CN115178858A - Laser welding robot tool calibration method and system based on focus positioning compensation - Google Patents

Abstract

The invention discloses a method and a system for calibrating a laser welding robot tool based on focus positioning compensation, which belong to the technical field of laser welding and comprise the following steps: setting a robot tool1 under a robot geodetic coordinate system, and calibrating a tool parameter P0 at the tool 1; generating laser indicating light which is in a confocal point with welding laser, adjusting a robot to enable the focal point of the laser indicating light to be located at a point O on a preset plane of a sensor, and then obtaining the coordinate position of the tool1 as an initial position; controlling the robot to rotate for a certain angle around a rotating shaft passing through the initial position, controlling the robot to translate to enable the focus to return to a point O, and acquiring the coordinate position of the tool1 as a newly added position; and after N is more than or equal to 3 noncoplanar newly added positions are obtained, carrying out spherical surface fitting together with the initial position, calculating a vector of the initial position pointing to the center of the sphere, compensating P0 by using the vector to obtain tool parameters in the robot system, and finishing calibration. The invention can improve the calibration precision of the robot tool parameter at the focus.

Description

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

Technical Field

The invention belongs to the technical field of laser welding, and particularly relates to a method and a system for calibrating a laser welding robot tool based on focus positioning compensation.

Background

Laser welding is a process in which a workpiece is irradiated with high-energy laser beams, the operating temperature is rapidly increased, and the workpiece is melted and reconnected to form a permanent connection. Compared with other welding processes, the laser welding process has the advantages of deep melting depth, high speed, small deformation, low requirement on welding environment, high power density, no influence of a magnetic field, no limitation to a conductive material, no need of vacuum working conditions, no generation of X-rays in the welding process and the like, and is widely applied to the field of high-end precision manufacturing. Laser welding generally can bind with joint robot, and for manual welding, welding robot can reduce welding manpower manufacturing cost by a wide margin, improves weldment work's automatic intelligent operation degree, and welding robot can accomplish a large amount of welding actions in certain workspace voluntarily, consequently every welder's of automatically regulated gesture that can be arbitrary.

The process of laser welding is closely related to the position of the focal point of the laser beam, which is usually set to the tool point of the robot when performing welding robot tool point setting. However, when calibrating the tool of the robot, since the focus of the laser welding does not have an entity in the space, the four-point method and the six-point method of calibrating the tool of the conventional robot are difficult to calibrate with the tool of the laser welding robot, even if the focus simulation is performed by mounting a tip on the laser welding head, the precision of the tool point of the robot measured by using the conventional calibration methods such as the four-point method and the six-point method is still low, and the method cannot be applied to a high-precision laser welding robot system, which limits the application of the laser welding robot in practice.

Disclosure of Invention

Aiming at the defects and improvement requirements of the prior art, the invention provides a method and a system for calibrating a laser welding robot tool based on focus positioning compensation, and aims to ensure that the position of a laser focus cannot be influenced by the posture change of a robot in the welding process, so that the calibration precision of the robot tool parameter at the focus is improved.

To achieve the above object, according to an aspect of the present invention, there is provided a method for calibrating a laser welding robot tool based on focus positioning compensation, comprising:

a rough calibration step: setting a robot tool under a robot geodetic coordinate system, recording as a setting tool1, and calibrating a tool parameter P0 at the setting tool 1; setting the directions of the tool coordinate system of the tool1 and the coordinate axes of the robot geodetic coordinate system to be the same or opposite;

an initial positioning step: generating laser indicating light which is in a confocal point with welding laser, adjusting the robot to enable the focal point of the laser indicating light to be located on a preset plane of a sensor, and then obtaining a coordinate position of a set tool1 under a robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser indication light focus on the sensor plane is marked as a point O;

and a rotational translation step: controlling the robot to rotate for a certain angle around a rotating shaft passing through the initial position, controlling the robot to translate to enable a laser indication light focus to return to a point O in a sensor plane, and acquiring a coordinate position of a set tool1 under a robot geodetic coordinate system and marking the coordinate position as a new position;

and a compensation amount calculation step: performing the rotational translation step N times to obtain N newly added positions which are not on the same plane, performing spherical surface fitting on the initial position and the N newly added positions, and calculating a vector of the initial position pointing to the sphere center obtained by fitting to serve as a compensation quantity; n is more than or equal to 3;

a compensation step: and compensating the tool parameter P0 by using the compensation amount to obtain a tool parameter in the robot system as a final calibration result.

Further, in the compensation amount calculating step, when the acquired N newly added positions are obtained, the robot rotates around at least two rotation axes.

Further, in the compensation amount calculating step, when the N newly added positions are obtained, the robot rotates around three rotation axes, and the three rotation axes are parallel to three coordinate axes of a robot geodetic coordinate system respectively.

Further, N =3.

Further, in the rough calibration step, a robot tool, that is, a tool1, is set in the robot geodetic coordinate system by using a four-point method or a six-point method, and a tool parameter P0 at the tool1 is calibrated.

Further, in the compensation amount calculation step, spherical surface fitting is performed on the initial position and the N newly added positions by using a least square method.

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

the rough calibration module is used for setting a robot tool under a robot geodetic coordinate system, recording the robot tool as a setting tool1 and calibrating a tool parameter P0 at the setting tool 1; setting the directions of the tool coordinate system of the tool1 and the coordinate axes of the robot geodetic coordinate system to be the same or opposite;

the laser is used for generating laser indicating light which is in a confocal point with the welding laser;

the sensor is arranged below the welding head;

the initial positioning module is used for adjusting the robot to enable the focal point of the laser indicating light to be located on the plane of the sensor, and then obtaining the coordinate position of the setting tool1 under the robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser indication light focus on the sensor plane is marked as a point O;

the rotation translation module is used for controlling the robot to translate after rotating for a certain angle around a rotating shaft passing through the initial position, so that the laser indication light focus returns to a point O in the plane of the sensor, and acquiring the coordinate position of the setting tool1 in the robot geodetic coordinate system and recording the coordinate position as a newly added position;

the compensation amount calculation module is used for performing spherical surface fitting on the initial position and the N newly added positions after the N newly added positions which are not on the same plane are obtained by the rotation translation module, and calculating a vector of the initial position pointing to the center of the sphere obtained by fitting to serve as the compensation amount; n is more than or equal to 3;

and the compensation module is used for compensating the tool parameter P0 by the compensation amount to obtain a tool parameter in the robot system as a final calibration result.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

(1) After the tool parameters at the position of the setting tool1 are calibrated by using the existing calibration method, based on the characteristic that the space relation between the laser indication light focus and the setting tool1 is relatively fixed, a plurality of coordinate positions of the tool1 are obtained by rotating the robot and then translating the robot to return the laser indicating light focus to the original position, then obtaining the focal position of the laser indicating light which is in confocal with the welding laser in a spherical fitting mode, further obtaining a vector which points to the focal point of the laser indicating point from the initial position of the setting tool1, and taking the vector as a compensation quantity, and compensating the tool parameters of the set tool1 obtained by calibration of the existing calibration method to obtain a final calibration result, namely a vector of the default tool0 of the robot pointing to the laser indication light focus. According to the invention, through compensation, the calibration error caused by the influence of the posture change of the robot on the focus position can be reduced, and the calibration precision of the robot tool parameter at the focus position is effectively improved.

(2) According to the invention, a plurality of coordinate positions of the tool1 are obtained by rotating the robot around the coordinate axis for three times in a single-axis manner, so that the value of the focus in a certain direction is unchanged after the rotation, and the focus can return to the point O in the plane of the sensor only by moving in two directions subsequently, thereby simplifying the implementation of translation operation.

Drawings

FIG. 1 is a schematic view of a laser welding robot system according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a robot setting tool1 according to an embodiment of the present invention;

FIG. 3 is a flowchart of a method for calibrating a laser welding robot tool based on focus position compensation according to an embodiment of the present invention;

fig. 4 is a schematic diagram illustrating a deviation between a laser pointer focus and a robot setting tool1 according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of initial parameter setting according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating the change in focus of a robot rotating about the Z-axis of a tool according to an embodiment of the present invention;

FIG. 7 is a schematic view of a plane shift of a focal point of laser pointer light provided by an embodiment of the present invention;

FIG. 8 is a schematic view of a spherical fit provided by an embodiment of the present invention;

the same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1-a robot control cabinet; 2-a laser; 3, an upper computer system; 4-industrial six-axis robot; 5-a robot flange plate; 6-an optical fiber; a 7-qbh joint; 8-laser welding head; 9-laser indicating light focus; 10-a sensor; 11-robot geodetic coordinate system; 12-a network cable; 13-robot control line; 14-mesh wire; 15-default tool; 16-setting means; 17-adjusting the base; 18-a sensor light-sensitive surface; 19-point O in the sensor photosurface; 20-a rotation axis; 21-direction of translation.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Before explaining the technical scheme of the invention in detail, a laser welding robot system is briefly introduced as follows:

laser welding robot system is as shown in fig. 1, including industry six axis robot 4, industry six axis robot 4 is controlled through robot control line 13 by robot control cabinet 1, and host computer system 3 passes through net twine 14 and connects robot control cabinet 1, realizes reading and translation, rotation control the positional information of industry six axis robot 4. The tail end of a robot flange plate 5 of the industrial six-axis robot 4 is provided with a laser welding head 8, in the welding process, welding laser is emitted into the laser welding head 8 from a qbh connector 7, and is emitted into the surface of a sample after being collimated, expanded and focused in the laser welding head 8.

In order to calibrate the robot system, in the invention, a sensor 10 is arranged right below the laser welding head 8, and the sensor 10 can sense the light intensity and has a plane positioning function for determining the focal position of the laser indicating light in the calibration process. The sensor 10 is connected with the upper computer system 3 through a network cable 12. The laser 2 is also arranged for generating laser indicating light which is confocal with welding laser, the laser indicating light is visible light, the laser indicating light which is confocal with the welding laser and is generated by the laser 2 is transmitted through an optical fiber 6, is incident into a laser welding head 8 through a qbh joint 7, is converged at a laser indicating light focus 9 after being collimated, expanded and focused in the laser welding head 8, can observe a light spot of the laser indicating light on a photosensitive surface of a sensor 10 by adjusting the position of the sensor 10, and can judge the focus position through the size and the strength of the light spot; in the whole calibration process, the spatial three-dimensional coordinate information which needs to be substituted into the calculation finally comes from the robot geodetic coordinate system 11.

As shown in fig. 2, a default robot tool 15, which is designated as a default tool0, is usually provided at the center of a robot flange 5 of an industrial six-axis robot 4. In the present invention, when the industrial six-axis robot 4 uses the default tool 15 of the robot as a tool and the attitude parameters of the robot are set to (0, 0), the tool coordinate system direction of the default tool 15 is the same as the direction of the geodetic coordinate system 11 of the robot. The tool parameters (x, y, z) of the robot setting tool 16 represent a vector pointing from the origin of the default tool0 coordinate system to the robot setting tool1 in the default tool 15 coordinate system.

By the traditional calibration methods such as a four-point method, a six-point method and the like, the tool parameters at the tool1 can be determined and set, i.e. a vector pointing from the default tool0 to the setting tool1, however, because the change of the robot posture can affect the laser focus, the calibration result obtained by the traditional calibration method has lower precision. In order to solve the problem, the invention provides a method and a system for calibrating a laser welding robot tool based on focus positioning compensation, and the overall thought is as follows: the compensation quantity is calculated by utilizing the characteristic that the spatial relationship between the laser indication light focus and the setting tool1 is relatively fixed (namely the distance between the laser indication light focus and the setting tool1 is constant), and the compensation quantity is utilized to compensate the calibration result obtained by adopting the traditional calibration method, so that the final calibration result is obtained, and the precision of the calibration result is improved.

The following are examples.

Example 1:

a method for calibrating a laser welding robot tool based on focus positioning compensation, as shown in fig. 3, includes: the method comprises a rough calibration step, an initial positioning step, a rotational translation step, a compensation amount calculation step and a compensation step.

In this embodiment, the rough calibration step specifically includes: setting a robot tool under a robot geodetic coordinate system, recording as a setting tool1, and calibrating a tool parameter P0 at the setting tool 1;

for convenience of calculation, the tool coordinate system of the tool1 and the directions of the coordinate axes of the robot earth coordinate system are set to be the same or opposite in the embodiment;

as an alternative implementation, in this embodiment, a common four-point method is used to set a robot tool, that is, a set tool1, in a robot geodetic coordinate system, and to calibrate a tool parameter P0 at the set tool1. In other embodiments of the present invention, the tool1 may be obtained by using other calibration methods such as a six-point method.

As shown in fig. 4, the robot setting tool1 obtained by rough setting by a four-point method does not coincide with the laser indication light focus 9 output by the qbh joint 7 and formed by collimating and focusing by the laser welding head 8; in the three-dimensional space, when the directions of the single axes x, y, z of the tool1 and the directions of the single axes x, y, z of the robot earth coordinate system 11 are the same or opposite, the relative position relationship between the laser indication light focus 9 and the robot setting tool1 under the robot geodetic coordinate system 11 is obtained as (det _ x, det _ y, det _ z), that is, the vector pointing to the laser indication light focus from the setting tool1. In this embodiment, by solving the relative positional relationship between the laser pointer light focus 9 and the robot setting tool1 in the robot geodetic coordinate system 11 of the industrial six-axis robot 4, the tool parameters in the robot system when the tool setting of the industrial six-axis robot 4 is the laser pointer light focus 9 can be further solved.

In this embodiment, the initial positioning step specifically includes: generating laser indicating light which is in a confocal point with welding laser, adjusting the robot to enable the focal point of the laser indicating light to be located on a preset plane of a sensor, and then obtaining a coordinate position of a set tool1 under a robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser pointer light focus on the sensor plane is denoted as point O.

As shown in fig. 5, in order to make the laser indication light focus 9 easy to observe, firstly, the sensor photosurface 18 of the sensor 10 is made parallel to the xy plane of the robot geodetic coordinate system 11 by adjusting the adjusting base 17 of the sensor 10, then the industrial six-axis robot 4 is adjusted to make the laser indication light perpendicular to the sensor photosurface 18, and the laser welding head 8 is adjusted in height to make the laser indication light focus 9 just fall on the sensor photosurface 18 through the size of a light spot read by the sensor 10, the upper computer system 3 reads the two-dimensional coordinates of the sensor plane photosite O19 in the sensor 10 plane coordinate system, and simultaneously reads the coordinates of the robot setting tool 16 under the robot geodetic coordinate system 11, and sets a tool point A1 for the robot, and records the coordinates as an initial position. And ensures 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 geodetic coordinate system 11.

In this embodiment, the rotational translation step specifically includes: controlling the robot to rotate for a certain angle around a rotating shaft passing through the initial position, controlling the robot to translate to enable a laser indication light focus to return to a point O in a sensor plane, and acquiring a coordinate position of a set tool1 under a robot geodetic coordinate system and marking the coordinate position as a new position; it is easily understood that, in the rotational-translation step, the angle of controlling the robot to rotate around the rotation axis should be within a safe angle range.

In this embodiment, the step of calculating the compensation amount specifically includes: and (3) performing the rotation translation step for 3 times to obtain 3 newly added positions which are not on the same plane, performing spherical surface fitting on the initial position and the 3 newly added positions, and calculating a vector of the initial position pointing to the sphere center obtained by fitting to serve as a compensation quantity.

Because the setting tool1 and the laser indication light focus are relatively fixed in spatial position and the distance between the setting tool1 and the laser indication light focus is kept unchanged, after the focus returns to the point O by executing the rotation translation step each time, the newly added position of the setting tool1 should be located on a spherical surface with the point O as the center of the sphere and the distance between the setting tool1 and the focal point of the laser indicating light as the radius. Therefore, in this embodiment, after acquiring a plurality of newly added positions of the setting tool1, spherical surface fitting is performed together with the initial position of the setting tool1, and the obtained spherical center position is the point O in the sensor plane and is also the focal point of the laser pointer light.

It should be noted that, in order to perform the spherical surface fitting, at least four positions of the tool1 need to be set, that is, at least 3 new positions need to be obtained together with the initial position, and in this embodiment, only 3 new positions are obtained.

In order to ensure the accuracy of the focus position obtained by fitting and facilitate the control and calculation of the robot, as a preferred implementation manner, in this embodiment, the obtained 3 newly added positions are obtained by rotating and translating the robot around three different rotation axes, where the three rotation axes are parallel to three coordinate axes of the robot ground coordinate system respectively. The process of acquiring the 3 newly added positions is as follows:

as shown in fig. 6, the industrial six-axis robot 4 is controlled by the upper computer system 3 to rotate an angle a around a rotation axis 20 formed by extending the Z axis of the robot setting tool1 at the initial position, i.e. the robot setting tool point A1, at which time the spatial position of the laser indication light focus 9 changes, but since the rotation axis 20 is parallel to the Z axis of the robot earth coordinate system 11 and the sensor photosurface 18 is parallel to the xy plane of the robot earth coordinate system 11, the laser indication light focus 9 is still on the sensor photosurface 18.

As shown in fig. 7, the industrial six-axis robot 4 is controlled by the upper computer system 3 to move in the xy plane on the robot ground coordinate system 11 along the translation direction 21, and the laser pointer light focus 9 is moved back to the point O19 in the sensor light sensing surface again. During the movement, the robot setting tool1 will also move along the translation direction 21 in the xy-plane of the robot coordinate system from the robot setting tool point A1 to the robot setting tool point A2. Since the spatial relationship between the laser indication light focus 9 and the robot setting tool1 is relatively fixed, the distance between the laser indication light focus 9 and the robot setting tool1 is a fixed value, and when the size and the 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 indication light focus 9 coincides with the point O19 in the back sensor light sensing surface again, the distance between the sensor plane light sensing point O19 and the robot setting tool point A2 is equal to the distance between the sensor plane light sensing point O19 and the robot setting tool point A1.

As can be seen from fig. 7, after the robot setting tool1 of the industrial six-axis robot 4 is rotated in a single axis, the laser pointer light focus 9 is made to coincide with the sensor plane photosite O19 again by the translation of the corresponding plane, under the robot geodetic coordinate system 11 read by the upper computer system 3, the coordinate value of the robot setting tool1 and the sensor plane photosite O19 are equal to the distance between the robot setting tool point A1 and the sensor plane photosite O19. The industrial welding robot 4 is sequentially rotated by a certain angle around the X-axis and the Y-axis of the robot setting tool1 at the robot setting tool point A1, and successively translated in the yz plane of the tool coordinate system of the tool1 at the position A1 and the xz plane of the tool coordinate system of the tool1 at the position A1, thereby obtaining a robot setting tool point A3 and a robot setting tool point A4.

As shown in fig. 8, the distances from the sensor plane photosite 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 finally obtained to be equal, and 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 fitted to be a spherical surface, so that the coordinate values of the sensor plane photosite O19 in the robot geodetic coordinate system 11 are obtained, and compared with the position coordinates of the robot setting tool point A1, and the relative positions (det _ x, det _ y, det _ z) which are vectors pointing from the setting tool1 to the laser pointing light focus are obtained, and are compensation quantities.

Optionally, in this embodiment, the spherical surface fitting is performed by using a least square method.

In this embodiment, the compensation step specifically includes: compensating the tool parameter P0 by using the compensation quantity to obtain a tool parameter in the robot system as a final calibration result;

the tool parameter P0 at the tool1 is set as a vector of the default tool0 pointing to the tool1, and in this embodiment, based on the tool parameter P0, the calibration error caused by the influence of the robot posture change on the focal position can be reduced by adding the compensation amount, and finally obtaining a vector pointing to the laser indication light focus from the default tool0, wherein the vector is a tool parameter at the laser indication light focus.

In general, in this embodiment, when the upper computer system communicating with the robot collects the laser indicating light beam having the same focus as the laser beam and irradiates the same position on the plane coordinate system of the sensor plane for multiple times, and under the condition that the welding tool1 roughly calibrated by the four-point method is set as the tool for the robot, the tool point position information displayed by the laser welding robot obtains four points through three rotations, obtaining the position relation between a point and a robot setting tool when the laser indicating light focus is positioned at the point on the sensor plane by least square fitting, namely the relative position relation between the laser indicating light focus and a roughly calibrated setting tool1, and further obtaining a vector pointing to the laser indicating light focus by the default tool0 of the robot, and reversely solving to obtain the tool parameter at the laser indicating light focus. In the embodiment, the tool parameters roughly calibrated by the four-point method are compensated through focus positioning, tool information of a robot tool and the laser indication light focus is obtained, and the posture change of the robot does not influence the position of the laser focus in the welding process, so that the problem of high-precision tool calibration required in the actual generation process of the welding robot is solved.

Example 2:

a system for calibrating a laser welding robot tool based on focus position compensation, as shown in fig. 1, comprising:

the rough calibration module is used for setting a robot tool under a robot geodetic coordinate system, recording the robot tool as a setting tool1 and calibrating a tool parameter P0 at the setting tool 1; setting the directions of the tool coordinate system of the tool1 and the coordinate axes of the robot earth coordinate system to be the same or opposite;

a laser for generating laser indicating light which is confocal with the welding laser;

the sensor is arranged below the welding head;

the initial positioning module is used for adjusting the robot to enable the focal point of the laser indicating light to be located on the plane of the sensor, and then obtaining the coordinate position of the setting tool1 under the robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser indication light focus on the sensor plane is marked as a point O;

the rotation translation module is used for controlling the robot to translate after rotating for a certain angle around a rotating shaft passing through the initial position, so that the laser indication light focus returns to a point O in the plane of the sensor, and the coordinate position of the setting tool1 under the robot geodetic coordinate system is obtained and recorded as a newly added position;

the compensation amount calculation module is used for performing spherical surface fitting on the initial position and the N newly added positions after the N newly added positions which are not on the same plane are obtained by the rotation translation module, and calculating a vector of the initial position pointing to the center of the sphere obtained by fitting to serve as the compensation amount; n is more than or equal to 3;

the compensation module is used for compensating the tool parameter P0 for the compensation quantity to obtain a tool parameter in the robot system as a final calibration result;

in this embodiment, the detailed implementation of each module may refer to the description in the above method embodiment, and will not be repeated here.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A laser welding robot tool calibration method based on focus positioning compensation is characterized by comprising the following steps:

a rough calibration step: setting a robot tool under a robot geodetic coordinate system, recording as a setting tool1, and calibrating a tool parameter P0 at the setting tool 1; the tool coordinate system of the setting tool1 is the same as or opposite to the directions of all coordinate axes of the robot geodetic coordinate system;

initial positioning: generating laser indicating light which is in a confocal point with welding laser, adjusting the robot to enable the focal point of the laser indicating light to be located on a preset plane of a sensor, and then obtaining a coordinate position of the set tool1 under a robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser indicating light focus on the sensor plane is marked as a point O;

and a rotational translation step: controlling the robot to rotate for a certain angle around the rotating shaft passing through the initial position, controlling the robot to translate, enabling the laser indication light focus to return to a point O in the plane of the sensor, and acquiring the coordinate position of the setting tool1 under the geodetic coordinate system of the robot and recording the coordinate position as a new position;

and a compensation amount calculation step: executing the rotation translation step N times to obtain N newly added positions which are not in the same plane, performing spherical surface fitting on the initial position and the N newly added positions, and calculating a vector of the initial position pointing to the center of a sphere obtained by fitting to serve as a compensation quantity; n is more than or equal to 3;

a compensation step: and compensating the tool parameter P0 by using the compensation amount to obtain a tool parameter in the robot system as a final calibration result.

2. The method for calibrating a laser welding robot tool based on focus positioning compensation as claimed in claim 1, wherein in said compensation amount calculating step, the robot is rotated around at least two rotation axes when the N new positions are obtained.

3. The method for calibrating a laser welding robot tool based on focus positioning compensation as claimed in claim 2, wherein in said compensation amount calculating step, the robot rotates around three rotation axes when the N new positions are obtained, and the three rotation axes are respectively parallel to three coordinate axes of the robot earth coordinate system.

4. The method for calibrating a laser welding robot tool based on focus positioning compensation of claim 3, wherein N =3.

5. The method for calibrating a tool of a laser welding robot based on focus position compensation according to any one of claims 1 to 4, wherein in the step of rough calibration, a four-point method or a six-point method is used to set a robot tool, namely a tool1, in a robot geodetic coordinate system, and a tool parameter P0 at the tool1 is calibrated.

6. The method for calibrating a laser welding robot tool based on focus location compensation according to any one of claims 1 to 4, wherein in the step of calculating the compensation amount, a least square method is used to perform spherical fitting on the initial position and the N newly added positions.

7. The utility model provides a laser welding robot tool calibration system based on focus positioning compensation which characterized in that includes:

the rough calibration module is used for setting a robot tool under a robot geodetic coordinate system, recording the robot tool as a setting tool1 and calibrating a tool parameter P0 at the setting tool 1; the directions of the tool coordinate system of the set tool1 and the directions of all coordinate axes of the robot earth coordinate system are the same or opposite;

a laser for generating laser indicating light which is confocal with the welding laser;

the sensor is arranged below the welding head;

the initial positioning module is used for adjusting the robot to enable the focal point of the laser indicating light to be located on the plane of the sensor, and then obtaining the coordinate position of the setting tool1 under the robot geodetic coordinate system and recording the coordinate position as an initial position; the point of the laser indication light focus on the sensor plane is marked as a point O;

the rotation translation module is used for controlling the robot to translate after rotating for a certain angle around the rotating shaft passing through the initial position, so that the laser indication light focus returns to a point O in the plane of the sensor, and the coordinate position of the setting tool1 in the robot geodetic coordinate system is obtained and recorded as a newly added position;

the compensation amount calculation module is used for performing spherical surface fitting on the initial position and the N newly added positions after the N newly added positions which are not on the same plane are obtained by the rotation translation module, and calculating a vector of the initial position pointing to the sphere center obtained by fitting to serve as the compensation amount; n is more than or equal to 3;

and the compensation module is used for compensating the tool parameter P0 by the compensation amount to obtain a tool parameter in the robot system as a final calibration result.

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