WO2007015288A1

WO2007015288A1 - Misalignment estimation method, and misalignment estimation device

Info

Publication number: WO2007015288A1
Application number: PCT/JP2005/014026
Authority: WO
Inventors: Toshio Wakayama; Takayuki Inaba; Takashi Sekiguchi; Masashi Mitsumoto
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2005-08-01
Filing date: 2005-08-01
Publication date: 2007-02-08
Also published as: JPWO2007015288A1

Abstract

A radar is precisely estimated in its misalignment. Provided is a misalignment estimation device for estimating the misalignment of the radar to detect a target in front of a running vehicle. The misalignment estimation device comprises a stationary object extraction unit (21) for selecting the echo of a stationary object from the echo of a transmission wave on the basis of a distance and a velocity, and an observation area division unit (221) for dividing the coverage of the radar into a plurality of areas. Further comprised is a reference straight line calculation unit (222) for determining a reference straight line parallel to the running orbit of the vehicle, by linearly approximating the distribution of such a reflection point of the echo of the stationary object selected by the stationary object extraction unit (21) as belongs to the partial area divided by the observation area division unit (222), thereby to determine the misalignment of the radar on the basis of that reference straight line.

Description

Specification

Axis deviation amount estimation method and axis deviation amount estimation device

Technical field

TECHNICAL FIELD [0001] The present invention relates to an apparatus for detecting a target using a radar, and more particularly to a technique for increasing the detection accuracy of a target by calculating an axis deviation amount of the radar.

Background art

[0002] The power of conventional radar systems that have been widely applied in the fields of military / defense, weather, etc. In these fields, mass production costs and installation costs did not become much of a problem. Recently, however, attempts have been made to increase the safety of automobile operation by installing a radar device in an automobile, detecting obstacles while the automobile is running. For automobile-mounted radars, it is required to mount a low-priced radar that can be manufactured at low cost, with less effort, with high man-hours.

[0003] A particular problem here is the simplification and high accuracy of the radar axis adjustment work. The radar mounted on a car is required to detect the distance and speed of a target distant from about 200 meters with a resolution of about lm. However, the radar axis is shifted by only 0.5 degrees from the original forward direction. Even just, the detection error is 200 meters X tanO. 5 ° = 1.7 meters, which means that the required resolution cannot be achieved.

[0004] Further, even if the radar apparatus can be installed with high accuracy before shipment from the factory, the installation of the radar apparatus may go wrong through the use of the automobile. For example, it is almost impossible to prevent radar axis errors caused by long-term vibrations caused by running on rough roads and deformations of the car body due to minor accidents. Therefore, it is necessary to incorporate a process for automatically detecting and correcting the axis deviation while using the radar device.

[0005] Conventionally, as this kind of axis deviation estimation method, it is assumed that the vehicle on which the radar is mounted is running on a straight road, and the signboard or guardrail that exists on the roadside in the echo detected by the radar. There is a known method that estimates the radar axis deviation based on the direction of the straight line, by approximating the echoes distributed parallel to the road in a straight line. (For example, Patent Document 1 and Non-Patent Document 1). [0006] Patent Document 1: Japanese Patent Laid-Open No. 7-120555

[0007] Non-specialized document 1: W. Kederer, J. Detlefsen, Sensor-based determination of angular misali gnment and lane configuration of a radar sensor for ACC—applications, Proceedings of 30th European Microwave Conference, pp.313-31b, 2000.

Disclosure of the invention

Problems to be solved by the invention

[0008] The above-described conventional technology can estimate the radar axis deviation well when many stationary object echoes are distributed on a single straight line and the approximation accuracy of the straight line is high. It is well known that there are various shapes of obstacles observed on real roads, so that the echo distribution cannot be approximated by such a single straight line. Under such circumstances, it is difficult to estimate the radar axis deviation accurately even if the spatial distribution of a stationary object is approximated by a single straight line.

[0009] The present invention has been made to solve the above-described problems, and has an object to make it possible to accurately estimate the amount of misalignment of the radar axis and to improve the measurement performance of the radar. To do.

Means for solving the problem

[0010] In order to solve the problem, a method of estimating the amount of axis deviation according to the present invention,

An axis misalignment estimation method for determining an axis misalignment amount of a radar that detects a target in front of a traveling vehicle,

An echo selection step of selecting a stationary object echo whose reflection point belongs to a predetermined partial region of the radar coverage from the echo of the transmission wave of the radar;

A reference straight line calculating step for calculating a reference straight line parallel to the traveling track of the vehicle by approximating the distribution of reflection points of the stationary object echo selected in the echo selection step with a straight line;

In the reference straight line calculating step, an axial deviation amount estimating step for obtaining an axial deviation amount of the radar based on the direction of the reference straight line calculated in the step;

It is supposed to have. The invention's effect

As described above, in the method of estimating the amount of axial deviation according to the present invention, the linear deviation approximation is not performed on the echoes of the stationary object existing in the entire radar coverage, and is present in a part of the coverage. Since the linear approximation is performed only for the echo of the stationary object, the approximation accuracy of the straight line is increased by rejecting the stationary object echo that degrades the approximation accuracy, and the radar axis deviation is calculated accurately. It becomes possible.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of an observation region according to the first embodiment of the present invention.

FIG. 5 is a flowchart of an axial deviation amount estimation process according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the operation principle of the first embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of the second embodiment of the present invention.

Explanation of symbols

[0013] 4 echo detector,

5 Position detector,

6 Speed detector,

7 Axis deviation estimation part,

8 Position correction section,

21 Stationary object extraction unit,

22 Straight line approximation,

24 orbital curvature acquisition unit,

25 Reference straight line storage section,

26 Orbital curvature storage unit,

221 Observation area division,

222 Reference straight line calculator. BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Embodiment 1.

The radar apparatus according to Embodiment 1 of the present invention is assumed to be mounted on, for example, an automobile, radiates a radar transmission wave in the traveling direction of the automobile (a direction perpendicular to the axle), and targets (many of which are It is an obstacle in driving). Here, the radar apparatus according to the first embodiment of the present invention has a function of correcting a deviation between the reference azimuth in detecting the position of the target and the front direction of the automobile, that is, a radar axis deviation. Yes.

[0015] First, the principle of the method for correcting the axis deviation angle of the radar used in Embodiment 1 of the present invention will be roughly described as follows. In other words, there are many objects on the road that have a plane parallel to the running track of the car, such as guardrails, sidewalks, and median strips. Therefore, the reflection points on the object parallel to the vehicle's running trajectory are extracted, and the reflection points of the radar wave (echo reflection points) are extracted, and a straight line is approximated to the distribution of these reflection points.

[0016] Assuming that the straight line thus obtained is parallel to the traveling track of the vehicle, the difference between the traveling track of the vehicle and the reference direction of the radar itself is obtained. In this way, even if a deviation (unknown amount) occurs in the reference direction of the radar (the direction of the radar axis), the amount of deviation is calculated appropriately. By calculating the position and azimuth of the reflector in consideration of the amount of axis deviation, the accuracy of the position, azimuth and speed of the reflector will be improved.

As shown in the figure, this radar apparatus radiates a radar wave from the antenna 1 in the direction of travel of the automobile and receives a radar wave reflected by a radar wave reflector such as a target or an obstacle. . The transmission / reception unit 2 supplies a transmission signal 11 that is a source of radar waves radiated from the antenna 1 to the outside. At the same time, when the antenna 1 receives the radar wave reflected by the radar wave reflector, the transmitting / receiving unit 2 converts the received signal 12 in the RF (Radio Frequency) band output by the antenna 1 into an internal signal of an intermediate frequency. Down-converted to a received signal in the video band using the difference signal. Down-conversion is realized by outputting the frequency difference between the received signal 12 and the transmission / reception unit 2 and the reference signal which is an internal signal. Hereinafter, the received signal in the video band is referred to as a difference signal. As a result, the transceiver 2 Outputs the difference signal 13. The difference signal 13 is input to the signal processing unit 3 and used for detecting the position of the object.

[0018] The echo detector 4 detects the reflected wave using the difference signal 13, and outputs the frequency 14 of the detected difference signal of the reflected echo. As a general method for detecting such reflected echoes, a method is generally used in which there is a reflected wave when the power is larger than unwanted wave components such as receiver noise and clutter. For that purpose, a certain margin is added to the receiver noise or the power of the clutter, and the signal component having the power exceeding it is regarded as a reflected echo and detected.

The position detection unit 5 obtains a reflection point (echo) position 15 for each predetermined period using the frequency 14 of the difference signal output from the echo detection unit 4. For this purpose, first, the relative distance between the reflection point and the radar device and the direction (angle) of the reflection point are obtained, and the position of the reflector is determined from the obtained relative distance and direction.

[0020] As a method of measuring the distance, a pulse radar method in which a transmission wave is pulse-modulated and distance measurement is performed by a transmission / reception time difference, a frequency-modulated continuous wave is transmitted, and a transmission signal and a reception signal are mixed. The FMCW (Frequency Modulation Continuous Wave) method or multi-frequency CW method, which obtains the distance from the frequency of the difference signal obtained by this, is known. In addition, as a method for obtaining the direction, a method in which an antenna with a pencil beam is mechanically driven and observed, a plurality of element antennas are arranged, and phase control is performed on each element at the time of transmission or reception. In addition, a method of performing beam scanning is known. If these known methods are used, those skilled in the art can easily configure the position detector 5.

In the following description, it is assumed that the position detection unit 5 expresses and outputs the position 15 of the reflection point in a Cartesian coordinate system composed of an X coordinate and a y coordinate. Here, the y-axis, which is the coordinate axis of the y-coordinate, is set with the forward direction of the radar axis as the positive direction and the opposite direction as the negative direction. Also, the X axis and the y axis, which are the coordinate axes of the X coordinate, are assumed to be orthogonal to each other, and the X axis is set forward with the radar axis in the forward direction and the right direction as the positive direction and the left direction as the negative direction. To do.

On the other hand, the speed detector 6 calculates the relative speed of the reflection point using the frequency 14 of the difference signal. The relative velocity of the reflection point is calculated using Doppler modulation of the received wave frequency. Widely known. When the position detection unit 5 uses the FMCW method or multi-frequency CW method, the distance and speed can be calculated simultaneously, so the position detection unit 5 and the speed detection unit 6 are composed of the same parts and elements. Even so,

[0023] Axis deviation amount estimation unit 7 extracts and extracts reflection points that are estimated to be distributed on a straight line parallel to the traveling track of the automobile from the reflection points detected by echo detection unit 4. The amount of axis deviation is calculated based on the distribution of reflected points. FIG. 2 is a block diagram showing a detailed configuration of the axis deviation amount estimation unit 7. In the figure, when the axial deviation amount estimation unit 7 obtains the reflection point position 15 and the reflection point relative speed 16 from the outside, the reflection point position 15 and the reflection point relative speed 16 are input to the stationary object extraction unit 21. To do.

[0024] The stationary object extraction unit 21 selects an echo of the reflection point on the stationary object (hereinafter referred to as a stationary object echo) based on the position 15 or the relative velocity 16 of the reflection point, and outputs it as a stationary object echo 31. To do. Note that the contents of the stationary object echo 31 include at least the position of the reflection point on the stationary object (Cartesian coordinates, or coordinates obtained by converting Cartesian coordinates to a polar coordinate system, etc., equivalent to Cartesian coordinates, etc.). It is. As a method of determining whether the reflection point to which the stationary object extraction unit 21 is input is a reflection point on the stationary object, for example, there are several methods as shown in the following method 1 to method 3. .

[Method 1] This is a method for discriminating whether or not the reflection point is a reflection point on a stationary object based on the relative velocity of the reflection point. As a method of using the relative speed of the reflection point, first, the vehicle speed data is acquired from the outside and collated with the relative speed of the reflection point to identify whether the reflection point is a reflection point on a stationary object (method) 1 1) can be considered. More specifically, for example, vehicle speed data is obtained by a vehicle speed sensor attached to the host vehicle, and a reflector having a Doppler speed that is approximately the same size as the vehicle speed and approaching the vehicle is regarded as a stationary object.

[0026] Similarly, as a method of using the relative speed of the reflection point, whether or not the reflection point is a reflection point on a stationary object is obtained from only the relative speed of the reflection point without taking in information or signals such as vehicle speed from the outside. There is also a method of discrimination (Method 1 2). This method is based on the fact that there are many stationary objects in the radar observation area and the relative velocities are almost the same for multiple stationary object echoes. In other words, this is a method in which a plurality of reflection points are classified with respect to relative velocities, and reflection points where the distribution of relative velocities is concentrated are regarded as stationary object echoes. [0027] (Method 2) This is a method in which an object (reflection point) existing at a position off the lane is regarded as a stationary object. To determine whether a reflection point is out of lane force, a predetermined reference (reference X coordinate) is set for the X coordinate, and the difference between the X coordinate of each reflection point and the reference X coordinate is greater than a certain value. If this happens, consider that this reflection point is out of the lane.

[0028] In this case, the reference X coordinate is calculated by statistically processing the X coordinate of the reflection point obtained so far. For example, the average of the X coordinates of a plurality of reflection points input immediately before is obtained, and this average value is used as the reference X coordinate. Furthermore, it goes without saying that the reference X coordinate can be determined based on the radar axis deviation amount finally obtained by the radar apparatus of the first embodiment of the present invention.

[0029] According to Method 2, since it is possible to determine whether the reflection point is a point on a stationary object only by the X coordinate of the reflection point, the reflection point of the reflection point is determined with respect to the axis deviation estimation unit 7. No need to enter speed 16. Therefore, if it is sufficient to obtain only the purpose of obtaining the radar axis misalignment amount or correcting the axis misalignment amount to improve the reflection point position calculation accuracy, the speed detector 6 can be connected to the radar device. It may be omitted from the component.

[0030] In Method 1 1, since it is necessary to acquire signals and information from an external speed sensor, the radar device and the speed sensor of the mobile platform (vehicle, etc.) are connected so that the speed data can be transmitted. There is a need to. However, it is possible to identify each reflection point independently for each reflection point whether or not each reflection point is a stationary object echo.

[0031] On the other hand, both method 1 2 and method 2 do not require information from an external velocity sensor, and in method 2, it is necessary to calculate the velocity of the reflection point. And However, it is necessary to have a configuration in which the positional information of a plurality of reflection points can be accessed simultaneously. That is, it is necessary to store position information of a plurality of reflection points in a storage device (not shown).

[0032] Since these methods do not contradict each other in principle, there is no problem in using them in combination. For example, as in method 2, the stationary object echo may be narrowed down based on the X coordinate, and the stationary object echo may be narrowed down again using method 11 or method 12.

[0033] On the basis of the stationary object echo 31 calculated in this way, the linear approximation unit 22 Find a straight line approximating the distribution of the coordinates. The approximate straight line slope and intercept are output as line 32. If a straight line approximating the distribution of stationary object echoes is expressed as in equation (1), the slope is given by P, and the intercept (X intercept: the X coordinate of the intersection of the straight line and the X axis) is given by q.

[Number 1]

Hereinafter, a method in which the straight line approximation unit 22 approximates a straight line to the distribution of the stationary object echo will be described in detail. FIG. 3 is a detailed block diagram of the straight line approximation unit 22. The stationary object echo 31 in the figure is input to the observation area dividing unit 221. In the observation area dividing unit 221, observation areas divided based on a predetermined boundary line are set in advance, and an observation area to which a stationary object echo used for linear approximation belongs is determined. .

FIG. 4 is a diagram showing the state of such an observation area (covering area of the radar device). This figure shows an example in which the boundary line is set so as to be parallel to the traveling track of the vehicle 41, and the left side of the boundary line is region A and the right side of the boundary line is region B in the direction of travel. is there. The X in the figure (the symbol “X”) indicates the position of the stationary object echo. Area A stationary objects are distributed almost along the guardrail 42. In addition, stationary object echoes in region B are distributed almost along the central separation zone 43.

[0036] The expression "the boundary line is parallel to the traveling track of the car 41" used here means that the angle between the traveling track and the boundary line is "a child that is almost 0 °". It does not require that the running trajectory and the boundary line do not intersect, that is, the running trajectory and the boundary line may exist on the same straight line, or may have an intersection.

[0037] The observation area dividing unit 221 selects only the stationary object echo in one of the observation areas of the area A and the area B, and selects the stationary object echo 32 in the observation area (hereinafter simply referred to as the stationary object echo 32). ) And output the stationary object echo of the other observation area that has not been selected. For example, only the stationary object echo in region A is selected and output as stationary object echo 32, and the stationary object echo in region B is rejected. It goes without saying that certain! / May select the stationary object echo in region B, output it as stationary object echo 32, and reject the stationary object echo in region A. [0038] As with the stationary object echo 31, the data of the stationary object echo 32 includes the coordinates of the position of the reflection point (Cartesian coordinates or coordinates obtained by converting the Cartesian coordinates to a polar coordinate system or the like, which is equivalent to the Cartesian coordinates). For example).

[0039] By doing so, it is possible to obtain a straight line that approximates the distribution of stationary object echoes belonging to only one of the regions A and B. In general, on roads and vehicle tracks, stationary objects are distributed on both sides of the vehicle track. If the stationary object echo is extracted in such a situation, the stationary object echo is scattered in the right and left direction in the direction of travel. That is, a straight line that simultaneously approximates both the stationary object echo on the guardrail 42 and the stationary object echo on the central separation band 43 must be obtained.

As a result, the straight line obtained as the approximate straight line is greatly deviated from the track of the vehicle, and cannot be used as a reference for obtaining the amount of axial deviation of the radar. To solve this problem, segmentation in advance using the observation region segmentation unit 221 and linear approximation using only stationary object echoes belonging to a given region will greatly improve the accuracy of linear approximation. Become.

[0041] It should be noted that to determine whether the stationary object echo belongs to region A or region B, it is sufficient to compare the X coordinate of the stationary object echo with the X coordinate of the boundary line. In addition, it is desirable that the boundary line be set parallel to the traveling track (traveling direction) of the automobile 41. However, in the case of the example shown in FIG. 4, it is sufficient to reject the V or deviation between the stationary object echo on the guardrail 42 and the stationary object echo on the central separator 43. Therefore, the boundary line only needs to be a straight line that forms approximately 0 ° with the traveling direction of the car. In addition, normally, a certain degree of direction adjustment should have been performed when the radar device is attached to the moving platform (vehicle), and even if the direction accuracy of the boundary line before correcting the axis deviation functions sufficiently. . Therefore, the precision of the setting of the boundary line is not so required.

[0042] In addition to dividing the observation area into the left and right in the direction of travel, the average value X of the X coordinate X (1 = 1, ..., N, N is a natural number) of the stationary object echo is calculated. Or as the X coordinate of the border

ave ave

Yes. The absolute value of the difference between the X coordinate X of the boundary line and the X coordinate X of the stationary object echo | x— X

The stationary object echo may be selected by calculating ave jj ave I and extracting only stationary objects whose absolute value is smaller than a preset value. In this case, the observation area is divided by the set value to be compared with the absolute value of the difference and the X coordinate of the boundary line. [0043] In addition to the roadside, there is a possibility that a reflective object such as a traffic sign may exist on the upper part of the road in front of the traveling direction. In order to extract only roadside data, the X coordinate of a stationary object may be limited and extracted. On the other hand, for example, a wall surface located in parallel with the vehicle trajectory exists above the road in the tunnel, so the observation area may be divided so as to select a stationary object echo on the upper wall surface.

Next, the stationary object echo 32 is input to the reference line calculation unit 222 in FIG. 3, and the reference line calculation unit 222 obtains a straight line that approximates the distribution of the stationary object echo 32. FIG. 5 is a flowchart of the process of the reference straight line calculation unit 222. The reference straight line calculation unit 222 is synchronized with the timing at which the echo detection unit 4 outputs the frequency 14 of the difference signal or the timing at which the position detection unit 5 outputs the reflection point echo every predetermined cycle. The indicated process is executed, and the amount of axis deviation is calculated individually for each timing.

In step ST 101 in FIG. 5, first, the number of repetitions is set to zero. The number of repetitions is a counter for measuring the number of straight line approximations. Thereafter, the reference straight line calculation unit 222 approximates the straight line (step ST102). Assume that there are N stationary object echoes 32 (N is a natural number), and the position of the i-th stationary object echo among these N stationary object echoes is (x, y) (i = l, ... Ν). On the other hand, the approximate straight line is given by equation (1). Here, the slope ρ and the X-intercept q are calculated by equations (2) and (3) by the least square method.

[Equation 2]

”Ν Λ 'ν

[Equation 3] NNNN

-Σ Σ + Σ Σ

N

[0046] After obtaining the slope p and the x-intercept q, the reference straight line calculation unit 222 evaluates the approximation accuracy of the straight line obtained as the approximate straight line, and if the approximation accuracy is inferior to that determined in advance, Some of the stationary object echoes are rejected, and the process moves to the process of obtaining an approximate line again. Specifically, first, the distance between the stationary object echo and the approximate line is calculated (step ST103). The distance d between the stationary object echo, y) and the straight line _x = _Py + q is calculated by equation (4).

Drawing-(py _t + q)

α _Ί =, —— _,,

[0047] Next, stationary object echoes for which d calculated through equation (4) is greater than or equal to a predetermined value are rejected from the set of stationary object echoes 32 (step ST104). By doing so, it becomes possible to efficiently remove the stationary object echo that is a factor that degrades the accuracy of the linear approximation, and the stationary object echo force to be approximated.

FIG. 6 is a diagram for explaining that the approximation accuracy of the straight line, and thus the estimation accuracy of the axis deviation is improved by step ST104. In the figure, a set 51 of stationary object echoes exists along the straight line 52 at the left front of the automobile 41. A set 53 of stationary object echoes exists along a straight line 54 different from the straight line 52. If an attempt is made to approximate the stationary object echo sets 51 and 53 with the same straight line at step ST102, an approximate straight line such as a straight line 55 is obtained.

[0049] Therefore, when the distance between the straight line 55 and each stationary object echo belonging to the stationary object echo sets 51 and 53 is calculated in step ST103, and the stationary object echo belonging to the stationary object echo set 53 is rejected in step ST104, Therefore, it can be expected to approximate a straight line close to the original straight line 52 along which the set 51 of stationary object echoes. [0050] As a result, if the axis deviation amount is calculated based on the straight line 55, the straight line 52 is used as the reference straight line for calculating the axis deviation amount at the angle 56, and the axis is calculated based on the reference straight line. Since the shift amount can be obtained, the angle 57 is obtained, and it can be seen that the estimated accuracy of the axis deviation is improved.

[0051] Here, when the number of rejected stationary object echoes is 0, or when the number of stationary object echoes remaining in the set of stationary object echoes 32 falls below a predetermined number (step ST105: Y S) uses the estimated axis deviation as a missing value (step ST106). Conversely, if any stationary object echo is rejected in step ST104 and still remains in the set of stationary object echoes 32 and the number of stationary object echoes is greater than or equal to a predetermined number (step ST105: No) again finds a straight line that approximates the distribution of the remaining stationary object echoes (step ST107). The calculation performed here is the same as in step ST103.

[0052] Then, add 1 to the number of repetitions (step ST108), and calculate the distance between the stationary object echo and the straight line

Calculate in (4) (step ST110). After calculating the distance, the reference straight line calculation unit 222 further calculates the average of the calculated distances and tests whether the average value exceeds a predetermined value (step ST110). With such a test, it is possible to evaluate whether the force has reached a sufficient level of approximation accuracy of the straight line.

[0053] Here, if the average value exceeds the predetermined value (step ST110: Yes), it is determined that the approximation accuracy is not yet sufficient, so the approximation process is performed again. However, if the number of repetitions exceeds the predetermined value, no further approximation processing is performed, and the estimated axis deviation with respect to the stationary object echo 32 is set as a missing value (step ST106). When the radar device is mounted on an automobile, the response performance will be degraded if it takes too long to calculate the axis misalignment estimation. Then, when the radar device is applied to a collision avoidance / prevention system, it may cause a serious obstacle to safety during driving. Therefore, the response performance is prevented from deteriorating by controlling so that the number of linear approximation processes does not exceed a predetermined number.

[0054] On the other hand, when the number of repetitions exceeds a predetermined number, the straight line approximation process is performed again. For this purpose, first, a stationary object echo rejection process is performed based on the distance between the stationary object echo and the straight line calculated in step ST109 (step ST104). Thereafter, step ST105 to step S Repeat the linear approximation process of Tl 11.

As described above, the radar apparatus according to Embodiment 1 of the present invention determines whether or not the obtained straight line follows the distribution of each stationary object echo by simply obtaining a straight line that approximates the distribution of the stationary object echo. evaluate. In other words, the degree of coincidence and convergence of the stationary object echo distribution with respect to the approximate line is evaluated. If it is determined that the distribution of stationary object echoes is not sufficiently approximated, the stationary object echo distribution is again approximated after rejecting the stationary object echoes that cause the approximate accuracy degradation. Find a straight line. As a result, the accuracy is greatly improved compared to the estimation of the amount of axis deviation by simple linear approximation.

[0056] On the other hand, in step ST110, if the average value does not exceed the predetermined value! /, (Step ST11 0: No), it is already determined that the approximation accuracy of the straight line is sufficiently high. The approximate straight line is output as the axis deviation amount 17 (step ST111), and the process is terminated.

[0057] When outputting the axis deviation amount 17, the reference straight line calculation unit 222 may output the obtained inclination of the reference line and the X intercept as the axis deviation amount 17 as they are, or in accordance with the requirements of the system. You may make it convert into the amount 17 of axis deviations of the expression form. For example, if an angle expression (radian value, etc.) is appropriate as the amount of axis deviation, the angle ex between the straight line 32 and the radar axis is calculated as the axis deviation amount 17 of the radar axis according to Equation (5).

[Equation 5] a = tan ^-1 p ₍₅₎

[0058] Finally, the position correction unit 8 corrects the position 15 of the reflection point output from the position detection unit 5 by using the axis deviation amount 17 and outputs the corrected position 18 to the outside of the radar apparatus. .

Thus, according to the radar apparatus of Embodiment 1 of the present invention, the force for obtaining a straight line that approximates the distribution of reflection points in order to estimate the radar axis deviation amount. Since the observation area is divided based on the boundary line and only the reflection points included in some of the observation areas are used, the factor that degrades the accuracy of the linear approximation is removed, and the accuracy of the linear approximation is improved. Greatly improved.

[0060] Further, by removing the reflection point having a linear force distance in the linear approximation, the factor that further deteriorates the accuracy of the linear approximation is removed, and the accuracy of the linear approximation is greatly improved. [0061] Embodiment 2.

The radar apparatus according to the first embodiment obtains a straight line that approximates the distribution of stationary object echoes on the assumption that the vehicle, which is a mobile platform, moves linearly and the trajectory is also a straight line. It was to estimate the axis deviation of the radar using the tilt

[0062] However, when the radar device is mounted on an automobile, the proportion of the dredging time when the steering angle is not 0 can be ignored. In addition, the track (road) of a vehicle is not always a straight line. In such a case, simply finding a straight line approximating the distribution of stationary object echoes will not give you a correct result! / ヽ!

[0063] Furthermore, the radar apparatus according to the first embodiment may cause the loss of the axis deviation amount when the desired approximation accuracy cannot be obtained or when the number of approximation processes exceeds a predetermined number. However, the handling method for the deficit in the amount of misalignment has been clarified.

[0064] Therefore, in Embodiment 2 of the present invention, in the process of estimating the amount of axial deviation of the radar apparatus of Embodiment 1, a step of smoothing the amount of axial deviation is further provided, whereby the variation in the track shape of the vehicle is performed. It is explained that a method for estimating the amount of misalignment can be obtained that can cope with fluctuations in the steering angle of the vehicle and the lack of the amount of misalignment.

The radar apparatus according to the second embodiment of the present invention is an improvement of the off-axis amount estimation unit 7 of the radar apparatus according to the first embodiment. Therefore, unless otherwise specified, the configuration of the radar apparatus according to the second embodiment is the same as that of the radar apparatus according to the first embodiment.

FIG. 7 is a block diagram showing the configuration of the straight line approximation unit 22 that is a characteristic part of the radar apparatus according to Embodiment 2 of the present invention. In the figure,

The track curvature acquisition unit 24 is a part that acquires the curvature 34 of the track at the position where the vehicle is currently traveling. As a specific method for obtaining the curvature 34, for example, a measurement value of a directional sensor that obtains the angular velocity of a running vehicle may be used, or the steering angle information from the vehicle steering device is used as the curvature. You may make it convert.

In addition, the reference straight line storage unit 25 is a part that stores the amount of axis deviation 35 obtained for each observation period having a predetermined length for a plurality of periods. The track curvature storage unit 26 is the timing at which the reference straight line is calculated, and the track curvature of the vehicle acquired by the reference straight line calculation unit 222 from the track curvature acquisition unit 24. This is the part that stores the rate.

In the following description, a time zone in which one axis deviation amount 33 is calculated is referred to as a section, and each section is identified by a number such as section 1, section 2,. Sections with consecutive numbers assigned to sections shall be adjacent to each other. Also, in a certain section N (N is a natural number), the obtained axis deviation 33 is expressed as axis deviation 33 (N), and the curvature 34 is expressed as curvature 34 (N).

Next, the processing of the reference straight line calculation unit 222 will be described. The reference straight line calculation unit 222 acquires the curvature 34 (N) from the trajectory curvature acquisition unit 24. Further, the reference straight line calculation unit 222 acquires the curvature 36 from the orbital curvature storage unit 26. This curvature 36 is the curvature 34 (k) (k k N) that the reference straight line calculation unit 222 has previously acquired the orbital curvature acquisition unit 24 force. Thereafter, the reference straight line calculation unit 222 stores the curvature 34 (N) in the orbital curvature storage unit 26. As a result, the curvature stored in the orbital curvature storage unit 26 is replaced from the curvature 36 to the curvature 34 (N), and the curvature 34 (N) is used as the curvature 36 in the next processing.

Next, the reference straight line calculation unit 222 examines whether the curvature 36 (curvature 34 (k), k <N) and the curvature 34 (N) are both curvatures equal to or less than a predetermined value. As a result, when either the curvature 36 or the curvature 34 (N) exceeds a predetermined value, the reference straight line calculation unit 222 replaces the process of calculating the reference straight line from the current stationary object echo 32, and the reference straight line storage unit 25 Uses the reference straight line 35 stored by. For example, if the reference line storage unit 25 has stored the reference lines of the last few times, the average value of these reference lines (the average value of the slope and the average value of the X-intercept) is used to calculate the current reference line. calculate.

[0072] Further, when both the curvature 36 and the curvature 34 (N) are less than or equal to a predetermined value, it is determined that the vehicle is in a straight traveling state. Then, as in the first embodiment, a reference straight line is obtained and the estimated axis deviation is calculated. When the estimated axis deviation is correctly calculated, the reference straight line is stored in the reference straight line storage unit 25, and the calculated axis deviation is output.

[0073] In addition, as a result of calculating the amount of axial deviation by the method of Embodiment 1, if the estimated amount of axial deviation is a loss value, either curvature 36 or curvature 34 (N) has a predetermined value. As in the case of exceeding, the current reference line is calculated using the reference line 35 stored in the reference line storage unit 25. As described above, according to the radar apparatus of the second embodiment of the present invention, when the curvature of the trajectory is acquired from the trajectory curvature acquisition unit 24 and it is determined that the calculated axis deviation amount is not effective. In addition, the substitute value is calculated and output based on the past effective axis deviation. For this reason, it is possible to prevent the position from being corrected based on the amount of axis deviation calculated in the curved trajectory, and to improve the reliability of the axis deviation amount estimation processing.

[0075] In addition, even if a loss of axis deviation occurs due to the fact that linear approximation cannot be performed with sufficient accuracy in linear approximation processing, or linear approximation cannot be performed within the desired response time, it is accumulated in the past. The recovery process is performed using a sufficiently reliable misalignment amount, so that the robustness of the misalignment estimation process can be enhanced, and collision prediction / avoidance, which is the main use of such radar equipment, is also possible. Contributes to increasing system safety.

Industrial applicability

The present invention is useful for improving the accuracy of radar technology, and can be applied particularly to a radar device mounted on an automobile.

Claims

The scope of the claims

[1] An axis misalignment estimation method for obtaining an axis misalignment amount of a radar that detects a target in front of a traveling vehicle,

A method of estimating an axis deviation amount, comprising:

[2] In the method for estimating an axis deviation amount according to claim 1,

The echo selection step is characterized by selecting a stationary object echo to which a reflection point belongs to a predetermined partial area of the radar coverage that is divided into a boundary line where the angle formed with the traveling track of the vehicle is approximately 0 °. A method for estimating an axis deviation amount.

[3] In the method of estimating an axis deviation amount according to claim 2,

The echo selection step is characterized by selecting a stationary object echo belonging to any one of the covered areas divided into left and right by a boundary line where the angle formed with the traveling track of the vehicle is approximately 0 °. To estimate the amount of misalignment.

[4] In the method of estimating an axis deviation amount according to claim 1,

The reference straight line calculation step

The first straight line that approximates the distribution of the reflection points of the selected stationary object echo is obtained, and the second straight line that approximates the distribution of the reflection points whose distance from the first straight line is less than the predetermined value is used as a reference. A method for estimating the amount of axis deviation characterized by calculating as a straight line.

[5] A radar that detects a target in front of a traveling vehicle, receives an echo of a transmitted wave, and detects the distance and speed of the reflection point of the received echo and estimates the amount of axis misalignment of the radar In the quantity estimation device,

Select a stationary object echo from the echoes of the transmitted wave based on the distance and velocity A stationary object extraction unit;

An observation area dividing unit for dividing the radar coverage into a plurality of areas;

The vehicle traveling trajectory is obtained by linearly approximating the distribution of reflection points of the echoes of the stationary object selected by the stationary object extraction unit and belonging to a part of the region divided by the observation area dividing unit. A reference straight line calculating unit for obtaining a reference straight line parallel to the reference line, and obtaining an axis deviation amount of the radar based on the reference straight line;

An axis deviation amount estimation device comprising:

[6] In the axial deviation estimation device according to claim 5,

The observation area dividing unit divides the radar coverage into a plurality of areas by a boundary line where the angle formed with the traveling trajectory of the vehicle on which the radar is mounted is approximately 0 °.

[7] In the axial deviation estimation device according to claim 6,

The observation area dividing unit divides the radar coverage into left and right with the radar axis as a boundary line.

[8] In the axial deviation estimation device according to claim 5,

The reference straight line calculation unit performs straight line approximation of the reflection points of the echoes of the stationary object selected by the stationary object extraction unit and belongs to a part of the region divided by the observation area dividing unit. A straight line of 1 is obtained, and further, a second straight line that approximates the distribution of reflection points of echoes of a stationary object whose distance from the first straight line is within a predetermined value is calculated as a reference straight line Quantity calculation device.

[9] In the axial deviation estimation device according to claim 5,

A reference straight line storage unit for storing the reference straight line;

The reference straight line calculation unit performs straight line approximation of the reflection points of the echoes of the stationary object selected by the stationary object extraction unit and belongs to a part of the region divided by the observation area dividing unit. If the first straight line is obtained, and whether or not the first straight line is the reference straight line is determined based on the distance between the first straight line and the reflection point, and the first straight line is the reference straight line, When the first straight line is stored in the reference straight line storage unit and output as the reference straight line, and the first straight line is not set as the reference straight line, the reference straight line stored in the reference straight line storage unit is used. To calculate the reference straight line,

An apparatus for estimating an axis deviation amount.

[10] In the axial deviation amount estimation device according to claim 5,

A trajectory curvature acquisition unit for acquiring the curvature of the trajectory of the vehicle;

A track curvature storage unit for storing the curvature of the track of the vehicle;

A reference straight line storage unit for storing the reference straight line;

The reference straight line calculation unit acquires the curvature of the vehicle trajectory stored in the trajectory curvature storage unit as the curvature of the trajectory of the first vehicle, and acquires the curvature of the trajectory of the second vehicle. The curvature of the trajectory of the second vehicle is stored in the trajectory curvature storage unit, and the curvature of the trajectory of the first vehicle and the curvature of the trajectory of the second vehicle are both predetermined. If the value is within the range, the reflection point of the echo of the stationary object selected by the stationary object extraction unit and belonging to a part of the area divided by the observation area division unit is linearly approximated and used as a reference A straight line is calculated, and when either of the curvature of the track of the first vehicle and the curvature of the track of the second vehicle exceeds a predetermined value, the reference straight line is stored using the reference straight line stored in the reference straight line storage unit. calculate,

An apparatus for estimating an axis deviation amount.