WO2008058777A1

WO2008058777A1 - Radar system for motor vehicles

Info

Publication number: WO2008058777A1
Application number: PCT/EP2007/059267
Authority: WO
Inventors: Dieter Hoetzer; Thomas Kropf
Original assignee: Robert Bosch Gmbh
Priority date: 2006-10-23
Filing date: 2007-09-05
Publication date: 2008-05-22
Also published as: DE102006049879A1; EP2084554A1; DE102006049879B4

Abstract

Radar system for motor vehicles, having a plurality of radar sensors which are installed at the front of the vehicle (26) and have the purpose of monitoring the area in front of the vehicle, characterized in that at least two of the radar sensors are LRR sensors (16,18).

Description

description

title

Radar system for motor vehicles

State of the art

The invention relates to a radar system for motor vehicles, with a plurality of radar sensors installed in the front of the vehicle for monitoring the apron of the vehicle.

Such radar systems are used in motor vehicles for locating vehicles ahead and for measuring the distances, relative speeds and azimuth angles of these vehicles, so that an automatic distance control (ACC; Adaptive Cruise

Control) and / or an electronic warning system (PSS).

Conventional ACC systems have a single long range radar (LRR) sensor, such as a 76 GHz FMCW radar, which has a detection depth of 100 m or more. From distances of about 20 m, the radar lobe of this sensor is fanned out so far that it covers at least the entire width of the traffic lane traveled by the own vehicle, so that relevant target objects for the distance control can be reliably located. These ACC systems are designed for use on highways or well-developed highways and can only be activated at speeds greater than 30 km / h. In this

Speed range are the usual vehicle distances so large that with a single LRR sensor a sufficiently reliable location of vehicles ahead can be ensured. However, there are so-called ACC FSR systems (Füll Speed Range) in development, whose application is to cover the entire speed range down to zero speed and which should also allow, for example, when driving on a jam end, the own vehicle in the state to brake when the fore vehicle stops. In such ACC FSR systems, additional sensors can be used to monitor the area in front of the vehicle. As proximity sensors, video sensors, LIDAR sensors and short range radar (SRR) sensors have been considered. A typical example of an SRR sensor is a 24 GHz pulse radar, the azimuth of which ranges from about ± 60 °, so that the near range in the front of the vehicle can be monitored almost completely. To increase the positioning security, it is also known to arrange two SRR sensors symmetrically on either side of the longitudinal central axis of the vehicle.

German Patent Application 10 2006 032 539 proposes an LRR FMCW sensor in which the beam expansion can be varied by utilizing interference effects.

Disclosure of the invention

The object of the invention is to provide a cost-effective radar system for motor vehicles, which allows monitoring of both the long range and the near range and in particular allows good coverage of the near front area.

This object is achieved in that at least two of the more

Radar sensors are LRR sensors.

The detection ranges of the at least two LRR sensors can be adapted so that only with these LRR sensors in addition to a long-range detection also for the purposes of FSR systems appropriate Nahbereichsortung is made possible. The advantage is that in this way the complexity of the radar system can be reduced by installing only a single type of sensor. In addition, there are rationalization effects through the use of identical sensors in a correspondingly larger number. At the same time, this solution is due to the Redundancy in long-range detection achieved a significant improvement in quality, especially in the location of two-wheeled vehicles, in the reduction of secondary lane disorders and in the automatic detection of blindness of one or more of the LRR sensors.

Advantageous developments and refinements of the invention are in the

Subclaims specified.

Good coverage of the near range can be achieved e.g. achieve that the two LRR sensors are mounted in the vicinity of the left and right lateral boundaries of the vehicle, so that in particular Einscherer from the left or right side lane can be detected early. A further improvement can be achieved in that the optical axes of the two sensors are not arranged in parallel, but slightly divergent.

In LRR sensors, where e.g. In the case of an FMCW radar, the frequency of the radar signal is modulated, moreover, the frequency modulation can be varied and thus optimized with regard to the respective relevant distance range.

For example, on low speed trips where short range monitoring is particularly relevant, the frequency of at least one sensor may be modulated with a steeper ramp, thereby providing higher resolution in the distance measurement.

On the other hand, the frequency modulation in at least one of the sensors can be chosen so that in particular the location of two-wheeled vehicles is improved. Unlike a car, in which the rear of the vehicle forms a well-defined reflection surface, there is the problem in a two-wheeler that on the one hand, the total intensity of Radarechos is lower, especially at a large distance, and that on the other radar echoes received from multiple reflex points which are distributed over the length of the two-wheeler, which in an FMCW radar, the signal is additionally smeared over a wider frequency range. For optimal location of two-wheeled vehicles, a frequency modulation with a flatter ramp is therefore more suitable. - A -

To avoid interference between the multiple LLR sensors, it is possible to operate the sensors alternately and / or with slightly different frequencies, frequency characteristics or modulations.

In a system with two LRR sensors, compared to a system with only one LLR sensor, the total amount of data to be evaluated is twice as large. In order to keep the data processing effort within limits, at least in the far-field location, it is therefore expedient if the data of one sensor and of the other sensor are only evaluated alternately from the measuring cycle to the measuring cycle. It is possible, the sensor whose data in the current cycle are not evaluated anyway, during this cycle mute, which also at the same time

Problem of possible interference is eliminated.

In a particularly preferred embodiment, the sensors are operated alternately with different frequency modulation. In each cycle, then the modulation of one sensor can be optimized for the near range, while it is optimized in the other sensor for the long range. In this way, a signal with good distance resolution is obtained both for the left and the right sensor in every second cycle, while at the same time an optimal long-range detection in each cycle is possible by fusion of the data of the two sensors.

Based on the known beam geometry of the sensors, an overlap region can be determined in which an object is located by both sensors. If an object in this overlap area is located by only one of the sensors, this indicates a malfunction, such as blindness due to snow or dirt, from the other sensor. In this way, an increased reliability and self-monitoring of the system is achieved by the invention at the same time.

In a particular embodiment, the optical systems of the LRR sensors may be designed differently so that, for example, one sensor produces a sharper focused radar beam for long-range detection while the other sensor produces a wider-spread beam for near range detection. This can be added grandsätzlich same structure of the sensors simply by a different design and / or arrangement of the radar lenses achieve.

Basically, an adjustment is required for an LRR sensor to ensure proper operation. In the system according to the invention, however, the adjustment process can be simplified in that the adjustment of the second sensor is performed electronically at least in the horizontal, wherein the correctly adjusted first sensor serves as a reference.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

Figure 1 is a block diagram of an ACC system with a radar system according to the invention;

Figure 2 is a schematic diagram for explaining a radar system according to an embodiment of the invention;

FIG. 3 shows a scheme for the frequency modulation of a radar sensor in the system according to the invention; and

Figure 4 is a schematic diagram of a radar system according to another embodiment; and

Figures 5 and 6 are schematic representations of LRR sensors in the

Embodiment of FIG. 4. Embodiments of the invention

In Figure 1, a known per se ACC system 10 for a motor vehicle is simplified as a block. In the example shown, this system includes an ACC FSR controller 12 which provides distance and cruise control over the entire speed range of the vehicle equipped with this system.

For locating objects in the front of the vehicle, a radar system 14 is provided, which is formed in the example shown by two substantially identical LRR sensors 16, 18, for example by FMCW radar sensors. Each of the two LRR sensors 16, 18 is capable of locating the object and measuring its distance and its relative speed as well as calculating its azimuth angle. From the

Distance and the azimuth angle can then calculate the cross-shelf of the object with respect to the transverse position of the respective sensor.

The ACC system 10 includes a fusion device 20 for merging (fusing) the data provided by the two LRR sensors. For example, for each located object, the fusing device 20 is connected to the

Controller 12 only one record transmitted, indicating, for example, the distance, the relative speed and the Querab lags of the object.

The controller 12 includes a mode selector 22 that can be toggled between different modes of operation depending on the vehicle's operating condition, such as between a high speed mode for launches with higher

Speed, where close-range surveillance is not mandatory, and a low-speed-ride Stop & Go mode, where closer, gap-free monitoring of the near range is desired. The manner in which the data is fused in the fusion device 20 may depend on the particular mode of operation. Furthermore, the ACC system 10 includes a driver module 24, which allows the two LRR sensors 16, 18 to be controlled as a function of the respective operating mode with independent driver signals. FIG. 2 shows in sketchy form how the two LRR sensors 16, 18 are installed in a vehicle 26. The two sensors are arranged symmetrically to the longitudinal center axis of the vehicle 26 and are each located in the vicinity of the left or right vehicle boundary. Each of the two sensors generates a divergent Radarkeule 28 and 30, which sweeps over from a certain distance, the entire width of the lane 26 traveled by the vehicle 26. The two radar beams form an overlap zone 34 in which objects from each of the two LRR sensors can be located. At close range, the overlap between the two radar lobes decreases, creating a dead angle 36 that can not be monitored directly. Due to the selected arrangement of the sensors, however, no object can penetrate into this blind spot 36 without first passing through at least one of the radar lobes 28, 30. Thus, seamless monitoring of the apron of the vehicle 26 is ensured even in the vicinity.

The optical axes 38 of the two LRR sensors 16, 18 are not parallel to the longitudinal axis of the vehicle 26, but are each pivoted by an angle d of, for example, 3 ° to the outside. It is thereby achieved that a vehicle 40 shattering about from a secondary lane can be detected earlier. However, since the opening angle of the radar lobes (with, for example ± 8 °) is greater than the angle d, the radar lobes are directed substantially forward.

The radar system 14 can be operated, for example, in the high-speed mode so that in the successive measuring cycles alternately the data of the LRR sensor 16 and the LRR sensor 18 are transmitted from the fusion device 20 to the controller 12. In that case, the driver module 24 may cause the sensor whose data is not needed to remain completely inactive. If the transmitted from the fusion device 20 to the controller 12 data set instead of the cross-placement of the object whose azimuth angle, must be specified in addition, with which of the two sensors, the data was obtained so that the cross-shelf can then be correctly calculated in the controller 12.

Preferably, it is also checked in the fusion device 20 or in the controller 12 whether a located object is located in the overlapping zone 34 of the two radar lobes, and in that case it is further checked whether an object located by one of the two sensors is also located by the other sensor in the next cycle. If this is not the case, an error message will be issued (possibly only after 2 to 3 further cycles), as obviously one of the two sensors will not work properly.

Optionally, the radar system 14 can also be operated so that both sensors perform synchronous measuring cycles and the measured data of the two sensors in the fusion device 20 are checked for consistency and possibly subjected to averaging. This requires a higher data processing capacity, but has the advantage of greater location accuracy and error safety.

Likewise, an operation is conceivable in which the measuring cycles of the two LLR sensors

16, 18 are time offset by half a cycle period, so that a higher temporal resolution is achieved.

Another expedient mode of operation of the radar system 14 will now be explained with reference to FIG. This figure shows in a frequency / time diagram an example of the modulation of the radar signal transmitted by one of the two LRR sensors, for example sensor 16. The period shown in Figure 3 comprises two measuring cycles Cl and C2. In accordance with the principle of operation of an FMCW radar, the frequency is ramped in each measuring cycle, with a rising ramp RIs or R2s and a symmetrically falling ramp RIf or R2f. The radar signal reflected by an object and received again by the sensor is mixed with the signal transmitted by that sensor at the time of reception so as to obtain an intermediate frequency signal whose frequency corresponds to the frequency difference between the transmitted and the received signal. This frequency difference depends on the one hand on the signal propagation time and thus on the distance of the object and on the other hand on the Doppler shift that reflected this

Signal due to the relative speed of the object experiences. If one adds the frequency differences obtained for a given object on the rising ramp RIs and the falling ramp RIf, then the distance-dependent parts will expire due to the opposite equal ramp slope, and a measure of the relative speed will be obtained. On the other hand, if one forms the difference of the Frequency differences, then doubles the Doppler part, and you get a measure of the distance.

In the second measuring cycle C2, a steeper ramp is used. With the same frequency deviation, therefore, in the second cycle, the duration T2 of a ramp is less than the duration T1 of a ramp in the first measuring cycle Cl. For the remainder of the second measurement cycle C2, the sensor can be muted or, as it were, idle without the signal being evaluated. The steeper ramp in the second measurement cycle C2 causes the frequency difference to be more sensitive to changes in distance so that a higher resolution is achieved in the distance measurement. This is particularly advantageous for objects in the vicinity. On the other hand, the steepness of the ramp in the first

Measuring cycle Cl for the long-range, and in particular for the location of two-wheeled be optimized. If the measurement cycles Cl and C2 are repeated periodically, one obtains alternately a frequency modulation, which are optimized for the near and the far range. This modulation scheme is therefore particularly suitable for the radar system described here, in which the LRR sensors for both the

Distance range detection as well as for optimized Nahbereichsortung be used.

At the same time, the steeper ramp R2s can be used to eliminate ambiguities that may otherwise arise when multiple objects are located simultaneously. Of course, a modulation scheme is conceivable in which working with three or more different ramps.

The radar signals of the two LRR sensors 16, 18 can be modulated synchronously or asynchronously according to the same modification scheme or according to different modulation schemes. Optionally, the two sensors can also work in different frequency bands, so that it can be decided upon receipt of a signal by one of the two sensors, whether this signal was sent from the same sensor or from the other sensor. This results in additional possibilities to improve the accuracy and in particular the angular resolution of the radar system. In a particularly advantageous embodiment, the two LRR sensors are controlled so that the measuring cycles Cl of one sensor coincide with the measuring cycles C2 of the other sensor. In this way, a signal optimized for long-range detection is obtained in each measurement cycle, as is a signal optimized for near-field detection. To limit the processing effort, the evaluation of the

In the evaluation of the signal optimized for the far range, the evaluation is limited to the larger distance range.

An exemplary embodiment will now be described with reference to FIGS. 4 to 6, in which the two LRR sensors 16, 18 differ in their directional characteristic.

FIG. 4 shows a radar system with two LRR sensors 42, 44 installed in the vehicle 26 at the same positions and in the same orientation as in FIG. 2, but differing in the extent and range of their radars 46, 48. The radar lobe 48 of the LRR sensor 44 is relatively narrow, while the radar lobe 46 of the LRR sensor 42 sweeps a significantly larger angular range, but has only a smaller range because of the faster decrease of the signal intensity. Also in this embodiment, both LRR sensors 42, 44 can be used together for both remote area monitoring and close range monitoring. Due to the specially adapted directional characteristic, however, the quality of the long-range detection is improved in the sensor 44, and the quality of the near-range detection in the case of the sensor 42.

In Figure 5, the structure of the LRR sensor 44 is shown schematically. This sensor has four adjacently arranged antenna patches 50, to which an identical transmission signal is supplied, the received signals, however, are evaluated separately. The radar beams emitted by the patches are shared by a common

Lens 52 bundled, so that four slightly mutually angularly offset partial lobes 54 arise, which together form the relatively narrow radar lobe 48 in Figure 4. By comparing the amplitudes and phases of the signals received by the antenna patches 50, the azimuth angle of a located object can be determined. In Figure 6, the structure of the LRR sensor 42 is shown in an analogous manner. Here, the lens 52, which in the example shown has the same focal length as in FIG. 5, is arranged at a shorter distance in front of the antenna patches 50, so that weakly focused partial lobes 56 are formed, which together form the radar lobe 46 in FIG. Due to the smaller lens distance is here also the angular offset between the

Part lobes 56 larger, so that the radar lobe 46 is not only fanned further, but due to the greater angular displacement of the partial lobes and a uniformly high angular resolution in the increased detection angle range is made possible.

Alternatively or additionally, the lenses 52 of the sensors shown in FIGS. 5 and 6 may also differ in their geometry.

Likewise, the different directional characteristics of the LRR sensors 42, 44 can also be generated with so-called phased array antennas. However, the embodiment described here has the advantage that the LRR sensors may be identical in their basic structure and only the shape and / or mounting of the lens 52 needs to be modified. This facilitates a rational and cost-effective production of

Radar system.

The embodiment shown in Figure 4 can also be modified so that, for example, the LRR sensor 42 is arranged with the further fanned Radarkeule on the longitudinal center axis of the vehicle 26. In this case, a symmetrical arrangement with two LRR sensors 44 on either side of the sensor 42 is possible, so that the radar system has a total of three LRR sensors.

Claims

claims

A radar system for motor vehicles, comprising a plurality of radar sensors installed in the front of the vehicle (26) for monitoring the apron of the vehicle, characterized in that at least two of the radar sensors are LRR sensors (16, 18, 42, 44).

2.Radarsystem according to claim 1, characterized in that two LRR sensors (16, 18, 42, 44) are arranged in the vicinity of the lateral vehicle boundary on the left and right side of the vehicle (26).

3. Radar system according to claim 1 or 2, characterized in that the LRR sensors

(16, 18; 42, 44) are oriented so that their optical axes (38) diverge.

4.Radarsystem according to any one of the preceding claims, characterized by a fusion device (20) which is adapted to evaluate the signals of the LRR sensors (16, 18) alternately from measuring cycle to measuring cycle.

5. Radar system according to one of the preceding claims, characterized by a

Driver module (24) adapted to activate the LRR sensors (16, 18) alternately.

6.Radarsystem according to one of the preceding claims, characterized in that the LRR sensors (16, 18) are adapted to transmit frequency modulated radar signals, and that the pattern of the frequency modulation differs from sensor to sensor.

7.Radarsystem according to any one of the preceding claims, characterized in that the LRR sensors (16, 18) are adapted to frequency modulated radar signals send, and that a driver module (24) is adapted to the LRR sensors (16, 18) to control so that they each have at least two alternately traversed measuring cycles (Cl, C2), which differ in their frequency modulation.

8. Radar system according to claims 6 and 7, characterized in that the driver module (24) is adapted to the LRR sensors (16, 18) to control so that the same time measuring cycles (Cl, C2) of the sensors differ in their frequency modulation ,

9.Radarsystem according to any one of the preceding claims, characterized in that at least two LRR sensors (42, 44) are present, the differently fanned radar lobes (46, 48) generate.

10. The radar system according to claim 9, characterized in that the LRR sensors (42, 44) differ in the arrangement and / or geometry of their lenses (52).