Wheel odometry and single-line lidar joint calibration method

Abstract

The present application relates to the technical field of intelligent logistics navigation laser radar, specifically a wheeled odometer and single-line laser radar joint calibration method, comprising: a calibration environment construction module for constructing a good calibration environment, before formally carrying out the joint calibration of the wheeled odometer and the single-line laser radar, the present application first focuses on the accurate calibration of the single-line laser radar internal parameter. This step is crucial because accurate laser radar internal parameters are the basis for subsequent calibration work. Through accurate internal parameter calibration, the present application can significantly reduce the overall calibration error caused by laser radar internal error, thereby improving the accuracy and reliability of the entire calibration system. This not only helps to improve the accuracy of vehicle navigation, but also provides more accurate data support for subsequent intelligent logistics tasks.

Description

Technical Field

[0001] This invention relates to the field of intelligent logistics navigation lidar technology, specifically a method for joint calibration of a wheeled odometer and a single-line lidar. Background Technology

[0002] In the intelligent logistics industry, the application of vehicle navigation LiDAR is becoming increasingly widespread, with single-line LiDAR and multi-line LiDAR being the two most common types. However, compared to multi-line LiDAR, single-line LiDAR has significant limitations in information acquisition. It can only acquire profile information of the surrounding environment, and therefore is inferior to multi-line LiDAR in terms of information acquisition volume, calibration difficulty, and calibration accuracy.

[0003] Single-line lidar is primarily used in scenarios involving planar motion. Key parameters requiring calibration include the x-coordinate, y-coordinate, and yaw angle. Among these parameters, the accuracy of the yaw angle has the most significant impact on vehicle motion precision. Therefore, in practical engineering applications, the focus is mainly on accurately calibrating the yaw angle, while the x and y coordinates are typically calibrated manually. However, this method struggles to guarantee consistent parking accuracy across multiple vehicles, thus affecting the overall performance and reliability of the intelligent logistics system.

[0004] In addition, although theoretically the x and y coordinates and heading angle yaw of a single-line lidar can be calibrated simultaneously using a wheel-based odometer method, in actual testing, the accuracy and consistency of the calibration results obtained by this method are poor and cannot meet the high standards required for industrial applications.

[0005] Furthermore, in most industrial applications, the calibration of wheeled odometers is typically performed entirely independently of the calibration of single-line lidar. Traditional calibration methods rely primarily on manual measurement using a measuring tape. While this method offers good accuracy, it is inefficient, time-consuming, labor-intensive, and prone to errors. This not only increases production costs but also extends project delivery cycles, impacting the overall project schedule and acceptance.

[0006] In summary, in order to improve the efficiency of vehicle factory testing, shorten the project delivery cycle, and speed up project acceptance, there is an urgent need for a solution that can simultaneously achieve accurate, fast, and simple calibration of wheeled odometers and single-line lidar. Summary of the Invention

[0007] (a) Purpose of the invention

[0008] In view of this, the purpose of this invention is to propose a joint calibration method for a wheeled odometer and a single-line lidar, which solves the problems mentioned in the background above.

[0009] (II) Technical Solution

[0010] A method for jointly calibrating a wheel-type odometer and a single-line lidar includes:

[0011] 1) A calibration environment construction module, used to build a good calibration environment to ensure the accuracy and reliability of the calibration process, wherein the calibration environment construction module further includes:

[0012] The single-line lidar intrinsic parameter calibration function ensures that the beam emitted by the laser emitter is parallel to the ground plane by precisely adjusting the installation angle of the lidar.

[0013] The flat ground selection function allows you to choose a flat, unobstructed ground as the calibration site.

[0014] 2): Mathematical model building module: Based on the physical conditions and geometric constraints of vehicle motion, a joint calibration mathematical model is built. This model can accurately describe the relationship between vehicle motion and sensor data.

[0015] 3) Raw sample data preprocessing module, used for preprocessing raw sample data, including steering wheel speed, steering wheel angle, raw laser point cloud, and mechanical constants. The raw sample data preprocessing module further includes:

[0016] The function of setting the steering wheel speed and angle to constant values ​​is available to quickly filter out abnormal data later.

[0017] The abnormal data filtering function is used to quickly filter out steering wheel speed, steering wheel angle, and laser point cloud sample data that exceed the threshold or deviate too much from the mean.

[0018] The data synchronization and interpolation processing function performs time synchronization and interpolation processing on the sample data after removing abnormal data, ensuring the integrity and continuity of the data.

[0019] 4): Parameter optimization calculation module. Through multiple iterative optimization calculations, the parameters of the wheel odometer and the single-line lidar are finally obtained. The parameters of the wheel odometer include the steering wheel zero bias and the travel motor reduction ratio. The parameters of the single-line lidar include the x-coordinate, y-coordinate and heading angle yaw.

[0020] 5): Iterative outlier filtering module: After each iteration calculation is completed, the calibration result of the single-line lidar is substituted into the target optimization function to calculate the error value of each group of sample data, and the sample data with large error values ​​are filtered and removed. Then the next iteration calculation is performed until the predetermined number of iterations or the error value meets the requirements is reached.

[0021] Preferably, the single-line lidar intrinsic parameter calibration function identifies the specific wavelength light emitted by the single-line lidar through a visual camera and adjusts the installation angle of the lidar until the emitted light is parallel to the ground plane.

[0022] A method for jointly calibrating a wheel-type odometer and a single-line lidar includes the following steps:

[0023] 1): Begin calibration and initialize the calibration program;

[0024] 2): Perform single-line lidar intrinsic parameter calibration to ensure that the beam emitted by the laser emitter is parallel to the ground plane, so as to improve the accuracy of the calibration results;

[0025] 3) Collect raw sample data, including steering wheel speed, steering wheel angle, point cloud data of single-line lidar, and mechanical constants, etc.

[0026] 4) Preprocess the original sample data, including filtering out outliers, performing time synchronization and interpolation, to ensure the integrity and continuity of the data;

[0027] 5): Perform joint calibration of wheeled odometer and single-line lidar, and establish a mathematical model to describe the relationship between vehicle motion and sensor data;

[0028] 6): Determine if there are any anomalies during the iteration process. If there are no anomalies, proceed to step g); if there are anomalies, return to step 5) to continue iterative optimization.

[0029] 7) Output calibration results, including parameters of the wheel odometer (such as steering wheel zero bias, travel motor reduction ratio) and parameters of the single-line lidar (such as x-coordinate, y-coordinate and heading angle yaw).

[0030] 8): Calibration complete.

[0031] Preferably, the single-line lidar intrinsic parameter calibration in step 2) is achieved by parking the vehicle on a level surface, using a vision camera to identify the specific wavelength of light emitted by the single-line lidar, and adjusting the installation angle of the lidar until the emitted light is parallel to the ground plane.

[0032] Preferably, the preprocessing of raw sample data in step 4) further includes setting the steering wheel speed and angle to constant values ​​in order to reduce external interference when collecting sample data and to quickly filter out abnormal data.

[0033] Preferably, the calibration formula for wheel-type odometers is as follows: Because the single-line lidar and the vehicle form a rigid body structure, the angular velocity of any point on the vehicle relative to its center of rotation is equal, defined as follows: Indicates the time period of the wheel odometer [ , Changes in heading angle within ] This indicates that the single-line lidar operates within a certain time period. , The change in heading angle within the range of ] holds the following equation: During the time period [ , [Inside, define] From the vehicle's kinematic model, we can conclude that: in, Indicates the speed of the walking motor, Indicates the radius of the steering wheel, Represents the horizontal coordinate of the steering wheel, Indicates the reduction ratio of the walking motor, Indicates the steering wheel angle, This indicates the zero bias value of the steering wheel. and All of these are variables to be determined; the rest are known variables.

[0034] Therefore, the calibration equation for the wheel odometer is: in, , , Using the least squares algorithm, we can obtain... b, and thus have , .

[0035] Preferably, the calibration formula for a single-line lidar includes: based on the zero offset value of the steering wheel obtained from calibration. and the reduction ratio of the walking motor The calibrated wheel odometer was calculated. This provides accurate and reliable data for calibrating single-line lidar.

[0036] The displacement relationship between the wheel-type odometer and the single-line lidar is as follows: in, , Given a constant coefficient matrix, establish the following objective function: in, , and All are known constant coefficient matrices. The objective function is optimized through iterative optimization. The value corresponding to the minimum The pose of a single-line lidar can then be obtained. .

[0037] As can be seen from the above technical solutions, this application has the following beneficial effects:

[0038] Before formally calibrating the wheeled odometer and single-line LiDAR, this invention first focuses on the precise calibration of the single-line LiDAR's intrinsic parameters. This step is crucial because accurate LiDAR intrinsic parameters are the foundation for subsequent calibration work. Through precise intrinsic parameter calibration, this invention can significantly reduce the overall calibration error caused by the LiDAR's internal errors, thereby improving the accuracy and reliability of the entire calibration system. This not only helps improve the accuracy of vehicle navigation but also provides more precise data support for subsequent intelligent logistics tasks.

[0039] This invention introduces a preprocessing step for the raw sample data during the calibration process. By filtering and denoising the collected raw data, this invention can effectively eliminate outliers and noise interference in the data, thereby ensuring that the data used in the calibration process is more authentic and reliable. This preprocessing step not only improves the stability of the calibration results but also helps reduce calibration errors caused by data issues.

[0040] This invention utilizes innovative technology to simultaneously calibrate wheeled odometers and single-line lidar systems offline or online. This capability not only significantly reduces calibration time but also simplifies the calibration process, making it more efficient and convenient. This is of great significance for improving vehicle factory testing efficiency and shortening project delivery cycles.

[0041] This invention also incorporates an iterative outlier filtering mechanism. At the end of each iteration, the system automatically removes outliers and performs the next iteration based on the remaining data. This mechanism continuously approaches the optimal solution, thereby further reducing calibration errors. Through multiple iterative optimizations, this invention ensures the stability and consistency of calibration results, providing more reliable data support for subsequent intelligent logistics tasks. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the original sample data before screening in this invention;

[0043] Figure 2 This is a schematic diagram of the sample data after screening in this invention;

[0044] Figure 3 This is a schematic diagram of the method architecture of the present invention. Detailed Implementation

[0045] The following description is exemplary in nature and is not intended to limit the scope, application, or use of this disclosure. It should be understood that in all these figures, the same or similar reference numerals indicate the same or similar parts and features. The figures are merely schematic representations of the concept and principles of embodiments of this disclosure and do not necessarily show the specific dimensions and scale of the various embodiments of this disclosure. Certain details or structures of embodiments of this disclosure may be exaggerated in particular portions of certain figures.

[0046] Please see Figure 1-3 One embodiment provided by the present invention:

[0047] A method for jointly calibrating a wheel-type odometer and a single-line lidar includes:

[0048] 1) Calibration environment construction module, used to build a good calibration environment to ensure the accuracy and reliability of the calibration process. The calibration environment construction module further includes:

[0049] The single-line lidar intrinsic parameter calibration function ensures that the beam emitted by the laser emitter is parallel to the ground plane by precisely adjusting the installation angle of the lidar.

[0050] The flat ground selection function allows you to choose a flat, unobstructed ground as the calibration site.

[0051] 2): Mathematical model building module: Based on the physical conditions and geometric constraints of vehicle motion, a joint calibration mathematical model is built. This model can accurately describe the relationship between vehicle motion and sensor data.

[0052] 3) Raw sample data preprocessing module, used for preprocessing raw sample data, including steering wheel speed, steering wheel angle, raw laser point cloud, and mechanical constants. The raw sample data preprocessing module further includes:

[0053] The function of setting the steering wheel speed and angle to constant values ​​is available to quickly filter out abnormal data later.

[0054] The abnormal data filtering function is used to quickly filter out steering wheel speed, steering wheel angle, and laser point cloud sample data that exceed the threshold or deviate too much from the mean.

[0055] The data synchronization and interpolation processing function performs time synchronization and interpolation processing on the sample data after removing abnormal data, ensuring the integrity and continuity of the data.

[0056] 4): Parameter optimization calculation module. Through multiple iterative optimization calculations, the parameters of the wheel odometer and the single-line lidar are finally obtained. The parameters of the wheel odometer include the steering wheel zero bias and the travel motor reduction ratio. The parameters of the single-line lidar include the x-coordinate, y-coordinate and heading angle yaw.

[0057] 5): Iterative outlier filtering module: After each iteration calculation is completed, the calibration result of the single-line lidar is substituted into the target optimization function to calculate the error value of each group of sample data, and the sample data with large error values ​​are filtered and removed. Then the next iteration calculation is performed until the predetermined number of iterations or the error value meets the requirements is reached.

[0058] Furthermore, the single-line lidar intrinsic parameter calibration function identifies the specific wavelength of light emitted by the single-line lidar through a visual camera and adjusts the installation angle of the lidar until the emitted light is parallel to the ground plane.

[0059] A method for jointly calibrating a wheel-type odometer and a single-line lidar includes the following steps:

[0060] 1): Begin calibration and initialize the calibration program;

[0061] 2) Perform single-line lidar intrinsic parameter calibration to ensure that the beam emitted by the laser emitter is parallel to the ground plane, thereby improving the accuracy of the calibration results. If the intrinsic parameters of the single-line lidar are inaccurate, the recorded original laser point cloud will be inaccurate, thus reducing the accuracy of the calibration results. To ensure that the beam emitted by the laser emitter is parallel to the ground plane, the vehicle is manually parked on a level surface before calibration begins. Using a vision camera that can identify the characteristics of the wavelength of light emitted by the single-line lidar, the installation angle of the target lidar is adjusted until the emitted light is parallel to the ground plane.

[0062] 3) Collect raw sample data, including steering wheel speed, steering wheel angle, point cloud data of single-line lidar, and mechanical constants, etc.

[0063] 4) Preprocessing of the raw sample data includes filtering out outliers, time synchronization, and interpolation to ensure data integrity and continuity. The raw sample data includes steering wheel speed, steering wheel angle, raw laser point cloud, and mechanical constants. To reduce the cumulative error of the wheeled odometer and facilitate accurate filtering of outlier data, the steering wheel speed and angle are set to constant values. Therefore, after data collection, steering wheel speed, steering wheel angle, and laser point cloud data exceeding thresholds or deviating significantly from the mean can be quickly filtered out. Figure 1 , Figure 2 As shown, time synchronization and interpolation of sample data can only be performed after outlier sample data has been removed.

[0064] 5): Perform joint calibration of wheeled odometer and single-line lidar, and establish a mathematical model to describe the relationship between vehicle motion and sensor data;

[0065] 6): Determine if there are any anomalies during the iteration process. If there are no anomalies, proceed to step g); if there are anomalies, return to step 5) to continue iterative optimization.

[0066] 7) Output calibration results, including parameters of the wheel odometer (such as steering wheel zero bias, travel motor reduction ratio) and parameters of the single-line lidar (such as x-coordinate, y-coordinate and heading angle yaw).

[0067] 8): Calibration complete.

[0068] Furthermore, the single-line lidar intrinsic parameter calibration in step 2) is achieved by parking the vehicle on a level surface, using a vision camera to identify the specific wavelength of light emitted by the single-line lidar, and adjusting the installation angle of the lidar until the emitted light is parallel to the ground plane.

[0069] Furthermore, the raw sample data preprocessing in step 4) also includes setting the steering wheel speed and angle to constant values ​​in order to reduce external interference when collecting sample data and to quickly filter out abnormal data.

[0070] Furthermore, this includes the calibration formula for wheeled odometers: because the single-line lidar and the vehicle form a rigid body structure, the angular velocity of any point on the vehicle relative to its center of rotation is equal, defined as follows: Indicates the time period of the wheel odometer [ , Changes in heading angle within ] This indicates that the single-line lidar operates within a certain time period. , The change in heading angle within the range of ] holds the following equation: During the time period [ , [Inside, define] From the vehicle's kinematic model, we can conclude that: in, Indicates the speed of the walking motor, Indicates the radius of the steering wheel, Represents the horizontal coordinate of the steering wheel, Indicates the reduction ratio of the walking motor, Indicates the steering wheel angle, This indicates the zero bias value of the steering wheel. and All of these are variables to be determined; the rest are known variables.

[0071] Therefore, the calibration equation for the wheel odometer is: in, , , Using the least squares algorithm, we can obtain... b, and thus have , .

[0072] Preferably, the calibration formula for a single-line lidar includes: based on the zero offset value of the steering wheel obtained from calibration. and the reduction ratio of the walking motor The calibrated wheel odometer was calculated. This provides accurate and reliable data for calibrating single-line lidar.

[0073] The displacement relationship between the wheel-type odometer and the single-line lidar is as follows: in, , Given a constant coefficient matrix, establish the following objective function: in, , and All are known constant coefficient matrices. The objective function is optimized through iterative optimization. The value corresponding to the minimum The pose of a single-line lidar can then be obtained. .

[0074] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for joint calibration of a wheel-type odometer and a single-line lidar, characterized in that, include: 1) A calibration environment construction module, used to build a good calibration environment to ensure the accuracy and reliability of the calibration process, wherein the calibration environment construction module further includes: The single-line lidar intrinsic parameter calibration function ensures that the beam emitted by the laser emitter is parallel to the ground plane by precisely adjusting the installation angle of the lidar. The flat ground selection function allows you to choose a flat, unobstructed ground as the calibration site. 2) Mathematical Model Establishment Module: Based on the physical conditions and geometric constraints of vehicle motion, a joint calibration mathematical model is established. This model accurately describes the relationship between vehicle motion and sensor data, including the wheel odometer calibration formula. Because the single-line lidar and the vehicle form a rigid body structure, the angular velocity of any point on the vehicle relative to its center of rotation is equal. (Definition...) Indicates the time period of the wheel odometer [ , Changes in heading angle within ] This indicates that the single-line lidar operates within a certain time period. , The change in heading angle within the range of ] holds the following equation: ； During the time period [ , [Inside, define] From the vehicle's kinematic model, we can conclude that: ； in, Indicates the speed of the walking motor, Indicates the radius of the steering wheel, Represents the horizontal coordinate of the steering wheel, Indicates the reduction ratio of the walking motor, Indicates the steering wheel angle, This indicates the zero bias value of the steering wheel. and All variables are unknown; the rest are known variables. Therefore, the calibration equation for the wheel odometer is: ； in, , , Using the least squares algorithm, we can obtain... b, and thus have , ; Including the single-line lidar calibration formula: based on the zero offset value of the steering wheel obtained from the calibration. and the reduction ratio of the walking motor The calibrated wheel odometer was calculated. This provides accurate and reliable data for calibrating single-line lidar. The displacement relationship between the wheel-type odometer and the single-line lidar is as follows: ; in, This indicates the coordinates of a single-line lidar in the vehicle coordinate system. , Given a matrix with constant coefficients, its mathematical expression is as follows: ； Establish the following objective optimization function: ； in, , and All are known constant coefficient matrices. The objective function is optimized through iterative optimization. The value corresponding to the minimum The pose of a single-line lidar can then be obtained. ; and The mathematical expression is as follows: ； ； ； ； ； During the time period [ , ]Inside, and These represent the coordinates of a single-line lidar in its own coordinate system. axis, Change in displacement along the axial direction: ； ； ； ； 3) Raw sample data preprocessing module, used for preprocessing raw sample data, including steering wheel speed, steering wheel angle, raw laser point cloud, and mechanical constants. The raw sample data preprocessing module further includes: The function of setting the steering wheel speed and angle to constant values ​​is available to quickly filter out abnormal data later. The abnormal data filtering function is used to quickly filter out steering wheel speed, steering wheel angle, and laser point cloud sample data that exceed the threshold or deviate too much from the mean. The data synchronization and interpolation processing function performs time synchronization and interpolation processing on the sample data after removing abnormal data, ensuring the integrity and continuity of the data. 4): Parameter optimization calculation module. Through multiple iterative optimization calculations, the parameters of the wheel odometer and the single-line lidar are finally obtained. The parameters of the wheel odometer include the steering wheel zero bias and the travel motor reduction ratio. The parameters of the single-line lidar include the x-coordinate, y-coordinate and heading angle yaw. 5): Iterative outlier filtering module: After each iteration calculation is completed, the calibration result of the single-line lidar is substituted into the target optimization function to calculate the error value of each group of sample data, and the sample data with large error values ​​are filtered and removed. Then the next iteration calculation is performed until the predetermined number of iterations or the error value meets the requirements is reached.

2. The method for joint calibration of a wheel-type odometer and a single-line lidar according to claim 1, characterized in that: The single-line lidar intrinsic parameter calibration function identifies the specific wavelength of light emitted by the single-line lidar through a visual camera and adjusts the installation angle of the lidar until the emitted light is parallel to the ground plane.

3. The method for joint calibration of a wheel-type odometer and a single-line lidar according to claim 1, characterized in that: Includes the following steps: 1): Begin calibration and initialize the calibration program; 2): Perform single-line lidar intrinsic parameter calibration to ensure that the beam emitted by the laser emitter is parallel to the ground plane, so as to improve the accuracy of the calibration results; 3) Collect raw sample data, which includes steering wheel speed, steering wheel angle, point cloud data of single-line lidar, and mechanical constants; 4) Preprocess the original sample data, including filtering out outliers, performing time synchronization and interpolation, to ensure the integrity and continuity of the data; 5): Perform joint calibration of wheeled odometer and single-line lidar, and establish a mathematical model to describe the relationship between vehicle motion and sensor data; 6): Determine if there are any anomalies during the iteration process. If there are no anomalies, proceed to step g); if there are anomalies, return to step 5) to continue iterative optimization. 7) Output calibration results, including parameters of the wheel odometer, steering wheel zero bias, travel motor reduction ratio and single-line lidar parameters, namely x-coordinate, y-coordinate and heading angle yaw; 8): Calibration complete.

4. The method for joint calibration of a wheel-type odometer and a single-line lidar according to claim 3, characterized in that: The single-line lidar intrinsic parameter calibration in step 2) is achieved by parking the vehicle on a level surface, using a vision camera to identify the specific wavelength of light emitted by the single-line lidar, and adjusting the installation angle of the lidar until the emitted light is parallel to the ground plane.

5. The method for joint calibration of a wheel-type odometer and a single-line lidar according to claim 3, characterized in that: The preprocessing of raw sample data in step 4) also includes setting the steering wheel speed and angle to constant values ​​in order to reduce external interference when collecting sample data and to quickly filter out abnormal data.

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