Wheel type odometer and single-line laser radar combined calibration method

Abstract

The invention relates to the technical field of intelligent logistics navigation laser radars, in particular to a wheel type odometer and single-line laser radar combined calibration method, which comprises a calibration environment construction module used for constructing a good calibration environment. The method firstly focuses on the accurate calibration of the internal reference of the single-line laser radar. The step is crucial because the accurate internal reference of the laser radar is the basis of the subsequent calibration work. Through accurate internal reference calibration, the overall calibration error caused by the internal error of the laser radar can be remarkably reduced, and the precision and reliability of the whole calibration system are improved. The accuracy of vehicle navigation can be improved, and more accurate data support can be provided for subsequent intelligent logistics tasks.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent logistics navigation laser radar, and specifically to a joint calibration method of a wheel odometer and a single-line laser radar. Background Art

[0002] In the intelligent logistics industry, the application of vehicle navigation laser radar is becoming more and more widespread, among which single-line laser radar and multi-line laser radar are the two most common types. However, compared with multi-line laser radar, single-line laser radar has obvious limitations in obtaining information. It can only obtain profile information of the surrounding environment, so it is inferior to multi-line laser radar in terms of information acquisition, calibration difficulty and calibration accuracy.

[0003] Single-line laser radar is mainly used in planar motion scenarios, and the key parameters that need to be calibrated include the x-coordinate, y-coordinate, and heading angle yaw. Among these parameters, the accuracy of the heading angle yaw has the most significant impact on the vehicle's motion accuracy. Therefore, in actual engineering applications, the main focus is on accurately calibrating the heading angle yaw, while the x- and y-coordinates are usually calibrated by manual adjustment. However, this method makes it difficult to ensure the consistency of parking accuracy for multiple vehicles, thus affecting the overall performance and reliability of the intelligent logistics system.

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

[0005] In addition, in most industrial applications, the calibration of wheel odometers is usually performed completely independently of the calibration of single-line lidars. Traditional calibration methods mainly rely on manual measurement and calibration using a tape measure. Although this method performs well in terms of accuracy, it is inefficient, time-consuming, labor-intensive, and prone to errors. This not only increases production costs, but also prolongs project delivery cycles, affecting the overall progress and acceptance of the project.

[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 easy calibration of wheel odometers and single-line lidars. Summary of the invention

[0007] (I) Purpose of the invention

[0008] In view of this, the purpose of the present invention is to propose a joint calibration method of a wheel odometer and a single-line laser radar to solve the problems raised in the above background.

[0009] (II) Technical solution

[0010] A method for joint calibration of a wheel odometer and a single-line laser radar, comprising:

[0011] 1): A calibration environment construction module is used to construct a good calibration environment to ensure the accuracy and reliability of the calibration process. The calibration environment construction module further includes:

[0012] The single-line laser radar internal calibration function ensures that the light beam emitted by the laser transmitter is parallel to the ground plane by accurately adjusting the installation angle of the radar;

[0013] Flat ground selection function: select a flat, unobstructed ground as the calibration site;

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

[0015] 3): A raw sample data preprocessing module is used for preprocessing raw sample data, wherein the raw sample data includes 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 ​​can help to quickly filter out abnormal data later;

[0017] Abnormal data screening function, used to quickly screen 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] Data synchronization and interpolation processing function: after removing abnormal data, time synchronization and interpolation processing of sample data are performed to ensure data integrity and continuity;

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

[0020] 5): Iterative outlier screening module. After each iterative calculation is completed, the calibration result of the single-line laser radar is substituted into the target optimization function, the error value of each group of sample data is calculated, and the sample data with large error values ​​are screened and eliminated. Then the next iterative calculation is performed until the predetermined number of iterations is reached or the error value meets the requirements.

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

[0022] A method for joint calibration of a wheel odometer and a single-line laser radar comprises the following steps:

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

[0024] 2): Perform single-line lidar internal calibration to ensure that the light beam emitted by the laser transmitter is parallel to the ground plane to improve the accuracy of the calibration results;

[0025] 3): Collecting original sample data, which includes steering wheel speed, steering wheel angle, point cloud data of single-line laser radar, and mechanical constants;

[0026] 4): Preprocess the original sample data, including screening and removing abnormal data, performing time synchronization and interpolation processing to ensure the integrity and continuity of the data;

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

[0028] 6): Determine whether there is an abnormality in the iterative process. If there is no abnormality, execute step g); if there is an abnormality, return to step 5) to continue iterative optimization;

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

[0030] 8): Calibration is completed.

[0031] Preferably, the single-line laser radar internal parameter calibration in step 2) is achieved by parking the vehicle on horizontal ground, using a visual camera to identify the specific wavelength light emitted by the single-line laser radar, and adjusting the installation angle of the radar until the light emitted by it is parallel to the ground plane.

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

[0033] Preferably, the wheel odometer calibration formula is included: Since the single-line laser radar and the vehicle form a rigid structure, the angular velocity of any point on the vehicle relative to its rotation center is equal, and the definition is represents the wheel odometer in the time period [t k-1 ,t k ] within the heading angle change, Represents the single-line laser radar in the time period [t k-1 ,t k ], the following equation holds true:

[0034]

[0035] In the time period [t k-1 ,t k ], define Δt = t k -t k-1 , from the kinematic model of the vehicle, we can get:

[0036]

[0037] Among them, σ represents the speed of the travel motor, r represents the radius of the steering wheel, x represents the horizontal coordinate of the steering wheel, ξ represents the reduction ratio of the travel motor, α k represents the steering wheel angle, α off Indicates the zero bias value of the steering wheel, α k and α off are all variables to be determined, and the rest are known variables.

[0038] Therefore, the calibration equation of the wheel odometer is:

[0039] Ax=b

[0040] in, Using the least squares algorithm, we can get x = [x1 x2] T =(ATA) -1 A T b, and then there is

[0041] Preferably, a single-line laser radar calibration formula is included: According to the steering wheel zero bias value α obtained by calibration off and the travel motor reduction ratio ξ, and calculate the calibrated wheel odometer.

[0042] Provide accurate and reliable data for calibrating single-line laser radar.

[0043] From weight 6, we can know that the displacement relationship between the wheel odometer and the single-line laser radar is:

[0044]

[0045] Among them, R(l θ ), For a known constant coefficient matrix, establish the following objective optimization function:

[0046]

[0047] in, and All of them are known constant coefficient matrices. Through iterative optimization, the target optimization function The value corresponding to the minimum The position and posture of the single-line laser radar can be obtained as l = [l x l y l θ ] T .

[0048] It can be seen from the above technical solutions that the present application has the following beneficial effects:

[0049] 1. Before the joint calibration of the wheel odometer and the single-line laser radar is officially carried out, the present invention first focuses on the precise calibration of the internal parameters of the single-line laser radar. This step is crucial because accurate internal parameters of the laser radar are the basis for subsequent calibration work. Through precise internal parameter calibration, the present invention can significantly reduce the overall calibration error caused by the internal error of the laser radar, 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.

[0050] 2. The invention introduces a preprocessing step of the original sample data during the calibration process. By filtering and denoising the collected original data, the invention can effectively eliminate outliers and noise interference in the data, thereby ensuring that the data based on the calibration process is more real and reliable. The introduction of this preprocessing step not only improves the stability of the calibration results, but also helps to reduce the calibration errors caused by data problems.

[0051] 3. This invention uses innovative technical means to achieve the function of calibrating wheel odometers and single-line laser radars offline or online at the same time. This function not only greatly shortens the calibration time, but also simplifies the calibration steps, making the calibration process more efficient and convenient. This is of great significance for improving the efficiency of vehicle factory testing and shortening project delivery cycles.

[0052] 4. The invention also provides a screening mechanism for iterative outliers. At the end of each iteration, the system automatically removes outliers and performs the next iterative optimization based on the remaining data. This mechanism can continuously approach the optimal solution, thereby further reducing the calibration error. Through multiple iterative optimizations, the present invention can ensure the stability and consistency of the calibration results, and provide more reliable data guarantee for subsequent intelligent logistics tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the original sample data before screening in the present invention;

[0054] Figure 2 This is a schematic diagram of sample data after screening by the present invention;

[0055] Figure 3 The figure is a schematic diagram of the flow chart of the method structure of the present invention. DETAILED DESCRIPTION

[0056] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, and use. It should be understood that in all of these figures, the same or similar reference numerals indicate the same or similar parts and features. The various drawings only schematically represent the concepts and principles of the embodiments of the present disclosure, and do not necessarily show the specific dimensions and proportions of the various embodiments of the present disclosure. Specific parts in specific drawings may be exaggerated to illustrate the relevant details or structures of the embodiments of the present disclosure.

[0057] See also Figure 1-3 , an embodiment provided by the present invention:

[0058] A method for joint calibration of a wheel odometer and a single-line laser radar, comprising:

[0059] 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:

[0060] The single-line laser radar internal calibration function ensures that the light beam emitted by the laser transmitter is parallel to the ground plane by accurately adjusting the installation angle of the radar;

[0061] Flat ground selection function: select a flat, unobstructed ground as the calibration site;

[0062] 2): Mathematical model building module, which builds a joint calibration mathematical model based on the physical conditions and geometric constraints of vehicle motion. This model can accurately describe the relationship between vehicle motion and sensor data;

[0063] 3): The raw sample data preprocessing module is used for preprocessing the raw sample data. The raw sample data includes the steering wheel speed, steering wheel angle, raw laser point cloud and mechanical constants. The raw sample data preprocessing module further includes:

[0064] The function of setting the steering wheel speed and angle to constant values ​​can help to quickly filter out abnormal data later;

[0065] Abnormal data screening function, used to quickly screen out steering wheel speed, steering wheel angle, and laser point cloud sample data that exceed the threshold or deviate too much from the mean;

[0066] Data synchronization and interpolation processing function: after removing abnormal data, time synchronization and interpolation processing of sample data are performed to ensure data integrity and continuity;

[0067] 4): Parameter optimization calculation module, through multiple iterative optimization calculations, finally obtains the parameters of the wheel odometer and the single-line laser radar. The parameters of the wheel odometer include the steering wheel zero bias and the travel motor reduction ratio. The parameters of the single-line laser radar include the x-coordinate, y-coordinate and heading angle yaw.

[0068] 5): Iterative outlier screening module. After each iterative calculation is completed, the calibration result of the single-line laser radar is substituted into the target optimization function, the error value of each group of sample data is calculated, and the sample data with large error values ​​are screened and eliminated. Then the next iterative calculation is performed until the predetermined number of iterations is reached or the error value meets the requirements.

[0069] Furthermore, the single-line laser radar internal calibration function uses a visual camera to identify the specific wavelength of light emitted by the single-line laser radar, and adjusts the installation angle of the radar until the light it emits is parallel to the ground plane.

[0070] A method for joint calibration of a wheel odometer and a single-line laser radar comprises the following steps:

[0071] 1): Start calibration and initialize the calibration program;

[0072] 2): Perform internal calibration of the single-line laser radar to ensure that the light beam emitted by the laser transmitter is parallel to the ground plane to improve the accuracy of the calibration results. If the internal parameters of the single-line laser radar are inaccurate, the recorded original laser point cloud will be inaccurate, thereby reducing the accuracy of the calibration results. In order to ensure that the light beam emitted by the laser transmitter is parallel to the ground plane, the vehicle is manually parked on a horizontal ground before starting the calibration. The visual camera can identify the characteristics of the wavelength light emitted by the single-line laser radar, and the installation angle of the target radar is adjusted until the light emitted by it is parallel to the ground plane;

[0073] 3): Collect original sample data, including steering wheel speed, steering wheel angle, point cloud data of single-line laser radar, and mechanical constants;

[0074] 4): Preprocess the original sample data, including filtering out abnormal data, performing time synchronization and interpolation processing to ensure the integrity and continuity of the data. The original sample data includes steering wheel speed, steering wheel angle, original laser point cloud and mechanical constants. In order to reduce the cumulative error of the wheel odometer and facilitate accurate screening of abnormal sample data, the steering wheel speed and angle are set to constant values. After the sample data is collected, the steering wheel speed, steering wheel angle and laser point cloud sample data that exceed the threshold or deviate too much from the mean can be quickly screened out, such as Figure 1 , Figure 2 As shown. After the abnormal sample data is removed, the time synchronization and interpolation processing of the sample data can be performed;

[0075] 5): Perform joint calibration of wheel odometer and single-line lidar, and establish a mathematical model to describe the relationship between vehicle motion and sensor data;

[0076] 6): Determine whether there is an abnormality in the iterative process. If there is no abnormality, execute step g); if there is an abnormality, return to step 5) to continue iterative optimization;

[0077] 7): Output calibration results, including parameters of wheel odometer (such as steering wheel zero bias, travel motor reduction ratio) and parameters of single-line laser radar (such as x-coordinate, y-coordinate and heading angle yaw);

[0078] 8): Calibration is completed.

[0079] Furthermore, the single-line laser radar internal parameter calibration in step 2) is achieved by parking the vehicle on horizontal ground, using a visual camera to identify the specific wavelength light emitted by the single-line laser radar, and adjusting the installation angle of the radar until the light emitted by it is parallel to the ground plane.

[0080] Furthermore, the raw sample data preprocessing in step 4) also includes setting the steering wheel speed and angle to constant values ​​so as to reduce external interference when collecting sample data and quickly filter out abnormal data.

[0081] Furthermore, the wheel odometer calibration formula is included: Since the single-line laser radar and the vehicle form a rigid structure, the angular velocity of any point on the vehicle relative to its rotation center is equal, and the definition is represents the wheel odometer in the time period [t k-1 ,t k ] within the heading angle change, Represents the single-line laser radar in the time period [t k-1 ,t k ], the following equation holds true:

[0082]

[0083] In the time period [t k-1 ,t k ], define Δt = t k -t k-1 , from the kinematic model of the vehicle, we can get:

[0084]

[0085] Among them, σ represents the speed of the travel motor, r represents the radius of the steering wheel, x represents the horizontal coordinate of the steering wheel, ξ represents the reduction ratio of the travel motor, α k represents the steering wheel angle, α off Indicates the zero bias value of the steering wheel, α k and α off are all variables to be determined, and the rest are known variables.

[0086] Therefore, the calibration equation of the wheel odometer is:

[0087] Ax=b

[0088] in, Using the least squares algorithm, we can get x = [x1 x2] T =(ATA) -1 A T b, and then there is

[0089] Furthermore, the single-line laser radar calibration formula is included: According to the steering wheel zero bias value α obtained by calibration off and the travel motor reduction ratio ξ, and calculate the calibrated wheel odometer. Provide accurate and reliable data for calibrating single-line laser radar.

[0090] From weight 6, we can know that the displacement relationship between the wheel odometer and the single-line laser radar is:

[0091]

[0092] Among them, R(l θ ), For a known constant coefficient matrix, establish the following objective optimization function:

[0093]

[0094] in, and All of them are known constant coefficient matrices. Through iterative optimization, the target optimization function The value corresponding to the minimum The position and posture of the single-line laser radar can be obtained as l = [l x ly l θ ] T .

[0095] It will be apparent to those skilled in the art that the 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 the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A joint calibration method of a wheel odometer and a single-line laser radar, characterized in that: include: 1): A calibration environment construction module is used to construct a good calibration environment to ensure the accuracy and reliability of the calibration process. The calibration environment construction module further includes: The single-line laser radar internal calibration function ensures that the light beam emitted by the laser transmitter is parallel to the ground plane by accurately adjusting the installation angle of the radar; Flat ground selection function: select a flat, unobstructed ground as the calibration site; 2): Mathematical model building module, which builds a joint calibration mathematical model based on the physical conditions and geometric constraints of vehicle motion. This model can accurately describe the relationship between vehicle motion and sensor data; 3): A raw sample data preprocessing module is used for preprocessing raw sample data, wherein the raw sample data includes 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 ​​can help to quickly filter out abnormal data later; Abnormal data screening function, used to quickly screen out steering wheel speed, steering wheel angle, and laser point cloud sample data that exceed the threshold or deviate too much from the mean; Data synchronization and interpolation processing function: after removing abnormal data, time synchronization and interpolation processing of sample data are performed to ensure data integrity and continuity; 4): Parameter optimization calculation module, through multiple iterative optimization calculations, finally obtains the parameters of the wheel odometer and the single-line laser radar. The parameters of the wheel odometer include the steering wheel zero bias and the travel motor reduction ratio, and the parameters of the single-line laser radar include the x-coordinate, the y-coordinate and the heading angle yaw. 5): Iterative outlier screening module. After each iterative calculation is completed, the calibration result of the single-line laser radar is substituted into the target optimization function, the error value of each group of sample data is calculated, and the sample data with large error values ​​are screened and eliminated. Then the next iterative calculation is performed until the predetermined number of iterations is reached or the error value meets the requirements.

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

3. The combined calibration method of a wheel odometer and a single-line laser radar according to claim 1 is characterized in that: The following steps are involved: 1): Start calibration and initialize the calibration program; 2): Perform single-line lidar internal calibration to ensure that the light beam emitted by the laser transmitter is parallel to the ground plane to improve the accuracy of the calibration results; 3): Collecting original sample data, which includes steering wheel speed, steering wheel angle, point cloud data of single-line laser radar, and mechanical constants; 4): Preprocess the original sample data, including screening and removing abnormal data, performing time synchronization and interpolation processing to ensure the integrity and continuity of the data; 5): Perform joint calibration of wheel odometer and single-line lidar, and establish a mathematical model to describe the relationship between vehicle motion and sensor data; 6): Determine whether there is an abnormality in the iterative process. If there is no abnormality, execute step g); if there is an abnormality, return to step 5) to continue iterative optimization; 7): Output calibration results, including parameters of wheel odometer (such as steering wheel zero bias, travel motor reduction ratio) and parameters of single-line laser radar (such as x-coordinate, y-coordinate and heading angle yaw); 8): Calibration is completed.

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

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

6. The combined calibration method of a wheel odometer and a single-line laser radar according to claim 1 is characterized in that: Including the wheel odometer calibration formula: Since the single-line laser radar and the vehicle form a rigid structure, the angular velocity of any point on the vehicle relative to its rotation center is equal, and the definition represents the wheel odometer in the time period [t k-1 ,t k ] within the heading angle change, Represents the single-line laser radar in the time period [t k-1 ,t k ], the following equation holds true: In the time period [t k-1 ,t k ], define Δt = t k -t k-1 , it can be known from the kinematic model of the vehicle that have to: Among them, σ represents the speed of the travel motor, r represents the radius of the steering wheel, x represents the horizontal coordinate of the steering wheel, ξ represents the reduction ratio of the travel motor, α k represents the steering wheel angle, α off Indicates the zero bias value of the steering wheel, α k and α off are all variables to be determined, and the rest are known variables. Therefore, the calibration equation of the wheel odometer is: Ax=b in, Using the least squares algorithm, we can get x = [x1 x2] T =(A T A) -1 A T b, and then there is 7. The combined calibration method of a wheel odometer and a single-line laser radar according to claim 1 is characterized in that: Including the single-line laser radar calibration formula: According to the calibration obtained steering wheel zero bias value α off and the travel motor reduction ratio ξ, and calculate the calibrated wheel odometer. Provide accurate and reliable data for calibrating single-line laser radar. From weight 6, we can know that the displacement relationship between the wheel odometer and the single-line laser radar is: Among them, R(l θ ), For a known constant coefficient matrix, establish the following objective optimization function: in, and All of them are known constant coefficient matrices. Through iterative optimization, the target optimization function The value corresponding to the minimum The position and posture of the single-line laser radar can be obtained as l = [l x l y l θ ] T .

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