A method for robot single-sided sewing and continuous knotting of three-dimensional fabric

Abstract

The present application belongs to the technical field of intelligent sewing equipment and garment automation production, and particularly relates to a method for robot single-side sewing and continuous knotting of three-dimensional fabric, comprising the following steps: obtaining a target sewing line to generate a sewing point sequence; establishing a local sewing coordinate system according to a tangent and a normal for each sewing point; determining a sewing needle posture and a needle entry point in the local sewing coordinate system, moving a single-side sewing device to the needle entry point through RGB-D visual servo control of a sewing robot arm; completing puncture, clip replacement and thread extraction on one side of a workpiece through the single-side sewing device to form a stitch; repeating the above steps until a knotting condition is met, and controlling a thread manipulator driven by an auxiliary robot arm to cooperatively perform continuous knotting with the sewing robot arm, including holding the sewing line and applying a target tension, capturing a thread segment to form a knot, and tightening the knot under thread tension feedback. The present application can complete automatic sewing, automatic knotting and stable reinforcement of three-dimensional curved surface workpieces.

Description

Technical Field

[0001] This invention relates to the technical field of intelligent sewing equipment and automated garment production, specifically to a method for robotic single-sided sewing and continuous knotting of three-dimensional fabrics. Background Technology

[0002] In the manufacturing of automotive interior trim, three-dimensional shoe uppers, irregularly shaped bag covers, tubular fabric components, and other three-dimensional fabric products, it is often necessary to complete reinforcement seams, connecting seams, or overlock seams along spatial curves on curved workpieces. These workpieces typically have characteristics such as narrow internal cavities, difficulty in reaching the back side, large local curvature variations, and soft, easily deformable materials. Traditional flat sewing machines and manual sewing methods are inefficient, unstable, and difficult to guarantee consistent stitch length and knot quality.

[0003] Existing automated sewing technologies are mostly geared towards feeding flat or near-flat fabric pieces. For three-dimensional workpieces, if conventional double-sided needle feeding or presser foot feeding methods are still used, special fixtures, complex flipping mechanisms, or manual assistance are often required. If only industrial robots are relied upon to feed needles along a preset spatial trajectory, due to workpiece clamping errors, changes in the surface normal, and flexible deformation, it is difficult for the needle to be accurately aligned with the target needle entry point, which can easily lead to missed needles, off-center needles, and inconsistent stitch sizes.

[0004] In existing technologies, the following technical solutions exist: a semi-automatic sewing solution using a traditional flatbed sewing machine with a dedicated fixture; an open-loop sewing solution where an industrial robot performs punctures according to preset spatial points; and an automatic sewing device that only provides single threading and lacks continuous automatic knot-tying capabilities. These solutions have at least the following drawbacks: they require a workpiece back-side reachable or complex flipping mechanism, making them unsuitable for three-dimensional fabric components with a single-sided reachable surface; they lack the ability to plan the needle posture in real time based on the workpiece surface normal and the seam tangent; they are insensitive to clamping errors, and open-loop execution easily leads to needle deviation and missed stitches; and they lack automatic thread control and knot-tightening mechanisms, making truly continuous unmanned sewing impossible. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for robotic single-sided sewing and continuous knotting of three-dimensional fabrics, which can automatically sew, automatically knot, and stabilize and reinforce three-dimensional curved workpieces.

[0006] To solve the above-mentioned technical problems, the objective of this invention is achieved through the following technical solution: A method for robotic single-sided sewing and continuous knotting of three-dimensional fabrics includes the following steps: (1) Obtain the target seam on the three-dimensional structured fabric part, and generate a seam point sequence based on the target seam; (2) For each target seam point, establish a local sewing coordinate system based on the tangential direction between the seam point and the adjacent seam points and the normal direction of the workpiece surface; (3) In the local sewing coordinate system, the needle target posture and needle entry point are determined according to the preset stitch size, and the single-sided sewing device is moved to the needle entry point by the RGB-D vision servo control sewing robot arm; (4) The single-sided sewing device completes the piercing, clamp changing and thread pulling actions on one side of the workpiece to form a stitch; (5) Repeat steps (2) to (4) until the knotting conditions are met. When the knotting conditions are met, the thread manipulator driven by the auxiliary robotic arm controls the continuous knotting to be performed in conjunction with the sewing robotic arm. The continuous knotting includes: the thread manipulator pulls the thread and applies the target tension, the sewing robotic arm captures the thread segment and forms a knot, and the knot is tightened under the feedback of the thread tension.

[0007] As a further improvement of the present invention, in step (3), the needle entry point is determined by offsetting half a stitch size along the stitch line direction based on the current stitch point.

[0008] As a further improvement of the present invention, the single-sided sewing device includes a first clamping jaw, a second clamping jaw, and a double-pointed semi-circular needle; the piercing, clamp changing and thread pulling actions in step (4) specifically include: the first clamping jaw pushes the double-pointed semi-circular needle into the workpiece, so that the needle rotates along the curved surface and passes through the workpiece, the second clamping jaw takes over the needle, and the sewing robot arm pulls the thread to form a stitch.

[0009] As a further improvement of the present invention, the RGB-D visual servo includes: setting an identifiable mark array on the outer surface of the single-sided sewing device, acquiring the image and depth information of the mark array through an RGB-D camera, calculating the pose error of the sewing robot arm end relative to the target seam point, and outputting a correction speed command.

[0010] As a further improvement of the present invention, the online tension feedback in the continuous knotting includes: the tension sensor built into the thread controller detects the suture tension in real time, and the auxiliary robotic arm adjusts its posture according to the deviation between the detected tension and the target tension, until the tension reaches the target and then outputs a knotting permission signal.

[0011] As a further improvement of the present invention, in the local sewing coordinate system, one coordinate axis is along the tangential direction of the sewing thread, another coordinate axis is along the normal direction of the workpiece surface, and the third coordinate axis is obtained by the cross product of the first two coordinate axes.

[0012] As a further improvement of the present invention, when the sewing needle rotates along the curved surface in step (4), the continuous rotation is decomposed into multiple discrete small-angle posture adjustment steps to reduce the interference between the needle body and the workpiece or the support mold core.

[0013] The present invention also provides a robotic system for single-sided sewing and continuous knotting of three-dimensional fabrics, for performing the above-described method, the system comprising: The dual-arm execution module includes a sewing robotic arm and an auxiliary robotic arm; A single-sided sewing device, installed at the end of a sewing robot arm, is used to complete piercing, clamp changing, and thread pulling from one side of the workpiece. A thread manipulator, installed at the end of an auxiliary robotic arm, is used to hold the thread, apply tension, and assist in forming a knot during the knotting stage. The RGB-D vision acquisition module is used to acquire point clouds on the surface of workpieces and mark arrays on single-sided sewing devices. The seam point trajectory planning module is used to generate a sequence of seam points based on the target seam line and establish a local sewing coordinate system for each seam point; The visual servo control module is used to calculate the pose error based on RGB-D visual information and output correction commands. The force feedback knotting control module is used to control the auxiliary robotic arm to maintain the target tension based on the tension detection results of the thread manipulator, and to coordinate the sewing robotic arm to complete the knot formation and tightening. The central control and scheduling module is used to coordinate the state machine timing execution between the sewing robot arm, the auxiliary robot arm, and various modules.

[0014] As a further improvement of the present invention, it also includes a support core module, which matches the inner cavity or outer contour of the three-dimensional structured fabric part and provides a clearance area near the target seam for the sewing needle to pass through.

[0015] The present invention also provides a robotic sewing workstation, including dual robotic arms, a single-sided sewing device, a thread manipulator, an RGB-D camera, a support mold core, and a control device; the control device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the program to implement the above-described method.

[0016] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method.

[0017] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a single-sided sewing device consisting of a double clamping jaw and a double-pointed semi-circular needle. It can complete piercing and thread pulling by approaching the workpiece from only one side, completely solving the problem of automatic sewing of three-dimensional fabric parts with narrow inner cavities and inaccessible back sides, without the need for complex flipping mechanisms or manual assistance.

[0019] This invention innovatively proposes a local sewing coordinate system planning method based on the tangential direction of the sewing thread and the normal direction of the workpiece surface. At each sewing point, the tangential direction is calculated based on adjacent sewing points, and the normal direction is obtained from the workpiece surface model or real-time point cloud. This establishes a local coordinate system and precisely plans the needle's entry posture and puncture direction. This mechanism ensures that the needle is always perpendicular to the surface or punctures at a preset angle, significantly improving the consistency of stitches on complex surfaces and avoiding problems such as missed or off-center stitches caused by changes in the surface normal direction. The method of determining the specific entry point by offsetting half a stitch dimension along the sewing thread direction from the current sewing point further guarantees the uniformity of the stitch length.

[0020] This invention employs RGB-D vision servo closed-loop control. By setting a marker array on the outer surface of the single-sided sewing device, it observes and calculates the six-dimensional pose error between the end effector and the target sewing point in real time, and outputs a correction speed command. This scheme can effectively compensate for workpiece clamping errors, robot absolute positioning errors, and local deformation of curved surfaces, improving the needle positioning accuracy to the sub-millimeter level and overcoming the insensitivity of open-loop control to errors.

[0021] This invention employs a dual-robotic arm collaborative architecture. The sewing robotic arm is responsible for single-sided sewing, while the auxiliary robotic arm, carrying a thread controller, is responsible for thread tension adjustment and knotting. Both operate alternately under the state machine management of the central control and scheduling module, integrating continuous automatic knotting with three-dimensional curved surface single-sided sewing into a unified process for the first time. Force feedback tension control is introduced during the knotting process. The thread controller's built-in tension sensor monitors the thread force in real time, and the auxiliary robotic arm dynamically adjusts its posture to maintain the target tension, ensuring consistent tightening force for each knot and stable, reliable knot quality, truly achieving unmanned continuous sewing.

[0022] This invention decomposes the continuous rotation of the sewing needle along the curved surface into multiple discrete small-angle posture adjustment steps, effectively reducing mechanical interference between the needle body, the workpiece, and the supporting mold core, thus improving the dimensional accuracy of the stitches and the reliability of the system. The supporting mold core matches the contour of the workpiece and provides a clearance area near the suture line, offering stable support conditions and a safe space for unilateral puncture.

[0023] This invention is applicable to personalized, irregularly shaped, and small-batch three-dimensional fabric products. When changing shapes, only the support mold core needs to be replaced and new target seam data needs to be imported. It has a high degree of flexibility and has a wide range of industrial applications. Attached Figure Description

[0024] Figure 1This is an overall flowchart of the robot single-sided sewing and continuous knotting method for three-dimensional fabrics according to the present invention.

[0025] Figure 2 This is a schematic diagram of the module composition of the robotic single-sided sewing and continuous knotting system for three-dimensional fabrics according to the present invention.

[0026] Figure 3 This is a flowchart of the process of establishing a local sewing coordinate system and planning the stitch posture based on the tangential direction of the sewing thread and the normal direction of the workpiece surface in this invention.

[0027] Figure 4 This is a block diagram of the visual servo positioning control based on an RGB-D camera and a device marker array in this invention.

[0028] Figure 5 This is a flowchart illustrating the puncture, rotation, clamp change, and thread extraction process for a single needle stitch in this invention.

[0029] Figure 6 This is a flowchart of continuous knotting assisted by a thread manipulator in this invention.

[0030] Figure 7 This is the flowchart of the knot-tying closed-loop control in this invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] This embodiment provides a robotic single-sided sewing and continuous knotting system for three-dimensional fabrics, and a method based on this system. Figure 1 As shown, the overall process of this method includes: installing the three-dimensional fabric part, obtaining the workpiece pose, reading the target seam, generating the seam point sequence, establishing a local sewing coordinate system, locating the single-sided sewing device, executing a single stitch, and cyclically judging whether the knotting conditions and all seams are completed. When the knotting conditions are met, continuous knotting is executed, and finally the sewing ends.

[0033] System Composition like Figure 2 As shown, the system includes: a dual-arm execution module, one of which is a sewing arm and the other is an auxiliary arm; a single-sided sewing device installed at the end of the sewing arm; a thread manipulator installed at the end of the auxiliary arm; an RGB-D vision acquisition module; a support mold core module; a seam point trajectory planning module; a vision servo control module; a force feedback knotting control module; and a central control scheduling module. The dual arms are preferably seven-DOF collaborative robots to adapt to complex obstacle avoidance and posture adjustment around the three-dimensional curved workpiece. The support mold core is generated based on the workpiece CAD model, matching the inner cavity or outer contour of the three-dimensional fabric part, and has clearance grooves near the target seam for needle passage.

[0034] Step S1: Install the workpiece and perform initial positioning The three-dimensional fabric component is fitted or attached to the support mold core to maintain a stable shape. The overall control and scheduling module is activated, and the RGB-D vision acquisition module acquires the point cloud of the workpiece surface and the array of dot markers on the outer surface of the single-sided sewing device. The initial pose positioning of the workpiece and the sewing device is completed using the pre-calibrated camera and robot base coordinate system extrinsic parameter matrix.

[0035] Step S2: Generate the seam point sequence and local sewing coordinate system The stitch trajectory planning module reads the target suture data, which can be obtained from a CAD model, process path file, or manual teaching. Based on the preset stitch spacing, it discretizes the target suture to generate a sequence of stitch points. For example... Figure 3 As shown, perform the following operations for each target seam point: Read the three-dimensional coordinates of the current seam point and its adjacent seam points, and calculate the difference vector between the two points as the tangential direction of the seam. Query the normal vector at the point from the point cloud or CAD model on the workpiece surface. The normal vector is perpendicular to the surface and points outward from the workpiece. A local sewing coordinate system is established by taking the tangential direction as the first coordinate axis, the normal direction as the second coordinate axis, and the cross product of the two to obtain the third coordinate axis.

[0036] In the local sewing coordinate system, the target posture of the needle is determined according to the preset stitch size (e.g., stitch length, puncture depth). Using the current sewing point as a reference, the needle is offset by half a stitch size along the tangential direction of the sewing line to determine the precise position of the needle entry point.

[0037] Step S3: RGB-D Visual Servo Positioning like Figure 4 As shown, the RGB-D vision acquisition module acquires images and depth information of the marker array on the single-sided sewing device in real time. The vision servo control module extracts the pixel coordinates of the marker array, reconstructs the six-dimensional pose of the device in the robot's base coordinate system using the depth data, and compares it with the target needle insertion pose calculated in step S2 to obtain the pose error. Based on the error, a correction speed command is generated to drive the sewing robot arm to precisely move the single-sided sewing device to the target needle insertion point, aligning the needle axis with the normal direction of the local coordinate system.

[0038] Step S4: Perform a single stitch like Figure 5 As shown, the single-sided sewing device completes the following sub-steps on one side of the workpiece: The first clamping jaws clamp and push the double-pointed semi-circular needle, so that the needle tip enters from one side of the workpiece; After the needle penetrates the workpiece, based on the change in the surface normal, the sewing robot arm drives the device to perform continuous small-angle rotations around the needle entry point, causing the needle to gradually exit along the interior of the surface. This continuous rotation is decomposed into multiple discrete small-angle posture adjustment steps to reduce interference between the needle and the workpiece or supporting mold core; Once the needle reaches the predetermined exit position, the second jaw-clamping suture needle is engaged. The sewing robot arm pulls the device away from the workpiece along the planned thread-pulling trajectory, pulls out the sewing thread, and forms a complete single-sided stitch. The sewing robot arm returns to the standby position, ready for the next stitch or knotting action.

[0039] Step S5: Determining Knotting Conditions and Performing Continuous Knotting After each stitch is completed, the central control scheduling module determines whether the knotting conditions are met (e.g., a preset threshold for the number of stitches or a set value for suture tension). If met, continuous knotting is executed, such as... Figure 6 , Figure 7 As shown: The auxiliary robotic arm drives the thread manipulator to the suture position, and its flexible guide hook pulls the suture and applies a preset target tension. The tension sensor built into the thread manipulator detects the suture tension in real time and sends the signal to the force feedback knotting control module. This module compares the measured tension with the target tension. If the deviation exceeds the allowable range, it controls the auxiliary robotic arm to fine-tune its posture to change the tension until the tension reaches the target. Once the tension reaches the target, a knotting permission signal is output. The sewing robot arm returns to the standby position, and the thread controller holds a section of thread between two flexible guide hooks, forming a winding path; The sewing robot arm controls a single-sided sewing device to capture the thread segment, and completes the formation of a hand knot or equivalent knot through a double-pointed semi-circular needle and a clamping switching mechanism; After the knot is formed, the auxiliary robotic arm changes the posture of the guide hook to release the knot, and the sewing robotic arm pulls the thread along the predetermined guide path to tighten and fix the knot under tension feedback.

[0040] Step S6: Repeat until completion. Repeat steps S2 to S5 until all seam points along the entire 3D seam have been executed and knotted as required. The central control module issues a termination command, and the dual robotic arms return to their origin, completing the sewing process.

[0041] The robot single-sided sewing and continuous knotting method and system provided in this embodiment are applicable to the automatic sewing of three-dimensional fabric parts such as automotive interior coverings, three-dimensional shoe uppers, irregularly shaped bag coverings, and tubular fabric components.

[0042] Those skilled in the art should understand that the above embodiments are merely illustrative and the present invention is not limited thereto. For example, the double-pointed semi-circular needle in the single-sided sewing device can be replaced with an arc-shaped needle, a flexible needle, or an irregularly shaped piercing needle; the clamping mechanism can be replaced with an electric gripper, a magnetic lock, or an elastic clamp. The thread manipulator can employ a flexible guide hook, gripper, roller, wire groove, or tension wheel, etc. The dual robotic arms can be replaced with an industrial robot, a collaborative robot, a gantry mechanism, or a combination of a main arm and an auxiliary wire control mechanism. All these alternatives should fall within the protection scope of the present invention.

Claims

1. A method for robotic single-sided sewing and continuous knotting of three-dimensional fabrics, characterized in that, Includes the following steps: (1) Obtain the target seam on the three-dimensional structured fabric part, and generate a seam point sequence based on the target seam; (2) For each target seam point, establish a local sewing coordinate system based on the tangential direction between the seam point and the adjacent seam points and the normal direction of the workpiece surface; (3) In the local sewing coordinate system, the needle target posture and needle entry point are determined according to the preset stitch size, and the single-sided sewing device is moved to the needle entry point by the RGB-D vision servo control sewing robot arm; (4) The single-sided sewing device completes the piercing, clamp changing and thread pulling actions on one side of the workpiece to form a stitch; (5) Repeat steps (2) to (4) until the knotting conditions are met. When the knotting conditions are met, the thread manipulator driven by the auxiliary robotic arm controls the continuous knotting to be performed in conjunction with the sewing robotic arm. The continuous knotting includes: the thread manipulator pulls the thread and applies the target tension, the sewing robotic arm captures the thread segment and forms a knot, and the knot is tightened under the feedback of the thread tension.

2. The method for single-sided sewing and continuous knotting of three-dimensional fabrics by a robot according to claim 1, characterized in that, In step (3), the needle entry point is determined by offsetting half a stitch size along the suture direction based on the current suture point.

3. The method for single-sided sewing and continuous knotting of three-dimensional fabrics by a robot according to claim 1, characterized in that, The single-sided sewing device includes a first clamping jaw, a second clamping jaw, and a double-pointed semi-circular needle; the piercing, clamp changing, and thread pulling actions in step (4) specifically include: the first clamping jaw pushes the double-pointed semi-circular needle into the workpiece, causing the needle to rotate along the curved surface and pass through the workpiece, the second clamping jaw takes over the needle, and the sewing robot arm pulls the thread to form a stitch.

4. The method for single-sided sewing and continuous knotting of three-dimensional fabrics by a robot according to claim 1, characterized in that, The RGB-D visual servo system includes: setting an identifiable marker array on the outer surface of the single-sided sewing device, acquiring the image and depth information of the marker array through an RGB-D camera, calculating the pose error of the sewing robot arm end relative to the target seam point, and outputting a correction speed command.

5. A method for single-sided sewing and continuous knotting of three-dimensional fabrics using a robot, as described in claim 1, is characterized in that... The online tension feedback in the continuous knotting process includes: the tension sensor built into the thread controller detects the suture tension in real time, and the auxiliary robotic arm adjusts its posture according to the deviation between the detected tension and the target tension until the tension reaches the target and then outputs a knotting permission signal.

6. A method for single-sided sewing and continuous knotting of three-dimensional fabrics using a robot, as described in claim 1, is characterized in that... In the local sewing coordinate system, one coordinate axis is along the tangential direction of the sewing line, another coordinate axis is along the normal direction of the workpiece surface, and the third coordinate axis is obtained by the cross product of the first two coordinate axes.

7. A method for single-sided sewing and continuous knotting of three-dimensional fabrics using a robot, as described in claim 1, is characterized in that... In step (4), when the needle rotates along the curved surface, the continuous rotation is decomposed into multiple discrete small-angle posture adjustment steps to reduce interference between the needle body and the workpiece or support mold core.

8. A robotic system for single-sided sewing and continuous knotting of three-dimensional fabrics, characterized in that, The system for performing the method according to any one of claims 1 to 7 comprises: The dual-arm execution module includes a sewing robotic arm and an auxiliary robotic arm; A single-sided sewing device, installed at the end of a sewing robot arm, is used to complete piercing, clamp changing, and thread pulling from one side of the workpiece. A thread manipulator, installed at the end of an auxiliary robotic arm, is used to hold the thread, apply tension, and assist in forming a knot during the knotting stage. The RGB-D vision acquisition module is used to acquire point clouds on the surface of workpieces and mark arrays on single-sided sewing devices. The seam point trajectory planning module is used to generate a sequence of seam points based on the target seam line and establish a local sewing coordinate system for each seam point; The visual servo control module is used to calculate the pose error based on RGB-D visual information and output correction commands. The force feedback knotting control module is used to control the auxiliary robotic arm to maintain the target tension based on the tension detection results of the thread manipulator, and to coordinate the sewing robotic arm to complete the knot formation and tightening. The central control and scheduling module is used to coordinate the state machine timing execution between the sewing robot arm, the auxiliary robot arm, and various modules.

9. A robotic single-sided sewing and continuous knotting system for three-dimensional fabrics according to claim 8, characterized in that, It also includes a support core module, which matches the inner cavity or outer contour of the three-dimensional structured fabric part and provides a clearance area near the target seam for the sewing needle to pass through.

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