Fixed point tracking method, system and device based on laser real-time tracking

Abstract

The invention provides a fixed-point tracking method, system and device based on real-time laser tracking, the fixed-point tracking method comprises a point collection teaching stage and a fixed-point tracking stage, in the point collection teaching stage, a large cylinder is kept immobile, a welding robot is moved around a welding seam on the surface of the cylinder, and the large cylinder is fixed; position information of a welding seam to be welded by the robot relative to the tail end of the robot is obtained in advance by obtaining a welding seam image of the CCD visual sensor, and preliminary positioning of the tail end of the robot is achieved; in the welding stage, a large cylinder is rotated to enable a welding seam to sequentially pass through a CCD visual sensor and a robot welding tail end, after the CCD visual sensor receives welding seam position information, the offset of the robot tail end and the center line of the welding seam is calculated, at the moment, the robot tail end only needs to deviate in the radial direction of a roller and deviate relative to the normal direction of the welding seam, and the welding seam can be accurately welded. Therefore, the welding task under the large cylinder environment is completed through the small welding robot.

Description

Technical Field

[0001] The present invention relates to the field of automation control, and in particular to the technical field of a fixed-point tracking method, system and device based on laser real-time tracking. Background Art

[0002] With the continuous development of science and technology, the application of automation control in industry is increasing. In the industrial production link of workpiece welding, the following methods are usually used: Figure 1 The process shown is used to follow and weld the weld. A CCD vision sensor installed in front of the welding gun (with a spacing of 50-100mm) emits a line laser and collects weld images. The light signal is converted into time-series serial image data, and then the image processing module performs noise reduction and contour enhancement. The left and right deviations (Δx) and height deviations (Δz) between the weld center line and the preset path are calculated. After receiving the deviation data, the welding controller generates an adjustment instruction through the control algorithm. Δx drives the cross slide to move horizontally, and Δz drives the welding gun lifting mechanism. The robot is driven to compensate for the above-calculated deviations, and the weld is tracked in real time to complete the weld of the workpiece.

[0003] However, most of these deviation calculation technologies require pre-calibration of the collaborative axis in order to calculate the conversion relationship between the image data collected by the CDD vision sensor and the robot coordinates. Calibration of the collaborative axis generally requires a three-point method, and the angle of each point must be greater than 30 degrees. This results in that when the large cylinder rotates more than 30 degrees, it has exceeded the robot's workspace and cannot be automatically calibrated. In addition, the rotation center of the large cylinder is eccentric. Therefore, existing technologies make it difficult to calibrate a relatively accurate collaborative axis coordinate system through robots, making it difficult to accurately track welds.

[0004] Therefore, there is an urgent need for a new weld tracking method that can solve the problem of accurate tracking in large cylinder welding scenarios. Summary of the Invention

[0005] The present invention proposes a fixed-point tracking method, system and device based on real-time laser tracking, which can eliminate the need for calibrating cooperative axes and enable a small welding robot to complete welding tasks under large cylinder conditions.

[0006] The present invention is achieved through the following technical solutions:

[0007] In one aspect, the present invention provides a fixed-point tracking method based on real-time laser tracking, comprising:

[0008] The point picking teaching stage and the fixed point tracking stage. In the point picking teaching stage, the robot end moves and the large cylinder is fixed. The point picking teaching stage includes:

[0009] S10: Acquire first weld trajectory information from a preset calibration point to a preset welding point;

[0010] S20: Calculating a first radial offset and a first normal offset of the robot end relative to the weld according to the first weld trajectory information and a preset coordinate transformation matrix;

[0011] S30: Correcting the robot end according to the first radial offset and the first normal offset so that the robot end faces the weld centerline when it reaches the preset welding point;

[0012] During the fixed-point tracking phase, the robot end remains stationary while the large cylinder rotates around the rotation axis. The fixed-point tracking phase includes:

[0013] S40: Acquire second weld trajectory information;

[0014] S50: Calculating a second radial offset and a second normal offset of the robot end relative to the weld according to the second weld trajectory information and the coordinate transformation matrix;

[0015] S60: Correcting the robot end according to the second radial offset, the second normal offset, and the tangential speed of the large cylinder rotation until the welding is completed.

[0016] Furthermore, the step S20 includes:

[0017] S201: extracting a plurality of weld feature points according to the first weld trajectory information, performing B-spline fitting on the weld feature points, and obtaining a first weld centerline;

[0018] S202: transforming the coordinates of the first weld centerline according to the coordinate transformation matrix to obtain position information of the robot end relative to the first weld centerline;

[0019] S203: Decoupling the position information to calculate a first radial offset and a first normal offset of the robot end relative to the weld.

[0020] Furthermore, the step S60 includes:

[0021] S601A: Calculating a radial offset change speed between the robot end and the weld over time based on the second radial offset and the tangential speed;

[0022] S601B: Calculating a time-dependent normal offset speed between the robot end and the weld based on the second normal offset and the tangential speed;

[0023] S602: Correcting the robot end according to the radial offset change speed and the normal offset change speed until welding is completed.

[0024] On the other hand, the present invention also provides a fixed-point tracking system based on laser real-time tracking, which comprises:

[0025] Data acquisition module, offset calculation module, robot teaching correction module and robot fixed point correction module; among them,

[0026] During the point-collecting and teaching phase:

[0027] Data acquisition module: used to obtain the first weld trajectory information from the preset calibration point to the preset welding point;

[0028] An offset calculation module is configured to calculate a first radial offset and a first normal offset of the robot end relative to the weld according to the first weld trajectory information and a preset coordinate transformation matrix;

[0029] A robot teaching correction module is used to correct the robot end according to the first radial offset and the first normal offset, so that the robot end is aligned with the weld centerline when it reaches the preset welding point position;

[0030] During the fixed-point tracking phase:

[0031] Data acquisition module: used to obtain the second weld trajectory information;

[0032] An offset calculation module is used to calculate a second radial offset and a second normal offset of the robot end relative to the weld according to the second weld trajectory information and the coordinate transformation matrix;

[0033] The robot fixed-point correction module is used to correct the robot end according to the second radial offset, the second normal offset and the tangential speed of the large cylinder rotation until the welding is completed.

[0034] Furthermore, the offset calculation module includes:

[0035] B-spline fitting submodule: used to extract multiple weld feature points based on weld trajectory information, perform B-spline fitting based on the weld feature points, and obtain the weld curve;

[0036] Coordinate transformation submodule: used to transform the coordinates of the weld curve according to the coordinate transformation matrix to obtain the position information of the robot end relative to the weld curve;

[0037] Offset decoupling submodule: used to decouple the position information and calculate the radial offset and normal offset of the robot end relative to the weld centerline.

[0038] Furthermore, the robot fixed-point correction module includes:

[0039] Radial offset change calculation submodule: used to calculate the radial offset change speed between the robot end and the weld over time based on the radial offset and tangential speed;

[0040] Normal offset change calculation submodule: used to calculate the normal offset change speed between the robot end and the weld over time based on the normal offset and tangential speed;

[0041] Offset correction submodule: corrects the robot end according to the radial offset change speed and the normal offset change speed until welding is completed.

[0042] On the other hand, the present invention also provides a fixed-point tracking device based on laser real-time tracking, which comprises:

[0043] A workpiece fixture, a welding robot, a welding gun disposed at the end of the welding robot, a CCD visual sensor, a control unit, and any of the above-mentioned fixed-point tracking systems;

[0044] The workpiece fixing frame is provided with a rotating shaft at both ends, and the rotating shafts at both ends are located on the same axis;

[0045] The CCD visual sensor is fixedly arranged on the robot and is relatively fixed to the position of the welding gun;

[0046] The control unit is respectively connected to the workpiece fixing frame, the welding robot, the welding gun, the CCD visual sensor and the fixed-point tracking system;

[0047] The control unit is used to control the rotation of the rotating shaft of the workpiece fixing frame, the switch of the welding gun and the switch of the CCD visual sensor;

[0048] The fixed-point tracking system is connected to the CCD vision sensor and outputs the offset of the end of the welding robot relative to the center line of the weld according to the input of the CCD vision sensor;

[0049] The fixed-point tracking system is also connected to the welding robot and performs real-time correction on the end of the robot according to the offset of the end of the welding robot relative to the center line of the weld.

[0050] The present invention is based on maintaining the relative position of the CCD vision sensor and the end of the welding robot fixed. The CCD vision sensor is used to obtain in advance the position information of the weld to be welded by the robot relative to the end of the robot. In the point-taking and teaching stage, the large cylinder is kept stationary and the welding robot is moved in a small range to achieve preliminary positioning of the end of the robot; in the welding stage, the large cylinder is rotated so that the weld passes through the CCD vision sensor and the robot welding end in sequence. After the CCD vision sensor receives the weld position information, it calculates the offset between the end of the robot and the center line of the weld. At this time, the end of the robot only needs to be offset along the radial direction of the cylinder and the normal offset relative to the weld, thereby achieving the welding task of large cylinder welding with a small welding robot.

[0051] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the process of existing welding technology;

[0053] Figure 2 A structural block diagram of a fixed-point tracking system based on real-time laser tracking provided by the present invention;

[0054] Figure 3 To execute Figure 2 The flowchart of the fixed-point tracking method of the fixed-point tracking system based on laser real-time tracking is shown;

[0055] Figure 4 This is a specific structural block diagram of the offset calculation module of the present invention;

[0056] Figure 5 for Figure 4 The execution flow chart of the offset calculation module is shown. DETAILED DESCRIPTION

[0057] The existing welding device includes a welding robot, a workpiece fixing frame for fixing the workpiece to be welded, a CCD visual sensor set at the end of the welding robot. Since the welding gun is set at the end of the robot, the position of the welding gun is referred to as the robot end in the present invention. The welding robot establishes a coordinate transformation matrix between the robot coordinate system and the workpiece coordinate system through automatic or manual teaching, and converts the position of the robot end to the workpiece coordinate system through the coordinate transformation matrix, and uses this to calculate the offset between the robot welding gun position and the weld center line, and finally controls the robot end to align with the weld center line to achieve welding of the workpiece.

[0058] However, in the existing control method, in the large cylinder welding scenario, it is difficult for the robot to calibrate the collaborative axis through the three-point method, and it is impossible to establish the workpiece coordinate system, and thus it is impossible to realize the coordinate transformation between the workpiece coordinate system and the robot coordinate system. After analysis, the inventor found that in the large cylinder scenario, a small range of weld rotation can be approximately regarded as a weld translation, and there is a fixed distance difference between the CCD vision sensor and the robot end. During the rotation of the cylinder, the CCD vision sensor always measures the position information of the weld first, and then the welding is performed by the welding gun. Therefore, the rotation process of the cylinder can be regarded as the splicing of countless weld translations. At this time, the robot end is kept from moving along the direction of weld rotation (that is, the tangential direction of rotation). It is only necessary to control the height of the robot end and the weld (along the radial direction of the cylinder) to not offset and the robot end and the weld center line (normal direction of rotation) to not offset, so as to achieve accurate welding of the large cylinder.

[0059] Based on the above analysis, the present invention provides a fixed-point tracking method and system based on real-time laser tracking. Figure 2 and Figure 3 , Figure 2 This is a flow chart of a fixed-point tracking method based on real-time laser tracking provided by the present invention. Figure 3 To execute Figure 2 The following is a block diagram of a fixed-point tracking system based on a fixed-point tracking method using real-time laser tracking. The fixed-point tracking system of the present invention includes a data acquisition module 10, an offset calculation module 20, a robot teaching and correction module 30, and a robot fixed-point correction module 40. To ensure that the welding gun tip is aligned with the weld centerline when welding begins, the fixed-point tracking system includes a point acquisition and teaching phase and a fixed-point tracking phase. The execution flow of the various components of the fixed-point tracking system during each phase is as follows:

[0060] During the point-taking teaching phase, the robot end moves while the large cylinder remains stationary. At this point, the data acquisition module 10, the offset calculation module 20, and the robot teaching correction module 30 participate in the point-taking teaching process.

[0061] The data acquisition module 10 executes step S10: acquiring first weld trajectory information from a preset calibration point to a preset welding point.

[0062] The preset calibration point is the starting point for the point-collection teaching task. At this time, the CCD vision sensor is directly aligned with this point. The preset welding point is the point where the robot end-point is aligned with the center of the weld at the calibration point when the CCD vision sensor is aligned with this point. The weld trajectory collected by the CCD vision sensor from the calibration point to the welding point is the first weld trajectory information.

[0063] The offset calculation module 20 executes step S20: calculating a first radial offset and a first normal offset of the robot end relative to the weld according to the first weld trajectory information and a preset coordinate transformation matrix.

[0064] See also Figure 4 , the offset calculation module 20 includes:

[0065] The B-spline fitting submodule 201 is used to execute step S201: extract multiple weld feature points based on the first weld trajectory information, perform B-spline fitting based on the weld feature points, and obtain a first weld centerline;

[0066] The weld trajectory is essentially the gap between the two large cylinders. Usually, the welding gun is aimed at the center line between the gaps. The center line cannot be directly calibrated by image coordinates and must be generated by data fitting. In this invention, B-spline fitting is used to collect multiple weld feature points {q0,q i ,q2…q n}, construct the node vectors {u0,u1,u2…u n}, set the spline order p = 5, and the center line of the first weld is expressed using B-spline as follows:

[0067]

[0068] where q j is the weld feature point, is the spline basis function of the p-degree B-spline curve, and u is the knot vector.

[0069] The coordinate transformation submodule 202 is used to execute step S202: transform the coordinates of the first weld centerline according to the coordinate transformation matrix to obtain position information of the robot end relative to the weld curve;

[0070] The collected data is the coordinate position of the center line of the first weld relative to the CCD vision sensor. Therefore, the coordinate transformation matrix is ​​calculated in advance based on the positional relationship between the CCD vision sensor and the robot end. The weld curve obtained by the CCD is converted into the position information of the robot end relative to the weld curve through the coordinate transformation matrix.

[0071] The offset decoupling submodule 203 is used to execute step S203: decoupling the position information to calculate a first radial offset and a first normal offset of the robot end relative to the weld centerline.

[0072] According to the relative position relationship between the first weld centerline and the robot end and the preset standard position relationship, the radial offset and normal offset of the robot end relative to the weld centerline are calculated.

[0073] S30: Correcting the robot end according to the first radial offset and the first normal offset so that the robot end is aligned with the weld centerline when it reaches the preset welding point.

[0074] After receiving the deviation data, the PID algorithm generates adjustment instructions, driving the welding gun lifting mechanism to perform radial offsets and the robotic arm to achieve normal offsets. When the CCD vision sensor reaches the weld point, the robot end—the welding gun—is aligned with the weld centerline. At this point, the system also stores the weld curve position offset information from the calibration point to the weld point.

[0075] In the fixed-point tracking stage, the robot end remains stationary and the large cylinder rotates around the rotation axis. At this time, the data acquisition module 10, the offset calculation module 20, and the robot fixed-point correction module 40 participate in the fixed-point tracking process.

[0076] The data acquisition module 10 executes step S40: obtaining second weld trajectory information;

[0077] After the point teaching, the welding task begins. At this time, the CCD vision sensor begins to continuously obtain the weld position information during the rotation of the large cylinder.

[0078] The offset calculation module 20 executes step S50: calculating a second radial offset and a second normal offset of the robot end relative to the weld according to the second weld trajectory information and the coordinate transformation matrix;

[0079] Similarly, the components in the offset calculation module 20 try to calculate the radial offset and normal offset of the robot end relative to the weld at each position based on the weld position information during the rotation of the large cylinder obtained by the CCD vision sensor.

[0080] The machine fixed point correction module 40 executes step S60: correcting the robot end according to the second radial offset, the second normal offset and the tangential speed of the large cylinder rotation until the welding is completed.

[0081] The robot fixed-point correction module 40 includes a radial offset change calculation submodule, a normal offset change calculation submodule, and an offset correction submodule.

[0082] During the fixed-point tracking stage, the robot end does not need to move significantly to track the weld centerline of the weld. Instead, it moves slightly within a fixed plane to correct the left and right offsets of the weld centerline and the changes in the distance between the welding gun and the welding surface caused by the eccentricity during the rotation of the large cylinder. Therefore, during the rotation of the large cylinder, it will generate a tangential speed in the direction of rotation. In order to match the cylinder rotation speed with the speed of controlling the movement of the welding gun, the offset position value must be converted into the offset change value.

[0083] The radial offset change calculation submodule 401 is used to execute step S601: to calculate the radial offset change speed between the robot end and the weld over time based on the radial offset and the tangential speed;

[0084] Each radial offset segment is divided into (Δx1, Δx2, Δx3, ... Δxn). Within each predetermined radial offset segment, a corresponding set of radial offset change velocities (Vx1, Vx2, Vx3, ... Vxn) is calculated based on the tangent velocity. This set of discrete radial offset change velocities is then fitted to obtain a continuous radial offset change velocity, generating a VT plot of the robot end-point in the radial direction over welding time.

[0085] The normal offset change calculation submodule 402 is used to execute step S602: calculating the normal offset change speed between the robot end and the weld over time based on the normal offset and the tangential speed;

[0086] The normal offset variation is defined as each segment of the normal offset (Δz1, Δz2, Δz3, ..., Δzn). Within each preset normal offset segment, a corresponding set of normal offset variation velocities (Vz1, Vz2, Vz3, ..., Vzn) is calculated based on the tangent velocity. This set of discrete normal offset variation velocities is then fitted to produce a continuous normal offset variation velocity, generating a VT plot of the robot end-point in the normal direction over welding time.

[0087] The offset correction submodule 403 is used to execute step S603: correcting the robot end according to the radial offset change speed and the normal offset change speed until welding is completed.

[0088] The radial and normal movement speeds of the robot end relative to the large cylinder are adjusted in real time according to the radial offset change speed and the normal offset change speed, thereby realizing real-time following of the weld center line of the rotating large cylinder by the robot end, so that a small welding robot can also complete the welding task in a large cylinder environment, and improves the welding accuracy, making the weld more complete.

[0089] The present invention is based on maintaining the relative position of the CCD vision sensor and the end of the welding robot fixed. The CCD vision sensor is used to obtain in advance the position information of the weld to be welded by the robot relative to the end of the robot. In the point-taking and teaching stage, the large cylinder is kept stationary and the welding robot is moved in a small range to achieve preliminary positioning of the end of the robot; in the welding stage, the large cylinder is rotated so that the weld passes through the CCD vision sensor and the robot welding end in sequence. After the CCD vision sensor receives the weld position information, it calculates the offset between the end of the robot and the center line of the weld. At this time, the end of the robot only needs to be offset along the radial direction of the cylinder and the normal offset relative to the weld, thereby achieving the welding task of large cylinder welding with a small welding robot.

[0090] The present invention also provides a fixed-point tracking device for real-time laser tracking, which includes: a workpiece fixing frame, a welding robot, a welding gun arranged at the end of the welding robot, a CCD visual sensor, a control unit and any of the fixed-point tracking systems mentioned above.

[0091] The workpiece fixing frame is provided with a rotating shaft at both ends, and the rotating shafts at both ends are located on the same axis;

[0092] The CCD visual sensor is fixedly arranged on the robot and is relatively fixed to the position of the welding gun;

[0093] The control unit is respectively connected to the workpiece fixing frame, the welding robot, the welding gun, the CCD visual sensor and the fixed-point tracking system;

[0094] The control unit is used to control the rotation of the rotating shaft of the workpiece fixing frame, the switch of the welding gun and the switch of the CCD visual sensor;

[0095] The fixed-point tracking system is connected to the CCD vision sensor and outputs the offset of the end of the welding robot relative to the center line of the weld according to the input of the CCD vision sensor.

[0096] The fixed-point tracking system is also connected to the welding robot and performs real-time correction on the end of the robot according to the offset of the end of the welding robot relative to the center line of the weld.

[0097] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the fixed-point tracking method based on laser real-time tracking described in any one of the above embodiments is implemented.

[0098] The present invention may take the form of a computer program product implemented on one or more storage media (including but not limited to magnetic disk storage, CD-ROMs, optical storage, etc.) containing program code. Computer-readable storage media include permanent and non-permanent, removable and non-removable media, and may be implemented by any method or technology for information storage. The information may be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include but are not limited to phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device.

[0099] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A fixed-point tracking method based on real-time laser tracking for welding large cylinder welds, characterized in that: include: The point picking teaching stage and the fixed point tracking stage. In the point picking teaching stage, the robot end moves and the large cylinder is fixed. The point picking teaching stage includes: S10: Acquire first weld trajectory information from a preset calibration point to a preset welding point; S20: Calculating a first radial offset and a first normal offset of the robot end relative to the weld according to the first weld trajectory information and a preset coordinate transformation matrix; S30: Correcting the robot end according to the first radial offset and the first normal offset so that the robot end faces the weld centerline when it reaches the preset welding point; During the fixed-point tracking phase, the robot end remains stationary while the large cylinder rotates around the rotation axis. The fixed-point tracking phase includes: S40: Acquire second weld trajectory information; S50: Calculating a second radial offset and a second normal offset of the robot end relative to the weld according to the second weld trajectory information and the coordinate transformation matrix; S60: Correcting the robot end according to the second radial offset, the second normal offset, and the tangential speed of the large cylinder rotation until the welding is completed.

2. The fixed-point tracking method based on real-time laser tracking according to claim 1, characterized in that: The step S20 includes: S201: extracting multiple weld feature points based on the first weld trajectory information, performing B-spline fitting based on the weld feature points, and obtaining a first weld centerline; S202: transforming the coordinates of the first weld centerline according to the coordinate transformation matrix to obtain position information of the robot end relative to the first weld centerline; S203: Decoupling the position information to calculate a first radial offset and a first normal offset of the robot end relative to the weld.

3. The fixed-point tracking method based on real-time laser tracking according to claim 2, characterized in that: The step S60 includes: S601A: Calculating a radial offset change speed between the robot end and the weld over time based on the second radial offset and the tangential speed; S601B: Calculating a time-dependent normal offset speed between the robot end and the weld based on the second normal offset and the tangential speed; S602: Correcting the robot end according to the radial offset change speed and the normal offset change speed until welding is completed.

4. A fixed-point tracking system based on real-time laser tracking, characterized in that: include: Data acquisition module, offset calculation module, robot teaching correction module and robot fixed point correction module; among them, During the point-collecting and teaching phase: Data acquisition module: used to obtain the first weld trajectory information from the preset calibration point to the preset welding point; An offset calculation module is configured to calculate a first radial offset and a first normal offset of the robot end relative to the weld according to the first weld trajectory information and a preset coordinate transformation matrix; A robot teaching correction module is used to correct the robot end according to the first radial offset and the first normal offset, so that the robot end is aligned with the weld centerline when it reaches the preset welding point position; During the fixed-point tracking phase: Data acquisition module: used to obtain the second weld trajectory information; An offset calculation module is used to calculate a second radial offset and a second normal offset of the robot end relative to the weld according to the second weld trajectory information and the coordinate transformation matrix; The robot fixed-point correction module is used to correct the robot end according to the second radial offset, the second normal offset and the tangential speed of the large cylinder rotation until the welding is completed.

5. The fixed-point tracking system according to claim 4, characterized in that: The offset calculation module includes: B-spline fitting submodule: used to extract multiple weld feature points based on weld trajectory information, perform B-spline fitting based on the weld feature points, and obtain the weld curve; Coordinate transformation submodule: used to transform the coordinates of the weld curve according to the coordinate transformation matrix to obtain the position information of the robot end relative to the weld curve; Offset decoupling submodule: used to decouple the position information and calculate the radial offset and normal offset of the robot end relative to the weld centerline.

6. The fixed-point tracking system according to claim 5, characterized in that: The robot fixed-point correction module includes: Radial offset change calculation submodule: used to calculate the radial offset change speed between the robot end and the weld over time based on the radial offset and tangential speed; Normal offset change calculation submodule: used to calculate the normal offset change speed between the robot end and the weld over time based on the normal offset and tangential speed; Offset correction submodule: corrects the robot end according to the radial offset change speed and the normal offset change speed until welding is completed.

7. A fixed-point tracking device based on real-time laser tracking, characterized in that: include: A workpiece fixture, a welding robot, a welding gun arranged at the end of the welding robot, a CCD visual sensor, a control unit, and a fixed-point tracking system according to any one of claims 4 to 6; The workpiece fixing frame is provided with a rotating shaft at both ends, and the rotating shafts at both ends are located on the same axis; The CCD visual sensor is fixedly arranged on the robot and is relatively fixed to the position of the welding gun; The control unit is respectively connected to the workpiece fixing frame, the welding robot, the welding gun, the CCD visual sensor and the fixed-point tracking system; The control unit is used to control the rotation of the rotating shaft of the workpiece fixing frame, the switch of the welding gun and the switch of the CCD visual sensor; The fixed-point tracking system is connected to the CCD vision sensor and outputs the offset of the end of the welding robot relative to the center line of the weld according to the input of the CCD vision sensor; The fixed-point tracking system is also connected to the welding robot and performs real-time correction on the end of the robot according to the offset of the end of the welding robot relative to the center line of the weld.

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