A device and method for controlling the gap and step difference in laser welding based on multi-sensor coupling of vision and force.

Abstract

This invention provides a device and method for controlling the gap and step difference in laser welding using a multi-sensor coupling of vision and force, relating to the field of laser welding. The device includes a vision sensing system, a force sensing system, a laser welding system, and a feedback control system. The vision sensing system includes an image projector, a CCD camera, and a support; the force sensing system includes a flexible pressure sensor, a vertical axis, and a motor control cabinet; the laser welding system includes a laser, a control box, a robot, and a laser welding head. The method employs a multi-sensor coupling approach of vision and force to adaptively weld the gap and step difference of thin-walled structural components, broadening the laser welding process window and achieving precise welding of larger gaps and step differences. This invention solves the problem of difficult welding caused by large gaps and step differences in the laser welding process of thin-walled structural components, and features fast response speed and high accuracy, effectively improving the precision and quality of laser welding of thin-walled structural components.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, specifically relating to a laser welding gap and step control device and method based on the coupling of vision and force multi-sensor. Background Technology

[0002] In the aerospace industry, especially in the manufacturing of critical aircraft structures, thin-walled structural components are increasingly used to reduce weight and improve manufacturing processes. For joining thin-walled parts, laser welding can not only produce high-strength, continuous, and smooth welds, but also increase the tensile strength of the welded parts, achieving the effects of weight reduction, material saving, and improved performance.

[0003] However, due to pre-processing and clamping errors of thin-walled structural components before welding, as well as the influence of thermal deformation during the welding process, thin-walled components with low stiffness and poor stability are prone to instability even under relatively small welding stresses, exhibiting obvious local deflection and torsion deformations. This makes it difficult to achieve the welding requirements of zero gap and zero step difference in actual production. During welding, the laser beam is focused into a very small area, resulting in a narrow process window. This places extremely stringent requirements on the gap and step difference of the welded structural components. Excessive gap and step difference will reduce welding stability, easily leading to welding defects and affecting the quality of joint formation.

[0004] The commonly used welding quality control method mainly relies on post-weld inspection. However, post-weld inspection is time-consuming, labor-intensive, and has a certain degree of lag, making it impossible to adjust the weld gap and step difference in real time. With the continuous development of science and technology, there is an urgent need for a precision laser welding device and method that can monitor and adjust the gap and step difference in real time, and adjust process parameters according to the dynamic changes in the gap and step difference during the welding process of thin-walled structural parts to ensure the quality of the welded joint. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an adaptive adjustment device and method for controlling the gap and step difference of laser welding welds in thin-walled structural components, which offers high precision and welding efficiency.

[0006] The principle of this invention is as follows: the weld gap is monitored by a coaxial vision sensing system carried by a robot; the weld step difference is measured by a pre-fixed force sensing system; the feedback control system performs coupling processing based on the information returned by the vision and force sensing systems, and adjusts the process parameters and pressure in real time to ensure that the gap and step difference are within the tolerance range.

[0007] The technical solution adopted in this invention is as follows:

[0008] A device and method for controlling weld gap and step difference in laser welding based on multi-sensor coupling of vision and force, characterized by comprising a vision sensing system, a force sensing system, a laser welding system, and a feedback control system. The vision sensing system includes an image projector, a CCD camera, and a support, used for real-time acquisition of weld gap morphology during the welding process; the force sensing system includes a flexible pressure sensor, a vertical axis, and a motor control cabinet, used for real-time measurement and acquisition of weld step difference during the welding process; the laser welding system includes a laser, a control box, a robot, and a laser welding head, used for welding thin-walled structural components; the feedback control system receives image and digital information from the vision and force sensing systems, performs three-dimensional reconstruction after data processing, and makes decisions to control welding deformation by adjusting process parameters.

[0009] A method for controlling the gap and step difference in laser welding based on multi-sensor coupling of vision and force includes the following steps: establishing a multi-sensor coupling database, embedding a "welding deformation-parameter adjustment" algorithm, and setting tolerance ranges for gap and step difference; comparing the welding gap and step difference obtained in real time from the multi-sensor system with the tolerance range to determine whether they are within the range; if they are within the range, welding continues; if they exceed the tolerance range, the "welding deformation-parameter adjustment" algorithm is called to solve for optimal parameters and the results are fed back to each system for feedback adjustment; for gap and step difference adjustment, the laser power P, welding speed V, wire feed speed v, and pressure h can be adjusted until the gap and step difference are within the tolerance range.

[0010] The method for establishing a multi-sensor coupled database is as follows: A high-precision laser welding monitoring platform for thin-walled structural components is built based on visual and force sensing units; the non-uniform gaps and step differences appearing in the thin-walled structural components are monitored, and the gap is monitored and collected during welding through a visual sensing system; the displacement of the thin-walled structural components is monitored and processed during welding through a force sensing system; laser welding experiments with different gaps and step differences as single variables are designed, the process parameters and pressure are adjusted, and the real-time changes in gap and step difference are recorded; based on the experimental data, the mapping relationship between "process parameters-heat input-gap and step difference" is determined, the "welding deformation-parameter adjustment" algorithm is developed, a welding process database is established, and the tolerance range of gap and step difference is determined;

[0011] Furthermore, in the visual sensing system, structured light emitted by the image scanner provides an auxiliary light source, and a filter with a wavelength of 800-1000nm is installed in front of the CCD camera to match it.

[0012] Furthermore, in the force sensing system, the patch-type flexible pressure sensor is located at the bottom of the vertical axis, and the vertical axis is controlled by a motor driven by the motor control cabinet to lift and lower.

[0013] Furthermore, the flexible pressure sensor in the force sensing system is subjected to force when a step difference occurs in the thin-walled structural component. The force is transmitted back to the feedback control system, and the position coordinates are calculated through force coordinate transformation, thereby realizing the monitoring of minute displacements.

[0014] Furthermore, the image processing steps of the feedback control system are as follows: noise reduction is performed through image filtering to preserve image edge information; the image grayscale is divided into K levels, n i Let n be the number of pixels with gray level i. The total number of pixels in the image is: n = n0 + n1 + ... + n K- 1. The probability that a pixel has a gray level of i is: For the entire image Set the image grayscale threshold to T(x) = x (0 < x < L-1). Use the threshold to divide the image grayscale into H1 and H2. The probability of a pixel grayscale being assigned to H1 is... The probability that a pixel grayscale value is assigned to H2 is The average gray value of the pixels assigned to H1 is The average grayscale value of the pixels assigned to H2 is The pixel is the average gray value of the entire image. Then use This represents the non-uniformity of pixel grayscale values, where σ B To find the between-class variance, solve for σ. B The maximum value is the optimal threshold. According to the threshold The image is binarized to extract the weld contour and gap information;

[0015] Furthermore, the feedback control system receives and processes the incoming image and digital information, and reconstructs the real-time three-dimensional model of welding on the control screen according to the gap and step difference characteristics, thereby realizing the coupling of multiple sensor systems.

[0016] Furthermore, the plate thickness t ranges from 1 to 2 mm, the welding gap a ranges from 0 to 0.8 mm, and the step difference b ranges from 0 to 0.5 mm;

[0017] Furthermore, the algorithm solves for the optimal parameters (P, V, v, h), where the laser power P ranges from 800 to 3000 W; the welding speed V ranges from 0.6 to 2.0 m / min; the wire feed speed v ranges from 0 to 2 m / min; and the downward pressure h ranges from 0 to 0.3 mm.

[0018] The advantages and positive effects of this invention are as follows:

[0019] This invention relates to a device and method for controlling weld gap and step difference in laser welding based on the coupling of vision and force sensors. Employing a vision and force multi-sensor system as the means of acquiring welding information, it enables real-time monitoring of weld gap and step difference during the welding process and facilitates 3D reconstruction and observation of thin-walled structural components. This invention couples vision and force sensors and uses algorithm analysis to achieve real-time correction and control of weld gap and step difference, solving the problem of difficult welding caused by large variations in gap and step difference during the laser welding process of thin-walled structural components, effectively improving the accuracy and quality of laser welding of thin-walled structural components. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall welding equipment of the laser welding gap and step difference control device and method based on the coupling of vision and force perception multi-sensor, as described in this invention.

[0021] Figure 2 This is a schematic diagram of the computer screen processing results of the feedback control system described in this invention.

[0022] Figure 3 This is a flowchart of the weld gap and step difference control method described in this invention.

[0023] Figure 4 This is a flowchart of the multi-sensor coupling database establishment process for the weld gap and step difference control method described in this invention.

[0024] Figure 5 This is a schematic diagram of the weld gap and step difference in the welding process described in this invention.

[0025] Figure 6 This is a partial enlarged view of the welding equipment described in this invention.

[0026] In the picture:

[0027] The visual sensing system includes: 11-image projector; 12-CCD camera; 13-stand;

[0028] The force sensing system includes: 21-flexible pressure sensor; 22-vertical axis; 23-motor control cabinet;

[0029] The laser welding system includes: 31-laser; 32-control box; 33-robot; 34-laser welding head;

[0030] The feedback control system includes: 41-computer control console; Detailed Implementation

[0031] To facilitate understanding by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0032] See Figure 1 In this example, the laser welding gap and step difference control device and method based on multi-sensor coupling of vision and force mainly includes a vision sensing system, a force sensing system, a laser welding system, and a feedback control system. The vision sensing system, including an image projector, a CCD camera, and a support, is used for real-time acquisition of the weld gap morphology during the welding process. The force sensing system, including a flexible pressure sensor, a vertical axis, and a motor control cabinet, is used for real-time measurement and acquisition of the weld step difference during the welding process. The laser welding system, including a laser, a control box, a robot, and a laser welding head, is used for laser welding operations on thin-walled structural components. The feedback control system receives image and digital information from the vision and force sensing systems, performs three-dimensional reconstruction after data processing, and makes decisions to adjust welding deformation in real time.

[0033] See Figure 2 The feedback control system receives and processes images and digital information from the visual and force sensing systems. The images are filtered, denoised, thresholded, and binarized to extract the weld contour and gap information. The digital information is calculated to obtain the position coordinates through force coordinate transformation. Finally, the real-time three-dimensional model of the welding is reconstructed on the control screen based on the gap and step difference characteristics, realizing the coupling of multiple sensing systems.

[0034] See Figure 3 The method for controlling weld gap and step difference for plate thickness t of 1-2mm includes the following steps: Conduct experiments to determine the mapping relationship between "process parameters - heat input - gap and step difference", establish a multi-sensor coupled database, embed a "welding deformation - parameter adjustment" algorithm, and set tolerance ranges for gap and step difference; compare the weld gap and step difference obtained from real-time acquisition and processing by the multi-sensor system with the tolerance range to determine whether they are within the range. If they are within the range, welding continues; if they exceed the tolerance range, the "welding deformation - parameter adjustment" algorithm is called to solve for optimal parameters and the results are fed back to each system for feedback adjustment; for gap and step difference adjustment, the laser power P, welding speed V, wire feed speed v, and downward pressure h can be adjusted until the gap and step difference are within the tolerance range.

[0035] See Figure 4 The method for establishing a multi-sensor coupled database is as follows:

[0036] (1) A high-precision laser welding platform for thin-walled structural components was built by combining visual sensing and force sensing system units.

[0037] (2) Use a bracket to fix the image projector and CCD camera on the welding robot. Install a filter in front of the CCD camera to filter wavelengths of 800-1000nm.

[0038] (2) To monitor the uneven gaps and step differences that occur in thin-walled structural components during the welding process, the gaps are monitored and collected during welding through a visual sensing system; the displacement of thin-walled structural components is monitored and processed during welding through a force sensing system.

[0039] The gap captured by the camera is filtered and denoised, thresholded, and binarized to extract the weld contour and gap information. The flexible pressure sensor is subjected to force when a step difference occurs in the thin-walled structure. The force is transmitted back to the feedback control system, where the position coordinates are calculated through force coordinate transformation, thereby realizing the monitoring of minute displacements.

[0040] (3) Design laser welding experiments with different gaps and different step differences as single variables, adjust process parameters and pressure, and record real-time changes in gap and step difference.

[0041] (4) The adjusted process parameters are (P, V, v, h), where the laser power P ranges from 800 to 3000 W; the welding speed V ranges from 0.6 to 2.0 m / min; the wire feed speed v ranges from 0 to 2 m / min; and the downward pressure h ranges from 0 to 0.3 mm. The feedback control system receives and processes the incoming image and digital information, and reconstructs the real-time three-dimensional welding model on the control screen based on the gap and step difference characteristics, thereby realizing the coupling of multiple sensor systems.

[0042] (4) Based on experimental data, determine the mapping relationship between “process parameters-heat input-gap and step difference”, develop the “welding deformation-parameter adjustment” algorithm, establish a welding process database, and determine the tolerance range of gap and step difference.

[0043] See Figure 5 Due to pre-processing and assembly errors, as well as the influence of thermal deformation during the welding process, the unwelded areas deform during actual welding, resulting in gaps and step differences, which reduces welding stability, easily leads to welding defects, and reduces the quality of joint formation.

[0044] See Figure 6 During the welding process, the vision and force sensing system collects gap and step difference information in real time. After the feedback control system makes a decision, it adjusts parameters such as wire feed speed v and laser power P to meet the requirements of laser welding process. The step difference is reduced and the welding stability is improved by adjusting the downward pressure h.

[0045] It should be understood that the above-described embodiments are merely exemplary and not restrictive. Those skilled in the art can obviously make various modifications to this example. Therefore, the present invention is not limited to the examples described herein. Any simple modifications or substitutions made to the above details within the spirit and essence of the present invention will be included within the scope of the claims of the present invention.

Claims

1. A method for laser welding seam gap and step difference control based on visual and force sensing multi-sensor coupling, mainly using the following devices including visual sensing system, force sensing system, laser welding system and feedback control system, wherein: The visual sensing system is used for real-time collection of the weld gap profile during welding, including an image projector (11), a CCD camera (12) and a bracket (13); the structured light emitted by the image projector is irradiated on the thin-walled structure, the CCD camera captures the weld gap image, the image projector and the CCD camera are fixed on the welding robot through the bracket to realize coaxial monitoring, the distance and angle between the image projector and the CCD camera are adjusted to realize different angle weld gap image collection; The force sensing system is used for real-time measurement and collection of the weld step difference during welding, including a flexible pressure sensor (21), a vertical shaft (22) and a motor control cabinet (23); the flexible pressure sensor is subjected to force when the step difference deformation of the thin-walled structure occurs, and returns feedback to the feedback system for data processing, and the pressure information is converted into displacement information, the motor control cabinet receives the control instructions from the feedback system to drive the vertical shaft to move, and the step difference of the thin-walled structure is corrected by pressing down; The laser welding system is used for welding the thin-walled structure, including a laser (31), a control box (32), a robot (33) and a laser welding head (34); the laser generates and transmits laser, the control box is used for controlling the travel route of the robot and receiving instructions from the feedback system to adjust the laser welding process parameters, and the laser welding head is used for adjusting and controlling the light beam; The feedback control system is used for sensing and decision-making during welding, including a computer console (41); the system receives images and digital information from the visual and force sensing systems, compares the real-time gap and step difference of the weld with the tolerance interval of the pre-set gap and step difference after data processing, continues to monitor if it is within the tolerance interval, and calls the "welding deformation-parameter adjustment" algorithm to solve the optimal process parameters and the down pressure amount for correcting the weld gap and step difference if it is beyond the tolerance interval; The feedback control system receives and processes the incoming images and digital information, and reconstructs a real-time three-dimensional model on the control screen according to the gap and step difference characteristics, realizing multi-sensor system coupling; The laser welding seam gap and step difference control method includes the following steps: establishing a multi-sensor coupling database, implanting the "welding deformation-parameter adjustment" algorithm, and setting the gap and step difference tolerance interval; comparing the real-time gap and step difference during welding with the tolerance interval, continuing welding if it is within the interval, and calling the "welding deformation-parameter adjustment" algorithm to solve the optimal process parameters and the down pressure amount if it is beyond the tolerance interval, and feeding back to each system for adjustment until the gap and step difference are within the tolerance interval. The multi-sensing coupling database establishment method is as follows: a laser welding platform for thin-walled structural members is built by combining a visual sensing system and a force sensing system; the gap and the step difference are monitored in real time by the visual sensing system and the force sensing system; laser welding experiments with different gaps and step differences as single variables are designed, the process parameters and the pressing amount are adjusted, and the gap and the step difference are recorded in real time; the mapping relationship among the process parameters, the heat input, the gap and the step difference is determined based on the experimental data, the "welding deformation-parameter adjustment" algorithm is developed, the welding process database is established, and the gap and step difference tolerance intervals are determined.

2. The method of claim 1, wherein the method is a method of controlling the gap and step of a laser welding seam based on the coupling of visual and force sensation. In the visual sensing system, the structure light emitted by the image scanner provides an auxiliary light source, and a filter is installed in front of the CCD camera, with a filtering range of 800-1000 nm.

3. The method of claim 1, wherein the method is a method of controlling the gap and step of a laser welding seam based on the coupling of visual and force sensing. In the force sensing system, the patch-type flexible pressure sensor is located at the lower part of the vertical shaft, and the motor control cabinet drives the vertical shaft to rise and fall according to the feedback of the pressing amount h, and the vertical shaft pressing adjusts the step difference deformation.

4. The method of claim 1, wherein the method is a method of controlling the gap and step of a laser welding seam based on the coupling of visual and force sensing. The force sensing system monitors the deformation of the thin-walled structural member. At the initial stage, the distance between the vertical shaft and the workpiece can be adjusted to be moderate. When the flexible pressure sensor is subjected to force when the thin-walled structural member produces step difference deformation, the feedback is returned to the feedback control system, the position coordinates are calculated through force coordinate conversion, and the monitoring of the micro displacement is realized.

5. The method of claim 1, wherein the method is a method of controlling the gap and step of a laser welding seam based on the coupling of visual and force sensing. The feedback control system carries out image processing step as follows: reducing noise by image filtering, protecting image edge information; dividing image gray scale into K levels, n i is the number of pixels with gray scale i, and the total number of pixels in the image is n = n0+ n1+... + n K-1 K, the probability of pixels with gray scale i is: , the total image has ; setting image gray threshold value as T(x) = x (0 < x < L-1), using threshold value to divide image gray scale into H1 and H2, the probability of pixel gray scale being divided into H1 is , the probability of pixel gray scale being divided into H2 is , the average gray scale value of pixels being divided into H1 is , the average gray scale value of pixels being divided into H2 is , the average gray scale value of pixels in the whole image is , then using to represent pixel gray scale value unevenness, wherein σ B is inter-class variance, solving the maximum value of σ B is the optimal threshold value ; according to threshold value , carrying out binary processing to extract weld seam contour and gap information.

6. The method of claim 1, wherein the method is a method of laser welding gap and step control based on visual and force sensing coupling. The thickness t of the plate ranges from 1 to 2 mm, the welding gap a ranges from 0 to 1.0 mm, and the step difference b ranges from 0 to 0.5 mm.

7. The method of claim 1, wherein the method is a method of laser welding gap and step control based on visual and force sensing coupling. The "welding deformation-parameter adjustment" algorithm obtains the optimal parameters (P, V, v, h), wherein P is the laser power, the value range is 800-3000 W; V is the welding speed, the value range is 0.6-2.0 m / min; v is the wire feeding speed, the value range is 0-2 m / min; and h is the pressing amount, the value range is 0-0.5 mm.

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