A six-degree-of-freedom absolute deformation measurement method based on single reference point measurement of a measuring platform

Abstract

A kind of six-freedom absolute deformation measurement method of measuring platform based on single reference point measurement platform, with measuring platform as center, in the measured area, and with measuring platform as the other side of symmetry, reference point is arranged, laser displacement measuring instrument, camera and target are arranged on reference point;Camera is used to collect measuring platform target image on measuring platform;Target on reference point is used as feature recognition point;Two-dimensional inclination measuring instrument is arranged on measuring platform, measuring platform camera and measuring platform target;Measuring platform target is used for collecting image data by camera of reference point;The present application realizes real-time solution to six-freedom (three-dimensional translation+three-dimensional rotation) displacement of measuring platform by single reference point feature identification and measuring platform feature identification, to realize high-precision measurement to position change of measuring platform itself, so that measurement result is more accurate.

Description

Technical Field

[0001] This invention relates to the field of engineering measurement technology, and in particular to a six-degree-of-freedom absolute deformation measurement method based on a single reference point measurement platform. Background Technology

[0002] In many industrial production and scientific research scenarios, a measuring platform is a collection of devices used for measurement tasks. For example, a measuring platform composed of cameras, laser emitters, and other equipment can complete measurement work. During measurement, the measuring platform itself undergoes positional changes, which significantly affect the accuracy of the measurement results. For instance, in engineering construction, measuring platforms are needed to monitor the structural stability of the construction area. Environmental vibrations at the site can also affect the measuring platform, causing positional changes and impacting the measurement results. Furthermore, some measuring platforms used in engineering surveys, such as total stations, typically require three reference points to complete the measurement, but setting up three reference points is difficult in real-world working environments. Therefore, developing a method based on a single reference point, using photoelectric measurement technology and image recognition technology to monitor changes in the measuring platform itself has significant application value. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide a six-degree-of-freedom absolute deformation measurement method based on a single reference point measurement platform. Based on laser tilt measurement, image recognition, and distance calculation, and through the feature identification of the single reference point and the feature identification of the measurement platform, the method realizes real-time calculation of the six-degree-of-freedom (three-dimensional translation + three-dimensional rotation) displacement of the measurement platform, so as to achieve accurate measurement of the position change of the measurement platform itself. Thus, the position change data of the measurement platform can be applied to the actual measurement work of the measurement platform, making the measurement results more accurate.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A method for measuring six-degree-of-freedom absolute deformation based on a single-reference-point measuring platform includes the following steps:

[0006] Step 1, Setting up reference points:

[0007] Centered on the measuring platform, a reference point is set in the area to be measured and on the other side symmetrical to the measuring platform. A laser displacement measuring instrument, a camera, and a target are arranged on the reference point. The camera is used to collect images of the measuring platform target on the measuring platform. The target on the reference point serves as a feature recognition point for the measuring platform camera to capture and recognize the measurement in step two.

[0008] Step 2, Setting up the measuring platform:

[0009] A two-dimensional tilt measuring instrument, a camera, and a target are set up on the measuring platform; the target provides image data for the camera at the reference point to collect the image data.

[0010] Step 3: Obtain six degrees of freedom using the center of gravity algorithm. , , The displacement;

[0011] Images of the target on the testing platform are acquired by cameras positioned at the reference point, and calculations are performed. , The target centroid coordinates are calculated as follows:

[0012] (1)

[0013] in, It is the grayscale value of the image pixel at pixel coordinates (u,v); Represents column coordinate values; Represents the row coordinate value;

[0014] (2)

[0015] (3)

[0016] in, Let t be the displacement of the measuring platform in the X direction at time t relative to the initial time. The displacement of the measuring platform in the Z direction at time t relative to the initial time is given. The change of the column coordinates of the target center at time t relative to the initial time; The change of the row coordinate of the target center at time t relative to the initial time. The distance between the measuring platform and the reference point. The size of the camera pixel (micrometer level). The focal length of the camera lens;

[0017] The measuring platform was directly measured using a laser displacement measuring instrument. ;

[0018] The tilt angle of the measuring platform around the XY axis was directly measured using a two-dimensional inclinometer. , ;

[0019] The target image of the reference point in step 1 is acquired by the camera on the measuring platform. The angular change of the measuring platform around the Z-axis can be calculated by subtracting the contribution of the horizontal pixel center change of the target image at the reference point from the horizontal pixel center change of the measuring platform during translation, and then transforming the formula. :

[0020] (4)

[0021] The coordinates of the center of the light spot in the target image illuminated by the rear-view camera of the measuring platform. Coordinates of the center of the target image spot at the initial reference point Change The change in the number of pixels on the target platform illuminated by the camera at the reference point compared to the initial number of pixels. , Let Z be the coordinate of the measuring platform. The tilt angle of the measuring platform around the Y-axis, The distance between the reference point and the measuring platform. For pixel size, This refers to the focal length of the camera lens.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The invention uses a spot centroid calculation method to calculate the displacement of a long-distance measuring station. Controlled within 0.1 pixel precision; The accuracy is better than 0.1 mm, obtained directly from a laser displacement measuring instrument; two-dimensional tilt angle is measured. The data is obtained directly from a two-dimensional inclinometer, and the accuracy can be controlled within 1 second. The accuracy of the calculation using the center of gravity of the light spot is about 1 second, thus enabling high-precision measurement with six degrees of freedom.

[0024] Therefore, this invention, based on laser tilt measurement, image recognition, and center of gravity algorithm, uses single reference point feature identification and platform feature identification to achieve real-time calculation of the six degrees of freedom (three-dimensional translation + three-dimensional rotation) displacement of the platform, thereby achieving high-precision measurement of the platform's own positional changes and making the measurement results more accurate. Attached Figure Description

[0025] Figure 1 This is the overall coordinate system of the measuring platform and reference point of this invention.

[0026] Figure 2 This is a schematic diagram of the target light intensity distribution of the present invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings.

[0028] A method for measuring six-degree-of-freedom absolute deformation based on a single-reference-point measuring platform includes the following steps:

[0029] Step 1, Setting up reference points:

[0030] Centered on the measuring platform, reference points are set up in the area to be measured and on the opposite side symmetrical to the measuring platform. A laser displacement measuring instrument, a camera, and a target are arranged at the reference points. The laser displacement measuring instrument is used to measure and calculate the displacement change of the measuring platform in step 3. (Main contribution); The camera is used to acquire images of the target on the measuring platform, which is used in step 3 to calculate the displacement changes of the measuring platform in the X and Z directions. (Main contribution); The target serves as a feature recognition point. The target is placed at the reference point for the camera on the measuring platform in step two to capture, identify and measure.

[0031] Step 2, Setting up the measuring platform:

[0032] A two-dimensional inclinometer, a camera (either a separate rear-view camera aligned with a reference point or a single main measuring camera) and a target are set up on the measuring platform. The two-dimensional inclinometer is used to measure the angular changes of the measuring platform itself in the X and Y directions in step 3. , The camera on the measuring platform is used to acquire the target image of the reference point in step 1. The angular change of the measuring platform around the Z-axis can be calculated by subtracting the contribution of the horizontal pixel center change of the target image at the reference point from the horizontal pixel center change caused by the translation of the measuring platform. The test platform target provides a reference point for camera image data acquisition; the overall coordinate system is as follows: Figure 1 As shown.

[0033] Step 3: Data calculation and processing to obtain six-degree-of-freedom three-dimensional translation. + 3D rotation , , The displacement of )

[0034] Images of the target on the testing platform are acquired by cameras positioned at the reference point, and calculations are performed. , ;like Figure 2 As shown, the target centroid coordinates are calculated as follows:

[0035] (1)

[0036] in, It is the grayscale value of the image pixel at pixel coordinates (u,v); Represents column coordinate values; Represents the row coordinate value;

[0037] (2)

[0038] (3)

[0039] Let t be the displacement of the measuring platform in the X direction at time t relative to the initial time. The displacement of the measuring platform in the Z direction at time t relative to the initial time is given. The change of the column coordinates of the target center at time t relative to the initial time; The change of the center coordinate of the target on the measuring platform at time t relative to the initial time. The distance between the measuring platform and the reference point. The size of the camera pixel (micrometer level). The focal length of the camera lens;

[0040] The measuring platform was directly measured using a laser displacement measuring instrument. ;

[0041] The tilt angle of the measuring platform around the XY axis was directly measured using a two-dimensional inclinometer. , ;

[0042] The target image of the reference point in step 1 is acquired by the camera on the measuring platform. The angular change of the measuring platform around the Z-axis can be calculated by subtracting the contribution of the horizontal pixel center change of the target image at the reference point from the horizontal pixel center change of the measuring platform during translation, and then transforming the formula. :

[0043] (4)

[0044] The coordinates of the center of the light spot in the target image illuminated by the rear-view camera of the measuring platform. Coordinates of the center of the target image spot at the initial reference point Change The change in the number of pixels on the target platform illuminated by the camera at the reference point compared to the initial number of pixels. , Let Z be the coordinate of the measuring platform. The tilt angle of the measuring platform around the Y-axis, The distance between the reference point and the measuring platform. For pixel size, This refers to the focal length of the camera lens.

[0045] Once the displacement data of the measuring platform is calculated, it can be sent to the next higher-level application, namely the measurement system to which the measuring platform belongs, via the serial port. The measurement system will then add the displacement of the measuring platform to the measurement system to compensate for the deformation error of the measuring platform, thereby improving the measurement accuracy of the measurement system.

Claims

1. A method for measuring six-degree-of-freedom absolute deformation based on a single-reference-point measuring platform, characterized in that, Includes the following steps: Step 1, Setting up reference points: With the measuring platform as the center, a reference point is set in the area to be measured and on the other side symmetrical to the measuring platform. A laser displacement measuring instrument, a camera and a target are arranged on the reference point. The camera is used to collect images of the measuring platform target on the measuring platform. The target on the reference point is used as a feature recognition point for the measuring platform camera to capture and recognize the measurement in step 2. Step 2, Setting up the measuring platform: A two-dimensional tilt measuring instrument, a camera, and a target are set up on the measuring platform; the target provides image data for the camera at the reference point to collect the image data. Step 3: Obtain six degrees of freedom using the center of gravity algorithm. , , The displacement; Images of the target on the testing platform are acquired by cameras positioned at the reference point, and calculations are performed. , The target centroid coordinates are calculated as follows: （1） in, It is the grayscale value of the image pixel at pixel coordinates (u,v); Represents column coordinate values; Represents the row coordinate value; （2） （3） Let t be the displacement of the measuring platform in the X direction at time t relative to the initial time. The displacement of the measuring platform in the Z direction at time t relative to the initial time is given. The change of the column coordinates of the target center at time t relative to the initial time; The change of the row coordinate of the target center at time t relative to the initial time; This is the distance between the measuring platform and the reference point; The size refers to the camera pixel size, which is in the micrometer range. The focal length of the camera lens; The measuring platform was directly measured using a laser displacement measuring instrument. ; The tilt angle of the measuring platform around the XY axis was directly measured using a two-dimensional inclinometer. , ; The target image of the reference point in step 1 is acquired by the camera on the measuring platform. The angular change of the measuring platform around the Z-axis can be calculated by subtracting the contribution of the horizontal pixel center change of the target image at the reference point from the horizontal pixel center change of the measuring platform during translation, and then transforming the formula. : （4） The coordinates of the center of the light spot in the target image illuminated by the rear-view camera of the measuring platform. Coordinates of the center of the target image spot at the initial reference point Change The change in the number of pixels on the target platform illuminated by the camera at the reference point compared to the initial number of pixels. , Let Z be the coordinate of the measuring platform. The tilt angle of the measuring platform around the Y-axis, The distance between the reference point and the measuring platform. For pixel size, This refers to the focal length of the camera lens.

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