Calibration Method for Laser Positioning System with Self-Organizing Network Mechanism

Abstract

The present invention discloses a calibration method for a laser positioning system with a self-organizing network mechanism, which is specifically implemented according to the following steps: Step 1, install a marking point on each laser emission station and calibrate the coordinates of each marking point in the local coordinate system of the emission station; Step 2, after arranging the laser emission stations at the measurement site, measure the distance between every two marking points; Step 3, the laser emission stations measure the marking points with each other, and calibrate the laser positioning system in combination with the distance between every two marking points; Step 4, after the laser positioning system is calibrated to form a measurement network, when a new laser emission station is added to the system, the original measurement network measures the marking points of the new emission station to achieve self-organizing network. The present invention only needs to fix a marking point on each laser emission station, and the calibration can be completed by measuring the distance between the marking points. After the calibration is completed, when a new laser emission station is added, the calibration of the new laser emission station can be completed through the self-organizing network mechanism, improving the calibration efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic information calibration methods, and particularly relates to a calibration method for a laser positioning system with a self-organizing network mechanism. Background Art

[0002] A laser positioning system is a distributed optoelectronic scanning positioning system for large-scale industrial measurement, which has the advantages of high measurement accuracy, high efficiency, large range, and real-time multi-target measurement. When the system works, the local coordinate systems of multiple measurement units must be unified into the global coordinate system to calculate the coordinates of measurement points. Traditional calibration methods include the control point method and the standard ruler method. The control point method deploys multiple transfer control points with known global coordinates inside the measurement space, and uses each measurement unit to measure these control points, and then calculates the coordinate transformation parameters. However, this method is extremely cumbersome and prone to point pairing errors, resulting in calculation failures. The standard ruler method is to manually place a standard ruler with a known length at multiple different positions in the measurement space, and establish a constraint equation about the calibration parameters based on the distance information. This method takes more than 1 hour for calibration. Although it can achieve high accuracy, it makes the calibration process more cumbersome and less efficient.

[0003] Existing calibration methods are difficult to improve the calibration efficiency while ensuring accuracy. In addition, when facing complex measurement objects, there is often the problem of laser occlusion, and a fixed measurement scheme cannot be adopted. Therefore, it is necessary to flexibly introduce new measurement units to expand the measurement range. However, after adding new measurement units, the current calibration methods cannot automatically unify the local coordinate systems of the new measurement units into the global coordinate system of the system, and can only recalibrate the entire measurement field, thus restricting the efficiency of dynamic measurement of the system. Summary of the Invention

[0004] The purpose of the present invention is to provide a calibration method for a laser positioning system with a self-organizing network mechanism, and solve the problem that existing calibration methods cannot improve the calibration efficiency while ensuring accuracy.

[0005] The technical solution adopted by the present invention is a calibration method for a laser positioning system with a self-organizing network mechanism, which is specifically implemented according to the following steps:

[0006] Step 1: Install a marking point on each laser emission station, and calibrate the coordinates of each marking point in the local coordinate system of the emission station;

[0007] Step 2: After arranging the laser emission stations at the measurement site, measure the distance between every two marking points;

[0008] Step 3: The laser emission stations measure the marking points with each other, and calibrate the laser positioning system in combination with the distance between every two marking points;

[0009] Step 4: After the laser positioning system is calibrated to form a measurement network, when a new laser emission station is added to the system, the original measurement network measures the marking points of the new emission station to achieve self-networking.

[0010] The features of the present invention also lie in:

[0011] Step 1 is specifically implemented according to the following steps:

[0012] Step 1.1: Fix a target ball-shaped photoelectric receiver on each laser emission station. The emission station and the receiver are rigidly connected to ensure that the relative position relationship between the receiver and the emission station remains unchanged, and the optical center of the receiver is defined as the marking point of the laser emission station;

[0013] Step 1.2: Measure the coordinates of the marking points on each laser emission station in the global coordinate system of the high-precision control field, and determine the coordinates Q of the marking points on the i-th laser emission station in the local coordinate system of the i-th laser emission station according to the transformation relationship between the global coordinate system and the local coordinate system of each laser emission station ii 。

[0014] Step 2 is specifically implemented according to the following steps:

[0015] Step 2.1: Use a high-precision laser tracker at the measurement site to measure the coordinates of each marking point in the coordinate system of the laser tracker respectively, and calculate the distance D between the i-th and j-th marking points from this ij ;

[0016] Step 2.2: According to Q ii and D ij , the i-th laser emission station scans and measures the marking points on the j-th laser emission station to determine the coordinates Q of the marking points on the j-th laser emission station in the coordinate system of the i-th laser emission station ji , and similarly determine the coordinates Q of the marking points on the i-th laser emission station in the coordinate system of the j-th laser emission station ij ;

[0017] Step 2.3: The coordinates of the marking points on n, n≥4 laser emission stations of the laser positioning system are known in the local coordinate systems of any two laser emission stations. According to formula (1):

[0018]

[0019] Determine the rotation matrix R ij and the translation matrix T ij from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station, that is, the preliminary system calibration parameters.

[0020] Step 3 specifically includes: measuring the marked points among n (n≥4) laser emission stations of the laser positioning system, and based on the orthogonality of the rotation matrix and the calculated D ij Optimizing the preliminary calibration parameters to determine the rotation matrix R from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station ij and the translation matrix T ij , which are the final system calibration parameters.

[0021] Step 4 is specifically implemented according to the following steps:

[0022] Step 4.1: Add a laser emission station H to the laser positioning system, automatically measure the coordinates Q of the marked points on the newly added laser emission station H in the common coordinate system of the laser positioning system, and calculate the distances D between this marked point and other marked points based on Q;

[0023] Step 4.2: Based on D and Q, preliminarily calibrate the conversion relationship from the laser emission station H to the common coordinate system of the laser positioning system, and optimize the preliminary calibration result according to Step 3 to complete the self - networking of the newly added measurement unit.

[0024] The beneficial effects of the present invention are as follows: The present invention provides a calibration method for a laser positioning system with a self - networking mechanism. Only by fixing a marked point on each laser emission station and measuring the distances between the marked points can the calibration be completed. When a new laser emission station needs to be added after the calibration is completed, the calibration of the new laser emission station can be completed through the self - networking mechanism, improving the calibration efficiency. Specific Embodiments

[0025] The present invention will be described in detail below in conjunction with specific embodiments.

[0026] The calibration method for a laser positioning system with a self - networking mechanism is specifically implemented according to the following steps:

[0027] Step 1: Install a marked point on each laser emission station and calibrate the coordinates of each marked point in the local coordinate system of the emission station;

[0028] Step 1 is specifically implemented according to the following steps:

[0029] Step 1.1: Fix a target spherical photoelectric receiver on each laser emission station. The emission station and the receiver are rigidly connected to ensure that the relative position relationship between the receiver and the emission station remains unchanged, and define the optical center of the receiver as the marked point of this laser emission station;

[0030] Step 1.2: Measure the coordinates of the marked points on each laser emission station in the global coordinate system of the high - precision control field, and determine the coordinates Q of the marked point on the i - th laser emission station in the local coordinate system of the i - th laser emission station according to the transformation relationship between the global coordinate system and the local coordinate system of each laser emission stationii ;

[0031] Step 2: After arranging the laser emission stations at the measurement site, measure the distances between every two marked points.

[0032] Step 2 is specifically implemented according to the following steps:

[0033] Step 2.1: Use a high-precision laser tracker at the measurement site to measure the coordinates of each marked point in the laser tracker coordinate system respectively, and thereby calculate the distance D between the i-th and j-th marked points. ij ;

[0034] Step 2.2: According to Q ii and D ij , the i-th laser emission station determines the coordinates Q of the marked points on the j-th laser emission station in the coordinate system of the i-th laser emission station by scanning and measuring the marked points on the j-th laser emission station. Similarly, determine the coordinates Q of the marked points on the i-th laser emission station in the coordinate system of the j-th laser emission station. ji ; ij ;

[0035] Step 2.3: The coordinates of the marked points on the n (n≥4) laser emission stations of the laser positioning system are known in the local coordinate systems of any two laser emission stations. According to formula (1):

[0036]

[0037] Determine the rotation matrix R ij and translation matrix T ij from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station, that is, the preliminary system calibration parameters.

[0038] Step 3: The laser emission stations measure the marked points with each other, and calibrate the laser positioning system in combination with the distances between every two marked points.

[0039] Step 3 specifically includes: The n (n≥4) laser emission stations of the laser positioning system measure the marked points with each other. According to the orthogonality of the rotation matrix and the calculated D ij , optimize the preliminary calibration parameters, and determine the rotation matrix R ij and translation matrix T ij from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station, that is, the final system calibration parameters.

[0040] Step 4: After the laser positioning system is calibrated to form a measurement network, when a new laser emission station is added to the system, the original measurement network measures the marked points of the new emission station to achieve self-networking.

[0041] Step 4 is specifically implemented according to the following steps:

[0042] Step 4.1: Add a new laser emission station H to the laser positioning system, automatically measure the coordinates Q of the marking point on the new laser emission station H in the common coordinate system of the laser positioning system, and calculate the distance D between this marking point and other marking points according to Q;

[0043] Step 4.2: Initially calibrate the conversion relationship from the laser emission station H to the common coordinate system of the laser positioning system according to D and Q, and optimize the initially calibrated result according to Step 3 to complete the self - networking of the newly added measurement unit.

[0044] The distance between the physical centers of the marking points in Step 1 can be measured by other high - precision instruments. In Step 2, it is convenient to measure the distance between the marking points using precision instruments. In Step 3, the information of the marking points and the distance information between the marking points can be mutually measured by the laser emission stations to establish an objective function for maximizing the calibration accuracy. In Step 4, the marking points of the newly added laser emission station can be jointly measured by the laser emission stations in the original measurement network.

[0045] Embodiment 1

[0046] A calibration method for a laser positioning system with a self - networking mechanism is specifically implemented according to the following steps:

[0047] Step 1: Install marking points and calibrate the coordinates of the marking points

[0048] Install a fixed target base on each laser emission station for placing the marking points. The installation position of the marking points should not block the laser signal of the laser emission station. Measure the coordinates of the marking points on each laser emission station in a high - precision control field, and then solve the coordinates Q of the marking points on the i - th emission station in the local coordinate system of the i - th emission station with the help of the conversion relationship between the high - precision field coordinate system and the laser emission station coordinate system ii , in this example, the calibration accuracy of the marking points is within 0.2 mm, and a target ball - type photoelectric receiver with a diameter of 38.1 mm is selected, and the optical center of the photoelectric receiver is used as the marking point, and the number of laser emission stations N = 4;

[0049] Step 2: Conduct a preliminary calibration of the laser positioning system, and use a high - precision coordinate measuring instrument to measure and calculate the distance D between marking points i and j ij

[0050] Taking the coordinates Q ii =(x ii y ii z ii ) T of the marking point on the i - th laser emission station in its own emission station coordinate system as the center of the sphere, and D ij as the radius, determine a spherical surface in the coordinate system of the i - th laser emission station According to the measurement principle of the laser positioning system, the i-th laser emission station measures the marked point on the j-th laser emission station to determine a ray L. The ray L intersects with the spherical surface to obtain the coordinates Q of the marked point on the j-th laser emission station in the coordinate system of the i-th laser emission station. ji Similarly, determine the coordinates Q of the marked point on the i-th laser emission station in the coordinate system of the j-th laser emission station. ij The coordinates of the marked points on N (N≥4) laser emission stations of the laser positioning system in the local coordinate systems of any two laser emission stations are known. According to formula (1):

[0051]

[0052] The rotation matrix R from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station can be solved by using the linear least squares method. ij and the translation matrix T ij , that is, the preliminary system calibration parameters. In this example, after replacing the optoelectronic receiver on the fixed target seat with a reflective target ball, since the radius of the optoelectronic receiver as the marked point is the same as the radius of the tracker target ball, the coordinates of their center points are equal, and the laser tracker has high measurement accuracy, so the laser tracker is used to measure the distance between the marked points;

[0053] Step 3. Perform precise calibration on the laser positioning system

[0054] Among the N (N≥4) laser emission stations of the laser positioning system, assume that the coordinates of the marked point on the j-th laser emission station in the local coordinate system of the i-th laser emission station are Q ji = [x y z] T , then the i-th laser emission station scans this marked point to obtain two point-plane constraint equations (2):

[0055]

[0056] In formula (2), [a m b m c m d m , (m = 1, 2) are the coefficients of the m-th laser plane of the i-th laser emission station. To enhance the constraint conditions, introduce n distance constraint equations between the marked points as formula (3):

[0057] D = ||||Q sq - Q nq || - d sn || |(3)

[0058] In formula (3), d sn is the distance between the marked point s and the marked point n. By combining the above constraints, the final objective function is obtained:

[0059]

[0060] where i is the serial number of the marked point, n is the serial number of the transmitting station, and i≠n, f pj is the orthogonal constraint equation satisfied by the p-th rotation matrix, and M1 and M2 are penalty factors. N transmitting stations scanning each other to the marked points can list N×(N - 1)×2 point-plane constraint equations and distance constraint equations, and each rotation matrix contains 6 orthogonal constraints f. Solving the transformation relationship between the coordinate systems of N laser transmitting stations introduces a total of N - 1 groups of rotation matrices R ij and translation matrices T ij to be solved, that is, (N - 1)×12 unknown parameters. In this example, when N = 4, the objective function contains 66 non-linear equations and 36 unknown parameters. Therefore, R ij and T ij can be solved by the non-linear optimization algorithm;

[0061] Step 4, Self-organizing network mechanism for adding laser transmitting stations

[0062] Define the local coordinate system of any one of the n laser transmitting stations that have been calibrated in the measurement field as the global coordinate system. When adding a new laser transmitting station H to the measurement field to expand the measurement range, the original measurement network automatically measures the coordinates Q of the marked points on the new laser transmitting station H in the global coordinate system, and transfers the coordinates of all marked points to the global coordinate system according to the solved rotation and translation matrices, thereby calculating the distances D between Q and these marked points. Then, based on D and Q, the initial values of the rotation and translation matrices for the transformation from the local coordinate system of the laser transmitting station H to the global coordinate system are solved, and finally, the final rotation and translation matrices are optimized according to the distance constraint and the orthogonal constraint, thus completing the self-organizing network of the new measurement unit.

[0063] The calibration method of the laser positioning system with a self-organizing network mechanism of the present invention only needs to fix a marked point on each laser transmitting station, and the calibration can be completed by measuring the distances between the marked points. After the calibration is completed, when adding a new laser transmitting station, the calibration of the new laser transmitting station can be completed through the self-organizing network mechanism, improving the calibration efficiency.

Claims

1. Calibration method for a laser positioning system with a self-organizing network mechanism, characterized in that, The implementation is specifically carried out according to the following steps: Step 1: Install a marking point on each laser emission station and calibrate the coordinates of each marking point in the local coordinate system of the emission station; Step 2: After arranging the laser emission stations at the measurement site, measure the distances between every two marking points; Step 3: The laser emission stations measure the marking points with each other, and calibrate the laser positioning system in combination with the distances between every two marking points; Step 4: After the laser positioning system is calibrated to form a measurement network, when a new laser emission station is added to the system, the original measurement network measures the marking points of the new emission station to achieve self-networking; The specific implementation of Step 2 is carried out according to the following steps: Step 2.1: At the measurement site, use a high-precision laser tracker to measure the coordinates of each marked point in the laser tracker coordinate system respectively, and thus calculate the distance D between the i-th and j-th marked points ij ; Step 2.2: According to the coordinates Q of the marking point on the i-th laser emission station in the local coordinate system of the i-th laser emission station ii and D ij , the i-th laser emission station determines the coordinates Q of the marking point on the j-th laser emission station in the coordinate system of the i-th laser emission station by scanning and measuring the marking point on the j-th laser emission station ji . Similarly, determine the coordinates Q of the marking point on the i-th laser emission station in the coordinate system of the j-th laser emission station ij ; Step 2.3: The coordinates of the marking points on n, n≥4 laser emission stations of the laser positioning system are known in the local coordinate systems of any two laser emission stations. According to formula (1): Determine the rotation matrix R from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station ij and the translation matrix T ij , which are the preliminary system calibration parameters.

2. The calibration method of the laser positioning system with a self-organizing network mechanism according to claim 1, characterized in that The specific implementation of Step 1 is carried out according to the following steps: Step 1.1: Fix a target spherical photoelectric receiver on each laser emission station. The emission station and the receiver are rigidly connected to ensure that the relative position relationship between the receiver and the emission station remains unchanged, and the optical center of the receiver is defined as the marking point of this laser emission station; Step 1.2 Measure the coordinates of the marked points on each laser emission station in the global coordinate system of the high-precision control field, and determine the coordinates Q of the marked points on the i-th laser emission station in the local coordinate system of the i-th laser emission station according to the transformation relationship between the global coordinate system and the local coordinate system of each laser emission station ii 。 3. The calibration method of the laser positioning system with a self-organizing network mechanism according to claim 1, characterized in that, The specific steps of step 3 include: measuring the marked points among n (n≥4) laser emission stations of the laser positioning system, and based on the orthogonality of the rotation matrix and the calculated D ij Optimizing the preliminary calibration parameters to determine the rotation matrix R from the coordinate system of the i-th laser emission station to the coordinate system of the j-th laser emission station ij and the translation matrix T ij , which are the final system calibration parameters.

4. The calibration method of the laser positioning system with a self-organizing network mechanism according to claim 1, characterized in that, The specific implementation of Step 4 is carried out according to the following steps: Step 4.1: Add a new laser emission station H to the laser positioning system, automatically measure the coordinates Q of the marking point on the new laser emission station H in the common coordinate system of the laser positioning system, and calculate the distances D between this marking point and other marking points according to Q; Step 4.2: According to the conversion relationship between the initially calibrated laser emission station H and the common coordinate system of the laser positioning system, and according to the optimized initial calibration result, complete the self-networking of the new measurement unit.

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