Tool coordinate system calibration method for mechanical arm of collaborative robot

Abstract

The invention relates to the field of robot positioning, in particular to a tool coordinate system calibration method for mechanical arms of a collaborative robot, which accurately obtains 6D poses of multiple groups of mechanical arms of the collaborative robot by changing the poses of the robot and performing plane estimation and definition analysis on calibration plate data acquired by a camera, and determines the tool coordinate system of the mechanical arms of the collaborative robot based on the 6D poses of the multiple groups of mechanical arms. And the transformation matrix of the tool coordinate system relative to the base coordinate system is obtained, so that the calibration accuracy of the tool coordinate system can be improved. Moreover, under the condition that a high-precision three-coordinate instrument is not used, the tool coordinate system of the collaborative robot can be accurately calibrated, the economic cost of calibration of the working coordinate system is reduced, and the calibration efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of robot positioning, and in particular to a method for calibrating a tool coordinate system of a collaborative robot arm. Background Art

[0002] Collaborative robots combined with vision systems can assist humans in completing mechanical work, giving full play to the efficiency of robots and the accuracy of vision. In practical applications, due to the limitations of process and mechanical mechanisms, a new tool coordinate system is often customized. The tool coordinate system is a coordinate system used to define the position of the tool center point (TCP) and the tool posture.

[0003] The traditional method of calibrating the tool coordinate system is to adjust the different postures of the collaborative robot, align the end with the same reference point, and calculate the calibrated tool coordinate system. However, this method is affected by the end structure processing accuracy and human subjective factors, resulting in large errors in the newly created tool coordinates. In some high-precision, high-detection accuracy applications, it cannot be actually used. In order to pursue a higher-precision tool coordinate system, a high-precision three-coordinate instrument is also used for auxiliary calibration, but this instrument is expensive and is often not purchased for use in actual projects.

[0004] Therefore, how to accurately calibrate the tool coordinate system of the collaborative robot arm is an urgent problem to be solved. Summary of the invention

[0005] The present application provides a method for calibrating the tool coordinate system of a collaborative robot arm. By changing the robot's posture, plane estimation and clarity analysis are performed on the calibration plate data collected by the camera to obtain the 6D posture of multiple groups of collaborative robot arms. Based on the 6D posture of the multiple groups of arms, the transformation matrix of the tool coordinate system relative to the base coordinate system is obtained, which can improve the accuracy of the tool coordinate system calibration.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] In a first aspect, the present invention provides a method for calibrating a tool coordinate system of a collaborative robot manipulator, the method comprising:

[0008] Obtain the positional relationship between the camera and the collaborative robot;

[0009] Establish a contour feature model of the marker and obtain multiple calibration plate images with the marker;

[0010] Based on the contour feature model, a contour matching algorithm is used to determine the position and direction of the marker in the calibration plate image;

[0011] Generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot so that the marker is located at the center of the camera, and then send a second movement instruction to move the robot arm along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction;

[0012] Performing clarity evaluation on the plurality of calibration plate images having the same position and orientation of the markers, and selecting the calibration plate image with the highest clarity as the pose image;

[0013] Obtaining a 6D posture of the robotic arm when the robotic arm captures the posture image;

[0014] Based on the 6D postures of the multiple robotic arms and in combination with the positional relationship, the tool coordinate system is calibrated.

[0015] In a preferred example of the present application, it can be further configured that the 6D postures of the plurality of robotic arms, combined with the positional relationship, calibrate the tool coordinate system, including:

[0016] Based on the 6D postures of more than four robotic arms and in combination with the positional relationship, the tool coordinate system is calibrated.

[0017] In a preferred example of the present application, it can be further configured that the acquiring the positional relationship between the camera and the collaborative robot includes:

[0018] Convert the coordinate systems of the camera and collaborative robot to the world coordinate system and obtain the transformation matrix of the two coordinate systems.

[0019] In a preferred example of the present application, it can be further configured to perform clarity evaluation on the plurality of calibration plate images with the markers having the same position and orientation, including:

[0020] An edge detection algorithm is used to perform clarity assessment on the plurality of calibration plate images in which the markers have the same position and orientation.

[0021] In a preferred example of the present application, it can be further configured that the clarity evaluation is performed on the plurality of calibration plate images having the same position and direction of the markers using an edge detection algorithm, including:

[0022] An edge detection algorithm is used to evaluate the sharpness of the stripes of the plurality of stripe groups in each quadrant of the plurality of calibration plate images in which the markers have the same position and orientation.

[0023] In a preferred example of the present application, it can be further configured to include:

[0024] In combination with the sharpness, calculating the variance value of the stripe width in each stripe group of the calibration plate image;

[0025] The sharpness is evaluated based on the variance value and the sharpness of the fringes.

[0026] In a second aspect, the present application provides a tool coordinate system calibration device for a collaborative robot manipulator, the device comprising:

[0027] A position acquisition module is used to obtain the position relationship between the camera and the collaborative robot;

[0028] A contour recognition module is used to establish a contour feature model of the marker and obtain multiple calibration plate images with the marker; based on the contour feature model, a contour matching algorithm is used to determine the position and direction of the marker in the calibration plate image;

[0029] A clarity evaluation module is used to generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot to make the marker located at the center of the camera, and then send a second movement instruction to make the robot arm move along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction; perform clarity evaluation on the multiple calibration plate images with the marker having the same position and direction, and select the calibration plate image with the highest clarity as the posture image;

[0030] A path planning module is used to plan the path of the end effector based on the first six-dimensional coordinate and the second six-dimensional coordinate by using an inverse kinematics algorithm to obtain a rotation angle and a rotation direction of the wrist joint, wherein the rotation direction is a clockwise direction or a counterclockwise direction;

[0031] A calibration module is used to obtain the 6D posture of the robotic arm when the robotic arm is shooting the posture image; based on the 6D postures of multiple robotic arms and combined with the position relationship, calibrate the tool coordinate system.

[0032] In a third aspect, the present application provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the tool coordinate system calibration method for a collaborative robot manipulator arm as described in any one of the above items are implemented.

[0033] In a fourth aspect, the present application provides a computer-readable storage medium having a program stored thereon, wherein when the program is executed by a processor, a tool coordinate system calibration method for a collaborative robot manipulator arm as described in any one of the above items is implemented.

[0034] In a fifth aspect, the present application provides a computer program product, comprising computer instructions, which, when executed by a processor, implement the steps of the tool coordinate system calibration method for a collaborative robot manipulator as described in any one of the above items.

[0035] In summary, compared with the prior art, the technical solution provided in the embodiment of the present application has at least the following beneficial effects:

[0036] The present application provides a method for calibrating the tool coordinate system of a collaborative robot manipulator. By changing the robot's posture, the calibration plate data collected by the camera is estimated and analyzed for clarity, and the 6D posture of multiple groups of collaborative robot manipulators is accurately obtained. Based on the 6D posture of multiple groups of manipulators, the transformation matrix of the tool coordinate system relative to the base coordinate system is obtained, which can improve the accuracy of the tool coordinate system calibration. Moreover, the collaborative robot tool coordinate system can be accurately calibrated without using a high-precision three-coordinate instrument, which not only reduces the economic cost of the work coordinate system calibration, but also improves the calibration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flowchart of a tool coordinate system calibration method for a collaborative robot manipulator is provided in accordance with one embodiment of the present application.

[0038] Figure 2 A calibration board diagram of a tool coordinate system calibration method for a collaborative robot manipulator arm provided in one embodiment of the present application.

[0039] Figure 3 A structural diagram of a tool coordinate system calibration device for a collaborative robot arm provided in one embodiment of the present application. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] In one embodiment of the present application, a method for calibrating a tool coordinate system of a collaborative robot manipulator is provided. Figure 1 As shown, the method includes:

[0042] S100: Acquire the positional relationship between the camera and the collaborative robot;

[0043] Specifically, the camera is fixed on the robotic arm of the collaborative robot. After the positional relationship between the camera and the collaborative robot is determined by hand-eye calibration, this positional relationship is obtained, and at the same time, the camera coordinate system and the coordinate system of the collaborative robot are converted to the world coordinate system.

[0044] In a preferred embodiment, the coordinate systems of the camera and the collaborative robot are converted to the world coordinate system to obtain the transformation matrix of the two coordinate systems.

[0045] S200: Establishing a contour feature model of the marker and acquiring multiple calibration plate images with the marker;

[0046] Specifically, Figure 2 As shown, the marker is an irregular ellipse and is located in the middle of the calibration plate. After the contour feature model of the marker is established, the posture of the collaborative robot is adjusted to move the robotic arm to different positions so that the camera can take images of the calibration plate at different angles. Then, multiple images of the calibration plate with the marker at different positions are obtained.

[0047] S300: Based on the contour feature model, using a contour matching algorithm to determine the position and direction of the marker in the calibration plate image;

[0048] Specifically, a contour matching algorithm is used to identify the contour of the marker in each marked plate image, and the position of the center point of the marker and the plane coordinate system direction of the marker are obtained.

[0049] S400: Generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot, so that the marker is located at the center of the camera, and then send a second movement instruction to move the robot arm along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction;

[0050] Specifically, the first movement instruction is an instruction for controlling the movement of the robot arm of the collaborative robot, which is calculated based on the position and direction in the calibration plate image. The second movement instruction is an instruction for controlling the robot arm of the collaborative robot to move along the optical axis of the camera. At this time, the marker is already at the center point of the camera, and moving along the optical axis will not change the position and direction of the marker. When the robot arm moves along the optical axis, multiple shooting instructions are sent to the camera to obtain multiple calibration plate images in which the marker has the same position and direction.

[0051] S500: Evaluate the clarity of the plurality of calibration plate images having the same position and orientation of the markers, and select the calibration plate image with the highest clarity as the pose image;

[0052] Specifically, the clarity evaluation algorithm is used to evaluate the calibration plate image, such as Figure 2 As shown, the calibration plate is divided into four quadrants and has multiple fringe groups.

[0053] In a preferred embodiment, an edge detection algorithm is used to perform clarity assessment on the plurality of calibration plate images in which the markers have the same position and orientation.

[0054] The accuracy of sharpness assessment is improved by using edge detection algorithms.

[0055] S600: Acquire the 6D posture of the robotic arm when the robotic arm captures the posture image;

[0056] Specifically, the 6D posture of the robotic arm in the teaching software is obtained when the robotic arm shoots the posture image.

[0057] S700: Calibrate the tool coordinate system based on the 6D postures of the multiple robotic arms and the positional relationship.

[0058] Specifically, the relative motion between the known robot base coordinate system and the tool coordinate system can be calculated through multiple sets of 6D pose data of the robot and the origin position and direction data of the tool coordinate system, and the transformation matrix of the tool coordinate system relative to the robot base coordinate system.

[0059] In this embodiment, by changing the robot's posture, plane estimation and clarity analysis are performed on the calibration plate data collected by the camera, and the 6D posture of multiple sets of collaborative robot manipulators is accurately obtained. Based on the 6D posture of multiple sets of manipulators, the transformation matrix of the tool coordinate system relative to the base coordinate system is obtained, which can improve the accuracy of the tool coordinate system calibration. Moreover, the collaborative robot tool coordinate system can be accurately calibrated without using a high-precision three-coordinate instrument, which not only reduces the economic cost of the work coordinate system calibration, but also improves the calibration efficiency.

[0060] In some embodiments, the 6D poses of the plurality of robotic arms combined with the positional relationship to calibrate the tool coordinate system includes:

[0061] Based on the 6D postures of more than four robotic arms and in combination with the positional relationship, the tool coordinate system is calibrated.

[0062] In this embodiment, the accuracy of the calibration tool coordinate system is improved.

[0063] In some embodiments, using an edge detection algorithm to perform clarity assessment on the plurality of calibration plate images having the same position and orientation of the markers includes:

[0064] An edge detection algorithm is used to evaluate the sharpness of the stripes of the plurality of stripe groups in each quadrant of the plurality of calibration plate images in which the markers have the same position and orientation.

[0065] When implementing it, Figure 2 As shown, the stripe group is a combination of parallel-arranged stripes in each quadrant of the figure, and each quadrant has multiple groups of stripes in different directions.

[0066] In this embodiment, the accuracy of the calibration tool coordinate system is improved.

[0067] In some embodiments, it also includes:

[0068] In combination with the sharpness, calculating the variance value of the stripe width in each stripe group of the calibration plate image;

[0069] The sharpness is evaluated based on the variance value and the sharpness of the fringes.

[0070] During specific implementation, the clarity is the ratio of the variance value to the sharpness.

[0071] In this embodiment, the accuracy of the calibration tool coordinate system is improved.

[0072] This application also provides a tool coordinate system calibration device for a collaborative robot manipulator. Figure 3 As shown, the device comprises:

[0073] A position acquisition module 100 is used to acquire the position relationship between the camera and the collaborative robot;

[0074] The contour recognition module 200 is used to establish a contour feature model of the marker and obtain multiple calibration plate images with the marker; based on the contour feature model, a contour matching algorithm is used to determine the position and direction of the marker in the calibration plate image;

[0075] The clarity evaluation module 300 is used to generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot to make the marker located at the center of the camera, and then send a second movement instruction to make the robot arm move along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction; perform clarity evaluation on the multiple calibration plate images with the marker having the same position and direction, and select the calibration plate image with the highest clarity as the posture image;

[0076] A path planning module 400 is used to plan the path of the end effector based on the first six-dimensional coordinate and the second six-dimensional coordinate by using an inverse kinematics algorithm to obtain a rotation angle and a rotation direction of the wrist joint, wherein the rotation direction is a clockwise direction or a counterclockwise direction;

[0077] The calibration module 500 is used to obtain the 6D posture of the robotic arm when the robotic arm is shooting the posture image; based on the 6D postures of multiple robotic arms and combined with the position relationship, calibrate the tool coordinate system.

[0078] The functional implementation of each module in the tool coordinate system calibration device of the above-mentioned collaborative robot manipulator corresponds to the steps in the embodiment of the tool coordinate system calibration method of the above-mentioned collaborative robot manipulator, and its functions and implementation processes will not be repeated here one by one.

[0079] The present application also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the tool coordinate system calibration method for the collaborative robot manipulator arm as described in any of the above embodiments are implemented.

[0080] The present application also provides a computer-readable storage medium, on which a program is stored, wherein the computer-readable storage medium refers to a carrier for storing data, which may include but is not limited to a floppy disk, an optical disk, a hard disk, a flash memory, a USB flash drive and / or a memory stick, etc., and the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The working process, working details and technical effects of the computer-readable storage medium provided in this embodiment can be found in the embodiment of a tool coordinate system calibration method for a collaborative robot manipulator arm above, and will not be repeated here.

[0081] The application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the steps of the tool coordinate system calibration method of the collaborative robot manipulator as described in any of the above embodiments.

[0082] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in the present application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0083] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-mentioned embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several deformations and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of this application shall be based on the attached claims.

Claims

1. A method for calibrating a tool coordinate system of a collaborative robot arm, characterized in that: include: Obtain the positional relationship between the camera and the collaborative robot; Establish a contour feature model of the marker and obtain multiple calibration plate images with the marker; Based on the contour feature model, a contour matching algorithm is used to determine the position and direction of the marker in the calibration plate image; Generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot so that the marker is located at the center of the camera, and then send a second movement instruction to move the robot arm along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction; Performing clarity evaluation on the plurality of calibration plate images having the same position and orientation of the markers, and selecting the calibration plate image with the highest clarity as the pose image; Obtaining a 6D posture of the robotic arm when the robotic arm captures the posture image; Based on the 6D postures of the multiple robotic arms and in combination with the positional relationship, the tool coordinate system is calibrated.

2. The tool coordinate system calibration method of the collaborative robot manipulator according to claim 1, characterized in that: The 6D postures of the plurality of robotic arms are combined with the positional relationship to calibrate the tool coordinate system, including: Based on the 6D postures of more than four robotic arms and in combination with the positional relationship, the tool coordinate system is calibrated.

3. The tool coordinate system calibration method of the collaborative robot manipulator according to claim 1, characterized in that: The obtaining of the positional relationship between the camera and the collaborative robot comprises: Convert the coordinate systems of the camera and collaborative robot to the world coordinate system and obtain the transformation matrix of the two coordinate systems.

4. The tool coordinate system calibration method of the collaborative robot manipulator according to claim 1, characterized in that: Performing clarity evaluation on the plurality of calibration plate images having the same position and orientation of the markers, comprising: An edge detection algorithm is used to perform clarity assessment on the multiple calibration plate images in which the markers have the same position and orientation.

5. The tool coordinate system calibration method of the collaborative robot manipulator according to claim 4, characterized in that: Using an edge detection algorithm to perform clarity assessment on the plurality of calibration plate images having the same position and orientation of the markers, comprising: An edge detection algorithm is used to evaluate the sharpness of the stripes of the plurality of stripe groups in each quadrant of the plurality of calibration plate images in which the markers have the same position and orientation.

6. The tool coordinate system calibration method of the collaborative robot manipulator according to claim 5, characterized in that: Also includes: In combination with the sharpness, calculating the variance value of the stripe width in each stripe group of the calibration plate image; The sharpness is evaluated based on the variance value and the sharpness of the fringes.

7. A tool coordinate system calibration device for a collaborative robot manipulator, characterized in that: include: A position acquisition module is used to obtain the position relationship between the camera and the collaborative robot; A contour recognition module is used to establish a contour feature model of the marker and obtain multiple calibration plate images with the marker; based on the contour feature model, a contour matching algorithm is used to determine the position and direction of the marker in the calibration plate image; A clarity evaluation module is used to generate a first movement instruction based on the position and direction in the calibration plate image, send the movement instruction to the collaborative robot to make the marker located at the center of the camera, and then send a second movement instruction to make the robot arm move along the optical axis direction of the camera, and send multiple shooting instructions to the camera during the movement to obtain multiple calibration plate images with the marker having the same position and direction; Performing clarity evaluation on the plurality of calibration plate images having the same position and orientation of the markers, and selecting the calibration plate image with the highest clarity as the pose image; A path planning module is used to plan the path of the end effector based on the first six-dimensional coordinate and the second six-dimensional coordinate by using an inverse kinematics algorithm to obtain a rotation angle and a rotation direction of the wrist joint, wherein the rotation direction is a clockwise direction or a counterclockwise direction; A calibration module is used to obtain the 6D posture of the robotic arm when the robotic arm is shooting the posture image; based on the 6D postures of multiple robotic arms and combined with the position relationship, calibrate the tool coordinate system.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the tool coordinate system calibration method of the collaborative robot manipulator arm as described in any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a program, wherein when the program is executed by the processor, the tool coordinate system calibration method of the collaborative robot manipulator arm according to any one of claims 1 to 6 is implemented.

10. A computer program product comprising computer instructions, characterized in that: When executed by a processor, the computer instructions implement the steps of the tool coordinate system calibration method of the collaborative robot manipulator arm described in claims 1 to 6.

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