Laser welding robot tool calibration method and system based on focus positioning compensation

Abstract

The present invention discloses a laser welding robot tool calibration method and system based on focus positioning compensation, which belongs to the field of laser welding technology, including: setting a robot tool tool1 in a robot geodetic coordinate system, and calibrating a tool parameter P0 at tool1; generating a laser indicator light co-focal with the welding laser, and adjusting the robot so that the focus of the laser indicator light is located at point O on the plane of a pre-set sensor, and then obtaining the coordinate position of tool1 as the initial position; after controlling the robot to rotate a certain angle around a rotation axis passing through the initial position, controlling the robot to translate so that the focus returns to point O, and obtaining the coordinate position of tool1 as a newly added position; after obtaining N≥3 newly added positions that are not coplanar, spherical fitting is performed together with the initial position, and a vector pointing to the center of the sphere from the initial position is calculated, and P0 is compensated by the vector to obtain the tool parameters in the robot system, and the calibration ends. The present invention can improve the calibration accuracy of the robot tool parameters at the focus.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser welding, and more specifically, relates to a laser welding robot tool calibration method and system based on focus positioning compensation. Background Art

[0002] Laser welding is a process in which a high-energy laser beam is irradiated on the workpiece, causing the working temperature to rise sharply, the workpiece to melt and reconnect to form a permanent connection. Compared with other welding processes, the laser welding process has the advantages of deep melting, fast speed, small deformation, low requirements for the welding environment, high power density, no influence of magnetic fields, not limited to conductive materials, no need for vacuum working conditions, and no X-rays generated during the welding process. It is widely used in the field of high-end precision manufacturing. Laser welding is generally bound to articulated robots. Compared with manual welding, welding robots can greatly reduce the labor production cost of welding and improve the degree of automatic and intelligent operation of welding work. Welding robots can automatically complete many kinds of welding actions in a certain working space, so they can automatically adjust the posture of each welder at will.

[0003] The laser welding process is closely related to the focal position of the laser beam. When setting the tool point of the welding robot, the focus of the laser beam is usually set to the tool point of the robot. However, when calibrating the robot's tool, since the focus of laser welding has no entity in space, the four-point method and six-point method of tool calibration of traditional robots are difficult to use for tool calibration of laser welding robots. Even if the focus is simulated by installing a tip on the laser welding head, the accuracy of the robot's tool point measured by traditional calibration methods such as the four-point method and the six-point method is still low and cannot be applied to high-precision laser welding robot systems, which limits the actual application of laser welding robots. Summary of the invention

[0004] In view of the defects of the prior art and the need for improvement, the present invention provides a laser welding robot tool calibration method and system based on focus positioning compensation, the purpose of which is to ensure that the posture change of the robot during the welding process does not affect the position of the laser focus, thereby improving the calibration accuracy of the robot tool parameters at the focus.

[0005] To achieve the above object, according to one aspect of the present invention, a laser welding robot tool calibration method based on focus positioning compensation is provided, comprising:

[0006] Rough calibration steps: set the robot tool in the robot earth coordinate system, record it as the setting tool tool1, and calibrate the tool parameter P0 at the setting tool tool1; set the tool coordinate system of tool tool1 to be the same or opposite to the direction of each coordinate axis of the robot earth coordinate system;

[0007] Initial positioning step: Generate a laser indicator light that is confocal with the welding laser, and adjust the robot so that the focus of the laser indicator light is located on the plane of the pre-set sensor. Then obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system and record it as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O;

[0008] Rotation and translation step: After controlling the robot to rotate a certain angle around the rotation axis passing through the initial position, control the robot to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the newly added position;

[0009] Compensation amount calculation steps: After executing the rotation and translation steps N times and obtaining N newly added positions that are not in the same plane, spherical fitting is performed on the initial position and the N newly added positions, and the vector pointing from the initial position to the center of the fitted sphere is calculated as the compensation amount; N≥3;

[0010] Compensation step: Use the compensation amount to compensate the tool parameter P0 to obtain the tool parameter in the robot system as the final calibration result.

[0011] Furthermore, in the compensation amount calculation step, when N newly added positions are obtained, the robot rotates around at least two rotation axes.

[0012] Furthermore, in the compensation amount calculation step, when the N newly added positions are obtained, the robot rotates around three rotation axes, and the three rotation axes are respectively parallel to the three coordinate axes of the robot's earth coordinate system.

[0013] Furthermore, N=3.

[0014] Furthermore, in the rough calibration step, the robot tool is set in the robot earth coordinate system by using a four-point method or a six-point method, that is, the tool tool1 is set, and a tool parameter P0 at the setting tool tool1 is calibrated.

[0015] Furthermore, in the compensation amount calculation step, the least square method is used to perform spherical fitting on the initial position and the N newly added positions.

[0016] According to another aspect of the present invention, a laser welding robot tool calibration system based on focus positioning compensation is provided, comprising:

[0017] A rough calibration module is used to set a robot tool in the robot earth coordinate system, which is recorded as the setting tool tool1, and calibrate a tool parameter P0 at the setting tool tool1; the tool coordinate system of the setting tool tool1 is in the same or opposite direction to the coordinate axes of the robot earth coordinate system;

[0018] A laser, used for generating a laser indicator light having a focal point concentric with the welding laser;

[0019] The sensor is arranged below the welding head;

[0020] The initial positioning module is used to adjust the robot so that the focus of the laser indicator light is located on the plane of the sensor, and then obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O;

[0021] The rotation and translation module is used to control the robot to rotate a certain angle around the rotation axis passing through the initial position, and then control the robot to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the newly added position;

[0022] The compensation amount calculation module is used to obtain N newly added positions that are not in the same plane using the rotation and translation module, perform spherical fitting on the initial position and the N newly added positions, and calculate the vector from the initial position to the center of the fitted sphere as the compensation amount; N≥3;

[0023] And a compensation module is used to compensate the tool parameter P0 with the compensation amount to obtain the tool parameter in the robot system as the final calibration result.

[0024] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0025] (1) After the tool parameters at the setting tool tool1 are obtained by calibrating the existing calibration method, the present invention obtains multiple coordinate positions of the setting tool tool1 by rotating the robot and then translating the robot to return the laser indicator light focus to its original position based on the relatively fixed spatial relationship between the laser indicator light focus and the setting tool tool1. Then, the focal position of the laser indicator light that is co-focal with the welding laser is obtained by spherical fitting, and then the vector pointing from the initial position of the setting tool tool1 to the laser indicator point focus is obtained. The vector is used as a compensation amount to compensate the tool parameters at the setting tool tool1 obtained by the existing calibration method, and the final calibration result is obtained, that is, the vector of the robot default tool tool0 pointing to the laser indicator light focus. Through compensation, the present invention can reduce the calibration error caused by the influence of the robot posture change on the focus position, and effectively improve the calibration accuracy of the robot tool parameters at the focus.

[0026] (2) The present invention obtains multiple coordinate positions of the setting tool tool1 by making the robot perform three single-axis rotations around the coordinate axis, which can ensure that the value of the focus in a certain direction remains unchanged after the rotation. Subsequently, only two directions need to be moved to return the focus to point O in the sensor plane, thereby simplifying the implementation of the translation operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a laser welding robot system provided by an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a robot setting tool tool1 provided in an embodiment of the present invention;

[0029] Figure 3 A flow chart of a laser welding robot tool calibration method based on focus positioning compensation provided by an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of the deviation between the laser indicator light focus and the robot setting tool tool1 provided in an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of initial parameter settings provided by an embodiment of the present invention;

[0032] Figure 6 A focus change diagram of the robot rotating around the tool Z axis provided by an embodiment of the present invention;

[0033] Figure 7 A schematic diagram of the plane translation of the laser indicator light focal point provided by an embodiment of the present invention;

[0034] Figure 8 A schematic diagram of spherical fitting provided by an embodiment of the present invention;

[0035] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0036] 1-Robot control cabinet; 2-Laser; 3-Host computer system; 4-Industrial six-axis robot; 5-Robot flange; 6-Optical fiber; 7-QBH connector; 8-Laser welding head; 9-Laser indicator light focus; 10-Sensor; 11-Robot geodetic coordinate system; 12-Network cable; 13-Robot control cable; 14-Network cable; 15-Default tool; 16-Setting tool; 17-Adjustment base; 18-Sensor photosensitive surface; 19-Point O in the sensor photosensitive surface; 20-Rotation axis; 21-Translation direction. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, 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 intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0039] Before explaining the technical solution of the present invention in detail, the laser welding robot system is briefly introduced as follows:

[0040] Laser welding robot system Figure 1 As shown, the industrial six-axis robot 4 is controlled by the robot control cabinet 1 through the robot control line 13. The upper computer system 3 is connected to the robot control cabinet 1 through the network cable 14 to realize the position information reading and translation and rotation control of the industrial six-axis robot 4. The end of the robot flange 5 of the industrial six-axis robot 4 is equipped with a laser welding head 8. During the welding process, the welding laser is incident on the laser welding head 8 through the qbh joint 7, and is incident on the sample surface after being collimated, expanded and focused in the laser welding head 8.

[0041] In order to calibrate the robot system, in the present invention, a sensor 10 is set just below the laser welding head 8. The sensor 10 can sense the light intensity and has a plane positioning function, which is used to determine the focal position of the laser indicator light during the calibration process. The sensor 10 is connected to the host computer system 3 through a network cable 12. The present invention is also provided with a laser 2, which is used to generate a laser indicator light that is confocal with the welding laser. The laser indicator light is visible light. The laser indicator light generated by the laser 2 and confocal with the welding laser is transmitted through an optical fiber 6 and incident into the laser welding head 8 through a qbh connector 7. After collimation, beam expansion, and focusing in the laser welding head 8, it converges at the laser indicator light focus 9. By adjusting the position of the sensor 10, the laser indicator light spot can be observed on the photosensitive surface of the sensor 10, and the focal position can be determined by the size and intensity of the spot; in the entire calibration process, the spatial three-dimensional coordinate information that needs to be substituted into the calculation finally comes from the robot earth coordinate system 11.

[0042] like Figure 2As shown, the center of the robot flange 5 of the industrial six-axis robot 4 is usually provided with a robot default tool 15, which is recorded as the default tool tool0. In the present invention, when the industrial six-axis robot 4 uses the robot default tool 15 as a tool and the robot's posture parameters are set to (0, 0, 0), the direction of the tool coordinate system of the default tool 15 is the same as the direction of the robot's earth coordinate system 11. The tool parameters (x, y, z) of the robot setting tool 16 represent the vector from the origin of the default tool tool0 coordinate system to the robot setting tool tool1 in the default tool 15 coordinate system.

[0043] Through the traditional four-point method, six-point method and other calibration methods, the tool parameters at the setting tool tool1 can be determined, that is, the vector from the default tool tool0 to the setting tool tool1, but because the change of the robot posture will affect the laser focus, the calibration result obtained by the traditional calibration method has low accuracy. In order to solve this problem, the present invention provides a laser welding robot tool calibration method and system based on focus positioning compensation, and its overall idea is to use the relatively fixed spatial relationship between the laser indicator light focus and the setting tool tool1 (that is, the distance between the two is fixed) to calculate the compensation amount, that is, the vector of the setting tool tool1 pointing to the laser indicator light focus, and use the compensation amount to compensate the calibration result obtained by the traditional calibration method to obtain the final calibration result, thereby improving the accuracy of the calibration result.

[0044] The following are examples.

[0045] Embodiment 1:

[0046] A laser welding robot tool calibration method based on focus positioning compensation, such as Figure 3 As shown, it includes: a rough calibration step, an initial positioning step, a rotation and translation step, a compensation amount calculation step and a compensation step.

[0047] In this embodiment, the rough calibration step specifically includes: setting a robot tool in the robot earth coordinate system, recorded as setting tool tool1, and calibrating a tool parameter P0 at the setting tool tool1;

[0048] For the convenience of calculation, in this embodiment, the tool coordinate system of tool tool1 is set to have the same or opposite directions as the coordinate axes of the robot's earth coordinate system;

[0049] As an optional implementation, in this embodiment, the commonly used four-point method is used to set the robot tool in the robot geodetic coordinate system, that is, the setting tool tool1, and the tool parameter P0 at the setting tool tool1 is calibrated. In some other embodiments of the present invention, other calibration methods such as the six-point method can also be used to obtain the setting tool tool1.

[0050] like Figure 4 As shown, the robot setting tool tool1 roughly set by the four-point method does not coincide with the laser indicator light focus 9 formed by the output of the qbh joint 7 and after being collimated and focused by the laser welding head 8; in three-dimensional space, when the directions of the x, y, and z axes of the tool coordinate system of the robot setting tool tool1 are the same or opposite to the directions of the x, y, and z axes of the robot earth coordinate system 11, the relative position relationship between the laser indicator light focus 9 and the robot setting tool tool1 in the robot earth coordinate system 11 is (det_x, det_y, det_z), that is, the vector pointing from the setting tool tool1 to the laser indicator light focus. In this embodiment, by solving the relative position relationship between the laser indicator light focus 9 and the robot setting tool tool1 in the robot earth coordinate system 11 of the industrial six-axis robot 4, the tool parameters in the robot system when the tool of the industrial six-axis robot 4 is set to the laser indicator light focus 9 can be further solved.

[0051] In this embodiment, the initial positioning step specifically includes: generating a laser indicator light that is confocal with the welding laser, and adjusting the robot so that the focus of the laser indicator light is located on the plane of a pre-set sensor, and then obtaining the coordinate position of the setting tool tool1 in the robot's geodetic coordinate system, which is recorded as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O.

[0052] like Figure 5 As shown, in order to make the laser indicator light focus 9 easy to observe, the sensor 10 is first adjusted to make the sensor light-sensitive surface 18 of the sensor 10 parallel to the xy plane of the robot earth coordinate system 11 by adjusting the adjustment base 17 of the sensor 10, and then the industrial six-axis robot 4 is adjusted to make the laser indicator light perpendicular to the sensor light-sensitive surface 18, and the height of the laser welding head 8 is adjusted according to the spot size read by the sensor 10 so that the laser indicator light focus 9 just falls on the sensor light-sensitive surface 18, and the upper computer system 3 reads the two-dimensional coordinates of the sensor plane light-sensitive point O19 in the sensor 10 plane coordinate system, and at the same time reads the coordinates of the robot setting tool 16 in the robot earth coordinate system 11, which is the robot setting tool point A1, recorded as the initial position. And ensure that at the robot setting tool point A1, the xyz axis of the robot setting tool 16 is in the same or opposite direction as the xyz axis of the robot earth coordinate system 11.

[0053] In this embodiment, the rotation and translation step specifically includes: after controlling the robot to rotate a certain angle around the rotation axis passing through the initial position, controlling the robot to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and obtaining the coordinate position of the setting tool tool1 in the robot's geodetic coordinate system, which is recorded as the newly added position; it is easy to understand that in the rotation and translation step, the angle of the robot's rotation around the rotation axis should be within a safe angle range.

[0054] In this embodiment, the compensation amount calculation step specifically includes: executing the rotation and translation step three times to obtain three new positions that are not in the same plane, performing spherical fitting on the initial position and the three new positions, and calculating the vector from the initial position to the center of the fitted sphere as the compensation amount.

[0055] Since the spatial positions of the setting tool tool1 and the focus of the laser indicator light are relatively fixed, and the distance between them remains unchanged, each time the rotation and translation step is performed to return the focus to point O, the newly added position of the setting tool tool1 obtained should be located on a spherical surface with point O as the center and the distance between the setting tool tool1 and the focus of the laser indicator light as the radius. Therefore, after obtaining multiple newly added positions of the setting tool tool1, this embodiment performs spherical fitting together with the initial position of the setting tool tool1, and the obtained center position is point O in the sensor plane, which is also the focus of the laser indicator light.

[0056] It should be noted that, in order to perform spherical fitting, at least four positions of the tool tool1 need to be set, that is, including the initial position, at least three additional positions need to be obtained. In this embodiment, only three additional positions are obtained.

[0057] In order to ensure the accuracy of the focal position obtained by fitting and facilitate the control and calculation of the robot, as a preferred implementation, in this embodiment, the three newly added positions are obtained by the robot rotating and translating around three different rotation axes, and the three rotation axes are respectively parallel to the three coordinate axes of the robot's earth coordinate system. The acquisition process of the three newly added positions is as follows:

[0058] like Figure 6 As shown, the industrial six-axis robot 4 is controlled by the host computer system 3 to rotate around the initial position, that is, the rotation axis 20 formed by extending the Z axis of the robot setting tool tool1 at the robot setting tool point A1, by an angle a. At this time, the spatial position of the laser indication light focus 9 changes, but because the rotation axis 20 is parallel to the Z axis of the robot geodetic coordinate system 11, and the sensor photosensitive surface 18 is parallel to the xy plane of the robot geodetic coordinate system 11, the laser indication light focus 9 is still on the sensor photosensitive surface 18.

[0059] like Figure 7As shown, the upper computer system 3 controls the industrial six-axis robot 4 to move along the translation direction 21 in the xy plane of the robot's earth coordinate system 11, and moves the laser indicator light focus 9 back to the point O19 in the sensor's photosensitive surface. During the movement, the robot setting tool tool1 will also move along the translation direction 21 in the xy plane of the robot's earth coordinate system, from the robot setting tool point A1 to the robot setting tool point A2. Since the spatial relationship between the laser indicator light focus 9 and the robot setting tool tool1 is relatively fixed, the distance between the two is a fixed value. When the size and two-dimensional coordinate value of the light spot in the plane coordinate system of the sensor 10 are read by the upper computer system 3, so that the laser indicator light focus 9 coincides with the point O19 in the sensor's photosensitive surface again, the distance between the sensor plane photosensitive point O19 and the robot setting tool point A2 is equal to the distance between the sensor plane photosensitive point O19 and the robot setting tool point A1.

[0060] Depend on Figure 7 It can be seen that after the robot setting tool tool1 of the industrial six-axis robot 4 is rotated in a single axis, the laser indicator light focus 9 is made to coincide with the sensor plane photosensitive point O19 again through the translation of the corresponding plane. Under the robot earth coordinate system 11 read by the host computer system 3, the coordinate value of the robot setting tool tool1 and the sensor plane photosensitive point O19 are equal to the distance between the robot setting tool point A1 and the sensor plane photosensitive point O19. The industrial welding robot 4 is rotated around the X-axis and Y-axis of the robot setting tool tool1 at the robot setting tool point A1 by a certain angle, and after being translated successively in the yz plane of the tool1 tool coordinate system at A1 and the xz plane of the tool1 tool coordinate system at A1, the robot setting tool point A3 and the robot setting tool point A4 are obtained.

[0061] like Figure 8 As shown, finally, the distances from the sensor plane photosensing point O19 to the robot setting tool point A1, the robot setting tool point A2, the robot setting tool point A3 and the robot setting tool point A4 are equal. The coordinates of the robot setting tool point A1, the robot setting tool point A2, the robot setting tool point A3 and the robot setting tool point A4 are used as a sphere for fitting, and the coordinate value of the sensor plane photosensing point O19 in the robot earth coordinate system 11 can be obtained. The coordinates are compared with the position coordinates of the robot setting tool point A1 to solve the relative position (det_x, det_y, det_z). The relative position is the vector from the setting tool tool1 to the focus of the laser indication light, and the vector is the compensation amount.

[0062] Optionally, in this embodiment, the least square method is specifically used to perform spherical fitting.

[0063] In this embodiment, the compensation step specifically includes: compensating the tool parameter P0 using the compensation amount to obtain the tool parameter in the robot system as the final calibration result;

[0064] The tool parameter P0 at the setting tool tool1 is the vector of the default tool tool0 pointing to the setting tool tool1. This embodiment adds the compensation amount on the basis of the tool parameter P0, which can reduce the calibration error caused by the focus position being affected by the change of the robot posture, and finally obtains the vector of the default tool tool0 pointing to the focus of the laser indicator light. This vector is the tool parameter at the focus of the laser indicator light. Compared with the tool parameters obtained by adopting the traditional calibration method, the accuracy of the tool parameters finally obtained in this embodiment is effectively improved.

[0065] In general, this embodiment uses a host computer system that communicates with the robot to collect the laser indicator light beam with the same focus as the laser beam when it is repeatedly irradiated to the same position on the plane coordinate system of the sensor plane. When the welding tool tool1 roughly calibrated by the four-point method is the robot setting tool, the tool point position information displayed by the laser welding robot is obtained by three rotations to obtain four points. When the laser indicator light focus is located at a point on the sensor plane, the position relationship between the point and the robot setting tool is obtained by least squares fitting, that is, the relative position relationship between the laser indicator light focus and the roughly calibrated setting tool tool1, and then the vector pointing from the robot default tool tool0 to the laser indicator light focus is obtained, and the tool parameters at the machine laser indicator light focus are obtained by inverse calculation. This embodiment compensates the tool parameters roughly calibrated by the four-point method by focus positioning, obtains the tool information of the robot tool and the laser indicator light focus, ensures that the posture change of the robot during welding will not affect the position of the laser focus, and solves the problem of high-precision tool calibration required in the actual generation process of the welding robot.

[0066] Embodiment 2:

[0067] A laser welding robot tool calibration system based on focus positioning compensation, such as Figure 1 As shown, including:

[0068] A rough calibration module is used to set a robot tool in the robot earth coordinate system, which is recorded as the setting tool tool1, and calibrate a tool parameter P0 at the setting tool tool1; the tool coordinate system of the setting tool tool1 is in the same or opposite direction to the coordinate axes of the robot earth coordinate system;

[0069] A laser, used for generating a laser indicator light having a focal point concentric with the welding laser;

[0070] The sensor is arranged below the welding head;

[0071] The initial positioning module is used to adjust the robot so that the focus of the laser indicator light is located on the plane of the sensor, and then obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O;

[0072] The rotation and translation module is used to control the robot to rotate a certain angle around the rotation axis passing through the initial position, and then control the robot to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the newly added position;

[0073] The compensation amount calculation module is used to obtain N newly added positions that are not in the same plane using the rotation and translation module, perform spherical fitting on the initial position and the N newly added positions, and calculate the vector from the initial position to the center of the fitted sphere as the compensation amount; N≥3;

[0074] and a compensation module, which is used to compensate the tool parameter P0 by the compensation amount, and obtain the tool parameter in the robot system as the final calibration result;

[0075] In this embodiment, the specific implementation of each module can refer to the description in the above method embodiment, which will not be repeated here.

[0076] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser welding robot tool calibration method based on focus positioning compensation, characterized in that: include: Rough calibration steps: setting a robot tool in the robot earth coordinate system, recorded as setting tool tool1, and calibrating the tool parameter P0 at the setting tool tool1; the tool coordinate system of the setting tool tool1 has the same or opposite directions as the coordinate axes of the robot earth coordinate system; Initial positioning step: generate a laser indicator light that is confocal with the welding laser, and adjust the robot so that the focus of the laser indicator light is located on the plane of the pre-set sensor, then obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O; Rotation and translation step: After controlling the robot to rotate a certain angle around the rotation axis passing through the initial position, the robot is controlled to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and the coordinate position of the setting tool tool1 in the robot's earth coordinate system is obtained and recorded as the newly added position; Compensation amount calculation step: after executing the rotation and translation steps N times to obtain N newly added positions that are not in the same plane, spherical fitting is performed on the initial position and the N newly added positions, and a vector pointing from the initial position to the center of the sphere obtained by fitting is calculated as the compensation amount; N≥3； Compensation step: using the compensation amount to compensate the tool parameter P0 to obtain the tool parameter in the robot system as the final calibration result.

2. The laser welding robot tool calibration method based on focus positioning compensation according to claim 1, characterized in that: In the compensation amount calculation step, when the N newly added positions are obtained, the robot rotates around at least two rotation axes.

3. The laser welding robot tool calibration method based on focus positioning compensation as described in claim 2, characterized in that: In the compensation amount calculation step, when the N newly added positions are obtained, the robot rotates around three rotation axes, and the three rotation axes are respectively parallel to the three coordinate axes of the robot's earth coordinate system.

4. The laser welding robot tool calibration method based on focus positioning compensation as described in claim 3 is characterized in that: N＝3。 5. The laser welding robot tool calibration method based on focus positioning compensation according to any one of claims 1 to 4, characterized in that: In the rough calibration step, the robot tool is set in the robot earth coordinate system by using the four-point method or the six-point method, that is, the tool tool1 is set, and the tool parameter P0 at the setting tool tool1 is calibrated.

6. The laser welding robot tool calibration method based on focus positioning compensation according to any one of claims 1 to 4, characterized in that: In the compensation amount calculation step, the least square method is used to perform spherical fitting on the initial position and the N newly added positions.

7. A laser welding robot tool calibration system based on focus positioning compensation, characterized in that: include: A rough calibration module is used to set a robot tool in a robot earth coordinate system, which is recorded as a setting tool tool1, and calibrate a tool parameter P0 at the setting tool tool1; the tool coordinate system of the setting tool tool1 has the same or opposite directions as the coordinate axes of the robot earth coordinate system; A laser, used for generating a laser indicator light having a focal point concentric with the welding laser; The sensor is arranged below the welding head; The initial positioning module is used to adjust the robot so that the focus of the laser indicator light is located on the plane of the sensor, and then obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the initial position; the point where the focus of the laser indicator light is on the sensor plane is recorded as point O; The rotation and translation module is used to control the robot to rotate a certain angle around the rotation axis passing through the initial position, and then control the robot to translate so that the focus of the laser indicator light returns to point O in the sensor plane, and obtain the coordinate position of the setting tool tool1 in the robot's earth coordinate system, which is recorded as the newly added position; A compensation amount calculation module, used to obtain N newly added positions that are not in the same plane by using the rotation and translation module, perform spherical fitting on the initial position and the N newly added positions, and calculate a vector from the initial position to the center of the sphere obtained by fitting as a compensation amount; N≥3； And a compensation module is used to compensate the tool parameter P0 with the compensation amount to obtain the tool parameter in the robot system as the final calibration result.

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