A lidar calibration method, apparatus, computer equipment, and storage medium

Abstract

This application belongs to the field of lidar technology, and provides a lidar calibration method, device, computer equipment, and storage medium. The method includes: rotating the lidar so that the light spot emitted by the nth transmitter of the lidar illuminates the detection area of ​​a calibration plate with a known size from its original position, and recording the rotation data generated by the lidar rotating the nth transmitter; obtaining the true emission angle corresponding to the light spot image coordinates of the target light spot corresponding to the laser beam emitted by the transmitter and the rotation data generated by the motor based on the preset data parameters of the calibration plate, the laser beam emitted by the transmitter, and the rotation data generated by the motor when the light spot emitted by a single transmitter is in its original position; using the true emission angle can more efficiently calibrate the emission angle of the lidar transmitter and restore the true performance of the lidar.

Description

Technical Field

[0001] This application belongs to the field of lidar technology, and in particular relates to a lidar calibration method, device, computer equipment and storage medium. Background Technology

[0002] LiDAR, as a high-precision sensor, plays a vital role in fields such as transportation and surveying. Its key characteristic lies in its ability to detect the surrounding environment and the positional relationships of objects. However, in the manufacturing process of multi-channel LiDAR, the emission angles of each channel's optical path are designed according to specifications. Errors in the manufacturing process may cause the actual emission angles to differ slightly from the set angles. Furthermore, after the LiDAR is manufactured, objective factors such as increased usage time can also lead to discrepancies between the actual emission angles of each channel's optical path and the initial set angles. Summary of the Invention

[0003] This application provides a lidar calibration method, apparatus, computer equipment, and storage medium, aiming to solve the technical problem of the error between the actual emission angle of the lidar channel optical path and the initially set angle.

[0004] In a first aspect, embodiments of this application provide a lidar calibration method, including:

[0005] The lidar is rotated so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and the rotation data generated by the lidar rotating the nth emitter is recorded, where n is a positive integer;

[0006] Determine the preset data parameters of the calibration board;

[0007] Obtain the target spot image coordinates of the light spot of the nth emitter illuminating the detection area;

[0008] Based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, the actual emission angle of the light spot emitted by the nth transmitter when it is in the original position is obtained, wherein the actual emission angle is used to calibrate the set emission angle of the nth transmitter.

[0009] In a first possible implementation of the first aspect, the preset data parameters of the calibration board include a preset distance between the calibration board and the lidar, and two-dimensional image feature data of the calibration board;

[0010] The process of obtaining the true emission angle of the light spot emitted by the nth transmitter at its original position based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data includes:

[0011] Based on the preset distance and the two-dimensional image feature data, calculate the target beam vector corresponding to the target spot image coordinates in the spatial coordinate system;

[0012] Based on the rotation data and the target beam vector, obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position;

[0013] The true emission angle of the light spot emitted by the nth emitter at the original position is determined based on the original beam vector.

[0014] In a first possible implementation of the first aspect, the preset data parameters of the calibration board further include the radar spatial coordinates of the lidar in the spatial coordinate system; the target spot image coordinates and the two-dimensional image feature data are both pixel data in the two-dimensional image coordinate system of the calibration board;

[0015] The step of calculating the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the preset distance and the two-dimensional image feature data includes:

[0016] Based on the radar spatial coordinates, the preset distance, and the two-dimensional image feature data, a first mapping relationship between the two-dimensional image coordinate system and the spatial coordinate system is obtained;

[0017] Calculate the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the first mapping relationship;

[0018] The step of obtaining the original beam vector corresponding to the light spot emitted by the nth emitter at its original position based on the rotation data and the target beam vector includes:

[0019] The target beam vector is moved in reverse according to the rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position.

[0020] In a first possible implementation of the first aspect, the rotation data includes horizontal rotation data and pitch data;

[0021] The step of reversing the target beam vector according to the rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter at the original position includes:

[0022] The target beam vector is horizontally rotated in the opposite direction according to the horizontal rotation data to obtain the transition beam vector.

[0023] According to the pitch data, the beam corresponding to the transition beam vector is pitched in the opposite direction to obtain the original beam vector corresponding to the light spot emitted by the nth transmitter when it is in the original position.

[0024] or

[0025] According to the pitch data, the beam corresponding to the target beam vector is pitched in the opposite direction to obtain the transition beam vector;

[0026] The beam corresponding to the transition beam vector is rotated horizontally in the opposite direction according to the horizontal rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position.

[0027] In a first possible implementation of the first aspect, determining the true emission angle corresponding to the light spot emitted by the nth emitter at the original position based on the original beam vector includes:

[0028] Obtain a lidar coordinate system that has a second mapping relationship with the spatial coordinate system;

[0029] Based on the second mapping relationship, the original beam vector is transformed into the lidar coordinate system to obtain the true emission angle corresponding to the spot of the laser beam emitted by a single transmitter when it is in the original position; the true emission angle includes the vertical angle of the spot and the horizontal angle of the spot, the vertical angle of the spot is the angle between the laser beam emitted by the nth transmitter in the original position and the horizontal plane of the lidar coordinate system, and the horizontal angle of the spot is the angle between the laser beam emitted by the nth transmitter in the original position and the vertical plane of the lidar coordinate system.

[0030] In a first possible implementation of the first aspect, obtaining the lidar coordinate system that has a second mapping relationship with the spatial coordinate system includes:

[0031] Obtain the established reference beam in the spatial coordinate system, and the lidar coordinate system containing the reference beam;

[0032] The step of transforming the original beam vector to the lidar coordinate system based on the second mapping relationship to obtain the true emission angle corresponding to the light spot emitted by a single transmitter at its original position includes:

[0033] Determine the vector of the first beam corresponding to the first transmitter of the lidar, and the vector of the (n-1)th beam corresponding to the (n-1)th transmitter other than the first transmitter;

[0034] The first beam is rotated to the reference beam to transform the vector of the first beam to the lidar coordinate system, thereby obtaining the true emission angle of the light spot emitted by the first transmitter in the lidar coordinate system.

[0035] Calculate the rotation information generated by the first beam rotating to the reference beam, and rotate the vector of the (n-1)th beam according to the rotation information to transform the vector of the (n-1)th beam to the lidar coordinate system, so as to obtain the true emission angle of the light spot emitted by the (n-1)th transmitter in the lidar coordinate system.

[0036] In a first possible implementation of the first aspect, the method further includes:

[0037] The actual emission angle is transmitted to the lidar, so that the nth transmitter of the lidar calculates the lidar detection data according to the actual emission angle when it is working.

[0038] The beneficial effect of the first aspect of this application is that: based on the preset data parameters of the calibration board, the target spot image coordinates corresponding to the laser beam emitted by the transmitter, and the rotation data generated by the motor, the true emission angle corresponding to the original position of the light spot emitted by a single transmitter can be obtained. Using the true emission angle, the emission angle of the lidar transmitter can be calibrated more efficiently, restoring the true performance of the lidar.

[0039] Secondly, embodiments of this application provide a lidar calibration device, comprising:

[0040] A rotation module is used to rotate the lidar so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and records the rotation data generated by the lidar rotating the nth emitter, where n is a positive integer;

[0041] The determination module is used to determine the preset data parameters of the calibration board;

[0042] The acquisition module is used to acquire the target spot image coordinates illuminated by the spot of the nth emitter on the detection area;

[0043] The calculation module is used to obtain the actual emission angle of the light spot emitted by the nth transmitter when it is in the original position based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, wherein the actual emission angle is used to calibrate the set emission angle of the nth transmitter.

[0044] Thirdly, the present invention also proposes a computer device, the computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the computer program to implement the steps of the lidar calibration method as described in any of the preceding claims.

[0045] Fourthly, the present invention also proposes a storage medium storing a computer-readable storage program, which, when executed by a processor, implements the steps of the lidar calibration method as described in any of the preceding claims.

[0046] It is understood that the beneficial effects of the third or fourth aspects mentioned above can be found in the relevant descriptions in the first or second aspects mentioned above, and will not be repeated here. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application;

[0049] Figure 2 This is a schematic diagram showing the laser beam emitted by the lidar illuminating a 10% reflective calibration plate in a conventional lidar calibration method.

[0050] Figure 3 This is a schematic diagram of a lidar calibration system in a coordinate plane of a spatial coordinate system according to one embodiment of this application;

[0051] Figure 4 This is a schematic flowchart of an embodiment of the lidar calibration method provided in this application;

[0052] Figure 5 This is a schematic diagram of the light spot emitted by the lidar illuminating the checkerboard calibration plate in one embodiment of this application;

[0053] Figure 6 A flowchart illustrating one embodiment of this application for obtaining the true emission angle of a single transmitter.

[0054] Figure 7 This is a schematic diagram of a laser radar beam illuminating a calibration plate of known fixed size in one embodiment of this application.

[0055] Figure 8This is a schematic flowchart of another embodiment of the lidar calibration method provided in this application;

[0056] Figure 9 This is a schematic diagram of rotation information generated by rotating the first beam to the reference beam in one embodiment of this application;

[0057] Figure 10 This is a schematic diagram of the structure of the lidar calibration device provided in the embodiments of this application. Detailed Implementation

[0058] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0059] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0060] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0061] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0062] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0063] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0064] This invention provides a computer device, such as... Figure 1 As shown, Figure 1 This is a schematic diagram of a computer device provided according to an embodiment of the present application. The computer device 1 of this embodiment includes: at least one processor 1001 (… Figure 1 Only one is shown in the diagram), memory 1005, and computer program 1006 stored in said memory 1005 and executable on said at least one processor 1001, wherein the processor 1001 executes said computer program 1006 to implement the steps in the embodiments of the lidar calibration method of this application.

[0065] The computer device 1 also includes a lidar interface 1003 for connecting to a lidar device to be calibrated. The computer device 1 can obtain relevant parameters of the lidar device to be calibrated through the lidar interface 1003. The computer device 1 can also transmit relevant data to the lidar device to be calibrated through the lidar interface 1003.

[0066] The computer device 1 can be a computer device specifically used for calibrating the lidar. This computer device can directly issue control commands to the lidar or obtain the lidar's operating parameter information. After the lidar leaves the factory, the user can use the computer device at any time to run the computer program 1006 to calibrate the lidar.

[0067] The computer device 1 may also include a camera interface 1004, which can be used to collect two-dimensional image feature data of the calibration board of the lidar; in some embodiments, the camera interface 1004 can be connected to the internal image sensor of the computer device 1, and in other embodiments, the camera interface 1004 can also be connected to an external camera device of the computer device 1.

[0068] Those skilled in the art will understand that Figure 1The computer device 1 is merely an example and does not constitute a limitation on the computer device 1. It may include more or fewer components than shown, or combine certain components, or different components.

[0069] The processor 1001 may be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0070] In some embodiments, the memory 1005 may be an internal storage unit of the computer device 1, such as a hard disk or memory of the computer device 1. In other embodiments, the memory 1005 may be an external storage device of the computer device 1, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the computer device 1. Further, the memory 1005 may include both internal and external storage units of the computer device 1. The memory 1005 is used to store the operating system and the computer-executable program of the lidar calibration method, etc., and the computer-executable program may include at least an image processing program and a motion control program.

[0071] As we can understand, a lidar (Light Detection and Ranging) system is a radar system that uses laser beams to detect the position, velocity, and other characteristics of a target. Its working principle involves emitting a laser beam (which serves as the detection signal) towards the target, then comparing the received signal reflected back from the target (the target echo) with the emitted signal. After appropriate processing, relevant information about the target (target azimuth, distance, altitude, attitude, velocity, shape, etc.) can be obtained, enabling the detection, tracking, and identification of targets such as pedestrians and vehicles. A lidar system typically consists of a laser transmitter, an optical receiver, a turntable, and an information processing system.

[0072] The lidar to be calibrated in this invention application is a multi-channel lidar, which consists of multiple transmitters and receivers. Multiple beams are obtained through the rotation of a motor, with each channel corresponding to one transmitter and receiver. During the manufacturing process of the multi-channel lidar, the emission angle of each channel's optical path is assembled according to the design angle. However, due to factors such as the lidar's transmitter emission angle not perfectly achieving the design angle accuracy during assembly, or the lidar's actual emission angle deviating from the initial design angle due to increased usage time after leaving the factory, the actual emission angle of the lidar's transmitter may differ from the initial design angle. This results in an error between the actual point cloud data sensed by the lidar and the theoretically obtained point cloud data based on the transmitter's design angle, thus distorting the lidar's performance. Current vehicle-mounted and roadside lidars can achieve ranging capabilities of several hundred meters. If the actual emission angle deviation of the lidar is 0.1°, the error at 200 meters will reach more than 0.3 meters, leading to highly inaccurate final detection data and severely impacting the user experience.

[0073] To address the technical problem mentioned in the background art of "the technical problem that there is an error between the actual emission angle of the laser radar channel optical path and the initially set angle", in a first aspect, the present invention proposes an embodiment of a laser radar calibration method. This laser radar calibration method can be used in a specific radar calibration environment, that is, a calibration board is placed directly in front of the laser radar, and the laser radar is calibrated by the calibration board.

[0074] It should be noted that the calibration plate used in conventional calibration lidar has a 10% reflectivity. Here, 10% reflectivity refers to the proportion of laser light that can be reflected by the reflective object to the emitted laser light. In this embodiment, the 10% reflectivity calibration plate of the calibration lidar is replaced with a calibration plate with a known fixed size. The camera can collect two-dimensional image feature data from the calibration plate with a known fixed size.

[0075] In the specific calibration scheme, Figure 3 This is a schematic diagram of a lidar calibration system in the YOZ coordinate plane of a spatial coordinate system (this embodiment uses the YOZ coordinate plane being perpendicular to the horizontal plane as an example for illustration; the YOZ coordinate plane is also referred to as the vertical plane in the following text; the corresponding XOY coordinate plane of the spatial coordinate system is parallel to the horizontal plane, and the XOY coordinate plane is perpendicular to the YOZ coordinate plane; the XOY coordinate plane is also referred to as the horizontal plane in the following text). The lidar calibration system includes the lidar itself, a calibration plate with fixed size characteristics, and a computer device for executing the lidar calibration method.

[0076] like Figure 3As shown, the origin of the spatial coordinate system is the center O of the lidar's emission point. The direction directly in front of the lidar is the positive Y-axis. The direction directly above the lidar and perpendicular to the Y-axis is the positive Z-axis. The direction perpendicular to both the Y and Z axes and pointing to the right of the YOZ plane is the positive X-axis. A calibration plate with fixed dimensions is positioned directly in front of the lidar, meaning its plane is perpendicular to the Y-axis of the spatial coordinate system, and the distance between them is D meters. Figure 3 The plane coordinates corresponding to the intersection of the calibration plate and the Y-axis are (D,0), then the spatial coordinates of this intersection point are (0,D,0).

[0077] Furthermore, Figure 4 The diagram illustrates a flowchart of a first embodiment of the lidar calibration method provided in this application. This is an example, not a limitation. In this embodiment, the lidar calibration method is executed by a computer device. The computer device establishes a data transmission connection with the lidar to be calibrated to receive parameter data from the lidar or to transmit data to the lidar. The computer device can acquire two-dimensional image feature points in a calibration board with known fixed dimensions using a camera. For example, in this embodiment, the calibration board can be a checkerboard with known fixed grid dimensions, and the pixel coordinates of the grid feature points on the checkerboard can be acquired using a camera.

[0078] In specific applications, the application scenario of the lidar calibration method in this embodiment is illustrated by taking the lidar after it has been assembled and shipped from the factory, and the user using the aforementioned computer equipment to execute the relevant program of the lidar calibration method described in this embodiment. The lidar can be applied to vehicles with driving functions such as automobiles, and the user can be a professional staff member of an automobile manufacturer or sales store, or a vehicle driver, etc.

[0079] It should be noted that in existing technologies, the emission angle of the transmitters of multi-channel lidar is often calibrated before the lidar is assembled and shipped from the factory. The existing calibration method usually requires moving the light spots emitted by each transmitter to the same position (target position) on a calibration plate (such as a calibration plate with a 10% reflective surface) that can receive the light spots. The coordinates of the light spots are captured by sensors such as infrared cameras to determine whether the light spots have moved to the target position coordinates. For each lidar transmitter, the motor needs to rotate multiple times to make the light spot of a single lidar transmitter illuminate the target position on the calibration plate. This is time-consuming, inefficient, and seriously affects the production schedule of lidar.

[0080] The lidar calibration method in this embodiment can be applied not only to lidar applications after assembly and delivery, but also to other applications. Unlike conventional lidar calibration methods, this method does not require the lidar motor to rotate multiple times, significantly reducing the number of motor movements and greatly improving calibration efficiency. In conventional calibration schemes, multiple motor movement operations are required for each channel transmitter, while in this embodiment, each channel motor only needs to move once to obtain the true emission angle. While ensuring the accuracy of the results, the calibration time can be greatly shortened.

[0081] like Figure 4 As shown, the lidar calibration method provided in this embodiment mainly includes the following steps:

[0082] Step S01: Rotate the lidar so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and record the rotation data generated by the lidar rotating the nth emitter, where n is a positive integer;

[0083] It should be noted that the lidar is rotated as a whole during calibration. However, during the rotation of the lidar, the laser transmitting and receiving modules inside the lidar will rotate under the action of inertia, which may affect the calibration. Since this embodiment calibrates the lidar after it has been assembled and shipped from the factory, the lidar housing cannot be disassembled (i.e., the inertial force on the transmitting and receiving modules cannot be controlled manually using tools).

[0084] Therefore, in this embodiment of the lidar calibration method, before performing step S01 (rotating the lidar), the computer device sends a control signal to the lidar. This control signal is used to restrict the laser transmitting and receiving module or the drive shaft of the scanning motor during the lidar's rotation. In specific implementations, this embodiment can lock and release the laser transmitting and receiving module or the drive shaft of the scanning motor by setting a limiting structure, or by using hardware circuitry to send a lock signal to the motor, preventing the drive shaft of the scanning motor from rotating under inertial force.

[0085] Furthermore, the rotation data can be the rotation angle and / or pitch angle generated by the motor rotating the transmitter. In this embodiment, the motion control program of the computer device sends a calibration command to the lidar, controlling the lidar motor to rotate the transmitter of a single channel. When the light spot emitted by the transmitter of a single channel illuminates the detection area of ​​the calibration board, the motor stops rotating, so that the light spot emitted by the transmitter illuminates the detection area of ​​the calibration board. Since the detection area is a relatively large area, the computer device only needs to control the motor to rotate once to move the light spot emitted by the transmitter to... Figure 4The light spot detection area is shown, without requiring the motor to move multiple times to make the transmitter's light spot fall into the area, as is the case with conventional calibration methods. Figure 2 The target location.

[0086] Step S02: Determine the preset data parameters of the calibration board;

[0087] In this embodiment, a checkerboard pattern can be used as a calibration plate with a known fixed size. The camera can collect two-dimensional image feature data from the calibration plate with a known fixed size.

[0088] The preset data parameters of the calibration board include the preset distance between the calibration board and the lidar (e.g., the lidar and the checkerboard are D meters apart) and the two-dimensional image feature data of the calibration board (e.g., the pixel coordinates of known grid feature points on the checkerboard).

[0089] The two-dimensional image feature data of the chessboard grid is as follows: Figure 5 As shown, the intersection point Cp of the checkerboard grid and the Y-axis of the spatial coordinate system with the checkerboard plane is (0, D, 0) because the checkerboard grid is D meters away from the LiDAR. This intersection point is pre-set. Therefore, the pixel coordinates (Xcpixel, Ycpixel) of the checkerboard grid at Cp can be obtained. Knowing that the size of each cell in the checkerboard grid is S meters, we first find the four corner points C1, C2, C3, and C4 of the cell where Cp is located. Then, based on the ratio between pixels and the checkerboard grid size, we can calculate... To determine the spatial coordinates of one of the grid corner points, for example, the calculation process is as follows: the pixel distance between C1 and C2 is PD1, the pixel distance between C2 and C4 is PD2, the pixel distance from Cp to the line with C1 and C2 as endpoints is PG1, and the pixel distance from Cp to the line with C2 and C4 as endpoints is PG2. Then, the spatial coordinates of C2 can be determined as: (PG2 / PD1*S, D, PG1 / PD2*S). Following the same calculation method, the spatial coordinates of the other corner points can be calculated based on the grid size.

[0090] In a specific implementation, a computer device can acquire two-dimensional image feature data of the calibration board through a camera. The computer device can call an image processing program to analyze and process the image of the calibration board, thereby determining the pixel coordinates corresponding to the two-dimensional image feature data of the calibration board.

[0091] Step S03: Obtain the target spot image coordinates illuminated by the spot of the nth emitter on the detection area;

[0092] In a specific implementation, the computer device can use a camera to capture images of light spots formed by the light beams emitted by each transmitter of the radar illuminating the detection area. The computer device can then call an image processing program to analyze and process the light spot images on the calibration board, thereby determining the coordinates of the target light spot image of the nth transmitter illuminating the detection area.

[0093] Step S04: Based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, obtain the actual emission angle corresponding to the light spot emitted by the nth transmitter when it is in the original position, wherein the actual emission angle calibrates the set emission angle of the nth transmitter.

[0094] Preferably, in this embodiment, step S04 further includes the following sub-steps:

[0095] Sub-step S041: Based on the preset distance and the two-dimensional image feature data, calculate the target beam vector corresponding to the target spot image coordinates in the spatial coordinate system;

[0096] In a specific implementation, the preset data parameters of the calibration board also include the radar spatial coordinates of the lidar in the spatial coordinate system; the target spot image coordinates and the two-dimensional image feature data are both pixel data in the two-dimensional image coordinate system of the calibration board;

[0097] The step of calculating the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the preset distance and the two-dimensional image feature data includes:

[0098] Based on the radar spatial coordinates, the preset distance, and the two-dimensional image feature data, a first mapping relationship between the two-dimensional image coordinate system and the spatial coordinate system is obtained;

[0099] Calculate the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the first mapping relationship;

[0100] like Figure 7 As shown, when the light spot stops in the detection area, the center CL of the target light spot is determined, and the pixel coordinates of the light spot center CL (i.e. the image coordinates of the target light spot) are recorded as CL;

[0101] The preset distance is: D meters for the checkerboard-grid distance laser radar;

[0102] The radar's spatial coordinates in the spatial coordinate system are (0,0,0). The intersection of the Y-axis of the spatial coordinate system and the checkerboard plane is Cp. Since the checkerboard is D meters away from the radar, the spatial coordinates of the intersection point Cp are (0,D,0).

[0103] The two-dimensional image feature data includes: the four corner points Ca, Cb, Cc, and Cd of the grid where CL is located;

[0104] During the image processing process, the computer device first determines the pixel distance from Ca to Cb as PD1, the pixel distance from Cb to Cd as PD2, the pixel distance from Cl to the line with Ca and Cb as endpoints as PG1, and the pixel distance from Cl to the line with Cb and Cd as endpoints as PG2. Then, the spatial coordinates of Cb are determined to be (Xb,D,Zb). Based on the radar spatial coordinates (0,0,0), the preset distance D meters, and the pixel data in the two-dimensional image coordinate system of the calibration board collected by the camera, the first mapping relationship (coordinate transformation relationship between the two-dimensional image coordinate system and the spatial coordinate system) between the two-dimensional image coordinate system and the spatial coordinate system can be determined. Then, the spatial coordinates corresponding to the target spot image coordinates CL can be calculated as: (Xb-PG2 / PD1*S,D,Zb-PG1 / PD2*S). After determining the spatial coordinates corresponding to the center CL of the target spot, the vector corresponding to this coordinate is the target beam vector Vn corresponding to the beam of the target spot image in the spatial coordinate system.

[0105] Sub-step S042: Based on the rotation data and the target beam vector, obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position;

[0106] Understandably, before step S01 is executed (i.e. before the motor corresponding to the lidar rotates by a certain angle), the original beam vector corresponding to the light spot at its initial original position is Vo.

[0107] When the light spot emitted by each transmitter moves to the detection area of ​​the calibration plate, the computer equipment can calculate the target beam vector Vn corresponding to the light spot at that moment. Vn is obtained after Vo is rotated by a certain angle by the motor corresponding to the lidar. Therefore, in order to obtain Vo, the target beam vector Vn needs to be moved in reverse according to the known rotation angle (rotation data) to obtain the original beam vector Vo corresponding to the light spot emitted by a single transmitter at the original position.

[0108] Sub-step S043: Determine the actual emission angle of the light spot emitted by the nth emitter at the original position based on the original beam vector.

[0109] Specifically, the coordinate system in which the original beam vector Vo of each transmitter of the lidar is located is a spatial coordinate system. During the lidar spot angle calibration process, the position of the beam model in the lidar coordinate system remains unchanged. However, the position of the beam model in the spatial coordinate system changes as the lidar transmitter moves. Therefore, it is necessary to transform the relevant data of the original beam vector of the transmitter from the spatial coordinate system to the lidar coordinate system in order to determine the true emission angle of the spot emitted by a single transmitter at the original position.

[0110] In the technical solution of this embodiment, the computer device first calculates the original beam vector model Vo in the spatial coordinate system corresponding to the transmitter of the lidar in the initial state, and then transforms the beam vector model Vo into the lidar coordinate system, thereby determining the actual emission angle corresponding to the light spot emitted by a single transmitter in the initial state.

[0111] In practice, when the computer device runs the program, it can obtain a reference axis that is pre-configured in the program and set in the lidar coordinate system for each channel transmitter. Then, each channel transmitter is rotated around the reference axis according to the original beam vector model Vo. The angle generated after the rotation is the actual emission angle.

[0112] Step S05: The actual emission angle is transmitted to the lidar, so that the nth transmitter of the lidar calculates the lidar detection data according to the actual emission angle when it is working. In this way, the lidar can transmit data according to the actual angle, instead of transmitting data according to the design angle, thus ensuring the accuracy of the lidar detection data results.

[0113] The beneficial effects of the technical solution in this embodiment are as follows: Based on the preset data parameters of the calibration board, the target spot image coordinates of the transmitter, and the rotation data generated by the motor, the true emission angle corresponding to the original position of the light spot emitted by a single transmitter can be obtained. This allows for more efficient calibration of the emission angle of the lidar transmitter, restoring the true performance of the lidar after it is assembled and shipped from the factory, thus improving the user experience. Furthermore, compared with the existing conventional calibration method of moving the light spot to the target position, this embodiment can significantly reduce the number of motor movements, greatly improving calibration efficiency. In conventional calibration schemes, multiple motor movement operations are required for each channel transmitter, while in this embodiment, each channel motor only needs to move once to obtain the true emission angle. While ensuring the accuracy of the results, the calibration time can be greatly shortened.

[0114] Furthermore, in another embodiment, the rotation data includes horizontal rotation data and pitch data;

[0115] Understandably, lidar has pitch and rotation motors, enabling the laser beam emitted by the lidar transmitter to be directed in any direction. This type of lidar is more functional. A common calibration method for this type of lidar requires using the pitch and rotation motors to control the laser in single-point mode to move a single spot to the same position on the calibration plate (10% reflective surface). Figure 2 (The rectangular target position), since the motion control program of the host computer does not know how many times the motor needs to be moved during the movement, the host computer performs a calculation every time the motor is moved until the light spot is moved to the desired position. Figure 2 The calibration process only ends when the target point is located. Therefore, the motor needs to be moved repeatedly to find the target point. Taking a 64-channel LiDAR as an example, the entire calibration process requires about 270 movements of the pitch motor and the horizontal rotation motor, taking about 5.5 minutes. The calibration efficiency is not high.

[0116] In this embodiment, to address the aforementioned technical problem, when performing step S01, the lidar in single-point mode is controlled by a pitch motor and a horizontal rotation motor, so that the light spot emitted by the single (nth) transmitter illuminates the detection area of ​​the calibration plate from its original position, and the horizontal rotation data and pitch data generated by the lidar rotating the nth transmitter are recorded.

[0117] Accordingly, in performing step S042, which involves obtaining the original beam vector corresponding to the light spot emitted by the nth emitter at its original position based on the rotation data and the target beam vector, this embodiment may include both methods:

[0118] The first method is to perform a horizontal rotation in the opposite direction on the beam corresponding to the target beam vector according to the horizontal rotation data to obtain a transition beam vector; and to perform a pitch operation in the opposite direction on the beam corresponding to the transition beam vector according to the pitch data to obtain the original beam vector corresponding to the light spot emitted by the nth transmitter when it is in the original position.

[0119] Understandably, the target beam vector Original beam vector The beam vector is obtained after rotating by angle α using the horizontal motor and pitching by angle θ using the pitch motor of the lidar. Therefore, in order to obtain the original beam vector... The target beam vector can be set first. Rotate the motor by an angle -α around the Z-axis (horizontal motor rotation axis) of the spatial coordinate system, and then tilt it by an angle -θ around the X-axis (pitch motor pitch axis) of the spatial coordinate system to obtain the vector. The specific operating formula is as follows:

[0120]

[0121] in, To determine the target beam vector The transition beam vector after rotating by an angle -α around the Z-axis of the spatial coordinate system. It is the rotation axis vector (Z-axis of the spatial coordinate system);

[0122]

[0123] in, To transition beam vector The original beam vector obtained by pitching -θ angle around the X-axis of the spatial coordinate system The rotation axis vector (X-axis of the spatial coordinate system);

[0124] The second method involves performing a reverse pitch operation on the beam corresponding to the target beam vector according to the pitch data to obtain a transition beam vector; and performing a reverse horizontal rotation on the beam corresponding to the transition beam vector according to the horizontal rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth transmitter when it is in the original position. The specific rotation pitch operation formula is consistent with the principle of the rotation pitch operation formula in the first method mentioned above, and will not be elaborated here.

[0125] Accordingly, after performing step S043, the actual emission angle includes the vertical angle of the light spot and the horizontal angle of the light spot. The vertical angle of the light spot is the angle between the light beam emitted by the nth transmitter in the original position and the horizontal plane of the spatial coordinate system, and the horizontal angle of the light spot is the angle between the light beam emitted by the nth transmitter in the original position and the vertical plane of the spatial coordinate system.

[0126] The beneficial effects of the technical solution in this embodiment are as follows: Based on the preset data parameters of the calibration board, the target spot image coordinates of the transmitter, and the horizontal rotation data and pitch data generated by the motor, the vertical angle and horizontal angle of the spot emitted by a single transmitter at its original position can be obtained. This allows for more efficient calibration of the emission angle of the lidar transmitter, restoring the true performance of the lidar. Compared with conventional calibration schemes, this significantly reduces the number of movements of the pitch motor and horizontal rotation motor. While ensuring the accuracy of the results, the calibration time can be greatly shortened.

[0127] Furthermore, in yet another embodiment, such as Figure 8 As shown, sub-step S043 further includes:

[0128] Step S0431: Obtain the lidar coordinate system that has a second mapping relationship with the spatial coordinate system;

[0129] In a specific implementation, a reference beam pre-configured in the computer execution program and established in the spatial coordinate system can be obtained, and a lidar coordinate system containing the reference beam pre-configured in the program can be obtained.

[0130] Step S0432: Based on the second mapping relationship, the original beam vector is transformed into the lidar coordinate system to obtain the true emission angle corresponding to the light spot emitted by a single transmitter at its original position.

[0131] In a specific implementation, the vector of the first beam corresponding to the first transmitter (n=1) of the lidar is first determined; then the first beam is rotated to the reference beam to transform the vector of the first beam to the lidar coordinate system, so as to obtain the true emission angle of the light spot emitted by the first transmitter in the lidar coordinate system.

[0132] Calculate the rotation information generated by the first beam rotating to the reference beam, and rotate the vector of the (n-1)th beam according to the rotation information to transform the vector of the (n-1)th beam to the lidar coordinate system, so as to obtain the true emission angle of the light spot emitted by the (n-1)th transmitter in the lidar coordinate system.

[0133] It should be noted that, in order to calculate the emission angle of the light spot according to the logic of vertical and horizontal angles in the lidar coordinate system, refer to... Figure 9 In this embodiment, the vector of the light spot emitted by the first channel transmitter can be calculated. The vector corresponding to Cp (pre-established) Rotation information (including the rotation axis) of the corresponding beam as the reference beam And the rotation angle θr), the calculation formula is as follows:

[0134]

[0135] in, The vector representing the first beam. The vector representing the axis of rotation. This represents the vector corresponding to the reference beam.

[0136]

[0137] Wherein, θr represents the rotation angle generated when the first beam rotates to the reference beam.

[0138] Find the axis of rotation After rotating by an angle θr, the light spot vector emitted by each transmitter of the lidar is respectively processed by... The rotation transformation is θr, which is the rotation of the rotation axis. The resulting light spot vector can be used to solve for the angle. The vertical angle of the light spot is the angle between the beam emitted by the transmitter in the original position and the XOY plane (horizontal plane) of the lidar coordinate system. The horizontal angle of the light spot is the angle between the beam emitted by the transmitter in the original position and the YOZ plane (vertical plane) of the lidar coordinate system.

[0139] Understandably, after obtaining the target beam model in the spatial coordinate system, it is necessary to transform the model to the lidar coordinate system and set a reference beam, i.e., to set a coordinate system, which is the lidar coordinate system. When used as a sensor, the data information output by the lidar is based on the lidar coordinate system. In this embodiment, the settings will be pre-set according to the requirements set in the initial design of the lidar. For example, if the lidar has 32 channels, and the unit vector of the vector of the 16 channels in the lidar coordinate system is specified as (0,1,0), then the 16 channels in the measured beam model need to be rotated to the vector direction of (0,1,0) according to the vector rotation formula, and the rotation axis vector of this rotation process needs to be calculated. And the rotation angle θr, then the entire beam vector model revolves around After rotating θr, the relative position of the beam vector in the entire beam vector model remains unchanged, but the x, y, and z values ​​in the vector of the spatial coordinate system change. This process is to transform the beam vector model to a specified position in the lidar coordinate system, and finally solve the angle according to the lidar coordinate system relative angle solution method.

[0140] The technical solution of this embodiment can more efficiently calibrate the emission angle of the lidar reflector and restore the true performance of the lidar. In addition, this embodiment can also make the included angle between the various transmitters of the lidar closer to the true value. For example, the horizontal included angle between the two emitted light spots of the lidar's adjacent transmitters 1 and 2 is 10 degrees, but the actual included angle between the two transmitters during assembly is 10.5 degrees. This embodiment can obtain the true included angle of 10 degrees between the emitted light spots of adjacent transmitters and provide the true included angle data to the lidar, so that the two adjacent transmitters of the lidar emit lasers according to the true relative emission angle when working, further ensuring the detection accuracy of the lidar.

[0141] In one embodiment, such as Figure 10 As shown, the present invention also provides a lidar calibration device, comprising:

[0142] The rotation module 10 is used to rotate the lidar so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and records the rotation data generated by the lidar rotating the nth emitter, where n is a positive integer;

[0143] The determination module 20 is used to determine the preset data parameters of the calibration board;

[0144] The acquisition module 30 is used to acquire the target spot image coordinates illuminated by the spot of the nth emitter on the detection area;

[0145] The calculation module 40 is used to obtain the actual emission angle of the light spot emitted by the nth transmitter when it is in the original position based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, wherein the actual emission angle is used to calibrate the set emission angle of the nth transmitter.

[0146] It should be noted that the above-mentioned device can be understood as a chip in the computer device; the information interaction, execution process and other contents between the above-mentioned devices / units are based on the same concept as the method embodiment of this application, and their specific functions and technical effects can be found in the method embodiment section, which will not be repeated here.

[0147] Furthermore, this application embodiment also provides a storage medium, which is a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps in the above-described method embodiments.

[0148] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of this application can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a photographing device / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals.

[0149] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0150] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0151] In the embodiments provided in this application, it should be understood that the disclosed apparatus / network devices and methods can be implemented in other ways. For example, the apparatus / network device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0152] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0153] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A lidar calibration method, characterized in that, include: The lidar is rotated so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and the rotation data generated by the lidar rotating the nth emitter is recorded, where n is a positive integer; Determine the preset data parameters of the calibration board; Obtain the target spot image coordinates of the light spot of the nth emitter illuminating the detection area; Based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, the actual emission angle of the light spot emitted by the nth transmitter at its original position is obtained. The actual emission angle is used to calibrate the set emission angle of the nth transmitter.

2. The method as described in claim 1, characterized in that, The preset data parameters of the calibration board include the preset distance between the calibration board and the lidar, and the two-dimensional image feature data of the calibration board; The process of obtaining the true emission angle of the light spot emitted by the nth transmitter at its original position based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data includes: Based on the preset distance and the two-dimensional image feature data, calculate the target beam vector corresponding to the target spot image coordinates in the spatial coordinate system; Based on the rotation data and the target beam vector, obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position; The true emission angle of the light spot emitted by the nth emitter at the original position is determined based on the original beam vector.

3. The method as described in claim 2, characterized in that, The preset data parameters of the calibration board also include the radar spatial coordinates of the lidar in the spatial coordinate system; the target spot image coordinates and the two-dimensional image feature data are both pixel data in the two-dimensional image coordinate system of the calibration board; The step of calculating the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the preset distance and the two-dimensional image feature data includes: Based on the radar spatial coordinates, the preset distance, and the two-dimensional image feature data, a first mapping relationship between the two-dimensional image coordinate system and the spatial coordinate system is obtained; Calculate the target beam vector in the spatial coordinate system corresponding to the target spot image coordinates based on the first mapping relationship; The step of obtaining the original beam vector corresponding to the light spot emitted by the nth emitter at its original position based on the rotation data and the target beam vector includes: The target beam vector is moved in reverse according to the rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position.

4. The method as described in claim 3, characterized in that, The rotation data includes horizontal rotation data and pitch data; The step of reversing the target beam vector according to the rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter at the original position includes: The target beam vector is horizontally rotated in the opposite direction according to the horizontal rotation data to obtain the transition beam vector. According to the pitch data, the beam corresponding to the transition beam vector is pitched in the opposite direction to obtain the original beam vector corresponding to the light spot emitted by the nth transmitter when it is in the original position. or According to the pitch data, the beam corresponding to the target beam vector is pitched in the opposite direction to obtain the transition beam vector; The beam corresponding to the transition beam vector is rotated horizontally in the opposite direction according to the horizontal rotation data to obtain the original beam vector corresponding to the light spot emitted by the nth emitter when it is in the original position.

5. The method as described in claim 2, characterized in that, Determining the true emission angle of the light spot emitted by the nth emitter at its original position based on the original beam vector includes: Obtain a lidar coordinate system that has a second mapping relationship with the spatial coordinate system; Based on the second mapping relationship, the original beam vector is transformed into the lidar coordinate system to obtain the true emission angle corresponding to the spot of the laser beam emitted by a single transmitter when it is in the original position. The actual emission angle includes the vertical angle of the laser spot and the horizontal angle of the laser spot. The vertical angle of the laser spot is the angle between the laser beam emitted by the nth transmitter in the original position and the horizontal plane of the lidar coordinate system. The horizontal angle of the laser spot is the angle between the laser beam emitted by the nth transmitter in the original position and the vertical plane of the lidar coordinate system.

6. The method as described in claim 5, characterized in that, The step of obtaining the lidar coordinate system that has a second mapping relationship with the spatial coordinate system includes: Obtain the established reference beam in the spatial coordinate system, and the lidar coordinate system containing the reference beam; The step of transforming the original beam vector to the lidar coordinate system based on the second mapping relationship to obtain the true emission angle corresponding to the spot of the laser beam emitted by a single transmitter at its original position includes: Determine the vector of the first beam corresponding to the first transmitter of the lidar, and the vector of the (n-1)th beam corresponding to the (n-1)th transmitter other than the first transmitter; The first beam is rotated to the reference beam to transform the vector of the first beam to the lidar coordinate system, thereby obtaining the true emission angle of the light spot emitted by the first transmitter in the lidar coordinate system. Calculate the rotation information generated by the first beam rotating to the reference beam, and rotate the vector of the (n-1)th beam according to the rotation information to transform the vector of the (n-1)th beam to the lidar coordinate system, so as to obtain the true emission angle of the light spot emitted by the (n-1)th transmitter in the lidar coordinate system.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: The actual emission angle is transmitted to the lidar, so that the nth transmitter of the lidar calculates the lidar detection data according to the actual emission angle when it is working.

8. A lidar calibration device, characterized in that, include: A rotation module is used to rotate the lidar so that the light spot emitted by the nth emitter of the lidar illuminates the detection area of ​​the calibration plate from its original position, and records the rotation data generated by the lidar rotating the nth emitter, where n is a positive integer; The determination module is used to determine the preset data parameters of the calibration board; The acquisition module is used to acquire the target spot image coordinates illuminated by the spot of the nth emitter on the detection area; The calculation module is used to obtain the actual emission angle of the light spot emitted by the nth transmitter when it is in the original position based on the preset data parameters of the calibration plate, the target light spot image coordinates, and the rotation data, wherein the actual emission angle is used to calibrate the set emission angle of the nth transmitter.

9. A computer device, characterized in that, The computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the lidar calibration method as described in any one of claims 1-7.

10. A storage medium, said storage medium being a computer-readable storage medium, said computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the lidar calibration method as described in any one of claims 1-7.

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