Welding mechanical arm TCP calibration device based on checkerboard calibration and calibration method thereof

Abstract

The invention relates to the technical field of robots, in particular to a welding mechanical arm TCP calibration device based on checkerboard calibration and a calibration method thereof.The method comprises the following steps that according to hand-eye calibration, a pose conversion matrix of a camera coordinate system relative to a mechanical arm base coordinate system is calculated; shooting a checkerboard on the TCP calibrator by using a camera, and obtaining a pose conversion matrix of a checkerboard coordinate system relative to a camera coordinate system; determining a pose conversion matrix of the welding tail end relative to the checkerboard center according to the three-dimensional model; and according to the pose conversion relation between the TCP calibrator and the mechanical arm base coordinate system, the pose of the tail end of the welding wire of the welding gun in the mechanical arm base coordinate system is obtained. The efficiency and convenience of the calibration process are remarkably improved only through simple operation of installing the calibrator and collecting the coordinates of the feature points; the camera is used for recording the feature points on the TCP calibrator, the position and the posture of the tail end of the welding wire of the welding gun can be accurately determined, the influence on the TCP calibration precision is avoided, and the calibration precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of robots, and in particular to a welding robot arm TCP calibration device based on chessboard calibration and a calibration method thereof. Background Art

[0002] In the field of modern industrial production, welding robot arms are key equipment for automated production and are increasingly used in various complex welding tasks. The positioning accuracy of the welding robot arm during the working process directly determines the welding quality and production efficiency, among which the accuracy of the tool center point (TCP) value plays a vital role. TCP is a key parameter of the robot arm's end effector (such as a welding gun), and its precise calibration is the core link to ensure that the welding robot arm can accurately perform welding tasks.

[0003] In current industrial practice, there are various methods for TCP calibration of robot welding guns, among which the four-point calibration method is widely used because of its relatively simple operation. However, as the requirements for welding accuracy and efficiency in industrial production continue to increase, the four-point calibration method has gradually exposed a series of limitations and has been unable to meet actual needs in certain specific scenarios.

[0004] First, from the perspective of accuracy, although the four-point calibration method is relatively simple in terms of operation process, its accuracy is easily affected by a combination of factors during the actual calibration process. On the one hand, the robot arm itself will inevitably produce motion errors during the movement process, such as wear of the mechanical structure, clearance of the transmission components, and accuracy limitations of the control system. These factors will cause deviations between the actual position and theoretical position of the end of the robot arm. On the other hand, the measurement errors in the calibration process cannot be ignored, such as the accuracy of the measuring tool, the stability of the measuring environment, and human reading errors, which will have an adverse effect on the final TCP calibration accuracy. Therefore, the four-point calibration method is often difficult to achieve the required accuracy standards in these high-precision control scenarios.

[0005] Secondly, the four-point calibration method is highly dependent on manual operation. During the calibration process, the operator is required to manually select fixed position points and manually control the posture of the robot arm so that the TCP tip at the end of the robot arm approaches but does not touch these fixed reference points. This operation method not only increases the complexity of the operation and requires high skills and experience of the operator, but also easily introduces additional error risks due to the uncertainty of manual operation itself, prolongs the time of the calibration process, and increases costs. The intervention of manual operation challenges the stability and repeatability of the calibration results.

[0006] In addition, the four-point calibration method has obvious limitations in environmental adaptability. In actual industrial production environments, there are often various complex working conditions, such as narrow space and obstacles. In these restricted environments, the application of the four-point calibration method will be greatly limited. This is because the method requires the robot arm to have sufficient movement space and posture change capabilities so that it can accurately coincide with the pre-set fixed position points. These conditions may be difficult to meet in a restricted environment.

[0007] In summary, although the four-point calibration method has a certain application basis in the field of robot arm welding gun TCP calibration, as industrial production develops towards high precision, high efficiency and complex environment, its limitations such as accuracy limitation, strong dependence on manual operation and poor environmental adaptability have become increasingly prominent, which severely restricts the application of this method in some key application scenarios. Therefore, it is urgent to explore a more accurate, efficient and environmentally adaptable TCP calibration method to improve the working performance of the welding robot arm and meet the growing demand of modern industrial production for welding quality and production efficiency. Summary of the invention

[0008] The purpose of the present invention is to overcome the above problems or at least partially solve the above problems, and to propose a welding robot arm TCP calibration device based on chessboard calibration and a calibration method thereof.

[0009] To achieve the above object, the present invention provides the following technical solution: a TCP calibration device for a welding robot arm based on chessboard calibration, comprising:

[0010] The TCP calibrator body is used to be fixedly installed on the end of the welding gun of the welding robot arm;

[0011] A checkerboard component is fixedly arranged on the TCP calibrator body, and the checkerboard component includes a plurality of checkerboard units, which are used to provide feature point information for the camera to perform pose calculation;

[0012] A sleeve, arranged on the TCP marker body, the sleeve is used to be sleeved on the welding gun, and the sleeve is provided with a fixing structure for fixing the relative position of the TCP marker body and the welding gun;

[0013] The welding wire penetration structure is arranged at the bottom of the sleeve, and the welding wire penetration structure includes a small hole for the welding wire of the welding gun to pass through.

[0014] In a preferred embodiment, the number of checkerboard units in the checkerboard component is three, and the three checkerboard units are distributed on the TCP calibrator body, and the checkerboard pattern of each checkerboard unit has a regular geometric shape and known size parameters to facilitate the camera to accurately identify and calculate the pose transformation matrix.

[0015] In a preferred embodiment, the fixing structure is a throat clamp, which can adjust the tightness to adapt to welding guns of different specifications, and can maintain the relative position between the TCP calibrator body and the welding gun stable after fixation to avoid displacement or shaking during the calibration process.

[0016] A welding robot arm TCP calibration method based on chessboard calibration, the method is applied to the welding robot arm TCP calibration device based on chessboard calibration as mentioned above, comprising the following steps:

[0017] Step 1: Calculate the pose transformation matrix of the camera coordinate system relative to the robot base coordinate system based on the hand-eye calibration;

[0018] Step 2: Fix the TCP calibration device to the end of the welding gun, use the camera to shoot the checkerboard on the TCP calibrator, and obtain the pose transformation matrix of the checkerboard coordinate system relative to the camera coordinate system;

[0019] Step 3: Determine the posture transformation matrix of the end of the welding gun relative to the center of the chessboard according to the three-dimensional model;

[0020] Step 4: According to the posture conversion relationship between the TCP calibrator and the robot base coordinate system, the posture of the welding wire end of the welding gun in the robot base coordinate system is obtained.

[0021] In a preferred embodiment, in step 4, after obtaining the pose matrix of the welding gun wire end in the robot arm base coordinate system, the obtained pose matrix is ​​subjected to mean filtering to reduce the calibration error, and finally the welding gun TCP is obtained.

[0022] In a preferred embodiment, in step 4, the posture transformation matrix of the welding gun wire end relative to the checkerboard coordinate system is determined by the calibrator mechanical structure and the wire stem extension length, and the posture transformation matrix of the welding gun end relative to the checkerboard coordinate system is:

[0023] in Determined by the mechanical structure of the calibrator, Determined by the wire extension, E3 is the unit matrix, z is the wire extension length.

[0024] In a preferred embodiment, in the step 2, when the number of checkerboard grids on the TCP calibrator is three, the camera is used to respectively obtain the pose transformation matrices of the three checkerboard grid coordinate systems relative to the camera coordinate system.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention optimizes the calibration steps, which originally required the teaching robot arm to move to four different positions, and at each position the TCP tip must be close to but not touch a fixed reference point, to a simple operation of only installing a calibrator and collecting feature point coordinates, thereby significantly improving the efficiency and convenience of the calibration process.

[0027] 2. The present invention uses a camera to record the feature points on the TCP calibrator. By accurately identifying and analyzing these feature points, the position and posture of the end of the welding gun wire can be accurately determined. Compared with the traditional method, the influence of the motion error of the robot arm itself during the movement on the TCP calibration accuracy is avoided, and the calibration accuracy is improved.

[0028] 3. The calibrator of the present invention adopts a design on which a checkerboard is fixed, and the calibrator is fixed to the end of the welding gun through a specific structure. This design makes the manufacturing process of the calibrator relatively simple, and does not require complicated processing technology and high-precision assembly requirements. At the same time, in actual operation, the operator only needs to install the calibrator on the end of the welding gun, and there is no need for complicated adjustments and calibrations, which reduces the difficulty of operation and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a three-view and three-dimensional structural schematic diagram of the TCP calibration device of the present invention;

[0030] Figure 2 Schematic diagram of the posture conversion relationship between various coordinate systems of the present invention;

[0031] Figure 3 It is a calibration flow chart of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-3 The present invention provides a technical solution: a TCP calibration device for a welding robot arm based on chessboard calibration, comprising:

[0034] The TCP calibrator body is used to be fixedly installed on the end of the welding gun of the welding robot arm;

[0035] A checkerboard component is fixedly arranged on the TCP calibrator body. The checkerboard component includes a plurality of checkerboard units and is used to provide feature point information for the camera for pose calculation;

[0036] A sleeve is arranged on the TCP calibrator body. The sleeve is used to be sleeved on the welding gun, and a fixing structure for fixing the relative position of the TCP calibrator body and the welding gun is arranged on the sleeve. The fixing structure is a throat clamp. The throat clamp can adjust the tightness to adapt to welding guns of different specifications, and can keep the relative position between the TCP calibrator body and the welding gun stable after being fixed to avoid displacement or shaking during the calibration process;

[0037] The welding wire penetration structure is arranged at the bottom of the sleeve, and the welding wire penetration structure comprises a small hole for allowing the welding wire of the welding gun to pass through.

[0038] In a specific implementation, the number of checkerboard units in the checkerboard component is three, and the three checkerboard units are distributed on the TCP calibrator body. The checkerboard pattern of each checkerboard unit has a regular geometric shape and known size parameters to facilitate the camera to accurately identify and calculate the pose transformation matrix.

[0039] In a specific implementation, the inner diameter of the sleeve matches the outer diameter of a common welding gun, and the inner wall of the sleeve is provided with an anti-slip layer or a texture structure to increase the friction between the sleeve and the welding gun, further ensuring the stability of the fixation.

[0040] In specific implementation, the diameter of the small hole in the welding wire perforation structure is slightly larger than the diameter of the welding gun welding wire, and the inner wall of the small hole is smooth to avoid damage or interference to the welding wire during the passing process of the welding wire, while ensuring that the welding wire can pass smoothly.

[0041] In specific implementation, the TCP calibrator body is made of a lightweight material with certain strength and rigidity to reduce the impact on the movement performance of the welding robot arm, while ensuring that it will not be deformed by external forces during the calibration process, affecting the calibration accuracy.

[0042] In a specific implementation, the surface of the chessboard component is coated with a reflective coating or made of a reflective material, so that the camera can clearly capture the characteristic points of the chessboard under different lighting conditions, thereby improving the accuracy and reliability of calibration.

[0043] The present invention also provides a welding robot arm TCP calibration method based on chessboard calibration, comprising the following steps:

[0044] (1) Figure 2 As shown, according to the position transformation relationship between the calibrator and the robot base coordinate system Obtain the pose matrix of the welding gun wire end in the robot arm base coordinate system The three obtained pose matrices are used to reduce the calibration error by using mean filtering, and finally the welding gun TCP is obtained.

[0045] (2) According to the hand-eye calibration, the pose transformation matrix of the camera coordinate system relative to the robot base coordinate system is calculated as

[0046] (3) There are three chessboards distributed around the TCP calibrator body. The camera is used to obtain the pose transformation matrices of the three chessboard coordinate systems relative to the camera coordinate system:

[0047] (4) The TCP calibrator body is provided with a sleeve with a throat clamp and a small hole at the lower end. The calibrator is put on the welding gun and fixed by the throat clamp. The welding wire passes through the small hole. According to the mechanical structure of the calibrator, the posture transformation matrix of the end of the welding gun wire relative to the checkerboard coordinate system is: in Determined by the mechanical structure of the calibrator, Determined by the wire extension, where E3 is the unit matrix, z is the wire extension length.

[0048] In summary, the TCP calibration device and calibration method of the welding robot arm based on checkerboard calibration provided by the present invention realizes efficient and accurate calibration of the TCP of the welding robot arm through the carefully designed TCP calibrator body, checkerboard assembly, sleeve and welding wire perforation structure and other components. In the specific implementation process, the design details of each component fully consider various needs in practical applications, such as adapting to welding guns of different specifications, ensuring the smooth passage of welding wire, improving the recognition ability of the camera under different lighting conditions, and reducing the impact on the motion performance of the robot arm. At the same time, the calibration method effectively reduces the calibration error and improves the calibration accuracy through the calculation and mean filtering of a series of posture conversion matrices. The combination of this calibration device and its calibration method not only simplifies the calibration operation process and reduces manual operation errors, but also can better adapt to complex industrial production environments, and provides reliable technical support for the application of welding robot arms in high-precision welding tasks, and has significant practical value and broad application prospects.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A TCP calibration device for a welding robot arm based on chessboard calibration, characterized in that: Included are: The TCP calibrator body is used to be fixedly installed on the end of the welding gun of the welding robot arm; A checkerboard component is fixedly arranged on the TCP calibrator body, and the checkerboard component includes a plurality of checkerboard units, which are used to provide feature point information for the camera to perform pose calculation; A sleeve, arranged on the TCP marker body, the sleeve is used to be sleeved on the welding gun, and the sleeve is provided with a fixing structure for fixing the relative position of the TCP marker body and the welding gun; The welding wire penetration structure is arranged at the bottom of the sleeve, and the welding wire penetration structure includes a small hole for the welding wire of the welding gun to pass through.

2. The TCP calibration device for a welding robot arm based on checkerboard calibration according to claim 1, characterized in that: The number of checkerboard units in the checkerboard component is three, and the three checkerboard units are distributed on the TCP calibrator body. The checkerboard pattern of each checkerboard unit has a regular geometric shape and known size parameters, so that the camera can accurately identify and calculate the pose transformation matrix.

3. The TCP calibration device for a welding robot arm based on chessboard calibration according to claim 2, characterized in that: The fixing structure is a throat clamp, the tightness of which can be adjusted to adapt to welding guns of different specifications, and can keep the relative position between the TCP calibrator body and the welding gun stable after being fixed, avoiding displacement or shaking during the calibration process.

4. The TCP calibration device for a welding robot arm based on checkerboard calibration according to claim 3 is characterized in that: The surface of the chessboard component is coated with a reflective coating or is made of a reflective material.

5. A TCP calibration method for a welding robot arm based on chessboard calibration, characterized in that: The method is applied to the TCP calibration device of a welding robot arm based on checkerboard calibration as described in any one of claims 1 to 4, comprising the following steps: Step 1: Calculate the pose transformation matrix of the camera coordinate system relative to the robot base coordinate system based on the hand-eye calibration; Step 2: Fix the TCP calibration device to the end of the welding gun, use the camera to shoot the checkerboard on the TCP calibrator, and obtain the pose transformation matrix of the checkerboard coordinate system relative to the camera coordinate system; Step 3: Determine the posture transformation matrix of the end of the welding gun relative to the center of the chessboard according to the three-dimensional model; Step 4: According to the posture conversion relationship between the TCP calibrator and the robot base coordinate system, the posture of the welding wire end of the welding gun in the robot base coordinate system is obtained.

6. The TCP calibration method for a welding robot arm based on checkerboard calibration according to claim 5, characterized in that: In the step 4, after the pose matrix of the welding gun wire end in the robot arm base coordinate system is obtained, the obtained pose matrix is ​​subjected to mean filtering to reduce the calibration error, and finally the welding gun TCP is obtained.

7. The TCP calibration method for a welding robot arm based on chessboard calibration according to claim 6, characterized in that: In step 4, the posture transformation matrix of the welding gun wire end relative to the checkerboard coordinate system is determined by the calibrator mechanical structure and the wire stem extension length. The posture transformation matrix of the welding gun wire end relative to the checkerboard coordinate system is: in Determined by the mechanical structure of the calibrator, Determined by the wire extension, E3 is the unit matrix, z is the wire extension length.

8. The welding robot arm TCP calibration method based on chessboard calibration according to claim 7 is characterized in that: In the step 2, when the number of checkerboards on the TCP calibrator is three, the camera is used to respectively obtain the pose transformation matrices of the three checkerboard coordinate systems relative to the camera coordinate system.

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