Multi-directional linkage synchronous stretching type leather stretching device

Abstract

This invention discloses a multi-directional linkage synchronous stretching leather stretching device, including a laying station, a stretching station, a gripping and hanging station, a disassembly and sorting station, and a stretching frame resetting station, and is also equipped with an Aobo robotic arm and a transport vehicle. The laying station includes a base with two pairs of oppositely arranged transmission device side plates on the base, forming a guide channel between each pair of side plates, and a conveyor belt running in the channel; the leather stretching mechanism is installed on the conveyor belt; the leather stretching mechanism includes a stretching frame and multiple radially retractable stretching plates distributed circumferentially, the leather is laid on the support surface composed of stretching plates, and multi-directional stretching is achieved by the synchronous outward expansion of the stretching plates; this invention can apply tensile force in multiple directions along the circumference of the leather, realize multi-directional asymmetric synchronous adjustment, effectively eliminate local wrinkles, balance the overall tension, and accurately control the edge position, thereby ensuring that leather with irregular shape or significant anisotropy achieves high flatness and dimensional stability after stretching.

Description

Technical Field

[0001] This invention belongs to the field of leather processing technology, specifically relating to a multi-directional linkage synchronous stretching leather stretching device. Background Technology

[0002] In leather processing, stretching is a crucial finishing step. Its purpose is to stretch and fix the leather, maintaining specific tension to ensure it dries smoothly and flattens, reducing shrinkage and wrinkling, improving appearance and dimensional stability, and laying the foundation for subsequent processing. Tanned and dyed leather fibers are prone to shrinkage and deformation; if stretching is not performed correctly, finished products are susceptible to quality defects, severely impacting added value and market competitiveness.

[0003] Existing leather stretching devices mostly employ unidirectional stretching or symmetrical bidirectional expansion structures, which cannot achieve multi-directional coordinated adjustment. When processing leather with irregular shapes or significant differences in extensibility in different directions, it is difficult to apply appropriate stretching forces simultaneously in multiple circumferential directions, resulting in problems such as local wrinkles, tension imbalance, or edge misalignment after stretching, which affects the quality of subsequent processing. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-directional linkage synchronous stretching leather stretching device that can apply stretching force in multiple directions along the circumference of the leather, realize multi-directional asymmetric synchronous adjustment, effectively eliminate local wrinkles, balance the overall tension and precisely control the edge position, thereby ensuring that irregularly shaped or significantly anisotropic leathers achieve high flatness and dimensional stability after stretching.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A multi-directional, synchronously linked, stretching leather stretching device includes a laying station, a stretching station, a gripping and hanging station, a disassembly and finishing station, and a stretching frame resetting station. The stretching station, gripping and hanging station, disassembly and finishing station, and stretching frame resetting station all have the same main frame as the laying station. Each of the laying station, gripping and hanging station, and disassembly and finishing station is equipped with an Aobo robotic arm for performing leather loading, hanging, and disassembly and finishing operations. A transport vehicle is also provided. The laying station includes a base with two pairs of opposing transmission device side plates, forming a guide channel between each pair of transmission device side plates, and a conveyor belt runs within the guide channel. A leather stretching mechanism is mounted on the conveyor belt, carrying the leather to be stretched. The leather stretching mechanism includes a stretching frame and several... The leather stretching mechanism consists of circumferentially distributed stretching plates, each capable of radial expansion and contraction relative to the stretching plate frame. The leather to be stretched is laid on the support surface formed by all the stretching plates and is stretched and stretched as the stretching plates expand outward. The leather stretching mechanism, carrying the leather, serves as the process carrier, completing the corresponding processes at each station in sequence: the leather is loaded and initially positioned at the laying station, transported to the stretching station for stretching and shaping, and then picked up and transferred to the drying chamber by an Aobo robotic arm at the gripping and hanging station. After drying, the transport vehicle transports the leather stretching mechanism carrying the dried leather to the disassembly and finishing station, where the Aobo robotic arm removes the finished leather from the leather stretching mechanism and places it on the transport vehicle for transport to the downstream process. Subsequently, the empty leather stretching mechanism is transported to the stretching plate frame reset station for reset and then returned to the laying station for the next cycle.

[0006] Furthermore, the stretching frame includes an outer stretching frame and an inner stretching frame nested therein, both coaxially and symmetrically arranged; a crank disc bracket is installed transversely inside the outer stretching frame, with both ends fixedly connected to the side walls of the outer stretching frame, and located at the center of the inner stretching frame; two crank discs are symmetrically arranged on the crank disc bracket near the outer stretching frame, and each crank disc is hinged with a stretching mechanism connecting rod matching the number of stretching plates; the two crank discs are connected by crank disc connecting rods; stretching layer tracks with guide grooves matching the number of stretching plates are evenly distributed between the outer and inner stretching frames, and stretching plate sliders are embedded in the guide grooves of the stretching layer tracks, wherein the upper end of each stretching plate slider is connected to the stretching plate, and the lower end is hinged to one end of the stretching mechanism connecting rod; the main frame of the stretching station is equipped with a motor lifting device, which is coaxially connected to one of the crank discs, thereby driving the leather stretching mechanism to stretch the leather to be stretched.

[0007] Furthermore, a stretching control mechanism for the leather stretching mechanism is provided below the crank disc bracket. This stretching control mechanism includes a spring slide, a ratchet, and a fixed base. The ratchet is keyed to the crank disc bracket and is coaxially fixed to one of the crank discs, allowing them to rotate synchronously. The spring slide is fixedly mounted to the crank disc bracket via the fixed base. A spring is fitted onto the spring slide, with one end connected to the fixed base and the other end connected to an unlocking slider. The unlocking slider is connected to the slider roller via a slider roller shaft. An unlocking device connecting rod is installed on the side of the unlocking slider near the crank disc bracket. Both ends of the unlocking device connecting rod are hinged to the unlocking slider and the pawl, respectively, with the pawl hinged to the crank disc. The motor lifting device includes a motor support mounted within the main frame of the stretching station. Two sets of internal motor supports are symmetrically mounted on the motor support, each set of internal motor supports is equipped with an electric push rod. A motor support plate is mounted on the top of the two sets of electric push rods and is fixedly connected to their output ends. A servo motor is mounted on the motor support plate via a motor bracket. The output end of the servo motor is connected to a rotary table. A stretching plate drive shaft connected to a crank disc transmission is mounted on the rotary table. The front end of the stretching plate drive shaft is sequentially provided with a cylindrical shaft section and a conical boss structure. When the leather stretching mechanism moves to the stretching station, the motor lifting device moves upward, driving the motor support plate vertically via the electric push rods. The cylindrical shaft of the stretching plate drive shaft is inserted into the center hole of the ratchet and crank disc to achieve coaxial positioning. The return spring is pre-compressed during assembly, and its length does not exceed the free length. The return spring continuously applies a stable rightward axial thrust to the unlocking slider, causing the pawl to tightly engage and lock into the tooth groove of the ratchet. The servo motor rotates forward, driving the stretching plate drive shaft to rotate, which in turn drives the ratchet and the coaxially connected crank disc to rotate. The pawl slides over the tooth tip along the direction of rotation on the ratchet tooth profile, achieving a one-way overrunning function. During the rotation of the crank disc, the stretching mechanism connecting rod converts the rotational motion into linear thrust, driving the stretching plate slider to make a radially outward linear translation along its corresponding stretching layer track. The servo motor stops outputting torque, and the elastic recoil force of the leather... When the crank disc and ratchet reverse, the pawl and the root of the ratchet teeth mechanically interfere, forming a one-way self-locking mechanism. The main frame of the stretching frame reset station is equipped with a motor lifting device. The structure of the motor lifting device is the same as that of the motor lifting device located in the stretching station, and the axial travel of the motor lifting device is greater than that of the motor lifting device in the stretching station. The stretched leather stretching mechanism is transferred to the stretching frame reset station. The motor lifting device of the stretching frame reset station moves upwards in the vertical direction. The conical boss structure on the stretching power shaft abuts upwards and laterally squeezes the slider roller, causing the unlocking slider to overcome the thrust of the reset spring and move radially backwards, thereby forcibly pulling the pawl away from the ratchet teeth.After the lock is released, the servo motor rotates in the reverse direction, driving the stretching plate power shaft to rotate. This causes the ratchet and its coaxially connected crank disc to rotate in the opposite direction, which in turn pulls the stretching mechanism connecting rod, causing the stretching plate slider to move radially inward in a linear retraction motion along the stretching plate layer track. Finally, all stretching plates synchronously retract to the center position, completing the full reset of the leather stretching mechanism.

[0008] Furthermore, the main frame of the stretching station is equipped with an actuator magnet picking and placing mechanism. This mechanism includes a truss-type robotic arm base, on which a camera bracket and a crossbeam are mounted. An industrial camera and a light source are mounted on the top of the camera bracket. A truss-type robotic arm capable of linear movement along the X, Y, and Z axes is mounted on the crossbeam. At the end of the truss-type robotic arm is a magnet picking and placing actuator drive motor, on which a magnet picking and placing actuator is mounted. An electromagnet storage box is installed below the crossbeam, containing de-energized electromagnets. The magnet picking and placing actuator is configured to automatically pick up the de-energized electromagnet from the electromagnet storage box based on the stretching point coordinates output by the stretching point identification and positioning algorithm, and precisely place it at the corresponding stretching point position on the leather surface to achieve fixed-point pressing and fixing of the leather.

[0009] Furthermore, a magnet recycling device is installed on one side of the main frame of the disassembly and sorting station. An electromagnet storage box conveying device is installed below the magnet recycling device. On both sides of the magnet recycling device are an Aobo robotic arm with a hook actuator at its end and an Aobo robotic arm with a suction cup end actuator at its end. The magnet recycling device includes a suspension rod and a magnet collecting chamber. The suspension rod is used to suspend the leather stretching mechanism, forming a power supply path when the leather stretching machine is attached to the suspension rod. The magnet collecting chamber is located below the suspension rod. The top of the magnet collecting chamber has an inlet for receiving de-energized electromagnets, and the bottom has a discharge outlet. The discharge outlet is connected to the electromagnet storage box conveying device via a feeding plate. The push rod is arranged on one side of the feeding plate, and its movement direction is consistent with the length direction of the feeding plate. It is used to push the de-energized electromagnets placed on the feeding plate into the electromagnet storage box along this direction. The electromagnet storage box conveying device is arranged around the stretching station and the disassembly and sorting station. It includes a circular conveying track laid on the ground. A branch conveying track is also set on one side of the circular conveying track, which is connected to it to form a replenishment bypass. The branch conveying track is adjacent to the discharge outlet of the magnet recycling device. Empty electromagnet storage boxes are transported to the area below the electromagnet discharge outlet of the magnet recycling device through the branch conveying track for filling. After the electromagnet storage box is full of de-energized electromagnets, it returns to the circular conveying track and is transported to the stretching station.

[0010] Furthermore, the electromagnet storage box is an integrated shell with an upper triangular shape and a lower rectangular shape, with a permanent magnet embedded in the apex of the triangle; a Hall sensor is installed upstream of the entrance of the branch conveyor track adjacent to the circular conveyor track; a sorting baffle is installed at the entrance of the branch conveyor track and is connected to the Hall sensor signal, configured such that: when an empty electromagnet storage box moves to the position of the Hall sensor in a forward orientation, in response to the trigger signal generated by the permanent magnet passing through the sensing area of ​​the Hall sensor, the empty electromagnet storage box is diverted and guided into the branch conveyor track; the branch conveyor track includes a left track and a right track arranged in parallel, forming a longitudinal gap extending along the conveying direction between the two tracks and adapted to the electromagnet storage box; a lifting rotary table is installed on the branch conveyor track corresponding to the position of the feeding plate. The lifting rotary table is located directly below the longitudinal gap of the branch conveyor track. Its initial position is lower than the top surface of the track. It includes a liftable platform and a rotary mechanism that rotates around a vertical axis. A pressure sensor is installed at the bottom of the liftable platform to determine whether the electromagnet storage box is full. The lifting rotary table is configured such that when the electromagnet storage box moves above the lifting rotary table along the branch conveyor track, the lifting rotary table rises and lifts the electromagnet storage box, causing it to detach from the track support. Subsequently, while the electromagnet storage box is in a suspended state, the recovered magnets are loaded into the electromagnet storage box via the feeding plate. After filling, the lifting rotary table rotates 180° to reorient the electromagnet storage box. After reorientation, the platform descends, and the filled and reoriented storage box is placed back onto the branch conveyor track for continued subsequent conveying.

[0011] Furthermore, the stretching point identification and positioning algorithm is specifically a stretching point selection method based on partitioned equidistant parallel lines, including the following steps: Step 1: Construct a model of the line of action of the force loading. The intersection of the extended lines of the head and tail endpoints and the limb endpoints in the idealized leather model is used as the morphological reference center to replace the traditional centroid positioning method. Based on this morphological reference center, the leather area is divided into multiple sub-regions, and the main stretching direction is set along the angle bisector of each sub-region. At the same time, auxiliary stretching directions are added in highly deformable and sensitive areas in the leather outline that have significant lateral extension, local outward convexity, or dramatic curvature changes, to construct a force loading action line model. Step 2: After acquiring the leather image, perform grayscale processing, Gaussian blur denoising, and binarization processing on the image in sequence. Then, perform morphological operations on the binarized image and finally extract the contour to remove noise and background interference and obtain a leather recognition image with smooth edges and completeness. Step 3: Use OpenCV's contour extraction function to obtain the single-pixel-wide outer contour of the leather, and divide the leather region into upper and lower halves based on its geometric center; construct 14 force loading lines on the contour image, and align the geometric center of the contour with the center of the force loading line model; determine the position of the basic stretching point by detecting the intersection of each force loading line with the contour. Step 4: Establish a zoning system in the upper and lower halves of the leather area. Detect the intersection of the parallel lines with the leather outline by arranging an array of equally spaced parallel lines, thereby supplementing auxiliary stretching points. Finally, integrate the basic and auxiliary stretching points to form a composite stretching point system with a reasonable layout throughout the entire area.

[0012] Furthermore, the location of the basic tension point mentioned in step 3 is determined through the following steps: (1) Determine the necessary stretching points The highest and lowest points of the leather outline are obtained vertically. A horizontal center line is drawn with the center between these two points, dividing the leather into upper and lower halves. Intersection point detection is performed on the skeletal lines of the leather outline. The closest intersection points to the horizontal center line are selected in the skeletal regions above and below the center line, respectively, to obtain the corresponding ridge nodes. Two ridge nodes are connected, and the line is extended towards the head and tail ends respectively until it intersects the outline, thus obtaining the leather's backline. The leftmost and rightmost extreme contour points are extracted from the upper and lower halves of the outline, respectively, and these extreme points are connected to the ridge nodes of the corresponding halves. Finally, the simplest skeleton under the ideal outline is constructed; then, the intersection of the horizontal midline and the spine line is defined as the center point of the leather morphology, and a coordinate system is established as the origin. In this coordinate system, the spine nodes are located at about one-third of the distance from the origin to the end points of the leather. Each spine node is connected to the extreme point of the limb ends of its respective half-region, and the direction of the connecting line is consistent with the natural growth direction of the leather fibers. Therefore, the spine line and the lines connecting the spine nodes to the extreme points of the limb ends constitute the necessary stretching directions in the leather spreading process; the intersections of these stretching directions with the leather outline are the six necessary stretching points. (2) Based on the morphological characteristics of the leather and the simplest skeleton under the ideal contour, the upper and lower halves of the leather are divided into three regions each, with the vertebral nodes of the upper and lower halves as vertices, and radially divided along the symmetrical axial edge of the spine line. Fourteen force loading lines are constructed on the contour image. Region 1 is bounded by two boundary lines that are symmetrical about the spine line and have a total angle of 45°, with the corresponding vertices of the vertebral nodes of the partition as vertices. Within each partition, two new rays are extended outward by rotating 60° from the two boundary rays of Region 1 as references. A total of four new rays are formed in the upper and lower partitions. The angled region enclosed by the upper and lower partitions together with the adjacent boundaries is Region 2, and the remaining region is Region 3. Based on the initial division of the three regions, a total of 8 extended rays are formed. Region 2 and Region 3 are divided into two equal parts, and finally 14 force loading lines are constructed on the contour image. (3) Detect the intersection of the leather profile and the line of force application to determine the basic tension point. The intersection points of the leather profile and the line of force application were detected using the nearest neighbor projection method, and the leather profile points were traversed. Calculate its normalized projection parameters along the direction of the force loading line. Using this projection parameter, each point is projected onto the parameter space of the force loading line: In the formula, As the starting point of the line of action of the force loading, The endpoint of the line of action of the force loading; for For candidate points within the valid interval, further calculate contour points. Its coordinates as an orthogonal projection point on the line of force application : Next, calculate the leather outline points. and projection point Euclidean distance: The algorithm traverses 14 lines of force application to obtain 14 basic tension points.

[0013] Furthermore, the auxiliary stretching point mentioned in step 4 is determined through the following steps: First, using the vertebral node as a reference, based on the intersection relationship between 14 force loading lines and the leather contour, a total of 10 triangular regions and 4 trapezoidal regions are divided. A differentiated baseline generation strategy is adopted for the two types of regions: the baseline system of the triangular regions is constructed by the angle bisectors of their adjacent boundaries, while the force loading lines inside the trapezoidal regions are directly used as the baseline. Then, in each region, equidistant parallel line clusters with a spacing of 10mm are symmetrically generated on both sides of the baseline, and the clip_line_segment() function is used to trim the line segments, retaining the line segments that are completely within the region, and calculating the intersection points of some cross-boundary line segments for precise cutting. The algorithm iterates through all parallel lines and the leather contour image, using projection to detect intersections and obtain dense reference points on the leather contour. Finally, based on the obtained dense reference points, auxiliary stretching points are selected using a cumulative distance thresholding method: within each partition, starting from the base stretching point... Connect the reference points sequentially to the left / right to form an ordered sequence from the reference starting point to each intersection point. Construct a path chain from the starting point to the end point, and calculate the cumulative distance of each point on the path relative to the starting point. : Total length of path chain This can be viewed as an approximate length of the leather outline within the region; a filtering threshold can be set. Starting from the starting point, accumulate the segmented distances. When the accumulated value... When, select the next intersection point. As an auxiliary stretching point, the tolerance It is 5mm.

[0014] Furthermore, a roller drive shaft is provided between the two pairs of transmission device side plates, with both ends of the roller drive shaft respectively mounted on the transmission device side plates, and a conveyor belt wound around the roller drive shaft; the leather stretching mechanism is set on the conveyor belt, carried by the conveyor belt and running with it, and the leather to be stretched is carried on the leather stretching mechanism; on both sides of the spreading station, there are Aobo robotic arms with leather operation end actuators at their ends, used to spread the leather to be stretched on the leather stretching mechanism; a guide roller side plate is fixedly installed on the outer side of each transmission device side plate, and a set of guide rollers is installed on the guide roller side plate, each set containing sixteen guide rollers, the outer circumference of the guide rollers... The surface rolls in contact with the lateral guide surface of the leather stretching mechanism; a transmission motor is mounted on the base via a motor bracket, the output shaft of the transmission motor is connected to a large pulley, a small pulley is mounted on the roller drive shaft, and is connected to the large pulley via a transmission belt; a stretching frame locking mechanism is also provided between the motor bracket and the motor support plate, the stretching frame locking mechanism includes a stretching frame locking mechanism bracket fixed at the upper edge of the motor bracket, a stretching frame locking claw is hinged to the stretching frame locking mechanism bracket, and is hinged to one end of the stretching frame locking push rod via a locking claw connecting rod; the other end of the stretching frame locking push rod is connected to the stretching frame locking push rod bracket fixed on the motor support plate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention automates the entire process of leather stretching, from loading, stretching, gripping and hanging, disassembly and finishing, to resetting the stretching frame. A leather stretching mechanism, carrying the leather, serves as the process carrier, performing corresponding steps at each station. This achieves fully automated operation of the leather, from loading, multi-directional synchronous stretching, automatic gripping, hanging and drying, leather unloading and finishing, to automatic resetting of the stretching frame. The stretching mechanism features stretching plates distributed circumferentially and capable of synchronous or on-demand radial expansion and contraction, ensuring uniform tension from multiple directions on the leather during stretching, effectively preventing localized overstretching or loosening. The radially adjustable stretching plate structure automatically adjusts the size and shape of the support surface according to the actual contour of the leather, eliminating the need for changing special clamps. It is suitable for various specifications and irregularly shaped leathers, enhancing the equipment's versatility and flexibility. Compared to traditional edge-clamping stretching methods, this structure disperses stress through surface support and flexible expansion, preventing tearing or indentation at the clamping points, making it particularly suitable for the fine processing of high-grade or thin leathers.

[0016] Furthermore, the leather stretching mechanism of this invention adopts a double-crank disc synchronous transmission structure. The crank disc connecting rod enables coordinated movement on both sides, and the stretching mechanism connecting rod converts the rotational motion into radial linear motion of the stretching plate slider, thereby driving the circumferentially distributed stretching plates to expand synchronously, uniformly and multi-directionally stretching the leather. Simultaneously, a stretching control and locking mechanism composed of a ratchet and pawl is provided. After the servo motor stops, mechanical self-locking prevents the leather from retracting, ensuring stable stretching tension. At the reset position, the motor lifting device drives the stretching plate power shaft with a conical boss upwards, and the lateral compression unlocking slider forcibly separates the pawl and ratchet, releasing the locked state and achieving automatic reset of the stretching plate frame. This structure effectively achieves high-precision synchronous stretching, reliable tension maintenance, and efficient automatic reset in the leather stretching process, significantly improving stretching quality, equipment automation level, and work cycle efficiency.

[0017] Furthermore, this invention features a gantry-type robotic arm with three-axis (X / Y / Z) movement capabilities at the stretching station, combined with a stretching point recognition and positioning algorithm based on equidistant parallel lines in partitions. This algorithm intelligently identifies the leather edge contour and automatically selects the optimal stretching point, achieving precise clamping and multi-point coordinated stretching of the leather. Simultaneously, a magnet recycling device and a surrounding electromagnet storage box conveying system are installed at the disassembly and finishing station. This system includes a circular conveying track and branch conveying tracks with Hall sensor-triggered diversion, automatically identifying the posture and position of empty electromagnet storage boxes and guiding them into a replenishment bypass for cyclic replenishment. This integrated structure and intelligent algorithm work synergistically to not only improve the accuracy, uniformity, and adaptability of leather stretching but also achieve fully automated flow, recycling, and replenishment of the actuators (electromagnets), significantly reducing manual intervention and improving the system's continuous operation capability and overall automation efficiency.

[0018] Furthermore, compared to traditional centroid localization methods that are easily affected by irregular features such as long and thin heads and necks and short and thick tails in leather, the stretching point recognition and localization algorithm proposed in this invention accurately obtains the external contour of the leather by constructing a standardized force loading action line model and combining image preprocessing (grayscale conversion, Gaussian blurring, binarization, and morphological operations) and contour extraction techniques. Using the intersection points of the limbs, which are more consistent with biological anatomy, as the morphological reference center, and aligning this center with the contour, 14 fixed action lines and an array of equally spaced parallel lines are arranged in the upper and lower halves of the area, respectively. The intersection points are automatically detected to generate basic and auxiliary stretching points, forming a globally optimized composite stretching point system. This method eliminates the need to rebuild personalized models for each piece of leather in real time, significantly reducing computational complexity and time consumption. Simultaneously, the feature point prediction algorithm quickly locks key stretching positions, avoiding manual marking bias. The determined stretching direction can maximally conform to the local fiber direction, reducing the angle and effectively suppressing local wrinkles while ensuring a high leather yield and meeting overall deformation constraints. The overall solution combines high precision, high efficiency, and strong versatility, and can be adapted to leathers of different specifications and textures, ensuring uniform stretching force and significantly improving the accuracy of automated processing, the quality of finished products, and the feasibility of industrial implementation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the unfolding workstation structure of the present invention; Figure 3 This is a schematic diagram of the rear structure of the leather stretching mechanism of the present invention; Figure 4 This is a schematic diagram of the connection structure between the stretching control locking mechanism and the crank disc bracket of the leather stretching mechanism of the present invention. Figure 5 This is a schematic diagram of the stretching control and locking mechanism of the stretching mechanism of the present invention; Figure 6 This is a schematic diagram of the stretching station structure of the present invention; Figure 7 This is a schematic diagram of the connection structure of the motor lifting device of the present invention; Figure 8 This is a schematic diagram of the tensioning frame locking mechanism of the present invention; Figure 9 This is a schematic diagram of the magnet picking and placing mechanism of the actuator of the present invention; Figure 10 This is a schematic diagram of the gripping and suspension station structure of the present invention; Figure 11 This is a schematic diagram of the disassembly and finishing station structure of the present invention; Figure 12 This is a schematic diagram of the conveyor belt structure of the disassembly and sorting station of the present invention; Figure 13This is a schematic diagram of the tensioning frame resetting station structure; Figure 14 This is a structural schematic diagram of the force loading action line model; Figure 15 A diagram showing the essential stretching points for leather stretching; Figure 16 A schematic diagram of the leather stretching zones; Figure 17 A schematic diagram showing the location of the stretching points on the base of the leather stretching system; Figure 18 Generate a schematic diagram of the leather contour reference points based on parallel line projection; Figure 19 This is a schematic diagram showing the locations of all stretching points on a leather stretcher.

[0020] In the diagram: 1. Laying station; 2. Stretching station; 3. Grabbing and hanging station; 4. Disassembly and sorting station; 5. Stretching frame resetting station; 6. Aobo robotic arm; 7. Transport vehicle; 101. Base; 102. Transmission device side plate; 103. Conveyor belt; 104. Guide roller; 105. Leather stretching mechanism; 105-1. Outer frame of stretching layer; 105-2. Stretching layer track; 105-3. Stretching plate; 105-4. Stretching plate slider; 105-5. Stretching mechanism connecting rod; 105-6. Crank disc; 105-7. Inner frame of stretching layer; 105-8. Crank disc connecting rod; 105 -9. Crank disc support; 105-10. Spring slide bar; 105-11. Spring; 105-12. Unlocking slider; 105-13. Pawl; 105-14. Ratchet; 105-15. Sliding roller; 105-16. Sliding roller shaft; 105-17. Unlocking device linkage; 106. Leather; 107. Guide roller side plate; 108. Large pulley; 109. Small pulley; 1010. Drive belt; 1011. Motor support; 1012. Transmission motor; 1013. Roller drive shaft; 1014. Leather operation end effector; 201. Truss-type robotic arm base 202. Camera bracket; 203. Crossbeam; 204. Truss-type robotic arm; 205. Industrial camera; 206. Light source; 207. Electromagnet storage box; 208. Power-off electromagnet; 209. Motor lifting device; 209-1. Motor bracket; 209-2. Motor inner bracket; 209-3. Electric push rod; 209-4. Tensioner frame locking mechanism; 209-4-1. Tensioner frame locking claw; 209-4-2. Locking claw connecting rod; 209-4-3. Tensioner frame locking mechanism bracket; 209-4-4. Tensioner frame locking push rod; 209-4-5. Tensioner frame locking push rod. 209-5, Motor support plate; 209-6, Motor bracket; 209-7, Servo motor; 209-8, Rotary table; 209-9, Tensioner drive shaft; 2010, Magnet pick-and-place actuator drive motor; 2011, Magnet pick-and-place actuator; 301, Hook actuator; 401, Magnet recycling device; 402, Suction cup end effector; 403, Electromagnetic storage box conveyor device; 403-1, Circular conveyor track; 403-2, Branch conveyor track; 403-3, Sorting baffle; 403-4, Lifting rotary table; 404, Feeding plate; 405, Push rod. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1As shown in the figure, the multi-directional linkage synchronous stretching leather stretching device described in this embodiment includes a spreading station 1, a stretching station 2, a gripping and hanging station 3, a disassembly and sorting station 4, and a stretching frame resetting station 5. The spreading station 1, the gripping and hanging station 3, and the disassembly and sorting station 4 are all equipped with Aobo robotic arms 6 for performing leather loading, hanging, disassembly and sorting operations; in addition, a transport vehicle 7 is also provided.

[0023] The stretching station 2, gripping and hanging station 3, disassembly and sorting station 4, and stretching frame resetting station 5 all have the same main frame as the spreading station 1. The leather stretching mechanism 105, which carries the leather 106, serves as the process carrier and completes the corresponding processes at each station in sequence: the leather is loaded and initially positioned at the spreading station 1; then it enters the stretching station 2 to stretch and shape the leather; at the gripping and hanging station 3, the Aobo robotic arm 6 grips and transfers the leather to the drying chamber; after drying, the transport vehicle 7 transports the leather stretching mechanism 105 carrying the dried leather to the disassembly and sorting station 4, where the Aobo robotic arm 6 removes the finished leather from the leather stretching mechanism 105 and places it on the transport vehicle 7 to the downstream process; subsequently, the empty leather stretching mechanism 105 is transported to the stretching frame resetting station 5 for resetting and then returns to the spreading station 1 for the next cycle.

[0024] like Figure 1 , Figure 2 As shown, the spreading station 1 includes a base 101, on which two pairs of opposing transmission device side plates 102 are provided. A guide channel is formed between each pair of transmission device side plates 102, and a conveyor belt 103 runs within the guide channel, with its lateral position constrained by the transmission device side plates 102. A roller drive shaft 1013 is provided between the two pairs of transmission device side plates 102, with both ends of the roller drive shaft 1013 respectively mounted on the transmission device side plates 102. The conveyor belt 103 is wound around the roller drive shaft 1013. A leather spreading mechanism 105 is disposed on the conveyor belt 103, carried by the conveyor belt 103 and running with it. The leather 106 to be spread is carried on the leather spreading mechanism 105.

[0025] To prevent the leather stretching mechanism 105 from shifting or falling during transport, a guide roller side plate 107 is fixedly installed on the outer side of each transmission device side plate 102, and a set of guide rollers 104 are installed on the guide roller side plate 107. Each set contains sixteen guide rollers 104. The outer circumferential surface of the guide rollers 104 rolls in contact with the lateral guide surface of the leather stretching mechanism 105, thereby constraining the leather stretching mechanism 105 to run stably along a preset track. On both sides of the spreading station 1, Aobo robotic arms 6 with leather operation end actuators 1014 at their ends are respectively installed to spread the leather 106 to be stretched onto the leather stretching mechanism 105.

[0026] A transmission motor 1012 is mounted on the base 101 via a motor bracket 1011. The output shaft of the transmission motor 1012 is connected to a large pulley 108. A small pulley 109 is mounted on a roller drive shaft 1013 and is connected to the large pulley 108 via a transmission belt 1010. This is used to drive the roller drive shaft 1013 and the transmission belt 103 to rotate synchronously under the drive of the large pulley 108, thereby conveying the leather stretching mechanism 105, which carries the leather 106 to be stretched, to the stretching station 2.

[0027] like Figure 2 , Figure 3 As shown, the leather stretching mechanism 105 includes a stretching frame and a plurality of circumferentially distributed stretching plates 105-3 disposed on the stretching frame. Each stretching plate 105-3 can extend and retract radially relative to the stretching frame. The leather 106 to be stretched is laid on the support surface formed by all the stretching plates 105-3 and is stretched and stretched as the stretching plates 105-3 extend outward.

[0028] The tensioning plate frame includes an outer tensioning plate frame 105-1 and an inner tensioning plate frame 105-7 nested within it, both coaxially and symmetrically arranged. A crank disc bracket 105-9 is installed transversely inside the outer tensioning plate frame 105-1, with both ends fixedly connected to the side walls of the outer tensioning plate frame 105-1, and located at the center of the inner tensioning plate frame 105-7. Two crank discs 105-6 are symmetrically arranged on the crank disc bracket 105-9 near the outer tensioning plate frame 105-1, and the crank discs 105-6 are located between the inner tensioning plate frame 105-7 and the crank disc bracket 105-9. Each crank disc 105-6 is hinged with a tensioning mechanism connecting rod 105-5, matching the number of tensioning plates 105-3. The two crank discs 105-6 are connected by crank disc connecting rods 105-8 to achieve synchronous transmission.

[0029] Between the outer frame 105-1 and the inner frame 105-7 of the tensioning layer, tensioning layer tracks 105-2 with guide grooves are evenly distributed, matching the number of tensioning plates 105-3. Tensioning plate sliders 105-4 are embedded in the guide grooves of the tensioning layer tracks 105-2. The upper end of each tensioning plate slider 105-4 is connected to the tensioning plate 105-3, and the lower end is hinged to one end of the tensioning mechanism connecting rod 105-5.

[0030] like Figure 3 , Figure 4 , Figure 5As shown, a stretching control and locking mechanism for a leather stretching mechanism 105 is provided below the crank disc bracket 105-9. The stretching control and locking mechanism includes a spring slide rod 105-10, a ratchet 105-14, and a fixed base. The ratchet 105-14 is connected to the crank disc bracket 105-9 by a key. The ratchet 105-14 is coaxially fixed with one of the crank discs 105-6, and the two can rotate synchronously. The spring slide rod 105-10 is fixedly installed on the crank disc bracket 105-9 by the fixed base. A spring 105-11 is fitted on the spring slide rod 105-10. One end of the spring 105-11 is connected to the fixed base, and the other end is connected to an unlocking slider 105-12. The unlocking slider 105-12 is connected to the slider roller 105-15 through the slider roller shaft 105-16. An unlocking device connecting rod 105-17 is installed on the side of the unlocking slider 105-12 near the crank disc bracket 105-9. The two ends of the unlocking device connecting rod 105-17 are hinged to the unlocking slider 105-12 and the pawl 105-13, respectively. The pawl 105-13 is hinged to the crank disc bracket 105-9 and forms a meshing engagement with the ratchet 105-14.

[0031] like Figure 1 , Figure 6 , Figure 7As shown, the main frame of the stretching station 2 is equipped with a motor lifting device 209. The motor lifting device 209 is coaxially connected to a ratchet 105-14 and one of the crank discs 105-6, thereby driving the leather stretching mechanism 105 to stretch the leather 106 to be stretched. The motor lifting device 209 includes a motor bracket 209-1 mounted inside the main frame of the stretching station 2. The motor bracket 209-1 has a rectangular frame structure. Two sets of motor inner brackets 209-2 are symmetrically installed on the motor bracket 209-1. Each set of motor inner brackets 209-2 is equipped with an electric push rod 209-3. A motor support plate 209-5 is installed at the top of the two sets of electric push rods 209-3 and is fixedly connected to the output ends of both. When the electric push rods 209-3 extend and retract synchronously, they drive the motor support plate 209-5 to rise and fall in the vertical direction. A servo motor 209-7 is mounted on the motor support plate 209-5 via a motor bracket 209-6. The output end of the servo motor 209-7 is connected to a rotary table 209-8. A stretching power shaft 209-9, which is connected to the crank disc 105-6, is mounted on the rotary table 209-8. The front end of the stretching power shaft 209-9 is provided with a cylindrical shaft section and a conical boss structure in sequence. When the leather stretching mechanism 105 runs to the stretching station 2, the motor lifting device 209 moves upward, which is achieved by the electric push rod 2. 09-3 drives the motor support plate 209-5 to rise vertically. The cylindrical shaft section of the stretching plate drive shaft 209-9 passes through the central hole of the ratchet 105-14 and the crank disc 105-6, achieving coaxial positioning. During the leather stretching process, the tapered boss structure of the stretching plate drive shaft 209-9 remains in non-contact with the slider roller 105-15, thus preventing the slider roller 105-15 from being pushed to the left and accidentally triggering the unlocking action of the stretching frame locking mechanism, ensuring that the leather 106 can be fully stretched. The return spring 105-11 is fitted onto the guide rod 105-10, with one end abutting against the fixed base and the other end acting on the unlocking slider 105-12. The return spring 105-11 is pre-compressed during assembly to ensure that it is always under pressure throughout the working process, and its length does not exceed the free length, thus avoiding shaking, loosening, or free travel due to spring slack. As a result, the return spring 105-11 continuously applies a stable rightward axial thrust to the unlocking slider 105-12, which causes the pawl 105-13 installed at the front end of the unlocking slider 105-12 to fit tightly into the tooth groove of the ratchet 105-14.

[0032] Servo motor 209-7 rotates in the forward direction, driving the tensioning plate power shaft 209-9 to rotate, which in turn drives ratchet 105-14 and the crank disc 105-6 coaxially connected to it to rotate. Pad 105-13 slides over the tooth tip of ratchet 105-14 in the direction of rotation, achieving a unidirectional overtaking function. Since the two symmetrically distributed crank discs 105-6 are hinged together by crank disc connecting rod 105-8, synchronous linkage of the two transmission mechanisms is achieved. During the rotation of crank disc 105-6, the tensioning mechanism connecting rod 105-5 hinged to it converts the rotational motion into linear thrust, driving the tensioning plate slider 105-4 connected to it to make a radially outward linear translation along its corresponding tensioning plate layer track 105-2. Because the stretching plate slider 105-4 is fixedly connected to the outer stretching plate 105-3, the synchronous outward expansion of each set of stretching plate sliders 105-4 ultimately drives the radially arranged stretching plates 105-3 to move outward together, achieving uniform stretching of the leather 106 to be stretched. Once the servo motor 209-7 stops outputting torque, when the elastic recoil force of the leather attempts to reverse the crank disc 105-6 and ratchet 105-14, the pawl 105-13 and the root of the ratchet 105-14 mechanically interfere, forming a one-way self-locking mechanism. This anti-reverse mechanism physically locks the position of the stretching plate 105-3 in real time, ensuring that the leather remains taut under the set tension throughout the processing.

[0033] When the electric push rod 209-3 in the motor lifting device 209 retracts to its initial position, the stretching plate power shaft 209-9 moves axially downward, causing its cylindrical shaft section to completely disengage from the central hole of the ratchet 105-14, thereby severing the power transmission and engagement relationship with the crank disc 105-6 and the ratchet 105-14. Throughout the entire process of the stretching plate power shaft 209-9 retracting axially downward, its conical boss structure does not contact the roller 105-15 in the stretching unlocking mechanism, thus preventing the unlocking action of the stretching unlocking mechanism from being triggered. Since the power source is completely decoupled, and the self-locking mechanism formed by the ratchet 105-14 and the pawl 105-13 remains effectively engaged, the tensile potential energy generated by the stretching of the leather 106 is reliably locked inside the frame and cannot be released. Subsequently, the leather stretching mechanism 105, along with the tensioned leather 106, is transferred to the gripping and suspension station 3.

[0034] like Figure 6 , Figure 7 , Figure 8As shown, a tensioning frame locking mechanism 209-4 is also provided between the motor bracket 209-1 and the motor support plate 209-5. The tensioning frame locking mechanism 209-4 includes a tensioning frame locking mechanism bracket 209-4-3 fixed at the upper edge of the motor bracket 209-1. The tensioning frame locking claw 209-4-1 is hinged to the tensioning frame locking mechanism bracket 209-4-3 and is hinged to one end of the tensioning frame locking push rod 209-4-4 via the locking claw connecting rod 209-4-2. The other end of the tensioning frame locking push rod 209-4-4 is connected to the tensioning frame locking push rod bracket 209-4-5 fixed on the motor support plate 209-5.

[0035] like Figure 1 , Figure 6 , Figure 9 As shown, the main frame of the stretching station 2 is equipped with an actuator magnet picking and placing mechanism. The actuator magnet picking and placing mechanism includes a truss-type robotic arm base 201, on which a camera bracket 202 and a crossbeam 203 are mounted. An industrial camera 205 and a light source 206 are mounted on the top of the camera bracket 202. After the leather stretching mechanism 105 is fixed, the light source 206 provides uniform illumination, and the industrial camera 205 captures images of the leather 106 to be stretched in real time. A gantry-type robotic arm 204 capable of linear movement along the X, Y, and Z axes is mounted on the crossbeam 203. The gantry-type robotic arm 204 is configured to perform clamping and stretching operations based on the stretching point identification and positioning algorithm. A magnet pick-and-place actuator drive motor 2010 is provided at the end of the gantry-type robotic arm 204. A magnet pick-and-place actuator 2011 is mounted on the magnet pick-and-place actuator drive motor 2010. An electromagnet storage box 207 is installed below the crossbeam 203, and the electromagnet storage box 207 contains a de-energized electromagnet 208. According to the coordinate data of the selected stretching point, the gantry robotic arm 204 drives the magnet pick-and-place actuator 2011 to move to the position of the electromagnet storage box 207, picks up the de-energized electromagnet 208 from it, and deploys the de-energized electromagnet 208 to press the leather 106 to be stretched.

[0036] like Figure 10 As shown, an Aobo robotic arm 6 with a hook actuator 301 at its end is provided on the side and rear of the gripping and suspension station 3. This arm is used to grip the leather stretching mechanism 105 from the conveyor belt of the gripping and suspension station 3 and place it on the transport vehicle 7. The transport vehicle 7 is configured to send the leather stretching mechanism 105 to the drying chamber and, after drying, transport the leather stretching mechanism 105 carrying the stretched leather 106 to the disassembly and finishing station 4.

[0037] like Figure 11As shown, a magnet recycling device 401 is installed on one side of the main frame of the disassembly and sorting station 4, and an electromagnet storage box conveying device 403 is installed below the magnet recycling device 401. On both sides of the magnet recycling device 401 are respectively an Aobo robotic arm 6 with a hook actuator 301 at its end and an Aobo robotic arm 6 with a suction cup end actuator 402 at its end. The magnet recycling device 401 includes a suspension rod and a magnet collecting cavity. The suspension rod is used to suspend the leather stretching mechanism 105. When the leather stretching mechanism 105 is attached to the suspension rod, a power supply path is formed. The magnet collecting cavity is located below the suspension rod. The top of the magnet collecting cavity has an inlet for receiving the de-energized electromagnet 208, and the bottom has a discharge outlet. The discharge outlet is connected to the electromagnet storage box conveying device 403 via a feeding plate 404, for conveying the magnets to the electromagnet storage box conveying device 403. The push rod 405 is arranged on one side of the feeding plate 404, and its movement direction is consistent with the length direction of the feeding plate 404. It is used to push the de-energized electromagnet 208 placed on the feeding plate 404 into the electromagnet storage box 207 along this direction.

[0038] like Figure 12 As shown, the electromagnet storage box conveying device 403 includes a circular conveying track 403-1 laid on the ground. This circular conveying track is arranged around the stretching station 2 and the disassembly and sorting station 4 for the cyclical conveying of the electromagnet storage boxes 207. A branch conveying track 403-2 is also provided on one side of the circular conveying track 403-1, forming a replenishment bypass; and the branch conveying track 403-2 is adjacent to the discharge outlet of the magnet recycling device 401. Empty electromagnet storage boxes 207 are conveyed via the branch conveying track 403-2 to the area below the electromagnet discharge outlet of the magnet recycling device 401 for filling. After the electromagnet storage box 207 is filled with de-energized electromagnets 208, it returns to the circular conveying track 403-1 and is conveyed to the stretching station 2.

[0039] The electromagnet storage box 207 is an integrated shell with an upper triangle and a lower rectangle, and a permanent magnet is embedded in the apex of the triangle. A Hall sensor is provided upstream of the entrance of the branch conveyor track 403-2 near the circular conveyor track 403-1. A sorting baffle 403-3 is provided at the entrance of the branch conveyor track 403-2 and is connected to the Hall sensor signal. It is configured such that when the empty electromagnet storage box 207 runs in a positive posture to the position of the Hall sensor, in response to the trigger signal generated by the permanent magnet passing through the sensing area of ​​the Hall sensor, the empty electromagnet storage box 207 is diverted into the branch conveyor track 403-2.

[0040] The branch conveyor track 403-2 includes a left track and a right track arranged in parallel, forming a longitudinal gap extending along the conveying direction between the two tracks and adapting to the electromagnet storage box 207. A lifting rotary table 403-4 is provided on the branch conveyor track 403-2 at a position corresponding to the feeding plate 404. The lifting rotary table 403-4 is located directly below the longitudinal gap of the branch conveyor track 403-2, and its initial position is lower than the top surface of the track. It includes a liftable table surface and a rotary mechanism that rotates around a vertical axis. A pressure sensor is installed at the bottom of the liftable table surface to determine whether the electromagnet storage box 207 is full. The lifting rotary table 403-4 is configured such that when the electromagnet storage box 207 moves along the branch conveyor track 403-2 to the top of the lifting rotary table 403-4, the lifting rotary table 403-4 rises to lift the electromagnet storage box 207, causing it to detach from the track support; subsequently, while the electromagnet storage box 207 is in a suspended state, the recovered magnet is loaded into the electromagnet storage box 207 via the feeding plate 404; after loading is completed, the lifting rotary table 403-4 rotates 180° to reorient the electromagnet storage box 207; after reorientation is completed, the table descends, and the loaded and reoriented storage box is placed back onto the branch conveyor track 403-2 for continued subsequent conveying.

[0041] The Aobo robotic arm 6, equipped with a hook actuator 301 at its end, suspends the leather stretching mechanism 105 on the magnet recovery device 401. The magnet recovery device 401 and the leather stretching mechanism 105 form a power supply path, causing the de-energized electromagnets 208 fixed to the leather stretching mechanism 105 to lose their magnetism and fall into the magnet recovery device 401 under gravity. Once all the de-energized electromagnets 208 have detached, the Aobo robotic arm 6, equipped with a suction cup-type end effector 402 at its end, disassembles the stretched leather 106 and places it on a transport vehicle 7 for transport to the downstream process. Subsequently, the Aobo robotic arm 6, equipped with the hook actuator 301 at its end, places the empty and stretched leather stretching mechanism 105 on the conveyor belt of the disassembly and sorting station 4, transporting it to the stretching frame reset station 5. Simultaneously, the detached de-energized electromagnets 208 are transported by the magnet recovery device 401 and the electromagnet storage box conveyor 403 to the vicinity of the spreading station 1. The Aobo robotic arms 6 on both sides of the spreading station 1 control the leather operation end effector 1014 to remove the empty electromagnet storage box 207 under the crossbeam 203 on the stretching station 2, place it on the electromagnet storage box conveying device 403, and install the electromagnet storage box 207 filled with de-energized electromagnets 208 on the crossbeam 203.

[0042] like Figure 1 , Figure 13As shown, the main frame of the stretching frame reset station 5 is equipped with a motor lifting device, the structure of which is the same as that in the stretching station 2. The leather stretching mechanism 105 in the stretched state is transferred to the stretching frame reset station 5. The motor lifting device of the stretching frame reset station 5 moves upward in the vertical direction, and its axial stroke is greater than that in the stretching station 2. At this time, the conical boss structure on the stretching power shaft body abuts upward and laterally squeezes the slider roller 105-15. This lateral thrust forces the unlocking slider 105-12 to overcome the thrust of the reset spring 105-11 and move radially backward, thereby forcibly pulling the pawl 105-13 out of the tooth groove of the ratchet 105-14. At this point, the one-way anti-reverse mechanism of the ratchet and pawl fails, and the stretching lock state is completely released.

[0043] After the lock is released, the servo motor 209-7 rotates in the reverse direction, driving the stretching plate power shaft 209-9 to rotate. This causes the ratchet 105-14 and the crank disc 105-6, which is coaxially connected to it, to rotate in the opposite direction. This, in turn, pulls the stretching mechanism connecting rod 105-5, causing the stretching plate slider 105-4 to perform a radially inward linear retraction along the stretching plate layer track 105-2. Because the stretching plate slider 105-4 is fixedly connected to the stretching plate 105-3, it ultimately drives all the stretching plates 105-3 to synchronously retract towards the center position, completing the full reset of the leather stretching mechanism 105. The reset leather stretching mechanism 105 is then transported to the spreading station 1 for the next work cycle.

[0044] The stretching point identification and positioning algorithm, specifically a stretching point selection method based on partitioned equidistant parallel lines, includes the following steps: Step 1: Construct a model of the line of action of the force loading. The intersection of the extended lines from the head and tail endpoints and the limb endpoints in the idealized leather model is used as the morphological reference center, replacing the traditional centroid positioning method. Based on this morphological reference center, the leather area is divided into multiple sub-regions, and the main stretching direction is set along the angle bisectors of each sub-region. Simultaneously, auxiliary stretching directions are added to highly deformation-sensitive areas in the leather contour that exhibit significant lateral extension, local outward convexity, or drastic curvature changes, thus constructing a force loading action line model, such as... Figure 14 As shown.

[0045] Step 2: After acquiring the leather image, the image is sequentially processed by grayscale conversion, Gaussian blur denoising, and binarization. Then, morphological operations are performed on the binarized image, and finally, contour extraction is performed to remove noise and background interference, thereby obtaining a smooth and complete leather recognition image. During binarization, the threshold T is set to 150. All pixels in the original image with a value greater than or equal to 150 are set to 0 (black), while all pixels with a value less than 150 are set to 255 (white). The final result is: the background turns black, the leather area turns white, and the intermediate grayscale areas are effectively removed, thus achieving a clear distinction between the leather and the background.

[0046] Step 3: Use OpenCV's contour extraction function to obtain the single-pixel-wide outer contour of the leather. Divide the leather region into upper and lower halves based on its geometric center. Construct 14 force loading lines on the contour image and align the geometric center of the contour with the center of the force loading line model. Determine the position of the basic stretching point by detecting the intersection points of each force loading line and the contour. To identify and locate stretching points, the outer contour of the leather needs to be extracted from the processed binary image. This paper uses the OpenCV library to call the cv2.findContours() function to extract the contour of the leather region in the binary image, thus obtaining the boundary information of the leather.

[0047] Based on the visualization of the single-pixel width outline of the leather area superimposed on a two-dimensional image, skeletonization technology is used to extract the skeleton lines that represent its topological structure and basic shape, and align them with the force loading model to determine the basic stretching point.

[0048] First, the highest and lowest points of the leather outline are obtained vertically. A horizontal center line is drawn with the center between these two points, dividing the leather into upper and lower halves. Next, intersection point detection is performed on the skeletal lines of the leather outline. The closest intersection points to the horizontal center line are selected in the skeletal regions above and below the center line, respectively, to obtain the corresponding vertebral nodes. Then, two vertebral nodes are connected, and the connection is extended towards the head and tail ends respectively until it intersects the outline, thus obtaining the leather's spine line. Subsequently, the leftmost and rightmost extreme contour points are extracted from the upper and lower halves of the outline, respectively, to represent the positions of the limb ends. These extreme points are then connected to the vertebral nodes of the corresponding halves, ultimately constructing the simplest skeleton under the ideal outline. Finally, the intersection of the horizontal midline and the ridge line is defined as the center point of the leather morphology, serving as the origin. A coordinate system is established in this system, with the ridge node located approximately one-third of the distance from the origin to the end points of the leather. Each ridge node is connected to the extreme points at the ends of its respective half-region; the direction of the connecting lines is consistent with the natural growth direction of the leather fibers. Applying tensile force along this direction allows for the smooth spreading of the leather. Therefore, the ridge line and the lines connecting the ridge nodes to the extreme points at the ends of the limbs constitute the necessary stretching directions during the leather spreading process. The intersections of these stretching directions with the leather contour are the six necessary stretching points, such as... Figure 15 As shown.

[0049] Based on the morphological characteristics of leather and the simplest skeleton under an ideal outline, the upper and lower halves of the leather are divided radially along the symmetrical axial edge of the spine, using the vertebral nodes of each half as vertices. Each half is divided into three regions. Region 1 is enclosed by two boundary lines symmetrical about the spine with a total angle of 45°, using the corresponding vertebral nodes as vertices. This region covers the area at the respective ends (head end in the upper half, tail end in the lower half) where the fiber direction is parallel to the spine. Within each region, two new rays extend outwards by rotating 60° from the two boundary rays of Region 1, forming a total of four new rays in the upper and lower halves. The angled area formed by these rays with the adjacent boundaries is Region 2, covering the limbs with similar fiber directions and their surrounding transitional areas. The remaining region is Region 3, corresponding to the rib and abdominal area, with a regular edge outline and fiber direction perpendicular to the spine.

[0050] Based on the initial division of the three regions, a total of 8 extending rays were formed. Considering the complex curve characteristics of the leather contour, regions two and three, which account for a larger proportion, were further divided into equal subdivisions. Finally, 14 force loading lines were constructed on the contour image, such as... Figure 16 As shown.

[0051] The intersection points of the leather profile and the line of force application were detected using the nearest neighbor projection method, and the leather profile points were traversed. Calculate its normalized projection parameters along the direction of the force loading line. By using this projection parameter, each point is projected onto the parameter space of the force loading line.

[0052] In the formula, As the starting point of the line of action of the force loading, The endpoint of the line of action of the force loading; To optimize computational efficiency, this invention establishes a dual-constraint criterion. First, the first constraint is applied... (in =1e 8 represents the floating-point calculation tolerance), quickly eliminating contour points located outside the extended region of the action line. For For candidate points within the valid interval, further calculate contour points. Its coordinates as an orthogonal projection point on the line of force application : Next, calculate the leather outline points. and projection point Euclidean distance: The second constraint uses the geometric distance relaxation condition (2-pixel tolerance) to compensate for small errors in the skeleton digitization process. When d≤2 pixels, the contour point is marked as a valid intersection point to ensure that the true intersection point is captured.

[0053] The dual constraint mechanism balances computational efficiency and detection accuracy. The first constraint is determined by projection parameters. The algorithm quickly filters out most irrelevant points, reducing computational load; the second constraint ensures robustness through distance tolerance, further improving the accuracy of intersection detection. The algorithm traverses 14 force application lines, executes the above process, and outputs as follows: Figure 17 The 14 basic stretching points are shown.

[0054] Step 4: Establish a zoning system in the upper and lower halves of the leather area. Detect the intersections of the parallel lines with the leather contour by arranging an array of equally spaced parallel lines, thereby supplementing auxiliary stretching points. Finally, integrate the basic and auxiliary stretching points to form a composite stretching point system with a rationally distributed layout throughout the entire area. In practice, firstly, using the vertebral node as a reference, based on the intersection relationship between 14 force loading lines and the leather contour, a total of 10 triangular regions and 4 trapezoidal regions are divided. A differentiated baseline generation strategy is adopted for the two types of regions: the baseline system for the triangular regions is constructed using the angle bisectors of their adjacent boundaries, while the force loading lines within the trapezoidal regions are directly used as the baseline. Then, within each region, equidistant parallel line clusters with a spacing of 10mm are symmetrically generated on both sides of the baseline, and the `clip_line_segment()` function is used to trim the line segments, retaining those completely within the region. For some cross-boundary line segments, the intersection points are calculated and precisely truncated. All parallel lines and the leather contour image are traversed, and intersection point detection is performed using a projection method to obtain dense reference points on the leather contour, such as... Figure 18 As shown. Finally, based on the obtained dense reference points, auxiliary stretching points are selected using the cumulative distance threshold method: within each partition, the starting point is the basic stretching point (the intersection of the baseline and the contour). Connect the reference points sequentially to the left / right to form an ordered sequence from the reference starting point to each intersection point. Construct a path chain from the starting point to the terminal point, and calculate the cumulative distance of each point relative to the starting point. : Total length of path chain This can be viewed as an approximate length of the leather outline within the region; a filtering threshold can be set. Starting from the starting point, accumulate the segmented distances. When the accumulated value... When, select the next intersection point. As an auxiliary stretching point, the tolerance The thickness is 5mm. Finally, the basic stretching points and auxiliary stretching points are integrated to generate a composite stretching point layout covering the entire leather area, such as... Figure 19 As shown.

Claims

1. A multi-directional linkage synchronous stretching leather stretching device, characterized in that, The system includes a spreading station (1), a stretching station (2), a gripping and hanging station (3), a disassembly and finishing station (4), and a stretching frame resetting station (5). The stretching station (2), gripping and hanging station (3), disassembly and finishing station (4), and stretching frame resetting station (5) all have the same main frame as the spreading station (1). The spreading station (1), gripping and hanging station (3), and disassembly and finishing station (4) are all equipped with Aobo robotic arms (6) for performing loading, hanging, disassembly, and finishing operations of leather. In addition, a transport vehicle (7) is also provided. The spreading station (1) includes a base (101), on which two pairs of oppositely arranged transmission device side plates (102) are provided, and a guide channel is formed between each pair of transmission device side plates (102). The conveyor belt (103) runs in the guide channel. The leather stretching mechanism (105) is set on the conveyor belt (103), and the leather (106) to be stretched is carried on the leather stretching mechanism (105). The leather stretching mechanism (105) includes a stretching frame and several circumferentially distributed stretching plates (105-3) arranged on the stretching frame. Each stretching plate (105-3) can extend and retract radially relative to the stretching frame. The leather (106) to be stretched is laid on the support surface formed by all the stretching plates (105-3) and is stretched and stretched as the stretching plates (105-3) expand outward. The leather stretching mechanism (105) carrying the leather (106) serves as the process carrier, and completes the corresponding processes at each station in sequence: the leather is loaded and initially positioned at the spreading station (1), and transported to the stretching station (2) to stretch and shape the leather. At the grabbing and hanging station (3), the Aobo robotic arm (6) grabs and transfers the leather to the drying chamber. After drying, the transport vehicle (7) transports the leather stretching mechanism (105) carrying the dried leather to the disassembly and finishing station (4). The Aobo robotic arm (6) at the disassembly and finishing station (4) removes the finished leather from the leather stretching mechanism (105) and places it on the transport vehicle (7) to the downstream process. Subsequently, the empty leather stretching mechanism (105) is transported to the stretching frame reset station (5) and reset, and then returns to the spreading station (1) for the next cycle of use.

2. The multi-directional linkage synchronous stretching leather stretching device according to claim 1, characterized in that, The tensioning frame includes an outer tensioning frame (105-1) and an inner tensioning frame (105-7) nested therein, both coaxial and symmetrically arranged; a crank disc bracket (105-9) is installed transversely inside the outer tensioning frame (105-1), with both ends fixedly connected to the side walls of the outer tensioning frame (105-1), and located at the center of the inner tensioning frame (105-7); two crank discs (105-6) are symmetrically arranged on the crank disc bracket (105-9) near the side of the outer tensioning frame (105-1), and each crank disc (105-6) is hinged to a tensioning plate (105-7). -3) A number of matching tension mechanism connecting rods (105-5); two crank discs (105-5) are connected by crank disc connecting rods (105-8); tension layer tracks (105-2) with guide grooves are evenly distributed between the outer frame (105-1) and the inner frame (105-7) of the tension layer, matching the number of tension plates (105-3). Tension plate sliders (105-4) are embedded in the guide grooves of the tension layer tracks (105-2), wherein the upper end of each tension plate slider (105-4) is connected to the tension plate (105-3), and the lower end is hinged to one end of the tension mechanism connecting rod (105-5); The main frame of the stretching station (2) is equipped with a motor lifting device (209). The motor lifting device (209) is coaxially connected to one of the crank discs (105-6), thereby driving the leather stretching mechanism (105) to stretch the leather (106) to be stretched.

3. The multi-directional linkage synchronous stretching leather stretching device according to claim 2, characterized in that, Below the crank disc bracket (105-9) is a leather stretching mechanism (105) with a stretching control locking mechanism. The stretching control locking mechanism includes a spring slide rod (105-10), a ratchet (105-14), and a fixed base. The ratchet (105-14) is keyed to the crank disc bracket (105-9) and is coaxially fixed to one of the crank discs (105-6), allowing them to rotate synchronously. The spring slide rod (105-10) is fixedly mounted to the crank disc bracket (105-9) via the fixed base. A spring (105-11) is fitted onto the spring slide rod (105-10). One end of (105-11) is connected to the fixed base, and the other end is connected to the unlocking slider (105-12). The unlocking slider (105-12) is connected to the slider roller (105-15) through the slider roller shaft (105-16). An unlocking device connecting rod (105-17) is installed on the side of the unlocking slider (105-12) near the crank disc bracket (105-9). The two ends of the unlocking device connecting rod (105-17) are respectively hinged to the unlocking slider (105-12) and the pawl (105-13). The pawl (105-13) is hinged to the crank disc bracket (105-9) and forms a meshing engagement with the ratchet (105-14). The motor lifting device (209) includes a motor bracket (209-1) installed in the main frame of the stretching station (2). Two sets of motor inner brackets (209-2) are symmetrically installed on the motor bracket (209-1). Each set of motor inner brackets (209-2) is equipped with an electric push rod (209-3). The motor support plate (209-5) is installed on the top of the two sets of electric push rods (209-3) and is fixedly connected to the output ends of both. A servo motor (209-7) is installed on the motor support plate (209-5) through a motor bracket (209-6). The output end of the servo motor (209-7) is connected to a rotary table (209-8). A stretching plate power shaft (209-9) that is connected to the crank disc (105-6) is installed on the rotary table (209-8). The front end of the stretching plate power shaft (209-9) is provided with a cylindrical shaft section and a conical boss structure in sequence. When the leather stretching mechanism (105) reaches the stretching station (2), the motor lifting device (209) moves upward, driving the motor support plate (209-5) to rise vertically via the electric push rod (209-3). The cylindrical shaft section of the stretching plate power shaft (209-9) passes into the center hole of the ratchet (105-14) and the crank disc (105-6) to achieve coaxial positioning. The return spring (105-11) is pre-compressed during assembly, and its length does not exceed the free length. The return spring (105-11) continuously applies a stable rightward axial thrust to the unlocking slider (105-12), causing the pawl (105-13) to fit tightly and engage in the tooth groove of the ratchet (105-14). The servo motor (209-7) rotates in the forward direction, driving the stretching plate power shaft (209-9). The rotation drives the ratchet (105-14) and the crank disc (105-6) coaxially connected to it to rotate. The pawl (105-13) slides over the tooth tip of the ratchet (105-14) along the direction of rotation, realizing a one-way overtaking function. During the rotation of the crank disc (105-6), the tensioning mechanism connecting rod (105-5) converts the rotational motion into linear thrust, driving the stretching plate slider (105-4) to make a radial outward linear translation along its corresponding stretching plate layer track (105-2). When the servo motor (209-7) stops outputting torque, the elastic recoil force of the leather attempts to reverse the crank disc (105-6) and the ratchet (105-14). The pawl (105-13) and the root of the ratchet (105-14) teeth mechanically interfere, forming a one-way self-locking. The main frame of the stretching frame reset station (5) is equipped with a motor lifting device. The structure of the motor lifting device is the same as that of the motor lifting device (209) in the stretching station (2), and the axial travel of the motor lifting device is greater than that of the motor lifting device (209) in the stretching station (2). The stretched leather stretching mechanism (105) is transferred to the stretching frame reset station (5). The motor lifting device of the stretching frame reset station (5) moves upward in the vertical direction. The conical boss structure on the stretching power shaft abuts upward and squeezes the slider roller (105-15) laterally, causing the unlocking slider (105-12) to overcome the thrust of the reset spring (105-11) and move radially backward, thereby pulling the pawl (105-13) to forcibly disengage from the tooth groove of the ratchet (105-14); the locked state is released. Then, the servo motor (209-7) rotates in the opposite direction, driving the stretching plate power shaft (209-9) to rotate, which in turn drives the ratchet (105-14) and the crank disc (105-6) connected to it to rotate in the opposite direction, thereby pulling the stretching mechanism connecting rod (105-5), which drives the stretching plate slider (105-4) to make a radial inward linear retraction along the stretching plate layer track (105-2); finally, each stretching plate (105-3) synchronously retracts to the center position, completing the full reset of the leather stretching mechanism (105).

4. The multi-directional linkage synchronous stretching leather stretching device according to claim 3, characterized in that, The main frame of the stretching station (2) is provided with an actuator magnet picking and placing mechanism. The actuator magnet picking and placing mechanism includes a truss-type robotic arm base (201). A camera bracket (202) and a crossbeam (203) are installed on the truss-type robotic arm base (201). An industrial camera (205) and a light source (206) are installed on the top of the camera bracket (202). A truss-type robotic arm (204) capable of linear movement along the X-axis, Y-axis and Z-axis is installed on the crossbeam (203). A magnet pick-and-place actuator drive motor (2010) is provided at the end of the gantry-type robotic arm (204). A magnet pick-and-place actuator (2011) is installed on the magnet pick-and-place actuator drive motor (2010). An electromagnet storage box (207) is installed below the crossbeam (203). The electromagnet storage box (207) contains a de-energized electromagnet (208). The magnet pick-and-place actuator (2011) is configured to automatically pick up the de-energized electromagnet (208) from the electromagnet storage box (207) according to the stretching point coordinates output by the stretching point identification and positioning algorithm, and accurately place it on the stretching point position corresponding to the leather surface to achieve fixed-point pressing and fixing of the leather (106).

5. A multi-directional linkage synchronous stretching leather stretching device according to claim 4, characterized in that, A magnet recycling device (401) is provided on one side of the main frame of the disassembly and sorting station (4). An electromagnet storage box conveying device (403) is installed below the magnet recycling device (401). On both sides of the magnet recycling device (401), there are Aobo robotic arms (6) with hook actuators (301) at the end and Aobo robotic arms (6) with suction cup end actuators (402) at the end. The magnet recycling device (401) includes a suspension rod and a magnet collection cavity. The suspension rod is used to suspend the leather stretching mechanism (105). When the leather stretching mechanism (105) is attached to the suspension rod, a power supply path is formed. The magnet collecting chamber is located below the suspension rod. The top of the magnet collecting chamber is provided with a feed opening for receiving the de-energized electromagnet (208), and the bottom is provided with a discharge outlet. The discharge outlet is connected to the electromagnet storage box conveying device (403) via a feeding plate (404). The push rod (405) is arranged on one side of the feed plate (404), and its movement direction is consistent with the length direction of the feed plate (404). It is used to push the de-energized electromagnet (208) placed on the feed plate (404) into the electromagnet storage box (207) along this direction. The electromagnet storage box conveying device (403) is arranged around the stretching station (2) and the disassembly and sorting station (4), including a circular conveying track (403-1) laid on the ground. A branch conveying track (403-2) connected to the circular conveying track (403-1) is also provided on one side of the circular conveying track (403-1) to form a material replenishment bypass. The branch conveying track (403-2) is adjacent to the discharge outlet of the magnet recycling device (401). Empty electromagnet storage boxes (207) are conveyed through the branch conveying track (403-2) to the area below the electromagnet discharge outlet of the magnet recycling device (401) for filling. After the electromagnet storage box (207) is filled with de-energized electromagnets (208), it returns to the circular conveying track (403-1) and is conveyed to the stretching station (2).

6. A multi-directional linkage synchronous stretching leather stretching device according to claim 5, characterized in that, The electromagnet storage box (207) is an integrated shell with an upper triangle and a lower rectangle, and a permanent magnet is embedded in the apex of the triangle. A Hall sensor is provided upstream of the entrance of the branch conveyor track (403-2) near the circular conveyor track (403-1). A sorting baffle (403-3) is provided at the entrance of the branch conveyor track (403-2) and is connected to the Hall sensor signal. It is configured such that when an empty electromagnet storage box (207) moves to the position of the Hall sensor in a positive posture, in response to the trigger signal generated by the permanent magnet passing through the sensing area of ​​the Hall sensor, the empty electromagnet storage box (207) is diverted into the branch conveyor track (403-2). The branch transmission track (403-2) includes a left track and a right track arranged in parallel. A longitudinal gap extending along the conveying direction is formed between the two tracks and is adapted to the electromagnet storage box (207). A lifting rotary table (403-4) is provided on the branch transmission track (403-2) at the position corresponding to the feeding plate (404). The lifting rotary table (403-4) is located directly below the longitudinal gap of the branch transmission track (403-2). Its initial position is lower than the top surface of the track. It includes a liftable table and a rotary mechanism that rotates around the vertical axis. A pressure sensor is installed at the bottom of the liftable table to determine whether the electromagnet storage box (207) is full. The lifting rotary table (403-4) is configured such that when the electromagnet storage box (207) moves along the branch conveyor track (403-2) to the top of the lifting rotary table (403-4), the lifting rotary table (403-4) rises to lift the electromagnet storage box (207) so that it is removed from the track support; then, when the electromagnet storage box (207) is in a suspended state, the recovered magnet is loaded into the electromagnet storage box (207) through the feeding plate (404); after the loading is completed, the lifting rotary table (403-4) rotates 180° to complete the reorientation of the electromagnet storage box (207); after the reorientation is completed, the table descends and the loaded and reoriented storage box is put back on the branch conveyor track (403-2) to continue the subsequent conveying.

7. A multi-directional linkage synchronous stretching leather stretching device according to claim 4, characterized in that, The stretching point identification and positioning algorithm is specifically a stretching point selection method based on partitioned equidistant parallel lines, including the following steps: Step 1: Construct a model of the line of action of the force loading. The intersection of the extended lines of the head and tail endpoints and the limb endpoints in the idealized leather model is used as the morphological reference center to replace the traditional centroid positioning method. Based on this morphological reference center, the leather area is divided into multiple sub-regions, and the main stretching direction is set along the angle bisector of each sub-region. At the same time, auxiliary stretching directions are added in highly deformable and sensitive areas in the leather outline that have significant lateral extension, local outward convexity, or dramatic curvature changes, to construct a force loading action line model. Step 2: After acquiring the leather image, perform grayscale processing, Gaussian blur denoising, and binarization processing on the image in sequence. Then, perform morphological operations on the binarized image and finally extract the contour to remove noise and background interference and obtain a leather recognition image with smooth edges and completeness. Step 3: Use OpenCV's contour extraction function to obtain the single-pixel-wide outer contour of the leather, and divide the leather region into upper and lower halves based on its geometric center; construct 14 force loading lines on the contour image, and align the geometric center of the contour with the center of the force loading line model; determine the position of the basic stretching point by detecting the intersection of each force loading line with the contour. Step 4: Establish a zoning system in the upper and lower halves of the leather area. Detect the intersection of the parallel lines with the leather outline by arranging an array of equally spaced parallel lines, thereby supplementing auxiliary stretching points. Finally, integrate the basic and auxiliary stretching points to form a composite stretching point system with a reasonable layout throughout the entire area.

8. A multi-directional linkage synchronous stretching leather stretching device according to claim 7, characterized in that, The location of the basic tension point mentioned in step 3 is determined through the following steps: (1) Determine the necessary stretching points The highest and lowest points of the leather outline are obtained vertically. A horizontal center line is drawn with the center between these two points, dividing the leather into upper and lower halves. Intersection point detection is performed on the skeletal lines of the leather outline. The closest intersection points to the horizontal center line are selected in the skeletal regions above and below the center line, respectively, to obtain the corresponding ridge nodes. Two ridge nodes are connected, and the line is extended towards the head and tail ends respectively until it intersects the outline, thus obtaining the leather's backline. The leftmost and rightmost extreme contour points are extracted from the upper and lower halves of the outline, respectively, and these extreme points are connected to the ridge nodes of the corresponding halves. Finally, the simplest skeleton under the ideal outline is constructed; then, the intersection of the horizontal midline and the spine line is defined as the center point of the leather morphology, and a coordinate system is established as the origin. In this coordinate system, the spine nodes are located at about one-third of the distance from the origin to the end points of the leather. Each spine node is connected to the extreme point of the limb ends of its respective half-region, and the direction of the connecting line is consistent with the natural growth direction of the leather fibers. Therefore, the spine line and the lines connecting the spine nodes to the extreme points of the limb ends constitute the necessary stretching directions in the leather spreading process; the intersections of these stretching directions with the leather outline are the six necessary stretching points. (2) Based on the morphological characteristics of the leather and the simplest skeleton under the ideal contour, the upper and lower halves of the leather are divided into three regions each, with the vertebral nodes of the upper and lower halves as vertices, and radially divided along the symmetrical axial edge of the spine line. Fourteen force loading lines are constructed on the contour image. Region 1 is bounded by two boundary lines that are symmetrical about the spine line with the corresponding vertebral nodes as vertices and have a total included angle of 45°. Within each region, two new rays are extended outward by rotating 60° from the two boundary rays of Region 1 as references. Four new rays are formed by dividing the upper and lower regions. The angled region enclosed by the upper and lower regions and the adjacent boundary is region two, and the remaining region is region three. Based on the initial division of the three regions, a total of eight extended rays are formed. Region two and region three are divided into equal parts and then subdivided twice. Finally, 14 force loading lines are constructed on the contour image. (3) Detect the intersection of the leather profile and the line of force application to determine the basic tension point. The intersection points of the leather profile and the line of force application were detected using the nearest neighbor projection method, and the leather profile points were traversed. Calculate its normalized projection parameters along the direction of the force loading line. Using this projection parameter, each point is projected onto the parameter space of the force loading line: In the formula, As the starting point of the line of action of the force loading, The endpoint of the line of action of the force loading; for For candidate points within the valid interval, further calculate contour points. Its coordinates as an orthogonal projection point on the line of force application : Next, calculate the leather outline points. and projection point Euclidean distance: The algorithm traverses 14 lines of force application to obtain 14 basic tension points.

9. A multi-directional linkage synchronous stretching leather stretching device according to claim 8, characterized in that, The auxiliary stretching point mentioned in step 4 is determined through the following steps: First, using the vertebral node as a reference, based on the intersection relationship between 14 force loading lines and the leather contour, a total of 10 triangular regions and 4 trapezoidal regions are divided. A differentiated baseline generation strategy is adopted for the two types of regions: the baseline system of the triangular regions is constructed by the angle bisectors of their adjacent boundaries, while the force loading lines inside the trapezoidal regions are directly used as the baseline. Then, in each region, equidistant parallel line clusters with a spacing of 10mm are symmetrically generated on both sides of the baseline, and the clip_line_segment() function is used to trim the line segments, retaining the line segments that are completely within the region, and calculating the intersection points of some cross-boundary line segments for precise cutting. The algorithm iterates through all parallel lines and the leather contour image, using projection to detect intersections and obtain dense reference points on the leather contour. Finally, based on the obtained dense reference points, auxiliary stretching points are selected using a cumulative distance thresholding method: within each partition, starting from the base stretching point... Connect the reference points sequentially to the left / right to form an ordered sequence from the reference starting point to each intersection point. Construct a path chain from the starting point to the end point, and calculate the cumulative distance of each point on the path relative to the starting point. : Total length of path chain This can be viewed as an approximate length of the leather outline within the region; a filtering threshold can be set. Starting from the starting point, accumulate the segmented distances. When the accumulated value... When, select the next intersection point. As an auxiliary stretching point, the tolerance It is 5mm.

10. A multi-directional linkage synchronous stretching leather stretching device according to claim 9, characterized in that, A roller drive shaft (1013) is provided between the two pairs of transmission device side plates (102). The two ends of the roller drive shaft (1013) are respectively installed on the transmission device side plates (102), and the conveyor belt (103) is wound around the roller drive shaft (1013). The leather stretching mechanism (105) is set on the conveyor belt (103), is carried by the conveyor belt (103) and runs with it. The leather (106) to be stretched is carried on the leather stretching mechanism (105). On both sides of the spreading station (1), there are Aobo robotic arms (6) with leather operation end actuators (1014) at the end, which are used to spread the leather (106) to be stretched on the leather stretching mechanism (105). A guide roller side plate (107) is fixedly installed on the outer side of each transmission device side plate (102), and a set of guide rollers (104) is installed on the guide roller side plate (107). Each set contains sixteen guide rollers (104). The outer circumferential surface of the guide rollers (104) rolls in contact with the lateral guide surface of the leather stretching mechanism (105). A transmission motor (1012) is installed on the base (101) via a motor bracket (1011). The output shaft of the transmission motor (1012) is connected to a large pulley (108). A small pulley (109) is installed on the roller transmission shaft (1013) and is connected to the large pulley (108) via a transmission belt (1010). A tensioning frame locking mechanism (209-4) is also provided between the motor bracket (209-1) and the motor support plate (209-5). The tensioning frame locking mechanism (209-4) includes a tensioning frame locking mechanism bracket (209-4-3) fixed at the upper edge of the motor bracket (209-1). The tensioning frame locking claw (209-4-1) is hinged to the tensioning frame locking mechanism bracket (209-4-3) and is hinged to one end of the tensioning frame locking push rod (209-4-4) via the locking claw connecting rod (209-4-2). The other end of the tensioning frame locking push rod (209-4-4) is connected to the tensioning frame locking push rod bracket (209-4-5) fixed on the motor support plate (209-5).

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