DE102008054579B4 - Maladjustment detection for a radar sensor - Google Patents

Abstract

Method (300) for detecting a vertical misalignment of a radar sensor (110) for detecting a radar target, comprising the following steps:- emitting a radar signal by means of at least one transmitting element of the radar sensor (110);- receiving radar signals reflected by the radar target by means of a plurality of receiving elements of the radar sensor ( 110);- determining (340) a quality with which the received signals allow detection of the radar target; and- determining (370) a vertical misalignment of the radar sensor on the basis of the quality; characterized by the step (350) of selecting signals on which to base the determination (370) of vertical misalignment based on at least one of the following criteria: high signal-to-noise ratio, signal indicative of a single radar target, Position of a horizontal angle (γ) of the radar target in an angle range of the radar sensor (110), which is unambiguous with regard to an angle determination, signals indicating that different frequency peaks are not superimposed.

Description

State of the art

The invention relates to a technique for detecting a vertical misalignment of a radar sensor.

Known radar systems, such as those used in motor vehicles, use a radar sensor that includes at least one transmitting element and a number of fixed receiving elements such that each of the transmitting elements radiates a radar lobe of predetermined shape and direction (multiple fixed beam), and the receiving elements the incoming Signal received with a known spatial sensitivity distribution. An antenna diagram of the radar sensor can be specified from the sensitivity distributions of the reception elements and a spatial distribution of a transmission power of a transmission element. A measurement involves transmitting a radar signal and then receiving signals reflected from a radar target. In subsequent processing of the received signals, relative sizes of the radar target, such as its distance, speed, direction of movement and/or its (horizontal) directional angle can be determined.

In a Frequency Modulated Continuous Wave (FMCW) system, the at least one transmission element emits a signal of a modulated frequency. The signals received by the receiving elements are analyzed with regard to their frequency spectrum. A peak in the frequency spectrum corresponds to a certain combination of relative distance and relative speed of the radar target. A directional angle of the radar target can be determined based on the complex amplitudes of the reflected signal at the receiving elements.

The radar lobes can be arranged, for example, in the form of a horizontally oriented fan. If the fan of the radar lobes is vertically misaligned, i.e. deflected at an angle up or down with respect to a desired alignment, this has a negative effect on the measurement accuracy of the radar system. This is partly due to the fact that the correct alignment of the radar lobes is usually an implicit or explicit basis for an evaluation of received radar signals, so that in the event of misalignment the processing is based on incorrect assumptions.

Various proposals have been made to detect vertical misalignment of a radar sensor. Known approaches use, for example, the course of a radar backscatter cross section over a specific distance, a distribution of nearby ground targets, or a change in detection rates in the detection area. However, these methods are only reliable to a limited extent and have not yet been able to establish themselves in practice. In addition, these methods depend on the installation height of the radar sensor above the roadway or on the ground conditions, show differences between positive and negative vertical misalignment angles, are based on unreliable model assumptions or can only be evaluated in limited misalignment angle ranges. In addition, the previous methods are based on object properties and are therefore dependent on the signal processing and data fusion chain.

DE 199 37 723 C2 shows a method for determining a vertical misalignment of a radar sensor, an incoming signal being compared with a large number of antenna diagrams that are assigned to different misalignments, and a misalignment of the radar sensor being concluded from this comparison.

DE 102 07 437 A1 shows a radar sensor for a motor vehicle, in which an additional radar lobe is directed onto a roadway in order to be able to determine misalignment.

DE 602 12 468 T2 shows a method and a device for adjusting a mounting arrangement for radar, as well as a radar adjusted by this method or this device.

The object of the invention is to establish a reliable, automatic detection of a vertically misaligned radar sensor.

Disclosure of Invention

The object on which the invention is based is achieved by a method according to claim 1, a computer program product according to claims 6 and 7 and a system according to claim 8. Subclaims specify advantageous configurations of the invention.

According to the invention, a vertical misalignment of the radar sensor is determined on the basis of a quality with which a signal reflected by a radar target matches a sensor profile that indicates an adjusted radar sensor. If the determined quality indicates that the reflected signal only poorly matches the sensor profile, the sensor may be misaligned. Advantageously, this quality determination is only carried out for selected targets whose measured values are highly likely to be meaningful. In this case, signals are selected on which the determination of the vertical misalignment is based, on the basis of at least one of the following Criteria: high signal-to-noise ratio, signal indicating a single radar target, position of a horizontal angle of the radar target in an angular range of the radar sensor that is unambiguous with regard to an angle determination, signals indicating that different frequency peaks do not overlap.

character list

• 1a, 1b: eine schematische Ansicht eines an einem Kraftfahrzeug verwendeten Radarsensors in unterschiedlichen Ansichten;
• 2: eine schematische Ansicht eines Systems zur Erfassung einer vertikalen Dejustage des Radarsensors aus 1a und 1b;
• 3: ein Ablaufdiagramm eines Verfahrens zur Erfassung einer vertikalen Dejustage des Radarsensors aus 1a und 1b zur Ausführung auf dem System von 2;
• 4a, 4b: Sensorprofile des Radarsensors von 1a und 1b; und
• 5b, 5b: bestimmte Dejustageindikatoren in exemplarischen Messszenarien gemäß dem Verfahren von 3.

The invention is described in more detail below with reference to the drawings. Show it:

• 1a , 1b 1: a schematic view of a radar sensor used on a motor vehicle in different views;
• 2 : a schematic view of a system for detecting a vertical misalignment of the radar sensor 1a and 1b ;
• 3 : a flowchart of a method for detecting a vertical misalignment of the radar sensor 1a and 1b to run on the system of 2 ;
• 4a , 4b : Sensor profiles of the radar sensor from 1a and 1b ; and
• 5b , 5b : certain misalignment indicators in exemplary measurement scenarios according to the method of 3 .

1a shows a motor vehicle 100 with a radar sensor 110 on a level route in a side view. The radar sensor 110 emits a number of radar lobes K forward in the direction of travel at a predetermined elevation angle. A vertical misalignment angle α with respect to this elevation angle is shown. 1b shows the motor vehicle 100 in a plan view. Four radar lobes K1 to K4 (corresponding to the lobes K in 1a ) are fanned out in the horizontal direction. According to the invention, more or fewer radar lobes K can also be used; the number of evaluated radar lobes can be less than a number of transmitting and receiving elements comprised by radar sensor 110 . The extent and the overlaps of the radar lobes K1 to K4 in the 1a and 1b are not to scale. A horizontal angle γ of a radar target reflecting the radar signals is determined with respect to a longitudinal axis of radar sensor 110.

2 FIG. 12 shows a schematic overview of a system for detecting a vertical misalignment of radar sensor 110. FIG 1a and 1b . A transmitting device 210 generates radar signals, which are transmitted by means of the radar sensor 110 to the 1a and 1b directions shown are emitted in the radar lobes K1 to K4. A transmitting element and a receiving element (not shown) of radar sensor 110 are assigned to each radar lobe K1 to K4. Signals reflected by a radar target are received by a receiving device 220 using radar sensor 110 .

The signals received by the receiving device 220 are provided to a comparison unit 230 which is connected to a profile memory 240 . A sensor profile of radar sensor 110 is stored in profile memory 240, which describes an antenna diagram with respect to a horizontal angle (γ) for each radar lobe K1-K4. The antenna diagram can relate to amplitude and/or phase relationships of the signals.

The comparison unit 230 carries out a comparison between the received signals and the sensor profile stored in the profile memory 240 . For example, if reflected signals assigned to the four radar lobes K1 to K4 are received from a radar target, the ratio of the signal amplitudes (or signal phases) ideally only fits to a single horizontal angle γ in the sensor profile. Depending on how well the received signal matches the determined horizontal angle γ, the comparison unit 230 also determines a quality G in addition to the horizontal angle γ. It provides both values to a discriminator device 260 . In addition, the discriminator device 260 is provided with values of a signal-to-noise ratio (SNR) of the signals from an SNR determination device 250 which is connected to the receiving device 220 .

For each measurement, the discriminator device 260 has SNR values assigned to the radar lobes K1 to K4, a horizontal angle γ of the radar target and a quality value G of the determination of the horizontal angle γ. In addition, the discriminator device 260 can process further signals (not shown), which indicate, for example, a driving state of the vehicle 100 and/or are determined from the received signals. On the basis of its input variables, the discriminator device 260 selects measurements whose specific quality G is meaningful. A high informative value of the quality G can exist, for example, if the SNR values on which it is based are high, if the individual signals indicate a single radar target, if the determined horizontal angle γ lies in an angle range of the radar sensor that is unambiguous with regard to an angle determination and/or if the received signals indicate that different frequency peaks do not overlap.

The quality values G such as meaningful measurements are stored by the discriminator device 260 in a quality memory 270 written. Optionally, additional values can be written into the quality memory 270, for example a measurement time, measurement circumstances, the determined horizontal angle γ or the SNR values.

A decision device 280 reads the quality values G from the quality memory 270 and processes them such that a single quality value DG is determined from the quality values G collected up to now. For example, the decision device 280 can comprise a low-pass filter and/or a device for forming a moving average, which forms an average value for DG of past qualities G in a predetermined measurement window. Discarded and/or obsolete quality values G can be removed from the quality memory 270 by the decision device 280 (or alternatively, for example, the discriminator device 260). The decision device 280 compares the determined quality value DG with a threshold value that is provided to it by a threshold value specification device 290 . This can be, for example, an input device or a read-only memory. If the specific individual quality value DG is below the predefined threshold value, decision device 280 determines the presence of a misaligned radar sensor 110. This is indicated by the arrow in pointing to the left 2 decision device 280 can output a signal indicating a misalignment, which can be used, for example, to issue a driver warning, to log the misalignment and/or to initiate an adjustment of radar sensor 110 .

3 FIG. 12 shows a flow chart of a method 300 for execution on the system 200 of FIG 2 . The method 300 begins in a step 310 in which a radar signal is emitted by the radar sensor 110 . In a subsequent step 320, signals reflected by a radar target are received by means of radar sensor 110. In a step 330, the horizontal angle γ of the radar target is then determined on the basis of the received signals. In a subsequent step 340, the quality G of the determination of the horizontal angle γ is determined. In the case of multiple radar targets causing reflected signals superimposed on one another, in step 330 all horizontal angles and in step 240 all qualities are determined. Then (in a step that is not shown) the qualities are appropriately weighted or averaged unweighted in order to provide a representative quality G for all radar targets. In any case, a step 350 then checks whether the determination of the quality G is reliable or not. To this end, further values and/or measurement conditions can be used, such as SNR values determined from the received signals.

If the determination of the quality G in step 350 is not considered reliable, then the method 300 returns to step 310 and begins again. Otherwise, the method 300 continues with a step 360 in which an individual quality value DG is determined on the basis of the determined quality G and previously determined qualities G. Subsequently, in a step 370, it is checked whether the individual quality value is above a predetermined threshold value. If this is the case, then in a subsequent step 380 it is determined that there is no misalignment of radar sensor 110 and the method starts again with step 310 . If, on the other hand, it is determined in step 370 that the average quality is not above the threshold value, then in step 390 it is determined that radar sensor 110 is misaligned, before the method also begins again with step 310 .

Steps 390 and 380 can optionally include activating or deactivating warning devices, an entry in an error memory and/or activating or deactivating an actuator which aligns radar sensor 110 in the vertical direction.

4a FIG. 12 shows a schematic diagram of a sensor profile of a radar sensor 110 correctly adjusted in the vertical direction 1a , 1b . The determined horizontal angle γ of a radar target is plotted in the horizontal direction, and received power in dB in the vertical direction. Each of the four curves drawn is one of the radar lobes K1 to K4 in 1b assigned. This representation relates to amplitudes of received signals; in a corresponding manner, the phases of the received signals can also be displayed or evaluated in addition or as an alternative.

The horizontal angle γ of a radar target is determined, for example, by determining the relative signal strengths or phases of the reflected radar signal in the individual lobes K1 to K4 on the basis of in 4a shown sensor profile are correlated with each other. In an illustrative example, the relative signal strengths of the lobes K1 / K2 / K3 / K4 behave like -23dB / - 18dB / -36dB / -36dB, so that a horizontal angle y of approx. +3° can be clearly inferred from this. Due to the good determinability of the horizontal angle γ, a quality value G assigned to this determination would be relatively large.

4b shows a sensor profile accordingly 4a from a radar sensor 110 in vertical Direction is misaligned by an angle of α = -6 °. It can be seen that there are extensive areas of the horizontal angle γ in which the sensitivity curves associated with the lobes K1 to K4 are close to one another, which makes it difficult to reliably determine the horizontal angle γ.

In a continuation of the example above, the radar target at a horizontal angle γ of approx. +3° would result in the relative signal strengths of the lobes K1 / K2 / K3 / K4 being -42 dB / -43 dB / -43 dB / - 43 dB restrained. The differences in the signal strengths could lie within a range of their measurement inaccuracy, so that even a radar target in the range between +3° and +5° or around +12° could lead to a corresponding ratio of signal strengths. The horizontal angle γ of the radar target cannot then be determined reliably or precisely. A quality value G assigned to this determination would accordingly be relatively low.

5a shows a schematic representation of certain qualities G as points and a quality value DG derived from the qualities G as a solid line. 5a corresponds to 4a , ie, the radar sensor 110 is not misaligned in the vertical direction (α=0°). In the horizontal direction is in 5a a number of cycles is plotted, which in a first approximation corresponds to a measurement time. A quality G of the angle determination of the horizontal angle is plotted in the vertical direction. A quality G=1 indicates the highest possible quality. Most of the grades G are in the upper part of the diagram of 5a ; the quality value DG ranges between 0.95 and 0.93. Although individual qualities are determined below 0.7, the average quality remains relatively constant in the specified range.

5b shows a representation accordingly 5a , but corresponds to the prerequisites for the values shown 4b ie, radar sensor 110, on the basis of whose measurements the data shown are determined, is misaligned in the vertical direction by an angle of α=−6°. The grades G shown as points are distributed relatively widely in the vertical direction. Accordingly, the quality value DG ranges between approximately 0.81 and 0.83.

How from the 5a and 5b As can be seen, a correctly aligned radar sensor 110 (α=0°) can be clearly distinguished from a vertically misaligned radar sensor 110 (α=−6°) by selecting a threshold value in the range between 0.85 and 0.9. A smaller misalignment of radar sensor 110 can also be determined by an adapted selection of the threshold value.

Claims (8)

Method (300) for detecting a vertical misalignment of a radar sensor (110) for detecting a radar target, comprising the following steps: - emitting a radar signal by means of at least one transmitting element of the radar sensor (110); - Receiving radar signals reflected from the radar target by means of a plurality of receiving elements of the radar sensor (110); - determining (340) a quality with which the received signals allow detection of the radar target; and - determining (370) a vertical misalignment of the radar sensor on the basis of the quality; characterized by the step (350) of selecting signals on which to base the determination (370) of vertical misalignment based on at least one of the following criteria: high signal-to-noise ratio, signal indicative of a single radar target, Position of a horizontal angle (γ) of the radar target in an angle range of the radar sensor (110), which is unambiguous with regard to an angle determination, signals indicating that different frequency peaks are not superimposed. procedure after claim 1 , characterized by the step of determining the horizontal angle (γ) of the radar target. Method (300) according to claim 2 , characterized in that the step of determining (330) the horizontal angle (γ) comprises the step of correlating amplitudes and/or phases of the received signals on the basis of a sensor profile which has amplitudes dependent on the horizontal angle (γ) and which are assigned to the receiving elements and /or indicates phase sensitivities. Method (300) according to one of the preceding claims, characterized in that the vertical maladjustment is additionally determined on the basis of qualities (G) determined in the past. Method (300) according to the preceding claim, further comprising the steps of determining a summary quality value (DG) on the basis of previously determined qualities (G) and comparing (370) the summary quality value (DG) with a predetermined threshold value. Computer program product with program code means for carrying out the method according to one of the preceding claims when the computer program product runs on a processing unit. Computer program product according to the preceding claim when stored on a computer-readable data carrier. System (200) for detecting a vertical misalignment of a radar sensor (110) for detecting a radar target, comprising: - a radar sensor (110) with at least one transmitting element for transmitting a radar signal and a plurality of receiving elements for receiving radar signals reflected by the radar target; - Quality determination means (230) for determining a quality (G) with which the received signals allow detection of the radar target; and - misalignment determination means (280) for determining a vertical misalignment of the radar sensor (110) on the basis of the quality (G); characterized in that it further comprises selection means (260) for selecting signals which are provided to the misalignment determination means (280), and in that the selection means (260) are set up to select signals on the basis of at least one of the following criteria: high signal Noise ratio, signal indicating an individual radar target, position of the horizontal angle (γ) of the radar target in an angular range of the radar sensor (110) that is unambiguous with regard to an angle determination, signals indicating freedom from superimposition of different frequency peaks.

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