Multi-layer cloth detecting and sewing method

Abstract

The invention provides a multi-layer cloth detection sewing method which is used for business suit welt pocket layering processing and comprises the steps that a reference stitch set is sewn in a follow-up seam allowance area covered with pocket cloth, the left end of a pocket opening is a first reference stitch set with two short linear back stitch sections, and the right end of the pocket opening is a second reference stitch set with three short linear back stitch sections; after covering the pocket cloth, scanning and sampling in a detection window by adopting a capacitor, an inductor or an eddy current detection unit arranged on a presser foot or a needle plate, determining the actual positions of the two reference stitch groups, calculating translation deviation and rotation deviation, sewing after transforming the overall coordinates of the track in the pocket cloth assembling stage, and forbidding execution and giving an alarm if the coordinates are not detected or exceed a threshold value. According to the method, alignment reset and fool-proof control in the shielding state are achieved, mistaken sewing and mistaken cutting are reduced, and consistency is improved.

Description

Technical Field

[0001] This application relates to the field of fabric sewing technology, and in particular to a method for detecting and sewing multi-layer fabrics. Background Technology

[0002] Fitted pockets (pockets / stitched pockets) are a typical type of layered sewn pocket structure. Their processing usually involves first shaping the pocket opening on the layer of the garment fabric and reinforcing lining (for example, sewing two parallel stitches extending along the length of the pocket opening to form the opening). After the fitted edge is turned up and shaped, the pocket lining or other materials are covered on the inside of the garment for subsequent assembly and sewing, thus forming the external pocket opening and the internal pocket cavity.

[0003] Existing technologies mostly use clamps / templates in conjunction with preset sewing tracks to complete bag opening forming and bag fabric assembly. In terms of alignment, positioning is usually based on the nominal reference of the clamp or the exposed edge of the bag fabric. Some equipment is supplemented by photoelectric / vision detection of visible edges, ends or indicator marks to correct the starting position or local parameters before completing the end reinforcement line and sealing line sewing.

[0004] In the layered sewing process of the edge-sealed bag, the real process reference formed in the bag opening forming stage is obscured after the bag fabric is covered. Existing alignment methods that rely on the nominal reference of the fixture or visible features are difficult to obtain the position and posture deviation of the real reference in the covered state. Therefore, it is impossible to reliably reset the coordinates of the sewing / cutting trajectory of the subsequent assembly and sewing, making it difficult for subsequent processes to stably maintain the preset geometric relationship with the bag opening structure. Summary of the Invention

[0005] Therefore, it is necessary to propose a multi-layer fabric inspection and sewing method that can solve the above-mentioned technical problems.

[0006] A multi-layer fabric inspection and sewing method, applied to the layered processing of suit patch pockets, includes the following steps: Clamp and position the garment fabric, reinforcing lining, and edge strips to complete the bag opening and form the bag opening and both ends; In the seam allowance area subsequently covered by the bag fabric, a reference stitch group is sewn using a detectable reference thread; A first reference stitch group consisting of two short straight backstitches is sewn at the left end of the bag opening, and a second reference stitch group consisting of three short straight backstitches is sewn at the right end of the bag opening. The geometric center of each reference stitch group is theoretically offset relative to the corresponding endpoint along the length of the bag opening and in its perpendicular direction. Cover the reference stitch group with a lining bag; With the bag cover in the state, the capacitance detection unit, inductance detection unit or eddy current detection unit set on the presser foot or needle plate is used to scan and sample within the preset detection window, and the actual position of the two reference stitch groups is determined according to the two-segment back needle characteristics and the three-segment back needle characteristics, respectively. The translation and rotation deviations are calculated based on the actual position and theoretical offset. Based on this, the overall coordinate transformation of the sewing trajectory or cutting trajectory in the bag assembly stage is performed before bag assembly and sewing. If no two reference stitch groups are detected or the deviation exceeds a preset threshold, bag assembly sewing is prohibited and an abnormality indication is output.

[0007] In at least one embodiment of this application, detecting the reference stitch group of the reference thread sewing includes the following steps: When the bag is covered, the non-visual detection unit at the pressure foot or needle plate generates relative displacement with the workpiece and forms a scanning trajectory. Detection signals are continuously acquired along the scanning trajectory to form a detection signal sequence; Baseline elimination processing is performed on the detected signal sequence and a set of candidate peak points is extracted.

[0008] In at least one embodiment of this application, determining the actual positions of the two reference stitches specifically includes the following steps: The candidate peak points are clustered according to the peak spacing to form several peak clusters; Each peak cluster is mapped to a short straight needle stitch detection response, and the cluster center is obtained. The number of peak clusters is counted and segment matching is performed. When there are two peak clusters, it is determined as the first reference stitch group and its actual position is determined by the geometric center of the two cluster centers. When there are three peak clusters, it is determined as the second reference stitch group and its actual position is determined by the geometric center of the three cluster centers.

[0009] In at least one embodiment of this application, determining the actual positions of the two reference stitches further includes the following steps: Calculate the recognition confidence of the first reference stitch group and the second reference stitch group, wherein the recognition confidence is obtained at least based on the peak cluster number matching result and the consistency of the peak cluster spacing; When the identification confidence level is lower than the preset confidence threshold, the scanning parameters are changed and rescanning is performed to reacquire the detection signal sequence; If the rescan sampling still fails to meet the segment number matching or is still below the preset information threshold, it is determined that the corresponding reference stitch group has not been detected.

[0010] In at least one embodiment of this application, sewing the reference stitch set specifically includes the following steps: Select a detectable baseline cable and match it with a non-visual inspection method; When sewing the reference stitch group, control the stitch to sew in the forward direction along the preset straight line to form a short straight stitch segment, and then backstitch along the same straight line direction to form a backstitch segment to form a short straight backstitch. After lifting the needle and moving it to the next position, repeat the forward sewing and backstitching to form the next short straight backstitch stitch. Repeat twice at the left end of the bag opening to form the first reference stitch group; Repeat three times at the right end of the bag opening to form the second reference stitch group.

[0011] In at least one embodiment of this application, forming a reference stitch group at the bag opening specifically includes the following steps: Establish the theoretical coordinates of the bag opening endpoint in the equipment coordinate system; The geometric center theoretical coordinates of each reference stitch group are generated based on the endpoint theoretical coordinates. The geometric center theoretical coordinates are determined by a first theoretical offset along the length direction of the bag opening and a second theoretical offset perpendicular to the length direction of the bag opening. When sewing the first reference stitch group and the second reference stitch group, the corresponding geometric center theoretical coordinates are used as the center of the needle drop area, and short straight backstitches with two or three segments are constructed within the needle drop area.

[0012] In at least one embodiment of this application, the construction of the first reference stitch group and the second reference stitch group specifically includes the following steps: To enhance direction discrimination, inter-segment sequence features are set for the first reference stitch group and the second reference stitch group. The inter-segment sequence features include setting the segment spacing of adjacent short straight backstitches to at least two different spacing levels. When identifying the first reference stitch group and the second reference stitch group, segment number matching and inter-segment sequence matching are performed simultaneously; When the segment number matches but the inter-segment sequence does not match, it is determined as invalid identification and treated as undetected.

[0013] In at least one embodiment of this application, determining the actual position of the two reference stitch groups specifically includes the following steps: The translational deviation is calculated based on the actual positions of the first and second reference stitch groups and their respective theoretical coordinates of geometric centers. The rotational deviation is calculated based on the actual connecting direction of the two reference stitch groups and the theoretical connecting direction of the two reference stitch groups. The sewing or cutting trajectory during the bag assembly stage is represented as a set of trajectory points; For each trajectory point in the trajectory point set, rotation compensation is performed first, followed by translation compensation to complete the overall coordinate transformation.

[0014] In at least one embodiment of this application, the global coordinate transformation specifically includes the following steps: The endpoint reinforcement line trace point set and the bag sealing line trace point set in the bag assembly stage are respectively used as the trajectory point set to be transformed; The same rotation and translation compensations are applied to the endpoint reinforcement line trajectory point set and the sealing bag line trajectory point set; When the bag fabric assembly stage includes a cutting process, the same global coordinate transformation as the sewing trajectory is applied to the set of cutting trajectory points.

[0015] In at least one embodiment of this application, the overall transformation conditions specifically include the following steps: Before performing bag fabric assembly and sewing, determine whether the first reference stitch group and the second reference stitch group are both detected and determine whether the recognition confidence level meets the preset conditions. When the detection and confidence conditions are met, determine whether both translational and rotational deviations are within preset thresholds. The assembly and sewing of the bag fabric after global coordinate transformation is allowed when the threshold conditions are met. If the detection conditions, confidence conditions, or threshold conditions are not met, the bag assembly and sewing process will be prohibited, an abnormality indication will be output, and a rescan sampling or re-clamping and positioning will be triggered before another detection and judgment is performed.

[0016] The multi-layer fabric inspection and sewing method of this embodiment will have at least the following beneficial effects: The multi-layer fabric detection sewing method described above uses a detectable reference thread to sew a reference stitch group in the seam area subsequently covered by the bag fabric. Reference stitch groups with two-segment backstitch characteristics and three-segment backstitch characteristics are set at the left and right ends of the bag opening, respectively, with preset theoretical offsets. This allows the actual positions of the two reference stitch groups to be scanned and sampled within a preset detection window by a capacitance detection unit, inductance detection unit, or eddy current detection unit set on the presser foot or needle plate even after the bag fabric is covered. Then, the translational and rotational deviations are calculated based on the actual positions and theoretical offsets, and the sewing trajectory or cutting trajectory of the bag fabric assembly stage is transformed into overall coordinates before assembly sewing is performed. At the same time, execution is prohibited and abnormal indications are implemented when no detection is found or the deviation exceeds the limit. This achieves reliable alignment and error prevention control and reduces the risk of mis-sewing in layered and covered scenarios. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] in: Figure 1 This is a flowchart of the multi-layer fabric sewing inspection method shown in this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Please see Figure 1 This application provides a multi-layer fabric inspection and sewing method, applied to the layered processing of suit patch pockets, including the following steps: S10: Clamp and position the garment fabric, reinforcing lining, and edge strips to complete the bag opening and form the bag opening and both ends.

[0021] To ensure a clear reference for subsequent detection, deviation calculation, and trajectory reset under covered conditions, in one specific embodiment, the multi-layered fabric involved in bag opening formation is first clamped and positioned to complete the bag opening formation, thereby forming the bag opening and end points that can be used to establish theoretical biases and calculate deviations. The garment fabric serves as the outer fabric of the edge-sealed bag, providing the visual carrier for the bag opening; the reinforcing liner is placed on the inner side of the garment fabric and overlaps with the bag opening area to improve the tensile and deformation resistance of the bag opening area, making the geometric shape of the formed bag opening more stable and reducing rebound deformation during handling, loosening, or subsequent covering of the bag fabric; the edge-sealing strip is laid on the predetermined bag opening area of ​​the garment fabric and, together with the garment fabric and reinforcing liner, participates in the formation of the bag opening edge, constituting the edge-sealed appearance of the bag and defining the structural boundary of the bag opening area. These three elements form a layered object in the bag opening area, and their layering relationship ensures that the bag opening formation result satisfies both appearance and structural support, providing a foundation for subsequently establishing theoretical biases using the end points as references.

[0022] Furthermore, to achieve clamping and positioning, a clamping and positioning mechanism is provided in one specific embodiment. This mechanism applies clamping force to the garment fabric, reinforcing lining, and edge strip and restricts their relative slippage. Specifically, the clamping and positioning mechanism includes a support portion and a pressing portion. The support portion provides a flat support surface to support the garment fabric and reinforcing lining, while the pressing portion presses the stacked objects in a direction perpendicular to the support surface to form a clamp. The clamping and positioning mechanism may also include a positioning reference portion for aligning with a predetermined edge of the garment fabric or edge strip, thereby locking the nominal position and nominal direction of the bag opening area during clamping. Through the clamping and limiting of the clamping and positioning mechanism, the instantaneous displacement caused by fabric feeding traction, presser foot action, or material elasticity during bag opening formation is suppressed, reducing fluctuations in the bag opening and end point formation positions. This facilitates maintaining consistency of the theoretical offset established based on the end points between different workpieces.

[0023] It is understood that the aforementioned positioning mechanisms are existing positioning mechanisms, and will not be elaborated upon further here.

[0024] S20: In the seam allowance area subsequently covered by the pocket fabric, a reference stitch group is sewn using a detectable reference thread.

[0025] After completing the bag opening and forming the bag opening and end points, to address the problem of "the true reference point being obscured and invisible in the first stage after the bag fabric is covered" during the layered processing of the edge-sealed bag, in a specific embodiment, a reference stitch group is sewn using detectable reference thread in the seam allowance area subsequently covered by the bag fabric. This allows the position information of the reference stitch group to still be obtained by subsequent non-visual inspection methods after the bag fabric is covered, thereby providing a traceable reference source for the calculation of subsequent translational and rotational deviations and the overall coordinate transformation of the trajectory during the bag fabric assembly stage. The seam allowance area refers to the area located inside the edge-sealing structure after the bag opening is formed and will be covered by the bag fabric during bag fabric assembly. This area is not exposed to the appearance side in the finished product state. Therefore, setting the reference stitch group in this area can establish a process reference without affecting the appearance of the edge-sealed bag. It should be noted that the positional relationship of arranging the reference stitch group in the area "subsequently covered by the bag fabric" has a clear process significance, that is, the reference originates from the bag opening forming stage and will be obscured during the bag fabric assembly stage, thus directly corresponding to the alignment and repositioning problem under obscuration conditions that this application aims to solve.

[0026] Furthermore, the detectable reference thread refers to a thread that, after being sewn into stitches, can generate a distinguishable detection response by a capacitance detection unit, an inductance detection unit, or an eddy current detection unit when the fabric is covered. Specifically, in one embodiment, the detectable reference thread can be at least one of conductive yarn, metal fiber yarn, or magnetically responsive fiber yarn, making the reference stitch group have a detectable difference in electrical or electromagnetic response relative to the surrounding ordinary stitches or fabric materials. By selecting a detectable reference thread, even if the fabric is covered over the reference stitch group, the detection unit can still obtain the detection signal change corresponding to the reference stitch group by scanning and sampling within a preset detection window, thereby achieving the detectability of the "hidden reference". It should be noted that the "detectability" here does not rely on visual comparison, but on the difference in capacitance, inductance, or eddy current response between the reference thread and the detection method, thus adapting to the invisible state caused by the fabric covering.

[0027] In a specific embodiment, during the operation, after the bag opening is formed and the stacked object is still in a clamped and positioned state, the detectable reference thread is selected as the sewing thread, and the sewing device is driven to perform a sewing action within the seam allowance area to form a reference stitch group. The sewing action can employ a combination of straight sewing and backstitching to generate a stitch structure with a predetermined shape within the seam allowance area, thereby providing a basis for subsequent feature recognition and position determination within the detection window. Since the seam allowance area is located inside the edge-fitting structure, the reference stitch group is covered after the bag fabric is subsequently covered without affecting the appearance, but it still retains its relative geometric relationship in the device coordinate system, allowing for subsequent comparison between the detected actual position and the preset theoretical offset to output deviation parameters.

[0028] Specifically, the process of inspecting the reference thread sewing reference stitch group includes the following steps: When the bag is covered, the non-visual detection unit at the pressure foot or needle plate generates relative displacement with the workpiece and forms a scanning trajectory. Detection signals are continuously acquired along the scanning trajectory to form a detection signal sequence; Baseline elimination processing is performed on the detected signal sequence and a set of candidate peak points is extracted.

[0029] After the reference stitch group in the seam allowance area is formed and the pocket fabric is covered, in order to ensure that the covered reference stitch group can still be stably and repeatably positioned, in a specific embodiment, a non-visual detection unit set at the presser foot or needle plate is used to scan and sample the preset detection window, and then performs relative displacement scanning, detection signal sequence construction, baseline elimination and candidate peak extraction in sequence.

[0030] Specifically, the non-visual detection unit at the pressure foot or needle plate is first driven to generate relative displacement with the workpiece within a preset detection window and form a scanning trajectory. The role of this relative displacement is to convert the spatial distribution of the "covered reference needle stitch group" into a "time-sequential sampling process along the scanning trajectory", so that the detection unit can obtain the corresponding capacitance, inductance or eddy current response changes at different sampling positions. Furthermore, detection signals are continuously acquired along the scanning trajectory to form a detection signal sequence. The detection signal sequence is used to characterize the response intensity of the detection unit as the position changes during the scanning process, so that the actual position of the reference needle group in the detection window can be deduced from the waveform characteristics of the sequence, avoiding accidental misjudgment caused by relying solely on single-point sampling. Furthermore, baseline elimination processing is performed on the detection signal sequence and a candidate peak point set is extracted. Baseline elimination is used to remove background components caused by fluctuations in bag thickness, differences in material background, zero drift of detection units, or slow trend changes, so that the local abrupt response corresponding to the reference stitch group is more prominent in the sequence, thereby retaining peak information that is closer to the "true response of the reference stitch group" in the candidate peak point set and suppressing the interference of background noise on positioning.

[0031] It should be noted that the aforementioned scanning trajectory, continuous sampling, baseline elimination, and peak extraction constitute a derivation chain from "physical response under occlusion" to "candidate feature points that can be used for positioning." Its direct benefit lies in improving the signal-to-noise ratio and repeatability of detection under covered conditions, providing a stable data foundation for subsequently determining the actual positions of the two reference stitch groups based on two-segment and three-segment backstitch features. This improves the reliability of translational and rotational deviation calculations and reduces the risk of false resets due to false detections. The above process is particularly suitable for automated or semi-automated scenarios in the layered processing of suit patch pockets. For example, even when the pocket fabric is covered and no positioning marks are visible on the exterior, it is still necessary to complete the alignment reset and access control judgment at the workstation before assembly and sewing, thereby achieving stable alignment and mistake-proof control under occlusion conditions.

[0032] Furthermore, determining the actual positions of the two reference stitches specifically includes the following steps: The candidate peak points are clustered according to the peak spacing to form several peak clusters; Each peak cluster is mapped to a short straight needle stitch detection response, and the cluster center is obtained. The number of peak clusters is counted and segment matching is performed. When there are two peak clusters, it is determined as the first reference stitch group and its actual position is determined by the geometric center of the two cluster centers. When there are three peak clusters, it is determined as the second reference stitch group and its actual position is determined by the geometric center of the three cluster centers.

[0033] After obtaining the candidate peak point set, in order to deduce the "actual position of the two reference stitch groups" under the condition that the bag cover is covered and the reference stitch group is not visible, in a specific embodiment, a recognition process based on peak spacing and segment matching is adopted.

[0034] Specifically, the candidate peak point set is clustered according to the peak spacing to form several peak clusters. Its function is to merge adjacent or related peaks generated by the same short straight needle trace during the scanning process into the same response unit, thereby transforming the originally discrete peak point set that may be disturbed by noise into a smaller and more stable peak cluster set, reducing the interference of occasional peaks on the recognition results. Furthermore, each peak cluster is mapped to the detection response of a short straight backstitch and the cluster center is obtained. The cluster center is used to characterize the representative position of the short straight backstitch within the detection window, so that subsequent steps do not need to rely on the precise position of each peak point, but instead use the cluster center as the position description of the "segment", thereby improving the robustness and repeatability of the positioning. Furthermore, the number of peak clusters is counted and segment matching is performed. When there are two peak clusters, it is determined to be the first reference stitch group, and its actual position is determined by the geometric center of the two cluster centers. When there are three peak clusters, it is determined to be the second reference stitch group, and its actual position is determined by the geometric center of the three cluster centers. The role of segment matching is to use the difference in the number of segments between the first and second reference stitch groups to distinguish the left and right ends and to make directional references. In this way, even in the coverage state, it is still clear which group has two segments and which group has three segments, avoiding confusion between the left and right ends or directions, which would lead to distortion in subsequent deviation calculations. The role of using the geometric center of the cluster center as the actual position is to integrate the positions of the responses of each segment in the same reference stitch group into a stable representative point, so that this representative point can correspond one-to-one with the preset theoretical offset, thereby providing a clear input for the subsequent calculation of translational and rotational deviations.

[0035] It should be noted that the above-described derivation chain, from the candidate peak point set to the peak cluster, then to the cluster center, and finally to segment matching and geometric center positioning, transforms the recognition result from "signal waveform characteristics" into "the actual position that can be used for coordinate calculation" in a closed loop. Its beneficial effect is to improve the reliability of determining the position of the reference stitch group under covered conditions, thereby improving the accuracy of the overall trajectory coordinate transformation and reducing the risk of mis-sewing or mis-cutting caused by mis-reset. This process is particularly suitable for workstations in the layered processing of edge-sealed bags where alignment and resetting are still required after the bag fabric is covered. Examples include automated equipment or semi-automatic tooling scenarios where the bag fabric is covered and not visible from the outside, but automatic positioning and access control judgment are still required before assembly and sewing.

[0036] Furthermore, determining the actual positions of the two reference stitches includes the following steps: Calculate the recognition confidence of the first reference stitch group and the second reference stitch group, wherein the recognition confidence is obtained at least based on the peak cluster number matching result and the consistency of the peak cluster spacing; When the identification confidence level is lower than the preset confidence threshold, the scanning parameters are changed and rescanning is performed to reacquire the detection signal sequence; If the rescan sampling still fails to meet the segment number matching or is still below the preset information threshold, it is determined that the corresponding reference stitch group has not been detected.

[0037] After obtaining the candidate identification results of the first and second reference stitch groups through peak spacing clustering and segment number matching, in order to avoid false detection, missed detection or left and right end confusion caused by material background fluctuations, local wrinkles, changes in holding force or electromagnetic environmental disturbances under bag cover conditions, a specific embodiment further introduces an identification confidence assessment and rescanning mechanism to form a closed-loop judgment link from "initial identification" to "credible confirmation" and then to "non-detection judgment".

[0038] Specifically, the recognition confidence of the first reference stitch group and the second reference stitch group is calculated. The recognition confidence is based at least on the peak cluster number matching result and the peak cluster spacing consistency. The peak cluster number matching result is used to characterize whether the candidate result meets the segment number constraint of the two-segment backstitch feature or the three-segment backstitch feature. The peak cluster spacing consistency is used to characterize whether the relative spacing of each segment response within the same reference stitch group meets the structural stability expectation of the reference stitch group. The combination of the two can identify the situation of "correct segment number but abnormal spacing" as a low confidence state, thereby suppressing the pseudo two-segment and pseudo three-segment recognition results caused by noise peaks or occasional responses. Furthermore, when the recognition confidence level is lower than the preset confidence threshold, the scanning parameters are changed and rescanning sampling is performed to reacquire the detection signal sequence. The purpose of changing the scanning parameters is to adjust the relative displacement scanning conditions so that the detection unit can obtain a clearer response difference in the coverage state, thereby improving the peak distinguishability of the detection signal sequence corresponding to the reference needle group. The purpose of rescanning sampling is to regenerate the detection signal sequence with new sampling conditions and perform baseline elimination, peak extraction, clustering and segment matching again, so that the recognition conclusion is transformed from a single result into a repeatable and verifiable result. Furthermore, when the rescan sampling still fails to meet the segment matching or is still below the preset confidence threshold, it is determined that the corresponding reference stitch group has not been detected. Its function is to clearly classify the "unreliable identification result" into the undetected state, so as to avoid continuing to output the wrong actual position and enter the subsequent translational deviation and rotational deviation calculation and trajectory overall coordinate transformation when the identification is unreliable, thereby reducing the risk of incorrect stitching or incorrect cutting caused by incorrect reset being solidified.

[0039] It should be noted that the identification confidence level and rescanning mechanism elevate the baseline positioning under coverage conditions from "whether identification exists" to a judgment system of "whether identification is reliable." Rescanning provides a second chance for reliable identification, and ultimately, a non-detection determination provides a clear trigger condition for subsequent access control, thus logically forming a closed loop with the subsequent "no detection or exceeding threshold prohibition" error-proofing step. This mechanism is particularly suitable for the robust identification needs of automated equipment in the layering process of edge-sealed bags during continuous production, facing different fabric batches, different bag fabric coverage flatness, or different layer thicknesses. It can improve the stability and consistency of coverage status detection without adding visible markings.

[0040] S30: Sew a first reference stitch group consisting of two short straight backstitches at the left end of the bag opening, and sew a second reference stitch group consisting of three short straight backstitches at the right end of the bag opening, and pre-set the theoretical offset of the geometric center of each reference stitch group relative to the corresponding endpoint along the length direction of the bag opening and its perpendicular direction. To enable simultaneous left-right differentiation, orientation reference establishment, and pose deviation calculation even when the bag is covered, in one specific embodiment, a first reference stitch group consisting of two short straight backstitch segments is sewn at the left end of the bag opening, and a second reference stitch group consisting of three short straight backstitch segments is sewn at the right end of the bag opening. The geometric center of each reference stitch group is theoretically offset relative to its corresponding endpoint along the length of the bag opening and its perpendicular direction. It should be noted that the difference in the number of segments between the first and second reference stitch groups is not merely a matter of marking presence or absence, but rather serves to form a distinguishable feature set under covered conditions. This allows the non-visual detection unit to make clear classifications based on the "two-segment backstitch feature" and the "three-segment backstitch feature," even when the bag is covered, thus avoiding confusion between the left and right ends. Simultaneously, the parallel setting of the two references allows for the subsequent derivation of rotational deviation based on the relative geometric relationship between the two references, rather than simply obtaining translational deviation from single-point positioning. This forms a logical closed loop with the subsequent requirement for overall coordinate transformation of the sewing or cutting trajectory.

[0041] Specifically, the short straight backstitch refers to first forming a short straight stitch segment by forward sewing in the same straight direction, and then backstitching in the same straight direction to form a backstitch segment, thereby creating a stitch structure with enhanced detectable response in a localized area. The first reference stitch group consists of two short straight backstitch segments, indicating that two short straight backstitch segments are formed sequentially at the left end of the pocket opening; the second reference stitch group consists of three short straight backstitch segments, indicating that three short straight backstitch segments are formed sequentially at the right end of the pocket opening. By setting two and three segments of structural difference at the left and right ends of the pocket opening respectively, the left and right ends can be identified by segment number matching during the coverage state detection, and the identification result can be directly used to determine the "corresponding endpoints" in the subsequent deviation calculation, avoiding incorrect theoretical bias reference due to incorrect endpoint correspondence. Furthermore, the reference needle stitch group uses the "geometric center" as the position representation. This means that the detection response positions formed by each short straight back needle stitch in the detection window of the reference needle stitch group are combined to obtain a center point that can represent the overall position of the group. This allows for a one-to-one correspondence between the center point and the preset theoretical offset, reducing the impact of single-segment response fluctuations on the overall positioning.

[0042] Furthermore, the theoretical offset of the geometric center of each reference stitch group relative to its corresponding endpoint along the length of the bag opening and its perpendicular direction is preset. This means that, using the two endpoints of the bag opening as nominal references, the offset from the geometric center of the reference stitch group to the endpoint along the length of the bag opening is given, and the offset from the geometric center of the reference stitch group to the endpoint along the perpendicular direction is given, so that the reference stitch group at each end has a definite nominal coordinate. The purpose of this theoretical offset is to transform "where the reference stitch group should appear" into a calculable theoretical position, so that the actual position detected in the bag cover state can be directly compared with the theoretical position, thereby deriving the translational deviation. At the same time, since there are reference stitch groups at both ends, the theoretical offset also provides a nominal reference for the direction of the theoretical connection between the two ends, so that the rotational deviation can be derived by comparing the actual connection direction between the two ends with the theoretical connection direction, thereby meeting the requirement of overall coordinate transformation of the trajectory during the bag assembly stage.

[0043] In summary, by forming reference stitch groups with different numbers of segments at the left and right ends of the bag opening and presetting the theoretical offset of their relative endpoints, a distinguishable, locatable, and calculable hidden process reference can be provided even when the reference is invisible due to the bag fabric covering. This allows subsequent coverage state detection to output the actual positions corresponding to the left and right ends, and further provides the necessary input for solving translational and rotational deviations and the overall trajectory coordinate transformation. Thus, a logical closed loop is formed in the technical solution from "reference construction" to "coverage detection" and then to "deviation calculation and trajectory reset". This step is suitable for application scenarios of layered processing of edge-sealed bags, such as when bag opening forming and bag fabric assembly are performed by different stations, and when no visible positioning information can be obtained from the appearance side after the bag fabric is covered, but automatic alignment and reset are still required.

[0044] Furthermore, the process of sewing the reference stitch set specifically includes the following steps: Select a detectable baseline cable and match it with a non-visual inspection method; When sewing the reference stitch group, control the stitch to sew in the forward direction along the preset straight line to form a short straight stitch segment, and then backstitch along the same straight line direction to form a backstitch segment to form a short straight backstitch. After lifting the needle and moving it to the next position, repeat the forward sewing and backstitching to form the next short straight backstitch stitch. Repeat twice at the left end of the bag opening to form the first reference stitch group; Repeat three times at the right end of the bag opening to form the second reference stitch group.

[0045] To ensure that the first and second reference stitch groups can generate stable and distinguishable non-visual detection responses when covered by the pocket fabric, and can be reliably identified by the subsequent segment matching process, in a specific embodiment, the sewing of the reference stitch groups is achieved through an action chain of "reference thread selection - short straight backstitch construction - inter-segment shifting and repetition - formation of two segments on the left end - formation of three segments on the right end", thereby establishing detectable features at both the material properties and stitch morphology levels. Specifically, selecting a detectable reference thread and matching it with a non-visual inspection method ensures that the stitches still exhibit identifiable response differences in capacitance, inductance, or eddy current detection even after the fabric is covered. Furthermore, when sewing the reference stitch group, the stitches are controlled to be sewn forward along a preset straight direction to form a short straight stitch segment, and then backstitched along the same straight direction to form a backstitch segment, thus constituting a short straight backstitch. The preset straight direction defines the geometry of this stitch segment, ensuring a consistent directional response distribution during scanning through the detection window. The forward sewing and backstitch combination... This technique is suitable for creating repeated overlapping lines locally, making the material volume distribution and electrical or electromagnetic response of the stitch more concentrated, thereby increasing the probability of it being captured by scanning sampling in the covered state. Furthermore, after lifting the needle and moving it to the next position, the forward sewing and backstitching are repeated to form the next short straight backstitch stitch. Its function is to expand the single-segment response into a multi-segment response and form a "multi-peak" response structure through the separation of the segment positions. This allows multiple candidate peak points to be extracted from the detection signal sequence and peak clusters to be formed by clustering the peak spacing, thereby providing a data basis for segment number matching.

[0046] It should be noted that repeating the stitch twice at the left end of the bag opening to form the first reference stitch group and repeating it three times at the right end of the bag opening to form the second reference stitch group directly corresponds to the segment matching judgment logic based on the number of peak clusters in the subsequent coverage state. That is, when the number of peak clusters is two, it corresponds to the first reference stitch group, and when the number of peak clusters is three, it corresponds to the second reference stitch group. This achieves the differentiation of the left and right ends and the establishment of direction reference. At the same time, since there are reference stitch groups at both ends, the translational deviation can be calculated based on the actual position and theoretical offset of the references at both ends, and the rotational deviation can be calculated based on the direction difference of the connecting lines at both ends. This forms an input-output closed loop with the subsequent step of performing overall coordinate transformation on the sewing trajectory or cutting trajectory.

[0047] The specific operation process is as follows: In one embodiment, when the bag opening is formed and the stacked objects are in a stable clamping state, the sewing thread is first switched to a detectable reference thread and the corresponding non-visual detection method is selected. Then, a forward sewing is performed along a preset straight line in the seam allowance area at the left end of the bag opening, followed by a backstitch to form the first short straight backstitch. After lifting the needle, it is moved to the next position and forward sewing and backstitch are performed again to form the second short straight backstitch, thus completing the first reference stitch group. Then, three short straight backstitches are continuously formed in the same way in the seam allowance area at the right end of the bag opening, thus completing the second reference stitch group. The above construction method is suitable for application scenarios in the layering processing of edge-sealed bags where visual positioning cannot be used after the bag fabric is covered, such as automatic bag opening forming and bag fabric assembly integrated machines or separate workstation equipment, where automatic positioning and trajectory reset need to be completed by relying on hidden references before assembly and sewing. In summary, by forming a detectable, multi-segment countable reference stitch group through material selection and stitch morphology construction, the reliability of identification under the covering state can be improved and a stable input can be provided for subsequent deviation calculation and access control, thereby improving the consistency of layer processing and reducing the risk of mis-sewing caused by misalignment. Furthermore, forming the reference stitch set at the bag opening specifically includes the following steps: Establish the theoretical coordinates of the bag opening endpoint in the equipment coordinate system; The geometric center theoretical coordinates of each reference stitch group are generated based on the endpoint theoretical coordinates. The geometric center theoretical coordinates are determined by a first theoretical offset along the length direction of the bag opening and a second theoretical offset perpendicular to the length direction of the bag opening. When sewing the first reference stitch group and the second reference stitch group, the corresponding geometric center theoretical coordinates are used as the center of the needle drop area, and short straight backstitches with two or three segments are constructed within the needle drop area.

[0048] To ensure a clear and reproducible reference system for subsequent comparisons of "actual position and theoretical offset," and to guarantee that the nominal positions of the first and second reference stitch groups in the device coordinate system can be consistently invoked, in a specific embodiment, the endpoint theoretical coordinates are established before the reference stitch groups are formed at the bag opening. Then, the geometric center theoretical coordinates are derived from the endpoint theoretical coordinates, and the geometric center theoretical coordinates are used as the center of the needle-dropping area to construct the corresponding number of short straight backstitch stitch segments. This forms a closed-loop link from "endpoint reference" to "reference theoretical position" and then to "needle-dropping implementation." Specifically, establishing the endpoint theoretical coordinates of the bag opening endpoints in the device coordinate system means that after completing the bag opening formation and determining the two endpoints of the bag opening, the two endpoints are used as nominal reference points and assigned theoretical coordinate values ​​in the device coordinate system. This makes the endpoints no longer just geometric concepts, but coordinate references that can be calculated and invoked subsequently. Its function is to unify the nominal geometric results of the bag opening formation stage with the coordinate system used for subsequent detection, calculation, and trajectory reset, avoiding the inaccurate placement of the theoretical offset due to relying solely on empirical positions or clamping nominal positions.

[0049] Furthermore, the theoretical coordinates of the geometric center of each reference stitch group are generated based on the endpoint theoretical coordinates. These theoretical coordinates are determined by a first theoretical offset along the length of the bag opening and a second theoretical offset perpendicular to the length of the bag opening. Specifically, based on the endpoint theoretical coordinates, a first theoretical offset is set along the length of the bag opening to determine the theoretical displacement of the reference stitch group relative to the endpoint in the bag opening direction; simultaneously, a second theoretical offset is set perpendicular to the length of the bag opening to determine the theoretical displacement of the reference stitch group relative to the endpoint in the normal direction. Both offsets together determine the theoretical coordinates of the geometric center of the reference stitch group in the equipment coordinate system. This step quantifies "where the reference stitch group should be sewn" as a target position in the equipment coordinate system, allowing for a direct comparison between the actual position of the reference stitch group detected under bag cover conditions and these theoretical coordinates, thereby deriving the translational deviation. Simultaneously, since reference stitch groups exist at both ends, the theoretical connection direction between the theoretical coordinates of the geometric centers of the left and right ends is also determined, providing a theoretical reference for the subsequent derivation of the rotational deviation, thus logically aligning with the requirements of the subsequent overall coordinate transformation. It should be noted that using the geometric center as the reference point for the theoretical coordinates allows the combined structure of multiple short straight backstitch stitches to be abstracted into a single center point. This ensures that the subsequent definition of "actual position" corresponds to the definition of "theoretical position" at the same level, avoiding inconsistencies in comparison caused by introducing internal structural differences through the reference point of a single stitch.

[0050] Furthermore, when sewing the first and second reference stitch groups, the theoretical coordinates of the corresponding geometric center are used as the center of the needle-dropping area. Within this area, two or three short straight backstitch segments are constructed. This means that after the control system calls the theoretical coordinates of the geometric center, these coordinates are used as the center point of the needle-dropping area. Subsequently, multiple short straight backstitch segments are formed near this center point according to a predetermined inter-segment layout. This ensures that the reference stitch group is formed around this center and that its geometric center is consistent with the theoretical coordinates or has a controllable deviation. Its function is to translate the theoretical coordinates into the actual sewing action, ensuring that the reference stitch group for each workpiece is nominally generated with the same endpoint reference and the same theoretical offset. Therefore, the difference between the actual position obtained by subsequent detection and identification and the theoretical offset mainly reflects the actual pose change of the workpiece after being covered by the pocket fabric, rather than reflecting the randomness of the reference stitch group's own placement.

[0051] The specific operation process is as follows: In one embodiment, after the bag opening is formed, the theoretical coordinates of the two ends of the bag opening are first determined in the equipment coordinate system. Then, the theoretical coordinates of the geometric center of the corresponding reference stitch group are calculated for the left and right ends respectively. After that, the sewing device is driven to move to the center of the needle drop area corresponding to the theoretical coordinates of the geometric center and complete the construction of short straight backstitch. A reference stitch group with two segments is formed at the left end, and a reference stitch group with three segments is formed at the right end. In summary, by establishing the theoretical coordinates of the endpoints and the theoretical coordinates of the geometric center and constraining the center of the needle drop area, a traceable path from the nominal reference to the actual sewing of the reference stitch group is realized. This ensures that subsequent coverage state detection, translation and rotation deviation calculation, and overall trajectory coordinate transformation have a consistent coordinate basis, which is suitable for automated or semi-automated application scenarios of bag opening forming and bag fabric assembly separation processes in the layered processing of edge-sealed bags.

[0052] Furthermore, the construction of the first reference stitch group and the second reference stitch group specifically includes the following steps: To enhance direction discrimination, inter-segment sequence features are set for the first reference stitch group and the second reference stitch group. The inter-segment sequence features include setting the segment spacing of adjacent short straight backstitches to at least two different spacing levels. When identifying the first reference stitch group and the second reference stitch group, segment number matching and inter-segment sequence matching are performed simultaneously; When the segment number matches but the inter-segment sequence does not match, it is determined as invalid identification and treated as undetected.

[0053] To further reduce the risk of false two-segment or false three-segment misjudgments caused by noise peaks, local wrinkles, or changes in material background under bag cover conditions, and to provide stronger direction discrimination capability even when the number of segments is the same or the number of peak clusters accidentally meets the segment condition, in a specific embodiment, inter-segment sequence features are introduced into the construction of the first reference stitch group and the second reference stitch group, and segment number matching and inter-segment sequence matching are combined as the determination condition for effective recognition during the recognition stage. Specifically, inter-segment sequence features are set for the first reference stitch group and the second reference stitch group to enhance direction discrimination. The inter-segment sequence features include setting the segment spacing of adjacent short straight backstitches to at least two different spacing levels. Its function is to expand the reference stitch group from "only relying on the number of segments" to a "segment number plus sequence" encoding form, so that the number of segments in the same reference stitch group is different, and the spacing between adjacent segments presents a preset sequence pattern, thereby forming a more recognizable peak cluster spacing distribution in the detection signal sequence. Furthermore, when identifying the first and second reference stitch groups, segment number matching and inter-segment sequence matching are performed simultaneously. This means that after the candidate peak point set is clustered to form peak clusters and the cluster centers are obtained, it is first determined whether the number of peak clusters meets the segment number condition of two or three segments, and then it is determined whether the spacing relationship between adjacent cluster centers conforms to the preset spacing level sequence, thereby eliminating the situation of "correct quantity but incorrect spacing relationship". Furthermore, when the segment number matching is successful but the inter-segment sequence matching is unsuccessful, it is determined as invalid identification and treated as undetected. Its function is to directly reject candidate results that do not meet the sequence constraints and not output the actual position of the corresponding reference stitch group, so as to avoid bringing the misidentification results into the subsequent translational deviation and rotational deviation calculation and triggering the incorrect overall coordinate transformation, thereby reducing the risk of mis-sewing or mis-cutting caused by mis-reset.

[0054] It should be noted that the introduction of inter-segment sequence features and the aforementioned recognition confidence and rescanning mechanism are logically complementary. The former enhances distinguishability through the structural encoding of the reference stitch group itself, while the latter enhances robustness through the credibility assessment of the recognition process. Together, they make the hidden reference positioning under the coverage state more reliable, and when recognition fails, it can clearly fall into the undetected processing, thus forming a closed loop consistent with the triggering conditions of subsequent access control. The specific operation process is as follows: In a specific embodiment, when sewing each segment of short straight backstitch, the displacement distance between adjacent segments is determined sequentially according to the preset spacing level, so that the first reference stitch group or the second reference stitch group forms a sequence structure with at least two different segment spacings; in the subsequent coverage state detection, in addition to counting the number of peak clusters, the sequence consistency judgment of the peak cluster spacing is also performed. Only when both the number of segments and the sequence are satisfied is the recognition confirmed as valid; otherwise, it is processed as undetected. This structure and recognition method are suitable for application scenarios where the fabric type varies greatly or the flatness of the bag cover fluctuates greatly in the layered processing of edge-attached bags. It can improve the reliability of left and right end and direction discrimination without relying on visual marks, thereby improving the consistency of subsequent trajectory reset and assembly sewing. S40: Cover the bag fabric to cover the reference stitch group.

[0055] After the formation of the reference stitch group within the seam allowance area and the theoretical offset setting of its relative endpoints are completed, in order to proceed to the bag fabric assembly stage of the edge-fitting bag layering process, in a specific embodiment, the action of covering the bag fabric to conceal the reference stitch group is performed. The bag fabric refers to the piece of fabric used to form the bag cavity of the edge-fitting bag, which, during the assembly stage, combines with the inner area of ​​the garment fabric to ultimately form the bag cavity structure. Covering the bag fabric to conceal the reference stitch group means laying the bag fabric inside the seam allowance area of ​​the bag opening, so that the bag fabric adheres to the seam allowance area and the reference stitch group is covered by the bag fabric, thereby physically creating a state where the "reference stitches are concealed and invisible". This positional relationship has clear technological significance. On the one hand, the reference stitch group is located in the seam allowance area subsequently covered by the pocket fabric. After the pocket fabric is covered, the reference stitch group will not appear on the finished product's appearance side, thus avoiding any impact on the appearance of the suit's edge pocket. On the other hand, the reference stitch group is covered after the pocket fabric is covered, which precisely forms the typical layered processing obstruction situation that this application aims to solve. This provides a clear application premise for subsequently scanning, sampling, and locating the reference stitch group through non-visual inspection methods while the pocket fabric is covered.

[0056] In a specific embodiment, during the operation, while maintaining the geometric stability of the bag opening forming area, the bag fabric is moved to the inner area of ​​the bag opening and unfolded, so that the coverage area of ​​the bag fabric at least covers the area where the reference stitch group is located, thereby achieving the covering of the first reference stitch group and the second reference stitch group. Subsequently, the bag fabric can be pressed or temporarily positioned to keep the bag fabric and the seam area in a close fit, so that when scanning and sampling is performed in the preset detection window, the relative distance change between the detection unit and the workpiece can be controlled and the detection signal sequence can be more stable. It should be noted that covering the bag fabric and covering the reference stitch group is not just a natural step in the assembly process. In this application, it plays the role of "creating the covering conditions and verifying the hidden detection capability". That is, by placing the reference under the bag fabric, the subsequent reference positioning does not rely on visual or visible marks, but on the differences in capacitance, inductance or eddy current response of the reference stitch group formed by the detectable reference wire, thereby forming a logical closed loop with the subsequent scanning sampling, candidate peak extraction, cluster matching and deviation calculation.

[0057] In summary, by covering the pocket fabric to conceal the reference stitch group, the assembly requirements for forming the pocket cavity are met, while establishing a layered concealment process without affecting the finished product's appearance. This allows for subsequent detection and positioning of the hidden reference while the pocket fabric is covered, enabling trajectory reset and access control. This improves alignment consistency during layered processing and reduces the risk of mis-sewing. This step is suitable for automated or semi-automated processing scenarios of suit pockets, especially for workstations where visible positioning information is not available after the pocket fabric is covered, but assembly, sewing, or cutting is still required.

[0058] S50: When the bag is covered, the capacitance detection unit, inductance detection unit or eddy current detection unit set on the presser foot or needle plate is used to scan and sample within the preset detection window, and the actual position of the two reference stitch groups is determined according to the two-segment backstitch characteristics and the three-segment backstitch characteristics, respectively.

[0059] After covering the pocket fabric and obscuring the reference stitch group, in order to obtain reference position information that can be used for deviation calculation and trajectory reset even when the reference is not visible, in a specific embodiment, a capacitance detection unit, inductance detection unit, or eddy current detection unit set on the presser foot or needle plate is used to scan and sample within a preset detection window while the pocket fabric is covered. The actual positions of the first reference stitch group and the second reference stitch group are determined based on the characteristics of two-segment backstitch and three-segment backstitch, respectively. It should be noted that the significance of "set on the presser foot or needle plate" is that the presser foot or needle plate is the near-field position of the sewing and cutting execution area. Arranging the detection unit at this location can keep the detection coordinate system consistent with the execution coordinate system of the subsequent sewing or cutting trajectory, reducing the error transmission caused by coordinate system transformation. This makes the subsequent logic of calculating translational and rotational deviations based on actual positions and theoretical offsets and performing overall coordinate transformation more closed.

[0060] Specifically, the capacitance detection unit generates a detection signal by utilizing the difference in capacitance response between the reference stitch group and the surrounding material under covered conditions; the inductance detection unit generates a detection signal by utilizing the difference in inductance response between the reference stitch group and the surrounding material; and the eddy current detection unit generates a detection signal by utilizing the difference in eddy current response between the reference stitch group and the surrounding material. All three units can output detectable response changes corresponding to the reference stitch group under bag cover conditions, thus avoiding reliance on visible features. The preset detection window refers to the scanning area set around the theoretical location of the reference stitch group. Its function is to limit the scanning range to a local area related to the reference stitch group, reducing background interference from scanning irrelevant areas and increasing the sampling density per unit time. This makes the response features corresponding to the reference stitch group more prominent in the detection signal sequence, thereby improving the reliability of subsequent identification.

[0061] In one specific embodiment, the scanning sampling process includes driving the detection unit to generate relative displacement with the workpiece and forming a scanning trajectory, continuously acquiring detection signals along the scanning trajectory to form a detection signal sequence, and then performing baseline elimination processing on the detection signal sequence and extracting a set of candidate peak points, so that the local response peaks corresponding to the reference needle stitch group stand out from the background components. Further, the set of candidate peak points is clustered according to the peak spacing to form several peak clusters, and each peak cluster corresponds to the detection response of a short straight backstitch and the cluster center is obtained, so that multiple short straight backstitch segments correspond to multiple stable response units in the signal domain. Further still, the number of peak clusters is counted and segment matching is performed. When the number of peak clusters is two, the two backstitch segments are determined as the first reference needle stitch group, and the actual position of the first reference needle stitch group is determined by the geometric center of the two cluster centers; when the number of peak clusters is three, the three backstitch segments are determined as the second reference needle stitch group, and the actual position of the second reference needle stitch group is determined by the geometric center of the three cluster centers, thereby achieving left-right differentiation and direction reference establishment in the coverage state. It should be noted that using two-segment and three-segment back needle features to identify the two end references respectively can form a clear classification basis when the references are not visible and only the detection signal is available, thus avoiding confusion between the two end references and causing errors in the subsequent calculation of the correspondence between translational and rotational deviations.

[0062] Furthermore, in one specific embodiment, an identification confidence level can be calculated on the identification result. The identification confidence level is at least based on the consistency between the peak cluster number matching result and the peak cluster spacing. When the identification confidence level is lower than a preset confidence threshold, the scanning parameters are changed and rescanning sampling is performed to reacquire the detection signal sequence. When the rescanning sampling still cannot meet the segment number matching or is still lower than the preset confidence threshold, it is determined that the corresponding reference needle group has not been detected, thereby providing a clear triggering condition for the subsequent access control of "not detected or deviation exceeding the limit prohibits execution".

[0063] Further, determining the actual positions of the two reference stitch sets specifically includes the following steps: The translational deviation is calculated based on the actual positions of the first and second reference stitch groups and their respective theoretical coordinates of geometric centers. The rotational deviation is calculated based on the actual connecting direction of the two reference stitch groups and the theoretical connecting direction of the two reference stitch groups. The sewing or cutting trajectory during the bag assembly stage is represented as a set of trajectory points; For each trajectory point in the trajectory point set, rotation compensation is performed first, followed by translation compensation to complete the overall coordinate transformation.

[0064] After obtaining the actual positions of the first reference stitch group and the second reference stitch group through non-visual detection under the bag cover state, in order to convert the actual positions into a reset trajectory that can be directly executed in the bag assembly stage, in a specific embodiment, the translational deviation is further calculated based on the actual positions of the two references and their respective geometric center theoretical coordinates, and the rotational deviation is calculated based on the direction of the line connecting the two references, and then the overall coordinate transformation is performed on the sewing trajectory or cutting trajectory in the bag assembly stage.

[0065] Specifically, the calculation of translational deviation is based on "the difference between the actual position of the same reference in the equipment coordinate system and its theoretical geometric center coordinates". That is, a correspondence is established between the first reference stitch group and the second reference stitch group, and their actual positions are compared with their respective theoretical geometric center coordinates to obtain the displacement difference along two orthogonal directions of the equipment coordinate system. This displacement difference reflects the overall offset of the workpiece relative to the nominal position after the bag cloth is covered. Its beneficial effect is that the starting position, sealing path or cutting path of the subsequent bag cloth assembly stage can be corrected synchronously with the workpiece offset, avoiding assembly offset caused by still executing according to the nominal trajectory.

[0066] Furthermore, the calculation of rotational deviation is based on the difference between the actual connecting line direction of the two reference stitch groups and the theoretical connecting line direction. Specifically, the actual positions of the first and second reference stitch groups are used to construct the actual connecting line, and the theoretical coordinates of their geometric centers are used to construct the theoretical connecting line. The rotational deviation is obtained by comparing the directions of the two connecting lines. This rotational deviation reflects the change in the workpiece's rotation angle relative to the nominal direction. Its beneficial effect is that it can compensate for the overall directional deviation caused by slight clamping deviations, layered traction, or the pulling of the bag fabric covering, avoiding defects such as tilted end reinforcement positions or skewed sealing stitches. It should be noted that using two-end references to calculate the rotational deviation ensures that the directional information comes from the geometric relationship between two points rather than a single-point inference. This aligns with the aforementioned logic of using "two-segment backstitch features and three-segment backstitch features for left-right end differentiation and directional reference establishment," ensuring that the correspondence of the deviation solution is clear and traceable.

[0067] Furthermore, in one specific embodiment, in order to facilitate the overall coordinate transformation of the sewing trajectory or cutting trajectory, the sewing trajectory or cutting trajectory in the bag assembly stage can be represented as a set of trajectory points arranged in the execution order, so that the path is transformed from a process description into a computable object, thereby enabling a consistent rigid body transformation to be applied to the entire path without changing the shape of the path.

[0068] Furthermore, rotation compensation is performed on each trajectory point in the trajectory point set first, followed by translation compensation to complete the overall coordinate transformation. The order of rotation before translation is used to ensure that the rotation compensation is performed around a consistent nominal reference relationship. Then, the result after rotation is translated as a whole to be consistent with the actual position of the workpiece. This ensures that the sewing trajectory or cutting trajectory after reset maintains a preset geometric correspondence with the end point of the bag opening and the theoretical offset, reducing the path accumulation error caused by improper compensation order.

[0069] The overall coordinate transformation includes the following steps: The endpoint reinforcement line trace point set and the bag sealing line trace point set in the bag assembly stage are respectively used as the trajectory point set to be transformed; The same rotation and translation compensations are applied to the endpoint reinforcement line trajectory point set and the sealing bag line trajectory point set; When the bag fabric assembly stage includes a cutting process, the same global coordinate transformation as the sewing trajectory is applied to the set of cutting trajectory points.

[0070] In one specific embodiment, the reason why the overall coordinate transformation needs to be further refined into "separate point sets, same-parameter compensation, and unified reset" for different process paths is that the bag assembly stage usually contains multiple path types that are related to each other but executed at different positions. If only one path is reset while the other paths are still executed according to the nominal coordinates, or if different compensation parameters are used for different paths, the geometric correspondence that should be maintained within the bag assembly stage will be destroyed, thereby causing relative misalignment between the end reinforcement and the sealing stitch, and between sewing and cutting. Based on this, the endpoint reinforcement stitch trajectory point set and the sealing stitch trajectory point set during the bag assembly stage are respectively used as trajectory point sets to be transformed. The endpoint reinforcement stitch trajectory point set corresponds to the reinforcement path near the bag opening endpoint, and the sealing stitch trajectory point set corresponds to the path of the bag lining sealing to form the bag cavity. Although the path shapes and coverage areas of the two are different, they must maintain a consistent positional relationship relative to the bag opening endpoint. Therefore, the same rotation compensation and translation compensation are applied to the endpoint reinforcement stitch trajectory point set and the sealing stitch trajectory point set, so that the two types of paths are synchronously reset under the action of the same translation deviation and rotation deviation, thereby ensuring that the nominal correspondence between the endpoint reinforcement landing point, the direction of the sealing stitch, the bag opening, and the endpoint is not destroyed.

[0071] Furthermore, when the bag assembly stage includes a cutting process, the cutting trajectory point set and the sewing trajectory also need to be reset based on the same positional deviation. This is because the cutting position and the subsequent stitch position have a process-related coordination relationship. If the cutting trajectory is not adjusted synchronously with the workpiece position, even if the sewing trajectory has been reset, the problem of misalignment between the cut and the stitch may still occur. Therefore, the same overall coordinate transformation as the sewing trajectory is applied to the cutting trajectory point set, so that cutting and sewing change in tandem under the same coordinate reset result. In summary, by using the same set of rotation compensation and translation compensation parameters for the overall coordinate transformation of the endpoint reinforcement stitch trajectory point set, the sealing stitch trajectory point set, and the optional cutting trajectory point set, the error introduced by the positional deviation after covering can be uniformly eliminated, avoiding relative drift between different process paths, thereby improving the alignment consistency in the bag assembly stage and reducing the risks of misaligned endpoints, skewed sealing, and misaligned cuts.

[0072] Furthermore, the overall transformation conditions specifically include the following steps: Before performing bag fabric assembly and sewing, determine whether the first reference stitch group and the second reference stitch group are both detected and determine whether the recognition confidence level meets the preset conditions. When the detection and confidence conditions are met, determine whether both translational and rotational deviations are within preset thresholds. The assembly and sewing of the bag fabric after global coordinate transformation is allowed when the threshold conditions are met. If the detection conditions, confidence conditions, or threshold conditions are not met, the bag assembly and sewing process will be prohibited, an abnormality indication will be output, and a rescan sampling or re-clamping and positioning will be triggered before another detection and judgment is performed.

[0073] In one specific embodiment, to avoid perpetuating errors into the finished product by continuing bag fabric assembly and sewing even when the reference identification is unreliable or the pose deviation exceeds the limit, an overall transformation condition is set as an access control decision link before the overall coordinate transformation is completed, so that "whether the detection result is reliable", "whether the deviation is compensable", and "whether to allow entry for assembly execution" form a closed-loop control. Specifically, before performing bag fabric assembly and sewing, it is first determined whether both the first reference stitch group and the second reference stitch group have been detected and whether the recognition confidence meets the preset conditions. The derivation logic is as follows: the calculation of translational deviation and rotational deviation depends on the actual position input of the two references. If either reference is not detected, the correspondence between the left and right ends and the direction reference cannot be established, and the deviation calculation lacks the necessary input. Even if both references are detected, if the recognition confidence is insufficient, the output actual position may originate from noise peaks or pseudo-responses. Continuing to calculate the deviation and performing trajectory reset will amplify the error and cause the assembly path to be incorrectly "reset" to an incorrect position. Therefore, it is necessary to use detection and confidence as the first threshold to filter out the situation of "no input" or "unreliable input".

[0074] Furthermore, when the detection and confidence conditions are met, it is determined whether both translational and rotational deviations are within preset thresholds. The reasoning behind this is that the overall coordinate transformation is a compensation and reset of the assembly trajectory. When the deviation is too large, it indicates that the actual position of the workpiece has significantly deviated from the nominal clamping state. Continuing to rely on trajectory compensation may cause the assembly path to cross into non-target areas, resulting in risks such as incorrect endpoint reinforcement placement, bag sealing stitches exceeding boundaries, or cutting position deviations. Therefore, a threshold is used to constrain the compensable range, keeping the compensation and reset within the error window allowed by the process. Furthermore, when the threshold conditions are met, the assembly and sewing of the bag fabric after the overall coordinate transformation is allowed. Its function is to convert the "reliable identification result" and the "controllable deviation range" into explicit execution permission, ensuring that the assembly stage only enters actual sewing when the alignment conditions are met, thereby improving processing consistency.

[0075] Furthermore, if the detection conditions, confidence level conditions, or threshold conditions are not met, the bag assembly and sewing process is prohibited, an anomaly indication is output, and a rescan sampling or re-clamping and positioning is triggered before another detection and judgment is performed. The reasoning behind this is as follows: when the failure is due to unstable identification, rescan sampling is prioritized to reacquire the detection signal sequence in order to restore reliable identification under the same clamping state; when the failure is due to excessive deviation, simple rescanning cannot eliminate the true pose deviation, so the nominal clamping state is restored by re-clamping and positioning before the detection and judgment are performed, so as to re-establish the effective correspondence between the endpoint reference and the theoretical offset. It should be noted that the above-mentioned "prohibition of execution - anomaly indication - rescanning or re-clamping - re-judgment" chain ensures that the system will not directly enter the assembly execution when the detection fails or exceeds the tolerance, but will return to the link that can restore the alignment conditions, thus forming a closed-loop mistake-proof control together with the aforementioned coverage state detection, deviation calculation, and trajectory reset. In summary, by setting access control conditions based on detection and identification confidence levels and deviation thresholds before assembly and sewing, and triggering rescanning or repositioning before judgment in case of failure, the risk of mis-sewing under false detection, false omission, or out-of-tolerance conditions can be reduced, and the reliability and yield of the layered processing of edge-sealing bags can be improved. This is especially suitable for application scenarios in rhythmic production that require automatic determination of whether to allow entry into assembly and sewing.

[0076] S60: Calculate translation and rotation deviations based on actual position and theoretical offset, and then perform overall coordinate transformation on the sewing or cutting trajectory during the bag assembly stage before performing bag assembly sewing.

[0077] S70: When no two reference stitch groups are detected or the deviation exceeds the preset threshold, the bag fabric assembly sewing is prohibited and an abnormality indication is output.

[0078] In one specific embodiment, after determining the actual positions of the first and second reference stitch groups under the bag cover state, the actual positions are compared with the corresponding theoretical offsets to calculate translational and rotational deviations. The translational deviation characterizes the overall offset of the workpiece relative to its nominal position, and the rotational deviation characterizes the angular change of the workpiece relative to its nominal direction. After obtaining the translational and rotational deviations, a global coordinate transformation is performed on the sewing or cutting trajectory during the bag assembly stage, so that the trajectory is synchronously reset with the actual pose of the workpiece. This maintains the preset geometric correspondence between the assembly path and the bag opening endpoints even when the bag opening forming reference is obscured, reducing the risk of assembly offset. It should be noted that since the rotational deviation originates from the difference between the direction of the line connecting the two references and the theoretical connection direction, simple translational compensation is insufficient to eliminate directional errors. Therefore, the combined use of translation and rotation as input for the global coordinate transformation can more completely restore the nominal pose of the assembly path.

[0079] Furthermore, to prevent assembly from being performed and errors from being solidified when the reference is missing or the deviation exceeds the limit, an access control judgment is performed before the bag fabric assembly and sewing is performed. When two reference stitch groups are not detected or the deviation exceeds the preset threshold, the bag fabric assembly and sewing is prohibited and an abnormal indication is output. The reasoning is as follows: when no detection is made, a reliable actual position input cannot be obtained; when the deviation exceeds the limit, it indicates that the workpiece pose has exceeded the compensable range, and continuing to perform the overall coordinate transformation will introduce greater risks. Through the above prohibition and prompt, the assembly process is only executed under detectable and compensable conditions, thereby realizing the closed-loop connection between alignment reset and mistaken control.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A multi-layer cloth detection sewing method applied to the layered processing of a suit welt pocket, characterized by, Includes the following steps: Clamp and position the garment fabric, reinforcing lining, and edge strips to complete the bag opening and form the bag opening and both ends; In the seam allowance area subsequently covered by the bag fabric, a reference stitch group is sewn using a detectable reference thread; A first reference stitch group consisting of two short straight backstitches is sewn at the left end of the bag opening, and a second reference stitch group consisting of three short straight backstitches is sewn at the right end of the bag opening. The geometric center of each reference stitch group is theoretically offset relative to the corresponding endpoint along the length of the bag opening and in its perpendicular direction. Cover the reference stitch group with a lining bag; With the bag cover in the state, the capacitance detection unit, inductance detection unit or eddy current detection unit set on the presser foot or needle plate is used to scan and sample within the preset detection window, and the actual position of the two reference stitch groups is determined according to the two-segment back needle characteristics and the three-segment back needle characteristics, respectively. The translation and rotation deviations are calculated based on the actual position and theoretical offset. Based on this, the overall coordinate transformation of the sewing trajectory or cutting trajectory in the bag assembly stage is performed before bag assembly and sewing. If no two reference stitch groups are detected or the deviation exceeds a preset threshold, bag assembly sewing is prohibited and an abnormality indication is output.

2. The multi-layer cloth detection sewing method according to claim 1, wherein, The steps for inspecting the reference thread sewing reference stitch group are as follows: When the bag is covered, the non-visual detection unit at the pressure foot or needle plate generates relative displacement with the workpiece and forms a scanning trajectory. Detection signals are continuously acquired along the scanning trajectory to form a detection signal sequence; Baseline elimination processing is performed on the detected signal sequence and a set of candidate peak points is extracted.

3. The multi-layer cloth detection sewing method according to claim 2, wherein, Determining the actual positions of the two reference stitches includes the following steps: The candidate peak points are clustered according to the peak spacing to form several peak clusters; Each peak cluster is mapped to a short straight needle stitch detection response, and the cluster center is obtained. The number of peak clusters is counted and segment matching is performed. When there are two peak clusters, it is determined as the first reference stitch group and its actual position is determined by the geometric center of the two cluster centers. When there are three peak clusters, it is determined as the second reference stitch group and its actual position is determined by the geometric center of the three cluster centers.

4. The multi-layer cloth detecting sewing method according to claim 3, wherein Determining the actual positions of the two reference stitches also includes the following steps: Calculate the recognition confidence of the first reference stitch group and the second reference stitch group, wherein the recognition confidence is obtained at least based on the peak cluster number matching result and the consistency of the peak cluster spacing; When the identification confidence level is lower than the preset confidence threshold, the scanning parameters are changed and rescanning is performed to reacquire the detection signal sequence; If the rescan sampling still fails to meet the segment number matching or is still below the preset information threshold, it is determined that the corresponding reference stitch group has not been detected.

5. The multi-layer cloth detection sewing method according to claim 1, wherein, The steps for sewing the reference stitch group are as follows: Select a detectable baseline cable and match it with a non-visual inspection method; When sewing the reference stitch group, control the stitch to sew in the forward direction along the preset straight line to form a short straight stitch segment, and then backstitch along the same straight line direction to form a backstitch segment to form a short straight backstitch. After lifting the needle and moving it to the next position, repeat the forward sewing and backstitching to form the next short straight backstitch stitch. Repeat twice at the left end of the bag opening to form the first reference stitch group; Repeat three times at the right end of the bag opening to form the second reference stitch group.

6. The multi-layer cloth detection sewing method according to claim 5, wherein, The process of creating a reference stitch set at the bag opening includes the following steps: Establish the theoretical coordinates of the bag opening endpoint in the equipment coordinate system; The geometric center theoretical coordinates of each reference stitch group are generated based on the endpoint theoretical coordinates. The geometric center theoretical coordinates are determined by a first theoretical offset along the length direction of the bag opening and a second theoretical offset perpendicular to the length direction of the bag opening. When sewing the first reference stitch group and the second reference stitch group, the corresponding geometric center theoretical coordinates are used as the center of the needle drop area, and short straight backstitches with two or three segments are constructed within the needle drop area.

7. The multi-layer cloth detection sewing method according to claim 6, wherein, The construction of the first and second reference stitch groups specifically includes the following steps: To enhance direction discrimination, inter-segment sequence features are set for the first reference stitch group and the second reference stitch group. The inter-segment sequence features include setting the segment spacing of adjacent short straight backstitches to at least two different spacing levels. When identifying the first reference stitch group and the second reference stitch group, segment number matching and inter-segment sequence matching are performed simultaneously; When the segment number matches but the inter-segment sequence does not match, it is determined as invalid identification and treated as undetected.

8. The multi-layer cloth detection sewing method according to claim 1, wherein, Determining the actual positions of the two reference stitch sets includes the following steps: The translational deviation is calculated based on the actual positions of the first and second reference stitch groups and their respective theoretical coordinates of geometric centers. The rotational deviation is calculated based on the actual connecting direction of the two reference stitch groups and the theoretical connecting direction of the two reference stitch groups. The sewing or cutting trajectory during the bag assembly stage is represented as a set of trajectory points; For each trajectory point in the trajectory point set, rotation compensation is performed first, followed by translation compensation to complete the overall coordinate transformation.

9. The multi-layer cloth detection sewing method according to claim 8, wherein, The overall coordinate transformation includes the following steps: The endpoint reinforcement line trace point set and the bag sealing line trace point set in the bag assembly stage are respectively used as the trajectory point set to be transformed; The same rotation and translation compensations are applied to the endpoint reinforcement line trajectory point set and the sealing bag line trajectory point set; When the bag fabric assembly stage includes a cutting process, the same global coordinate transformation as the sewing trajectory is applied to the set of cutting trajectory points.

10. The multi-layer fabric sewing detection method according to claim 9, characterized in that, The overall transformation conditions specifically include the following steps: Before performing bag fabric assembly and sewing, determine whether the first reference stitch group and the second reference stitch group are both detected and determine whether the recognition confidence level meets the preset conditions. When the detection and confidence conditions are met, determine whether both translational and rotational deviations are within preset thresholds. The assembly and sewing of the bag fabric after global coordinate transformation is allowed when the threshold conditions are met. If the detection conditions, confidence conditions, or threshold conditions are not met, the bag assembly and sewing process will be prohibited, an abnormality indication will be output, and a rescan sampling or re-clamping and positioning will be triggered before another detection and judgment is performed.

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