3D-DIC measuring system with automatic leveling and calibration functions and control method thereof

Abstract

The invention discloses a 3D-DIC measurement system with automatic leveling and calibration functions and a control method of the 3D-DIC measurement system. The system comprises an upper computer, a tension tester, a control box, a seven-axis binocular camera holder and a Bluetooth calibration platform, the seven-axis binocular camera holder comprises two cameras and a seven-axis electric control adjusting mechanism, the seven-axis electric control adjusting mechanism comprises a Y-axis module, a pitch axis module, a rolling axis module and two groups of camera adjusting structures, each group of camera adjusting structures comprises an X-axis module and a rotating shaft module, the cameras are mounted on the rotating shaft modules, and each camera is provided with an IMU (Inertial Measurement Unit); the Bluetooth calibration platform is arranged on the tension tester and comprises a control box, a calibration plate clamp and a calibration plate electric control adjusting mechanism, and the calibration plate clamp is arranged on the calibration plate electric control adjusting mechanism. The system integrates the binocular camera holder and the Bluetooth calibration platform, and has the functions of binocular vision automatic calibration and automatic leveling, 3D-DIC image acquisition, binocular camera visual angle control, calibration plate platform accurate control and the like.

Description

Technical Field

[0001] The present invention relates to the technical field related to three-dimensional digital images, and in particular to a 3D-DIC measurement system with automatic leveling and calibration functions and a control method thereof. Background Art

[0002] Three-dimensional digital image correlation (3D-DIC) is a non-contact optical measurement method based on digital image processing. It is used to measure the three-dimensional deformation and displacement of an object's surface and is widely used in fields such as materials science, mechanical engineering, and biomedicine. 3D-DIC sprays or affixes a randomly distributed speckle pattern to the surface of an object. Using a binocular stereo vision system, the technique captures images of the object before and after deformation. Correlation algorithms are then used to calculate the three-dimensional displacement and strain fields on the surface.

[0003] During the initial preparation for a 3D-DIC experiment, the camera platform must be leveled and the viewing angle adjusted. Existing technologies typically rely on manual operation, which can easily lead to viewing angle deviation, reduced measurement accuracy, increased operational complexity, and other issues. This reduces the stability and repeatability of experimental results, and wastes significant time and effort. After leveling and field of view adjustment, the 3D-DIC calibration process also relies on manual operation, requiring the experimenter to manually adjust the calibration plate at three angles before taking photos. This is not only time-consuming and laborious, but also prone to human error, affecting the accuracy and repeatability of experimental results.

[0004] In current 3D-DIC experiments, a conventional camera stand is typically used to construct a binocular vision system. Leveling, field of view, and angle adjustment of the binocular camera require manual effort. After completing these tasks, the binocular camera must be stabilized for calibration. Traditional binocular vision calibration methods typically employ manual calibration or a manual calibration plate platform. Calibration is achieved by repeatedly adjusting the calibration plate angle and capturing images of the plate at different angles to calculate the camera's internal and external parameters. This calibration method is complex and time-consuming, often requiring two people to coordinate: one to adjust the calibration plate angle and the other to capture images. This can easily introduce human error, affecting the accuracy and consistency of the calibration results. Calibration accuracy often falls short of requirements and cannot meet the precision requirements of 3D-DIC experiments. Given the current challenges of binocular camera leveling, inconvenient field of view adjustment, and complex binocular calibration in 3D-DIC experiments, which lead to labor-intensive and inefficient experimental processes, further improvements to 3D-DIC measurement systems are urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a 3D-DIC measurement system with automatic leveling and calibration functions and a control method thereof. The system is equipped with a binocular camera pan / tilt and a wireless calibration plate platform. The system has the functions of automatic binocular vision calibration and automatic leveling, 3D-DIC image acquisition, binocular camera viewing angle control, and precise control of the calibration plate platform, thereby improving the automation level and work efficiency and avoiding human operation errors.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A 3D-DIC measurement system with automatic leveling and calibration functions includes a host computer, a tensile testing machine electrically connected to the host computer, a control box, a seven-axis binocular camera gimbal, and a Bluetooth calibration platform;

[0008] The tensile testing machine is used to perform deformation testing on the test sample;

[0009] The seven-axis binocular camera gimbal is arranged opposite the tensile testing machine and is used to collect three-dimensional digital images of the test sample during the deformation test; the seven-axis binocular camera gimbal includes two cameras and a seven-axis electrically controlled adjustment mechanism electrically connected to the control box, and the seven-axis electrically controlled adjustment mechanism is used for camera leveling, field of view adjustment and angle adjustment of the two cameras, including a Y-axis module, a pitch axis module installed on the Y-axis module, a roll axis module installed on the pitch axis module and two groups of camera adjustment structures; each group of camera adjustment structures includes an X-axis module installed on the roll axis module and a rotation axis module installed on the X-axis module; the two cameras are respectively installed on the corresponding rotation axis modules; each camera is provided with an IMU unit, and the IMU unit, the controller, and the two cameras are respectively connected to the host computer for communication;

[0010] The Bluetooth calibration platform is arranged on the tensile testing machine, and the Bluetooth calibration platform includes a control box, a calibration plate clamp and an electric control adjustment mechanism for the calibration plate. The calibration plate clamp is used to clamp the calibration plate, and the calibration plate clamp is arranged on the electric control adjustment mechanism for the calibration plate. The electric control adjustment mechanism for the calibration plate is used to drive the calibration plate clamp to drive the calibration plate to move; a control chip and a Bluetooth communication module electrically connected to the control chip are arranged in the control box, and the control chip is electrically connected to the electric control adjustment mechanism for the calibration plate; the Bluetooth communication module is communicatively connected to the host computer.

[0011] Furthermore, the 3D-DIC measurement system also includes a movable lifting platform, and the seven-axis binocular camera gimbal is arranged on the lifting platform, and the lifting platform can drive the seven-axis binocular camera gimbal to move up and down as a whole.

[0012] Furthermore, the pitch axis module is slidably connected to the Y-axis module along the Y-axis, the pitch axis module is used to drive the roll axis module to perform pitch movement, and the roll axis module is used to drive the two sets of camera adjustment structures to perform roll movement; the rotation axis module is slidably connected to the X-axis module along the X-axis, and the rotation axis module is used to drive the camera to rotate.

[0013] Furthermore, the control box includes a motion controller, a power supply module and drivers for seven modules in the seven-axis electronic control adjustment mechanism; the Y-axis module includes a stepper motor, a coupling, a ball screw, a linear slide, a slider seat, a fixed base and a transmission platform, a linear slide is provided on the fixed base, a ball screw is provided in the same direction along the linear slide, the ball screw is connected to the output shaft of the stepper motor through a coupling, the stepper motor is controlled by a driver in the control box, and the stepper motor is provided at one end of the fixed base; a ball nut is sleeved on the ball screw, the slider seat is fixedly provided on the ball nut, and the slider seat is in slidable contact with the linear slide; a transmission platform is provided on the slider seat; the pitch axis module is provided on the transmission platform;

[0014] The pitch axis module includes a second stepper motor, an eccentric structure or a connecting rod mechanism, an arc-shaped guide rail, an angle scale plate, a pitch axis, a pitch platform and a second fixed base. The second fixed base is fixed to the first transmission platform of the Y-axis module, the arc-shaped guide rail is installed on the second fixed base, the second stepper motor is arranged on the second fixed base, the second stepper motor is controlled by the second driver in the control box, the output shaft of the second stepper motor is connected to the pitch platform through the eccentric structure or the connecting rod mechanism, the pitch platform cooperates with the arc-shaped guide rail through a slider or a bearing to realize rotation around the pitch axis, the angle scale plate is installed near the second fixed base or the arc-shaped guide rail to indicate the pitch angle; the roll axis module is arranged on the pitch platform;

[0015] The roll axis module differs from the pitch axis module in that a roll axis replaces the pitch axis, a roll platform replaces the pitch platform, the axial direction of the roll axis is perpendicular to the axial direction of the pitch axis, and the other structures are the same as those of the pitch axis module; the stepper motor of the roll axis module drives the roll platform to roll around the roll axis;

[0016] The X-axis modules are symmetrically arranged in two groups. The structure of each group of X-axis modules is the same as that of the Y-axis modules, except that the arrangement direction of the X-axis modules is along the X-axis direction and perpendicular to the arrangement direction of the Y-axis modules.

[0017] The rotating axis module corresponds to the X-axis module and is provided with two groups. The rotating axis module includes a stepper motor five, a rotating worktable, a transmission assembly and a support base. The support base is arranged on the transmission platform of the X-axis module. The stepper motor five is arranged on the support base. The stepper motor five is controlled by the driver five in the control box. The output shaft of the stepper motor five is connected to the vertical rotating axis of the rotating worktable through the coupling five and the transmission assembly (such as direct connection or through gears / synchronous belts); the camera is installed on the rotating worktable.

[0018] Furthermore, the IMU unit is connected to the host computer via a Bluetooth module, the controller is connected to the host computer via a network cable, and the two cameras are connected to the host computer via a USB camera cable.

[0019] Furthermore, the calibration plate electric control adjustment mechanism includes a first steering gear, a first L-shaped arm, a second steering gear, a second L-shaped arm, and a third steering gear; the first L-shaped arm and the second L-shaped arm respectively include an arm 1 and an arm 2 vertically connected;

[0020] The first servo is fixedly arranged in the control box, and is driven and connected to arm 1 of the first L-shaped arm. The second servo is fixedly arranged on the outside of arm 2 of the first L-shaped arm; arm 1 of the second L-shaped arm is arranged on the inside of arm 2 of the first L-shaped arm, and is driven and connected to the second servo; the third servo is fixedly arranged on the outside of arm 2 of the second L-shaped arm, and the calibration plate fixture is arranged on the inside of arm 2 of the second L-shaped arm, and is driven and connected to the third servo.

[0021] Furthermore, the calibration plate fixture includes a square box, left and right positioning parts and upper and lower positioning parts. The steering wheel of the third servo is fixedly connected to the back of the square box. The left and right positioning parts and the upper and lower positioning parts are both installed on the square box. The left and right positioning parts include two movable clamping parts, one on the left and one on the right, for clamping the calibration plate from the left and right directions. The upper and lower positioning parts include two movable clamping parts, one on the top and one on the bottom, for clamping the calibration plate from the top and bottom directions.

[0022] On the other hand, the present invention further provides a control method for a 3D-DIC measurement system with automatic leveling and calibration functions, which is applied to the above-mentioned 3D-DIC measurement system with automatic leveling and calibration functions, comprising:

[0023] Automatic leveling: The host computer obtains the quaternion values ​​collected by the IMU units installed on the two cameras, converts them into Euler angles through least squares fusion, and then performs Kalman filtering on the Euler angles to obtain stable roll and pitch angles. Based on these two angles, the pitch and roll axis modules of the seven-axis binocular camera gimbal are controlled to achieve leveling work in the early stage of the 3D-DIC experiment.

[0024] Automatic calibration: The host computer establishes a Bluetooth communication connection with the Bluetooth calibration platform. The host computer software programmed in QT controls the Bluetooth calibration platform via Bluetooth, causing the calibration plate's electronic control adjustment mechanism to operate, driving the calibration plate's rotation. At the same time, the two cameras of the seven-axis binocular camera gimbal take pictures, thus achieving the automatic calibration function.

[0025] After automatic calibration, the calibration images taken by the two cameras are processed by the calibration algorithm to obtain the corresponding calibration data.

[0026] Furthermore, during the automatic leveling process: if the Roll and Pitch angles are less than 0.05 degrees, the leveling is completed; otherwise, the two deflection axes of the seven-axis binocular camera gimbal are controlled according to the Roll and Pitch angles.

[0027] Furthermore, the calibration algorithm specifically includes:

[0028] Receive calibration plate parameters: receive preset calibration plate physical parameters;

[0029] Import binocular camera images: The two cameras are triggered synchronously to simultaneously capture left and right camera image pairs of the calibration plate in multiple poses, and perform image preprocessing on the images;

[0030] Left and right camera image pair processing: Perform spot detection on the left and right images, identify the feature points of the calibration plate, then sort the feature points by grayscale value, select the three feature points with the largest grayscale value, establish a new coordinate system based on the coordinate relationship of these three hollow points, uniformly convert the coordinates of the feature points of the left and right images to the new coordinate system, topologically sort the feature points according to the physical structure of the calibration plate, and establish a point pair mapping relationship;

[0031] Calibration data collection: store the 3D coordinates of paired feature points and corresponding pixel coordinates in all poses;

[0032] Parallel single-object positioning: Based on feature point data, the intrinsic parameter matrix of each camera is calculated in parallel and the monocular optimization result is output;

[0033] Binocular positioning: Using the corresponding feature point data of the left and right cameras, the binocular external parameters are solved and the stereo correction parameters are calculated to ensure that the subsequent matching pixels are on the same horizontal line;

[0034] Result output: Output complete calibration parameters, including the left and right camera intrinsic parameter matrices, distortion coefficients, binocular relative pose parameters, and stereo correction mapping matrix; evaluate the calibration accuracy through reprojection error, and trigger recalibration if it exceeds the threshold.

[0035] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the 3D-DIC measurement system with automatic leveling and calibration functions and the control method thereof provided by the present invention, the seven-axis electronically controlled adjustment mechanism (Y axis + pitch axis + roll axis + two X axes + two rotation axes) combined with the camera IMU unit to feedback posture data in real time, the upper computer dynamically controls the gimbal to achieve multi-degree-of-freedom precise leveling, automatic matching of binocular field of view, and adaptive adjustment of observation angle; the Bluetooth calibration platform is remotely controlled by the upper computer, the calibration board automatically switches between multiple postures, the binocular image synchronous acquisition is triggered, motion blur is eliminated, the calibration data is transmitted in real time, and dynamic recalibration is supported.

[0036] The present invention uses wireless communication and automated control technology to achieve automatic leveling and calibration functions, simplifying the initial leveling process, camera field of view adjustment process, and calibration process, and improving calibration accuracy. This significantly improves the efficiency of equipment setup and leveling, the accuracy and efficiency of camera adjustment, and the efficiency and accuracy of binocular vision calibration in 3D-DIC experiments. It transforms the discrete manual operations in traditional 3D-DIC experiments into an automated assembly line, achieving a breakthrough improvement in experimental efficiency while ensuring sub-pixel measurement accuracy. This provides a highly reliable full-field deformation measurement solution for fields such as material mechanics and structural engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a control principle block diagram of the 3D-DIC measurement system with automatic leveling and calibration functions of the present invention;

[0039] Figure 2 Schematic diagram of the structure of the 3D-DIC measurement system with automatic leveling and calibration functions of the present invention;

[0040] Figure 3 This is a schematic diagram of the structure of the seven-axis binocular camera gimbal of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of the Bluetooth calibration platform of the present invention;

[0042] Figure 5 This is a schematic diagram of the control box structure of the present invention;

[0043] Figure 6Schematic diagram of the structure of each module of the seven-axis binocular camera gimbal of the present invention, wherein (a) is the Y-axis module; (b) is the pitch axis module or the roll axis module; (c) is the X-axis module; (d) is the rotation axis module;

[0044] Figure 7 This is a flow chart of automatic leveling of the present invention;

[0045] Figure 8 This is the automatic calibration flow chart of the present invention;

[0046] Figure 9 This is a flow chart of image processing for binocular camera calibration of the present invention;

[0047] Figure 10 This is the operating interface of the binocular camera pan / tilt control software in the host computer of the embodiment of the present invention;

[0048] Figure 11 This is the interface for processing the calibration plate image in the host computer according to the embodiment of the present invention;

[0049] Figure 12 It is the change between the old and new coordinate systems in the calibration algorithm.

[0050] Description of reference numerals:

[0051] 1. Bluetooth calibration platform; 2. Seven-axis binocular camera gimbal; 3. Tensile testing machine; 4. Lifting platform; 5. Control box;

[0052] 101. Control box; 102. First servo; 103. First L-shaped arm; 104. Second servo; 105. Second L-shaped arm; 106. Third servo; 107. Calibration plate fixture;

[0053] 201, Y-axis module; 202, pitch axis module; 203, roll axis module; 204, camera 1 X-axis module; 205, camera 2 X-axis module; 206, camera 1 rotation axis module; 207, camera 2 rotation axis module; 208, camera 1; 209, camera 2; 210, camera 1 IMU unit; 211, camera 2 IMU unit;

[0054] 301, motion controller; 302, power module; 303, driver 1; 304, driver 2; 305, driver 3; 306, driver 4; 307, driver 5; 308, driver 6; 307, driver 7;

[0055] a-1. Stepper motor; a-2. Coupling; a-3. Ball screw; a-4. Linear guide; a-5. Slider; a-6. Slider seat; a-7. Ball nut; a-8. Fixed base; a-9. Transmission platform;

[0056] b-1, stepper motor 2; b-2, arc guide rail; b-3, fixed base 2; b-4, pitch platform;

[0057] c-1, stepper motor three; c-2, coupling three; c-3, ball screw three; c-4, linear guide two; c-5, transmission platform two; c-6, support seat; c-7, transmission platform three; c-8, ball screw four; c-9, coupling four; c-10, stepper motor four;

[0058] d-1, stepper motor five; d-2, coupling five; d-3, transmission assembly; d-4, support base; d-5, rotary worktable. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] The present invention provides a 3D-DIC measurement system with automatic leveling and calibration functions, comprising a wireless calibration device and a control system, and capable of quickly and accurately completing binocular vision calibration in 3D-DIC experiments.

[0061] Example 1

[0062] like Figures 1-6 As shown, the present invention provides a 3D-DIC measurement system with automatic leveling and calibration functions, including a host computer and a tensile testing machine 3 electrically connected to the host computer, a seven-axis binocular camera gimbal 2 and a Bluetooth calibration platform 1, and also includes a movable lifting platform 4 and a control box 5 for realizing the control function.

[0063] The tensile testing machine 3 is used to perform a deformation test on the test sample.

[0064] The seven-axis binocular camera platform 2 is arranged on a lifting platform 4, and the lifting platform 4 can drive the seven-axis binocular camera platform 2 to move up and down as a whole.

[0065] The seven-axis binocular camera platform 2 is set facing the tensile testing machine 3 to collect three-dimensional digital images of the test sample during the deformation test; Figure 3As shown, the seven-axis binocular camera gimbal 2 includes two cameras and a seven-axis electronically controlled adjustment mechanism electrically connected to the control box. The seven-axis electronically controlled adjustment mechanism is used for camera leveling, field of view adjustment and angle adjustment of the two cameras, including a Y-axis module 201, a pitch axis module 202 installed on the Y-axis module, a roll axis module 203 installed on the pitch axis module 202, and two sets of camera adjustment structures; each set of camera adjustment structures includes an X-axis module (camera 1 X-axis module 204 and camera 2 X-axis module 205) installed on the roll axis module and a rotation axis module (camera 1 rotation axis module 206 and camera 2 rotation axis module 207) installed on the X-axis module; two cameras (camera 1 208 and camera 2 209) are respectively installed on the corresponding rotation axis modules; each camera is provided with an IMU unit (camera 1 IMU unit 210 and camera 2 IMU unit 211), and the IMU unit, controller, and two cameras are respectively connected to the host computer for communication. Specifically, the IMU unit is connected to the host computer via a Bluetooth module, the controller is connected to the host computer via a network cable, and the two cameras are connected to the host computer via a USB camera cable.

[0066] The pitch axis module 202 is slidably connected to the Y axis module 201 along the Y axis, and the pitch axis module 202 is used to drive the roll axis module 203 to perform pitch action, and the roll axis module 203 is used to drive the two camera adjustment structures to perform roll action; the rotation axis module is slidably connected to the X axis module along the X axis, and the rotation axis module is used to drive the camera to rotate.

[0067] like Figure 5 As shown, the control box includes a motion controller, a power supply module and drivers of seven modules in the seven-axis electronic control adjustment mechanism, specifically including a motion controller 301, a power supply module 302, driver one 303, driver two 304, driver three 305, driver four 306, driver five 307, driver six 308, and driver seven 307.

[0068] Specifically, if Figure 6As shown in (a), the Y-axis module includes a stepper motor a-1, a coupling a-2, a ball screw a-3, a ball nut a-7, a slider a-5, a linear guide rail a-4, a slider seat a-6, a fixed base a-8 and a transmission platform a-9. The fixed base a-8 is provided with a linear guide rail a-4, and the ball screw a-3 is provided in the same direction as the linear guide rail a-4. The ball screw a-3 is connected to the output shaft of the stepper motor a-1 through a coupling a-2. The stepper motor A-1 is controlled by a driver 303 in the control box, and a stepper motor a-1 is arranged at one end of a fixed base a-8; a ball screw a-3 is sleeved with a ball nut a-7, a slider seat is fixedly arranged on the ball nut a-7, and a slider a-5 is fixedly connected to a slider seat a-6 through a transmission platform a-9 to carry the pitch axis module and guide the slider seat a-6 to move linearly along the Y-axis direction; a transmission platform a-9 is arranged on the slider seat a-6; and the pitch axis module is arranged on the transmission platform a-9.

[0069] In the Y-axis module, a stepper motor a-1 is controlled by a driver 303 to rotate, driving a ball screw a-3. Since a ball nut a-7 is fixed on a slider seat a-6, the ball nut a-7 rotates with the ball screw a-3 to produce linear movement, driving the slider seat a-6 to slide linearly along the Y-axis direction. The slide rail and the slider provide high-rigidity guidance and load-bearing support to ensure smooth and precise movement.

[0070] like Figure 6 As shown in (b), the pitch axis module includes a stepper motor b-1, a ball screw 2, a ball nut 2, a slider, an arc guide rail b-2, a pitch platform b-4 and a fixed base 2 b-3. The fixed base 2 b-3 is fixed on the transmission platform 1 a-9 of the Y-axis module, the arc guide rail b-2 is installed on the fixed base 2 b-3, the stepper motor b-1 is arranged on the fixed base 2 b-3, the ball screw 2 is connected to the output shaft of the stepper motor b-1 through the coupling 2, the stepper motor b-1 is controlled by the driver 2 304 in the control box, the output shaft of the stepper motor b-1 is connected to the pitch platform b-4, the pitch platform b-4 cooperates with the arc guide rail through the slider to realize rotation around the pitch axis, the angle scale is engraved near the fixed base 2, the angle scale is obtained by laser marking, and is used to indicate the pitch angle; the roll axis module is arranged on the pitch platform b-4.

[0071] In the pitch axis module, the stepper motor b-1 rotates under the control of the driver 304, and drives the pitch platform b-4 to rotate around the pitch axis through the output shaft to achieve pitch movement. Combined with the arc guide rail and scale indication, precise angle adjustment and repeated positioning can be achieved.

[0072] The roll axis module has a substantially identical structure to the pitch axis module, with the difference being that a roll axis replaces the pitch axis, a roll platform replaces the pitch platform, the axial direction of the roll axis is perpendicular to the axial direction of the pitch axis, and the other structures are identical to the pitch axis module; the stepper motor of the roll axis module drives the roll platform to perform roll motion around the roll axis;

[0073] like Figure 6 As shown in (c), the X-axis modules are symmetrically arranged in two groups. Each group of X-axis modules has the same structure as the Y-axis module, except that the X-axis modules are arranged along the X-axis direction, perpendicular to the Y-axis module. The two groups of X-axis modules include stepper motor 3 (c-1), coupling 3 (c-2), ball screw 3 (c-3), linear guide 2 (c-4), transmission platform 2 (c-5), support base 3 (c-6), transmission platform 3 (c-7), ball screw 4 (c-8), coupling 4 (c-9), stepper motor 4 (c-10), and other components. The connection method is similar to that of the Y-axis module.

[0074] The rotating axis module corresponds to the X-axis module and is provided with two groups, such as Figure 6 As shown in (d), the rotating axis module includes a stepper motor 5 d-1, a rotating worktable d-5, a transmission assembly d-3 and a support base d-4. The support base d-4 is arranged on the transmission platform of the X-axis module, and the stepper motor 5 d-1 is arranged on the support base d-4. The stepper motor 5 d-1 is controlled by the driver 5 307 in the control box. The output shaft of the stepper motor 5 d-1 is connected to the vertical rotating axis of the rotating worktable d-5 through the coupling 5 d-2 and the transmission assembly d-3 (such as direct connection or through gears / synchronous belts); a camera is installed on the rotating worktable d-5.

[0075] In the rotating axis module, the stepper motor five serves as the power source, and its output shaft is connected to the rotating axis of the rotary worktable through a coupling. When the motor is running, the rotation of the output shaft is transmitted to the rotating shaft through the transmission assembly, driving the rotary worktable to rotate around its own axis, thereby realizing rotation around the axis direction. If it is coordinated with other linear motion modules, it can expand movement in different directions to meet the needs of multi-dimensional workstation adjustment.

[0076] The seven-axis binocular camera gimbal 2 performs a series of complex tasks during the early stages of 3D-DIC experiments, including system leveling, adjusting the binocular camera's field of view, and sample centering. The seven-axis binocular camera gimbal is controlled by a host computer program written in QT software, which controls the stepper motors via a motion control card and driver. The camera used is the FLIR GS3-U3-32S4C-C. The seven-axis binocular camera gimbal allows for adjustment of the binocular camera's field of view from 25mm x 35mm to 65mm x 80mm.

[0077] like Figure 3As shown, the Bluetooth calibration platform 1 is set on the tensile testing machine 3, and the Bluetooth calibration platform 1 includes a control box 101, a calibration plate clamp 107 and a calibration plate electric control adjustment mechanism. The calibration plate clamp is used to clamp the calibration plate, and the calibration plate clamp 107 is set on the calibration plate electric control adjustment mechanism. The calibration plate electric control adjustment mechanism is used to drive the calibration plate clamp to drive the calibration plate to move; a control chip and a Bluetooth communication module electrically connected to the control chip are set in the control box 1, and the control chip is electrically connected to the calibration plate electric control adjustment mechanism; the Bluetooth communication module is connected to the host computer for communication.

[0078] For example, the control chip adopts ESP32 chip, and a power supply module is also provided in the control box 1.

[0079] Specifically, if Figure 2 As shown, the calibration plate electric control adjustment mechanism includes a first steering gear 102, a first L-shaped arm 103, a second steering gear 104, a second L-shaped arm 105, and a third steering gear 106; the first L-shaped arm 103 and the second L-shaped arm 105 respectively include an arm 1 and an arm 2 that are vertically connected;

[0080] The first servo 102 is fixedly arranged in the control box 101, and is driven and connected to arm 1 of the first L-shaped arm 103. The second servo 104 is fixedly arranged on the outside of arm 2 of the first L-shaped arm 103; arm 1 of the second L-shaped arm 105 is arranged on the inside of arm 2 of the first L-shaped arm 103, and is driven and connected to the second servo 104; the third servo 106 is fixedly arranged on the outside of arm 2 of the second L-shaped arm 105, and the calibration plate fixture 107 is arranged on the inside of arm 2 of the second L-shaped arm 105, and is driven and connected to the third servo 106.

[0081] The calibration plate fixture 107 includes a square box, left and right positioning parts and upper and lower positioning parts. The steering wheel of the third servo 106 is fixedly connected to the back of the square box. The left and right positioning parts and the upper and lower positioning parts are both installed on the square box. The left and right positioning parts include two movable clamping parts, one on the left and one on the right, for clamping the calibration plate from the left and right directions. The upper and lower positioning parts include two movable clamping parts, one on the top and one on the bottom, for clamping the calibration plate from the top and bottom directions.

[0082] Example 2

[0083] The present invention further provides a control method for a 3D-DIC measurement system with automatic leveling and calibration functions, which is applied to the above-mentioned 3D-DIC measurement system with automatic leveling and calibration functions, comprising:

[0084] like Figure 7As shown in the figure, automatic leveling: the host computer obtains the quaternion values ​​collected by the IMU units set on the two cameras, converts them into Euler angles through least squares fusion, and then performs Kalman filtering on the Euler angles to obtain stable Roll and Pitch angles. The pitch axis module and roll axis module of the seven-axis binocular camera gimbal are controlled according to the Roll and Pitch angles, thereby achieving the leveling work in the early stage of the 3D-DIC experiment; among them, if the Roll and Pitch angles are less than 0.05 degrees, the leveling is completed. If not, the two yaw axes of the seven-axis binocular camera gimbal are controlled according to the Roll and Pitch angles.

[0085] like Figure 8 As shown in the figure, automatic calibration: the host computer establishes a Bluetooth communication connection with the Bluetooth calibration platform, and controls the Bluetooth calibration platform through the host computer software programmed by QT. The calibration plate's electronic control adjustment mechanism is activated to drive the calibration plate's rotation. At the same time, the two cameras of the seven-axis binocular camera gimbal take pictures, thus realizing the function of automatic calibration.

[0086] After automatic calibration, the calibration images taken by the two cameras are processed by the calibration algorithm to obtain the corresponding calibration data.

[0087] like Figures 9-12 As shown, the calibration algorithm specifically includes:

[0088] Receive calibration plate parameters: receive preset calibration plate physical parameters;

[0089] Import binocular camera images: The two cameras are triggered synchronously to simultaneously capture left and right camera image pairs of the calibration plate in multiple poses, and perform image preprocessing on the images;

[0090] Left and right camera image pair processing: Perform spot detection on the left and right images, identify the feature points of the calibration plate, then sort the feature points by grayscale value, select the three feature points with the largest grayscale value, establish a new coordinate system based on the coordinate relationship of these three hollow points, uniformly convert the coordinates of the feature points of the left and right images to the new coordinate system, topologically sort the feature points according to the physical structure of the calibration plate, and establish a point pair mapping relationship;

[0091] Calibration data collection: store the 3D coordinates of paired feature points and corresponding pixel coordinates in all poses;

[0092] Parallel single-object positioning: Based on feature point data, the intrinsic parameter matrix of each camera is calculated in parallel and the monocular optimization result is output;

[0093] Binocular positioning: Using the corresponding feature point data of the left and right cameras, the binocular external parameters are solved and the stereo correction parameters are calculated to ensure that the subsequent matching pixels are on the same horizontal line;

[0094] Result output: Output complete calibration parameters, including the left and right camera intrinsic parameter matrices, distortion coefficients, binocular relative pose parameters, and stereo correction mapping matrix; evaluate the calibration accuracy through reprojection error, and trigger recalibration if it exceeds the threshold.

[0095] Figure 10 The host computer control interface for the seven-axis binocular gimbal and binocular camera, written for QT software, includes control buttons and communication buttons for the seven motion modules of the seven-axis binocular camera gimbal and the binocular camera. The automatic calibration function area is located in the lower left corner of the interface, which includes control buttons and communication buttons for the Bluetooth calibration platform. All functions on the interface have been implemented.

[0096] Figure 11 This is the calibration interface for using a binocular camera, which includes the calibration plate selection function, the calibration image display function, and the calibration accuracy output area.

[0097] Figure 12 This is the change between the old and new coordinate systems in the calibration algorithm. By converting the original pixel coordinate system to a new coordinate system based on the three hollow dots, not only is the coordinate system standardized, but the stability and consistency of the dot ordering are also ensured. Regardless of how the calibration plate is rotated or moved within the image, the relative positions of the dots in the new coordinate system remain unchanged, providing a reliable foundation for subsequent calibration calculations and grid fitting. This demonstrates the stability and robustness of this calibration algorithm.

[0098] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A 3D-DIC measurement system with automatic leveling and calibration functions, characterized in that: include: The host computer and the tensile testing machine, control box, seven-axis binocular camera gimbal and Bluetooth calibration platform electrically connected to the host computer; The tensile testing machine is used to perform deformation testing on the test sample; The seven-axis binocular camera gimbal is arranged opposite the tensile testing machine and is used to collect three-dimensional digital images of the test sample during the deformation test; the seven-axis binocular camera gimbal includes two cameras and a seven-axis electric control adjustment mechanism electrically connected to the control box, and the seven-axis electric control adjustment mechanism is used for camera leveling, field of view adjustment and angle adjustment of the two cameras, including a Y-axis module, a pitch axis module installed on the Y-axis module, a roll axis module installed on the pitch axis module and two groups of camera adjustment structures; each group of camera adjustment structures includes an X-axis module installed on the roll axis module and a rotation axis module installed on the X-axis module; the two cameras are respectively installed on the corresponding rotation axis modules; each camera is provided with an IMU unit, and the IMU unit and the two cameras are respectively communicated with the host computer; The Bluetooth calibration platform is arranged on the tensile testing machine, and the Bluetooth calibration platform includes a control box, a calibration plate clamp and an electric control adjustment mechanism for the calibration plate. The calibration plate clamp is used to clamp the calibration plate, and the calibration plate clamp is arranged on the electric control adjustment mechanism for the calibration plate. The electric control adjustment mechanism for the calibration plate is used to drive the calibration plate clamp to drive the calibration plate to move; a control chip and a Bluetooth communication module electrically connected to the control chip are arranged in the control box, and the control chip is electrically connected to the electric control adjustment mechanism for the calibration plate; the Bluetooth communication module is communicatively connected to the host computer.

2. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 1, characterized in that: The 3D-DIC measurement system further includes a movable lifting platform, and the seven-axis binocular camera platform is arranged on the lifting platform. The lifting platform can drive the seven-axis binocular camera platform to move up and down as a whole.

3. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 1, characterized in that: The pitch axis module is slidably connected to the Y axis module along the Y axis, the pitch axis module is used to drive the roll axis module to perform pitch action, and the roll axis module is used to drive the two sets of camera adjustment structures to perform roll action; the rotation axis module is slidably connected to the X axis module along the X axis, and the rotation axis module is used to drive the camera to rotate.

4. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 3, characterized in that: The control box includes a motion controller, a power module and drivers for seven modules in the seven-axis electronic control adjustment mechanism; the Y-axis module includes a stepper motor, a coupling, a ball screw, a linear slide rail, a slider seat, a fixed base and a transmission platform; a linear slide rail is provided on the fixed base, a ball screw is provided in the same direction along the linear slide rail, the ball screw is connected to the output shaft of the stepper motor through a coupling, the stepper motor is controlled by a driver in the control box, and the stepper motor is provided at one end of the fixed base; a ball nut is sleeved on the ball screw, the slider seat is fixedly provided on the ball nut, and the slider seat is in slidable contact with the linear slide rail; a transmission platform is provided on the slider seat; the pitch axis module is provided on the transmission platform; The pitch axis module includes a second stepper motor, an eccentric structure or a connecting rod mechanism, an arc-shaped guide rail, an angle scale plate, a pitch axis, a pitch platform and a second fixed base. The second fixed base is fixed to the first transmission platform of the Y-axis module, the arc-shaped guide rail is installed on the second fixed base, the second stepper motor is arranged on the second fixed base, the second stepper motor is controlled by the second driver in the control box, the output shaft of the second stepper motor is connected to the pitch platform through the eccentric structure or the connecting rod mechanism, the pitch platform cooperates with the arc-shaped guide rail through a slider or a bearing to realize rotation around the pitch axis, the angle scale plate is installed near the second fixed base or the arc-shaped guide rail to indicate the pitch angle; the roll axis module is arranged on the pitch platform; The roll axis module differs from the pitch axis module in that a roll axis replaces the pitch axis, a roll platform replaces the pitch platform, the axial direction of the roll axis is perpendicular to the axial direction of the pitch axis, and the other structures are the same as those of the pitch axis module; the stepper motor of the roll axis module drives the roll platform to roll around the roll axis; The X-axis modules are symmetrically arranged in two groups. The structure of each group of X-axis modules is the same as that of the Y-axis modules, except that the arrangement direction of the X-axis modules is along the X-axis direction and perpendicular to the arrangement direction of the Y-axis modules. The rotating axis module corresponds to the X-axis module and is provided with two groups. The rotating axis module includes a stepper motor five, a rotating worktable, a transmission assembly and a support base. The support base is arranged on the transmission platform of the X-axis module. The stepper motor five is arranged on the support base. The stepper motor five is controlled by the driver five in the control box. The output shaft of the stepper motor five is connected to the vertical rotating axis of the rotating worktable through the coupling five and the transmission assembly; the camera is installed on the rotating worktable.

5. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 1, characterized in that: The IMU unit is connected to the host computer via a Bluetooth module, the controller is connected to the host computer via a network cable, and the two cameras are connected to the host computer via a USB camera cable.

6. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 1, characterized in that: The electronically controlled adjustment mechanism of the calibration plate includes a first steering gear, a first L-shaped arm, a second steering gear, a second L-shaped arm, and a third steering gear; the first L-shaped arm and the second L-shaped arm respectively include an arm 1 and an arm 2 that are vertically connected; The first servo is fixedly arranged in the control box, and is driven and connected to arm 1 of the first L-shaped arm. The second servo is fixedly arranged on the outside of arm 2 of the first L-shaped arm; arm 1 of the second L-shaped arm is arranged on the inside of arm 2 of the first L-shaped arm, and is driven and connected to the second servo; the third servo is fixedly arranged on the outside of arm 2 of the second L-shaped arm, and the calibration plate fixture is arranged on the inside of arm 2 of the second L-shaped arm, and is driven and connected to the third servo.

7. The 3D-DIC measurement system with automatic leveling and calibration functions according to claim 6, characterized in that: The calibration plate fixture includes a square box, left and right positioning parts and upper and lower positioning parts. The steering wheel of the third servo is fixedly connected to the back of the square box. The left and right positioning parts and the upper and lower positioning parts are both installed on the square box. The left and right positioning parts include two movable left and right clamping parts for clamping the calibration plate from the left and right directions. The upper and lower positioning parts include two movable upper and lower clamping parts for clamping the calibration plate from the top and bottom directions.

8. A control method for a 3D-DIC measurement system with automatic leveling and calibration functions, applied to the 3D-DIC measurement system with automatic leveling and calibration functions according to any one of claims 1 to 7, characterized in that: include: Automatic leveling: The host computer obtains the quaternion values ​​collected by the IMU units installed on the two cameras, converts them into Euler angles through least squares fusion, and then performs Kalman filtering on the Euler angles to obtain stable roll and pitch angles. Based on these two angles, the pitch and roll axis modules of the seven-axis binocular camera gimbal are controlled to achieve leveling work in the early stage of the 3D-DIC experiment. Automatic calibration: The host computer establishes a Bluetooth communication connection with the Bluetooth calibration platform. The host computer software programmed in QT controls the Bluetooth calibration platform via Bluetooth, causing the calibration plate's electronic control adjustment mechanism to operate, driving the calibration plate's rotation. At the same time, the two cameras of the seven-axis binocular camera gimbal take pictures, thus achieving the automatic calibration function. After automatic calibration, the calibration images taken by the two cameras are processed by the calibration algorithm to obtain the corresponding calibration data.

9. The control method of the 3D-DIC measurement system with automatic leveling and calibration functions according to claim 8, characterized in that: During the automatic leveling process: If the Roll and Pitch angles are less than 0.05 degrees, the leveling is completed. If not, the two deflection axes of the seven-axis binocular camera gimbal are controlled based on the Roll and Pitch angles.

10. The control method of the 3D-DIC measurement system with automatic leveling and calibration functions according to claim 8, characterized in that: The calibration algorithm specifically includes: Receive calibration plate parameters: receive preset calibration plate physical parameters; Import binocular camera images: The two cameras are triggered synchronously to simultaneously capture left and right camera image pairs of the calibration plate in multiple poses, and perform image preprocessing on the images; Left and right camera image pair processing: Perform spot detection on the left and right images, identify the feature points of the calibration plate, then sort the feature points by grayscale value, select the three feature points with the largest grayscale value, establish a new coordinate system based on the coordinate relationship of these three hollow points, uniformly convert the coordinates of the feature points of the left and right images to the new coordinate system, topologically sort the feature points according to the physical structure of the calibration plate, and establish a point pair mapping relationship; Calibration data collection: store the 3D coordinates of paired feature points and corresponding pixel coordinates in all poses; Parallel single-object positioning: Based on feature point data, the intrinsic parameter matrix of each camera is calculated in parallel and the monocular optimization result is output; Binocular positioning: Using the corresponding feature point data of the left and right cameras, the binocular external parameters are solved and the stereo correction parameters are calculated to ensure that the subsequent matching pixels are on the same horizontal line; Result output: Output complete calibration parameters, including the left and right camera intrinsic parameter matrices, distortion coefficients, binocular relative pose parameters, and stereo correction mapping matrix; evaluate the calibration accuracy through reprojection error, and trigger recalibration if it exceeds the threshold.

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