A three-dimensional reconstruction and automatic repair welding system for grinding roller surface and a control method thereof

Abstract

The application provides a three-dimensional reconstruction and automatic repair welding system for a grinding roller surface and a control method thereof. The system comprises a platform for supporting and rotating the grinding roller, a three-dimensional reconstruction assembly, a welding assembly and a controller. The platform comprises a rotating table, a motor, a frequency converter, an encoder, a PLC and other devices. The welding assembly comprises a welding gun, a stepping motor and other devices. The three-dimensional reconstruction assembly performs three-dimensional reconstruction on the surface of the grinding roller based on a line structured light camera. The controller controls the frequency converter, the encoder, the welding gun and other devices. The control method of the system comprises analyzing the defect distribution and size of the grinding roller according to a three-dimensional reconstruction model, and adjusting the rotation speed of the grinding roller according to the defects, so as to realize automatic repair welding of the wear defects of the grinding roller. The system can realize three-dimensional reconstruction of the surface of the grinding roller through the line structured light camera, and can realize automatic repair welding of the grinding roller through the collaborative work of the controller and the frequency converter, the encoder, the welding gun and other devices, so that the system has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application provides a three-dimensional reconstruction and automatic repair welding system for a grinding roller surface and a control method thereof, and particularly relates to the field of industrial metal part surface repair welding automation equipment. BACKGROUND

[0002] With the continuous development of manufacturing automation technology, grinding rollers are increasingly widely used, and the performance stability thereof is crucial to the continuous and reliable operation of the entire production line. How to realize automatic repair welding of the grinding roller surface is a key technical problem.

[0003] The grinding roller is an important component of a powder grinding system of equipment such as a vertical mill, and is mainly used for cooperative work with a grinding disc. When coarse materials are meshed into the grinding roller and the grinding disc, the grinding roller and the grinding disc move relatively, and the coarse materials are simultaneously subjected to the combined action of friction, extrusion force and shear force, and are ground into powder materials. Due to long-term grinding of hard impurities, the grinding roller surface often produces serious wear, which leads to an increase in the gap between the grinding roller and the grinding disc, a decrease in the operation efficiency of the equipment and an increase in energy consumption. In order to solve this problem, the factory often adopts hard surfacing technology to repair weld hard alloy on the grinding roller surface. The current commonly used repair welding technology is still mainly manual repair welding, and there are problems such as uneven repair welding quality, low repair welding efficiency, potential health risks of the repair welding environment to workers and the like. Three-dimensional reconstruction is an important research direction in the current field of intelligent manufacturing. Three-dimensional reconstruction of the grinding roller surface can identify and locate the distribution of the wear defects of the grinding roller surface, so as to realize targeted repair welding of the wear defects, and improve the repair welding quality, repair welding efficiency and repair welding process automation level of the grinding roller.

[0004] The existing patents are mostly from the aspects of optimizing the welding process, designing the quick replacement system of the grinding roller, and improving the performance of the welding wire material, in order to improve the grinding roller repair welding process level. Optimizing the welding process is to optimize the welding parameters and welding methods in the repair welding process. Patent CN103464868A discloses a process flow for cladding a hot-rolled support roller. Patent CN106378511A discloses a cladding process for a wear-resistant grinding roller. Patent CN106475661A discloses a cladding process for a wear-resistant grinding disc tile. Patent CN108655538A discloses a cladding method for a MPS-200 coal mill grinding roller and lining tile. Patent CN116890151A discloses an alloy wear-resistant roller repair welding process. They all improve the wear resistance of the wear-resistant layer and the repair welding quality by adjusting and optimizing the welding process, but the complex welding process also reduces the efficiency of the grinding roller repair welding. Designing the quick replacement system of the grinding roller is to optimize how to quickly assemble, disassemble and transport the grinding roller. Patent CN215711012U discloses a medium-speed coal mill grinding roller sleeve ejection device, which uses a hydraulic rod to eject the roller sleeve, uses a grab hook to clamp the roller sleeve, and uses an electric hoist to lift and lower, achieving quick ejection of the roller sleeve. However, compared with the time spent on grinding roller repair welding, it cannot effectively improve the efficiency of grinding roller repair welding. Improving the performance of the welding wire material is to optimize the forming performance of the repair welding wire. Patent CN119489293A discloses a high-alloy wear-resistant roller repair welding material, which has a large allowable welding current for the protective flux-cored wire, high deposition efficiency and good forming. However, the time period for optimizing the performance of the welding wire itself is long, the cost of optimizing the welding wire is high, and the cost of grinding roller repair welding is increased. In addition, patent CN205798649U discloses an automatic cladding equipment for a vertical mill and / or a coal mill, which places the grinding roller on a support and rotation platform and can complete the cladding work at one time. However, it does not realize automatic repair welding of the grinding roller wear defects, and the whole repair welding process lacks intelligence. SUMMARY

[0005] The purpose of the present application is to provide a grinding roller surface three-dimensional reconstruction and automatic repair welding system and a control method thereof. The system reconstructs the grinding roller surface by a line structured light camera, and controls the frequency converter, encoder, welding gun and other devices through the controller to realize targeted automatic repair welding of the grinding roller wear defects.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A grinding roller surface three-dimensional reconstruction and automatic repair welding system, characterized in that: it comprises a platform (1) for supporting and rotating a grinding roller (5), a three-dimensional reconstruction assembly (2), a welding assembly (3) and a controller (4),

[0008] The platform (1) comprises a rotating table (10), a motor (12) for driving the rotating table, an encoder (15) for measuring the rotating angle displacement, and a frequency converter (18) for adjusting the rotating speed of the motor, the three-dimensional reconstruction component (2) comprises a line structured light camera (21) for collecting the surface point cloud information of the grinding roller (5) and a conical calibration block (23), and the welding component (3) comprises a welding gun (31), a horizontal shaft stepping motor (33), a horizontal shaft screw (34), a vertical shaft stepping motor (35), and a vertical shaft screw (36).

[0009] The rotating table (10) is driven by a middle shaft (11), the middle shaft (11) is connected with the output shaft of a speed reducer (13) through a gear (14), the encoder (15) is connected with the output shaft of the speed reducer (13) through a shaft coupling (17), the motor (12) and the speed reducer (13) are fixedly arranged on the inner surface of the box body, the encoder (15) and a PLC (16) are fixedly arranged on the fixed support extending from the inner surface of the box body, the frequency converter (18) is fixedly arranged on the base, and the end position of the welding gun (31) is moved in the horizontal direction through the horizontal shaft stepping motor (33) and the horizontal shaft screw (34) and is moved in the vertical direction through the vertical shaft stepping motor (35) and the vertical shaft screw (36).

[0010] The controller (4) is used for connecting the line structured light camera (21), the PLC (16), the frequency converter (18), the welding gun (31), and the horizontal shaft stepping motor (33) and the vertical shaft stepping motor (35), and the functions of the controller (4) include running the grinding roller (5) surface three-dimensional reconstruction and automatic repair welding system and realizing the automatic repair welding function.

[0011] The PLC (16) sends the rotating angle displacement information stored in the register to the controller (4) in real time through the Modbus protocol, the controller (4) sends instructions to the specified register of the frequency converter (18) through the Modbus protocol and changes the motor frequency of the frequency converter (18) to adjust the rotating speed of the rotating table of the frequency converter (18), the controller (4) sends instructions to the welding gun (31) through the Modbus protocol to control the start and stop of welding and the adjustment of the welding parameters, and the controller (4) sends instructions to the motion control card, the single-chip microcomputer, or the stepping motor driver through the Modbus protocol, so that the horizontal shaft stepping motor (33) outputs the pulse to drive the horizontal shaft screw (34) to move, the vertical shaft stepping motor (35) outputs the pulse to drive the vertical shaft screw (36) to move, and the end position of the welding gun is controlled.

[0012] Further, the line structured light camera (21) of the three-dimensional reconstruction component (2) continuously collects single-frame point cloud information of the surface of the rotating grinding roller (5) by being fixed and not moving, and realizes the collection of three-dimensional point cloud information of the surface of the grinding roller (5) in combination with the angular displacement of the grinding roller (5).

[0013] In summary, a control method for grinding roller surface three-dimensional reconstruction and automatic repair welding, wherein the control method comprises the following steps:

[0014] Step S1: calibrate the camera extrinsic parameter k of the line structured light camera (21) and the center axis parameter m of the rotating scanning system z 、r w to obtain the transformation relationship matrix of the camera coordinate system and the world coordinate system in the mathematical model of the rotating scanning system; wherein k is the camera extrinsic parameter, indicating the transformation coefficient of the camera coordinate system and the world coordinate system;

[0015] Step S2: the grinding roller (5) rotates at a constant speed, the line structured light camera (21) continuously collects single-frame point cloud of the surface of the grinding roller (5) in the axial direction, the encoder (15) and the PLC (16) real-time acquire the angular displacement, and the controller (4) pre-processes each frame of point cloud, performs point cloud splicing and three-dimensional reconstruction on multiple frames of point cloud according to the transformation relationship obtained in step S1, and obtains a three-dimensional reconstruction model of the surface of the grinding roller (5);

[0016] Step S3: according to the three-dimensional point cloud information of the surface of the grinding roller (5) obtained in step S2, the grinding roller (5) is segmented in the axial direction, the segmented grinding roller (5) sheet is regarded as a cylinder, the cylinder point cloud is reduced to a two-dimensional plane based on the dimension reduction theory, and a two-dimensional polar coordinate point cloud is obtained;

[0017] Step S4: analyze the defect distribution position in the two-dimensional plane, and calculate the defect size based on the integral idea;

[0018] Step S5: according to the defect size and distribution position obtained by analyzing step S4, the output speed is calculated, and the speed is inversely proportional to the defect depth;

[0019] Step S6: according to the output speed calculated in step S5, the repair welding process of the welding gun (31) is controlled to realize the targeted repair welding of the defects of the grinding roller (5);

[0020] Step S7: after the targeted repair welding of the defects is completed, the surfacing of the grinding roller (5) is continued to increase the thickness of the wear-resistant layer.

[0021] Further, step S1 comprises:

[0022] The central axis of the rotating scanning system is quickly calibrated based on the cone calibration block (23). The calibration method is as follows: by fixing the cone calibration block (23) on the side wall of the rotating stage (10), the structured light projected by the line structured light camera (21) passes through the vertex of the cone, and the first frame image is captured. Then the rotating stage (10) rotates by an angle and the second frame image is captured. The central axis parameters of the rotating scanning system are obtained according to the geometric relationship between the two frames of images, and the transformation relationship matrix between the camera coordinate system and the world coordinate system in the mathematical model of the rotating scanning system is established.

[0023] In the rapid calibration of the central axis of the rotating scanning system, the coordinates of the vertex of the cone calibration block (23) in the first frame point cloud imaging on the Z-axis of the camera coordinate system are m. z The distance r between the vertex of the cone calibration block and the central axis of the rotational scan w The expressions include the following:

[0024]

[0025] Where k is the camera extrinsic parameter, representing the transformation coefficient between the camera coordinate system and the world coordinate system, α is the angle rotated by the rotary table, and r C and p C r represents the projected length of the camera images captured in the first and second frames onto the Z-axis of the camera coordinate system, respectively. w This is the distance between the vertex of the cone calibration block and the central axis of the rotational scan.

[0026] Furthermore, in step S2, the formula for converting two-dimensional coordinates to three-dimensional coordinates during point cloud stitching is: X = X c ×k, Y=[(Z c -m z )×k+r w ]×sinθ,Z=[(Z c -m z )×k+r w ]×cosθ;

[0027] Among them, (X) c Z c (X, Y, Z) represents the two-dimensional coordinates in the camera coordinate system, and (X, Y, Z) represents the three-dimensional coordinates in the world coordinate system. The parameter θ represents the angle of counterclockwise rotation of the grinding roller around the central axis. sinθ represents the sine value of the angle of counterclockwise rotation of the grinding roller around the central axis; cosθ represents the cosine value of the angle of counterclockwise rotation of the grinding roller around the central axis.

[0028] Furthermore, in step S3, the formula for reducing the cylindrical point cloud to a two-dimensional plane based on dimensionality reduction theory is as follows:

[0029]

[0030]

[0031] In the formula, (θ, R) is the polar coordinates of the point cloud after dimension reduction, θ is the same physical quantity as θ in step S2, indicating the rotation angle displacement of the point cloud of this frame from the first frame point cloud, X0 and X1 are the upper and lower limit values of the X coordinate of the slice; (X i , Y i , Z i ) are the three-dimensional coordinates of a plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice, t is the number of the plurality of point clouds, and R represents the average value of the radii of a plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice.

[0032] Further, in step S4, according to the starting angle θ1 and the ending angle θ2 of the defect, the absolute value of the difference between R i and the maximum fitting circle radius R max corresponding to all θ in the angle range is accumulated to obtain the defect area, and the calculation formula of the defect area is:

[0033] Where A is the defect area.

[0034] Further, in step S5, the rotation speed calculation formula is:

[0035]

[0036] In the formula, K and ε represent two constants respectively; wherein, the constant K represents the best corresponding relationship coefficient of the actual motor speed and the defect area; and the constant ε represents that when the grinding roller (5) is defect-free, i.e. A=0, the rotation speed v has an upper limit value.

[0037] Further, in step S6, the linkage control scheme of the controller (4) for targeted repair welding is: the controller (4) sends instructions to control the welding gun (31) to move to the grinding roller (5) slice position corresponding to the two-dimensional plane in step S4, and controls the frequency converter (18) to adjust the rotation table speed in real time according to the output rotation speed result of step S5 and the real-time rotation angle displacement feedback by the encoder (15), so as to perform targeted repair welding on the grinding roller (5) slice. And sequentially realize the repair welding on other grinding roller (5) slices, and finally realize the targeted repair welding on the surface defects of the entire grinding roller (5).

[0038] Further, in the step S7, the controller (4) controls the welding gun (31) to start repairing from the first slice position of the grinding roller (5), and after one round of repairing, the welding gun (31) steps to the next slice position along the axial direction to repair, and so on, until the whole grinding roller (5) is repaired for one round, then the welding gun (31) returns to the first slice position to repair the second layer, and the repairing is repeated until the thickness of the wear-resistant layer meets the requirement.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] The present application provides a grinding roller surface three-dimensional reconstruction and automatic repair welding system and a control method thereof. The system captures two frames of images of a conical block based on a line structured light camera, quickly calibrates the central axis of a rotary scanning system according to geometric relationships, and performs high-precision three-dimensional reconstruction of the grinding roller surface by the line structured light camera. The controller is used to control the frequency converter, encoder, welding gun and other devices to realize accurate positioning and automatic repair welding of the grinding roller wear defects. The three-dimensional reconstruction method proposed by the system has wide application range, high reconstruction accuracy and easy implementation. It can be used to quickly and accurately obtain three-dimensional point cloud information of the surface of any rotating member, and realize high-precision three-dimensional reconstruction of the surface of any rotating member through coordinate conversion and point cloud splicing. In the application of repairing the worn grinding roller surface, the system calculates and adjusts the rotating speed of the grinding roller in real time according to the size and distribution position of the defects, so that the repair amount of the welding gun at the defect position matches the defect depth, thereby realizing targeted repair welding of the grinding roller wear defects. The system realizes intelligent control of the whole grinding roller repair process through the controller, which not only improves the repair welding quality, but also greatly improves the repair welding efficiency, reduces manual intervention and labor intensity. The system also has a surfacing function, which can automatically perform multi-layer surfacing according to the thickness requirement of the wear-resistant layer, meet the grinding roller repair requirement, and further improve the service life of the grinding roller. The system has compact structure, close cooperation between components, stable and reliable operation, simple operation, flexible control, strong adaptability and other characteristics. It is not only suitable for different specifications of grinding rollers, but also can be quickly adjusted and optimized according to the actual working conditions, and has wide industrial application prospect. The system can realize three-dimensional reconstruction of the grinding roller surface through the line structured light camera, and realize automatic repair welding of the grinding roller through the cooperative work of the controller, frequency converter, encoder, welding gun and other devices. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a schematic diagram of the grinding roller of the embodiment of the present application;

[0042] Figure 2 It is a schematic diagram of the worn grinding roller of the embodiment of the present application;

[0043] Figure 3The schematic diagram of the overall system of the embodiment of the present application;

[0044] Figure 4 The schematic diagram of the platform of the overall system of the embodiment of the present application;

[0045] Figure 5 The schematic diagram of the three-dimensional reconstruction component of the overall system of the embodiment of the present application;

[0046] Figure 6 The schematic diagram of the welding component of the overall system of the embodiment of the present application;

[0047] Figure 7 The control flow chart of the control method of the embodiment of the present application;

[0048] Figure 8 The schematic diagram of the fast calibration system of the rotating scanning central axis of the embodiment of the present application;

[0049] Figure 9 The principle diagram of the fast calibration method of the rotating scanning central axis of the embodiment of the present application;

[0050] Figure 10 The control flow chart of the three-dimensional reconstruction method of the embodiment of the present application.

[0051] In the figure:

[0052] 1, platform; 2, three-dimensional reconstruction component; 3, welding component; 4, controller; 5, grinding roller; 10, rotating table; 11, central axis; 12, motor; 13, speed reducer; 14, gear; 15, encoder; 16, PLC; 17, coupling; 18, frequency converter; 19, box and its base; 21, line structured light camera; 22, camera mounting bracket; 23, conical calibration block; 31, welding gun; 32, column; 33, horizontal axis stepping motor; 34, horizontal axis screw; 35, vertical axis stepping motor; 36, vertical axis screw; 51, grinding roller wear defect. DETAILED DESCRIPTION

[0053] The present application will be further described below in conjunction with the drawings and embodiments.

[0054] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0055] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0056] like Figure 1 , 2 As shown in Figure 3, this embodiment provides a three-dimensional reconstruction and automatic welding system for the surface of worn grinding rollers, specifically for the practical application of automatic welding repair. The system includes a platform 1 for supporting and rotating the grinding roller, a three-dimensional reconstruction component 2, a welding component 3, and a controller 4. Figure 4 As shown, the platform includes a rotary table 10, a central shaft 11 located at the bottom center of the rotary table, a motor 12 for driving the rotary table, a reducer 13 used in conjunction with the motor, a gear 14 used between the central shaft and the reducer, an encoder 15 for measuring rotational angular displacement, a PLC 16 used in conjunction with the encoder, a coupling 17 for connecting the encoder and the reducer output shaft, a frequency converter 18 for adjusting the motor speed, and a housing and its base 19. All the various industrial control equipment components—motor 12, reducer 13, encoder 15, PLC 16, and frequency converter 18—are housed inside the housing and its base 19, improving equipment protection and electrical safety, and facilitating maintenance and management.

[0057] The motor 12 can be an AC motor or a servo motor. When using an AC motor, the frequency converter 18 can be used to adjust the speed. When using a servo motor, a servo driver can be used to adjust the speed. In this embodiment, the motor 12 drives the reducer 13 to work. The reducer 13 is connected to the central shaft 11 through a gear 14, driving the central shaft 11 to rotate. The central shaft 11 drives the rotary table 10 to rotate, and the rotary table 10 drives the grinding roller 5 to rotate. The motor 12 is a high-power AC motor. The frequency converter 18 changes the output speed of the motor 12 by changing the power supply frequency and voltage, so as to ultimately adjust the speed of the rotary table 10 and the grinding roller 5.

[0058] The encoder 15 can be an incremental encoder or an absolute encoder. When an incremental encoder is selected, it needs to be combined with limit devices such as limit switches and photoelectric sensors to reset the rotation pulse count when the rotational angular displacement reaches 360°. In this embodiment, the encoder 15 is connected to the output shaft of the reducer 13 via a coupling 17. When the output shaft of the reducer 13 rotates, the absolute encoder 15 generates a digital signal. The PLC 16 communicates with the encoder 15 via the MODBUS protocol and records the output signal of the encoder 15 in a designated register to realize the measurement of the rotational angular displacement of the rotary table 10.

[0059] like Figure 5 As shown, the three-dimensional reconstruction component 2 includes a line structured light camera 21, a camera mounting bracket 22, and a conical calibration block 23.

[0060] The camera mounting bracket 22 can be made of any material, have any shape, and be installed in any way. The fixed end of the bracket can be fixed to the housing and its base, or it can be fixed to the ground. In this embodiment, the camera mounting bracket 22 is an approximately L-shaped bracket, with one end fixed to the outer surface of the housing and the other end mounting the line structured light camera 21. The conical calibration block 23 is a detachable calibration block, which is fixed to the side wall of the rotary table 10 during system calibration and rotates with the rotary table 10.

[0061] The line structured light camera 21 projects structured light rays onto the surface of the grinding roller 5 each time it acquires a single frame image, and collects single-frame point cloud information along a single line on the surface of the grinding roller 5 in the axial direction. Each point cloud carries two-dimensional coordinate information, namely the length coordinate along the direction of the structured light ray and the depth coordinate of a point on the structured light ray, which are defined as X and X respectively in this embodiment. C Coordinates and Z C Coordinates. In this embodiment, in order to obtain the coordinate information of the third dimension of the point cloud on the surface of the grinding roller 5, a line structured light rotation scanning system and its mathematical model are established. The grinding roller 5 rotates at a constant speed, while the line structured light camera 21 remains stationary. Single-frame point cloud images of the surface at different rotational angular displacements θ during the rotation of the grinding roller 5 are continuously acquired. Each frame of point cloud image is preprocessed and its coordinates are transformed to be unified to the world coordinate system, thereby realizing the acquisition of three-dimensional point cloud information on the surface of the grinding roller 5.

[0062] like Figure 6 As shown, the welding assembly 3 includes a welding torch 31, a column 32 perpendicular to the ground, a horizontal axis stepper motor 33, a horizontal axis lead screw 34, a vertical axis stepper motor 35, and a vertical axis lead screw 36. The welding torch 31 includes a torch tip, a wire feeder, a welding machine, and other necessary welding equipment. Different welding processes can be used, and different welding equipment can be selected based on the specific welding process. The torch tip position adjustment mechanism can adopt different structures or different driving methods. In this embodiment, stepper motors and lead screws are used to move the end position of the welding torch 31. Both stepper motors and lead screws are fixed on a column 32 perpendicular to the ground. The horizontal axis stepper motor 33 and the horizontal axis lead screw 34 work together to move the welding torch in the horizontal direction, i.e., the X-axis direction. The vertical axis stepper motor 35 and the vertical axis lead screw 36 work together to move the welding torch in the vertical direction, i.e., the Z-axis direction. The horizontal axis stepper motor 33 and the vertical axis stepper motor 35 can be driven by devices such as motion control cards, microcontrollers, or stepper motor drivers. Through the coordinated operation of the two axes, the end of the welding torch 31 is moved to the position to be welded on the surface of the grinding roller 5.

[0063] The main control equipment for the three-dimensional reconstruction and automatic repair welding system of the grinding roller surface can be a PLC, PAC, industrial computer, etc.; the communication method between the main control equipment and other equipment can be Modbus, Ethernet, Profibus, etc. Figure 3 As shown, in this embodiment, the controller 4 is used to connect the line structured light camera 21, PLC 16, frequency converter 18, welding torch 31, and a controller that drives the stepper motor. It is used to run the control algorithm for the three-dimensional reconstruction and automatic welding system of the grinding roller surface and to realize the automatic welding function. After the line structured light camera 21 continuously acquires images, it stores the images in the built-in hard disk of the controller 4, awaiting further image processing. The PLC 16 sends the rotational angular displacement information stored in its register to the controller 4 in real time via the Modbus protocol. The controller 4 sends instructions to the designated register of the frequency converter 18 via the Modbus protocol to start or stop the motor 12 or change the frequency of the motor 12 to adjust the rotational speed of the rotary table. The controller 4 sends instructions to the welding torch 31 via the Modbus protocol to control the welding start and adjust the welding parameters. The controller 4 sends instructions to the motion control card, microcontroller, or stepper motor driver via the Modbus protocol, causing the stepper motor to output pulses to drive the lead screw, thereby controlling the end position of the welding torch 31.

[0064] In this embodiment, the human-machine interface of the host computer is divided into a camera connection module, a PLC communication module, a 3D reconstruction module, a defect identification module, a frequency converter communication module, and a welding torch control module. The camera connection module connects to the line structured light camera 21, calibrates the camera's extrinsic parameters and the central axis parameters of the rotating scanning system, displays real-time images, controls the line structured light camera 21 to continuously acquire point cloud images of the grinding roller 5 surface, and stores the images locally. The PLC communication module communicates with the PLC 16 and reads the rotational angular displacement information stored in the designated register of the PLC 16 in real time. The 3D reconstruction module preprocesses single-frame point cloud images, performs coordinate transformation and point cloud stitching on multiple frames of point cloud images, and performs 3D point cloud reconstruction on the surface of the grinding roller 5. The defect identification module... The separate module is used to perform slicing and dimensionality reduction processing on the point cloud 3D reconstruction model, analyze the distribution location and size of defects, and calculate the theoretical rotation speed of the corresponding rotary table 10 based on the defects; the inverter communication module is used to communicate with the inverter 18, change the value of the specified register in the inverter 18, and adjust the speed of the motor 12; the welding torch control module is used to control the welding torch 31 to start or stop welding, adjust the welding parameters of the welding torch 31, and send instructions to the drive devices corresponding to the horizontal axis stepper motor 33 and the vertical axis stepper motor 35 to realize the adjustment of the end position of the welding torch 31.

[0065] This embodiment also provides a control method for the above-mentioned three-dimensional reconstruction and automatic welding system for the surface of the grinding roller. The overall control method flowchart is as follows: Figure 7 As shown, it includes the following steps:

[0066] S1. Before starting the operation, the line structured light camera 21 is mounted on the camera mounting bracket 22 to acquire calibration images. The external parameter k of the line structured light camera 21 and the parameter m of the central axis of the rotating scanning system are controlled in the controller 4. z r w Calibration is performed to obtain the transformation matrix between the camera coordinate system and the world coordinate system in the mathematical model of the rotating scanning system. A schematic diagram of the rapid calibration system for the center axis of the rotating scanning system is shown below. Figure 8 As shown, the rapid calibration method is as follows: The cone calibration block 23 is fixed to the side wall of the rotary table 10, ensuring that the structured light rays projected by the line structured light camera 21 just pass through the apex of the cone. At this point, the first frame image is captured. Then, the rotary table rotates by an angle α, and the second frame image is captured. Figure 9 As shown, the central axis parameter m of the rotating scanning system is determined based on the geometric relationship between the two frames of images. z r w Let m be the coordinate of the cone calibration block 23 in the first frame point cloud image on the Z-axis of the camera coordinate system. z Solve for r w The formula is as follows: r C and p C r represents the projected length of the camera images captured in the first and second frames onto the Z-axis of the camera coordinate system, respectively. w Let α be the distance between the vertex of the cone calibration block and the center axis of the rotation scan, where k is the camera extrinsic parameter, representing the transformation coefficient between the camera coordinate system and the world coordinate system, and α is the angle through which the rotary table rotates.

[0067] S2. The grinding roller 5 rotates at a constant speed. The line structured light camera 21 continuously acquires single-frame point clouds along the axial direction of the grinding roller surface. The encoder 15 and frequency converter 16 acquire the rotational angular displacement in real time and send it to the controller 4. In the controller 4, each frame of point cloud is preprocessed. Based on the transformation relationship obtained in S1, and combined with the rotational angular displacement information θ corresponding to each frame, multiple frames of point clouds are stitched together and 3D reconstructed to obtain a 3D reconstructed model of the grinding roller 5 surface. The conversion formula from 2D coordinates to 3D coordinates during point cloud stitching is as follows:

[0068] X = X c ×k, Y=[(Z c -m z )×k+r w ]×sinθ,Z=[(Z c -m z )×k+r w ]×cosθ;

[0069] (X c , Y c , Z i ) are two-dimensional coordinates in the camera coordinate system, (X, Y, Z) are three-dimensional coordinates in the world coordinate system. The specific algorithm flow chart of three-dimensional reconstruction is shown in Figure 10 . As shown in Figure 9 , the parameter θ represents the angle of the grinding roller rotating counterclockwise around the central axis. sinθ represents the sine value of the angle of the grinding roller rotating counterclockwise around the central axis; cosθ represents the cosine value of the angle of the grinding roller rotating counterclockwise around the central axis.

[0070] S3, according to the three-dimensional point cloud information of the surface of the grinding roller 5 obtained in S2, the grinding roller 5 is sliced and segmented in the axial direction, the segmented grinding roller sheet is regarded as a cylindrical body, and the cylindrical point cloud (X, Y, Z) is reduced to a two-dimensional plane (R, θ) based on the dimension reduction theory, to obtain a two-dimensional polar coordinate point cloud, and the dimension reduction formula is: In the formula, (θ, R) is the polar coordinate of the reduced point cloud, θ is the same physical quantity as θ in step S2, representing the rotational angular displacement of the frame point cloud from the first frame point cloud, X0 and X1 are the upper and lower limit values of the X coordinate of the slice, (X i , Y i , Z i ) are three-dimensional coordinates of a plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice, t is the number of the plurality of point clouds, and R represents the average value of the radii of the plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice.

[0071] S4, analyze the distribution position of the grinding roller wear defect 51 in the two-dimensional plane, and calculate the size of the grinding roller wear defect 51 based on the integral idea. According to the starting angle θ1 and the ending angle θ2 of the grinding roller wear defect 51, the absolute value of the difference between R i and the maximum fitting circle radius R max corresponding to all θ in the angle range is accumulated to obtain the area A of the grinding roller wear defect 51, and the calculation formula is:

[0072] S5, according to the size and distribution position of the grinding roller wear defect 51 obtained by S4 analysis, calculate the output speed v, the speed is inversely proportional to the depth of the grinding roller wear defect 51, that is, the deeper the defect, the slower the speed, so as to increase the repair welding amount of the welding gun 31 at the defect, and the speed calculation formula is: In the formula, K and ε represent two constants, respectively; wherein, the constant K represents the optimal corresponding relationship coefficient between the actual motor speed and the area of the defect. The constant K is introduced to adjust the optimal corresponding relationship between the actual motor speed and the area of the grinding roller wear defect 51, and the constant ε is introduced to make the upper limit value of the speed v exist when the grinding roller 5 has no grinding roller wear defect 51, i.e. A = 0.

[0073] S6, the output speed calculated according to S5 is used to control the repair welding process of the welding gun 31, so as to realize the targeted repair welding of the grinding roller wear defect 51. The controller 4 sends a command to the controller driving the stepping motor to control the welding gun 31 to move to the position directly above the grinding roller slice corresponding to the two-dimensional plane in S4; the controller 4 sends a command to the frequency converter 18 to adjust the speed of the rotating table 10 in real time according to the output speed result of S5 and the real-time rotary angular displacement feedback by the encoder 15, so as to realize the targeted repair welding of the grinding roller slice. Steps S3 to S6 are repeated to realize the repair welding of other grinding roller slices, and finally the targeted repair welding of the grinding roller wear defect 51 on the surface of the entire grinding roller 5 is realized.

[0074] S7, after the targeted repair welding of the defect is completed, the surfacing of the grinding roller 5 is continued to increase the thickness of the wear-resistant layer. The controller 4 sends a command to the frequency converter 18 to drive the motor 12 to rotate the rotating table 10 at a constant speed, and controls the welding gun 31 to start repair welding from the first grinding roller slice position. After one circle of repair welding, the welding gun 31 steps to the next grinding roller slice position in the axial direction to perform repair welding. In this way, after one circle of repair welding of the entire grinding roller, the welding gun 31 returns to the first grinding roller slice position to perform the second layer of repair welding. The repair welding is repeated for multiple layers until the thickness requirement of the wear-resistant layer of the grinding roller 5 is met.

[0075] The application provides a grinding roller surface three-dimensional reconstruction and automatic repair welding system and a control method thereof, and has certain universality; the three-dimensional reconstruction method has wide application range, high reconstruction precision and is easy to implement, can be used for quickly and accurately obtaining three-dimensional point cloud information of a surface of an arbitrary rotating member, and realizes high-precision three-dimensional reconstruction of the surface of the arbitrary rotating member through coordinate conversion and point cloud splicing; the automatic repair welding method is suitable for grinding rollers of different specifications, can be quickly adjusted and optimized according to actual working conditions, and has wide industrial application prospects. The system provided by the application shoots two frames of images of a conical calibration block based on a line structured light camera, quickly calibrates a central axis of a rotating scanning system according to geometric relations, performs high-precision three-dimensional reconstruction on the surface of the grinding roller through the line structured light camera, and realizes accurate positioning and automatic repair welding of the wear defect of the grinding roller by using a controller to link and control a frequency converter, an encoder, a welding gun and other equipment, intelligently controls the entire grinding roller repair welding process, improves the repair welding quality, greatly improves the repair welding efficiency, reduces manual intervention and reduces labor intensity. The system provided by the application also has a surfacing function, can automatically perform multi-layer surfacing according to the thickness requirement of the wear-resistant layer, meets the surfacing requirement of the grinding roller, and further improves the service life of the grinding roller. The system provided by the application can realize three-dimensional reconstruction of the surface of the grinding roller through the line structured light camera, and can realize automatic repair welding of the grinding roller through the collaborative work of the controller and the frequency converter, the encoder, the welding gun and other equipment.

[0076] The above description is only a preferred embodiment of the application, and is not intended to limit the application in other forms. Any skilled person in the art can modify or change the above disclosed technical content into equivalent embodiments. However, any simple modification, equivalent change and modification made on the basis of the technical essence of the application to the above embodiments still falls within the protection scope of the application.

Claims

1. A system for three-dimensional reconstruction and automatic repair welding of a surface of a grinding roller, characterized in that it comprises: The platform (1) for supporting and rotating the grinding roller (5), the three-dimensional reconstruction assembly (2), the welding assembly (3) and the controller (4); The platform (1) comprises a rotating table (10), a motor (12) for driving the rotating table, an encoder (15) for measuring the rotating angular displacement, and a frequency converter (18) for adjusting the rotating speed of the motor; the three-dimensional reconstruction assembly (2) comprises a line structured light camera (21) for collecting the point cloud information of the surface of the grinding roller (5) and a conical calibration block (23); and the welding assembly (3) comprises a welding gun (31), a horizontal shaft stepping motor (33), a horizontal shaft screw (34), a vertical shaft stepping motor (35) and a vertical shaft screw (36). The rotating table (10) is driven by a middle shaft (11) connected with the output shaft of a speed reducer (13) through a gear (14), and the encoder (15) is connected with the output shaft of the speed reducer (13) through a shaft coupling (17); the motor (12) and the speed reducer (13) are fixedly arranged on the inner surface of the side of a box body; the encoder (15) and a PLC (16) are fixedly arranged on a fixed support extending from the inner surface of the box body; the frequency converter (18) is fixedly arranged on a base; and the end position of the welding gun (31) is moved in the horizontal direction by the horizontal shaft stepping motor (33) and the horizontal shaft screw (34) and in the vertical direction by the vertical shaft stepping motor (35) and the vertical shaft screw (36). The controller (4) is connected with the line structured light camera (21), the PLC (16), the frequency converter (18), the welding gun (31) and the horizontal shaft stepping motor (33) and the vertical shaft stepping motor (35); the functions of the controller (4) include running the surface three-dimensional reconstruction and automatic repair welding system of the grinding roller (5) and realizing the automatic repair welding function. The PLC (16) sends the rotating angular displacement information stored in the register to the controller (4) in real time through the Modbus protocol; the controller (4) sends instructions to the specified register of the frequency converter (18) through the Modbus protocol and changes the motor frequency of the frequency converter (18) to adjust the rotating speed of the rotating table; the controller (4) sends instructions to the welding gun (31) through the Modbus protocol to control the start and stop of welding and the adjustment of the welding parameters; and the controller (4) sends instructions to the motion control card, the single-chip microcomputer or the stepping motor driver through the Modbus protocol to make the horizontal shaft stepping motor (33) output pulses to drive the horizontal shaft screw (34) to move and make the vertical shaft stepping motor (35) output pulses to drive the vertical shaft screw (36) to move, thereby controlling the end position of the welding gun.

2. The system of claim 1, wherein the system further comprises a three-dimensional reconstruction device for reconstructing the surface of the grinding roller. The line structured light camera (21) of the three-dimensional reconstruction assembly (2) collects single-frame point cloud information of the surface of the rotating grinding roller (5) by being fixed and immobile and continuously collecting the single-frame point cloud information, and realizes the collection of the three-dimensional point cloud information of the surface of the grinding roller (5) in combination with the rotating angular displacement of the grinding roller (5).

3. The control method of the three-dimensional reconstruction and automatic repair welding system for the surface of the grinding roller, which is applied to the three-dimensional reconstruction and automatic repair welding system for the surface of the grinding roller in claim 1 or claim 2, characterized in that, The control method comprises the following steps: Step S1: calibrate the camera extrinsic parameter k of the line structured light camera (21) and the center axis parameter m of the rotary scanning system when the operation has not started, to obtain the transformation relationship matrix of the camera coordinate system and the world coordinate system in the mathematical model of the rotary scanning system; wherein k is the camera extrinsic parameter, indicating the transformation coefficient of the camera coordinate system and the world coordinate system; z 、 w ; Step S2: the grinding roller (5) rotates at a constant speed, the line structured light camera (21) continuously collects single-frame point clouds in the axial direction of the surface of the grinding roller (5), the encoder (15) and the PLC (16) acquire the angular displacement in real time, the controller (4) pre-processes each frame of point cloud, and performs point cloud splicing and three-dimensional reconstruction on multiple frames of point cloud according to the conversion relationship obtained in step S1 to obtain a three-dimensional reconstruction model of the surface of the grinding roller (5); Step S3: according to the three-dimensional point cloud information of the surface of the grinding roller (5) obtained in step S2, the grinding roller (5) is segmented in the axial direction, the segmented grinding roller (5) sheet is regarded as a cylinder, and the cylinder point cloud is reduced to a two-dimensional plane based on the dimension reduction theory to obtain two-dimensional polar coordinate point cloud; Step S4: analyzing the defect distribution position in the two-dimensional plane, and calculating the defect size based on the integral idea; Step S5: according to the defect size and distribution position obtained in step S4, the output speed is calculated, and the speed is inversely proportional to the defect depth; Step S6: according to the output speed calculated in step S5, the welding process of the welding gun (31) is controlled to realize targeted repair welding of the defects of the grinding roller (5); Step S7: after the targeted repair welding is completed, the surfacing of the grinding roller (5) is continued to increase the thickness of the wear-resistant layer.

4. The control method of a three-dimensional reconstruction and automatic repair welding system for the surface of a grinding roller according to claim 3, characterized in that, Step S1 includes: The center axis of the rotating scanning system is quickly calibrated based on the conical calibration block (23), and the calibration method is as follows: the conical calibration block (23) is fixed on the side wall of the rotating table (10), so that the structured light line projected by the line structured light camera (21) passes through the vertex of the cone, at this time the first frame of image is shot, then the rotating table (10) is rotated by an angle, the second frame of image is shot, the center axis parameters of the rotating scanning system are obtained according to the geometric relationship of the two frames of images, and the transformation matrix of the camera coordinate system and the world coordinate system in the mathematical model of the rotating scanning system is established; In the rapid calibration of the central axis of the rotating scanning system, the expression of the distance r of the vertex of the conical calibration block in the first frame of point cloud imaging to the Z-axis coordinate of the camera coordinate system m z includes the following content: w The expression of the distance r of the vertex of the conical calibration block to the rotating scanning central axis where k is the camera extrinsic parameter, representing the transformation coefficient between the camera coordinate system and the world coordinate system, a is the angle of the rotation stage, r C and p C are the projection lengths of the camera imaging in the Z-axis of the camera coordinate system for the first frame and the second frame, respectively, and r w is the distance between the vertex of the conical calibration block and the rotation scanning central axis.

5. The control method of a three-dimensional reconstruction and automatic repair welding system for the surface of a grinding roller according to claim 4, characterized in that, In step S2, the formula for converting two-dimensional coordinates to three-dimensional coordinates during point cloud stitching is: X = X c ×k, Y=[(Z c -m z )×k+r w ]×sinθ,Z=[(Z c -m z )×k+r w ]×cosθ; wherein (X c , Y c ) is a two-dimensional coordinate in the camera coordinate system, (X, Y, Z) is a three-dimensional coordinate in the world coordinate system, and the parameter θ represents the angle of rotation of the grinding roller counterclockwise about the central axis; sinθ represents the sine value of the angle of rotation of the grinding roller counterclockwise about the central axis; and cosθ represents the cosine value of the angle of rotation of the grinding roller counterclockwise about the central axis.

6. The control method of a three-dimensional reconstruction and automatic repair welding system for grinding roller surfaces according to claim 5, characterized in that, In step S3, the formula for reducing the cylinder point cloud to a two-dimensional plane based on the dimension reduction theory is: In the formula, (θ, R) is the polar coordinates of the point cloud after dimension reduction, θ is the same physical quantity as θ in step S2, representing the rotation angle displacement of the point cloud of the frame from the first frame point cloud, X0 and X1 are the upper and lower limit values of the X coordinate of the slice; (X i , Y i , Z i ) are the three-dimensional coordinates of a plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice, t is the number of the plurality of point clouds, and R represents the average value of the radii of the plurality of point clouds corresponding to the same angle θ within the upper and lower limit values of the X coordinate of the slice.

7. The control method of a three-dimensional reconstruction and automatic repair welding system for grinding roller surfaces according to claim 3, characterized in that, In the step S4, according to the start angle θ1 and the end angle θ2 of the defect, the R corresponding to all θ in the angle range is accumulated to obtain the defect area, and the defect area is calculated according to the following formula: i And the difference between the maximum fitting circle radius R max The absolute value is accumulated to obtain the defect area, and the calculation formula of the defect area is as follows: Wherein A is the defect area.

8. The control method of a three-dimensional reconstruction and automatic repair welding system for grinding roller surfaces according to claim 7, characterized in that, In step S5, the speed calculation formula is: In the formula, K and ε respectively represent two constants; wherein, the constant K represents the best corresponding relationship coefficient of the actual motor speed and the defect area; and the constant ε represents that when the grinding roller (5) has no defects, that is, A=0, the speed v has an upper limit value.

9. The control method of a three-dimensional reconstruction and automatic repair welding system for the surface of a grinding roller according to claim 3, characterized in that, In step S6, the linkage control scheme of the controller (4) for targeted repair welding is as follows: the controller (4) sends instructions to control the welding gun (31) to move to the grinding roller (5) sheet position corresponding to the two-dimensional plane in step S4, the frequency converter (18) adjusts the rotating table speed in real time according to the output speed result of step S5 and the real-time rotating angular displacement feedback by the encoder (15), and the grinding roller (5) sheet is repaired in a targeted manner; and the repair welding of other grinding roller (5) sheets is realized in turn, and finally the targeted repair welding of the defects on the surface of the entire grinding roller (5) is realized.

10. The control method of a three-dimensional reconstruction and automatic repair welding system for grinding roller surfaces according to claim 3, characterized in that, In the step S7, the controller (4) controls the welding gun (31) to start from the first slice position of the grinding roller (5) for repair welding, and after one circle of repair welding, the welding gun steps to the next slice position along the axial direction for repair welding. In this way, the entire grinding roller (5) is repaired and welded for one circle, and then the welding gun returns to the first slice position of the grinding roller (5) for the second layer of repair welding. The repair welding is repeated for multiple layers until the thickness requirement of the wear-resistant layer is met.

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