DE102012024998A1 - Method for determining lateral velocity of target object relative to motor vehicle by driver assistance system of motor vehicle, involves detecting value of radial velocity to two target echoes - Google Patents

Abstract

The method involves transmitting a transmission signal in the detection regions (9,10) of radar sensors (5,6) by the radar sensors in successive measurement cycles. A signal reflected from the target object is received as receiving signal by the radar sensors. A target echo of the target object is detected on the basis of the receiving signal. A radial velocity and a target angle to the target echo are determined relative to the vehicle by the radar sensor. Two target echoes are detected to the target object. A value of the radial speed to the two target echoes and a value of the target angle are determined. The lateral velocity of the target object is determined depending on the two values of the radial velocity and the two values of the target angle.

Description

The invention relates to a method for determining a lateral velocity of a target object relative to a motor vehicle by means of a driver assistance system of the motor vehicle, wherein in each case a transmission signal is emitted in a detection range of the radar sensor by means of at least one radar sensor of the driver assistance system in successive measurement cycles and a signal reflected by the target object is received as a received signal by the radar sensor. At least one target echo of the target object or at least one reflection from the target object is detected based on the received signal, and a radial velocity and a target angle relative to the motor vehicle are determined by the radar sensor for the target echo. The invention also relates to a driver assistance system for a motor vehicle and to a motor vehicle having such a driver assistance system.

Radar sensors for motor vehicles (automotive radar sensors) are already state of the art and are operated, for example, at a frequency of about 24 GHz or about 79 GHz. Radar sensors generally serve to detect targets in the vicinity of the motor vehicle and assist the driver in guiding the motor vehicle in a variety of ways. In the present case, the interest applies in particular to a blind spot warning system by means of which the driver is warned of the presence of target objects in the blind spot area of the motor vehicle.

On the one hand, radar sensors measure the distance between the target object and the vehicle. On the other hand, they also measure both the relative speed to the target object and the so-called target angle, d. H. an angle between an imaginary connecting line to the target object and a reference line, such as the vehicle longitudinal axis. Consequently, the respective current position of the target object relative to the vehicle can be determined with the aid of a radar sensor, and the target object can be tracked in the detection area of the radar sensor, ie. H. the relative position of the target object can be continuously determined over a plurality of measurement cycles of the radar sensor. The "tracking" succeeds under the condition that the reflection points detected at the target object remain stable over the measuring cycles.

Radar sensors are usually placed behind the bumper, for example in the respective corners of the rear bumper. To detect the target object, the radar sensor emits a transmission signal (electromagnetic waves), which is then reflected at the target object to be detected and received as a radar echo by the radar sensor. In the present case, in particular, the so-called frequency modulation continuous wave ("Frequency Modulated Continuous Wave Radar" or "FMCW Radar") radar sensor, in which the emitted signal comprises a burst of frequency-modulated chirp signals, which are transmitted one after the other become. Correspondingly, the received signal of the radar sensor also contains such a multiplicity of chirp signals which are processed and evaluated with regard to the aforementioned measured quantities. The received signal is first mixed down into the baseband and then converted by means of an analog-to-digital converter into a digital received signal with a plurality of samples and FFT-transformed (Fast Fourier Transformation). The samples are then processed by means of an electronic computing device (digital signal processor) in the time domain and / or in the frequency domain.

With a radar sensor, a relatively wide azimuthal angular range, which can even be 150 °, is typically detected in the horizontal direction. The radar sensor thus has a relatively large azimuthal detection angle, so that the field of view or the detection range of the radar sensor is correspondingly wide in the azimuth direction. The azimuthal detection angle is usually symmetrical with respect to a radar axis perpendicular to the front sensor surface, so that the azimuthal detection angle of, for example, -75 ° to + 75 ° with respect to the radar axis is measured. This azimuthal detection area can be subdivided into smaller partial areas, which are irradiated or detected one after the other by the radar sensor. For this purpose, for example, the main lobe of the transmitting antenna is pivoted electronically in the azimuth direction, for example, according to the phase array principle. The receiving antenna may in this case have a reception characteristic in the azimuth direction, with which the entire azimuthal detection range is covered. Such a radar sensor is for example from the document DE 10 2009 057 191 A1 known. Another radar sensor is from the document US 2011/0163909 to be known as known.

With the aid of a radar sensor, therefore, it is also possible to monitor a lateral surrounding area next to the motor vehicle, and in particular also a blind spot area of the motor vehicle. In the present case, the interest is preferably directed to the monitoring of a proximity area laterally next to the motor vehicle with regard to target objects possibly located there, which could represent a danger when changing lanes. The interest is therefore in a driver assistance functionality known as "lateral collision avoidance". Here, the driver of the motor vehicle - for example, with an audible signal and / or with a haptic feedback on the steering wheel - warned against a small distance to a side, adjacent vehicle. Such a driver assistance system is also known under the name "lane change assistant".

For the aforementioned driver assistance functionality and also for other functionalities, it is necessary to determine the lateral velocity of a target object in the near range with a relatively high accuracy in order to be able to precisely estimate the danger. In the present case, the lateral velocity is understood to be the velocity component in the vehicle transverse direction, that is to say the speed with which the target object moves in the vehicle transverse direction relative to the motor vehicle. The determination of the lateral velocity component should take place very quickly, namely within a few measurement cycles of the radar sensor, particularly preferably within a single measurement cycle.

However, the radar sensor alone measures only the radial velocity of a target object by the Doppler effect. As already stated, the measured variables of a radar sensor, in particular a frequency modulation continuous wave radar sensor, in addition to the radial relative velocity also include the target angle of the target object and the distance of the target object. The radial velocity component represents the relative velocity between the target object and the radar sensor in the direction of an imaginary connecting line between target object and radar sensor. Only this radial velocity can be measured by means of a radar sensor, the lateral velocity can only be calculated.

If the target object is tracked in the detection area by means of a radar sensor, the lateral velocity component and also the longitudinal velocity component (in the vehicle longitudinal direction) can also be estimated by means of a Kalman filter. In estimating the lateral velocity component using the Kalman filter, however, a stable reflection of the target object over several measurement cycles is assumed, which means that a detected reflection point of the target echo on the surface of the target echo must not shift over time. The exact estimate here requires a very large number of measurement cycles, and in practice the estimation of the lateral velocity often contains large errors.

Because of the problems with lateral velocity determination, blind spot detection functionality has heretofore set the lateral velocity component to zero because it caused far-field defects in tracking the target objects. This was necessary because the tracking algorithm (tracker) automatically calculated a lateral velocity, but this was strongly distorted by the inaccuracy of the target angle determination or by the angular noise. So far, only the longitudinal velocity relative to the motor vehicle has been determined from the radial velocity and the lateral velocity has been set to zero.

As already mentioned, the information about the actual lateral relative speed between motor vehicle and target object is required in some driver assistance functionalities.

It is an object of the invention to provide a solution, as in a method of the type mentioned, the lateral velocity of the target object can be determined precisely and quickly.

This object is achieved by a method by a driver assistance system and by a motor vehicle with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures.

An inventive method is used to determine a lateral velocity of a target object relative to a motor vehicle by means of a driver assistance system of the motor vehicle. By means of at least one radar sensor of the driver assistance system, in successive measuring cycles, in each case a transmission signal, for example a sequence of chirp signals (chirps), is emitted into a detection range of the radar sensor, and a signal reflected by the target object is received as a reception signal by the radar sensor. On the basis of the received signal, at least one target echo of the target object is detected. To the target echo then the radial velocity and the target angle are measured relative to the motor vehicle by means of the radar sensor. According to the invention, at least two target echoes are detected for the target object, and for each target echo a value pair is determined from a value of the radial velocity and a value of the target angle, and the lateral velocity of the target object is dependent on the at least two value pairs and thus is determined as a function of the at least two values of the radial velocity and the at least two values of the target angle.

wobei φ den Zielwinkel, V_long die longitudinale Geschwindigkeitskomponente, V_lat die laterale Geschwindigkeitskomponente und v_R die gemessene Radialgeschwindigkeit bezeichnen. Bei einer einzelnen Detektion bzw. bei einem einzelnen Zielecho ist dieses Gleichungssystem zur Ermittlung der lateralen Geschwindigkeit unterbestimmt. Sind aber mehrere Zielechos vorhanden, zu denen jeweils die Radialgeschwindigkeit und der Zielwinkel gemessen werden, kann ein Gleichungssystem aufgestellt und nach der lateralen Geschwindigkeitskomponente und gegebenenfalls auch nach der longitudinalen Geschwindigkeitskomponente aufgelöst werden. Die laterale Geschwindigkeitskomponente kann also aus mehreren Radialgeschwindigkeitsmessungen bei verschiedenen Zielwinkeln bestimmt werden. Hierbei unterliegt die Zielwinkelmessung auch einer relativ hohen Varianz, was sich als vorteilhaft im Hinblick auf die Lösung des Gleichungssystems erweist. Insgesamt kann durch das erfindungsgemäße Verfahren die laterale Geschwindigkeitskomponente des Zielobjekts relativ zum Kraftfahrzeug präzise und besonders schnell, gegebenenfalls auch innerhalb eines einzelnen Messzyklus, bestimmt werden.The invention takes advantage of the fact that other road users, which represent extended to the radar sensor target objects that are larger than a resolution cell of the radar sensor, usually several reflections and thus a total of multiple target echoes arise, which are measured in distance, radial velocity and target angle by means of the radar sensor. This means that the transmitted transmission signal is typically reflected at a multiplicity of different reflection points of the target object, so that a multiplicity of target echoes, which are evaluated in each case with respect to distance, radial velocity and target angle, exist for the same target object. Assuming that the target echoes originate from one and the same target object, in particular in a predetermined near range, all relevant detections from one or more measurement cycles can be used to determine the lateral velocity component. The invention is based on the fact that for a single target echo the relationship between the measured radial velocity and the lateral velocity component as well as the longitudinal velocity component can be represented by the following equation:

where φ denotes the target angle, V _long the longitudinal velocity component, V _lat the lateral velocity component, and v _R the measured radial velocity. In a single detection or in a single target echo, this system of equations for determining the lateral velocity is underdetermined. However, if there are several target echoes for which the radial velocity and the target angle are respectively measured, a system of equations can be set up and resolved according to the lateral velocity component and possibly also according to the longitudinal velocity component. The lateral velocity component can therefore be determined from several radial velocity measurements at different target angles. Here, the target angle measurement is subject to a relatively high variance, which proves to be advantageous in terms of solving the equation system. Overall, the lateral velocity component of the target object relative to the motor vehicle can be determined precisely and particularly quickly, if appropriate also within a single measurement cycle, by the method according to the invention.

With regard to the origin of the at least two target echoes of the same target object, a wide variety of embodiments can be provided:
According to one embodiment, it is provided that at least two target echoes, to each of which a value of the radial velocity and a value of the target angle are determined and on the basis of which the lateral velocity is determined, are detected in different measurement cycles of the radar sensor. This means that at least two target echoes originating from different, in particular temporally immediately adjacent, measuring cycles are used to determine the lateral velocity. This embodiment proves to be particularly advantageous in a relatively small target object, in which only a few reflection points are present. The target echoes from this target object can be collected over several measurement cycles and used to determine the lateral velocity.

Additionally or alternatively, at least two target echoes, for each of which a value of the radial velocity and a value of the target angle are determined and by means of which the lateral velocity is determined, can be detected in a single measurement cycle of the radar sensor. Thus, multiple target echoes from one and the same measurement cycle can be used to determine the current lateral velocity component of the target echo. This embodiment enables a particularly rapid determination of the lateral velocity within a single measurement cycle or, if appropriate, within a few measurement cycles.

Furthermore, additionally or alternatively, it is also possible to use target echoes, which are detected by at least two different or separate radar sensors, for determining the lateral velocity. This embodiment also makes it possible to determine the lateral velocity of the target echo within a very short time, since target echoes of different radar sensors are used. Here, the fact is used that in today's motor vehicles typically not a single radar sensor, but in each case at least two radar sensors are used, which monitor the environment of the motor vehicle. If, for example, at least one radar sensor in the front region and at least one radar sensor in the rear region of the motor vehicle are used, with the respective detection regions overlapping, target echoes can be detected by both radar sensors simultaneously for one and the same target object. Each radar sensor then supplies in each case at least one value of the radial velocity and at least one value of the target angle, so that the lateral velocity of the target object can then be determined on the basis of these values. Consequently, with at least two radar sensors, the determination of the lateral velocity is accelerated.

The lateral velocity of the target object may be determined as a function of the at least two values of the radial velocity and the at least two values of the target angle, preferably for a short range in the surroundings of the motor vehicle predetermined in relation to the motor vehicle, in particular exclusively for this predetermined short range. Namely, in a near range, it can be assumed that the target echoes received by the radar sensor originate from one and the same target object. This assumption does not necessarily apply to a long range or to target objects located at a greater distance from the motor vehicle.

However, the method can also be applied to the far-end, for example, by grouping target echoes that belong to the same target object. In this case, the destination echoes can be grouped according to predetermined criteria and assigned to a specific destination object. Such algorithms are already used in the tracking of the target objects.

As a close range, an area is preferably predefined laterally next to the vehicle. In this way, the lateral velocity of target objects can be determined, which are located directly next to the motor vehicle (in the vehicle transverse direction), so that the aforementioned assistance functionality "lateral collision avoidance" can be provided and thus lateral collisions of the motor vehicle with other road users are effectively prevented can. For example, thus the driver of the motor vehicle can be supported when changing lanes or warned of obstacles.

Preferably, the short-range in the vehicle transverse direction has a width which is in a value range of 2 m to 4 m, in particular 3 m. This width is preferably measured starting from the side edge of the motor vehicle in the vehicle transverse direction. The near zone is preferably a rectangular area laterally adjacent to the vehicle. The short-range can extend in the vehicle longitudinal direction up to a distance value of 2 m to 4 m in front of the motor vehicle and / or up to a distance value of 2 m to 4 m behind the motor vehicle. The close range extends, for example, to 3 m in front of the motor vehicle and up to 3 m behind the motor vehicle. Specifically, target objects located in this region present a danger to the motor vehicle, so that the determination of the lateral velocity with regard to the avoidance of lateral collisions, for example when changing lanes, proves to be particularly advantageous.

Preferably, the radar sensor is a frequency modulation continuous wave radar sensor which emits a sequence of chirp signals as a transmission signal in a single measurement cycle.

The detection range of the radar sensor may be divided into a plurality of partial regions or partial angle regions in the azimuth direction, and the partial regions may be detected one after the other by means of the radar sensor. In this case, for example, the main lobe of the transmitting antenna and / or the receiving antenna can be electronically pivoted in the azimuth direction in order to be able to detect a relatively wide detection range with a relatively narrow main lobe. In this embodiment, in each case one transmission signal per sub-area or per "beam" is emitted by the radar sensor in a single measurement cycle, with each transmission signal comprising a multiplicity of chirp signals. To determine the lateral velocity of the target object, preferably only target echoes from a predetermined subset of the subregions may be used. For example, the middle three or the middle five sub-areas from a total of seven areas can be taken into account.

Alternatively, target echoes from all subareas can also be taken into account.

The method can also be advantageously applied to a radar sensor in which no pivotable antenna lobe is provided and which thus has only a single "beam".

wobei V_long die longitudinale Geschwindigkeit des Zielobjekts, V_lat die zu bestimmende laterale Geschwindigkeit, A^inv die Pseudoinverse einer Winkelmatrix A umfassend die zumindest zwei Werte des Zielwinkels und V →_R einen Radialgeschwindigkeitsvektor umfassend die zumindest zwei Werte der radialen Geschwindigkeit bezeichnen. Die Matrix A ist also eine Matrix, die sich aus den verschiedenen Winkeln der Zielechos ergibt, wobei die Matrix A^inv die pseudoinverse Matrix der A darstellt. Durch die genannte mathematische Operation lässt sich die laterale Geschwindigkeit des Zielobjekts, insbesondere im Nahbereich, sehr präzise und schnell berechnen. Die pseudoinverse Matrix hat außerdem den Vorteil, dass die Varianz der Schätzung der lateralen Geschwindigkeitskomponente minimiert werden kann. Durch die Bestimmung der lateralen Geschwindigkeit mit Hilfe der pseudoinversen Matrix wird das sogenannte Verfahren der minimalen mittleren quadratischen Abweichung (Minimum Mean Square Error) verwendet.The lateral velocity of the target object is determined as a function of the at least two values of the radial velocity and the at least two values of the target angle, preferably according to the following formula:

where V _{long is} the longitudinal velocity of the target object, V _{lat is} the lateral velocity to be determined, A ^{inv is} the pseudoinverse of an angle matrix A comprising the at least two values of the target angle and V → _R a radial velocity vector comprising the at least two values of the radial velocity. The matrix A is therefore a matrix which results from the different angles of the target echoes, where the matrix A ^{inv represents} the pseudoinverse matrix of A. By the mentioned mathematical operation, the lateral velocity of the target object can be calculated very precisely and quickly, in particular in the near field. The pseudo-inverse matrix also has the advantage of minimizing the variance of the lateral velocity component estimate can. By determining the lateral velocity with the help of the pseudoinverse matrix, the so-called minimum mean square error method is used.

The invention also relates to a driver assistance system having a radar sensor for carrying out a method according to the invention. An inventive motor vehicle, in particular a passenger car, comprises a driver assistance system according to the invention. The preferred embodiments presented with reference to the method and their advantages also apply correspondingly to the driver assistance system according to the invention and the motor vehicle.

Further features of the invention will become apparent from the claims, the figures and the description of the figures. All the features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively indicated combination but also in other combinations or alone.

The invention will now be described with reference to a preferred embodiment and with reference to the accompanying drawings.

Show it:

1 a schematic representation of a motor vehicle with a driver assistance system according to an embodiment of the invention; and

2 a schematic representation of the motor vehicle, wherein a method is explained in more detail according to an embodiment.

An in 1 illustrated motor vehicle 1 is for example a passenger car. The car 1 comprises a driver assistance device or a driver assistance system 2 , which the driver while driving the motor vehicle 1 supported. The driver assistance system 2 is for example a blind spot warning system and / or a lane change assistant and / or a collision avoidance system for lateral collisions (lateral collision avoidance system).

To the driver assistance system 2 include two radar sensors 5 . 6 behind a rear bumper 4 of the motor vehicle 1 are arranged concealed. The first radar sensor 5 is located in a left rear corner area while the second radar sensor 6 in a right rear corner region of the motor vehicle 1 is arranged. Both radar sensors 5 . 6 are behind the bumper 4 and are thus from outside the vehicle 1 not visible.

The driver assistance system 2 can also use additional radar sensors 13 . 14 have, in the front corner regions of the motor vehicle 1 are arranged.

The radar sensors 5 . 6 . 13 . 14 are in the embodiment frequency modulation continuous wave radar sensors (FMCW). The radar sensors 5 . 6 . 13 . 14 each have an azimuthal detection range 4 ), which in 1 through two lines 7a . 7b (for the left rear radar sensor 5 ) respectively. 8a . 8b (for the right rear radar sensor 6 ) is limited. The azimuthal detection angle φ is for example 150 °. By this angle φ is in each case a field of view or detection area 9 respectively. 10 of the respective radar sensor 5 . 6 defined in the azimuth direction and thus in the horizontal direction. Corresponding detection areas also have the radar sensors 13 . 14 on. The fields of view 9 . 10 can also overlap each other, leaving an overlap area 11 given is.

Every radar sensor 5 . 6 . 13 . 14 includes an integrated computing device, for example in the form of a digital signal processor, which the radar sensor 5 . 6 . 13 . 14 controls and also processes the received signals and evaluates. Alternatively or in addition, but also one for all sensors 5 . 6 . 13 . 14 be provided common and external computing device, which then the received signals of the sensors 5 . 6 . 13 . 14 can handle.

In their respective fields of view 9 . 10 can the radar sensors 5 . 6 vehicle-external target objects 12a (left) and 12b (right) detect. In particular, the radar sensors can 5 . 6 the removal of the target objects 12a respectively. 12b from the respective radar sensor 5 . 6 , as well as the target angle and the relative speed of the target objects 12a respectively. 12b with respect to the motor vehicle 1 determine - these are measured variables of the radar sensors 5 . 6 ,

Referring still to 1 can the radar sensor 5 - and analogously, the sensors 6 . 13 . 14 - Different sections A, B, C, D, E, F, G of the azimuthal field of view 9 irradiate one after the other. These subareas A to G represent angular ranges, wherein for detecting the subregions A to G successively, for example, a transmitting lobe of the transmitting antenna of the radar sensor 5 is pivoted electronically in the azimuth direction, namely according to the phase array principle. The different orientations of the transmission lobe are in 1 for the different sections A to G schematically indicated. The receiving antennas of the radar sensor 5 can have a broad receiving characteristic in the azimuth direction overall, with which the entire azimuthal field of view 9 is covered. Other embodiments may alternatively realize narrow receive angle ranges in conjunction with broad transmit lobes.

In 1 For clarity, only the partial areas A to G of the field of view 9 of the first radar sensor 5 shown. Corresponding here, however, is the horizontal field of view 10 of the second radar sensor 6 divided into several subareas. Although the further description on the operation of the first sensor 5 refers, corresponds to the operation of the sensors 6 . 13 . 14 that of the first sensor 5 ,

The number of subareas A to G is in 1 merely exemplified and may vary depending on the embodiment. In the exemplary embodiment, a total of seven partial areas A to G are provided, which are arranged one after the other by the radar sensor 5 be illuminated. But it can also be provided four such "beams" or it may also be provided only a single "beam".

The operation of the radar sensor 5 is as follows: In a single measurement cycle of the radar sensor 5 the main lobe of the transmitting antenna is once pivoted gradually from the portion A to the portion G, so that the portions A to G are illuminated one after the other. In each case, a temporal sequence of frequency-modulated chirp signals (chirps) is emitted for each subarea A to G. First, such a sequence of chirp signals is sent out for the subarea A. After a given transmission pause, a sequence of chirp signals is then sent out into the subarea B. After another predetermined transmission break then the sub-area C is irradiated, etc.

The driver assistance system 2 monitors one in 2 schematically shown short-range 15 in the vehicle transverse direction y laterally next to the motor vehicle 1 , Such a close range 15 can also be provided on the right side of the vehicle, with in 2 for the sake of clarity, the close range is simply unavoidable 15 is shown on the left side. The close range 15 has a width 16 for example, 3 m starting from the side edge of the motor vehicle 1 , In the vehicle longitudinal direction x, the rectangular short range extends 15 up to a distance of 3 m in front of the motor vehicle 1 and up to a distance of 3 m behind the motor vehicle 1 ,

Is located in the vicinity 15 , which also the blind spot area of the motor vehicle 1 includes, a target object 12 , such as another vehicle, becomes the lateral velocity V _{lat of} the target object 12 certainly. In addition, the longitudinal velocity V _long in the vehicle longitudinal direction x can also be determined. The lateral velocity V _lat becomes relative to the motor vehicle 1 determined in the transverse direction y. The target object 12 For example, it moves in accordance with the velocity vector V →.

With the radar sensor 5 and optionally also the radar sensor 13 is the radial velocity V _R and said target angle φ and the distance R measured. The target angle φ is, for example, the angle between a radar sensor 5 with the target object 12 connecting imaginary connecting line 17 and a reference line 18 , For example, the reference line runs 18 perpendicular to a front surface of the radar sensor 5 , namely perpendicular to the radome. Optionally, as a reference line 18 also the vehicle longitudinal axis x or the transverse axis y are selected.

In each measurement cycle causes the target object 12 in the received signal multiple target echoes, because the emitted radar signal at different reflection points of the target object 12 is reflected. Thus, several target echoes and thus several values of the target angle φ as well as several values of the radial velocity v _R are available per measuring cycle. If necessary, these values can also be collected over several measuring cycles.

Either destination echoes from all subareas A to G or from a predefined subset of subareas A to G can be taken into account. For example, to determine the lateral velocity V _lat, only the middle five partial regions B to F are taken into account.

To determine the current lateral velocity V _{lat of} the target object 12 Thus, N value pairs are each available from a value of the radial velocity v _R and a value of the target angle φ. In general:

wobei V →_R einen Radialgeschwindigkeitsvektor mit mehreren Werten der Radialgeschwindigkeit v_R und A eine Winkelmatrix mit Winkelwerten bezeichnen. Die Matrix A ist eine Matrix, die sich aus den verschiedenen Werten des Zielwinkels φ der entsprechenden Zielechos ergibt und folgendermaßen aufgestellt ist:

If there are N value pairs, a system of equations with N equations in matrix notation results:

in which V → _R a radial velocity vector having a plurality of values of the radial velocity v _R and A denotes an angle matrix with angle values. The matrix A is a matrix which results from the different values of the target angle φ of the corresponding target echoes and is arranged as follows:

The lateral velocity V _lat and the longitudinal velocity V _long can be determined according to the following equation system:

The matrix A represents the pseudoinverse matrix determined according to the following equation: A ^inv = (A ^T * A) ^-l * A ^T

These mathematical operations allow the lateral velocity V _lat and the longitudinal velocity V _{long of} the target object to be determined 12 relative to the motor vehicle 1 calculate very accurately and quickly. This method is preferably applied to the lateral and longitudinal velocity components V _lat and V _{long of} the target object 12 in the mentioned vicinity 15 next to the motor vehicle 1 appreciate. Optionally, however, this method can also be used for the far-end, in which case an assignment of target echoes to a specific target object 12 is to be made.

The different values of the radial velocity v _R and the target angle φ come from a single measurement cycle or from several measurement cycles of the radar sensor 5 , Optionally, measurements of one of the other sensors can also be used to determine the lateral velocity V _lat 6 . 13 . 14 be used. In particular, according to the embodiment 2 the measurements of the front radar sensor 13 in consideration, because the detection ranges of the radar sensors 5 and 13 can overlap laterally.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009057191 A1 [0005]
• US 2011/0163909 [0005]

Claims (11)

Method for determining a lateral velocity (V _lat ) of a target object ( 12 ) relative to a motor vehicle ( 1 ) by means of a driver assistance system ( 2 ) of the motor vehicle ( 1 ), in which by means of at least one radar sensor ( 5 . 6 . 13 . 14 ) of the driver assistance system ( 2 ) in successive measuring cycles in each case a transmission signal in a detection area ( 9 . 10 ) of the radar sensor ( 5 . 6 . 13 . 14 ) and one of the target object ( 12 ) reflected signal as received signal by the radar sensor ( 5 . 6 . 13 . 14 ), wherein based on the received signal at least one target echo of the target object ( 12 ) and to the target echo a radial velocity (v _R ) and a target angle (φ) relative to the motor vehicle ( 1 ) by means of the radar sensor ( 5 . 6 . 13 . 14 ), characterized in that to the target object ( 12 ) at least two target echoes are detected and for the at least two target echoes each a value of the radial velocity (v _R ) and a value of the target angle (φ) are determined, and that the lateral velocity (V _lat ) of the target object ( 12 ) is determined as a function of the at least two values of the radial velocity (v _R ) and the at least two values of the target angle (φ). A method according to claim 1, characterized in that at least two target echoes, to each of which a value of the radial velocity (v _R ) and a value of the target angle (φ) are determined in different measuring cycles of the radar sensor ( 5 . 6 . 13 . 14 ) are detected. A method according to claim 1 or 2, characterized in that at least two target echoes, to each of which a value of the radial velocity (v _R ) and a value of the target angle (φ) are determined, in a single measurement cycle of the radar sensor ( 5 . 6 . 13 . 14 ) are detected. Method according to one of the preceding claims, characterized in that at least two target echoes, to each of which a value of the radial velocity (v _R ) and a value of the target angle (φ) are determined by at least two different radar sensors ( 5 . 6 . 13 . 14 ) are detected. Method according to one of the preceding claims, characterized in that in relation to the motor vehicle ( 1 ) predetermined close range ( 15 ), in particular only in the predetermined near range ( 15 ), the lateral velocity (V _lat ) of the target object ( 12 ) is determined as a function of the at least two values of the radial velocity (v _R ) and the at least two values of the target angle (φ). A method according to claim 5, characterized in that as close range ( 15 ) an area laterally next to the motor vehicle ( 1 ) is given. Method according to claim 5 or 6, characterized in that the width of the near zone ( 15 ) in the vehicle transverse direction (y) is in a value range of 2 m to 4 m, in particular 3 m, and / or the predetermined short-range ( 15 ) in the vehicle longitudinal direction (x) up to a distance of 2 m to 4 m in front of the motor vehicle ( 1 ) and / or up to a distance of 2 m to 4 m behind the motor vehicle ( 1 ) enough. Method according to one of the preceding claims, characterized in that the detection area ( 9 . 10 ) of the radar sensor ( 5 . 6 . 13 . 14 ) is divided in Azimutrichtung into a plurality of subregions (A to G) and by means of the radar sensor ( 5 . 6 . 13 . 14 ) the subregions (A to G) are detected one after the other, wherein for the determination of the lateral velocity (V _lat ) of the target object ( 12 ) exclusively destination echoes from a given subset of the subareas (A to G) are used. Method according to one of the preceding claims, characterized in that the lateral velocity (V _lat ) of the target object ( 12 ) is determined as a function of the at least two values of the radial velocity (v _R ) and the at least two values of the target angle (φ) according to the following formula:

where V _{long is} a longitudinal velocity of the target object ( 12 ), V _lat the lateral velocity to be determined, A ^inv the pseudoinverse of an angle matrix (A) comprising the at least two values of the target angle (φ) and V → _R a radial velocity vector comprising the at least two values of the radial velocity (v _R ). Driver assistance system ( 2 ) for a motor vehicle ( 1 ), with a radar sensor ( 5 . 6 . 13 . 14 ) for carrying out a method according to one of the preceding claims. Motor vehicle ( 1 ) with a driver assistance system ( 2 ) according to claim 10.

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