A z-axis instant compensation method and system for flight welding

Abstract

The application discloses a Z-axis instant compensation method and system for flight welding, and belongs to the technical field of flight welding. The method comprises the following steps: obtaining the conversion relationship between the camera and the robot coordinate system, the standard welding height and the compensation conversion coefficient through calibration; collecting the image of the workpiece to be welded by the camera and extracting the pixel coordinates of each welding point, and converting the pixel coordinates to the robot coordinate system to obtain the welding coordinates; collecting the actual height of each welding point by the displacement sensor, calculating the difference between the actual height and the standard welding height, and then calculating the Z-axis compensation amount; when the robot reaches the welding coordinates, the galvanometer performs Z-axis compensation based on the Z-axis compensation amount. The displacement sensor is arranged in front of the galvanometer relative to the welding path, so that the pre-scanning is realized while the galvanometer is moving; and the compensation amount is received by the galvanometer controller through the high-speed real-time bus and the galvanometer controller responds instantaneously. The visual positioning and the height compensation are completed in parallel during the continuous movement of the robot, the production cycle is significantly shortened, and the welding quality and efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of flight welding technology, and in particular to a method and system for real-time Z-axis compensation in flight welding. Background Technology

[0002] Flying welding involves moving a galvanometer driven by the end effector of a robot. The galvanometer generates a welding laser beam to weld the workpiece. Precise welding can be completed during continuous movement. During flying welding, because the height of different parts of the workpiece surface is different, Z-axis compensation of the galvanometer is required to focus the welding laser beam of the galvanometer at the height of the welding position.

[0003] In existing technologies, Z-axis compensation of the galvanometer mainly relies on an independent servo mechanism. This mechanism drives a line-scanning camera to scan the pre-welding trajectory and perform imaging calculations. The calculation results are then transmitted to a PLC controller, which sends the data to the galvanometer via its internal database for Z-axis pre-compensation. Finally, the robot moves to drive the galvanometer for welding. This serial link—scanning first, then transmitting, then welding—results in a long compensation response time. It cannot perform real-time Z-axis compensation of the galvanometer based on the height of the welding point during in-flight welding, thus affecting welding efficiency. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a Z-axis real-time compensation method and system for flight welding, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this invention first proposes a real-time Z-axis compensation method for in-flight welding, comprising the following steps: S1, through calibration, obtains the transformation relationship between the camera and robot coordinate systems, the standard welding height, and the compensation transformation coefficient; S2, acquire images of the workpiece to be welded using a camera, and extract the pixel coordinates of each welding point in the image; S3, Based on the transformation relationship, the pixel coordinates are transformed into the robot coordinate system to obtain the robot's welding coordinates; S4, the actual height of each welding point is collected by the displacement sensor, and the difference between the actual height and the standard welding height is calculated; S5. Calculate the Z-axis compensation amount based on the difference and the compensation conversion coefficient; S6, when the robot reaches the position corresponding to the welding coordinate, the galvanometer performs Z-axis compensation based on the Z-axis compensation amount.

[0006] As a further aspect of the present invention, in step S1, the transformation relationship between the camera and robot coordinate systems includes the rotation matrix and translation matrix between the camera and robot coordinate systems, which are obtained through hand-eye calibration.

[0007] As a further aspect of the present invention, in step S1, the method for calibrating the standard welding height is as follows: Set the galvanometer to zero on the Z-axis; The standard welding height is determined by measuring the height of the focal point of the welding laser beam generated by the galvanometer using a displacement sensor.

[0008] As a further aspect of the present invention, in step S1, the calibration method for the compensation conversion coefficient is as follows: Set multiple Z-axis compensation test quantities; Record the change in the focal height of the welding laser beam generated by the galvanometer under each Z-axis compensation test value; The compensation conversion coefficients are obtained by linearly fitting multiple Z-axis compensation test values ​​and their changes.

[0009] As a further embodiment of the present invention, in step S2, when the camera acquires an image of the workpiece to be welded, the camera's optical axis is perpendicular to the workpiece to be welded, and all welding points are within the camera's field of view.

[0010] As a further embodiment of the present invention, in step S4, the displacement sensor is disposed at the end of the robot and positioned in front of the galvanometer on the flight welding path.

[0011] As a further embodiment of the present invention, the displacement sensor is a line laser displacement sensor, wherein the measuring laser beam generated by the displacement sensor and the welding laser beam generated by the galvanometer are parallel to each other and perpendicular to the workpiece to be welded.

[0012] As a further aspect of the present invention, in step S5, the Z-axis compensation amount... The calculation method is as follows:

[0013] in: To compensate for the conversion coefficient; , This refers to the actual height of the welding point. This is the standard welding height.

[0014] As a further embodiment of the present invention, in step S6, before the robot reaches the position corresponding to each welding coordinate, the galvanometer is zeroed on the Z-axis.

[0015] A real-time Z-axis compensation system for flight welding, used to implement the real-time Z-axis compensation method as described above, comprising: The robot's end effector moves along a pre-set flight welding path; A galvanometer, located at the end of the robot, is used to generate a welding laser beam to weld the workpiece. A camera used to capture images of the workpiece to be welded; The image processing module is connected to the camera, receives images, and extracts the pixel coordinates of each welding point in the image; A coordinate transformation module, which is connected to the image processing module and stores the transformation relationship, is used to receive pixel coordinates and transform the pixel coordinates to the robot coordinate system based on the transformation relationship to obtain the robot's welding coordinates; Displacement sensors are used to collect the actual height of each welding point; The compensation calculation module is connected to the displacement sensor and stores the standard welding height and compensation conversion coefficient. It is used to calculate the difference between the actual height and the standard welding height, and to calculate the Z-axis compensation based on the difference and the compensation conversion coefficient. The galvanometer controller, connected to the compensation calculation module, is used to control the galvanometer to perform Z-axis compensation based on the Z-axis compensation amount when the robot reaches the position corresponding to the welding coordinate.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. During the flight welding process, the Z-axis compensation of the galvanometer is performed in real time based on the height of the position to be welded. Compared with the traditional serial process of scanning first, then transmitting, and then welding, the production cycle can be shortened and the production efficiency can be improved.

[0017] 2. The galvanometer and displacement sensor are installed and move synchronously with the robot end effector, and their relative positions are fixed. During the flying welding process, the cumulative error caused by the series movement of multiple mechanisms such as robot joint movement and external axis movement can be avoided. There is no need to repeatedly calibrate the standard welding height, which reduces the difficulty of on-site debugging.

[0018] 3. The displacement sensor is positioned at a fixed distance ahead of the galvanometer on the flight welding path, allowing it to collect the actual height of each welding point before the galvanometer. This enables real-time Z-axis compensation of the galvanometer based on the actual height, and also makes the overall system layout more compact. Attached Figure Description

[0019] Figure 1 A flowchart of a real-time Z-axis compensation method for flight welding; Figure 2 A flowchart of a real-time Z-axis compensation system for flight welding; Figure 3 This is a schematic diagram of aerial welding.

[0020] Figure labels: 1-Robot, 2-Displacement sensor, 3-Galvanometer. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] Example 1 like Figure 2 As shown, this embodiment first proposes a real-time Z-axis compensation system for flying welding, including a robot 1, a galvanometer 3, a camera, and a displacement sensor 2.

[0024] like Figure 3 As shown, robot 1 has an end effector that moves along a preset welding path. A galvanometer 3 is positioned at the end effector of robot 1 to generate a welding laser beam to weld the workpiece. A camera is used to acquire images of the workpiece to be welded. A displacement sensor 2 is used to acquire the actual height of each welding point.

[0025] Displacement sensor 2 is rigidly connected to the end effector of robot 1 to move with the end effector. Galvanometer 3 is also rigidly connected to the end effector of robot 1. The rigid fixation of both displacement sensor 2 and galvanometer 3 to the end effector of robot 1 prevents the relative positions of displacement sensor 2 and galvanometer 3 from shifting, thereby avoiding damage to calibration parameters and reducing the workload of on-site debugging.

[0026] Displacement sensor 2 is positioned a fixed distance ahead of galvanometer 3 along the welding path. During workpiece welding, the end effector of robot 1 drives displacement sensor 2 to move along the welding path. Displacement sensor 2 arrives at the welding position before galvanometer 3, thus predicting the height of the welding position. As galvanometer 3 moves along the welding path with the end effector of robot 1, it emits a welding laser beam to perform flying welding on the workpiece.

[0027] The galvanometer 3 includes a galvanometer body and a Z-axis motor. The galvanometer body 3 is used to generate a welding laser beam. Preferably, the displacement sensor 2 is a linear laser displacement sensor 2, whose measuring laser beam is parallel to and perpendicular to the centerline of the welding laser beam generated by the galvanometer 3 and to the surface of the workpiece to be welded. The Z-axis motor drives the galvanometer body to move vertically so that the welding laser beam is focused at the height of the position to be welded. In this embodiment, the Z-axis motor is a linear motor to improve the response speed and positioning accuracy of Z-axis compensation.

[0028] The system also includes an image processing module, a coordinate transformation module, a compensation calculation module, and a galvanometer controller.

[0029] The image processing module is connected to the camera and is used to receive images captured by the camera and extract the pixel coordinates of each welding point in the image. In this embodiment, when the camera captures an image of the workpiece to be welded, the camera's optical axis is perpendicular to the workpiece, and all welding points are within the camera's field of view to ensure that each welding point can be clearly imaged.

[0030] The coordinate transformation module is connected to the image processing module and stores the transformation relationship between the camera and robot 1 coordinate systems. The coordinate transformation module receives the pixel coordinates output by the image processing module and transforms the pixel coordinates to the robot 1 coordinate system based on the transformation relationship to obtain the welding coordinates of robot 1.

[0031] The transformation relationship between the camera and robot 1 coordinate system is obtained through calibration, specifically including the rotation matrix and translation matrix between the camera and robot 1 coordinate systems, which are obtained through hand-eye calibration.

[0032] The compensation calculation module is connected to displacement sensor 2 and stores the standard welding height and compensation conversion coefficient. The compensation calculation module receives the actual height of each welding point collected by displacement sensor 2, calculates the difference between the actual height and the standard welding height, and calculates the Z-axis compensation based on the difference and the compensation conversion coefficient.

[0033] The galvanometer controller is connected to the compensation calculation module and is used to control the galvanometer 3 to perform Z-axis compensation based on the Z-axis compensation amount when the robot 1 reaches the position corresponding to the welding coordinate. Preferably, the galvanometer controller is connected to the displacement sensor 2 via an industrial real-time Ethernet bus, which includes, but is not limited to, PROFINET and EtherCAT buses. The industrial real-time Ethernet bus transmits data directly to the galvanometer controller with a microsecond delay. Compared with the traditional serial link of "scanning-processing-PLC-galvanometer", this embodiment can realize "pre-scanning while moving", which greatly improves the response speed of the galvanometer 3's Z-axis compensation.

[0034] Before robot 1 reaches the position corresponding to each welding coordinate, galvanometer 3 is zeroed on the Z-axis. That is, before robot 1 is about to reach each welding point, the galvanometer controller controls the Z-axis motor to reset galvanometer 3 to zero, and then performs compensation actions according to the compensation amount to ensure that the starting position of each compensation is consistent and improve the compensation accuracy.

[0035] Example 2 like Figure 1 As shown, this embodiment proposes a real-time Z-axis compensation method for in-flight welding, based on the system implementation of Embodiment 1. The method includes the following steps: S1, through calibration, obtains the transformation relationship between the camera and robot 1 coordinate systems, the standard welding height, and the compensation transformation coefficient.

[0036] S11, the transformation relationship between the camera and robot 1 coordinate systems includes the rotation and translation matrices between the camera and robot 1 coordinate systems, obtained through hand-eye calibration. The specific method is as follows: The calibration plate is placed horizontally at the welding station. Images of the calibration plate are captured by a camera, and the pixel coordinates of each calibration point on the calibration plate are extracted. The robot 1 moves the galvanometer 3, so that the red light from the origin of the galvanometer 3 is sequentially projected onto each marker point, and the coordinates of the robot 1 at this time are recorded. The pixel coordinates of each calibration point and the corresponding robot 1 coordinates are subjected to multi-point spatial fitting to obtain the rotation matrix and translation matrix between the camera and robot 1 coordinate systems.

[0037] S12, the standard welding height calibration method is as follows: Zero the galvanometer 3 along the Z-axis; measure the height of the focal point of the welding laser beam generated by the galvanometer 3 using the displacement sensor 2 as the standard welding height. .

[0038] S13, the calibration method for the compensation conversion coefficient is as follows: Set up multiple Z-axis compensation test parameters; record the change in the focal height of the welding laser beam generated by galvanometer 3 under each Z-axis compensation test parameter; perform linear fitting between the multiple Z-axis compensation test parameters and the change values ​​to obtain the compensation conversion coefficient. .

[0039] For example, a reference plane is set, which can be any plane, and the welding laser beam and the measuring laser beam are perpendicular to the reference plane. The placement plane of the workpiece to be welded can be used as the reference plane, and n measuring blocks of different heights can be placed on the reference plane. The height of each measuring block relative to the reference plane is measured by displacement sensor 2. ,in:

[0040] in The height of the nth measuring block; Adjust the height of the galvanometer body so that its welding laser beam is focused at the height of the reference plane. Then, control the vertical movement of the galvanometer body via the Z-axis motor so that its welding laser beam is focused on the top of each test block. Record the set H of the galvanometer's Z-axis compensation test quantities at this time, where:

[0041] in The Z-axis compensation measurement of galvanometer 3 when the focal point of the welding laser beam moves from the reference plane to the top of the nth test block; For n data pairs Perform linear fitting to obtain the compensation conversion coefficients. ; in i .

[0042] S2: Acquire images of the workpiece to be welded using a camera, and extract the pixel coordinates of each welding point in the image.

[0043] After the workpiece enters the welding station, the camera takes pictures of the workpiece to be welded, capturing images containing each welding point. The image processing module receives the image and extracts the pixel coordinates of each welding point in the image through an image recognition algorithm.

[0044] S3, based on the transformation relationship, transform the pixel coordinates to the robot 1 coordinate system to obtain the welding coordinates of robot 1.

[0045] The coordinate transformation module receives the pixel coordinates of each welding point from the image processing module and calls the calibrated transformation relationship (rotation matrix and translation matrix) between the camera and robot 1 coordinate systems to convert the pixel coordinates of each welding point into welding coordinates in the robot 1 coordinate system. These welding coordinates are the target positions that the robot 1 end effector needs to move to during welding.

[0046] S4. The actual height of each welding point is collected by displacement sensor 2, and the difference between the actual height and the standard welding height is calculated.

[0047] As robot 1 moves along the welding path, displacement sensor 2 pre-scans the welding position along the welding path and collects the actual height of each welding point. Displacement sensor 2 will collect the actual height of each welding point. The data is then transmitted to the compensation calculation module. The compensation calculation module calculates the actual height of each welding point. Standard welding height The difference between ,in:

[0048] S5. Calculate the Z-axis compensation amount based on the difference and compensation conversion coefficient. .

[0049]

[0050] when When the value is positive, it indicates that the height of the position to be welded is above the focusing height of the welding laser beam, and the galvanometer body needs to be moved upward by the Z-axis motor. Conversely, when When the value is negative, the galvanometer body is moved downwards via the Z-axis motor. .

[0051] S6, when robot 1 reaches the position corresponding to the welding coordinate, galvanometer 3 performs Z-axis compensation based on the Z-axis compensation amount.

[0052] The end effector of robot 1 moves sequentially along the preset flight welding path to the position corresponding to the welding coordinates. When the welding laser beam emitted by galvanometer 3 is aligned with the welding position on the plane, the controller of galvanometer 3 controls the Z-axis motor to compensate by the Z-axis amount. The galvanometer body is moved vertically to perform Z-axis compensation on galvanometer 3. Then, galvanometer 3 emits light to perform welding. The welding laser beam emitted by galvanometer 3 is aligned with the welding position in both plane and height. Before robot 1 reaches the position corresponding to each welding coordinate, galvanometer 3 returns to zero on the Z-axis. That is, before robot 1 reaches each welding point, the galvanometer 3 controller controls the Z-axis motor to reset galvanometer 3 to zero, and then performs compensation actions according to the compensation amount to ensure that the starting position of each compensation is consistent and improve compensation accuracy.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A real-time Z-axis compensation method for flight welding, characterized in that, Includes the following steps: S1, through calibration, the transformation relationship between the camera and robot (1) coordinate system, the standard welding height and the compensation transformation coefficient are obtained; S2, acquire images of the workpiece to be welded using a camera, and extract the pixel coordinates of each welding point in the image; S3, based on the transformation relationship, the pixel coordinates are transformed into the robot (1) coordinate system to obtain the welding coordinates of the robot (1); S4, the actual height of each welding point is collected by the displacement sensor (2), and the difference between it and the standard welding height is calculated; S5. Calculate the Z-axis compensation amount based on the difference and the compensation conversion coefficient; S6, when the robot (1) reaches the position corresponding to the welding coordinate, the galvanometer (3) performs Z-axis compensation based on the Z-axis compensation amount.

2. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S1, the transformation relationship between the camera and robot (1) coordinate system includes the rotation matrix and translation matrix between the camera and robot (1) coordinate system, which are obtained through hand-eye calibration.

3. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S1, the method for calibrating the standard welding height is as follows: Set the galvanometer (3) to zero along the Z-axis; The height of the focal point of the welding laser beam generated by the galvanometer (3) is measured by the displacement sensor (2) as the standard welding height.

4. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S1, the calibration method for the compensation conversion coefficient is as follows: Set multiple Z-axis compensation test quantities; Record the change in the focal height of the welding laser beam generated by the galvanometer (3) under each Z-axis compensation test value; The compensation conversion coefficients are obtained by linearly fitting multiple Z-axis compensation test values ​​and their changes.

5. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S2, when the camera acquires an image of the workpiece to be welded, the camera's optical axis is perpendicular to the workpiece to be welded, and all welding points are within the camera's field of view.

6. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S4, the displacement sensor (2) is placed at the end of the robot (1) and positioned in front of the galvanometer (3) on the flight welding path.

7. The instant Z-axis compensation method for flight welding according to claim 1, characterized in that, The displacement sensor (2) is a line laser displacement sensor (2). The measuring laser beam generated by the displacement sensor (2) and the welding laser beam generated by the galvanometer (3) are parallel to each other and perpendicular to the workpiece to be welded.

8. A real-time Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S5, the Z-axis compensation amount The calculation method is as follows: in: To compensate for the conversion coefficient; , This refers to the actual height of the welding point. This is the standard welding height.

9. A real-time Z-axis compensation method for flight welding according to claim 1, characterized in that, In step S6, before the robot (1) reaches the position corresponding to each welding coordinate, the galvanometer (3) is zeroed on the Z-axis.

10. A real-time Z-axis compensation system for flight welding, characterized in that, It is used to implement the Z-axis instantaneous compensation method as described in any one of claims 1-9, and includes: The robot (1) moves its end effector along a preset flight welding path; A galvanometer (3) is set at the end of the robot (1) to generate a welding laser beam to weld the workpiece; A camera used to capture images of the workpiece to be welded; The image processing module is connected to the camera, receives images, and extracts the pixel coordinates of each welding point in the image; The coordinate transformation module is connected to the image processing module and stores the transformation relationship. It is used to receive pixel coordinates and transform the pixel coordinates to the robot (1) coordinate system based on the transformation relationship to obtain the welding coordinates of the robot (1). Displacement sensor (2) is used to collect the actual height of each welding point; The compensation calculation module is connected to the displacement sensor (2) and stores the standard welding height and compensation conversion coefficient. It is used to calculate the difference between the actual height and the standard welding height, and to calculate the Z-axis compensation based on the difference and the compensation conversion coefficient. The galvanometer controller, connected to the compensation calculation module, is used to control the galvanometer (3) to perform Z-axis compensation based on the Z-axis compensation amount when the robot (1) reaches the position corresponding to the welding coordinate.

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