Six-degree-of-freedom target positioning and tracking precision calibration system and calibration method based on laser tracker

Abstract

The invention discloses a six-degree-of-freedom target positioning and tracking precision calibration system based on laser trackers, which comprises a laser tracker group, a target object and a target ball group, and is characterized in that the target ball group is fixed on the target object, the laser trackers are distributed and fixed around the target object, and laser signal transmission between the laser trackers and the corresponding target balls is ensured; firstly, a target ball is selected as a target, and it is guaranteed that all the laser trackers can collect laser signals of the target ball; and respectively acquiring the positions of the target ball target on the laser trackers, and calculating to obtain the relative position between the laser trackers to complete system calibration. Three laser trackers are arranged to track the corresponding target ball and the moving target object respectively, and measurement data and measurement time of the laser trackers are recorded; calculating the three-dimensional position information of the target ball according to the three-dimensional position measured by the laser tracker and the relative position calibrated by the laser tracker; and calculating three-dimensional position information and attitude information of the target object to realize real-time positioning and tracking of the three-dimensional position information and the three-dimensional angle information of the target object.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision measurement, and particularly relates to a six-degree-of-freedom target positioning and tracking accuracy calibration system and calibration method based on a laser tracker. Background Art

[0002] With the continuous improvement of the requirements for target positioning and tracking technology in modern industrial manufacturing, aerospace, and military defense and other fields, the importance of six-degree-of-freedom target positioning and tracking technology has become increasingly prominent. The six-degree-of-freedom target positioning and tracking technology aims to accurately measure the position (x, y, z) and attitude (θx, θy, θz) of a target in three-dimensional space, providing key data support for complex operations and precise control. However, there are still many deficiencies in the prior art in achieving high-precision six-degree-of-freedom target positioning and tracking.

[0003] Traditional target positioning and tracking methods mostly rely on a single sensor or measurement device, such as an optical camera, an inertial measurement unit, a lidar, a millimeter-wave radar, an ultrasonic radar, etc. These methods have obvious limitations in terms of measurement accuracy, data update rate, and environmental adaptability. For example, an optical camera is easily affected by light conditions, resulting in unstable measurement accuracy; although an inertial measurement unit can provide real-time data, it will generate cumulative errors over time, affecting long-term stability; a lidar is easily affected by weather, with relatively high accuracy but only at the centimeter level; although a millimeter-wave radar has good robustness in bad weather, the sparse point cloud leads to low measurement accuracy and poor detail resolution; an ultrasonic radar is inexpensive but has poor measurement accuracy.

[0004] In addition, the prior art lacks effective calibration methods and systems for six-degree-of-freedom target positioning and tracking accuracy verification. Calibration is a key step to ensure the accuracy of a measurement system, but traditional calibration methods can often only calibrate for specific devices or specific degrees of freedom, and cannot comprehensively and systematically solve the problem of six-degree-of-freedom target positioning and tracking accuracy verification. This not only limits the performance improvement of the measurement system, but also brings many inconveniences and risks to practical applications. In target positioning and tracking tasks in complex environments, such as industrial robot operations, aerospace vehicle docking, and military target monitoring, higher requirements are put forward for the accuracy, efficiency, and adaptability of the measurement system.

[0005] In summary, the prior art has problems such as insufficient measurement accuracy, lack of calibration methods, and poor adaptability to complex environments in the field of six-degree-of-freedom target positioning and tracking. These problems seriously restrict the development and application of related technologies. Therefore, developing a high-precision six-degree-of-freedom target positioning and tracking calibration method and system that can solve the above problems has important practical significance and broad application prospects. Summary of the Invention

[0006] The object of the present invention is to solve the above problems and provide a six-degree-of-freedom target positioning and tracking accuracy calibration system and calibration method based on a laser tracker, which have high measurement accuracy, a simple calibration method, and a wide range of applications.

[0007] To solve the above technical problems, the technical solution of the present invention is: a six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker, including a laser tracker group, a target object, and a target ball group. The laser tracker group includes laser tracker L1, laser tracker L2, and laser tracker L3, and the number of laser trackers in the laser tracker group is not less than three. The target ball group includes target balls B1, B2, and B3, and the number of target balls in the target ball group is not less than three. Target balls B1, B2, and B3 are fixed on the target object at the vertex positions of a polygon, and the laser trackers are distributed and fixed around the target object without moving after being fixed, and it is ensured that the laser signal transmission between the laser tracker and the corresponding target ball is normal. First, select one target ball as the target to ensure that all three laser trackers can collect the laser signal of this target ball. Respectively obtain the positions of this target ball target in the three laser trackers L1(x 10 , y 10 , z 10 ), L2(x 20 , y 20 , z 20 ), and L3(x 30 , y 30 , z 30 ), and calculate the relative positions between the laser trackers Complete the system calibration.

[0008] Furthermore, the method for obtaining the positions of the target ball target in the three laser trackers adopts a six-degree-of-freedom positioning and tracking calibration method, and the six-degree-of-freedom positioning and tracking calibration method includes the following steps:

[0009] S11. Set the target object target balls to be fixed at the vertex positions of a regular polygon, and the laser trackers respectively track the corresponding target balls;

[0010] S12. Move the target object and respectively record the measurement data and measurement time of the laser trackers;

[0011] S13. According to the three-dimensional positions L1(x 1i , y 1i , z 1i ) measured by the laser trackers, L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z 3i ) and the relative positions calibrated by the laser trackers Calculate the three-dimensional position information of the three target balls B1(x 1j , y 1j , z 1j )), B2(x 2j , y 2j , z 2j )), B3(x 3j , y 3j , z 3j ) at each measurement time in the same coordinate system;

[0012] S14. According to the real-time position information of the target balls in the same coordinate system, calculate the three-dimensional position information T(x j , y j , z j ) and attitude information T(θ 1j , θ 2j , θ 3j ) of the target object, and realize the real-time positioning and tracking of the three-dimensional position information and three-dimensional angle information of the target.

[0013] Furthermore, the calculation of the three-dimensional position information T(x j , y j , z j ) of the target object is divided into three cases: First, a definite position point on the target object is known, and the three-dimensional position information of the target is represented by this point. In this case, a target ball is set at the definite position point, and the measurement result of the ball is the three-dimensional position information of the target object; Second, consider that the median value of each position point represents the three-dimensional position information of the target object. In this case, calculate the median value of the maximum value and the minimum value of all the position information of the target balls, which is the three-dimensional position information of the target object; Third: Consider representing the three-dimensional position information of the target object by the average position. In this case, calculate the average value of all the three-dimensional position information of the target balls, which is the three-dimensional position information of the target object; The three-dimensional attitude information T(θ 1j , θ 2j , θ 3j ) of the target object is represented by the transformation matrix obtained by combining the normal vector of the plane determined by three points and the rotation matrix of the normal vector after movement around the three coordinate axes.

[0014] Furthermore, the target balls B1, B2, and B3 are fixed at the apex positions of a triangle on the target object.

[0015] Furthermore, the first selected target ball as the target ball is B1, ensuring that all three laser trackers can collect the laser signal of B1; respectively obtain the positions of B1 in the coordinate systems of L1, L2, and L3 as L1(x 10 , y 10 , z 10 ), L2(x 20 , y 20 , z20 ) and L3(x 30 , y 30 , z 30 ), the relative positions between the laser trackers in the same coordinate system are calculated The system calibration is completed.

[0016] Further, the polygon in S11 is a triangle, and the laser tracker L1, the laser tracker L2, and the laser tracker L3 respectively track the corresponding target balls B1, B2, and B3; the measurement data and measurement time in S12 are L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z 3i ); in S13, the three-dimensional position information of each measurement time of the three target balls in the same coordinate system is calculated as B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ); in S14, according to the real-time position information of the target balls in the same coordinate system, the three-dimensional position information T(x j , y j , z j ) and the attitude information T(θ 1j , θ 2j , θ 3j ) of the target object are calculated to realize the real-time positioning and tracking of the three-dimensional position information and three-dimensional angle information of the target.

[0017] Further, the target ball is the target ball B1, and all target balls refer to the target ball B1, the target ball B2, and the target ball B3.

[0018] Further, the transformation matrix is represented by the combination of the plane normal vector determined by calculating three points and the rotation matrix of the post-movement normal vector around the three coordinate axes. Specifically, it is: the plane normal vector determined by calculating B1, B2, and B3 and the rotation matrix R(θ1, θ2, θ3) = R(θ3)R(θ1)R(θ2) of the post-movement normal vector around the three coordinate axes in combination. Here, the ZXY convention and the external rotation convention are adopted.

[0019] The beneficial effects of the present invention are:

[0020] 1. The six-degree-of-freedom target positioning and tracking accuracy calibration system and calibration method provided by the present invention are based on the target six-degree-of-freedom positioning and tracking calibration method and system of a laser tracker, which can perform six-degree-of-freedom quantitative analysis of three-dimensional position information and three-dimensional attitude information of different types of targets, and are applicable to high-precision six-degree-of-freedom target positioning and tracking in different fields.

[0021] 2. The target six-degree-of-freedom positioning, tracking calibration method and system proposed by the present invention can verify the target positioning and tracking accuracy of different sensors or measurement devices, such as optical cameras, inertial measurement units, lidars, millimeter-wave radars, ultrasonic radars, etc.

[0022] 3. The method and system proposed by the present invention are based on a laser tracker, have a measurement range of up to hundreds of meters and a measurement accuracy of micrometers, can accurately provide precise position information, and the measurement results have high repeatability. It ensures that the method and system have high-precision six-degree-of-freedom positioning capabilities and are applicable to target positioning accuracy verification.

[0023] 4. The method and system proposed by the present invention are based on a laser tracker, have a tracking function, can continuously track the target ball and measure the position of the target ball in real time, and the maximum acquisition frequency can reach 1000 points per second, far exceeding common sensors or distance measurement devices such as lidars and cameras, meeting the requirements of most scenarios for the tracking acquisition frequency, and are applicable to target tracking accuracy verification.

[0024] 5. The present invention has good accuracy, efficiency and adaptability, provides new methods and means for six-degree-of-freedom target positioning and tracking accuracy detection, and can be widely applied to fields such as industrial manufacturing, aerospace, and national defense. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of a six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to the present invention.

[0026] Description of the Reference Numerals: T, target object. Detailed Embodiments

[0027] The following further describes the present invention with reference to the drawings and specific embodiments:

[0028] Embodiment 1

[0029] A six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker provided by the present invention includes a laser tracker group, a target object T, and a target ball group. The laser tracker group includes a laser tracker L1, a laser powder tracker L2, and a laser powder tracker L3, and the number of laser trackers in the laser tracker group is not less than three. The target ball group includes target balls B1, B2, and B3, and the number of target balls in the target ball group is not less than three. The target balls B1, B2, and B3 are fixed on the target object T at the positions of the polygon vertices, and the laser trackers are distributed and fixed around the target object T and will not move after being fixed, and it is ensured that the laser signal transmission between the laser tracker and the corresponding target ball is normal.

[0030] First, select a target ball as the target to ensure that all three laser trackers can collect the laser signal of this target ball. Respectively obtain the positions of this target ball in the three laser trackers as L1(x 10 , y 10 , z 10 ), L2(x 20 , y 20 , z 20 ), and L3(x 30 , y 30 , z 30 ), and calculate the relative positions between the laser trackers Complete the system calibration. The position coordinate system of the laser tracker can be based on the coordinate of any one of the laser trackers as the reference coordinate system.

[0031] In this embodiment, the target ball is target ball B1, and all target balls refer to target ball B1, target ball B2, and target ball B3. The target balls B1, B2, and B3 are fixed on the target object T at the positions of the triangle vertices. The target ball in "First, select a target ball as the target" is target ball B1, and ensure that all three laser trackers can collect the laser signal of B1. Respectively obtain the positions of B1 in the coordinate systems of L1, L2, and L3 as L1(x 10 , y 10 , z 10 ), L2(x 20 , y 20 , z 20 ), and L3(x 30 , y 30 , z 30 ), and calculate the relative positions between the laser trackers in the same coordinate system Complete the system calibration.

[0032] The present invention sets the number of laser trackers according to the actual situation. At least three laser trackers can be used to confirm the pose, and more laser trackers can be used according to actual usage needs. In this embodiment, three laser trackers are set to track the corresponding target balls respectively. The moving object is moved, and the measurement data and measurement time of the laser trackers are recorded; according to the three-dimensional positions (x1i, y1i, z1i), (x2i, y2i, z2i), (x3i, y3i, z3i) measured by the laser trackers and the relative positions calibrated by the laser trackers, the three-dimensional position information (x 1j , y 1j , z 1j ), (x 2j , y 2j , z 2j ), (x 3j , y 3j , z 3j ) of the target balls is calculated; according to the real-time three-dimensional position information of the target balls, the three-dimensional position information (x j , y j , z j ) and the attitude information (θ 1j , θ 2j , θ 3j ) of the object are calculated to realize the real-time positioning and tracking of the three-dimensional position information and the three-dimensional angle information of the object.

[0033] The six-degree-of-freedom positioning and tracking calibration method is used to obtain the positions of the target balls on the three laser trackers. The six-degree-of-freedom positioning and tracking calibration method includes the following steps:

[0034] S11. Set the target ball of the object to be fixed at the vertex positions of a regular polygon, and the laser trackers respectively track the corresponding target balls.

[0035] In step S11, the polygon is a triangle, and the laser tracker L1, the laser powder tracker L2, and the laser powder tracker L3 respectively track the corresponding target balls B1, B2, and B3.

[0036] S12. Move the object T, and record the measurement data and measurement time of the laser trackers respectively.

[0037] In step S12, the measurement data and measurement time are respectively L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z3), where L1(x 1i , y 1i , z 1i ), L2(x2i , y 2i , z 2i ), L3(x 3i , y 3i , z 3i ) represents the measured position coordinate data, and i represents different measurement times.

[0038] S13. According to the three-dimensional positions L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z3) measured by the laser tracker and the relative positions calibrated by the laser tracker Calculate the three-dimensional position information B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ) of the three target balls at each measurement time in the same coordinate system.

[0039] In this embodiment, in step S13, the three-dimensional position information B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ) of the three target balls at each measurement time in the same coordinate system is calculated, where j represents different measurement times.

[0040] S14. According to the real-time position information of the target balls in the same coordinate system, calculate the three-dimensional position information T(x j , y j , z j ) and the attitude information T(θ 1j , θ 2j , θ 3j ) of the target object, and realize the real-time positioning and tracking of the three-dimensional position information and three-dimensional angle information of the target.

[0041] In this embodiment, in step S14, according to the real-time position information of the target balls in the same coordinate system, calculate the three-dimensional position information T(x j , y j, z j ), and the attitude information T(θ 1j , θ 2j , θ 3j ), to achieve real-time positioning and tracking of the target three-dimensional position information and three-dimensional angle information.

[0042] The three-dimensional position information T(x j , y j , z j ) of the target object is calculated in three cases:

[0043] First, when a definite position point on the target object is known and the three-dimensional position information of the target is represented by this point. In this case, a target ball is set at the definite position point, and the measurement result of the ball is the three-dimensional position information of the target object.

[0044] Specifically, in this embodiment, the three-dimensional position information of the target is represented by a definite position point on the target object. The target ball B1 is set at the definite position point, and the measurement result of the target ball B1(x j , y j , z j ) is the three-dimensional position information T(x j , y j , z j ) of the target object.

[0045] Second, considering the median of each position point represents the three-dimensional position information of the target object. In this case, the median of the maximum and minimum values of all the position information of the target balls is calculated as the three-dimensional position information of the target object.

[0046] Specifically, in this embodiment, the median of the position points (x j , y j , z j ) at each moment j represents the three-dimensional position information of the target object. Calculate the median of the maximum and minimum values of the position information of B1, B2, and B3

[0047] which is the three-dimensional position information of the target object. For any moment, the maximum and minimum values of x, y, and z of three or more target balls are selected for calculation.

[0048] Third: Considering representing the three-dimensional position information of the target object by the average position. In this case, the mean value of all the three-dimensional position information of the target balls is calculated as the three-dimensional position information of the target object. The three-dimensional attitude information T(θ 1j , θ 2j , θ 3j ) is represented by the transformation matrix combining the normal vector of the plane determined by three points and the rotation matrix of the normal vector after movement around the three coordinate axes.

[0049] Specifically, in this embodiment, the three-dimensional position information of the target is represented by the average position, and the mean values of the three-dimensional position information of B1, B2, and B3 are calculated. That is the three-dimensional position information of the target. Among them is the position point (x j , y j , z j ) at each moment j. For any moment, after summing the measured values of three or more target balls in x, y, and z, the average is taken.

[0050] It is represented by the transformation matrix combined with the plane normal vector determined by calculating three points and the rotation matrix of the post-movement normal vector around the three coordinate axes. Specifically: by calculating the plane normal vector determined by B1, B2, and B3 and the rotation matrix R(θ1, θ2, θ3) = R(θ3)R(θ1)R(θ2) of the post-movement normal vector around the three coordinate axes. Here, the ZXY sequence and the external rotation convention are adopted.

[0051] In this embodiment, the three-dimensional attitude information T(θ 1j , θ 2j , θ 3j ) of the target is calculated: by calculating the plane normal vector determined by B1, B2, and B3: and the rotation matrix of the post-movement normal vector around the three coordinate axes:

[0052]

[0053] It is represented by the combined transformation matrix. Here, the ZXY sequence and the external rotation convention are adopted. Among them, θ1, θ2, and θ3 are the three angles of rotation along X, Y, and Z respectively, R(θ1, θ2, θ3) is the rotation matrix, and R(θ1), R(θ2), and R(θ3) are the rotation matrices along X, Y, and Z respectively.

[0054] Embodiment 2

[0055] Build a six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker:

[0056] Such as Figure 1As shown in the figure, a target six-degree-of-freedom positioning, tracking and calibration system is built. The system consists of three laser trackers, namely laser tracker L1, laser tracker L2 and laser tracker L3, and is configured with three target balls, namely target ball B1, target ball B2 and target ball B3. The three laser trackers and the target balls are fixed to the target object T at the apex positions of an equilateral triangle. The laser trackers are distributed and fixed around the target and will not move after being fixed, and it is ensured that the laser signal transmission between the laser tracker and the corresponding target ball is normal. The lidar is fixed directly above, and the position of the lidar is adjusted to ensure that the target is in the middle of the lidar field of view and remains within the market range during the movement, and the point cloud data can be collected normally.

[0057] In this embodiment, the lidar is selected as the LIVOX Mid360 lidar model, and the laser tracker is selected as the Leica AT930 model. This device uses an interferometer and an absolute distance meter to jointly calculate the coordinates of the target ball in its coordinate system and can provide accurate position measurement. Among them, the interferometer uses the interference phenomenon of light to measure the phase difference between the emitted and reflected laser beams, and then determines the propagation path of the laser beam and the position of the target object, with extremely high measurement accuracy.

[0058] In this embodiment, the maximum allowable error (MPE) of the interferometer used is 0.4um, and the MPE of the absolute distance meter is 10um. This device has a tracking function, can continuously track the target ball and measure the position of the target ball in real time. The maximum acquisition frequency of the point cloud can reach 1000 points / second, far exceeding the lidar frequency of 10fps. In addition, this device can send the collected data to all connected devices under its local area network in real time through WIFI connection, and the point cloud collected by it can be obtained through a computer and the timestamp of each point can be recorded. In this experiment, Dell Precision 7750 is used as the data acquisition platform, and Spatial Analyzer software and Leica Tracker Pilot software are installed to collect the data of the laser tracker.

[0059] Select target ball B1 as the target to ensure that lidar L and the three laser trackers can all collect the laser signal of B1. Respectively obtain the positions L1(x1, y1, z1), L2(x2, y2, z2) and L3(x3, y3, z3) of target ball B1 in the respective coordinate systems of laser tracker L1, laser tracker L2 and laser tracker L3, and at the same time collect the point cloud data of target ball B1 on the lidar. Move target ball B1 and collect multiple groups of data. Correlate the three-dimensional spatial position coordinates in the coordinate systems of each laser tracker with the point cloud clustering center of the lidar one by one, and unify them into the lidar coordinate system to complete the external parameter calibration of the experimental system. The external parameter calibration between the lidar and the laser tracker can be regarded as a PnP problem. The specific method is to first use the EPnP method to solve the initial value of the external parameters, and then use the LM algorithm to optimize the initial value.

[0060] In this embodiment, the steps of the six-degree-of-freedom positioning, tracking and calibration experiment are as follows:

[0061] S21. Fix the positions of the apexes of the triangle of the target object's target balls. Laser tracker L1, laser tracker L2, and laser tracker L3 respectively track the corresponding target balls B1, B2, and B3. The lidar is fixed directly above the target, and the target is in the middle of the lidar's field of view, and point cloud data can be normally collected.

[0062] S22. Move the target object, and record the measurement data and measurement time of the laser tracker L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z 3i ). At the same time, collect the lidar point cloud data and record it as a bag file.

[0063] Data processing and accuracy verification: Process the point cloud data through algorithms such as clustering to obtain the three-dimensional position information L(x j , y j , z j ) and L(θ 1j , θ 2j , θ 3j ) of the target object.

[0064] S23. According to the three-dimensional positions L1(x 1i , y 1i , z 1i ) measured by the laser tracker, L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z3) and the extrinsic calibration between the lidar and the laser tracker, calculate the three-dimensional position information B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ) of each target ball in the lidar coordinate system at each measurement time.

[0065] S24. According to the real-time position information of the target ball in the lidar coordinate system, calculate the three-dimensional position information T(x j , yj , z j ), and the attitude information T(θ 1j , θ 2j , θ 3j ).

[0066] The calculation of the three-dimensional position information of the target under the three-laser tracker calibration system includes but is not limited to the following three types:

[0067] The first type: Represent the three-dimensional position information of the target with the determined position points on the target. Set the target ball B1 at the determined position points, and the measurement result of the target ball B1(x j , y j , z j ) is the three-dimensional position information T(x j , y j , z j ) of the target.

[0068] The second type: Represent the three-dimensional position information of the target with the median of each position point. Calculate the median of the maximum and minimum values of the position information of B1, B2, and B3, which is the three-dimensional position information of the target:

[0069]

[0070] The third type: Represent the three-dimensional position information of the target with the average position. Calculate the mean value of the three-dimensional position information of B1, B2, and B3, which is the three-dimensional position information of the target:

[0071]

[0072] The calculation of the three-dimensional attitude information of the target under the three-laser tracker calibration system includes but is not limited to calculating the plane normal vector determined by B1, B2, and B3: and the rotation matrix of the post-movement normal vector around the three coordinate axes:

[0073] The transformation matrix represented by the combination. Here, the ZXY convention and the external rotation convention are adopted.

[0074] The process of verifying the target positioning and tracking accuracy of the lidar is as follows:

[0075] Calculate the three-dimensional position information L(x j , y j , z j ) and L(θ 1j , θ 2j , θ 3j ) of the target obtained by the lidar, and the three-dimensional position information T(x j , y j , z j) and the error of the attitude information T(θ 1j , θ 2j , θ 3j ), to realize the verification of the positioning and tracking accuracy of the lidar target.

[0076] For the positioning and tracking algorithms of different types of lidars, the coordinate transformation of the target attitude includes, but is not limited to, transformation methods such as rotation matrices, Euler angles, and quaternions.

[0077] The evaluation indexes for the positioning and tracking accuracy of the lidar target include, but are not limited to, position error, attitude angle error, number of trajectory points, absolute trajectory error (ATE, Absolute Trajectory Error), etc.

[0078] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on these technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker, characterized in that: The invention comprises a laser tracker group, a target object (T) and a target ball group, wherein the laser tracker group comprises a laser tracker L1, a laser powder tracker L2 and a laser powder tracker L3, and the number of laser trackers in the laser tracker group is not less than three; the target ball group comprises a target ball B1, a target ball B2 and a target ball B3, and the number of target balls in the target ball group is not less than three, and the target balls B1, B2 and B3 are fixed on the target object (T) according to the polygonal vertex positions, and the laser trackers are distributed and fixed around the target object (T), and do not move after being fixed, and ensure that the laser signal transmission between the laser tracker and the corresponding target ball is normal; first select a target ball as the target, and ensure that the three laser trackers can collect the laser signal of the target ball; respectively obtain the position L1 (x 10 ,y 10 , z 10 ), L2(x 20 ,y 20 , z 20 ) and L3(x 30 ,y 30 , z 30 ), calculate the relative position between the laser trackers Complete system calibration.

2. The six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 1, characterized in that The method for obtaining the positions of the target ball on three laser trackers adopts a six-degree-of-freedom positioning and tracking calibration method, and the six-degree-of-freedom positioning and tracking calibration method includes the following steps: S11. Set the target ball to be fixed at the apex positions of a regular polygon, and the laser trackers respectively track the corresponding target balls; S12. Move the target object (T), and record the measurement data and measurement time of the laser trackers respectively; S13. According to the three-dimensional positions L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z3) measured by the laser tracker and the relative positions calibrated by the laser tracker, calculate the three-dimensional position information B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ) of each of the three target balls at each measurement time in the same coordinate system; S14. Calculate the three-dimensional position information T(x j , y j , z j ) and the attitude information T(θ 1j , θ 2j , θ 3j ) of the target object based on the real-time position information of the target ball in the same coordinate system, so as to achieve real-time positioning and tracking of the three-dimensional position information and three-dimensional angle information of the target.

3. A six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 1, characterized in that: The calculation of the three-dimensional position information T(x j , y j , z j ) is divided into three cases: First, when a definite position point on the target object is known and the three-dimensional position information of the target object is represented by this point. In this case, a target ball is set at the definite position point, and the measurement result of the target ball is the three-dimensional position information of the target object; Second, considering that the median value of each position point represents the three-dimensional position information of the target object. In this case, the median value of the maximum value and the minimum value of all target ball position information is calculated as the three-dimensional position information of the target object; Third: Considering that the average position represents the three-dimensional position information of the target object. In this case, the average value of all target ball three-dimensional position information is calculated as the three-dimensional position information of the target object; The three-dimensional attitude information T(θ 1j , θ 2j , θ 3j ) is represented by the transformation matrix combining the rotation matrices of the normal vector of the plane determined by three points and the normal vector after movement around the three coordinate axes.

4. A six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 1, characterized in that: The target balls B1, B2 and B3 are fixed at the apex positions of a triangle on the target object (T).

5. The six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 1, characterized in that: First, select a target ball as the target ball B1, ensuring that all three laser trackers can collect the laser signal of B1; respectively obtain the positions of B1 in the coordinate systems of L1, L2, and L3 as L1(x 10 , y 10 , z 10 ), L2(x 20 , y 20 , z 20 ), and L3(x 30 , y 30 , z 30 ), and calculate the relative positions of the laser trackers in the same coordinate system Complete the system calibration.

6. A six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 2, characterized in that: The polygon in S11 is a triangle. The laser tracker L1, the laser powder tracker L2, and the laser powder tracker L3 respectively track the corresponding target balls B1, B2, and B3; the measurement data and measurement time in S12 are L1(x 1i , y 1i , z 1i ), L2(x 2i , y 2i , z 2i ), L3(x 3i , y 3i , z 3i ); In S13, calculate the three-dimensional position information B1(x 1j , y 1j , z 1j ), B2(x 2j , y 2j , z 2j ), B3(x 3j , y 3j , z 3j ) of each target ball at each measurement time in the same coordinate system; In S14, according to the real-time position information of the target balls in the same coordinate system, calculate the three-dimensional position information T(x j , y j , z j ) and attitude information T(θ 1j , θ 2j , θ 3j ) of the target object, and realize the real-time positioning and tracking of the three-dimensional position information and three-dimensional angle information of the target.

7. The six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 3, characterized in that: The target ball is target ball B1, and all target balls refer to target ball B1, target ball B2 and target ball B3.

8. The six-degree-of-freedom target positioning and tracking accuracy calibration system based on a laser tracker according to claim 3, characterized in that: The transformation matrix of the plane normal vector determined by calculating the three points and the rotation matrix of the normal vector around the three coordinate axes after the movement is expressed as follows: the plane normal vector determined by calculating B1, B2, B3 The transformation matrix is represented by the combination of the rotation matrix R(θ1, θ2, θ3) = R(θ3)R(θ1)R(θ2) of the normal vector around the three coordinate axes after movement, and the ZXY straight rule and external rotation convention are adopted here.

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