Non-contact finishing grinding block motion plane velocity field measurement method and system

Abstract

The present application discloses a non-contact method and system for measuring the plane velocity field of the grinding block motion in a finishing process, the method comprising: using a high-speed camera to record the time-series images of the grinding block in the area to be measured; performing image pre-processing on the original grinding block time-series images; performing cross-correlation processing or grinding block particle tracking processing on the pre-processed grinding block time-series images to obtain the plane velocity field distribution of the grinding block motion in the area to be measured; post-processing the plane velocity field to eliminate erroneous velocity vectors, and at the same time replace the eliminated erroneous vectors by interpolation based on adjacent correct vectors; and calibrating the plane velocity field to convert the velocity field in pixel units into a velocity field in internationally common length units. The present application obtains the entire plane velocity field distribution of the grinding block motion in the finishing process to be measured through the grinding block time-series images taken by a single high-speed camera. Compared with the single-point velocity measurement method in the prior art, a whole-field measurement method for the plane instantaneous velocity field is provided, which greatly improves the velocity field measurement efficiency.

Description

Technical Field

[0001] The present invention relates to the field of advanced manufacturing, and in particular to a method and system for measuring a velocity field of a grinding block motion plane in a non-contact finishing process based on a time-series image. Background Art

[0002] Rolling finishing technology is used to improve the surface quality and performance of parts. This technology is to place the workpiece in a free or non-free state in a container containing free granular media (rolling polishing blocks) and liquid media (abrasives, water). By setting a certain form of relative movement between the workpiece and the processing medium, the processing medium produces disordered or ordered collision rolling, micro-grinding and certain chemical effects on the workpiece surface, thereby achieving the effect of polishing, brightening, deburring, cleaning and descaling the surface of the part to improve the overall surface quality. Rolling finishing technology has strong adaptability and a wide range of applications. In recent years, its application in the fields of machinery, electronics, information, energy, aerospace, weapons, etc. has developed rapidly. As the processing medium in the rolling finishing technology, the impact speed of the grinding block relative to the workpiece greatly affects the material removal, the reduction of the workpiece roughness and the improvement of the hardness of the workpiece surface. However, the rolling polishing block is a collection of elastic particles, which is affected by multiple forces such as contact force, damping and gravity, and has the forced dynamic characteristics of the particle group. Therefore, the research method of the grinding block speed should be different from the traditional solid, liquid and gas research methods. At present, only the speed measurement method based on CCD laser displacement sensor and optical probe measurement can realize the single-point measurement of the grinding block speed. It has always been a challenge to directly obtain the instantaneous velocity field of the grinding block plane. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for measuring the plane velocity field of a grinding block in a non-contact finishing process based on time-series images, so as to solve the problems raised in the above technical background.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The first aspect of the present application provides a method for measuring the plane velocity field of a non-contact finishing grinding block motion based on a time-series image, comprising the following steps:

[0006] A1, using a high-speed camera to record the time-series images of the grinding block in the area to be tested;

[0007] A2, image pre-processing of the original grinding block time series images, including brightness adjustment and contrast adjustment;

[0008] A3, performing displacement estimation processing on the pre-processed grinding block time series image, including cross-correlation calculation or grinding block particle tracking, to obtain the distribution of the grinding block motion plane velocity field in the test area;

[0009] A4, post-processing the plane velocity field, removing the erroneous velocity vectors, and replacing the removed erroneous vectors with interpolation based on adjacent correct vectors;

[0010] A5, scale calibration is performed on the plane velocity field, and the velocity field in pixels is converted into a velocity field in internationally accepted length units.

[0011] Preferably, step A1 includes the following steps: using a soft white light source to illuminate the moving grinding block, installing a high-speed camera at a position where the line of sight is perpendicular to the plane of the velocity field to be measured and at an appropriate distance, adjusting parameters such as the camera exposure time and the shooting frame rate, and shooting the grinding block to obtain a time-series image of the grinding block in the area to be measured.

[0012] Preferably, step A2 includes the following steps: adjusting the brightness and contrast of the original time-series images of the grinding block to obtain a higher recognition of the grinding block texture and improve the displacement estimation accuracy.

[0013] Preferably, step A3 includes the following steps: performing displacement estimation processing on the processed grinding block images at adjacent moments, including cross-correlation calculation or grinding block particle tracking, to obtain the plane velocity field distribution of the grinding block motion in the test area; wherein, when the grinding block diameter is small, a cross-correlation algorithm is used for processing, and when the grinding block diameter is large, a grinding block particle tracking algorithm is used for processing.

[0014] Preferably, step A4 comprises the following steps: using the global threshold calculation formula (1), the local mean value filtering formula (2) or the local median filtering formula (3) to process the plane flow field U(i, j), selecting and eliminating the error vector therein, and using the linear interpolation or cubic spline interpolation method to interpolate the correct velocity vector to obtain a replacement vector,

[0015]

[0016]

[0017]

[0018] Among them, U(i, j) is the value of the velocity field; STD(U(i, j)) is the standard deviation of the velocity field; T is the filtering threshold; STD(U(i-1:i+1, j-1:j+1)) is the standard deviation of the velocity field in the local (3×3) area; is the average value of the velocity field in the local (3×3) area; It is the median of the velocity field in the local (3×3) area.

[0019] Preferably, step A5 includes the following steps: keeping the position of the camera and the measuring area unchanged, capturing an image of an object of known length, such as capturing a ruler, etc., and then calculating the object size corresponding to a single image pixel, i.e., x meters per pixel, and then multiplying the velocity field in pixels by x meters per pixel to convert it into a velocity field matrix in internationally accepted length units such as meters.

[0020] The second aspect of the present application provides a non-contact finishing grinding block motion plane velocity field measurement system based on time-series images, including a hardware system and a software system, wherein:

[0021] The hardware system includes: a high-speed camera and a main lens for collecting images, an illumination device and a data processing system, wherein the data processing system is used to control the shooting parameters of the high-speed camera and receive the time-series images of the grinding block transmitted by the high-speed camera;

[0022] The software system includes: a time-series grinding block image velocity field calculation platform for performing data processing and analysis on images.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] The present application can obtain the entire plane instantaneous velocity field distribution of the movement of the grinding block to be measured for finishing processing through the time-series images of the grinding block taken by a single high-speed camera. Compared with the existing single-point velocity measurement methods such as laser displacement sensors and optical fiber probes, the present application provides a whole-field measurement method for the plane instantaneous velocity field, which also greatly improves the efficiency of velocity field measurement and promotes the research on roller finishing processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0026] Figure 1 It is a flow chart of the method for measuring the velocity field of the motion plane of the grinding block in non-contact finishing processing based on time-series images;

[0027] Figure 2 It is a schematic diagram of the structure of a non-contact finishing grinding block motion plane velocity field measurement system based on time-series images;

[0028] Figure 3 This is a diagram of the grinding block motion measurement device for spindle type barrel grinding and finishing;

[0029] Figure 4 This is an example of a brown corundum spherical grinding block;

[0030] Figure 5 is an example of a scale calibration image;

[0031] Figure 6 This is an example diagram of the measurement results of the transient velocity field distribution. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Example:

[0034] Figure 1 The flowchart of the method for measuring the plane velocity field of the grinding block motion in non-contact finishing processing based on time-series images.

[0035] like Figure 1 As shown, a non-contact finishing grinding block motion plane velocity field measurement method based on time-series images in this embodiment obtains the grinding block velocity field distribution by high-speed camera measurement, and the specific steps are as follows:

[0036] Step 1: Use a high-speed camera to measure the motion of the grinding block in the vertical spindle barrel finishing machine.

[0037] like Figure 3 As shown, the diameter of the roller is 216 mm, the height is 210 mm, the material is stainless steel (0Cr18Ni9), and the filling amount is 60% of the roller volume.

[0038] like Figure 4 As shown, the grinding block is a brown corundum spherical grinding block with a diameter of 3 mm and a density of 2.49 g / cm 3 .

[0039] Step 2: A MEMRECAM Q1m high-speed camera was used to capture images at 500 frames per second (fps), and an XSJ2X1300-2 incandescent lamp was used to illuminate the capture area.

[0040] The drum speeds are set to 60 rpm, 80 rpm, and 100 rpm respectively; the image field of view is 66 mm × 63 mm, providing a resolution of 1280 × 1024 pixels.

[0041] Step 3: Adjust the brightness and contrast of the recorded image to improve the brightness and contrast of the image.

[0042] Step 4: Perform cross-correlation calculation on the processed grinding block images at adjacent moments according to formula (1) to obtain the plane velocity field distribution of the grinding block motion in the test area.

[0043]

[0044] Step 5: Use the global threshold calculation formula (2), local average filter formula (3) or local median filter formula (4) to process the obtained plane flow field U(i, j). Select and eliminate the error vectors, and use linear interpolation or cubic spline interpolation to interpolate the correct velocity vector to obtain a replacement vector.

[0045]

[0046]

[0047]

[0048] Among them, U(i, j) is the value of the velocity field; STD(U(i, j)) is the standard deviation of the velocity field; T is the filtering threshold; STD(U(i-1:i+1, j-1:j+1)) is the standard deviation of the velocity field in the local (3×3) area; is the average value of the velocity field in the local (3×3) area; It is the median of the velocity field in the local (3×3) area.

[0049] Step 6: Keep the camera and the measurement area unchanged, and shoot the ruler to calibrate the scale. Figure 5 Then calculate the object size corresponding to a single image pixel, and multiply the velocity field in pixels by x meters per pixel to convert it into a velocity field vector matrix in meters, such as Figure 6 .

[0050] On the other hand, the present application also discloses a non-contact finishing grinding block motion plane velocity field measurement system based on time-series images.

[0051] See also Figure 2 As shown in the figure, the system includes two parts: hardware system and software system. Among them:

[0052] The hardware system includes: a high-speed camera and a main lens for collecting images, an illumination device and a data processing system, wherein the data processing system is used to control the shooting parameters of the high-speed camera and receive the time-series images of the grinding block transmitted by the high-speed camera;

[0053] The software system includes: a time-series grinding block image velocity field calculation platform for performing data processing and analysis on the image.

[0054] In summary, the present application can obtain the entire plane instantaneous velocity field distribution of the movement of the grinding block to be measured during finishing processing through the time-series images of the grinding block taken by a single high-speed camera. Compared with the existing single-point velocity measurement methods such as laser displacement sensors and optical fiber probes, the present application provides a whole-field measurement method for the plane instantaneous velocity field, which also greatly improves the efficiency of velocity field measurement and promotes the research on roller finishing processing.

[0055] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A non-contact finishing grinding block motion plane velocity field measurement method, characterized in that: The following steps are involved: A1, using a high-speed camera to record the time-series images of the grinding block in the area to be tested; A2, image pre-processing of the original grinding block time series images, including brightness adjustment and contrast adjustment; A3, performing displacement estimation processing on the pre-processed grinding block time series image, including cross-correlation calculation or grinding block particle tracking, to obtain the distribution of the grinding block motion plane velocity field in the test area; A4, post-processing the plane velocity field, removing the erroneous velocity vectors, and replacing the removed erroneous vectors with interpolation based on adjacent correct vectors; A5, scale calibration of the plane velocity field, converting the velocity field in pixels into the velocity field in international common length units; Step A3 includes the following steps: The processed grinding block images at adjacent moments are subjected to displacement estimation processing, including cross-correlation calculation or grinding block particle tracking, to obtain the distribution of the grinding block motion plane velocity field in the test area; wherein, when the grinding block diameter is small, the cross-correlation algorithm is used for processing, and when the grinding block diameter is large, the grinding block particle tracking algorithm is used for processing; Step A4 includes the following steps: The planar flow field U(i,j) obtained by global threshold calculation formula (1), local average filter formula (2) or local median filter formula (3) is selected and eliminated, and the erroneous vector is obtained by linear interpolation or cubic spline interpolation according to the correct velocity vector interpolation. Among them, U(i, j) is the value of the velocity field; STD(U(i, j)) is the standard deviation of the velocity field; T is the filtering threshold; STD(U(i-1:i+1, j-1:j+1)) is the standard deviation of the velocity field in the local (3×3) area; is the average value of the velocity field in the local (3×3) area; It is the median of the velocity field in the local (3×3) area.

2. The non-contact finishing grinding block motion plane velocity field measurement method according to claim 1 is characterized in that: Step A1 includes the following steps: A soft white light source was used to illuminate the moving grinding block. A high-speed camera was installed at a position with a line of sight perpendicular to the plane of the velocity field to be measured and at an appropriate distance. The camera exposure time and shooting frame rate were adjusted, and the grinding block was photographed to obtain a time-series image of the grinding block in the measured area.

3. The method for measuring the plane velocity field of a non-contact finishing grinding block according to claim 1 is characterized in that: Step A2 includes the following steps: The brightness and contrast of the original time-series images of the grinding block are adjusted to obtain a higher recognition of the grinding block texture and improve the displacement estimation accuracy.

4. The method for measuring the plane velocity field of a non-contact finishing grinding block according to claim 1 is characterized in that: Step A5 includes the following steps: Keeping the position of the camera and the measurement area unchanged, take an image of an object of known length, and then calculate the object size corresponding to a single image pixel, that is, x meters per pixel. Then multiply the velocity field in pixels by x meters per pixel to convert it into a velocity field matrix in internationally accepted length units.

5. A measurement system based on the non-contact finishing grinding block motion plane velocity field measurement method according to claim 1, characterized in that: It includes two parts: hardware system and software system. The hardware system includes: a high-speed camera and a main lens for collecting images, an illumination device and a data processing system, wherein the data processing system is used to control the shooting parameters of the high-speed camera and receive the time-series images of the grinding block transmitted by the high-speed camera; The software system includes: a time-series grinding block image velocity field calculation platform for performing data processing and analysis on the image.

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