CN-121977449-A - High-precision displacement measurement method and system for micro deformation of large structure

CN121977449ACN 121977449 ACN121977449 ACN 121977449ACN-121977449-A

Abstract

The invention belongs to the technical field of precision measurement and structural health monitoring, and discloses a high-precision displacement measurement system and method for micro deformation of a large structure, wherein the system comprises an integrated structure comprising a laser light source, two reflectors fixed at an included angle of 146 degrees, two imaging screens, two observation cameras and a raspberry-based data processing unit. The laser light lever optically amplifies the micro deformation, the camera shooting measurement is responsible for capturing the amplified laser spot movement, the data processing unit realizes real-time calculation, the three are organically fused, and the high-precision and non-contact laser measurement on the micro deformation and the micro displacement of the large structure is realized together. Compared with the existing distributed laser measuring equipment, the instrument has the advantages of high integration degree, small volume and light weight, is convenient for on-site deployment and use, and overcomes the limitations of the traditional single technology or distributed equipment.

Inventors

ZHAO ZHENYI
WEN YUCHEN
LI JIAXUAN
YU YANGYI
Zheng Shican
Yi Yaxuan
WANG JINHANG
NIE QIN

Assignees

沈阳航空航天大学

Dates

Publication Date: 20260505
Application Date: 20260122

Claims (10)

1. A high accuracy displacement measurement system for small deformation of large-scale structure, characterized by comprising: the two reflectors (1) have an included angle of 146 degrees; A laser light source (2) for emitting a collimated laser beam vertically to the centers of the two reflectors, wherein the divergence angle of the laser beam is less than or equal to 0.1mrad; The two observation cameras (3) are respectively aligned with the two imaging light screens (4) and are used for continuously capturing images of laser spots on the light screens, and the optical axis of each observation camera (3) is perpendicular to the reference edge of the measuring system; The two imaging light screens (4) are used for receiving laser spots formed by reflection of the reflecting mirror and are respectively positioned in front of the two observation cameras (3), and the distance between the imaging light screens (4) and the observation cameras (3) is adjustable, wherein the adjusting range is 50-200 mm; the data processing unit (5) is used for controlling the observation camera to acquire laser spot images; The display is in signal connection with the data unit and is used for displaying the measurement result in real time; The laser light source (2), the two reflectors (1), the two imaging screens (4), the two observation cameras (3) and the data processing unit (5) are integrated into an integrated structure.
2. The high-precision displacement measurement system for micro deformation of a large structure according to claim 1, wherein the reflecting mirror (1) is a quartz reflecting mirror and is respectively fixed on an XYR three-axis fine adjustment platform, and the XYR three-axis fine adjustment platform is used for adjusting the displacement adjustment and the rotation angle of the quartz reflecting mirror at X, Y axes and simulating the displacement and the rotation angle deformation of a deformation edge, wherein the displacement adjustment range is +/-10 mm, and the rotation angle adjustment angle is +/-5 degrees.
3. The high-precision displacement measurement system for micro deformation of large structures according to claim 1, wherein the laser light source (2) is generated by a laser, wherein the laser is fixedly arranged in a clamping groove at the right position of a reference positioning edge of the measurement system, and the clamping groove is provided with an angle fine tuning rotating component for adjusting the laser emission angle to +/-5 degrees so as to calibrate the laser emission direction and adapt to alignment requirements of different measurement scenes; the working voltage of the laser light source is 5V, the data processing unit supplies power, the dustproof shell and the heat dissipation structure are arranged outside the laser light source, and the working temperature is controlled below 60 ℃.
4. The high-precision displacement measurement system for micro deformation of large structures according to claim 1, wherein the imaging light screen (4) adopts a diffuse reflection light screen, the diffuse reflection rate is more than or equal to 90%, and the imaging light screen is respectively arranged in front of two cameras through sliding guide rails.
5. The high-precision displacement measurement system for the micro deformation of the large structure according to claim 1 is characterized in that the observation camera (3) is an industrial camera with a USB interface, the resolution is 1920×1080 pixels, the frame rate is more than or equal to 30fps, the lens focal length is 8mm, the height adjustable range is 100-300 mm, and the observation camera (3) is connected with the data processing unit (5) to realize real-time data transmission.
6. The high-precision displacement measurement system for micro deformation of a large structure according to claim 1, wherein the data processing unit (5) adopts a raspberry group 4B main board, the parameters of the raspberry group 4B main board are a four-core Cortex-A72 processor, a 4GB memory, a 16GB MicroSD card is provided as a storage medium, a Linux operating system is carried, and a power management module is arranged in the data processing unit.
7. The high-precision displacement measurement system for micro deformation of a large structure according to claim 1, further comprising a supporting and fixing structure for bearing and positioning all functional modules, wherein the supporting and fixing structure comprises a fixing bracket, a PVC board base and stainless steel connectors, the PVC board base (6) is used as a basic supporting platform of the system, the fixing bracket is installed on the base in a modularized mode and can be used for fixing a laser light source, two reflectors, two observation cameras and a raspberry group data processing unit respectively, and each optical and electronic module is tightly integrated with the base through the fixing bracket.
8. The high-precision displacement measurement method for the micro deformation of the large structure is characterized by comprising the following steps of: Calibrating measurement parameters, wherein the parameters comprise equivalent focal lengths (f 1, f 2), principal point positions and distortion coefficients of an observation camera, a vertical distance S from a laser light source to the center of a reflecting mirror, and a vertical distance B from the laser light source to a light screen, and initial reflection angles theta 1 and theta 2 between reflected laser and a light beam emitted by the laser light source; extracting the laser spot position and determining the center coordinate of the laser spot: and calculating deformation, wherein the deformation comprises a distance change t and a rotation angle change alpha.
9. The method for high-precision displacement measurement of micro-deformations of a large structure according to claim 8, The extracting the laser spot position and determining the laser spot center coordinate comprises the following steps: Preprocessing the acquired image by a data processing unit: performing de-distortion treatment on the image by using the distortion coefficient obtained by calibration, and then graying the de-distorted image to obtain a gray image; the gray level image is processed by adopting a sub-pixel level laser spot center extraction algorithm, and a Gaussian surface fitting method is specifically adopted: as shown in equation (1), it is assumed that the pixel gray distribution of the laser spot approximately follows a two-dimensional gaussian distribution: (1) Taking the logarithm of the two sides of the formula (1), and converting the solving problem into a binary quadratic polynomial fitting problem as shown in the formula (2): (2) And solving by using a least square method, and taking an image coordinate corresponding to the fitting curve extreme point as a sub-pixel level coordinate of the laser spot center.
10. The high-precision displacement measurement method for micro deformation of a large structure according to claim 8, wherein the calculating the deformation amount comprises: According to the laser spot moving amount, the final distance variation t and the corner variation alpha are solved through a nonlinear iterative algorithm: calculating the pixel movement amount of the laser spot, namely obtaining pixel variation delta X1, delta X2, delta Y1 and delta Y2 of the laser spot on an image according to the initial coordinate and the deformed coordinate of the center of the laser spot as shown in formulas (3) - (4); (3) (4) Converting the actual moving distance of the laser light spot, namely calculating the actual moving distances delta X 'and delta Y' of the laser light spot on an imaging light screen according to the similar triangle relation of the perspective projection of the center of the camera and combining the known equivalent focal length (f 1 , f 2 ) of the camera, the pixel size P of the light screen and the physical size L of the light screen as shown in the formula (5-7); (5) (6) (7) Building and solving a nonlinear equation set: Taking DeltaX 'and DeltaY' as observables, taking the distance deformation t and the corner deformation alpha as to-be-measured, and substituting the to-be-measured values into an equation set established by the geometric relationship of the laser beam lever as shown in the formulas (8-9); (8) (9) Defining error functions F 1 and F 2 as shown in equation (10-11); (10) (11) A nonlinear iterative solving algorithm is adopted: calculating partial derivatives of the error function about t and alpha respectively as shown in formulas (12-13), and constructing a jacobian matrix J; (12) (13) b. iteratively updating values of deformation parameters t and alpha by using the inverse of the jacobian matrix and the error vector as shown in formula (14); (14) c. the initial value of the iteration is set to 0.

Description

High-precision displacement measurement method and system for micro deformation of large structure Technical Field The invention belongs to the technical field of precision measurement and structural health monitoring, and particularly relates to a high-precision displacement measurement method and system for micro deformation of a large structure. Background In many engineering and scientific fields, accurate measurement of a minute distance is of great importance. In the field of aerospace, the manufacturing and assembling precision of aircraft parts can directly influence the flight performance and safety, and accurate measurement of a small distance is a key for guaranteeing the fitting degree of the parts. In the manufacture of electronic chips, the distance between circuits in the chips is extremely small, and high-precision micro distance measurement is the basis for ensuring the normal function of the chips, so that a large-scale structure micro deformation measurement method with economy, high efficiency, strong adaptability and high measurement precision is needed, and data support is provided for safety monitoring, mechanical analysis and risk assessment of the large-scale structure. The existing measurement comprises the advantages of direct contact with an object, visual measurement results, low efficiency, high cost, limited applicable scene, possibility of damaging the measured object, laser range finders, non-contact equipment, accuracy up to millimeter level, and the like, but the laser range finders cannot meet the requirements of large-scale structure small deformation measurement and cannot detect angle deformation, the digital image correlation method has the advantages of simplicity and convenience in operation, higher accuracy, and the like, and has the advantages of needing spray painting speckle or other characteristics to change the surface morphology of the structure, and photographic measurement, although the application scene is various, the stability of external parameters, inconvenient installation and accuracy to be improved are easily affected by vibration. Therefore, aiming at the defects of the functional short plate and scene adaptation of the existing laser measuring instrument, the high-precision displacement measuring method and system suitable for the micro deformation of the large-scale structure are developed, and the technical problem to be solved in the field is urgent. Disclosure of Invention In view of the above, the present invention aims to provide a high-precision displacement measurement method and system for micro deformation of a large-scale structure, so as to overcome the defect that the rotation angle measurement method based on the laser PSD cannot measure the space deformation, and meet the requirement of the engineering site on multi-dimensional measurement data. The technical scheme provided by the invention is that in the first aspect, the invention provides a high-precision displacement measurement system for micro deformation of a large structure, which comprises: The included angle of the two reflectors is 146 degrees; the laser light source is used for emitting collimated laser beams, the collimated laser beams vertically irradiate to the centers of the two reflectors, and the divergence angle of the laser beams is less than or equal to 0.1mrad; The two observation cameras are respectively aligned with the two imaging screens and are used for continuously capturing images of laser spots on the screens, and the optical axes of the observation cameras are perpendicular to the reference edge of the measuring system; The two imaging light screens are used for receiving laser spots formed by reflection of the reflecting mirror and are respectively positioned in front of the two observation cameras, and the distance between the imaging light screens and the observation cameras is adjustable within the adjustment range of 50-200 mm; The data processing unit is used for controlling the observation camera to acquire laser spot images; The display is in signal connection with the data unit and is used for displaying the measurement result in real time; The laser light source, the two reflectors, the two imaging screens, the two observation cameras and the data processing unit are integrated into an integrated structure. The mirror is preferably a quartz mirror and is respectively fixed on an XYR triaxial fine tuning platform, the XYR triaxial fine tuning platform is used for adjusting displacement adjustment and rotation angle of the quartz mirror on X, Y axes and simulating displacement and rotation angle deformation of a deformation edge, wherein the displacement adjustment range is +/-10 mm, and the rotation angle adjustment angle is +/-5 degrees. Preferably, the laser light source is generated by a laser, wherein the laser is fixedly arranged in a clamping groove at the right opposite position of the reference positioning edge of the measuring system