EP2100162A1

EP2100162A1 - Method for operating a radar system with possible concealment of target objects and radar system for carrying out the method

Info

Publication number: EP2100162A1
Application number: EP07821207A
Authority: EP
Inventors: Ruediger Jordan; Oliver Schwindt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-12-05
Filing date: 2007-10-11
Publication date: 2009-09-16
Also published as: US20110063157A1; DE102006057277A1; WO2008068088A1; US8514124B2

Abstract

A method for operating a radar system and a radar system for carrying out the method, in particular a microwave radar system for applications in or on motor vehicles, in which at least one target object (100) and at least one possible concealing object (110) are sensed by radar equipment, there is in particular provision that it is detected (210 - 220) whether a concealment situation of the at least one target object (100) by the at least one concealing object (110) is occurring, and if the concealment situation is detected it is not automatically assumed that the target object (100) has been lost.

Description

description

title

Method for operating a radar system in the event of possible target obstruction occlusion

Radar system for carrying out the method

State of the art

The present invention relates to a method for operating a radar system, in particular a microwave radar system for applications in or on motor vehicles, as well as a radar system for carrying out the method, according to the

Topics of the respective independent claims.

Radar systems using electromagnetic waves, in particular using microwaves with frequencies above some 100 MHz, are widely known and used for the detection of objects and for the determination of

Speeds, distances and directions of these objects.

It is known to use such radar systems in a motor vehicle for detecting the position of preceding vehicles and possibly for lane allocation of these preceding vehicles.

A directional antenna provided with the respective radar system and having a radar sensor measures in a manner known per se reflexes of waves impinging on a (target) object to be sensed. The directional antenna can detect the object only if the direct path between the radar sensor and the target object is not obscured by one or more other objects.

The occlusion of a target object by another object in vehicle traffic, for example. In a strong highway right turn occur where the own vehicle on the trailing or approaching a lane behind a target vehicle with a relatively long interval. Namely, in the case where on the right lane another vehicle, for example a truck, travels, which at least partially blocks the direct view between the radar sensor and the target vehicle and therefore can not be detected.

In the known radar systems, the radar sensor is now arranged approximately in the center of the vehicle, preferably in the middle of the bumper of the vehicle, and the driver therefore sits to the left of the sensor. As a result, it may happen that the driver can still see the target vehicle even though it is already covered by the other vehicle for the radar sensor. In such a scenario, therefore, it often comes to a Zielobjektverlust, which is not understandable because of the still captured by the driver target vehicle for the driver.

An occlusion situation just described also occurs, for example, in traffic jams, where many vehicles are involved and it often happens that potentially relevant target vehicles are briefly covered by other vehicles before they become relevant in the first place.

It is therefore desirable to improve a radar system described at the beginning in such a way that unintelligible or contradictory measurement results are avoided for the driver in said concealment situations.

Disclosure of the invention

The present invention is based on the idea of improving the tracking (so-called "tracking") of a target object by means of a radar system affected here, by detecting whether there is a concealment situation with respect to the target object and, in the case of a detected concealment situation, not automatically of a loss of the target object.

Preferably, such a concealment situation is handled by means of a plausibility check of the existence of such a concealing object, wherein a plausibility value (ie the "plausibility of the object") is then increased or incremented if the radar system preferably in a measuring cycle a respective tracked object, hereinafter referred to as "target object", detected or re-detected after an already occlusion and the plausibility value is then decreased or counted down when the radar system preferably detects no radar reflections of the object in a measurement cycle. If the current plausibility value falls below a lower empirically predeterminable

Threshold, it is assumed that the target object has completely disappeared because no reflexes have been detected at all for a longer period of time. Only in this case, the target object is deleted from the capture and thus not pursued. This procedure therefore does not automatically delete a target object if it has not been detected within a measurement cycle.

According to the invention, a target object which is recognized as possibly hidden is made more slowly de-plausible, since in the case of a possible concealment situation the target object can not be detected, although it is actually still present.

Furthermore, it can be provided to make the respective increments for the mentioned increase or decrease in the plausibility values of a target object dependent on the sensitivity or measurement resolution of the respectively used radar sensor, whereby the reliability of the radar system is significantly increased.

By the invention, a target object is assumed to be longer than existent and in most cases be detected again by the radar sensor after a short time interval. In the meantime, the target object is communicated to the driver as still existing and thus does not lead to the above-described for the driver incomprehensible intermediate result. As a result, the unfounded target object losses described above are avoidable and results in a better understandable for the driver result.

According to the invention, said detection of a concealment situation preferably takes place by evaluating the relative position of the detected objects relative to one another and by marking objects which are possibly concealed by other objects. The resulting information is preferably further processed in the mentioned or an alternative plausibility algorithm in order to slow down or even completely suppress the reduction of the plausibility value for the target object in the case of a detected masking of a target object. - A -

Brief description of the drawings

The invention will be described in more detail below, with reference to the attached drawings, with reference to possible embodiments, from which further features and advantages of the invention result.

In the drawings show

Fig. 1 shows schematically the geometric relationships in the calculation of a

Concealment situation according to a preferred embodiment of the present invention and Fig. 2 shows a preferred embodiment of the method according to the invention with reference to a flow chart.

Embodiments of the invention

1 schematically shows the preferred procedure according to the invention in a purely geometrical calculation of a concealment situation of a target object 100. The assumed position of a radar sensor is referenced 105. Furthermore, an object 110 arranged in the measuring field of the radar sensor 105 is assumed, which obscures the target object 100.

In the obscuring object 110, a rectangular object floor plan of width 2 * B and length L is assumed. The purpose of the occlusion recognition is to determine the angles φ1 to φ4 of all four corners of the object 110 and to determine therefrom the minimum and maximum of these four angles (for the sake of clarity, only the angle φ1 is shown in the figure). More distant objects, which lie between these two angles, in the present case the two angles φ1 and φ3, are affected by occlusion.

The relative angle oc of the object 110 can be estimated by various methods, for example via the own radius R also shown in FIG. Incidentally, the quantities dxO and dyO are the coordinates of the obscuring object 110, as already provided by known algorithms for determining the position of objects (so-called "tracking algorithms").

The calculations to be derived from FIG. 1 are based on the two variables

R and OC. According to FIG. 1, the intrinsic radius R can be calculated from the airspeed v ego and the eigengray rate psidt ego according to the relationship R = v ego / psidt ego. The relative angle oc of the object 110 results according to FIG. 1 from the relationship OC = arcsin (dx0 / R).

By coordinate transformation one obtains the following relations for the angles φl to φ4:

dxl = dxO + cos (oc) * 0 - sin (α) * (- B) dyl = dyO + sin (α) * 0 + cos (α) * (- B) φl = arctane (dyl / dxl)

dx2 = dxO + cos (oc) * 0 - sin (oc) * (+ B) dy2 = dyO + sin (oc) * 0 + cos (oc) * (+ B) φ2 = arctan (dy2 / dx2)

dx3 = dxO + cos (oc) * L - sin (oc) * (+ B) dy3 = dyO + sin (oc) * L + cos (oc) * (+ B) φ3 = arctan (dy3 / dx3)

dx4 = dxO + cos (oc) * L - sin (α) * (- B) dy4 = dyO + sin (oc) * L + cos (α) * (- B) φ4 = arctane (dy4 / dx4)

Finally, as already mentioned, the occlusion angle 'φ_cover' 115 results according to the relationship φ occlusion = [min (φl ... φ4); max (φl ... φ4)]. All objects with an angle in the range of φ occlusion may be affected by occlusion. FIG. 2 describes a preferred procedure according to the invention in the operation of a radar system concerned in the case of an assumed concealment situation.

The procedure shown there, which can be implemented, for example, as a control code of a radar control unit or in the form of a special circuit, for example in a motor vehicle, consists of two subroutines 200 and 205, which run independently and / or in parallel in the present example. However, it is understood that the first subroutine 200 grds. also as part of the second subroutine

205 can be realized, for example. Between the local steps 225 and 230th

The first subroutine 200 loops through a weighting 210 of the relative position of the objects (i, j, k,...) Currently present in the measuring field of the radar system, preferably as described in FIG. Based on the result of this evaluation 210, in the subsequent step 215, those objects j possibly concealed by other objects k are marked as "possibly concealed" and the objects k thus marked are cached 220. This cached concealment-relevant information is present at independent and / or concurrent subroutine 205, as described below.

The second subroutine 205 preferably comprises executed process steps for carrying out the above-mentioned plausibility check method. The process steps 225-255 listed within the dashed line 205 represent the steps of an nth measurement cycle of the underlying radar system and are repeatedly executed by means of the loop shown until the step 260 is executed, which ends the entire subroutine 205.

It should be emphasized that the use of the plausibility method described below is only preferred and the general inventive concept of the present invention grds. can also be used in other methods, such as when calculating an object existence probability P _exist . In the n-th measurement cycle shown here, in a first step 225, a specific target object is measured or tracked by means of a radar sensor having a directional antenna of the radar system. It will be understood that the measurement cycle shown may also be applied in parallel to multiple targets to thereby track multiple targets simultaneously.

In a next processing step 230, it is checked whether the target object has been detected. If this is the case, in step 235 the current plausibility value P for the target object is incremented by an empirically predeterminable value k and jumped back to the beginning 225 of the subroutine 205 to return the (n + 1) th measurement cycle to the present one

To execute target object. However, step 235 is executed only if the condition P <P _max = const. is satisfied.

If the target object could not be detected by the radar sensor according to step 230, step 240 first checks whether the target object is stored as "possibly hidden" 220. If this is the case, in step 245 the plausibility P is changed by a value k / m is counted down or reduced, wherein the value of m is empirically chosen so that this down counting of P is mitigated, ie it applies in any case the condition m> 1.

In the event that the target object is detected as not "possibly obscured" in step 240, the plausibility of the target object is reduced by the full value k in step 250, since the non-detection of the target object is most likely not caused by occlusion In a subsequent step 255 it is still checked whether the new value of P is smaller than an empirically predeterminable one

Minimum value is P _mm . If this condition is not met, the jump back to the beginning 225 of the subroutine 205 back. If the condition 255 is met, however, the target object is deleted 260, since it can now be assumed that the target object has left the measuring range of the radar system and therefore no longer has to be detected.

It should be noted that, alternatively, after step 245, a check may be made according to step 255; This depends in particular on the size of the value of m, since only at larger step sizes the reduction of the plausibility P, ie at relative small values of m, the relationship P <P _mm can in principle also be fulfilled in the path 245.

By means of the above-described procedure, target object losses described in the introduction, which occur especially in multi-lane cornering of at least three consecutive vehicles such as a preceding target vehicle, a subsequent foreign vehicle and an own vehicle following the two vehicles, are effectively prevented.

In the embodiment shown in FIG. 2, the described

Plausibility of a target object by calculating the existence probability Pe _x is the target object. In this case, essentially the two probabilities are processed, namely the probability P (D | HI) with which the target object is measured or detected and the probability P (D | HO), which is a false measurement in the detection.

According to a preferred embodiment, the calculation of the value of the existence probability P _{exist is} based on the following equations:

P _existe * = LR _k / (I + LR _k )

where LR _{k represents} the likelihood ratio measured at a cycle number k.

The value of LR _{k is} calculated in the embodiment from the following equations:

LRk = min [P (D | HI) / P (D | HO) * LR _k-1 ; LR _MAX ],

if a detection of the target object has occurred and

LR _k = min [(I-P (D | HI)) / (1-P (D | HO)) * LR _k-1 ; LR _MAX ],

if no detection of the target object has occurred, where P (D | Hl) denotes said measurement probability, P (D | HO) denotes the erroneous measurement probability, and LR _MAX denotes the maximum value of LR.

In the mentioned algorithm, the consideration of a concealment situation takes place in the following way. With a suspected occlusion, P (D | Hl) is reduced. The exact value of the reduction can be determined in a conventional manner by statistical methods. Depending on the degree of occlusion it will be higher or lower. Since it is also possible to measure with radar sensors under vehicles, the value of the measurement or detection probability P (D | Hl) will not fall to the value '0'.

The said deletion of target objects is preferably also handled via the existence probability P. In this case, however, no further algorithmic measures are required.

Claims

claims

1. A method for operating a radar system, in particular a microwave radar system for applications in or on motor vehicles, in which at least one target object (100) and at least one possible masking object (110) radar-technically detected, characterized in that is detected (210 - 220 ), if one

Concealment situation of the at least one target object (100) by the at least one occlusion object (110) and in the case of a detected occlusion situation (215, 240) in a non-detection (230) of the target object (100) by the radar system does not automatically assume a loss of the target object becomes (245).

2. The method according to claim 1, characterized in that said concealment situation is determined by plausibility (235, 245, 250) of the existence of the obscurity object (110), wherein a plausibility value is increased when the radar system detects the target object or after an already has been detected again and the plausibility value is lowered if the radar system does not detect the target object.

3. The method according to claim 2, characterized in that only in the case that the current plausibility value falls below a lower empirically predeterminable threshold value, it is assumed that the target object has left the measuring range of the radar system and in this case the target object from the amount of the Radar system detected target objects is deleted.

4. The method of claim 2 or 3, characterized in that an unrecognized and detected as possible hidden target object is slower deplausibilisiert, as an unrecognized and not as a possible way hidden detected target object.

5. The method according to any one of claims 2 to 4, characterized in that the respective increments for said increase or decrease of the plausibility value of the target object are made dependent on the measurement resolution and / or sensitivity of the radar system.

6. The method according to any one of the preceding claims, characterized in that said detection of a concealment situation of the at least one target object by the at least one occluding object by evaluating the relative position to each other.

7. The method according to claim 6, characterized in that the possible masking object is assumed to be rectangular or square (110) and a masking situation is calculated by the angle of the four corners of the possible masking object relative to the position of a radar sensor (105) of the radar system and from the four angles, the minimum and maximum angles are calculated, where more distant objects lying between the calculated minimum and maximum angles are presumed to be affected by occlusion.

8. The method according to any one of claims 2 to 7, characterized in that the

Plausibilisierung based on a _{probability of} existence P _{exist is} performed.

9. radar system for carrying out the method according to any one of the preceding claims, characterized in that the radar system first means (210 - 220) for detecting a possible concealment situation of the at least one target object

(100) by the at least one masking object (110), wherein in the case of a detected occlusion situation in a non-detection of the target object (100) by the radar system is not automatically assumed a loss of the target object (100).

A radar system according to claim 9, characterized in that said first means (210-220) cooperate with at least second means (235, 245, 250) for plausibility checking the existence of the obscuration object (110), a plausibility value then being increased if the radar system the target object is detected or re-detected after a previous occlusion and wherein the plausibility value is lowered if the radar system does not detect the target object.

11. Radar system according to claim 10, characterized in that by means of the at least second means (235, 245, 250) an unrecognized and possibly concealed detected target object is slower deplausibilisiert, as an unrecognized and not as possible concealed detected target object.