, a compensation of these misalignments is carried out and, if a maximum compensation range is exceeded, a shutoff of particular detection unit 2 is carried out.

[0030] The schematic configuration of the device according to the present invention is represented in FIG. 2 with the aid of block diagrams. Four detection units 2a, 2b, 2c, 2d are shown, which each emit a transmission signal Tx 6a, 6b, 6c, 6d, into their particular detection area 4, in order to detect objects which may be present within detection area 4. Objects 15a, 15b are provided within detection areas 4, on which transmission signals Tx 6a, 6b, 6c are partially reflected and are received as received signals Rx 7a, 7b, 7c by detection units 2a, 2b, 2c. In this case, object 15a is represented as an object which is detected by detection unit 2a. Object 15b, which is detected both by detection unit 2b and by detection unit 2c in this case, should be one and the same object in this case, which is detected simultaneously by two detection units 2b, 2c and is therefore located in overlap area 5 of two detection areas 4. According to the representation in FIG. 2, there is no object present for detection unit 2d to detect. The received signals are evaluated in particular detection units 2a, 2b, 2c, 2d, and the corresponding object data are forwarded to an evaluation unit 8 via data lines 9a, 9b, 9c, 9d. This evaluation unit 8 is represented as a central evaluation unit and receives from detection units 2a, 2b, 2c, 2d the positions of objects 15a, 15b detected in detection areas 4. On the basis of the relative position data from detection units 2a to 2d, evaluation unit 8 may calculate object coordinates for objects 15a, 15b, which are then transferred to a vehicle-based coordinate system. This evaluation of the object data and the ascertainment of object data in the vehicle system may also optionally take place in detection units 2a through 2d. In this case, it is detected, for example, that object 15b was detected simultaneously by two detection units 2b, 2c and lies in overlap area 5 of two detection areas 4. The coordinates of detected objects 15a, 15b may be routed via an interface 10 of a data exchange system to data exchange system 11 which may be designed, for example, as a bus system, in particular as a CAN bus. The data routed to data exchange system 11 via interface 10 may be utilized in driver assistance systems or driver safety systems for comfort functions or safety functions. In order to ensure the reliable operation of the system, sensor main beam directions 3 of individual detection units 2a to 2d must be regularly monitored for correct alignment. This monitoring of the misalignment or the ascertainment of the instantaneous misalignment angle advantageously takes place, in this case, in individual detection units 2a through 2d. Alternatively, it is also possible, however, that the monitoring and ascertainment of the instantaneous misalignment angle takes place centrally in evaluation unit 8. For this purpose, it is continuously monitored whether specific object situations are present, i.e., in particular whether extended objects are detected on the left or on the right in the direction of travel, or on both sides of the vehicle. If such a specific object situation is detected, the measured angles of the object reflections with respect to particular sensor main beam direction 3 of detection area 4 are measured and are averaged over a longer time period.

[0031] In addition, the intended installation angle of particular detection unit 2, which indicates the difference angle between vehicle longitudinal axis 16 and sensor main beam direction 3 of detection units 2, may be stored. The position of the object reflection with respect to vehicle longitudinal axis 16 may be indicated on the basis of the difference between these two angle values. In the detected specific object situation, namely the detection of an extended object such as, for example, a guardrail, a concrete wall, a bridge railing, a tunnel wall, or a similar structure on the edge of the road, transmission signals Tx from detection units 2 are reflected back on the object surface at a right angle and are received as received signals Rx. As a result, the object reflection points are positioned at an angle of approximately exactly 90° with respect to vehicle longitudinal axis 16. If one subtracts 90° therefrom or adds 90° thereto, depending on the vehicle side and depending on the sign orientation of the detection areas, an averaged angle value is obtained, which corresponds to the averaged misalignment angle. A deviation on the one vehicle side toward positive angular deviations and a deviation having approximately the same order of magnitude on the other side of the vehicle toward negative angle values allows for a cross adjustment between detection unit 2 mounted on the left side of vehicle 1 and detection unit 2 mounted on the right side of vehicle 1.

[0032] This measuring method is also represented in FIG. 3 by way of example. Vehicle 1 is also represented, which moves at velocity v in the direction of the arrow in a lane of road 12. Vehicle longitudinal axis 16 is represented in the center of the vehicle by a dash-dotted line. An extended object 13, for example, a guardrail, is represented on the right side of the vehicle, in parallel to the road. A further extended object 14 is represented on the left side of the vehicle, likewise in parallel to direction of travel v of vehicle 1, which may likewise be a guardrail or a concrete wall. In addition, detection units 2 are mounted on both rear vehicle corners, which have approximately diagonally aligned sensor main beam directions 3, but which may also have other angle values between 0° and 90°. These main beam directions 3 are aligned symmetrically at an angle γ with respect to auxiliary axes 17 which are situated in parallel to the vehicle longitudinal axis and extend through detection units 2.

[0033] Due to the emission of transmission signals Tx 6 by detection units 2, radar waves or microwaves, for example, are radiated into the vehicle surroundings and are partially reflected on extended objects 13, 14. These reflected partial waves 7 are received by detection units 2 as received signals Rx, and their relative angle with respect to particular sensor main beam direction 3 is measured. On the basis of the knowledge of this object angle and the difference angle γ, and on the basis of the knowledge that the object reflections on extended objects 13 and 14 are reflected at a right angle, an instantaneous misalignment angle may be determined and may be ascertained for a predetermined time period. On the basis of the knowledge of the individual misalignment angle values and on the basis of the knowledge of the deviations on the left side of vehicle 1 and on the right side of vehicle 1, the alignments of main beam directions 3 of detection units 2 may be recalibrated, since their intended alignment with respect to vehicle longitudinal axis 16 is known in the sensors. The calibration takes place in this case in such a way that a deviation of the averaged object angles is added to all measured object angles as a compensation angle or a correction value.

[0034] If a threshold value for a misalignment angle is exceeded, it may be inferred that this is not only a slight misalignment, but rather that a greater misalignment of detection unit 2 has occurred as a result of an accident or a collision, and individual detection unit 2 or the entire system is shut off.