Automatically adjusted workpiece clamping system and control method

Abstract

The invention discloses an automatically-adjusted workpiece clamping system and a control method, and belongs to the technical field of machining, clamping and positioning. The system comprises a clamp base, a lineation detection unit, an image acquisition unit, a hydraulic adjustment unit and a control unit. The hydraulic adjusting unit comprises hydraulic cylinder sets in the X direction, the Y direction and the Z direction, the two hydraulic cylinders in the Z direction are communicated through a hydraulic communicating device to form linkage, the two hydraulic cylinders in the Z direction and the other two hydraulic cylinders jointly form a three-point supporting structure, and the over-positioning problem of four-point supporting is solved. The control unit carries out processing and feature extraction on the image, calculates the six-degree-of-freedom deviation of the workpiece, calculates the adjustment amount of each hydraulic cylinder according to the deviation and controls the hydraulic cylinders to act. The system realizes closed-loop automatic adjustment of the position of the workpiece by cyclically executing the detection and adjustment process until the six-degree-of-freedom deviation is within the allowable range. Automation and high precision of large workpiece clamping and positioning are achieved, and the device is suitable for precise positioning of large heavy workpieces such as train chassis.

Description

Technical Field

[0001] This invention belongs to the field of machining clamping and positioning technology, specifically relating to an automated workpiece clamping system and control method. Background Technology

[0002] In the field of machining, the clamping and positioning of large workpieces is a critical step affecting machining quality. Heavy and bulky workpieces such as train chassis, ship components, wind power equipment parts, and aerospace structural components need to be precisely fixed on fixtures during machining to ensure sufficient machining allowance for each machining surface, guaranteeing the smooth execution of processes such as drilling, tapping, milling, boring, and cutting. Positional deviations of the workpiece on the fixture directly affect machining accuracy and can even lead to insufficient machining allowance and the production of scrap.

[0003] The position and orientation of a rigid body in three-dimensional space are described by six independent parameters: translational degrees of freedom along the X, Y, and Z coordinate axes, and rotational degrees of freedom about the X, Y, and Z coordinate axes, collectively known as the six degrees of freedom. Precise positioning of large workpieces requires simultaneous control of deviations in all six degrees of freedom; any deviation exceeding the allowable range will affect the machining quality. Therefore, the clamping and positioning of large workpieces is essentially a six-degree-of-freedom positioning problem.

[0004] Existing methods for clamping and positioning large workpieces mainly include manual scribing positioning and fixed fixture positioning. Manual scribing positioning relies on the operator's experience and skill, using scribing tools to draw reference lines on the workpiece surface, and then manually measuring and adjusting to bring the workpiece to the predetermined position. This method is inefficient, and its positioning accuracy is greatly affected by human factors, making it difficult to meet the requirements of high-precision machining. Fixed fixture positioning uses pre-designed fixtures to position the workpiece; however, due to manufacturing tolerances and dimensional differences between different workpieces, fixed fixtures are difficult to adapt to these differences, easily leading to positioning deviations.

[0005] In workpiece support, traditional methods typically employ four-point or multi-point support structures. However, according to spatial geometry principles, three non-collinear points define a unique plane. When using four-point support, if the four support points are not strictly coplanar, over-positioning problems will occur. Over-positioning causes additional constraint forces on the workpiece, resulting in uneven distribution of support forces or even workpiece deformation, affecting machining accuracy and workpiece quality. Current technologies lack effective solutions to eliminate the over-positioning problem in multi-point support systems.

[0006] Furthermore, most existing workpiece positioning methods are open-loop control methods, meaning that operators adjust the workpiece position based on measurement results, and then remeasure and verify the adjustment, repeating this process until the requirements are met. This open-loop control method is inefficient and has a low degree of automation, making it difficult to meet the high efficiency and high precision requirements of modern manufacturing.

[0007] Therefore, there is an urgent need for a large workpiece clamping system and method that can automatically detect workpiece position deviation, automatically adjust workpiece posture, and has closed-loop control function. Summary of the Invention

[0008] To address the problems existing in the background art, the present invention provides an automated workpiece clamping system, including a clamping base, a scribing detection unit, an image acquisition unit, a hydraulic adjustment unit, and a control unit; The fixture base is fixed on the worktable to support the workpiece; an XYZ three-axis rectangular coordinate system is established on the fixture base, with the X-axis along the longitudinal direction of the workpiece, the Y-axis along the transverse direction of the workpiece, and the Z-axis along the vertical direction. The scribing inspection unit includes multiple positioning areas set on the surface of the workpiece and scribing tools corresponding to each positioning area; the positioning areas include Y-direction positioning areas set at the four corners of the upper surface of the workpiece. , , , Positioning areas are set on two opposite sides of the workpiece in the X direction. , And the Z-direction positioning area set at the bottom of the four corners of the workpiece's bottom surface. , , , Each positioning area is coated with a white powder layer; the scribing tool is fixedly mounted on the fixture base by a bracket, and the position of the scribing tool relative to the fixture base is fixed; The image acquisition unit includes industrial cameras that are set up one-to-one with each positioning area; industrial cameras , , , Each facing the positioning area , , , Settings, industrial camera , Each facing the positioning area , Settings, industrial camera , , , Each facing the positioning area , , , Settings: The optical axis of each industrial camera is perpendicular to the surface of the corresponding positioning area; The hydraulic adjustment unit includes an X-direction hydraulic cylinder group, a Y-direction hydraulic cylinder group, a Z-direction hydraulic cylinder group, and a hydraulic connector; the X-direction hydraulic cylinder group includes hydraulic cylinders. and The hydraulic cylinders are respectively positioned at both ends of the workpiece along the X direction, used to clamp and push the workpiece to move along the X direction; the Y-direction hydraulic cylinder assembly includes hydraulic cylinders. and The hydraulic cylinders are respectively positioned on both sides of the workpiece along the Y direction to clamp and push the workpiece to move along the Y direction; the Z-direction hydraulic cylinder assembly includes hydraulic cylinders. , , , The piston rods of the four hydraulic cylinders respectively support the bottom surface of the workpiece. , , , The location of the positioning area; the hydraulic connector connects to the hydraulic cylinder. and The rodless chamber allows the hydraulic cylinder to... and Linkage; each hydraulic cylinder is equipped with a servo hydraulic valve and a displacement sensor; The control unit includes a host computer and a slave computer; the host computer is connected to each industrial camera for image acquisition and processing, deviation calculation and adjustment; the slave computer is electrically connected to each servo hydraulic valve and displacement sensor for controlling the hydraulic cylinder action and acquiring displacement signals; the host computer and the slave computer are connected via a communication line.

[0009] In the preferred embodiment, the hydraulic connector is a connection to a hydraulic cylinder. rodless chamber and hydraulic cylinder Rodless cavity piping; when the workpiece is in contact with the hydraulic cylinder Piston rod pressure Greater than the hydraulic cylinder Piston rod pressure At that time, hydraulic oil flows from the hydraulic cylinder The rodless chamber flows to the hydraulic cylinder via the hydraulic connector. rodless chamber, hydraulic cylinder The piston rod descends, the hydraulic cylinder The piston rod rises until... equal Hydraulic cylinder , Hydraulic cylinders linked via hydraulic connectors and It forms a three-point support.

[0010] In the preferred embodiment, the hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side, hydraulic cylinder and The difference in the amount of thrust along the X direction is used to adjust the rotation angle of the workpiece about the Z axis; hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side view, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece side.

[0011] In the preferred scheme, the positioning area and Diagonally distributed, positioning area and Used to detect translational deviation in the Y direction and rotational deviation around the Z axis; positioning area and Diagonally distributed, positioning area , , , Used to detect translational deviation in the Z direction, rotational deviation around the X axis, and rotational deviation around the Y axis; positioning area and Used to detect translational deviation in the X direction and verify rotational deviation around the Z axis.

[0012] This invention also provides an automated workpiece clamping control method, comprising the following steps: S1, Workpiece loading and initial positioning: The workpiece is hoisted onto the fixture base, and the bottom surface of the workpiece is controlled by a hydraulic cylinder. , , , The piston rod supports the hydraulic cylinder. and Initial positioning is achieved by automatically balancing the pressure through a hydraulic connector. S2, Positioning area preparation and scribing: Apply a white powder layer to each positioning area, and control the scribing tool to scribing the detection line on the white powder layer of each positioning area; S3, Image Acquisition and Coordinate Extraction: Trigger each industrial camera to synchronously acquire scribing images, process the images and extract features to obtain the measured coordinates of each positioning area scribing line in the fixture coordinate system; S4, Deviation Calculation: Compare the measured coordinates of each positioning zone line with the pre-calibrated standard coordinates to calculate the six degrees of freedom deviation of the workpiece, including the X-direction translation deviation. Y-direction translational deviation Z-direction translational deviation Rotational deviation around the X-axis Rotational deviation around the Y-axis Rotational deviation around the Z-axis ; S5, Deviation Judgment: Determine whether all six degrees of freedom deviations are within the allowable range, i.e., determine... , , , , , Whether they are both true; among them, , , These are the absolute values ​​of the translational deviations in the X, Y, and Z directions, respectively. , , These are the absolute values ​​of the rotational deviations around the X, Y, and Z axes, respectively. The translation deviation threshold is set to approximately 0.1 mm. The rotational deviation threshold is determined based on the workpiece size. The conversion is as follows: If all the above conditions are met, proceed to step S8; otherwise, proceed to step S6. S6, Adjustment Execution: Calculate the adjustment amount of each hydraulic cylinder based on the six degrees of freedom deviation, control the servo hydraulic valve to drive the hydraulic cylinder action, and adjust the workpiece position; Hydraulic cylinder and Automatic balancing is achieved during the adjustment process via a hydraulic connector; S7, Cyclic Adjustment: Return to step S3 and repeat steps S3 to S6 until all six degrees of freedom deviations are within the allowable range; S8, Positioning Complete: Outputs a positioning complete signal.

[0013] Furthermore, step S1 includes the following sub-steps: S11, Control hydraulic cylinder , , , The piston rod extends to the initial support position; S12, hoist the workpiece above the fixture base, and lower the workpiece so that its bottom surface rests on the hydraulic cylinder. , , , On the piston rod, the weight of the workpiece acts on each piston rod to generate supporting pressure; S13, hydraulic cylinder and The rodless cavity is connected via a hydraulic connector, and when the workpiece moves against the hydraulic cylinder... Piston rod pressure With hydraulic cylinder Piston rod pressure When the hydraulic oil flows from the high-pressure side to the low-pressure side in the hydraulic connector, the hydraulic cylinder... and The piston rod automatically adjusts its height until equal To make the hydraulic cylinder , and linked hydraulic cylinder and This forms a three-point support, eliminating the over-positioning caused by a four-point support.

[0014] Furthermore, step S3 includes the following sub-steps: S31, control unit triggers industrial camera , , , , , , , , , Simultaneously acquire line images of each positioning area; S32 performs preprocessing on the acquired image, including extracting the region of interest, grayscale equalization, filtering and denoising, and binarization; S33 employs an edge detection algorithm to detect the edges of the drawn lines, and a line fitting algorithm to extract the center line of the drawn lines, calculating the pixel coordinates of the feature points of the drawn lines. ;in, The horizontal pixel coordinates of the feature point in the image; The vertical pixel coordinates of the feature point in the image; S34 converts the pixel coordinates into physical coordinates in the fixture coordinate system according to the pre-calibrated camera parameters, and obtains the measured coordinates of each positioning zone line.

[0015] Furthermore, the calculation of the six-degree-of-freedom deviation in step S4 includes the following sub-steps: S41, Calculate the translational deviation in the Y direction. Read the location area Measured value of the Y-coordinate of the line and standard value Read the location area Measured value of the Y-coordinate of the line and standard value According to the formula Calculate; where, The translational deviation in the Y direction is expressed in mm. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; S42, Calculate the rotational deviation around the Z-axis Read the location area and Distance in the X direction According to the formula Calculate; where, The deviation is the rotational deviation about the Z-axis, and the unit is rad. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area and Distance in the X direction, in mm; S43, Calculate the translational deviation in the X direction. Read the location area Measured value of the X-coordinate of the line and standard value Read the location area Measured value of the X-coordinate of the line and standard value According to the formula Calculate; where, The translational deviation in the X direction is expressed in mm. For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; S44, Check rotational deviation around the Z-axis Read the location area and Distance in the Y direction According to the formula Calculate the verification value ;in, This is the check value for rotational deviation around the Z-axis, in rad. For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area and The distance in the Y direction, in mm; if and An alarm will sound if the absolute value of the difference exceeds a preset threshold. S45, Calculate the translational deviation in the Z direction. Read the location area , , , Measured value of the Z-coordinate of the line , , , and standard value , , , According to the formula Calculate; where, The Z-direction translational deviation is expressed in mm. , , , The respective positioning areas , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , The standard value of the Z-coordinate for the line drawing, in mm; S46, Calculate the rotational deviation around the X-axis Read the front row positioning area , With rear seat positioning area , Distance in the Y direction According to the formula Calculate; where, The deviation is the rotational deviation about the X-axis, and the unit is rad. , , , The respective positioning areas , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , The standard value of the Z-coordinate for the line drawing, in mm; For the front row positioning area , With rear seat positioning area , Distance in the Y direction, in mm; S47, Calculate the rotational deviation around the Y-axis Read the left positioning area , With the right positioning area , Distance in the X direction According to the formula Calculate; where, The deviation in rotation about the Y-axis is expressed in rad. , , , The respective positioning areas , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , The standard value of the Z-coordinate for the line drawing, in mm; Left positioning area , With the right positioning area , The distance in the X direction, in mm.

[0016] Furthermore, step S6 includes the following sub-steps: S61, Calculate the adjustment amount of the hydraulic cylinder in the X direction: Read the hydraulic cylinder... Distance from the point of application to the center of the workpiece in the Y direction Read the hydraulic cylinder Distance from the point of application to the center of the workpiece in the Y direction According to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; The translational deviation in the X direction is expressed in mm. The deviation is the rotational deviation about the Z-axis, and the unit is rad. hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm; S62, Calculate the adjustment amount of the hydraulic cylinder in the Y direction: according to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; The translational deviation in the Y direction is expressed in mm. S63, Calculate the Z-direction hydraulic cylinder adjustment amount: Read the hydraulic cylinder... Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder and The distance in the Y direction from the midpoint of the line connecting the workpiece centers. According to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder and The amount of linkage adjustment; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder and The linkage adjustment amount is in mm; The Z-direction translational deviation is expressed in mm. The deviation is the rotational deviation about the X-axis, and the unit is rad. The deviation in rotation about the Y-axis is expressed in rad. hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder and The distance from the midpoint of the line to the center of the workpiece in the Y direction, in mm; S64, the control unit sends displacement commands to each servo hydraulic valve, driving the piston of each hydraulic cylinder to move by the corresponding adjustment amount; hydraulic cylinder and During the adjustment process, automatic balancing is achieved through a hydraulic connector, eliminating the impact on the hydraulic cylinders during adjustment around the Y-axis. and Over-constraint.

[0017] Furthermore, before performing step S1, a standard coordinate calibration step is also included: A1, Camera Calibration: Perform intrinsic and extrinsic parameter calibration on each industrial camera to establish the mapping relationship between image pixel coordinates and fixture coordinate system; A2, Standard coordinate calibration: Clamp the standard workpiece onto the fixture base, use measuring equipment to precisely adjust the standard workpiece to the standard position, apply a white powder layer to each positioning area, control the scribing tool to scribing, use measuring equipment to measure the coordinates of each scribing line in the workpiece coordinate system and record them as standard coordinates; A3, Standard Image Acquisition: Each industrial camera acquires line images of each positioning area at a standard position and stores them as a standard image template.

[0018] The beneficial effects achieved by this invention are as follows: This invention employs a combination of scribing inspection and machine vision to achieve non-contact detection of six-degree-of-freedom (DOF) positional deviations of a workpiece. The scribing tool is fixed in position relative to the fixture base, and the position of the detection line scribed in the workpiece positioning area within the fixture coordinate system remains constant each time. However, due to differences in the clamping positions of different workpieces, the position of the detection line on the workpiece varies accordingly. By acquiring scribing images of each positioning area using an industrial camera and performing image processing, the scribing position coordinates can be accurately extracted and compared with pre-calibrated standard coordinates to calculate the six-DOF deviation of the workpiece. This detection method is unaffected by the surface condition and shape complexity of the workpiece, ensuring stable and reliable detection. Furthermore, by arranging multiple positioning areas at different locations, comprehensive detection of deviations in all six degrees of freedom is achieved. Simultaneously, this invention improves the reliability of the measurement results by calculating the same rotational deviation from positioning areas in different directions and comparing and verifying the results.

[0019] This invention uses a hydraulic connector to connect the rodless chambers of two hydraulic cylinders in a Z-direction hydraulic cylinder group, creating a linkage between the two cylinders and fundamentally solving the over-positioning problem of four-point support. When a workpiece is placed on the piston rods of the four Z-direction hydraulic cylinders, if the pressure of the workpiece on each piston rod is unequal, hydraulic oil will automatically flow between the two connected hydraulic cylinders. The piston rod on the high-pressure side descends, and the piston rod on the low-pressure side rises until the pressure on both sides reaches equilibrium. In this way, two of the four support points are equivalent to one support point through the hydraulic connector, forming a three-point support structure together with the other two independent support points. Three-point support conforms to the geometric principle that three points determine a plane, eliminating the over-positioning problem and avoiding workpiece deformation or uneven distribution of support force due to over-constraint. This ensures the stability and positioning accuracy of the workpiece during adjustment.

[0020] This invention achieves precise adjustment of the workpiece's six-degree-of-freedom pose through the coordinated control of multiple sets of hydraulic cylinders. The X-axis hydraulic cylinder group, through differential control of two cylinders, enables both translation along the X-axis and slight rotation around the Z-axis. The Y-axis hydraulic cylinder group, through synchronous control of two cylinders, enables translation along the Y-axis. The Z-axis hydraulic cylinder group, through coordinated control of four cylinders, enables translation along the Z-axis and slight rotation around both the X and Y axes. Each hydraulic cylinder is equipped with a servo hydraulic valve and a displacement sensor. The servo hydraulic valve precisely adjusts the cylinder's displacement based on control signals, while the displacement sensor provides real-time feedback of the piston position, forming a closed-loop control of the hydraulic cylinder position and ensuring the accuracy and controllability of the adjustment action.

[0021] This invention establishes a closed-loop control system for detection, calculation, and adjustment, achieving automated adjustment of workpiece positioning. The control unit adopts a hierarchical architecture of upper and lower computers. The upper computer is responsible for image acquisition, image processing, deviation calculation, and adjustment calculation, while the lower computer is responsible for the position control and safety interlocking of the hydraulic cylinder. The system gradually reduces the positioning deviation by cyclically executing the processes of image acquisition, deviation calculation, and adjustment execution until all six degrees of freedom deviations are within the allowable range. The closed-loop control method is adaptive; even with various errors and interference factors, as long as they are within the system's adjustment range, the target position can be reached through multiple iterations. This significantly improves the efficiency and accuracy of clamping and positioning, reduces manual intervention, and meets the automation and intelligence requirements of modern manufacturing. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the front view structure of an automated workpiece clamping system according to the present invention; Figure 2 This is a rear-view structural diagram of an automated workpiece clamping system according to the present invention; Figure 3 This is a top view of the structure of an automated workpiece clamping system according to the present invention, showing an unclamped workpiece. Figure 4 This is a control principle diagram of an automated workpiece clamping system according to the present invention.

[0023] Figure 5 This is the control principle diagram of hydraulic cylinders HZ1, HZ2, HZ3, and HZ4. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Reference Figures 1-3 The automated workpiece clamping system provided by this invention includes a fixture base, a scribing and detection unit, an image acquisition unit, a hydraulic adjustment unit, and a control unit. These components work together through mechanical connections, hydraulic lines, and electrical signal circuits to achieve precise positioning and automatic adjustment of large workpieces on the fixture.

[0026] The fixture base is the fundamental support structure of the entire system. Made of high-rigidity material, it is securely mounted to the worktable using anchor bolts or other fixing methods. The main function of the fixture base is to provide a stable support platform for the workpiece and also serve as the mounting carrier for other units. An XYZ three-axis Cartesian coordinate system is established on the fixture base as the reference coordinate system for the entire system. The X-axis extends along the longitudinal direction of the workpiece (length), the Y-axis extends along the transverse direction of the workpiece (width), and the Z-axis extends vertically upwards, perpendicular to the worktable surface. This coordinate system provides a unified reference for subsequent position detection and deviation calculation; all position measurements and adjustment calculations are performed within this coordinate system.

[0027] The scribing inspection unit consists of two parts: multiple positioning areas set on the workpiece surface and scribing tools corresponding to each positioning area. The positioning areas are specific regions pre-defined on the workpiece surface, used to coat with a white powder layer and receive scribing marks. Based on the six-degree-of-freedom positioning requirements, the positioning areas are divided into 3 groups of 10 according to their inspection functions. The first group is the Y-direction positioning area, including positioning areas located at the four corners of the workpiece's upper surface. , , , The first group is used to detect translational deviation in the Y direction and rotational deviation around the Z axis. The second group is the X-direction positioning area, which includes positioning areas set on two opposite sides of the workpiece. and This is used to detect translational deviation in the X direction and to verify rotational deviation around the Z axis. The third group is the Z-direction positioning area, which includes positioning areas located at the bottom of the sides corresponding to the four corners of the workpiece's bottom surface. , , , This system is used to detect translational deviation in the Z direction, rotational deviation around the X-axis, and rotational deviation around the Y-axis. The Z-axis positioning area is located on the bottom side rather than the bottom surface of the workpiece to facilitate image acquisition from the side, avoiding the difficulty of taking pictures from below the workpiece. Each positioning area is coated with a white powder layer. The purpose of the white powder layer is to provide a high-contrast background; when the scribing tool scribes the detection line on its surface, the dark scribing line contrasts sharply with the white background, making it easier for the industrial camera to clearly capture the scribing image. The white powder layer can be made of industrial white powder, lime powder, or other suitable coating materials.

[0028] The scribing tool is fixedly mounted on the fixture base via a bracket. The position of the scribing tool relative to the fixture base is fixed; that is, the coordinates of the scribing tool in the fixture coordinate system are constant each time a scribing is performed. Because the position of the scribing tool is fixed while the position of the workpiece varies with each clamping, the position of the inspection line scribed by the scribing tool relative to different workpieces will be different. By detecting the deviation of the scribing position relative to the standard position, the deviation of the workpiece relative to the standard position can be determined.

[0029] The image acquisition unit includes industrial cameras, each corresponding to one of the positioning areas. These industrial cameras are high-resolution digital cameras specifically designed for industrial visual inspection, featuring high definition, high frame rate, and stable reliability, making them suitable for long-term operation in industrial environments. Based on the distribution of the 10 positioning areas, the image acquisition unit is configured with 10 industrial cameras. , , , Each facing the positioning area , , , This setting is used to acquire scribing images of the four corner positioning areas on the upper surface of the workpiece. (Industrial camera) , Each facing the positioning area , This setting is used to acquire scribing images of the positioning areas on both sides of the workpiece. (Industrial camera) , , , Each facing the positioning area , , , The settings are used to acquire scribing images of the four positioning areas on the bottom side of the workpiece.

[0030] Each industrial camera's optical axis is perpendicular to the surface of its corresponding positioning area. The optical axis is the main optical axis of the camera lens; when the optical axis is perpendicular to the surface of the object being photographed, the image with minimal distortion and highest accuracy can be obtained. Each industrial camera is mounted on a fixture base or independent support structure via a bracket. The mounting position is precisely adjusted to ensure that the camera maintains a suitable working distance and optimal shooting angle with its corresponding positioning area.

[0031] The hydraulic adjustment unit is the actuator for adjusting the position of the workpiece, including the X-direction hydraulic cylinder group, the Y-direction hydraulic cylinder group, the Z-direction hydraulic cylinder group, and the hydraulic connector.

[0032] The X-direction hydraulic cylinder assembly includes hydraulic cylinders. and Hydraulic cylinder and These are respectively positioned at both ends of the workpiece along the X direction, used to clamp and push the workpiece to move along the X direction. Hydraulic cylinders. Set in the positioning area Nearby and clamping the workpiece Side, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side. When the hydraulic cylinder and When the hydraulic cylinder extends and retracts synchronously in the same direction, it can achieve translation of the workpiece along the X-axis. and When there is a difference in the amount of pushing along the X direction, the rotation angle of the workpiece around the Z axis can be adjusted, thus achieving a small rotation of the workpiece in the horizontal plane.

[0033] The Y-direction hydraulic cylinder assembly includes hydraulic cylinders. and Hydraulic cylinder and These are respectively positioned on both sides of the workpiece along the Y-direction, used to clamp and push the workpiece to move along the Y-direction. Hydraulic cylinders. Set in the positioning area Nearby and clamping the workpiece Side view, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side view. Two hydraulic cylinders work together to achieve translation of the workpiece along the Y-axis.

[0034] Z-direction hydraulic cylinder assembly includes hydraulic cylinders , , , There are a total of 4 hydraulic cylinders. Each of the 4 cylinders has a support tray on top of its piston rod, which supports the bottom surface of the workpiece accordingly. , , , The position of the positioning area. The weight of the workpiece is supported by the piston rods of four hydraulic cylinders. By adjusting the extension of the piston rods of each hydraulic cylinder, the workpiece can be translated along the Z-axis and rotated slightly around the X-axis and Y-axis.

[0035] Hydraulic connector connects to hydraulic cylinder and The rodless chamber allows the hydraulic cylinder to... and Linkage. A hydraulic connector is a section of piping that connects the hydraulic cylinders. rodless chamber and hydraulic cylinder The rodless chambers are connected, forming a single, interconnected hydraulic cavity between the two hydraulic cylinders. When the workpiece moves against the hydraulic cylinder... Piston rod pressure Greater than the hydraulic cylinder Piston rod pressure At that time, the hydraulic cylinder The oil pressure in the rodless chamber is higher than that in the hydraulic cylinder. The oil pressure in the rodless chamber, hydraulic oil from the hydraulic cylinder The rodless chamber flows to the hydraulic cylinder via the hydraulic connector. The rodless chamber. During the flow of hydraulic oil, the hydraulic cylinder... The piston rod descends, the hydraulic cylinder The piston rod rises until... equal This hydraulic cylinder , Hydraulic cylinders linked via hydraulic connectors and This three-point support effectively eliminates the over-positioning problem that may occur with four-point support.

[0036] Each hydraulic cylinder is equipped with a servo hydraulic valve and a displacement sensor. The servo hydraulic valve is a high-precision hydraulic control component that precisely controls the flow and direction of hydraulic oil based on the input electrical signal, thereby achieving precise control of the hydraulic cylinder piston position. The displacement sensor is installed on each hydraulic cylinder to detect the piston position in real time and feeds the position signal back to the control unit, forming a closed-loop control system.

[0037] The control unit is the central control hub of the entire system, comprising a host computer and slave computers. The host computer communicates with each industrial camera to acquire and process images, calculate deviations, and make adjustments. The host computer can be an industrial computer or other high-performance computing device, running image processing software and control algorithms. The host computer connects to each industrial camera via an image acquisition interface or a network interface, triggering the cameras to take pictures and receiving the image data acquired by the cameras.

[0038] The lower-level computer is electrically connected to each servo hydraulic valve and displacement sensor to control the hydraulic cylinder's movement and collect displacement signals. The lower-level computer can be a programmable logic controller (PLC) or other industrial controller. It receives adjustment commands from the upper-level computer, converts them into control signals for the servo hydraulic valves, and drives the hydraulic cylinders. Simultaneously, the lower-level computer collects feedback signals from each displacement sensor to achieve closed-loop control of the hydraulic cylinder position.

[0039] The host computer and the slave computer are connected via a communication line. This communication line can be an industrial Ethernet network, a serial communication line, or other industrial communication methods. The host computer sends the calculated adjustment values ​​for each hydraulic cylinder to the slave computer, and the slave computer feeds back the actual position information of each hydraulic cylinder to the host computer, thus achieving data exchange and coordinated control between the two systems.

[0040] Reference Figures 4-5 This invention also provides an automated workpiece clamping control method, implemented based on the aforementioned system, which mainly includes two stages: standard coordinate calibration and workpiece positioning adjustment. Before formally positioning the workpiece, the standard coordinate calibration must be completed to establish a detection benchmark. Then, a positioning adjustment process is performed on each workpiece to bring it to the standard position.

[0041] Before executing the workpiece positioning and adjustment process, the standard coordinates must be calibrated. The calibration process includes three steps: camera calibration, standard coordinate calibration, and standard image acquisition.

[0042] Step A1 is camera calibration. Intrinsic and extrinsic parameter calibrations are performed on each industrial camera to establish the mapping relationship between image pixel coordinates and the fixture coordinate system. Intrinsic parameter calibration determines the camera's internal parameters, including focal length, principal point position, and distortion coefficients. These parameters describe the camera's inherent characteristics in projecting three-dimensional spatial points onto a two-dimensional image plane. Extrinsic parameter calibration determines the camera's position and orientation relative to the fixture coordinate system, including translation vectors and rotation matrices. Using intrinsic and extrinsic parameters, pixel coordinates in the image can be converted to physical coordinates in the fixture coordinate system. Camera calibration can employ the Zhang Zhengyou calibration method or other mature calibration methods, using a calibration board as the calibration tool. By acquiring images of the calibration board at different positions and orientations, the camera parameters are calculated.

[0043] Step A2 is the standard coordinate calibration. The standard workpiece is clamped onto the fixture base, and a measuring device is used to precisely adjust the workpiece to its standard position. The standard position refers to the ideal position of the workpiece on the fixture, where the workpiece coordinate system and the fixture coordinate system have a definite relative relationship. The measuring device can be a coordinate measuring machine, laser tracker, or other high-precision measuring instruments. After the standard workpiece is in the standard position, a white powder layer is applied to each positioning area. A scribing tool is used to scribing lines, and the coordinates of each scribing line in the workpiece coordinate system are measured and recorded as standard coordinates. The standard coordinates are the reference for subsequent deviation calculations, representing the correct positions of the scribing lines in each positioning area when the workpiece is in the standard position.

[0044] Step A3 involves standard image acquisition. Each industrial camera acquires line images of each positioning area at the standard location and stores them as standard image templates. These standard image templates can be used for template matching and feature comparison in subsequent image processing, and can also serve as a basis for verifying the mapping relationship between image coordinates and physical coordinates.

[0045] The workpiece positioning and adjustment process is a positioning operation performed for each workpiece to be processed, including eight steps: workpiece loading and initial positioning, positioning area preparation and marking, image acquisition and coordinate extraction, deviation calculation, deviation judgment, adjustment execution, cyclic adjustment and positioning completion.

[0046] Step S1: Workpiece loading and initial positioning; Step S1 involves loading and initially positioning the workpiece. The workpiece is hoisted onto the fixture base, with the bottom surface of the workpiece positioned by a hydraulic cylinder. , , , The piston rod supports it. Hydraulic cylinder. and The hydraulic connector automatically balances the pressure to complete the initial positioning.

[0047] Step S1 specifically includes the following sub-steps. Sub-step S11 is controlling the hydraulic cylinder. , , , The piston rod extends to the initial support position. The initial support position is a pre-set piston rod extension amount, which positions the four support trays at a suitable height to facilitate receiving the workpiece to be clamped.

[0048] Sub-step S12 involves hoisting the workpiece above the fixture base and lowering the workpiece so that its bottom surface rests on the hydraulic cylinder. , , , The workpiece is placed on the piston rod. It can be lifted using a crane, gantry crane, or other lifting equipment. During the lowering process, the workpiece's weight acts on each piston rod, generating supporting pressure.

[0049] Sub-step S13 is a hydraulic cylinder and The rodless chamber is connected via a hydraulic connector. When the workpiece moves against the hydraulic cylinder... Piston rod pressure With hydraulic cylinder Piston rod pressure When the pressure difference is not significant, hydraulic oil flows from the high-pressure side to the low-pressure side in the hydraulic connector. Hydraulic cylinder. and The piston rod automatically adjusts its height until equal .exist and After reaching equilibrium, the hydraulic cylinder , and linked hydraulic cylinder and This constitutes a three-point support. According to the principles of spatial geometry, three non-collinear points determine a unique plane, therefore, three-point support does not have the problem of over-positioning. However, with four-point support, if the four support points are not coplanar, over-constraint will occur, leading to uneven stress on the workpiece or even deformation. A hydraulic connector is used to... and The linkage is equivalent to transforming 4-point support into 3-point support, fundamentally eliminating the over-positioning problem of 4-point support.

[0050] Step S2: Preparation and marking of the positioning area; Step S2 involves preparing and marking the positioning area. A white powder layer is applied to each positioning area, and the marking tool is used to draw detection lines on the white powder layer in each positioning area.

[0051] The white powder layer can be applied manually or automatically by spraying. The coating thickness should be moderate; too thin and the contrast will be insufficient, too thick and the clarity of the scribing may be affected. A thickness of 2 to 3 mm is preferred. The scribing tool scribes the detection lines on the white powder layer. The detection lines can be single lines or cross lines. The dark scribing lines contrast sharply with the white powder background, facilitating subsequent image acquisition and feature extraction.

[0052] Step S3: Image Acquisition and Coordinate Extraction; Step S3 involves image acquisition and coordinate extraction. Each industrial camera is triggered to synchronously acquire images of the graffiti lines. The images are then processed and features are extracted to obtain the measured coordinates of each graffiti line in the fixture coordinate system.

[0053] Step S3 specifically includes the following sub-steps. Sub-step S31 involves the control unit triggering the industrial camera. , , , , , , , , , Simultaneously acquire images of the marking areas. Synchronization can be triggered by hardware trigger signals or software trigger commands, ensuring that all 10 cameras complete image acquisition at the same time, avoiding image inconsistencies caused by workpiece micro-movements or environmental changes.

[0054] Sub-step S32 involves preprocessing the acquired image, including extracting the region of interest (ROI), grayscale equalization, filtering and denoising, and binarization. The ROI is the region in the image containing line information; extracting the ROI reduces the amount of data needed for subsequent processing and eliminates background interference. Grayscale equalization is an image enhancement technique that adjusts the grayscale distribution of the image to make the image contrast more uniform. Filtering and denoising uses digital filters to remove random noise from the image; common filtering methods include Gaussian filtering and median filtering. Binarization converts the grayscale image into a binary image with only black and white values, facilitating subsequent edge detection and feature extraction.

[0055] Sub-step S33 involves detecting the edges of the drawn line using an edge detection algorithm, extracting the center line of the drawn line using a line fitting algorithm, and calculating the pixel coordinates of the feature points of the drawn line. The edge detection algorithm can use the Canny operator, Sobel operator, or other edge detection operators to extract the edge contour of the drawn line from the binary image. The line fitting algorithm can use the Hough transform or least squares method to fit the edge points to a straight line equation, thus obtaining the position of the center line of the drawn line. The feature points of the drawn line can be selected as points with clear geometric meaning, such as the midpoint, endpoints, or intersections of the drawn line. The pixel coordinates of the feature points are represented as follows: ;in The horizontal pixel coordinates of the feature point in the image; represents the vertical pixel coordinates of the feature point in the image.

[0056] Sub-step S34 involves converting pixel coordinates into physical coordinates in the fixture coordinate system based on pre-calibrated camera parameters, thereby obtaining the measured coordinates of each positioning zone line. The coordinate transformation is based on the pinhole model of camera imaging and the extrinsic and extrinsic parameters obtained from calibration. First, the pixel coordinates are converted into normalized coordinates in the camera coordinate system; then, based on the extrinsic parameters, the camera coordinates are converted into physical coordinates in the fixture coordinate system. For planar targets, a unique three-dimensional coordinate can also be obtained by combining planar constraints.

[0057] Step S4: Deviation Calculation. Step S4 involves calculating the deviation. The measured coordinates of each positioning zone line are compared with the pre-calibrated standard coordinates to calculate the workpiece's six degrees of freedom deviation. The six degrees of freedom deviation includes the X-direction translational deviation. Y-direction translational deviation Z-direction translational deviation Rotational deviation around the X-axis Rotational deviation around the Y-axis Rotational deviation around the Z-axis Six degrees of freedom fully describe the position and orientation of a rigid body in three-dimensional space. By detecting these six deviations, the offset of the workpiece relative to the standard position can be fully understood.

[0058] Step S4 specifically includes the following sub-steps. Sub-step S41 is to calculate the translational deviation in the Y direction. Read the location area Measured value of the Y-coordinate of the line and standard value Read the location area Measured value of the Y-coordinate of the line and standard value Calculate using the following formula: ; in This represents the translational deviation in the Y direction, in mm. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area Standard value for the Y-coordinate of the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line is in mm. This formula is derived from the positioning area. and The average of the Y-coordinate deviations is used to obtain the overall translation of the workpiece in the Y direction. (Select...) and Calculations are performed using two diagonally distributed positioning zones, which eliminates the influence of workpiece rotation on translation measurement.

[0059] Sub-step S42 is to calculate the rotational deviation around the Z-axis. Read the location area and Distance in the X direction Calculate using the following formula: ; in The deviation around the Z-axis is expressed in rad. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area Standard value for the Y-coordinate of the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area Standard value for the Y-coordinate of the line, in mm; For positioning area and The distance in the X direction is measured in mm. The principle behind this formula is: when the workpiece rotates around the Z-axis, the positioning area... and The displacement in the opposite direction is generated in the Y direction. The difference in displacement divided by the arctangent of the distance between the two points is the rotation angle.

[0060] Sub-step S43 is to calculate the translational deviation in the X direction. Read the location area Measured value of the X-coordinate of the line and standard value Read the location area Measured value of the X-coordinate of the line and standard value Calculate using the following formula: ; in This represents the translational deviation in the X direction, in mm. For positioning area The measured X-coordinate value of the line, in mm; For positioning area Standard X-coordinate value for the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate for the scribe line, in mm. This is achieved by defining the positioning area. and The average deviation of the X coordinate is used to obtain the translation amount of the workpiece in the X direction.

[0061] Sub-step S44 is to check the rotational deviation around the Z-axis. Read the location area and Distance in the Y direction Calculate the check value using the following formula. : ; in This is the check value for rotational deviation around the Z-axis, in rad. For positioning area The measured X-coordinate value of the line, in mm; For positioning area Standard X-coordinate value for the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area Standard X-coordinate value for the line, in mm; For positioning area and The distance in the Y direction, in mm. If and An alarm is triggered if the absolute value of the difference exceeds a preset threshold, indicating a potential system anomaly. By calculating and comparing the same rotational deviation from different directions and positioning areas, the measurement results can be cross-validated, improving measurement reliability.

[0062] Sub-step S45 is to calculate the translational deviation in the Z direction. Read the location area , , , Measured value of the Z-coordinate of the line , , , and standard value , , , Calculate using the following formula: ; in This represents the translational deviation in the Z direction, in mm. , , , Positioning area , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , The standard Z-coordinate value for the scribing is in mm. The overall translation of the workpiece in the Z-direction is obtained by averaging the Z-coordinate deviations of the four Z-direction positioning areas.

[0063] Sub-step S46 is to calculate the rotational deviation around the X-axis. Read the front row positioning area. , With rear seat positioning area , Distance in the Y direction Calculate using the following formula: ; in The deviation around the X-axis is expressed in rad. , , , The respective positioning areas , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , Standard Z-coordinate value for the line, in mm; For the front row positioning area , With rear seat positioning area , The distance in the Y direction is in mm. When the workpiece rotates around the X-axis, the front and rear positioning areas produce opposite height changes in the Z direction. The height difference divided by the arctangent of the distance between the front and rear rows is the rotation angle around the X-axis.

[0064] Sub-step S47 is to calculate the rotational deviation around the Y-axis. Read the left positioning area. , With the right positioning area , Distance in the X direction Calculate using the following formula: ; in This represents the rotational deviation about the Y-axis, in rad. , , , The respective positioning areas , , , The measured Z-coordinate value of the scribed line, in mm; , , , The respective positioning areas , , , Standard Z-coordinate value for the line, in mm; Left positioning area , With the right positioning area , The distance in the X direction is measured in mm. When the workpiece rotates around the Y-axis, the left and right positioning areas experience opposite height changes in the Z-direction. The height difference divided by the arctangent of the distance between the left and right sides is the rotation angle around the Y-axis.

[0065] Step S5: Deviation Judgment; Step S5 is the deviation judgment. It determines whether the deviations of all six degrees of freedom are within the allowable range. The allowable range is defined by a preset deviation threshold, denoted as the translation deviation threshold. The rotational deviation threshold is denoted as The judgment condition is: , , , , , Whether they are both true; among them , , These are the absolute values ​​of the translational deviations in the X, Y, and Z directions, respectively. , , These are the absolute values ​​of the rotational deviations around the X, Y, and Z axes, respectively. Translational deviation threshold. The value is determined based on the workpiece's machining accuracy requirements, and is preferably around 0.1 mm. Rotational deviation threshold. Based on workpiece size The conversion is calculated based on the principle of ensuring that the displacement of the workpiece edge caused by rotation does not exceed [a certain value]. If all the above judgment conditions are met simultaneously, it indicates that the workpiece has reached the standard position, and step S8 is executed to complete the positioning. If none of the above judgment conditions are met simultaneously, it indicates that the workpiece position still exceeds the tolerance, and step S6 is executed for adjustment. Step S6 is the adjustment execution step; step S6 is the adjustment execution step. The adjustment amount of each hydraulic cylinder is calculated based on the six degrees of freedom deviation, and the servo hydraulic valve is controlled to drive the hydraulic cylinder to move, thereby adjusting the workpiece position. Hydraulic cylinder and The system automatically balances itself during adjustment via a hydraulic connector.

[0066] Step S6 specifically includes the following sub-steps. Sub-step S61 is to calculate the adjustment amount of the hydraulic cylinder in the X direction. This involves reading the hydraulic cylinder... Distance from the point of application to the center of the workpiece in the Y direction Read the hydraulic cylinder Distance from the point of application to the center of the workpiece in the Y direction Calculate the hydraulic cylinder using the following formula. Adjustment amount: Calculate the hydraulic cylinder using the following formula. Adjustment amount: ;in hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; This represents the translational deviation in the X direction, in mm. The deviation around the Z-axis is expressed in rad. hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm. Hydraulic cylinder. and The adjustment amount is determined by the translation component. and rotational components Together, the rotational components have opposite signs, causing the two hydraulic cylinders to differentially rotate, thereby achieving the rotational adjustment of the workpiece.

[0067] Sub-step S62 calculates the adjustment amount of the hydraulic cylinder in the Y direction. The hydraulic cylinder adjustment is calculated using the following formula. Adjustment amount: Calculate the hydraulic cylinder using the following formula. Adjustment amount: ;in hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; The value represents the translational deviation in the Y direction, expressed in mm. Two hydraulic cylinders in the Y direction move synchronously and in equal amounts to achieve the translation of the workpiece along the Y-axis.

[0068] Sub-step S63 calculates the adjustment amount of the hydraulic cylinder in the Z direction. Read the hydraulic cylinder... Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder and The distance in the Y direction from the midpoint of the line connecting the workpiece centers. Calculate the hydraulic cylinder using the following formula. Adjustment amount: ; Calculate the hydraulic cylinder using the following formula. Adjustment amount: ; Calculate the hydraulic cylinder using the following formula. and Linkage adjustment amount: ; in hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder and The linkage adjustment amount is in mm; This represents the translational deviation in the Z direction, in mm. The deviation around the X-axis is expressed in rad. This represents the rotational deviation about the Y-axis, in rad. hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder and The distance from the midpoint of the line to the center of the workpiece in the Y direction, in mm. The adjustment amount of the hydraulic cylinder in the Z direction is determined by the translation component. Together with the rotation component, the rotation component is distributed according to the distance of each hydraulic cylinder from the center of the workpiece, so that the coordinated action of each hydraulic cylinder produces the desired translational and rotational motion.

[0069] Sub-step S64 involves the control unit sending displacement commands to each servo hydraulic valve, driving the piston of each hydraulic cylinder to move by the corresponding adjustment amount. (Hydraulic cylinder) and During the adjustment process, automatic balancing is achieved through a hydraulic connector, eliminating the impact on the hydraulic cylinders during adjustment around the Y-axis. and Over-constraint. Due to the hydraulic cylinder and Through hydraulic coupling, no separate control is required when adjusting the rotation around the Y-axis. and The hydraulic connector will automatically adjust the relative height of the two components to avoid over-constraint.

[0070] Step S7 is a cyclical adjustment; Step S7 is a cyclical adjustment. Return to step S3 and repeat steps S3 to S6 until all six degrees of freedom deviations are within the allowable range.

[0071] The purpose of iterative adjustment is to gradually reduce positioning deviation through multiple iterations. Due to various error factors in the system, a single adjustment may not bring all deviations within the acceptable range; therefore, repeated detection and adjustment are necessary. In each loop, images are reacquired, deviations are calculated, and adjustments are performed until all deviations meet the requirements. To prevent the system from entering an infinite loop due to anomalies, a maximum number of loops can be set. Exceeding this maximum number triggers an alarm, prompting manual intervention.

[0072] Step S8: Positioning complete. Step S8 signifies positioning completion. When all six degrees of freedom deviations are within the allowable range, a positioning completion signal is output. The positioning completion signal can be sent to the upper-level control system or operator via the control unit's output interface, indicating that the workpiece has been accurately positioned and can proceed with subsequent clamping, fixing, and processing operations. Simultaneously with outputting the positioning completion signal, the control unit can record the final deviation data for this positioning operation for quality traceability and statistical analysis.

[0073] This invention relates to an automated workpiece clamping system and control method based on six-degree-of-freedom (6DOF) positioning. It employs a combination of scribing detection and visual measurement to detect workpiece position deviations, and uses hydraulic cylinders to precisely adjust the workpiece's posture, forming a closed-loop control system of detection, calculation, and adjustment. Six-degree-of-freedom positioning refers to determining the position and orientation of a rigid body in three-dimensional space using six independent parameters, including translation along the X, Y, and Z coordinate axes and rotation around these axes. This invention, through the rational arrangement of the positioning area and scribing tools, collects scribing position information from different directions and calculates the deviations in the six degrees of freedom, achieving comprehensive detection of the workpiece's posture. By cyclically executing the detection, calculation, and adjustment process, the system gradually eliminates positioning deviations, ultimately bringing all deviations within acceptable limits. The closed-loop control is adaptive; even with various errors and interferences, as long as they remain within the system's adjustment range, the target position can be achieved through multiple iterations.

[0074] During adjustment, traditional four-point support suffers from over-positioning. When the four support points are not coplanar, the workpiece will be subjected to additional constraint forces, potentially leading to workpiece deformation or uneven distribution of support forces. This invention uses a hydraulic connector to link two hydraulic cylinders, effectively transforming the four-point support into a three-point support, fundamentally eliminating the over-positioning problem. Simultaneously, the linked two hydraulic cylinders still provide two support points, maintaining support stability and addressing both the need to eliminate over-positioning and the need for support stability.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automated workpiece clamping system, characterized in that, It includes a fixture base, a scribing detection unit, an image acquisition unit, a hydraulic adjustment unit, and a control unit; The fixture base is fixed on the worktable to support the workpiece; an XYZ three-axis rectangular coordinate system is established on the fixture base, with the X-axis along the longitudinal direction of the workpiece, the Y-axis along the transverse direction of the workpiece, and the Z-axis along the vertical direction. The scribing inspection unit includes multiple positioning areas set on the surface of the workpiece and scribing tools corresponding to each positioning area; the positioning areas include Y-direction positioning areas set at the four corners of the upper surface of the workpiece. , , , Positioning areas are set on two opposite sides of the workpiece in the X direction. , And the Z-direction positioning area set at the bottom of the four corners of the workpiece's bottom surface. , , , Each positioning area is coated with a white powder layer; the scribing tool is fixedly mounted on the fixture base by a bracket, and the position of the scribing tool relative to the fixture base is fixed; The image acquisition unit includes industrial cameras that are set up one-to-one with each positioning area; industrial cameras , , , Each facing the positioning area , , , Settings, industrial camera , Each facing the positioning area , Settings, industrial camera , , , Each facing the positioning area , , , Settings: The optical axis of each industrial camera is perpendicular to the surface of the corresponding positioning area; The hydraulic adjustment unit includes an X-direction hydraulic cylinder group, a Y-direction hydraulic cylinder group, a Z-direction hydraulic cylinder group, and a hydraulic connector; the X-direction hydraulic cylinder group includes hydraulic cylinders. and The hydraulic cylinders are respectively positioned at both ends of the workpiece along the X direction to clamp and push the workpiece to move along the X direction; the Y-direction hydraulic cylinder assembly includes hydraulic cylinders. and The hydraulic cylinders are respectively positioned on both sides of the workpiece along the Y direction to clamp and push the workpiece to move along the Y direction; the Z-direction hydraulic cylinder assembly includes hydraulic cylinders. , , , The piston rods of the four hydraulic cylinders respectively support the bottom surface of the workpiece. , , , The location of the positioning area; the hydraulic connector connects to the hydraulic cylinder. and The rodless chamber allows the hydraulic cylinder to... and Linkage; each hydraulic cylinder is equipped with a servo hydraulic valve and a displacement sensor; The control unit includes a host computer and a slave computer; the host computer is connected to each industrial camera for image acquisition and processing, deviation calculation and adjustment; the slave computer is electrically connected to each servo hydraulic valve and displacement sensor for controlling the hydraulic cylinder action and acquiring displacement signals; the host computer and the slave computer are connected via a communication line.

2. The automated workpiece clamping system according to claim 1, characterized in that, The hydraulic connector is for connecting hydraulic cylinders. rodless chamber and hydraulic cylinder Rodless cavity piping; when the workpiece is in contact with the hydraulic cylinder Piston rod pressure Greater than the hydraulic cylinder Piston rod pressure At that time, hydraulic oil flows from the hydraulic cylinder The rodless chamber flows to the hydraulic cylinder via the hydraulic connector. rodless chamber, hydraulic cylinder The piston rod descends, the hydraulic cylinder The piston rod rises until... equal Hydraulic cylinder , Hydraulic cylinders linked via hydraulic connectors and It forms a three-point support.

3. The automated workpiece clamping system according to claim 1, characterized in that, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side, hydraulic cylinder and The difference in the amount of thrust along the X direction is used to adjust the rotation angle of the workpiece about the Z axis; hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece Side view, hydraulic cylinder Set in the positioning area Nearby and clamping the workpiece side.

4. The automated workpiece clamping system according to claim 1, characterized in that, Location area and Diagonally distributed, positioning area and Used to detect translational deviation in the Y direction and rotational deviation around the Z axis; positioning area and Diagonally distributed, positioning area , , , Used to detect translational deviation in the Z direction, rotational deviation around the X axis, and rotational deviation around the Y axis; positioning area and Used to detect translational deviation in the X direction and verify rotational deviation around the Z axis.

5. A workpiece clamping control method for automated adjustment based on the system described in any one of claims 1-4, characterized in that, Includes the following steps: S1, Workpiece loading and initial positioning: The workpiece is hoisted onto the fixture base, and the bottom surface of the workpiece is controlled by a hydraulic cylinder. , , , The piston rod supports the hydraulic cylinder. and Initial positioning is achieved by automatically balancing the pressure through a hydraulic connector. S2, Positioning area preparation and scribing: Apply a white powder layer to each positioning area, and control the scribing tool to scribing the detection line on the white powder layer of each positioning area; S3, Image Acquisition and Coordinate Extraction: Trigger each industrial camera to synchronously acquire scribing images, process the images and extract features to obtain the measured coordinates of each positioning area scribing line in the fixture coordinate system; S4, Deviation Calculation: Compare the measured coordinates of each positioning zone line with the pre-calibrated standard coordinates to calculate the six degrees of freedom deviation of the workpiece, including the X-direction translation deviation. Y-direction translational deviation Z-direction translational deviation Rotational deviation around the X-axis Rotational deviation around the Y-axis Rotational deviation around the Z-axis ; S5, Deviation Judgment: Determine whether all six degrees of freedom deviations are within the allowable range, i.e., determine... , , , , , Whether they are both true; among them, , , These are the absolute values ​​of the translational deviations in the X, Y, and Z directions, respectively. , , These are the absolute values ​​of the rotational deviations around the X, Y, and Z axes, respectively. The translation deviation threshold is set to approximately 0.1 mm. The rotational deviation threshold is determined based on the workpiece size. The conversion is as follows: If all the above conditions are met, proceed to step S8; otherwise, proceed to step S6. S6, Adjustment Execution: Calculate the adjustment amount of each hydraulic cylinder based on the six degrees of freedom deviation, control the servo hydraulic valve to drive the hydraulic cylinder action, and adjust the workpiece position; Hydraulic cylinder and Automatic balancing is achieved during the adjustment process via a hydraulic connector; S7, Cyclic Adjustment: Return to step S3 and repeat steps S3 to S6 until all six degrees of freedom deviations are within the allowable range; S8, Positioning Complete: Outputs a positioning complete signal.

6. The automated workpiece clamping control method according to claim 5, characterized in that, Step S1 includes the following sub-steps: S11, Control hydraulic cylinder , , , The piston rod extends to the initial support position; S12, hoist the workpiece above the fixture base, and lower the workpiece so that its bottom surface rests on the hydraulic cylinder. , , , On the piston rod, the weight of the workpiece acts on each piston rod to generate supporting pressure; S13, hydraulic cylinder and The rodless cavity is connected via a hydraulic connector, and when the workpiece moves against the hydraulic cylinder... Piston rod pressure With hydraulic cylinder Piston rod pressure When the hydraulic oil flows from the high-pressure side to the low-pressure side in the hydraulic connector, the hydraulic cylinder... and The piston rod automatically adjusts its height until equal To make the hydraulic cylinder , and linked hydraulic cylinder and This forms a three-point support, eliminating the over-positioning caused by a four-point support.

7. The automated workpiece clamping control method according to claim 5, characterized in that, Step S3 includes the following sub-steps: S31, control unit triggers industrial camera , , , , , , , , , Simultaneously acquire line images of each positioning area; S32 performs preprocessing on the acquired image, including extracting the region of interest, grayscale equalization, filtering and denoising, and binarization; S33 employs an edge detection algorithm to detect the edges of the drawn lines, and a line fitting algorithm to extract the center line of the drawn lines, calculating the pixel coordinates of the feature points of the drawn lines. ;in, The horizontal pixel coordinates of the feature point in the image; The vertical pixel coordinates of the feature point in the image; S34 converts the pixel coordinates into physical coordinates in the fixture coordinate system according to the pre-calibrated camera parameters, and obtains the measured coordinates of each positioning zone line.

8. The automated workpiece clamping control method according to claim 5, characterized in that, The calculation of the six-degree-of-freedom deviation in step S4 includes the following sub-steps: S41, Calculate the translational deviation in the Y direction. Read the location area Measured value of the Y-coordinate of the line and standard value Read the location area Measured value of the Y-coordinate of the line and standard value According to the formula Calculate; where, This refers to the translational deviation in the Y direction, expressed in mm. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; S42, Calculate the rotational deviation around the Z-axis Read the location area and Distance in the X direction According to the formula Calculate; where, The deviation is the rotational deviation about the Z-axis, and the unit is rad. For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area The measured Y-coordinate value of the scribed line, in mm; For positioning area The standard value of the Y-coordinate for the line, in mm; For positioning area and Distance in the X direction, in mm; S43, Calculate the translational deviation in the X direction. Read the location area Measured value of the X-coordinate of the line and standard value Read the location area Measured value of the X-coordinate of the line and standard value According to the formula Calculate; where, The translational deviation in the X direction is expressed in mm. For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; S44, Check rotational deviation around the Z-axis Read the location area and Distance in the Y direction According to the formula Calculate the verification value ;in, This is the check value for rotational deviation around the Z-axis, in rad. For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area The measured X-coordinate value of the line, in mm; For positioning area The standard value of the X-coordinate of the line, in mm; For positioning area and The distance in the Y direction, in mm; if and An alarm will sound if the absolute value of the difference exceeds a preset threshold. S45, Calculate the translational deviation in the Z direction. Read the location area , , , Measured value of the Z-coordinate of the line , , , and standard value , , , According to the formula Calculate; where, The Z-direction translational deviation is expressed in mm. , , , Positioning area , , , The measured Z-coordinate value of the scribed line, in mm; , , , Positioning area , , , The standard value of the Z-coordinate for the line drawing, in mm; S46, Calculate the rotational deviation around the X-axis Read the front row positioning area , With rear seat positioning area , Distance in the Y direction According to the formula Calculate; where, The deviation is the rotational deviation about the X-axis, and the unit is rad. , , , Positioning area , , , The measured Z-coordinate value of the scribed line, in mm; , , , Positioning area , , , The standard value of the Z-coordinate for the line drawing, in mm; For the front row positioning area , With rear seat positioning area , Distance in the Y direction, in mm; S47, Calculate the rotational deviation around the Y-axis Read the left positioning area , With the right positioning area , Distance in the X direction According to the formula Calculate; where, The deviation in rotation about the Y-axis is expressed in rad. , , , Positioning area , , , The measured Z-coordinate value of the scribed line, in mm; , , , Positioning area , , , The standard value of the Z-coordinate for the line drawing, in mm; Left positioning area , With the right positioning area , The distance in the X direction, in mm.

9. The automated workpiece clamping control method according to claim 5, characterized in that, Step S6 includes the following sub-steps: S61, Calculate the adjustment amount of the hydraulic cylinder in the X direction: Read the hydraulic cylinder... Distance from the point of application to the center of the workpiece in the Y direction Read the hydraulic cylinder Distance from the point of application to the center of the workpiece in the Y direction According to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; The translational deviation in the X direction is expressed in mm. The deviation is the rotational deviation about the Z-axis, and the unit is rad. hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance from the point of application to the center of the workpiece in the Y direction, in mm; S62, Calculate the adjustment amount of the hydraulic cylinder in the Y direction: according to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; This refers to the translational deviation in the Y direction, expressed in mm. S63, Calculate the Z-direction hydraulic cylinder adjustment amount: Read the hydraulic cylinder... Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder Distance to the center of the workpiece in the X direction and distance in the Y direction Read the hydraulic cylinder and The distance in the Y direction from the midpoint of the line connecting the workpiece centers. According to the formula Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder The adjustment amount is calculated according to the formula. Calculate hydraulic cylinder and The amount of linkage adjustment; among which, hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder The adjustment amount is in mm; hydraulic cylinder and The linkage adjustment amount is in mm; The Z-direction translational deviation is expressed in mm. The deviation is the rotational deviation about the X-axis, and the unit is rad. The deviation in rotation about the Y-axis is expressed in rad. hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the X direction, in mm; hydraulic cylinder The distance to the center of the workpiece in the Y direction, in mm; hydraulic cylinder and The distance from the midpoint of the line to the center of the workpiece in the Y direction, in mm; S64, the control unit sends displacement commands to each servo hydraulic valve, driving the piston of each hydraulic cylinder to move by the corresponding adjustment amount; hydraulic cylinder and During the adjustment process, automatic balancing is achieved through a hydraulic connector, eliminating the impact on the hydraulic cylinders during adjustment around the Y-axis. and Over-constraint.

10. The automated workpiece clamping control method according to claim 5, characterized in that, Before performing step S1, a standard coordinate calibration step is also included: A1, Camera Calibration: Perform intrinsic and extrinsic parameter calibration on each industrial camera to establish the mapping relationship between image pixel coordinates and fixture coordinate system; A2, Standard coordinate calibration: Clamp the standard workpiece onto the fixture base, use measuring equipment to precisely adjust the standard workpiece to the standard position, apply a white powder layer to each positioning area, control the scribing tool to scribing, use measuring equipment to measure the coordinates of each scribing line in the workpiece coordinate system and record them as standard coordinates; A3, Standard Image Acquisition: Each industrial camera acquires line images of each positioning area at a standard position and stores them as a standard image template.

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