Method for automatically calibrating pitching installation angle of vehicle-mounted millimeter wave radar

Abstract

The invention relates to the technical field of vehicle-mounted millimeter-wave radars, in particular to a method for automatically calibrating the pitching installation angle of a vehicle-mounted millimeter-wave radar, and the method comprises the following steps: (1), data collection; step (2), target filtering; step (3), carrying out straight line fitting; step (4), solving an installation error; and step (5), software compensation. Compared with the prior art, according to the target filtering method, target filtering according to the pitch angle of the target is canceled, target filtering according to the target amplitude is newly added, interference points occurring in the testing process are effectively eliminated, and the influence of the environment on the precision of the self-adaptive calibration result is reduced; secondly, a complex algorithm and tedious calculation are not needed, the complexity of a program is effectively reduced, and track initiation and tracking of a target object can be rapidly helped; and thirdly, multi-sensor fusion, such as a camera and a laser radar, is not needed, and the cost of automatic calibration of the pitching installation angle of the vehicle-mounted millimeter wave radar is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle-mounted millimeter-wave radars, and in particular to a method for automatically calibrating the pitch installation angle of a vehicle-mounted millimeter-wave radar. Background Art

[0002] With the rapid development of autonomous driving technology, intelligent driving assistance systems (ADAS) are becoming more and more popular in automobiles. Millimeter-wave radar is also widely used. As one of the important sensors of the ADAS system, it has become an indispensable part of the ADAS system.

[0003] However, after a certain period of use and mileage, the radar angle may deviate due to radar replacement, vehicle collision, etc., and the measurement accuracy of the target position may deteriorate. In the case of medium and long-range perception, a small angle installation error of the millimeter-wave radar may cause a large distance deviation, thereby increasing the probability of traffic accidents. Therefore, high-precision and simple vehicle-mounted millimeter-wave radar installation angle self-calibration is very necessary. The existing after-installation installation angle self-calibration method of vehicle-mounted millimeter-wave radar requires professional calibration targets, and the calibration process is complicated, with high personnel costs and long time consumption. Summary of the invention

[0004] In order to solve the above technical problem, the present invention proposes a method for automatically calibrating the pitch installation angle of a vehicle-mounted millimeter-wave radar.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] A method for automatically calibrating the pitch installation angle of a vehicle-mounted millimeter-wave radar comprises the following steps:

[0007] Step (1), data collection: within a fixed time n, the target information corresponding to the specific object is collected by the vehicle-mounted millimeter wave radar, and the target information includes the radial distance r, radial velocity rr, distance x in the x direction, distance y in the y direction, pitch angle θ, and amplitude level of the target relative to the radar;

[0008] Step (2), target filtering: preliminarily filtering out target information within a predetermined distance range and relatively stationary with respect to the vehicle-mounted millimeter-wave radar, and the total number of filtered targets is greater than or equal to a predetermined threshold. Then, among the filtered targets, the targets are filtered again according to their amplitudes. If the radial distance difference between multiple targets is lower than the predetermined threshold, the target with the highest amplitude is selected for subsequent calculations, and interference points are eliminated.

[0009] Step (3), straight line fitting: Calculate the difference Δh between each target and the radar installation height based on the measured pitch angles and measured distances of multiple targets. Since the radar installation height h radarKnown, the actual height h corresponding to each target can be calculated tar , calculate each target (y, h tar ) coordinates, select multiple sets of corresponding data in the range of (0.994, 1.001) for linear fitting, and obtain multiple first-order polynomials

[0010] Step (4), solve the installation error: multiple first-order polynomials obtained in step (3) The coefficient of the first-order term in is the rate of change of multiple target detection heights. The angle corresponding to the rate of change of target detection height is the ideal installation elevation angle of the vehicle-mounted millimeter-wave radar. Therefore, through multiple first-order polynomials Calculate multiple ideal installation pitch angles angle of the vehicle-mounted millimeter-wave radar, and average the multiple ideal installation pitch angles angle, that is, the actual installation pitch angle of the vehicle-mounted millimeter-wave radar is approximately Actual installation pitch angle Subtract the ideal installation pitch angle angle to get the actual installation pitch angle installation error value offset of the vehicle-mounted millimeter-wave radar;

[0011] Step (5), software compensation: offset the target pitch angle according to the pitch angle installation error value offset of the actual installation of the vehicle-mounted millimeter-wave radar, thereby realizing software compensation of the millimeter-wave radar pitch angle and completing automatic calibration of the pitch installation angle.

[0012] As a further improvement of the present invention, the specific object described in step (1) is a metal guardrail with continuous equal height and on the same straight line, and the vehicle maintains a uniform speed and travels in a straight line during the collection process.

[0013] As a further improvement of the present invention, the predetermined distance range in step (2) is (-1m, 5m) in the x direction and (5m, 50m) in the y direction; the total number of targets is 50; and the radial distance difference is 0.2m.

[0014] As a further improvement of the present invention, the calculation formula of the difference Δh in step (3) is:

[0015] Δh=r×sin(θ),

[0016] The actual height h corresponding to each target tar The calculation formula is:

[0017] h tar =r×sin(θ)+hradar,

[0018] In the formula, htar is the actual height of the target, r is the radial distance of the target, θ is the pitch angle of the target, and h radar is the installation height of the radar.

[0019] As a further improvement of the present invention, the calculation formula of the linear correlation coefficient coefficient in step (3) is:

[0020]

[0021] In the formula, coefficient is the linear correlation coefficient, num is the total number of targets that meet the conditions, and y i is the distance of each target in the y direction, is the average distance of all eligible targets in the y direction, For each target's actual height, It is the average of the actual heights of all targets that meet the conditions.

[0022] As a further improvement of the present invention, the calculation formula of the ideal installation pitch angle angle described in step (4) is:

[0023]

[0024] Actual installation pitch angle The calculation formula is:

[0025]

[0026] The calculation formula for the actual installed pitch angle installation error value offset is:

[0027]

[0028] Where offset is the elevation angle installation error of the actual radar installation, n is the fixed period, and angle is the ideal radar installation elevation angle.

[0029] As a further improvement of the present invention, in step (4), for multiple angle i Before finding the average, sort the numbers, remove the larger and smaller numbers, and then calculate the average of the remaining numbers to improve the accuracy of the result.

[0030] The beneficial effects of the present invention are:

[0031] The present invention provides a method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar. First, compared with the prior art, in terms of the target filtering method, the target filtering based on the pitch angle of the target is cancelled, and the target filtering based on the target amplitude is newly added, which effectively eliminates the interference points appearing in the test process and reduces the influence of the environment on the accuracy of the adaptive calibration result; second, no complex algorithms and tedious calculations are required, which effectively reduces the complexity of the program and can quickly help start the track and track the target; third, no multi-sensor fusion is required, such as cameras, laser radars, etc., which effectively reduces the cost of automatic calibration of the pitch installation angle of the vehicle-mounted millimeter-wave radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0033] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown, a method for automatically calibrating the pitch installation angle of a vehicle-mounted millimeter-wave radar comprises the following steps:

[0036] Step (1), data collection: within a fixed time n, the target information corresponding to a specific object is collected by the vehicle-mounted millimeter-wave radar. The target information includes the radial distance r, radial velocity rr, distance x in the x direction, distance y in the y direction, pitch angle θ, and amplitude level of the target relative to the radar.

[0037] In this embodiment, the fixed time n can be set to 100 clock cycles, and the specific object is selected as continuous metal guardrails of equal height and on the same straight line. During the collection process, the vehicle maintains a uniform speed and travels in a straight line.

[0038] Step (2), target filtering: Preliminarily filter out target information that is within a predetermined distance range and relatively stationary with respect to the vehicle-mounted millimeter-wave radar, and the total number of filtered targets is greater than or equal to a predetermined threshold. Then, among the filtered targets, filter the targets again according to their amplitudes. If the radial distance difference between multiple targets is lower than a predetermined threshold, select the target with the highest amplitude for subsequent calculations and eliminate interference points.

[0039] In this embodiment, the predetermined distance range is (-1m, 5m) in the x direction and (5m, 50m) in the y direction; the total number of targets is 50; and the radial distance difference is 0.2m.

[0040] Step (3), straight line fitting: Calculate the difference Δh between each target and the radar installation height based on the measured pitch angles and measured distances of multiple targets. Since the radar installation height h radar Known, the actual height h corresponding to each target can be calculated tar , calculate each target (y, h tar ) coordinates, select multiple sets of corresponding data in the range of (0.994, 1.001) for linear fitting, and obtain multiple first-order polynomials

[0041] Specifically, based on the radial distance and pitch angle information of the target, the component of the radial distance in the z direction can be calculated, and the actual height of the target is the sum of the radar installation height and the component of the target radial distance in the z direction. Therefore, based on the radial distance and pitch angle information, the actual height of the target can be obtained.

[0042] Therefore, the calculation formula of the difference Δh is:

[0043] Δh=r×sin(θ),

[0044] The actual height h corresponding to each target tar The calculation formula is:

[0045] h tar =r×sin(θ)+h radar ,

[0046] In the formula, h tar is the actual height of the target, r is the radial distance of the target, θ is the pitch angle of the target, and h radar is the installation height of the radar.

[0047] According to the actual height of the target and the distance in the y direction, multiple targets (y, h tar ) coordinates. Construct the coordinates of y and h tar In the rectangular coordinate system, it can be seen that there is a certain linear relationship between these coordinate points. tar ) coordinates for straight line fitting. Before straight line fitting, the linear correlation coefficient between the coordinate points is calculated to determine the linear correlation between the coordinates. The calculation formula of the linear correlation coefficient coefficient is:

[0048]

[0049] In the formula, coefficient is the linear correlation coefficient, num is the total number of targets that meet the conditions, and y i is the distance of each target in the y direction, is the average distance of all eligible targets in the y direction, For each target's actual height, It is the average of the actual heights of all targets that meet the conditions.

[0050] According to the linear correlation coefficient calculated above, multiple sets of data with linear correlation coefficients that meet the conditions are selected for linear fitting, and multiple first-order polynomials h can be obtained. tar =a1×y+a0.

[0051] Step (4), solve the installation error: multiple first-order polynomials obtained in step (3) The coefficient of the first-order term in is the rate of change of multiple target detection heights. The angle corresponding to the rate of change of target detection height is the ideal installation elevation angle of the vehicle-mounted millimeter-wave radar. Therefore, through multiple first-order polynomials Calculate multiple ideal installation pitch angles angle of the vehicle-mounted millimeter-wave radar, and average the multiple ideal installation pitch angles angle, that is, the actual installation pitch angle of the vehicle-mounted millimeter-wave radar is approximately Actual installation pitch angle Subtracting the ideal installation pitch angle angle, the actual installation pitch angle installation error value offset of the vehicle-mounted millimeter-wave radar can be obtained.

[0052] Specifically, the calculation formula for the ideal installation pitch angle angle is:

[0053]

[0054] Actual installation pitch angle The calculation formula is:

[0055]

[0056] The calculation formula for the actual installed pitch angle installation error value offset is:

[0057]

[0058] Where offset is the actual installation elevation angle error of the radar, n is the fixed period, that is, the total number of data sets for fitting the straight line, and angle is the ideal radar installation elevation angle.

[0059] Furthermore, in order to improve the accuracy of the results, multiple angle i Before finding the average, first calculate the angle i In this embodiment, after removing 10 larger numbers and 10 smaller numbers, the remaining 80 anglei Calculate the average.

[0060] Step (5), software compensation: offset the target pitch angle according to the pitch angle installation error value offset of the actual installation of the vehicle-mounted millimeter-wave radar, thereby realizing software compensation of the millimeter-wave radar pitch angle and completing automatic calibration of the pitch installation angle.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar, characterized in that: The following steps are involved: Step (1), data collection: within a fixed time n, the target information corresponding to the specific object is collected by the vehicle-mounted millimeter wave radar, and the target information includes the radial distance r, radial velocity rr, distance x in the x direction, distance y in the y direction, pitch angle θ, and amplitude level of the target relative to the radar; Step (2), target filtering: preliminarily filtering out target information within a predetermined distance range and relatively stationary with respect to the vehicle-mounted millimeter-wave radar, and the total number of filtered targets is greater than or equal to a predetermined threshold. Then, among the filtered targets, the targets are filtered again according to their amplitudes. If the radial distance difference between multiple targets is lower than the predetermined threshold, the target with the highest amplitude is selected for subsequent calculations, and interference points are eliminated. Step (3), straight line fitting: Calculate the difference Δh between each target and the radar installation height based on the measured pitch angles and measured distances of multiple targets. Since the radar installation height h radar Known, the actual height h corresponding to each target can be calculated tar , calculate each target (y, h tar ) coordinates, select multiple sets of corresponding data in the range of (0.994, 1.001) for linear fitting, and obtain multiple first-order polynomials Step (4), solve the installation error: multiple first-order polynomials obtained in step (3) The coefficient of the first-order term in is the rate of change of multiple target detection heights. The angle corresponding to the rate of change of target detection height is the ideal installation elevation angle of the vehicle-mounted millimeter-wave radar. Therefore, through multiple first-order polynomials Calculate multiple ideal installation pitch angles angle of the vehicle-mounted millimeter-wave radar, and average the multiple ideal installation pitch angles angle, that is, the actual installation pitch angle of the vehicle-mounted millimeter-wave radar is approximately Actual installation pitch angle Subtract the ideal installation pitch angle angle to get the actual installation pitch angle installation error value offset of the vehicle-mounted millimeter-wave radar; Step (5), software compensation: offset the target pitch angle according to the pitch angle installation error value offset of the actual installation of the vehicle-mounted millimeter-wave radar, thereby realizing software compensation of the millimeter-wave radar pitch angle and completing automatic calibration of the pitch installation angle.

2. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: The specific object described in step (1) is a continuous metal guardrail of equal height and on the same straight line. During the acquisition process, the vehicle maintains a uniform speed and travels in a straight line.

3. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: The predetermined distance range in step (2) is (-1m, 5m) in the x direction and (5m, 50m) in the y direction; the total number of targets is 50; and the radial distance difference is 0.2m.

4. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: The calculation formula for the difference △h described in step (3) is: Δh=r×sin(θ), The actual height h corresponding to each target tar The calculation formula is: h tar =r×sin(θ)+h radar , In the formula, h tar is the actual height of the target, r is the radial distance of the target, θ is the pitch angle of the target, and h radar is the installation height of the radar.

5. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: The calculation formula of the linear correlation coefficient in step (3) is: In the formula, coefficient is the linear correlation coefficient, num is the total number of targets that meet the conditions, and y i is the distance of each target in the y direction, is the average distance of all eligible targets in the y direction, For each target's actual height, It is the average of the actual heights of all targets that meet the conditions.

6. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: The calculation formula for the ideal installation pitch angle angle described in step (4) is: Actual installation pitch angle The calculation formula is: The calculation formula for the actual installed pitch angle installation error value offset is: Where offset is the elevation angle installation error of the actual radar installation, n is the fixed period, and angle is the ideal radar installation elevation angle.

7. The method for automatic calibration of the pitch installation angle of a vehicle-mounted millimeter-wave radar according to claim 1, characterized in that: In step (4), for multiple angle i Before finding the average, sort the numbers, remove the larger and smaller numbers, and then calculate the average of the remaining numbers to improve the accuracy of the result.

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