Feeding and positioning device and method before bending of super-long part

Abstract

The invention discloses a feeding and positioning device and method before bending of ultra-long parts, and belongs to the field of precise forming and manufacturing of metal plates. According to the method, full-field-domain data of a feeding table top are collected through high-precision measurement, and a digital table top model aligned with the center line of a bending mold is constructed; and generating a global datum reference line and a static table top compensation mapping function of which the height is constantly equal to the center line of the mold. In the feeding process, the track deviation of the bottom face of a part relative to a datum line is detected in real time through a non-contact displacement sensor array, the active leveling mechanism is driven to conduct vertical adjustment through feedforward-feedback composite control by combining a static compensation value, and static errors and dynamic disturbance of the table top are synchronously counteracted. And the system continuously monitors the actual track, and triggers an immediate adjustment mechanism when deviation exceeds the limit. According to the method, the global unified reference is established, static pre-compensation and dynamic closed-loop control are fused, multi-stage verification is constructed, the problem of error accumulation in the ultra-long part feeding process is solved, and high-precision positioning is achieved.

Description

Technical Field

[0001] This invention relates to the field of precision forming and manufacturing of sheet metal, and specifically to a feeding and positioning device and method for bending ultra-long parts. Background Technology

[0002] In the field of sheet metal bending, especially for ultra-long parts required in rail transportation, aerospace, and other industries, the feeding and positioning accuracy before bending directly determines the accuracy of the bending line, thus affecting the subsequent assembly quality. Currently, the industry generally uses the same technical approach for feeding and positioning such ultra-long parts as for conventional short-sized parts, primarily relying on the following methods:

[0003] Mechanical stop positioning involves setting a rigid stop at the beginning of the feeding process or at a specific position. Positioning is considered complete when the front end of the part contacts the stop. This method is low-cost and simple to operate, but it can only guarantee a single point of contact and cannot control the overall posture changes of the part during long strokes caused by factors such as uneven table surfaces and sagging due to its own weight. Offset in the middle or tail of the part will directly cause the front end to deflect after contacting the stop, resulting in an unmeasurable angle and translation error between the true bending reference line (die center line) and the theoretical bending line of the part.

[0004] Segmented guide rails, with lateral guide rails along the feeding path, attempt to constrain the lateral position of the parts. However, extra-long parts are often composed of multiple independent support platforms, making it difficult to achieve extremely high precision in the straightness and height consistency of each guide rail segment. Minor segmental misalignments can create a "serpentine" path, forcing the parts to become stuck or generate internal stress during movement, thus introducing new positioning errors and the risk of surface scratches.

[0005] Local sensor feedback involves installing photoelectric or contact sensors near the end of the bending die to detect the instantaneous position of the part and make fine adjustments. However, this method only provides a "remedial" correction to the final position, and the twisting, warping, and other posture errors accumulated during the feeding process, which can last for several meters, cannot be completely eliminated at the last moment.

[0006] Existing technologies indirectly ensure the precise alignment of the entire ultra-long part "continuous body" with another spatial straight line (the mold centerline) by controlling the position of one or several discrete "points" or "local line segments". The control strategy of "using points to represent lines" and "using the local to represent the global" cannot solve the problem of error accumulation at ultra-long scales in terms of physical principles.

[0007] The error sources faced by ultra-long parts during the feeding process are continuously distributed and dynamically changing: the multi-segmented feeding table, with its overall flatness, straightness, height differences between segments, and misalignment of joints, constitutes a complex and non-ideal support surface. Traditional methods cannot fully perceive and compensate for this surface error. The elastic deflection of the part itself due to gravity under ultra-long spans, and the dynamic deformation caused by speed changes and inertial forces during movement, mean that its actual axis is not an ideal straight line. Controlling only the positions of its two ends or a few points cannot constrain and correct its overall bending shape. The references relied upon by the aforementioned local positioning methods (such as the position of the stop block, the guide rail mounting surface, and the sensor zero point) are usually not calibrated and associated with the final target, the centerline of the bending die, in a unified, high-precision global coordinate system. This results in the entire positioning process lacking a single, reliable absolute spatial reference throughout.

[0008] As the length of a part increases to a certain extent, the inherent errors of these localized, discrete, and inconsistent control methods will continue to propagate and amplify along the feeding direction. This results in lateral offsets, height deviations, and deflection angles far exceeding the process allowances when the front end of the part reaches the bending die. This not only causes single bending to exceed tolerances, but also makes it impossible to assemble large components that require multiple bends due to the accumulation of errors. Summary of the Invention

[0009] The purpose of this invention is to provide a feeding and positioning device and method for ultra-long parts before bending, which solves the technical problem that the positioning accuracy of ultra-long parts is seriously out of tolerance when the front end of the part reaches the bending die due to the gradual accumulation of geometric errors of the segmented support table and the dynamic deformation of the part itself during the bending feeding process.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A method for feeding and positioning ultra-long parts before bending includes the following steps:

[0012] When the equipment is unloaded, full-field geometric data is collected on the entire feeding table to obtain the spatial coordinate point cloud of the table surface; the spatial coordinate point cloud is registered to the absolute coordinate system with the center line of the bending die as the origin to generate a digital table model.

[0013] Based on the digital tabletop model, extract the vertical height coordinate values ​​that are distributed at intervals along the feeding direction, and construct the original tabletop height distribution function;

[0014] Based on the digital table model and the centerline height of the bending die, a global reference correction algorithm is executed to calculate the static table compensation mapping value at each location point, and a horizontal straight line with a height that is always equal to the centerline height of the bending die is generated as the corrected global reference line.

[0015] During the feeding process, multiple sets of non-contact displacement sensor arrays arranged above the feeding path are used to detect the measured distance value of the bottom surface of the ultra-long part relative to the fixed reference of the machine tool in real time; the difference between the measured distance value and the target value at the corresponding position in the corrected global reference line is calculated to obtain the trajectory deviation.

[0016] By combining the trajectory deviation with the static platform compensation mapping value of the corresponding position point, a sequence of positioning correction values ​​is generated for each active leveling mechanism control point throughout the entire path using a feedforward-feedback composite control method. For each control point... Its positioning correction value for: ;

[0017] in: Active leveling mechanism control points At any moment The positioning correction value;

[0018] : The position of the control point of the active leveling mechanism;

[0019] Time variable;

[0020] Control points The corresponding static platform compensation mapping function value;

[0021] : Proportional control gain coefficient (dimensionless, typical value [5,20], determined according to part thickness H and feed rate v);

[0022] Integral control gain coefficient (unit: 1 / s, typical value: [0.1, 1.0], determined based on part thickness H and feed rate v);

[0023] Control point xm at time 1 The trajectory deviation (the difference between the bottom surface of the part and the corrected global reference line).

[0024] : Integral variable (representing the time integration interval);

[0025] The integral term of the trajectory deviation over the time interval.

[0026] According to the positioning correction value sequence, the active leveling mechanism on each support section is controlled to adjust its position in the vertical direction to offset the influence of static deviation and dynamic disturbance on the posture of the parts.

[0027] The actual trajectory of the ultra-long part during its movement is continuously monitored, and the actual trajectory is compared with the corrected global reference line. When the actual trajectory deviates from the corrected global reference line by more than a preset threshold, an instant adjustment mechanism is triggered. When the front end of the ultra-long part approaches the entry area of ​​the bending die, the edge contour image of the front end of the part is captured by the visual recognition module, and its geometric center line is extracted.

[0028] Calculate the positioning consistency index between the geometric center line and the bending die center line, and if the positioning consistency index does not meet the set accuracy requirements, start the end fine-tuning program to correct the position of the front end of the part.

[0029] Furthermore, the full-field geometric data acquisition of the entire feeding platform specifically includes:

[0030] Data acquisition is performed using a high-precision laser scanning system or a structured light 3D measurement device.

[0031] The measuring device is mounted on the table above the platform perpendicular to the feeding direction and moves along the feeding direction at a constant speed;

[0032] During the data collection process, ensure that the sampling density meets the requirement of at least one hundred valid points per unit length.

[0033] Furthermore, the generation of the digital countertop model specifically includes:

[0034] The registered spatial coordinate point cloud is used to reconstruct the surface using a triangulation algorithm;

[0035] The reconstructed platform model is stored in a regular grid format, with the grid spacing set to 10 millimeters.

[0036] Each grid node records its precise coordinates in the X, Y, and Z dimensions, with the X-axis along the feeding direction and the Z-axis pointing vertically upwards.

[0037] Furthermore, the global benchmark correction algorithm includes the following steps:

[0038] Read the height value of the pre-calibrated bending die centerline in the absolute coordinate system, and record it as . ;

[0039] According to the original table height distribution function The calculation adjusts each point on the platform to the specified height. The required static compensation amount is used to generate a static platform compensation mapping function. ,in: ;

[0040] Function The defined horizontal straight line is determined as the corrected global reference line. ,in, This is the height function of the corrected global reference line.

[0041] Furthermore, the measurement points of the non-contact displacement sensor array correspond one-to-one with the support points of the active leveling mechanism in the feeding direction; each sensor group contains at least three eddy current or laser triangulation ranging units, which are symmetrically arranged in the transverse direction perpendicular to the feeding direction to simultaneously measure the height of different transverse positions on the bottom surface of the part, and eliminate single-point measurement errors caused by transverse sway or torsion of the part by calculating the average value.

[0042] Furthermore, the step of generating a positioning correction value sequence by combining the trajectory deviation and the static platform compensation mapping value specifically involves:

[0043] For each control point of the active leveling mechanism Directly obtain the trajectory deviation corresponding to that point. Mapping value with static tabletop compensation ;

[0044] The positioning correction value of the control point is calculated based on the following formula. :

[0045] ;

[0046] in, Time variable;

[0047] The integral term of the trajectory deviation over the time interval;

[0048] : Integral variable (representing the time integration interval);

[0049] (Proportional gain) and (Integral gain) is the control gain coefficient determined based on the part thickness H and the feed rate v. Typical value range: (dimensionless) For example: when the part thickness H=8mm and the feeding speed v=0.5m / s, take... , .

[0050] The positioning correction values ​​of all control points constitute the positioning correction value sequence.

[0051] Furthermore, the instant adjustment mechanism includes:

[0052] First-level local fine-tuning: When a trajectory deviation point is detected, the two sets of active leveling mechanisms upstream and downstream of the nearest neighbor of the deviation point are activated. By controlling the two sets of mechanisms to generate vertical displacements in opposite directions, the part is subjected to a corrective torque at the deviation point, thereby suppressing local drift.

[0053] Second-level parameter readjustment: When multiple consecutive trajectory points deviate beyond the tolerance band, or a single point deviates beyond twice the tolerance threshold, the central coordinating controller initiates an online parameter identification algorithm, mapping the static platform compensation value based on the real-time trajectory deviation sequence. Perform local gradient updates and send the updated compensation values ​​to the corresponding active leveling mechanisms.

[0054] Furthermore, the geometric center line of the front end of the part is extracted through the visual recognition module, specifically including:

[0055] A vision system consisting of an industrial CMOS camera, a telecentric lens, and a ring LED light source is used to capture images of the front edge contour of a part.

[0056] The image is preprocessed by grayscale conversion, Gaussian filtering, and contrast enhancement; the edge positions are located using a sub-pixel edge detection algorithm based on Zernike moments.

[0057] The extracted edge contours are fitted to straight lines using Hough transform, and the geometric center line is calculated.

[0058] Furthermore, the end-effector fine-tuning procedure specifically includes:

[0059] Position correction is achieved by controlling the lateral micro-motion platform of the end clamping mechanism of the feeding trolley;

[0060] The transverse micro-motion platform consists of a cross roller guide and a piezoelectric actuator, with a stroke range of ±2 mm and a closed-loop control resolution better than 0.5 micrometers.

[0061] The required lateral translation and rotation are calculated based on the positioning consistency index, and a composite motion command is generated to drive the micro-motion platform. After one adjustment, the visual recognition module is used for retesting until the positioning consistency index meets the set accuracy requirements.

[0062] In addition, the present invention also discloses a feeding and positioning device for ultra-long parts before bending, used to realize the feeding and positioning method for ultra-long parts before bending as described above, including:

[0063] The digital modeling and benchmark establishment module is configured to collect full-field geometric data of the entire feeding table surface under no-load conditions, and obtain the spatial coordinate point cloud of the table surface; register the spatial coordinate point cloud to an absolute coordinate system with the center line of the bending die as the origin to generate a digital table surface model; and generate a horizontal straight line with a height that is always equal to the height of the center line based on the height of the digital table surface model and the center line of the bending die as a corrected global benchmark reference line, while calculating the static table surface compensation mapping function.

[0064] The real-time feeding and positioning compensation module is configured to detect the trajectory deviation of the bottom surface of the ultra-long part relative to the corrected global reference line in real time during the feeding process using a non-contact displacement sensor array; combine the trajectory deviation with the static table compensation mapping function value at the corresponding position to generate a positioning correction value sequence, and control the active leveling mechanism to adjust the vertical position.

[0065] The feeding trajectory monitoring and real-time adjustment module is configured to continuously monitor the actual feeding trajectory of the extra-long part and compare it with the corrected global reference line; when the actual trajectory deviates from the preset threshold, the real-time adjustment mechanism is triggered.

[0066] The end-effector visual fine-tuning module is configured to extract the geometric center line of the ultra-long part by means of a visual recognition module when the front end of the part approaches the entry area of ​​the bending die; calculate the positioning consistency index between the geometric center line and the center line of the bending die; and start the end-effector fine-tuning program to correct the error if the index does not meet the set accuracy requirements.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] Traditional methods rely on multiple local, discrete physical or sensory references for segmented positioning. Essentially, they attempt to approximate a global path by connecting multiple independent coordinate systems. This leads to the inevitable amplification of static deviations such as manufacturing and installation errors and thermal deformation in each support segment, as well as dynamic disturbances such as deflection due to the component's own weight, during the transmission process. This invention abandons this indirect logic of approximating the whole with the local. Before feeding, it directly constructs a corrected global reference line, strictly aligned with the bending die centerline and running through the entire feeding path, through full-field digital modeling. This reference line, defined in an absolute coordinate system, provides a unique, continuous, and high-precision spatial reference for the entire movement of ultra-long parts, completely eliminating the systematic cumulative errors caused by reference transformation and segmented splicing from a fundamental technical perspective.

[0069] This invention achieves a deep integration of static pre-compensation and dynamic closed-loop control, transforming passive adaptation into active regulation: Existing technologies often passively accept or partially remedy table geometric errors. This invention calculates a static table compensation mapping function, precisely quantifies and stores the static geometric deviation along the entire path, and eliminates it through feedforward control at the start of feeding. Simultaneously, it combines real-time sensing of trajectory deviation for feedback control, forming a feedforward-feedback composite control law, thereby suppressing dynamic disturbances in real time. This transforms the system from a passive response to uncontrollable errors to active, precise regulation based on accurate models and real-time sensing, improving the system's anti-interference capability and overall accuracy and stability.

[0070] This invention ensures the controlled state of the intermediate process by continuously monitoring the actual feeding trajectory and comparing and adjusting it in real time with the calibrated global reference line. When the front end of the ultra-long part approaches the entry area of ​​the bending die, an independent visual recognition and end-effector fine-tuning program is introduced to perform absolute measurement and correction of the final pose, forming a complete verification closed loop from process to endpoint. This ensures that the positioning consistency index between the geometric center line of the part's front end and the center line of the bending die is strictly controlled, thus providing reliable input conditions for subsequent bending processes. This invention solves the technical problems caused by local reference discrepancies and error accumulation along the process by reconstructing the reference establishment and error control method for ultra-long part feeding and positioning. Attached Figure Description

[0071] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0072] Figure 1 This is an overall flowchart of the method described in this invention.

[0073] Figure 2 This is a flowchart illustrating the steps of digital modeling and benchmark establishment in this invention.

[0074] Figure 3 This is a flowchart of the real-time feeding and positioning compensation steps of the present invention.

[0075] Figure 4 This is a block diagram of the overall architecture of the device described in this invention. Detailed Implementation

[0076] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0077] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0078] Example 1: See Figures 1-4 This embodiment discloses a feeding and positioning method for ultra-long parts before bending. By establishing a digital table geometric model covering the entire feeding path, and on this basis establishing a global reference line that is strictly aligned with the center line of the bending die, high-precision front-end positioning of ultra-long parts before entering the bending station is achieved through multi-source sensor fusion, dynamic compensation control and closed-loop trajectory verification mechanism.

[0079] The following will elaborate on the specific implementation of the present invention in detail, including system composition, data modeling, benchmark correction, real-time correction, trajectory monitoring, and terminal fine-tuning.

[0080] First, with the equipment in an unloaded state and the ambient temperature stable, a high-precision laser scanning system or structured light 3D measurement device is activated to acquire full-field geometric data of the entire feeding platform. This measurement device is mounted on a crossbeam above the platform, perpendicular to the feeding direction, and possesses sub-millimeter spatial resolution and repeatability better than ±0.02 mm. During scanning, the device moves at a constant speed along the feeding direction, synchronously triggering point cloud data acquisition to ensure a sampling density of at least one hundred valid points per unit length. The acquired spatial coordinate point cloud data, after preliminary filtering and noise reduction, is transmitted to the central collaborative controller.

[0081] After receiving the raw point cloud data, the central coordinating controller performs coordinate system registration. The registration process uses a fixed physical marker point on the center line of the bending die as the origin, defining the X-axis as extending positively along the feeding direction, the Y-axis as horizontally pointing towards the die's symmetry plane, and the Z-axis as vertically upwards, forming a right-handed Cartesian coordinate system. A rigid body transformation matrix is ​​used to uniformly transform all platform sampling points to this absolute coordinate system, forming a registered 3D point cloud set. Subsequently, a triangulation algorithm is used to reconstruct the surface of this point cloud set, generating a digital platform model that includes height deviation, flatness error, and misalignment information at the joints of adjacent support sections. This model is stored in a regular grid format with a grid spacing of ten millimeters. Each grid node records its precise coordinate values ​​in the X, Y, and Z dimensions and is stored in the non-volatile memory of the central coordinating controller, serving as the basic reference for all subsequent positioning calculations.

[0082] Furthermore, based on the digital tabletop model, the Z-coordinate values ​​at each location are extracted along the X-axis at five-millimeter intervals to construct the original tabletop height distribution function. ,in L represents the total length of the feeding path. This function fully characterizes the actual spatial coordinates of the physical platform across its entire length before compensation. Based on this, a global benchmark correction algorithm is executed to determine an ideal reference line running from the starting end to the bending end.

[0083] The algorithm specifically includes the following steps:

[0084] S1: Die reference calibration. During the equipment installation phase, a laser tracker is used to measure the spatial coordinates of feature points on the centerline of the bending die, and their Z-coordinate values ​​are calibrated and stored as the die centerline height reference. .

[0085] S2: Static tabletop compensation mapping calculation. The central collaborative controller calculates the static tabletop compensation mapping based on the height function in the digital tabletop model. Compared with the calibration value Calculate the static compensation amount for the entire path. For any position on the feeding path... Its static platform compensation mapping value It is given by the following formula:

[0086] ;

[0087] The physical meaning is: in order to make the position The platform at that location reaches the same height as the center line of the mold. The active leveling mechanism at this location needs to be adjusted. distance ( Indicates an increase, (Indicates a decrease).

[0088] S3: Determination of the global reference line. The corrected global reference line... It is a horizontal straight line that is clearly defined in space, and its equation is uniquely determined by the height reference of the mold centerline:

[0089] ,in, The height function of the corrected global reference line;

[0090] This straight line represents the target trajectory that needs to be tracked during the feeding process of extra-long parts.

[0091] Therefore, the corrected global reference line Defined as a height that is always equal to The horizontal straight line has the following function expression: This reference line represents the target spatial trajectory that the extra-long part needs to be tracked during the feeding process. Based on this, the system initiates a real-time positioning correction process. It will be stored in the central coordinating controller for subsequent feedforward compensation control.

[0092] On the corrected reference line (Right now After the position is established, the system initiates a real-time positioning correction process. This process is executed by multiple arrays of non-contact displacement sensors arranged above the feeding path. The installation positions of the non-contact displacement sensor arrays are strictly aligned with the support points of each active leveling mechanism in the feeding direction (X-axis), ensuring that there is a corresponding sensor above each support point for measurement, thereby achieving a one-to-one correspondence between measurement points and control points. Each sensor array contains at least three eddy current or laser triangulation units, arranged in a laterally symmetrical layout to eliminate measurement deviations caused by lateral sway of the part. Each sensor continuously detects the distance between the bottom surface of the extra-long part and the machine tool's fixed reference frame at its corresponding X-position. The value is then transmitted to the central co-controller via the industrial real-time Ethernet bus.

[0093] The central collaborative controller has the corresponding location stored internally. Target feeding trajectory value Mapping values ​​of static tabletop compensation The controller first calculates the current trajectory deviation (feedback error):

[0094] All sensor data are aligned via a time synchronization module to ensure that each It has a unified timestamp and a synchronization accuracy better than 100 microseconds.

[0095] The central coordinating controller receives trajectory deviations from each sensor. Then, combined with the pre-stored static table compensation mapping Generate a sequence of location correction values ​​across the entire path. ,in , The locations of the control points corresponding to each active leveling mechanism;

[0096] in:

[0097] The location of the trajectory detection points corresponding to each sensor ( (Sensor serial number).

[0098] t: Real-time time during the feeding process (reflecting the time attribute of dynamic compensation);

[0099] : testing point At any moment Real-time trajectory deviation;

[0100] : Pre-stored static tabletop compensation mapping;

[0101] : The location of the control points corresponding to each active leveling mechanism (m is the leveling mechanism number);

[0102] : The real-time positioning correction value of control point xm at time t;

[0103] The total number of institutions that actively adjust the balance.

[0104] Each active leveling mechanism control point Positioning correction value It is generated by superimposing the feedforward compensation and the feedback compensation:

[0105] ;

[0106] in, This is a feedforward compensation amount from the static mapping, used to offset known table geometry errors; For proportional feedback items, The integral feedback term and the two together constitute the feedback compensation quantity, which is used to suppress dynamic trajectory deviations caused by part weight, inertia and external disturbances in real time. and The control gain coefficient is pre-tuned.

[0107] The sequence was generated using a combination of interpolation and extrapolation: for the region located between sensors, and Cubic spline interpolation was used for estimation; for the starting and ending regions, linear extrapolation was performed based on the boundary conditions.

[0108] The compensation command is issued to each independent servo drive unit. An active leveling mechanism is installed at the bottom of each support section, consisting of a precision ball screw pair driven by a servo motor. Its vertical travel is ±5 mm, with a positioning resolution better than 1 micrometer, used to execute precise position adjustments based on the positioning correction value sequence command, with a positioning repeatability better than ±1 micrometer. Two actuators are selected and configured according to the location of the support section and the expected disturbance characteristics. The actuator output is directly connected to the bottom of the table support plate, and through micrometer-level vertical displacement adjustment, the local table height is changed in real time, thereby offsetting the influence of original manufacturing and installation errors on the part's posture.

[0109] Meanwhile, the system continuously monitors the actual trajectory of the ultra-long part during its movement. This trajectory is jointly calculated by an inertial measurement unit (IMU) mounted on the feeding trolley and a laser tracker measurement system. Specifically, a laser tracker mounted on a fixed reference on the machine tool measures the three-dimensional coordinates of an optical target mounted on the feeding trolley in real time, providing absolute position information; the IMU provides high-frequency angular velocity and acceleration data. The two sets of data are fused using an extended Kalman filter algorithm. The fused state vector includes position, velocity, attitude angle, and their deviation terms. The angular velocity and acceleration outputs of the IMU serve as the basis for system state prediction; the three-dimensional coordinate data provided by the laser tracker are used as observations to correct the predicted state. The fused output is a continuous and stable six-degree-of-freedom pose estimate. ;

[0110] in:

[0111] : The spatial pose state vector of the part (or feeding actuator) at any given moment (including position and attitude information);

[0112] : The position coordinates of the part in the feeding direction (X-axis) at time t (unit: mm, consistent with the definition of the feeding path coordinate x);

[0113] : Position coordinates of the part at time t in the horizontal transverse direction (Y-axis) perpendicular to the feeding direction (unit: mm);

[0114] : The height coordinate of the part in the vertical direction (Z-axis) at time t (unit: mm, consistent with the height dimension of the table).

[0115] : The rotation angle of the part about the X-axis (feeding direction) at time t (roll angle, unit: rad / °, characterizing the torsional deviation of the part along the feeding direction);

[0116] : The rotation angle (pitch angle, unit: rad / °, representing the tilt deviation of the part in the vertical direction) of the part around the Y-axis (horizontal transverse direction) at time t.

[0117] : The rotation angle of the part around the Z-axis (vertical direction) at time t (yaw angle, unit: rad / °, characterizing the horizontal steering deviation of the part);

[0118] : Transpose of a vector (converts a row vector into a column vector, conforming to the common representation of state vectors in the control domain).

[0119] The pose estimation result is projected onto the XZ plane in real time to extract its longitudinal trajectory. and with the corrected global reference line (i.e., constant height) Perform point-by-point comparison.

[0120] If in any position The following conditions must be met: ;

[0121] in:

[0122] Extra-long parts in position The actual trajectory height at that location;

[0123] Any deviation of the feed path from the detection point position;

[0124] If a preset tolerance threshold (typically ±0.1 mm) is set, an immediate adjustment mechanism will be triggered.

[0125] The instant adjustment mechanism comprises two levels of operation. The first level is local fine-tuning: the system identifies deviation points. Then, activate the two nearest neighbor active leveling mechanisms (located at respectively) and Based on the direction and magnitude of the deviation, the required reverse compensation torque is calculated. This torque is achieved by coordinating the displacement of the two actuators; for example, if the part is in... If it arches upwards, then... The actuator descends slightly. The actuator slightly rises to create downward torque to suppress local drift. The second level is global replanning: when more than five consecutive sampling points in the intermediate path exceed the tolerance band, or a single point deviates more than twice the tolerance threshold, the central coordinating controller determines that the platform state has changed significantly and immediately re-invokes the global benchmark correction algorithm. At this time, the system can selectively activate the fast scan mode, only performing local point cloud re-sampling on the affected area, or calling historical data combined with current sensor readings to update the model. The updated digital platform model is used for recalculation. and and based on the new A new sequence of positioning correction values ​​is generated and distributed to all execution units to complete the dynamic reconstruction of the baseline.

[0126] Finally, when the front end of the extra-long part approaches the entry area of ​​the bending die (typically defined as the area less than 500 mm from the die centerline), the system performs a final precise positioning check. This stage utilizes a high-resolution vision recognition module, consisting of an industrial CMOS camera, a telecentric lens, and a ring-shaped LED light source, mounted directly above the die entry, covering a 50 mm area at the front end of the part. The camera captures images of the part's front edge contour at a rate of 30 frames per second, achieving an image resolution of 5,000 pixels per millimeter.

[0127] The central coordinating controller preprocesses the image, including grayscale conversion, Gaussian filtering, and contrast enhancement. Then, a sub-pixel edge detection algorithm is applied: specifically, an edge localization method based on Zernike moments is used. This method involves performing an orthogonal polynomial expansion on a local image region and estimating the sub-pixel position of the edge using the ratio of the zeroth-order to the first-order moment. This algorithm can improve edge localization accuracy to within 0.1 pixels. The extracted front-end edge contour is fitted to a straight line using a Hough transform, and its geometric centerline is calculated. .

[0128] Bending die centerline The positions of the two lines in the visual coordinate system are determined by prior calibration, and their equations are known. The system calculates the shortest distance between the two lines in the XY plane. and included angle deviation Positioning consistency index Defined as:

[0129] ;

[0130] in, This is the angle-displacement equivalence coefficient, set empirically based on the part thickness and bending radius. For example, it can be taken as 1 / 1000 of the part thickness H (unit: mm / rad). For instance, when the part thickness H = 8 mm, k = 0.008 mm / rad; when the bending radius is greater than 10 mm, it can be corrected to k = 0.01 mm / rad.

[0131] like The set accuracy requirement was not met (e.g.) If the value is less than 1 millimeter, then the end fine-tuning procedure will be initiated.

[0132] The end-effector fine-tuning program is implemented by controlling the lateral micro-motion platform of the end-effector clamping mechanism of the feeding trolley. This platform consists of cross roller guides and piezoelectric actuators, with a stroke range of ±2 mm and a closed-loop control resolution better than 0.5 micrometers.

[0133] Controller according to and The X-axis translation and Z-axis rotation required for decoupling calculations are used to generate a composite motion command. After the platform executes this command, it triggers the visual recognition module again for retesting until... To meet accuracy requirements, ensure that the center line of the front end of the part is perfectly aligned with the center line of the bending die in space.

[0134] Throughout the feeding process, all sensor data, control commands, and status feedback are transmitted via an industrial real-time Ethernet bus (such as EtherCAT or PROFINETIRT). The network topology adopts a linear or star structure, with the master station being a central coordinating controller, and the slave stations including various sensor interface modules, servo drivers, and vision processing units. The communication cycle is set to one millisecond, and time synchronization adopts a distributed clock mechanism to ensure that the time synchronization accuracy between subsystems is better than one hundred microseconds, meeting the timing requirements of high-speed dynamic compensation.

[0135] Furthermore, the central collaborative controller has a built-in fault diagnosis module, employing a hybrid diagnostic strategy that combines model-based and data-driven approaches. For sensors, failures are detected through residual analysis: if a sensor reading consistently deviates from its neighborhood mean by more than three standard deviations, it is marked as abnormal. For communication links, interruptions are monitored through a heartbeat mechanism. For actuators, jamming or hysteresis faults are identified by comparing current-displacement characteristic curves. Once an abnormal event is detected, the system automatically switches to redundant channels (such as backup sensors or communication lines) or degrades to a safe mode (such as pausing feeding or maintaining the current position), while simultaneously sending fault codes and suggested handling measures to the operating terminal to ensure the safety and robustness of the positioning process.

[0136] In one specific embodiment, a 2800mm long and 2mm thick 2024 aluminum alloy plate was selected as the workpiece. The feeding table was composed of six independent support units, with a total length of thirteen meters. First, an idle laser scan was performed to generate a digital table model, and the flatness error (peak-to-peak value) of the original table over its entire length was measured to be 2.7 mm (i.e., the difference between the highest and lowest points). After processing with a global reference correction algorithm, the static table compensation mapping was calculated. The numerical range is between [-1.8, +0.9] mm, and its peak-to-peak value is also 2.7 mm. During the feeding process, displacement sensors arranged at each support point update the trajectory deviation at a period of ten milliseconds, and the active leveling mechanism (precision ball screw pair) performs dynamic compensation based on the combined feedforward and feedback commands. The trajectory monitoring shows that the actual trajectory of the part and the global reference line ( The maximum deviation was controlled within ±0.05 mm. During the end-point visual verification phase, the initial positioning consistency index... The thickness was initially measured in millimeters, but after a minor adjustment, it was reduced to 0.03 millimeters, meeting the requirements of the bending process.

[0137] To verify the technical effects of the present invention, the following comparative example 1 was conducted.

[0138] Comparative Example 1: Using the traditional segmented reference transfer method: A mechanical stop is only set at the starting end as the positioning reference, with no active compensation in the intermediate segments, relying solely on the manufacturing precision of the table itself. Identical parts are fed onto the same equipment. Due to cumulative table errors and the deflection caused by the part's own weight, when the front end of the part reaches the bending station, its position relative to the mold centerline exhibits a lateral offset of 0.65 mm and a longitudinal height deviation of 0.42 mm. Positioning consistency index... Millimeters, far exceeding the process allowable range (usually required) (millimeters), resulting in the bending of the part's angle exceeding the tolerance, requiring rework and correction.

[0139] Table 1 summarizes the comparison results of key performance indicators between Example 1 and Comparative Example 1:

[0140] Table 1:

[0141]

[0142] The above data shows that by constructing a full-path digital model and implementing dynamic compensation and closed-loop verification, the present invention effectively overcomes the problem of cumulative error in the feeding process of ultra-long parts, and significantly improves positioning accuracy and process stability.

[0143] This invention discloses a feeding and positioning method for ultra-long parts before bending. Through systematic data acquisition, model building, benchmark correction, real-time adjustment, trajectory monitoring, and end-effector fine-tuning, it forms a complete high-precision positioning solution. Its technical implementation does not rely on idealized table manufacturing conditions, but rather incorporates the uncertainties of the physical world into a controllable range through proactive sensing and intelligent control. This ensures that ultra-long parts can achieve micron-level positioning accuracy even in complex industrial environments, providing reliable technical support for high-quality bending and forming of large structural components.

[0144] This invention solves the problem of cumulative positioning deviation along the feed path caused by manufacturing and installation errors, thermal deformation, and self-weight deflection. The method constructs a digital table model covering the entire feeding path through high-precision scanning and establishes a global reference line based on the bending die centerline. Combining multi-point non-contact displacement sensing and real-time trajectory monitoring, it dynamically generates compensation commands to drive an active leveling mechanism for micron-level correction. Simultaneously, it employs multi-source sensor fusion and closed-loop control strategies to achieve high-precision unified reference positioning from the starting end to the bending end, ensuring strict alignment between the part's front end and the bending die centerline.

[0145] Example 2: This example also discloses a feeding and positioning device for ultra-long parts before bending, comprising:

[0146] The digital modeling and benchmark establishment module is configured to collect full-field geometric data of the entire feeding table surface under no-load conditions, and obtain the spatial coordinate point cloud of the table surface; register the spatial coordinate point cloud to an absolute coordinate system with the center line of the bending die as the origin to generate a digital table surface model; and generate a horizontal straight line with a height that is always equal to the height of the center line based on the height of the digital table surface model and the center line of the bending die as a corrected global benchmark reference line, while calculating the static table surface compensation mapping function.

[0147] The real-time feeding and positioning compensation module is configured to detect the trajectory deviation of the bottom surface of the ultra-long part relative to the corrected global reference line in real time during the feeding process using a non-contact displacement sensor array; combine the trajectory deviation with the static table compensation mapping function value at the corresponding position to generate a positioning correction value sequence, and control the active leveling mechanism to adjust the vertical position.

[0148] The feeding trajectory monitoring and real-time adjustment module is configured to continuously monitor the actual feeding trajectory of the extra-long part and compare it with the corrected global reference line; when the actual trajectory deviates from the preset threshold, the real-time adjustment mechanism is triggered.

[0149] The end-effector visual fine-tuning module is configured to extract the geometric center line of the ultra-long part by means of a visual recognition module when the front end of the part approaches the entry area of ​​the bending die; calculate the positioning consistency index between the geometric center line and the center line of the bending die; and start the end-effector fine-tuning program to correct the error if the index does not meet the set accuracy requirements.

[0150] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for feeding and positioning ultra-long parts before bending, characterized in that, Includes the following steps: Digital modeling and benchmark establishment steps: Under no-load conditions, collect full-field geometric data of the entire feeding table surface to obtain the spatial coordinate point cloud of the table surface; register the spatial coordinate point cloud to the absolute coordinate system with the center line of the bending die as the origin to generate a digital table surface model; based on the height of the digital table surface model and the center line of the bending die, generate a horizontal straight line with a height always equal to the height of the center line as the global benchmark reference line after correction, and calculate the static table surface compensation mapping function; Real-time feeding and positioning compensation steps: During the feeding process, the trajectory deviation of the bottom surface of the extra-long part relative to the corrected global reference line is detected in real time by a non-contact displacement sensor array; combined with the trajectory deviation and the static table compensation mapping function value at the corresponding position, a positioning correction value sequence is generated, and the active leveling mechanism is controlled to adjust the vertical position. Feed trajectory monitoring and real-time adjustment steps: Continuously monitor the actual feeding trajectory of the extra-long part and compare it with the corrected global reference line; When the actual trajectory deviates from the preset threshold, an immediate adjustment mechanism is triggered; End-of-line visual fine-tuning steps: When the front end of the extra-long part approaches the entry area of ​​the bending die, its geometric center line is extracted by the visual recognition module; the positioning consistency index between the geometric center line and the center line of the bending die is calculated, and if the positioning consistency index does not meet the set accuracy requirements, the end-of-line fine-tuning program is started for correction.

2. The feeding and positioning method for ultra-long parts before bending according to claim 1, characterized in that, In the digital modeling and benchmark establishment steps, generating the corrected global benchmark reference line specifically includes: Read the pre-calibrated centerline height value of the bending die ; Based on the original tabletop height distribution function obtained from the digital tabletop model Calculate the static platform compensation mapping function. ; Function The defined horizontal straight line is determined as the corrected global reference line. ,in, This is the height function of the corrected global reference line.

3. The feeding and positioning method for ultra-long parts before bending according to claim 1, characterized in that, In the real-time feeding positioning compensation step, the specific steps for generating the positioning correction value sequence are as follows: For each control point of the active leveling mechanism Obtain the trajectory deviation corresponding to that point. Mapping function value with static table compensation ; The positioning correction value of the control point is calculated based on the following formula. : ； in, Time variable; The integral term of the trajectory deviation over the time interval; : Integral variable, representing the time integration interval; The proportional control gain coefficient is determined based on the part thickness H and the feeding speed v. The integral control gain coefficient is determined based on the part thickness H and the feeding speed v; the positioning correction values ​​of all control points constitute the positioning correction value sequence.

4. The feeding and positioning method for ultra-long parts before bending according to claim 1, characterized in that, The positions of the measurement points of the non-contact displacement sensor array in the feeding direction correspond one-to-one with the positions of the support points of the active leveling mechanism.

5. The feeding and positioning method for ultra-long parts before bending according to claim 4, characterized in that, Each sensor group contains at least three ranging units arranged symmetrically in the lateral direction to simultaneously measure the height of different lateral positions on the bottom surface of the part, thereby eliminating measurement errors caused by the lateral sway of the part.

6. The feeding and positioning method for ultra-long parts before bending according to claim 1, characterized in that, Extracting the geometric center line of the front end of the part through the visual recognition module specifically includes: Capture the outline image of the front edge of the part; After image preprocessing, a subpixel edge detection algorithm is applied to locate edges; The extracted edge contours are fitted to a straight line to obtain the geometric center line.

7. The feeding and positioning method for ultra-long parts before bending according to claim 1, characterized in that, The end fine-tuning program is implemented by controlling the lateral micro-motion platform at the end of the feeding trolley. The lateral micro-motion platform performs a composite motion based on the translation and rotation calculated by the positioning consistency index.

8. A method for feeding and positioning ultra-long parts before bending according to any one of claims 1-7, characterized in that, The acquisition of full-field geometric data for the entire feeding platform is accomplished by using high-precision laser scanning or structured light three-dimensional measurement, and by moving and scanning along a direction perpendicular to the feeding direction.

9. A feeding and positioning device for ultra-long parts before bending, used to implement the feeding and positioning method for ultra-long parts before bending according to any one of claims 1-8, characterized in that, include: The digital modeling and benchmark establishment module is configured to collect full-field geometric data of the entire feeding table surface under no-load conditions, and obtain the spatial coordinate point cloud of the table surface; register the spatial coordinate point cloud to an absolute coordinate system with the center line of the bending die as the origin to generate a digital table surface model; and generate a horizontal straight line with a height that is always equal to the height of the center line based on the height of the digital table surface model and the center line of the bending die as a corrected global benchmark reference line, while calculating the static table surface compensation mapping function. The real-time feeding and positioning compensation module is configured to detect the trajectory deviation of the bottom surface of the ultra-long part relative to the corrected global reference line in real time during the feeding process using a non-contact displacement sensor array; combine the trajectory deviation with the static table compensation mapping function value at the corresponding position to generate a positioning correction value sequence, and control the active leveling mechanism to adjust the vertical position. The feeding trajectory monitoring and real-time adjustment module is configured to continuously monitor the actual feeding trajectory of the extra-long part and compare it with the corrected global reference line; when the actual trajectory deviates from the preset threshold, the real-time adjustment mechanism is triggered. The end vision fine-tuning module is configured to extract the geometric center line of the ultra-long part by means of a vision recognition module when the front end of the part approaches the entry area of ​​the bending die. The positioning consistency index between the geometric center line and the bending die center line is calculated, and if the positioning consistency index does not meet the set accuracy requirements, the end fine-tuning program is started for correction.

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