Resistance spot welding electrode pose and electrode surface online automatic detection method and device

Abstract

The present application relates to a kind of resistance spot welding electrode pose and electrode surface online automatic detection method and device, belong to laser detection field.The device is controlled by industrial computer, using industrial robot load two-dimensional laser ranging sensor to carry out non-contact scanning detection to upper and lower electrode, can be detected by multi-angle and through coordinate transformation, data processing process, obtain the relative spatial angle and position of upper and lower electrode and the deviation amount of the specified space pose and the wear state of spot welding electrode.The method is aimed at the problem of detecting the space limited condition in actual spot welding production, detects the pose of spot welding electrode and electrode surface state, realizes the efficient, automatic detection and evaluation of the pose of spot welding electrode and electrode surface state, provides detection technical means for the correct adjustment of spot welding electrode pose and the grinding of electrode surface, to avoid the adverse effects of incorrect electrode pose and poor electrode surface state on resistance spot welding quality.

Description

Technical Field

[0001] This invention relates to the field of laser inspection, and particularly to an automatic detection technology for the position and surface of resistance spot welding electrodes in the field of equipment manufacturing welding technology, especially an online automatic detection method and device for the position and surface of resistance spot welding electrodes. Background Technology

[0002] In the resistance spot welding process, the electrodes play a crucial role in conducting welding current, applying mechanical pressure to the workpiece, and dissipating heat and controlling the temperature field in the welding area. During operation, the welding electrodes are subjected to cyclic heat and force, leading to wear and tear such as roughening, deformation, and oxidation. This wear alters the current distribution and heat dissipation conditions in the welding area, thus affecting the welding thermal process and ultimately, the weld quality. Therefore, welding electrodes require frequent re-grinding based on their wear condition, making them frequently replaced consumable parts in resistance spot welding. Furthermore, since pressure is typically applied to the workpiece using upper and lower electrodes during resistance spot welding, the coaxiality of these electrodes and their mating arrangement also significantly impacts the weld quality.

[0003] Currently, the detection and evaluation of wear conditions and electrode alignment in spot welding mainly rely on simple measuring tools and human experience, which is not only inefficient but also has low reliability. To adapt to the development of modern industrial technology, there is a need for an automated detection technology that can reduce the influence of human experience and achieve high efficiency and high precision in detecting electrode position and surface condition, especially an automated detection technology that can adapt to the various limitations of industrial field testing space. Summary of the Invention

[0004] The purpose of this invention is to provide an online automatic detection method and device for the posture and surface of resistance spot welding electrodes. This solves the problems of low efficiency and poor reliability in existing technologies, overcomes the difficulties in measuring electrode parameters in industrial production, and provides necessary basic data for electrode alignment and adjustment. The invention achieves automated and intelligent detection of the electrode posture. Based on the acquired electrode surface contour data, through data processing and fitting, it calculates the angular offset and position deviation of the upper and lower electrodes from the specified spatial posture, as well as the spatial state of the electrode end faces, providing a technical means for online detection and adjustment of spot welding electrodes.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] An online automatic detection method for the electrode position and surface of resistance spot welding includes the following steps:

[0007] Step (1): Start and initialize the online automatic detection device for the electrode posture and electrode surface of resistance spot welding. Control the industrial robot to drive the two-dimensional laser range sensor and adjust the spatial position of the two-dimensional laser range sensor so that the starting cross-section position of the upper electrode is at the center of the laser line emitted by the two-dimensional laser range sensor. Adjust the distance between the two-dimensional laser range sensor and the starting cross-section positions of the upper and lower electrodes so that the upper and lower electrodes are within the detection distance range. Determine this position as the initial detection position.

[0008] Step (2): Set the motion trajectory of the industrial robot so that the two-dimensional laser rangefinder moves in a straight line along the upper and lower electrode surfaces until the end position of the lower electrode, and determine this position as the final detection position.

[0009] Step (3): The industrial robot returns to its initial position and feeds back the detection results to the industrial computer in digital form; upon receiving the detection data, the industrial computer controls the industrial robot to move along the pre-set motion trajectory and feeds back the position and posture information of the industrial robot.

[0010] Step (4): With the detection distance and detection path unchanged, change the detection interval angle according to the actual situation until the detection space is limited; repeat steps (1), (2), and (3) until all angles are detected.

[0011] Step (5): Adjust the angle and distance between the two-dimensional laser rangefinder and the upper and lower electrode end faces so that the laser emitted by the two-dimensional laser rangefinder completely covers the upper and lower electrode end faces at the initial and final detection positions, so as to obtain complete detection data of the measured end face.

[0012] The data processing method is as follows:

[0013] 3.1 Coordinate Transformation

[0014] The automatic detection system for electrode pose and surface of resistance spot welding has three coordinate systems: industrial robot base coordinate system A, industrial robot flange coordinate system B, and sensor coordinate system C. The sensor coordinate system is converted into the industrial robot base coordinate system through hand-eye calibration, which facilitates the unified processing of the acquired electrode surface contour data.

[0015] 3.2 Electrode Surface Contour Data Acquisition and Processing

[0016] Contour data from multiple detections at different angles are integrated into a coordinate system based on the first detection through translation and angle transformations. Let matrix A represent the 3D coordinates of a common point in coordinate system A, and matrix B represent the 3D coordinates of a common point in coordinate system B. The 3D coordinate transformation equations between coordinate systems A and B, derived from the 3D coordinate transformation model, are shown below:

[0017]

[0018] Where Δx, Δy, and Δz represent the translation of the origin, and R is the rotation matrix from coordinate system A to coordinate system B; it can be seen that the coordinate data after transformation and integration are arcs with the same center measured multiple times;

[0019] 3.3 Solving for the coordinates of the center of a circle using its properties.

[0020] The standard equation of a sphere in a three-dimensional coordinate system is:

[0021] (x-x0) 2 +(y-y0) 2 (z-z0) 2 =R 2 (2)

[0022] (x0, y0, z0) are the coordinates of the sphere's center, and R is the radius. A spatial circle can be considered as being obtained by intersecting a sphere with a plane passing through the sphere's center. Therefore, when determining a spatial circle, a plane constraint equation should be added. Let the plane equation be:

[0023] Ax + By + Cz + D = 0 (3)

[0024] Let the coordinates of three points in space be (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3). Substitute these coordinates into equations (2) and (3) to calculate the coordinates of the center of the circle and its radius R. Then, define the arcs P1, P2, P3, ..., P... n Substitute into the system of equations to calculate.

[0025] 1) Randomly select 3 points on the arc, substitute them into the system of equations to calculate the equation of the spatial circle and the coordinates of the center;

[0026] 2) Calculate the distances from the remaining points to the circle;

[0027] 3) Set a distance threshold and find the "inner points" that meet the distance threshold among all data points;

[0028] 4) Set the number of iterations and repeat steps (1) to (3) continuously. The circle with the most supported coordinate points is taken as the final circle for fitting, and its center coordinates are obtained; calculate P1, P2, P3, ..., P respectively. n The obtained center coordinates are (x1, y1, z1), (x2, y2, z2), (x3, y3, z3), ... (x n y n , z n );

[0029] 3.4 Solving for the axes of the upper and lower electrodes

[0030] The coordinates of the center of the circle are obtained through data processing and fitting. The line connecting the centers of the circle is the axis of the electrode. By performing linear fitting on each coordinate point, the axis of the upper electrode is L1 and the axis of the lower electrode is L2.

[0031] 3.5. Determine the deviation between the spatial angles of the upper and lower electrodes and the specified spatial pose using the axes of the upper and lower electrodes.

[0032] Let the relative tilt angle θ between the upper and lower electrode axes be θ, the direction vector of axis L1 be a = (u1, v1, w1), and the direction vector of axis L2 be b = (u2, v2, w2), then:

[0033]

[0034] The relative tilt angle θ between the upper and lower electrode axes can then be calculated.

[0035] In this formula, the symbol "×" represents the cross product, and the symbol "‖" represents the magnitude of the vector;

[0036] Let A be the coordinates of the endpoint of axis L1, and B be the coordinates of any point on line L2. Then we have vector AB, and c is the normal vector of axis L2. According to the formula for the distance from a point to a line, the offset of the ends of the upper and lower electrode axes is:

[0037]

[0038] In this formula, the symbol "·" represents the dot product, and the symbol "‖" represents the magnitude of the vector;

[0039] By processing and analyzing the data from the three-dimensional imaging of the upper and lower electrode surfaces, the axes of the upper and lower electrodes can be obtained. The relative tilt angle θ and the end offset Δ of the upper and lower electrode axes can then be calculated, allowing for quantitative adjustment of the pose of the upper and lower electrodes to meet experimental requirements.

[0040] 3.6 Acquisition and Processing of Electrical End Face Contour Data

[0041] An industrial robot equipped with a two-dimensional laser sensor scans the upper and lower electrode end faces to obtain data on the upper and lower electrode end faces. It can be seen that the obtained three-dimensional morphology of the upper and lower electrodes is a circular plane. Through data filtering and processing, the plane of the upper and lower electrode end faces is obtained. By fitting it, the end face diameter d and surface morphology are obtained. By comparison, the electrode cap can be replaced in real time.

[0042] The aforementioned resistance spot welding electrode pose and electrode surface online automatic detection device includes an industrial computer 1, a two-dimensional laser rangefinder 2, a sensor bracket 3, an industrial robot 4, a robot base 5, an upper electrode 601, and a lower electrode 602. The sensor bracket 3 is fixed to the threaded hole of the flange at the end of the working arm of the industrial robot 4 by bolts, and the industrial robot 4 is fixed to the robot base 5. The two-dimensional laser rangefinder 2 is fixed to the sensor bracket 3, so that it can follow the industrial robot 4 to move in three-dimensional space. The two-dimensional laser rangefinder 2 corresponds to the positions of the upper electrode 601 and the lower electrode 602.

[0043] The two-dimensional laser rangefinder 2 is a linear array high-precision two-dimensional laser rangefinder that can emit and receive linear array lasers. It can acquire all the information on the laser line in a single detection and convert the photoelectric signal into a digital signal, which is then transmitted to the industrial computer 1.

[0044] The industrial computer 1 is a ruggedized portable computer. It controls the industrial robot 4 to move the two-dimensional laser rangefinder 2 in three-dimensional space through the teach pendant programmer 401. The two-dimensional laser rangefinder 2 scans and obtains the current position and pose of the upper and lower electrodes and the surface contour information of the upper and lower electrode end faces, and obtains the position and posture information of the industrial robot 4. The obtained surface contour data of the measured upper and lower electrodes and the motion data of the industrial robot are saved to the industrial computer 1.

[0045] The beneficial effects of this invention are as follows: In response to the requirements for automatic detection of the position of resistance spot welding electrodes, this invention achieves efficient and automated detection and evaluation of spot welding electrode position by non-contact measurement of the electrode outer contour and the morphological feature size parameters and image output method of the detection results, thereby improving the level of spot welding quality control and work efficiency. Attached Figure Description

[0046] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate the invention and are used to explain it, but do not constitute an undue limitation of the invention.

[0047] Figure 1 This is a schematic diagram of the automatic detection device for the position and surface of the resistance spot welding electrode according to the present invention.

[0048] Figures 2 to 5 This is a schematic diagram of the measurement angle transformation of the automatic detection method for the position and surface of the resistance spot welding electrode of the present invention;

[0049] Figure 6 This is a flowchart of the automatic detection method for the position of resistance spot welding electrodes according to the present invention;

[0050] Figure 7The flowchart below shows the automatic surface inspection method for resistance spot welding electrodes according to the present invention.

[0051] Figure 8 This is a data processing flowchart of the automatic detection method for the position of resistance spot welding electrodes according to the present invention;

[0052] Figure 9 This is a data processing flowchart of the automatic detection method for the surface of resistance spot welding electrodes according to the present invention;

[0053] In the diagram: 1. Industrial computer; 2. Two-dimensional laser rangefinder; 3. Sensor bracket; 4. Industrial robot; 401. Teach pendant programmer; 402. Robot control cabinet; 5. Robot base; 601. Upper electrode; 602. Lower electrode. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] See Figures 1 to 9 As shown, the online automatic detection method and apparatus for the position and surface of resistance spot welding electrodes of the present invention is controlled by an industrial computer. An industrial robot equipped with a two-dimensional laser rangefinder performs non-contact scanning detection of the upper and lower electrodes. Through multi-angle detection and processes such as coordinate transformation and data processing, the deviation of the relative spatial angle and position of the upper and lower electrodes from the specified spatial position and the wear state of the spot welding electrodes can be obtained. This method addresses the problem of detecting the position and surface condition of spot welding electrodes under limited detection space conditions in actual spot welding production. It achieves efficient and automated detection and evaluation of the position and surface condition of spot welding electrodes, providing a detection technology for the correct adjustment of the electrode position and the grinding of the electrode surface, thereby avoiding the adverse effects of incorrect electrode position and poor electrode surface condition on the welding quality of resistance spot welding.

[0056] See Figures 1 to 5As shown, the online automatic detection device for the posture and surface of resistance spot welding electrodes of the present invention achieves automated and intelligent detection of electrode posture. Based on the acquired electrode surface contour data, through data processing and axis fitting, the relative axis tilt angle θ of the upper and lower electrodes, the end offset Δ of the upper and lower electrodes, and the spatial state such as the electrode end face diameter d are calculated, providing a technical means for online detection and adjustment of spot welding electrodes. It includes an industrial computer 1, a two-dimensional laser rangefinder 2, a sensor bracket 3, an industrial robot 4, a robot base 5, an upper electrode 601, and a lower electrode 602. The sensor bracket 3 is fixed to the threaded hole of the flange at the end of the working arm of the industrial robot 4 by bolts. The two-dimensional laser rangefinder 2 is fixed to the sensor bracket 3, enabling it to move with the industrial robot 4 in three-dimensional space.

[0057] The two-dimensional laser rangefinder 2 is a linear array high-precision two-dimensional laser rangefinder that can emit and receive linear array lasers. It can acquire all the information on the laser line in a single detection and convert the photoelectric signal into a digital signal, which is then transmitted to the industrial computer 1.

[0058] The industrial computer 1 is a ruggedized portable computer. It controls the industrial robot 4 to move the two-dimensional laser rangefinder 2 in three-dimensional space through the teach pendant programmer 401. The two-dimensional laser rangefinder 2 scans and acquires the surface contour information of the current position and pose of the upper and lower electrodes being measured, and acquires the position and posture information of the industrial robot 4. The acquired electrode surface contour data and industrial robot motion data are saved to the industrial computer 1. Through subsequent data processing and analysis optimization, efficient and automated detection and evaluation of the attitude of the spot welding electrodes are realized.

[0059] See Figures 6 to 9 As shown, the online automatic detection method for the position and surface of resistance spot welding electrodes of the present invention, under the condition of limited detection space in actual spot welding production, is controlled by an industrial computer. An industrial robot equipped with a two-dimensional laser rangefinder performs non-contact scanning detection of the upper and lower electrodes within the detection window. To improve detection accuracy, multiple detections can be performed at fixed angle intervals, and the optimal data from each detection is taken. The multiple detection data are integrated into a single coordinate system through coordinate transformation. Then, the obtained data is fitted to obtain the deviation of the relative spatial angle and position of the upper and lower electrodes from the specified spatial pose, as well as the state of the spot welding electrode end face. This provides technical support for online detection and timely correction of spot welding electrodes, and for electrode grinding and replacement. The detection steps include the following:

[0060] Step (1): Start the detection system and initialize it. Control the industrial robot to drive the two-dimensional laser rangefinder sensor through the teach pendant programmer. Adjust the spatial position of the sensor so that the initial cross-section position of the electrode being measured is at the center of the laser line emitted by the two-dimensional laser sensor. Adjust the distance between the sensor and the initial cross-section position of the electrode so that the electrode being measured is in the optimal detection distance range. Determine this position as the initial detection position.

[0061] Step (2): Set the motion trajectory of the industrial robot so that the two-dimensional laser sensor can move in a straight line along the surface of the electrode being measured until the end position of the lower electrode being measured, and determine this position as the final position of the detection.

[0062] Step (3): The industrial robot returns to its initial position and feeds back the detection results to the industrial computer in digital form. Upon receiving the detection data, the industrial computer controls the industrial robot to move along a pre-set motion trajectory and feeds back the position and posture information of the industrial robot.

[0063] Step (4): To obtain more surface contour data of the electrode under test and improve the accuracy of the detection, while keeping the detection distance and detection path unchanged, only change the detection interval angle according to the actual situation until the detection space is limited. Repeat steps (1), (2), (3), and (4) until all angles are detected.

[0064] Step (5): Adjust the angle and distance between the sensor and the electrode end face to be tested so that the laser emitted by the sensor can completely cover the electrode end face at the initial and final positions of the detection, so as to obtain complete detection data of the electrode end face.

[0065] Automatic data processing of resistance spot welding electrode position and surface detection:

[0066] coordinate transformation

[0067] The automatic detection system for electrode pose and surface of resistance spot welding has three coordinate systems: industrial robot base coordinate system A, industrial robot flange coordinate system B, and sensor coordinate system C. The sensor coordinate system is converted into the industrial robot base coordinate system through hand-eye calibration, which facilitates the unified processing of the acquired electrode surface contour data.

[0068] Electrode surface contour data acquisition and processing

[0069] Contour data from multiple detections at different angles can be integrated into a coordinate system based on the first detection through translation and angle transformations. Let matrix A represent the 3D coordinates of a common point in coordinate system A, and matrix B represent the 3D coordinates of a common point in coordinate system B. From the 3D coordinate transformation model, the 3D coordinate transformation equations between coordinate systems A and B are as follows:

[0070]

[0071] Where Δx, Δy, and Δz represent the translation of the origin, and R is the rotation matrix from coordinate system A to coordinate system B. It can be seen that the transformed and integrated coordinate data represents multiple measurements of arcs with the same center.

[0072] Solve for the coordinates of the center of a circle using the properties of a spatial circle.

[0073] The standard equation of a sphere in a three-dimensional coordinate system is:

[0074] (x-x0) 2 +(y-y0) 2 +(z-z0) 2 =R 2 (2)

[0075] (x0, y0, z0) are the coordinates of the sphere's center, and R is the radius. A spatial circle can be considered as being formed by intersecting a sphere with a plane passing through the sphere's center. Therefore, when determining a spatial circle, a plane constraint equation should be added. Let the plane equation be:

[0076] Ax + Ry + Cz + D = 0 (3)

[0077] Let the coordinates of three points in space be (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3). By solving these equations and substituting them into equations (2) and (3), we can calculate the coordinates of the center of the circle and its radius R.

[0078] Arcs P1, P2, P3, ..., P n Substitute the values ​​into the system of equations to calculate, taking P1 as an example.

[0079] 1) Randomly select 3 points on the arc, substitute them into the system of equations to calculate the equation of the spatial circle and the coordinates of the center;

[0080] 2) Calculate the distances from the remaining points to the circle;

[0081] 3) Set a distance threshold and find the "inner points" that meet the distance threshold among all data points;

[0082] 4) Set a certain number of iterations and repeat steps (1) to (3) continuously. The circle with the most supported coordinate points is taken as the final circle for fitting, and its center coordinates are obtained.

[0083] Calculate P1, P2, P3, ..., P respectively. n The obtained center coordinates are (x1, y1, z1), (x2, y2, z2), (x3, y3, z3), ... (x n y n , z n ).

[0084] Solving for the electrode axis

[0085] The coordinates of the center of the circle can be obtained through data processing and fitting. It can be seen that the line connecting the centers of the circle is the axis of the electrode. By performing linear fitting on each coordinate point, the axis of the upper electrode is L1 and the axis of the lower electrode is L2.

[0086] The deviation between the spatial angles of the upper and lower electrodes and the specified spatial pose is determined by calculating the electrode axis.

[0087] Let the relative tilt angle θ between the upper and lower electrode axes be θ, the direction vector of axis L1 be a = (u1, v1, w1), and the direction vector of axis L2 be b = (u2, v2, w2), then:

[0088]

[0089] The relative tilt angle θ between the upper and lower electrode axes can then be calculated.

[0090] In this formula, the symbol “×” represents the cross product, and the symbol “‖” represents the magnitude of the vector.

[0091] Let A be the coordinates of the endpoint of axis L1, and B be the coordinates of any point on line L2. Then we have vector AB, and c is the normal vector of axis L2. According to the formula for the distance from a point to a line, the offset of the ends of the upper and lower electrode axes is:

[0092]

[0093] In this formula, the symbol "·" represents the dot product, and the symbol "‖" represents the magnitude of the vector.

[0094] By processing and analyzing the data from the three-dimensional imaging of the electrode surface, the axes of the upper and lower electrodes can be obtained. The relative tilt angle θ of the upper and lower electrode axes and the end offset Δ of the upper and lower electrode axes can then be calculated, allowing for quantitative adjustment of the electrode pose to meet experimental requirements.

[0095] Electric electrode surface profile data acquisition and processing

[0096] An industrial robot equipped with a two-dimensional laser sensor scans the electrode end face at a certain angle to obtain electrode end face data. It can be seen that the obtained three-dimensional shape of the electrode is a circular plane. Through data filtering and processing, the plane of the electrode end face is obtained. By fitting it, its end face diameter d and surface morphology can be obtained. By comparing with the standard, the electrode cap can be understood and replaced in real time.

[0097] Under normal operating conditions as described in this example, when using the detection device of the present invention to inspect welding clamps, the electrode angle error is ≤0.1° and the end offset error is ≤0.05mm.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made to the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for online automatic detection of the electrode posture and electrode surface in resistance spot welding, characterized in that: Includes the following steps: Step (1): Start and initialize the online automatic detection device for the electrode posture and electrode surface of resistance spot welding. Control the industrial robot to drive the two-dimensional laser range sensor and adjust the spatial position of the two-dimensional laser range sensor so that the starting cross-section position of the upper electrode is at the center of the laser line emitted by the two-dimensional laser range sensor. Adjust the distance between the two-dimensional laser range sensor and the starting cross-section positions of the upper and lower electrodes so that the upper and lower electrodes are within the detection distance range. Determine this position as the initial detection position. Step (2): Set the motion trajectory of the industrial robot so that the two-dimensional laser rangefinder moves in a straight line along the upper and lower electrode surfaces until the end position of the lower electrode, and determine this position as the final detection position. Step (3): The industrial robot returns to its initial position and feeds back the detection results to the industrial computer in digital form; upon receiving the detection data, the industrial computer controls the industrial robot to move along the pre-set motion trajectory and feeds back the position and posture information of the industrial robot. Step (4): With the detection distance and detection path unchanged, change the detection interval angle according to the actual situation until the detection space is limited; repeat steps (1), (2), and (3) until all angles are detected. Step (5): Adjust the angle and distance between the two-dimensional laser rangefinder and the upper and lower electrode end faces so that the laser emitted by the two-dimensional laser rangefinder completely covers the upper and lower electrode end faces at the initial and final detection positions, so as to obtain complete detection data of the measured end face. The data processing method is as follows: 3.1 Coordinate Transformation The automatic detection system for electrode pose and surface of resistance spot welding has three coordinate systems: industrial robot base coordinate system A, industrial robot flange coordinate system B, and sensor coordinate system C. The sensor coordinate system is converted into the industrial robot base coordinate system through hand-eye calibration, which facilitates the unified processing of the acquired electrode surface contour data. 3.2 Electrode Surface Contour Data Acquisition and Processing Contour data from multiple detections at different angles are integrated into a coordinate system based on the first detection through translation and angle transformations. Let matrix A represent the 3D coordinates of a common point in coordinate system A, and matrix B represent the 3D coordinates of a common point in coordinate system B. The 3D coordinate transformation equations between coordinate systems A and B, derived from the 3D coordinate transformation model, are shown below: （1）； in This represents the translation of the origin of the coordinate system. for coordinate system to The rotation matrix of the coordinate system; it can be seen that the coordinate data after transformation and integration are arcs with the same center measured multiple times; 3.3 Solving for the coordinates of the center of a circle using its properties. The standard equation of a sphere in a three-dimensional coordinate system is: （2）； Let R be the coordinates of the center of the sphere and R be the radius. A spatial circle can be considered as being obtained by intersecting a sphere with a plane passing through the center of the sphere. Therefore, when finding a spatial circle, a plane constraint equation should be added. Let the plane equation be: （3）； Let the coordinates of three points in space be... Substitute the equations (2) and (3) into the equations to calculate the coordinates of the center and the radius R; respectively, calculate the coordinates of the arc. Substitute into the system of equations to calculate. 1) Randomly select 3 points on the arc, substitute them into the system of equations to calculate the equation of the spatial circle and the coordinates of the center; 2) Calculate the distances from the remaining points to the circle; 3) Set a distance threshold and find the "inner points" that meet the distance threshold among all data points; 4) Set the number of iterations and repeat steps (1) to (3) continuously. The circle with the most supported coordinate points is taken as the final circle for fitting, and its center coordinates are obtained; calculate respectively The obtained center coordinates are ; 3.4 Solving for the axes of the upper and lower electrodes The coordinates of the circle centers are obtained through data processing and fitting. The line connecting the centers of each circle forms the axis of the electrode. By performing linear fitting on each coordinate point, the axis of the upper electrode is obtained. The axis of the lower electrode is ; 3.

5. Determine the deviation between the spatial angles of the upper and lower electrodes and the specified spatial pose using the axes of the upper and lower electrodes. Let the relative tilt angle of the upper and lower electrode axes be... axis Direction vector axis Direction vector ,but: （4）； The relative tilt angle between the upper and lower electrode axes can then be determined. ; In this formula, the symbol The cross product is represented by the symbol "". " represents the magnitude of the vector; Let the axis be The endpoint coordinates are ,straight line The coordinates of any point are Then we have a vector , As axis Given the normal vector, and using the formula for the distance from a point to a line, the offset of the ends of the upper and lower electrode axes is: （5）； In this formula, the symbol " "Represents the dot product, symbol " " represents the magnitude of the vector; By processing and analyzing the data from three-dimensional imaging of the upper and lower electrode surfaces, the axes of the upper and lower electrodes can be obtained, and thus the relative tilt angles of the upper and lower electrode axes can be calculated. and the end offset of the upper and lower electrode axes The poses of the upper and lower electrodes are quantitatively adjusted to meet the experimental requirements. 3.6 Acquisition and Processing of Electrical End Face Contour Data An industrial robot equipped with a two-dimensional laser sensor scans the upper and lower electrode end faces to obtain data on the upper and lower electrode end faces. It can be seen that the obtained three-dimensional morphology of the upper and lower electrodes is a circular plane. Through data filtering and processing, the plane of the upper and lower electrode end faces is obtained. By fitting it, the end face diameter d and surface morphology are obtained. By comparison, the electrode cap can be understood and replaced in real time. The online automatic detection device for the position and surface of resistance spot welding electrodes includes an industrial computer (1), a two-dimensional laser rangefinder (2), a sensor bracket (3), an industrial robot (4), a robot base (5), an upper electrode (601), and a lower electrode (602). The sensor bracket (3) is fixed to the threaded hole of the flange at the end of the working arm of the industrial robot (4) by bolts. The industrial robot (4) is fixed on the robot base (5). The two-dimensional laser rangefinder (2) is fixed to the sensor bracket (3) so that it can follow the industrial robot (4) to move in three-dimensional space. The two-dimensional laser rangefinder (2) corresponds to the position of the upper electrode (601) and the lower electrode (602).

2. The method for online automatic detection of electrode posture and electrode surface in resistance spot welding according to claim 1, characterized in that: The two-dimensional laser rangefinder (2) is a linear array high-precision two-dimensional laser rangefinder that can emit and receive linear array lasers. It can acquire all the information on the laser line in a single detection and convert the photoelectric signal into a digital signal, which is then transmitted to the industrial computer (1).

3. The method for online automatic detection of resistance spot welding electrode posture and electrode surface according to claim 2, characterized in that: The industrial computer (1) is a ruggedized portable computer. It controls the industrial robot (4) to drive the two-dimensional laser rangefinder (2) to move in three-dimensional space through the teach pendant (401). The two-dimensional laser rangefinder (2) scans and obtains the current position and pose of the upper and lower electrodes and the surface contour information of the upper and lower electrode end faces, and obtains the position and posture information of the industrial robot (4). The obtained surface contour data of the measured upper and lower electrodes and the motion data of the industrial robot are saved to the industrial computer (1).

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