Line laser contourgraph hand-eye calibration device and method

Abstract

The invention discloses a line laser contourgraph hand-eye calibration device which comprises a robot system, a line laser contourgraph and a calibration plate. The invention further discloses a line laser contourgraph hand-eye calibration method which comprises the steps that the calibration plate is placed at a fixed position, and a first matrix under a robot base coordinate system is obtained; the line laser contourgraph is driven by the mechanical arm to scan the calibration plate, and point cloud data of the mechanical arm under different poses are obtained; fitting the spliced surface contour of the calibration plate based on the point cloud data under different poses to obtain a second matrix under the coordinate system of the line laser contourgraph; according to the relation among the robot base coordinate system, the robot tail end coordinate system and the line laser contourgraph coordinate system, a model containing a hand-eye calibration matrix is established, and then the hand-eye calibration matrix is solved. According to the invention, accurate and repeatable pose control can be provided, the calibration cost is reduced, the calibration process is simplified, and meanwhile, the hand-eye calibration efficiency and the precision automation degree are improved.

Description

Technical Field

[0001] The invention relates to the field of robot technology and machine vision technology, in particular to a hand-eye calibration device and method for a line laser profiler. Background Art

[0002] In high-precision engineering fields such as aerospace and shipbuilding, when it comes to the assembly and quality control of large structural parts, ensuring that the various components can be accurately combined together is the key to the success of the project. As a non-contact 3D measurement tool, the line laser profiler is widely used in these industries because of its fast, accurate and suitable for complex shapes.

[0003] When used in conjunction with a robot, a line laser profiler can automate the measurement process, improve work efficiency and reduce human errors. In order for a line laser profiler to work with a robot, a hand-eye calibration is necessary. This calibration process is designed to determine the transformation relationship between the line laser profiler coordinate system and the flange coordinate system of the robot end effector. This transformation relationship is critical to ensure that the robot's motion instructions can be correctly mapped to the line laser profiler's measurement data. The accuracy of the hand-eye calibration directly affects the quality of the final measurement results, while its speed determines the efficiency and cost-effectiveness of the entire project.

[0004] The patent application with publication number CN 115752295 A discloses an automatic hand-eye calibration method for a line laser profiler, comprising: placing a calibration sphere in the field of view of the line laser profiler, manually adjusting the device so that the laser line covers the center of the sphere, and recording the laser line data and the device posture; repeating this process to obtain multiple sets of data at different postures; performing batch circle fitting on the collected laser line data to determine the coordinates of the center of the calibration sphere in the measurement coordinate system; calculating a pre-calibrated hand-eye relationship matrix according to the coordinates of the center of the sphere; based on the pre-calibrated matrix and the horizontal and vertical scanning ranges, automatically calculating and inversely solving multiple sets of different translation and rotation translation scanning postures and their corresponding motion joint parameters; inputting the calculated posture parameters into a motion control device, driving the device to the target position, and collecting laser line data at each posture; performing batch circle fitting again, calculating the average coordinates of the center of the sphere at each posture, respectively obtaining the translation and rotation hand-eye relationship matrices, and merging them into the final hand-eye relationship matrix. The existing technology determines the scanning posture by manually adjusting the device posture multiple times, calculating the spherical center coordinates, and inversely solving the motion joint parameters. This is not only time-consuming, but also requires a lot of manual intervention, which reduces the calibration efficiency.

[0005] The patent document with the publication number CN 115861445 B discloses a hand-eye calibration method based on a calibration plate three-dimensional point cloud, including: constructing a two-dimensional checkerboard calibration plate and a three-dimensional scanning system composed of a camera and a projector; using the two-dimensional checkerboard calibration plate to perform single-target and dual-target calibration on the camera and the projector respectively, and obtaining the internal parameters of the camera and the projector and the coordinate system transformation relationship between the two; changing the posture of the two-dimensional checkerboard calibration plate at least three times, and obtaining at least three sets of transformation matrices of the two-dimensional checkerboard calibration plate relative to the camera coordinate system and the transformation matrix of the end of the manipulator relative to the coordinate system of the manipulator base through the three-dimensional coordinates of the point cloud of the two-dimensional checkerboard calibration plate; solving and obtaining a high-precision transformation matrix of the camera coordinate system relative to the coordinate system of the manipulator base. The prior art involves constructing a three-dimensional scanning system composed of a two-dimensional checkerboard calibration plate, a camera and a projector, and performing multiple single-target and dual-target calibrations, which not only increases the complexity of the system, but also the process of changing the posture of the calibration plate multiple times also prolongs the calibration time and reduces the efficiency of project execution. Summary of the invention

[0006] The purpose of the present invention is to provide a hand-eye calibration device and method for a line laser profiler, so as to quickly obtain the conversion relationship between the line laser profiler coordinate system and the robot end coordinate system, improve the accuracy, execution efficiency and degree of automation of hand-eye calibration, and reduce the execution cost of robot projects.

[0007] The present invention provides a hand-eye calibration device for a line laser profiler, comprising: Robot system: including a multi-degree-of-freedom robotic arm, a fixed base and a motion controller, capable of performing positioning and movement tasks in space according to instructions, and an interface for fixing a line laser profiler is installed at the end of the robotic arm; Line laser profiler: fixed on the end effector of the robot, used to emit a linear laser beam and receive reflected light, and measure the data of the surface profile of the object by analyzing the reflected light information; Calibration plate: includes a rectangular plate as a base and an isosceles trapezoidal block erected on the rectangular plate.

[0008] Furthermore, a 0.1 mm wide and 0.1 mm deep engraved line is provided in the middle of the isosceles trapezoidal block for alignment with the laser emitted by the line laser profiler; The isosceles trapezoidal block is arranged at the central position of the rectangular flat plate, and is fixed to the rectangular flat plate with the end face where the bottom edge of the isosceles trapezoidal block is located as a fixing face, and the projection line of the splicing face of the isosceles trapezoidal block on the rectangular flat plate coincides with the line connecting the midpoints of the two parallel sides of the rectangular flat plate.

[0009] Furthermore, the base angle of the isosceles trapezoidal block is 45°, and the waist and upper side are of equal length.

[0010] The present invention also provides a line laser profiler hand-eye calibration method, which is implemented by the line laser profiler hand-eye calibration device as described above, and includes: Step 1: Place the calibration plate in a fixed position and fix the line laser profiler at the end of the robot; Step 2: Control the robot arm through the motion controller to drive the line laser profiler to align with the isosceles trapezoid of the calibration plate, and record the position and posture matrix of the robot TCP as the first matrix; Step 3: The line laser profiler collects the point cloud data of the isosceles trapezoid, and extracts the coordinate values ​​of the four vertex features in the line laser profiler coordinate system through feature search, and uses the coordinate values ​​measured by the four vertex features as the second matrix; Step 4: transform multiple postures of the robot to obtain a first matrix of multiple groups of robot TCP positions and a second matrix of calibration plate feature points under corresponding postures; Step 5: Based on the relationship between the robot base coordinate system, the robot end coordinate system and the line laser profiler coordinate system, a model including the hand-eye calibration matrix is ​​established, and the model is solved by combining the multiple sets of first matrices and second matrices obtained in step 4.

[0011] The present invention can quickly calculate the conversion relationship between the line laser profiler coordinate system and the robot terminal coordinate system through a simple calibration plate, thereby reducing the calibration cost and simplifying the calibration process; at the same time, the robot is used to clamp the line laser profiler for automatic adjustment to quickly obtain point cloud data, thereby improving the automation level of calibration and the efficiency and accuracy of hand-eye calibration, providing accurate and repeatable posture control, and enhancing the reliability of the calibration results.

[0012] Furthermore, in step 2, the motion controller is used to control the robot arm to drive the line laser profiler to align and scan the calibration plate to obtain the coordinate data of the feature points of the robot in different positions, including: The motion controller drives the robotic arm so that the line laser beam emitted by the line laser profiler at the end of the robotic arm coincides with the engraved lines of the isosceles trapezoidal block on the calibration plate, and the calibration plate is scanned to obtain the point cloud data of the calibration plate; The position and posture of the robotic arm are adjusted through the motion controller, and the calibration plate point cloud data of the robotic arm in multiple positions is scanned.

[0013] Further, the posture of the robot arm is represented by a transformation matrix between coordinate systems, including a rotation matrix and a translation vector in three-dimensional space; the multiple postures represent at least four postures; The point cloud data includes four scanning results obtained in the same posture, namely, the scanning result of the line laser profiler at the initial position, the scanning result of the initial position translated along the trapezoidal plane for a certain distance, the scanning result after the line laser profiler is rotated 180°, and the result of being translated along the trapezoidal plane for a certain distance after rotation.

[0014] Furthermore, in step 3, based on the point cloud data in different positions and postures, the actual measurement value is obtained by feature search to determine the four feature points on the calibration plate.

[0015] Furthermore, in step 4, a model including a hand-eye calibration matrix is ​​established according to the relationship between the robot base coordinate system, the robot end coordinate system, and the line laser profiler measurement data. The specific process is as follows: The position expression of the calibration plate coordinate system in the robot base coordinate system is as follows: in represents the transformation matrix from the machine base coordinate system to the robot end coordinate system under different postures, which is obtained by the robot controller. X represents the transformation matrix from the robot end to the camera coordinate system, and C Indicates that the camera measures the i Measurement data of feature points of the secondary calibration plate; make ; ; ; ; And bring it into the position expression, the change result is as follows: make , The final expression of the hand-eye calibration matrix model is as follows: Represents the transformation matrix from the robot end coordinate system to the line laser profiler coordinate system, represents the rotation matrix, represents the translation vector, and the transformation matrix X is the hand-eye calibration matrix; The model is solved by the Tsai-Lenz method to obtain the final transformation matrix from the robot end to the camera coordinate system.

[0016] Furthermore, the hand-eye calibration matrix is ​​expressed as: in, Represents the second rotation matrix The corresponding unit quaternion is, Represents the second translation vector ,in, All are real numbers.

[0017] Compared with the prior art, the present invention has the following beneficial effects: A simple calibration plate is used as an intermediate marker to improve the efficiency of hand-eye calibration between the line laser profiler and the robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the hand-eye calibration device of the centerline laser profilometer of the present invention; Figure 2 It is a structural schematic diagram of the calibration plate in the present invention; Figure 3 This is a flow chart of the hand-eye calibration of the line laser profiler provided in the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] A hand-eye calibration device for a line laser profiler Figure 1 As shown, including: Robot system 1: including a multi-degree-of-freedom robotic arm, a fixed base and a motion controller, capable of performing positioning and movement tasks in space according to instructions, and an interface for fixing a line laser profiler is installed at the end of the robotic arm; Line laser profiler 2: fixed on the end effector of the robot and rotatable, used to emit a linear laser beam and receive reflected light, and measure the data of the surface profile of the object by analyzing the reflected light information; The calibration plate 3 comprises a rectangular flat plate 31 as a base and an isosceles trapezoidal block 32 erected on the rectangular flat plate.

[0021] Among them, the structure of the calibration plate 3 is as follows Figure 2 As shown, the isosceles trapezoidal block 32 is formed by splicing two isosceles trapezoidal plates of the same shape and a bottom angle block of 45°, and the splicing surface is a trapezoidal surface in space and has four vertices 321, 322, 323 and 324; The isosceles trapezoidal block 32 is arranged at the central position of the rectangular flat plate 31, and is fixed to the rectangular flat plate 31 with the end surface where the bottom edge of the isosceles trapezoidal block 32 is located as a fixing surface, and the projection line of the splicing surface of the isosceles trapezoidal block 32 on the rectangular flat plate 31 coincides with the line connecting the midpoints of the two parallel sides of the rectangular flat plate 31.

[0022] exist Figure 1 In the hand-eye calibration device of the line laser profiler shown, there are a robot base coordinate system 4, a robot end coordinate system 5 and a line laser profiler coordinate system 6; When a point in the robot end coordinate system 5 is converted to the robot base coordinate system 4, it is represented by a first transformation matrix [R, T]; When a point in the line laser profiler coordinate system 6 is converted to the robot end coordinate system 5, it is represented by the second transformation matrix [r, t].

[0023] like Figure 3 As shown, a line laser profiler hand-eye calibration method is implemented by the line laser profiler hand-eye calibration device as described above, comprising: Step 1: Place the calibration plate in a fixed position and fix the line laser profiler at the end of the robot; Step 2: Control the robot arm through the motion controller to drive the line laser profiler to align with the isosceles trapezoid of the calibration plate, and record the position and posture matrix of the robot TCP as the first matrix; Step 3: The line laser profiler collects the point cloud data of the isosceles trapezoid, and extracts the coordinate values ​​of the four vertex features in the line laser profiler coordinate system through feature search, and uses the coordinate values ​​measured by the four vertex features as the second matrix; Step 4: transform multiple postures of the robot to obtain a first matrix of multiple groups of robot TCP positions and a second matrix of calibration plate feature points under corresponding postures; Step 5: Based on the relationship between the robot base coordinate system, the robot end coordinate system and the line laser profiler coordinate system, a model including the hand-eye calibration matrix is ​​established, and the model is solved by combining the multiple sets of first matrices and second matrices obtained in step 4.

[0024] In step 2, the motion controller controls the robot arm to drive the line laser profiler to align and scan the calibration plate to obtain the coordinate data of the feature points of the robot in different positions, including: The motion controller drives the robotic arm so that the line laser beam emitted by the line laser profiler at the end of the robotic arm coincides with the engraved lines of the isosceles trapezoidal block on the calibration plate, and the calibration plate is scanned to obtain the point cloud data of the calibration plate; The position and posture of the robotic arm are adjusted through the motion controller, and the calibration plate point cloud data of the robotic arm in multiple positions is scanned.

[0025] In step 4, a model including a hand-eye calibration matrix is ​​established based on the relationship between the robot base coordinate system, the robot end coordinate system, and the line laser profiler measurement data. The specific process is as follows: The position expression of the calibration plate coordinate system in the robot base coordinate system is as follows: in represents the transformation matrix from the machine base coordinate system to the robot end coordinate system under different postures, which is obtained by the robot controller. X represents the transformation matrix from the robot end to the camera coordinate system, and C Indicates that the camera measures the i Measurement data of feature points of the secondary calibration plate; make ; ; ; ; And bring it into the position expression, the change result is as follows: make , The final expression of the hand-eye calibration matrix model is as follows: Represents the transformation matrix from the robot end coordinate system to the line laser profiler coordinate system, represents the rotation matrix, represents the translation vector, and the transformation matrix X is the hand-eye calibration matrix; The model is solved by the Tsai-Lenz method to obtain the final transformation matrix from the robot end to the camera coordinate system.

[0026] Furthermore, the hand-eye calibration matrix is ​​expressed as: in, Represents the second rotation matrix The corresponding unit quaternion is, Represents the second translation vector ,in, All are real numbers.

[0027] The hand-eye calibration matrix contains a total of 7 unknowns. Equations greater than the number of unknowns are established through point cloud data of multiple postures. In this embodiment, 9 equations can be established based on point cloud data of two postures to solve all unknowns in the hand-eye calibration matrix, further obtain the hand-eye calibration matrix, and complete the hand-eye calibration based on the line laser profilometer.

[0028] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the rights of the embodiments of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the embodiments of the present invention shall be within the scope of the rights of the embodiments of the present invention.

Claims

1. A line laser profiler hand-eye calibration device, characterized in that: include: Robot system: including a multi-degree-of-freedom robotic arm, a fixed base and a motion controller, capable of performing positioning and movement tasks in space according to instructions, and an interface for fixing a line laser profiler is installed at the end of the robotic arm; Line laser profiler: fixed on the end effector of the robot, used to emit a linear laser beam and receive reflected light, and measure the data of the surface profile of the object by analyzing the reflected light information; Calibration plate: includes a rectangular plate as a base and an isosceles trapezoidal block erected on the rectangular plate.

2. The hand-eye calibration device for a line laser profiler according to claim 1, characterized in that: The base angle of the isosceles trapezoidal block is 45°, and the waist and upper side are equal in length; The isosceles trapezoidal block is arranged at the central position of the rectangular flat plate, and is fixed to the rectangular flat plate with the end surface where the bottom edge of the isosceles trapezoidal block is located serving as a fixing surface.

3. The hand-eye calibration device of the line laser profiler according to claim 1 or 2, characterized in that: A 0.1 mm wide and 0.1 mm deep engraved line is set in the middle of the isosceles trapezoidal block for alignment with the laser emitted by the line laser profiler.

4. A line laser profiler hand-eye calibration method, characterized in that: The method is implemented by the hand-eye calibration device for a line laser profiler according to any one of claims 1 to 3, comprising: Step 1: Place the calibration plate in a fixed position and fix the line laser profiler at the end of the robot; Step 2: Control the robot arm through the motion controller to drive the line laser profiler to align with the isosceles trapezoid of the calibration plate, and record the position and posture matrix of the robot TCP as the first matrix; Step 3: The line laser profiler collects the point cloud data of the isosceles trapezoid, and extracts the coordinate values ​​of the four vertex features in the line laser profiler coordinate system through feature search, and uses the coordinate values ​​measured by the four vertex features as the second matrix; Step 4: transform multiple postures of the robot to obtain a first matrix of multiple groups of robot TCP positions and a second matrix of calibration plate feature points under corresponding postures; Step 5: Based on the relationship between the robot base coordinate system, the robot end coordinate system and the line laser profiler coordinate system, a model including the hand-eye calibration matrix is ​​established, and the model is solved by combining the multiple sets of first matrices and second matrices obtained in step 4.

5. The hand-eye calibration method of a line laser profiler according to claim 4, characterized in that: In step 2, the robot arm is controlled by the motion controller to drive the line laser profiler to align and scan the calibration plate to obtain the coordinate data of the feature points of the robot in different positions, including: The motion controller drives the robotic arm so that the line laser beam emitted by the line laser profiler at the end of the robotic arm coincides with the engraved lines of the isosceles trapezoidal block on the calibration plate, and the calibration plate is scanned to obtain the point cloud data of the calibration plate; The position and posture of the robotic arm are adjusted through the motion controller, and the calibration plate point cloud data of the robotic arm in multiple positions is scanned.

6. The line laser profiler hand-eye calibration method according to claim 5, characterized in that: The posture of the robot arm is represented by a transformation matrix between coordinate systems, including a rotation matrix and a translation vector in three-dimensional space; the multiple postures represent at least four postures; The point cloud data includes four scanning results obtained in the same posture, namely, the scanning result of the line laser profiler at the initial position, the scanning result of the initial position translated along the trapezoidal plane for a certain distance, the scanning result after the line laser profiler is rotated 180°, and the result of being translated along the trapezoidal plane for a certain distance after rotation.

7. The hand-eye calibration method of a line laser profiler according to claim 4, characterized in that: In step 4, a model including a hand-eye calibration matrix is ​​established according to the relationship between the robot base coordinate system, the robot end coordinate system, and the line laser profiler measurement data. The specific process is as follows: The position expression of the calibration plate coordinate system in the robot base coordinate system is as follows: in represents the transformation matrix from the machine base coordinate system to the robot end coordinate system under different postures, which is obtained by the robot controller. X represents the transformation matrix from the robot end to the camera coordinate system, and C Indicates that the camera measures the i Measurement data of feature points of the secondary calibration plate; make ; ； ； ； And bring it into the position expression, the change result is as follows: make , The final expression of the hand-eye calibration matrix model is as follows: Represents the transformation matrix from the robot end coordinate system to the line laser profiler coordinate system, represents the rotation matrix, represents the translation vector, and the transformation matrix X is the hand-eye calibration matrix; The model is solved by the Tsai-Lenz method to obtain the final transformation matrix from the robot end to the camera coordinate system.

8. The hand-eye calibration method of a line laser profiler according to claim 4, characterized in that: The hand-eye calibration matrix is ​​expressed as: in, Represents the second rotation matrix The corresponding unit quaternion is, Represents the second translation vector ,in, All are real numbers.

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