Bolt loosening detection system and detection method for planetary mixer

Abstract

The present invention relates to a bolt loosening detection system and method for a planetary mixer. A bolt loosening detection system for a planetary mixer comprises a mixer, wherein a bolt assembly is installed in the interior of the mixer, and two symmetrically arranged camera assemblies are installed in the exterior of the mixer, and photos of the bolt assembly are taken by the two camera assemblies to determine whether the bolt assembly is loose. By setting the camera assembly, it is possible to prevent and detect the loosening of the bolts in advance, and avoid falling onto the materials and causing the materials to be scrapped. The use efficiency is high, the accuracy is high, the abnormal loosening of the bolts in the mixer can be detected early, and non-destructive detection and non-contact detection can be realized. The detection process will not destroy the vacuum environment inside the mixer when it is working.

Description

Technical Field

[0001] The invention relates to the technical field of planetary mixer fault monitoring, in particular to a planetary mixer bolt loosening detection system and detection method. Background Art

[0002] Planetary mixers, as mixing and stirring equipment, are suitable for various high-viscosity and high-solid materials and are widely used in the fields of energy, electronics, chemistry, food, and pharmaceuticals. When a planetary mixer is operating, its cavity usually needs to maintain a vacuum state, making it difficult to detect loose bolts inside the cavity. If the loose bolts fall into the material, it will cause material contamination and even cause the entire batch of materials to be scrapped, resulting in waste. In the existing technology, the detection of loose bolts inside planetary mixers often relies on manual inspections. This detection method is inefficient, has low detection accuracy, and cannot guarantee the timeliness of detection. Summary of the Invention

[0003] Based on this, it is necessary to provide a planetary mixer internal bolt loosening detection system and detection method to address the problems of low efficiency, low detection accuracy and difficulty in ensuring timeliness in the existing technology for planetary mixer internal bolt loosening detection.

[0004] The technical solutions adopted in the present invention are as follows:

[0005] A bolt loosening detection system for a planetary mixer comprises a mixer, wherein a bolt assembly is mounted inside the mixer, and two symmetrically arranged camera assemblies are mounted outside the mixer. The two camera assemblies take photos of the bolt assembly to determine whether the bolt assembly is loose.

[0006] As a further improvement of the above technical solution:

[0007] The mixer includes a vacuum cover, a transmission box is mounted on the top of the vacuum cover, a container is mounted on the bottom of the vacuum cover, the interior space of the container is connected to the interior space of the vacuum cover to form a working space, and a planetary gearbox and a stirring assembly connected to the output end of the planetary gearbox are arranged in the working space;

[0008] The input end of the transmission box is connected to the first motor, and the output end of the transmission box is connected to the housing of the planetary gear box. The first motor drives the planetary gear box to rotate through the transmission box, thereby driving the stirring assembly to revolve through the planetary gear box.

[0009] The input end of the planetary gearbox is connected to the second motor, and the second motor drives the stirring assembly to rotate through the planetary gearbox.

[0010] Two symmetrically arranged pipe openings are provided on the side wall surface of the vacuum cover, a single pipe opening extends obliquely downward, and a sight glass is mounted on the end of the single pipe opening.

[0011] A single camera assembly includes a mounting base fixed on the corresponding pipe mouth, and a first mounting bracket and a second mounting bracket are fixed on the mounting base respectively. A visual camera is installed on the first mounting bracket, and the lens of the visual camera is facing the corresponding viewing mirror. The visual camera takes pictures of the inside of the workspace through the corresponding viewing mirror; a rotary cylinder is installed on the second mounting bracket, and the output end of the rotary cylinder passes through the corresponding viewing mirror and is connected to a scraper arranged on the inner side of the corresponding viewing mirror. The scraper is close to the inner end face of the corresponding viewing mirror, and the rotary cylinder drives the scraper to rotate, thereby scraping off the material attached to the inner end face of the viewing mirror.

[0012] The bolt assembly includes several sets of bolt groups, and a single bolt group includes several bolts distributed along the circumference.

[0013] A method for detecting loose bolts for a planetary mixer, utilizing the above-mentioned detection system, the method comprising the following steps:

[0014] Using a camera assembly to acquire a three-dimensional point cloud image of the bolt assembly, thereby obtaining a depth map of the bolt assembly;

[0015] Using the depth map of the bolt assembly, the spatial position corresponding to each bolt in the bolt assembly is obtained, the corresponding bolt at each spatial position is recorded, and the bolts are numbered one by one;

[0016] Calculate the real-time height difference between the vertex of each bolt and the corresponding connection surface in the order of numbers;

[0017] By comparing the real-time height difference of a single bolt with the initial height difference, the looseness of the corresponding bolt can be determined.

[0018] As a further improvement of the above technical solution:

[0019] When using the camera assembly to acquire a three-dimensional point cloud image of the bolt assembly to obtain a depth map of the bolt assembly, two sets of camera assemblies are arranged to have two visual cameras, including the following steps:

[0020] S1. First, calibrate the two visual cameras separately and determine the working parameters of the two visual cameras respectively;

[0021] Based on the spatial position calibration technology, the two visual cameras are calibrated and the coordinate systems of the two visual cameras are aligned to the global coordinate system;

[0022] S2. The two visual cameras simultaneously begin collecting image data of the bolt assembly and continue collecting image data at a set interval.

[0023] S3 generates a timestamp for each acquired image data, generates a globally unique identification code based on the timestamp for each acquired image data, the identification code also includes the corresponding visual camera operating parameters to the acquired image data;

[0024] S4. Based on the image data obtained in step S3, denoising, alignment, registration, and surface reconstruction are performed by point cloud processing tools to generate a corresponding first three-dimensional point cloud image;

[0025] S5. Align the coordinates of the first three-dimensional point cloud image generated in step S4., thereby removing duplicate data and integrating the data, thereby generating a second three-dimensional point cloud image uniquely corresponding to each bolt, and generating a unique ID for the corresponding bolt based on the second three-dimensional point cloud image;

[0026] S6. Convert each second three-dimensional point cloud image obtained in step S5. into a corresponding depth map according to the working parameters of the two visual cameras.

[0027] Calculating the real-time height difference between the vertex of each bolt and the corresponding connection surface in numerical order includes the following steps:

[0028] First, the corresponding depth map is segmented to locate the bolt area and the connection surface area adjacent to the bolt;

[0029] Then, the depth values ​​of the bolt area are averaged or the lowest value is obtained to obtain a first depth value, and the depth values ​​of the connection surface area are averaged or the highest value is obtained to obtain a second depth value;

[0030] Finally, the difference between the first depth value and the second depth value is calculated and the absolute value is taken to obtain the real-time height difference.

[0031] By comparing the real-time height difference and the initial height difference of a single bolt, the looseness of the corresponding bolt is judged. If the absolute value of the difference between the real-time height difference and the initial height difference exceeds the set threshold, it is judged that the bolt is loose; otherwise, it is judged that the bolt is not loose.

[0032] The threshold is 1mm-2mm.

[0033] The beneficial effects of the present invention are as follows:

[0034] The present invention has a compact and reasonable structure and is easy to operate. By arranging a camera component, it can prevent and detect loose bolts in advance to avoid them falling onto materials and causing waste of materials. It has high efficiency and accuracy and can detect abnormal loose bolts in the mixer early. At the same time, by arranging a visual camera, it can collect image data of all bolts on the bottom of the planetary gearbox one by one, thereby constructing a three-dimensional point cloud based on the image data, and obtaining a depth map of each bolt based on the three-dimensional point cloud to obtain the depth data of each bolt, and then obtain the depth difference between the bolt and the connection surface. The detection accuracy is high, and non-destructive detection and non-contact detection can be realized. The detection process will not destroy the vacuum environment inside the mixer when it is working. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the detection method of the present invention.

[0036] Figure 2 Schematic diagram of the structure of the detection system in the present invention.

[0037] Figure 3 This is a schematic structural diagram of the mixer in the present invention when the container is omitted.

[0038] Figure 4 The structure of the camera assembly in the present invention is shown as follows Figure 1 .

[0039] Figure 5 The structure of the camera assembly in the present invention is shown as follows Figure 2 .

[0040] Figure 6 Schematic diagram of the internal structure of the mixer in the present invention.

[0041] Figure 7 for Figure 6 A partial enlarged view of point A in the middle.

[0042] Among them: 1. Mixer; 2. Bolt assembly; 3. Camera assembly;

[0043] 101. Container; 102. Vacuum cover; 103. Planetary gearbox; 104. Transmission box; 105. Stirring assembly; 106. Nozzle;

[0044] 301. Visual camera; 302. Rotary cylinder; 303. First mounting bracket; 304. Second mounting bracket; 305. Mounting base; 306. Scraper. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0046] like Figure 2-Figure 7As shown, this embodiment provides a bolt loosening detection system for a planetary mixer, including a mixer 1, a bolt assembly 2 is installed inside the mixer 1, and two symmetrically arranged camera assemblies 3 are installed outside the mixer 1. The two camera assemblies 3 take pictures of the bolt assembly 2 to determine whether the bolt assembly 2 is loose.

[0047] The bolt loosening detection system of this embodiment includes a mixer 1, a bolt assembly 2, and a camera assembly 3. By installing the camera assembly 3 at the two pipe openings 106 of the mixer 1, the image data of all the bolts at the bottom of the planetary gearbox 103 can be collected one by one by the visual camera 301 during the rotation of the planetary gearbox 103, so as to construct a three-dimensional point cloud based on the image data, and obtain a depth map of each bolt based on the three-dimensional point cloud to obtain the depth data of each bolt, and then obtain the depth difference between the bolt and the connection surface.

[0048] The mixer 1 includes a vacuum housing 102, with a transmission box 104 mounted on the top. A container 101 is mounted on the bottom of the vacuum housing 102. The interior of the container 101 interfaces with the interior of the vacuum housing 102, forming a workspace. A planetary gearbox 103 and a stirring assembly 105 connected to the output of the planetary gearbox 103 are located within the workspace. The input of the transmission box 104 is connected to a first motor, and the output of the transmission box 104 is connected to the housing of the planetary gearbox 103. The first motor drives the planetary gearbox 103 to rotate through the transmission box 104, thereby driving the stirring assembly 105 to orbit through the planetary gearbox 103. The input of the planetary gearbox 103 is connected to a second motor, which drives the stirring assembly 105 to rotate through the planetary gearbox 103. The stirring assembly 105 includes two stirring paddle mechanisms and two dispersion disk mechanisms, with two sets of dispersion disks arranged symmetrically. The individual stirring paddle mechanisms and individual dispersion disk mechanisms are alternately arranged.

[0049] A single stirring paddle mechanism includes a first rotating shaft, on the outer circumferential surface of which a stirring paddle is mounted. The first rotating shaft is connected to the output shaft corresponding to the planetary gearbox 103 through the first rotating shaft, so that the first rotating shaft can be driven to rotate by the planetary gearbox 103, thereby driving the corresponding stirring paddle to rotate.

[0050] A single dispersion disk mechanism includes a second rotating shaft, and a plurality of dispersion disks arranged along the axial direction are mounted on the outer circumferential surface of the second rotating shaft. The second rotating shaft is connected to the output shaft corresponding to the planetary gearbox 103 through the second rotating shaft, so that the second rotating shaft can be driven to rotate by the planetary gearbox 103, thereby driving the corresponding dispersion disk to rotate.

[0051] The side wall of the vacuum cover 102 is provided with two symmetrically arranged nozzles 106, each nozzle 106 extending obliquely downward, and a sight glass is mounted on the end of each nozzle 106. The sight glass is sealed with the corresponding nozzle 106 to ensure the vacuum degree in the working space.

[0052] The two camera assemblies 3 are respectively installed at the two pipe openings 106, which can ensure that the detection areas of the two visual cameras 301 cover the distribution area of ​​the bolt assembly 2, and the viewing angles between the visual cameras 301 have a certain overlapping area for subsequent data integration.

[0053] A single camera assembly 3 includes a mounting base 305 fixed to the corresponding nozzle 106. A first mounting bracket 303 and a second mounting bracket 304 are respectively fixed to the mounting base 305. A visual camera 301 is mounted on the first mounting bracket 303. The lens of the visual camera 301 faces the corresponding viewing mirror, and the visual camera 301 captures images of the interior of the workspace through the corresponding viewing mirror. A rotary cylinder 302 is mounted on the second mounting bracket 304. The output end of the rotary cylinder 302 passes through the corresponding viewing mirror and connects to a scraper 306 disposed inside the corresponding viewing mirror. The scraper 306 is in close contact with the inner end surface of the corresponding viewing mirror. The rotary cylinder 302 drives the scraper 306 to rotate, thereby scraping away material adhering to the inner end surface of the viewing mirror. In this embodiment, both visual cameras 301 are 3D visual cameras, capable of providing high-precision depth information with low error and high precision. Furthermore, to enhance the photographic effect, a 3D visual camera with an integrated light source can be used, which can automatically fill in the light during photography.

[0054] By setting the scraper 306, the material on the surface of the corresponding mirror can be scraped off, thereby preventing excessive material from accumulating inside the mirror and affecting the shooting accuracy of the visual camera 301, and effectively ensuring the detection effect.

[0055] The bolt assembly 2 includes several bolt groups, and a single bolt group includes several bolts distributed along the circumference. Figure 4-Figure 5 As shown, the bolt assembly 2 includes a first bolt group for fixing the bottom cover plate of the planetary gearbox 103, a second bolt group for connecting a first rotating shaft and the planetary gearbox 103, a third bolt group for connecting another first rotating shaft and the planetary gearbox 103, a fourth bolt group for connecting a second rotating shaft and the planetary gearbox 103, and a fifth bolt group for connecting another second rotating shaft and the planetary gearbox 103; the bolts in each bolt group are evenly spaced along the circumference.

[0056] The working process of the planetary mixer bolt loosening detection system of this embodiment is as follows:

[0057] Place the material to be mixed in the container 101, and fix the container 101 to the bottom of the vacuum cover 102 through a threaded connector. At the same time, install a sealing ring between the container 101 and the vacuum cover 102 to ensure the sealing performance of the container 101 and the inside of the vacuum cover 102;

[0058] The working space is evacuated through the vacuum port provided on the vacuum cover 102 until the set vacuum degree is reached;

[0059] Start the first motor and the second motor. The first motor drives the planetary gearbox 103 to rotate through the transmission box 104, thereby driving the stirring assembly 105 to revolve through the planetary gearbox 103. The second motor drives the stirring assembly 105 to rotate through the planetary gearbox 103.

[0060] The rotating stirring assembly 105 stirs, disperses and mixes the materials in the container 101;

[0061] At the same time, the two rotary cylinders 302 are activated to drive the corresponding scrapers 306 to rotate continuously, thus preventing the problem of material accumulation on the corresponding sight glasses;

[0062] The two visual cameras 301 are powered on and take photos of the bolt assembly 2 inside the mixer 1 at a preset interval. The two visual cameras 301 are electrically connected to the industrial computer and can transmit the taken photos back to the industrial computer. The photos are analyzed by the analysis software pre-stored in the industrial computer to obtain the looseness status of the bolts of the bolt assembly 2 inside the mixer 1.

[0063] like Figure 1 As shown, the planetary mixer bolt loosening detection method of this embodiment utilizes the above-mentioned detection system, and the method includes the following steps:

[0064] Using the camera assembly 3 to acquire a three-dimensional point cloud image of the bolt assembly 2, thereby obtaining a depth map of the bolt assembly 2;

[0065] In this embodiment, two visual cameras 301 are arranged to improve the image acquisition efficiency and ensure that the three-dimensional point cloud image corresponds one-to-one with the actual bolt. The specific process includes the following steps:

[0066] S1. First, the two visual cameras 301 are calibrated, respectively, to determine the operating parameters of the two visual cameras 301 to ensure that the camera can accurately capture information in three-dimensional space;

[0067] The working parameters include focal length, aperture, shutter speed, and internal parameters (such as distortion coefficient) and external parameters (such as the position and posture of the visual camera 301 in three-dimensional space) corresponding to each visual camera 301;

[0068] Based on the spatial position calibration technology, the two visual cameras 301 are calibrated, and the coordinate systems of the two visual cameras 301 are aligned to the global coordinate system to achieve coordinate alignment;

[0069] S2. The two visual cameras 301 simultaneously start collecting image data of the bolt assembly 2 and continue collecting image data at a set interval to ensure that the two visual cameras 301 always collect image data at the same time;

[0070] S3 generates a timestamp for each acquired image data, generates a globally unique identification code based on the timestamp for each acquired image data, the identification code also includes the corresponding visual camera 301 operating parameters of the acquired image data;

[0071] During the image acquisition process, ensure that the parameter settings of the camera component 3 remain unchanged to avoid data differences caused by parameter changes;

[0072] S4. Based on the image data obtained in step S3, denoising, alignment, registration, and surface reconstruction are performed by point cloud processing tools to generate a corresponding first three-dimensional point cloud image;

[0073] S5. Align the coordinates of the first 3D point cloud image generated in step S4 to remove duplicate data and perform data integration, thereby generating a second 3D point cloud image uniquely corresponding to each bolt. Based on the second 3D point cloud image, a unique ID is generated for the corresponding bolt to facilitate subsequent tracking.

[0074] S6. A depth map is an image generated by measuring the distance from the object surface to the camera, where the value of each pixel represents the distance from the point corresponding to that pixel to the camera. Each second 3D point cloud image obtained in step S5 is converted into a corresponding depth map based on the operating parameters of the two visual cameras 301.

[0075] The grayscale value of each depth map is converted to a z-coordinate in millimeters using the following formula:

[0076] z[mm]=gray2mm*g

[0077] Wherein, gray2mm is a constant, which is set to 1 in this embodiment;

[0078] g represents the grayscale value in the depth map;

[0079] The x and y coordinates of each pixel in each depth map are calculated using the following formula:

[0080] x[mm]=(u-cx)*z / f

[0081] y[mm]=(v-cy)*z / f

[0082] Where u represents the row in the corresponding depth map;

[0083] v represents the column in the corresponding depth map;

[0084] z represents the grayscale value of the corresponding depth map;

[0085] f represents the focal length of the corresponding visual camera 301;

[0086] cx and cy are both constants and can be obtained from the manual of the corresponding visual camera.

[0087] Analyze the depth map based on a neural network, use the depth map of the bolt assembly 2 to obtain the spatial position corresponding to each bolt in the bolt assembly 2, record the corresponding bolt at each spatial position and number the bolts one by one;

[0088] Calculate the real-time height difference between the vertex of each bolt and the corresponding connection surface in the order of numbering, including the following steps:

[0089] First, the corresponding depth map is segmented to locate the bolt area and the connection surface area adjacent to the bolt;

[0090] Then, the depth values ​​of the bolt area are averaged or the lowest value is obtained to obtain a first depth value, and the depth values ​​of the connection surface area are averaged or the highest value is obtained to obtain a second depth value;

[0091] Finally, the difference between the first depth value and the second depth value is calculated and the absolute value is taken to obtain the real-time height difference;

[0092] By comparing the real-time height difference of a single bolt with the initial height difference, the looseness of the corresponding bolt can be determined;

[0093] After the mixer 1 is assembled, the bolt assembly 2 inside the mixer 1 is initially scanned by the two-camera assembly 3, and the corresponding initial height difference is generated, and the initial height difference data is pre-stored in the industrial computer;

[0094] Each subsequent scan is compared with the first data. If the absolute value of the difference between the real-time height difference and the initial height difference exceeds the set threshold (the threshold can be 1mm-2mm), it is determined that the bolt is loose. Otherwise, it is determined that the bolt is not loose.

[0095] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any modifications may be made within the scope of protection of the present invention.

Claims

1. A bolt loosening detection system for a planetary mixer, characterized in that: The invention comprises a mixer (1), wherein a bolt assembly (2) is installed inside the mixer (1), and two symmetrically arranged camera assemblies (3) are installed outside the mixer (1). The two camera assemblies (3) take photos of the bolt assembly (2), thereby judging whether the bolt assembly (2) is loose.

2. The planetary mixer bolt loosening detection system according to claim 1, characterized in that: The mixer (1) comprises a vacuum cover (102), a transmission box (104) is mounted on the top of the vacuum cover (102), a container (101) is mounted on the bottom of the vacuum cover (102), the internal space of the container (101) is connected to the internal space of the vacuum cover (102) to form a working space, a planetary gear box (103) and a stirring assembly (105) connected to the output end of the planetary gear box (103) are arranged in the working space; The input end of the transmission box (104) is connected to a first motor, and the output end of the transmission box (104) is connected to a housing of a planetary gear box (103); the first motor drives the planetary gear box (103) to rotate through the transmission box (104), thereby driving the stirring assembly (105) to revolve through the planetary gear box (103); The input end of the planetary gear box (103) is connected to a second motor, and the second motor drives the stirring assembly (105) to rotate through the planetary gear box (103).

3. The planetary mixer bolt loosening detection system according to claim 2, characterized in that: Two symmetrically arranged pipe openings (106) are provided on the side wall surface of the vacuum cover (102), and a single pipe opening (106) extends obliquely downward, and a sight glass is mounted on the end of the single pipe opening (106).

4. The planetary mixer bolt loosening detection system according to claim 3, characterized in that: A single camera assembly (3) comprises a mounting seat (305) fixed on a corresponding pipe mouth (106), a first mounting frame (303) and a second mounting frame (304) being fixed on the mounting seat (305), respectively; a visual camera (301) is mounted on the first mounting frame (303), a lens of the visual camera (301) faces the corresponding viewing mirror, and the visual camera (301) takes pictures of the interior of the working space through the corresponding viewing mirror; a rotary cylinder (302) is mounted on the second mounting frame (304), an output end of the rotary cylinder (302) passes through the corresponding viewing mirror and is connected to a scraper (306) arranged on the inner side of the corresponding viewing mirror, the scraper (306) is in close contact with the inner end surface of the corresponding viewing mirror, and the rotary cylinder (302) drives the scraper (306) to rotate, thereby scraping off materials attached to the inner end surface of the viewing mirror.

5. The bolt loosening detection system for a planetary mixer according to claim 1, characterized in that: The bolt assembly (2) comprises several sets of bolt groups, and a single set of bolt groups comprises several bolts distributed along a circumference.

6. A method for detecting bolt loosening for a planetary mixer, characterized in that: Using the detection system according to any one of claims 1 to 5, the method comprises the following steps: Using a camera assembly (3) to acquire a three-dimensional point cloud image of the bolt assembly (2), thereby obtaining a depth map of the bolt assembly (2); Using the depth map of the bolt assembly (2), obtaining the spatial position corresponding to each bolt in the bolt assembly (2), recording the corresponding bolt at each spatial position and numbering the bolts one by one; According to the serial number sequence, calculate the real-time height difference between the vertex of each bolt and the corresponding connection surface; By comparing the real-time height difference of a single bolt with the initial height difference, the looseness degree of the corresponding bolt can be determined.

7. The method for detecting bolt loosening for a planetary mixer according to claim 6, characterized in that: When using a camera assembly (3) to acquire a three-dimensional point cloud image of a bolt assembly (2) to obtain a depth map of the bolt assembly (2), two groups of camera assemblies (3) are arranged to provide two visual cameras (301), including the following steps: S1. First, the two visual cameras (301) are calibrated respectively, and the working parameters of the two visual cameras (301) are determined respectively; Based on the spatial position calibration technology, the two visual cameras (301) are calibrated, and the coordinate systems of the two visual cameras (301) are aligned to the global coordinate system to achieve coordinate alignment; S2. The two visual cameras (301) simultaneously start collecting image data of the bolt assembly (2), and continue collecting image data at a set interval; S3. Generate a timestamp for each acquired image data, and generate a globally unique identification code for each acquired image data based on the timestamp, the identification code also includes the working parameters of the corresponding visual camera (301) for acquiring the image data; S4. Based on the image data obtained in step S3., denoising, alignment, registration and surface reconstruction are performed by point cloud processing tools to generate a corresponding first three-dimensional point cloud image; S5. Aligning the coordinates of the first three-dimensional point cloud image generated in step S4., thereby removing duplicate data for data integration, and then generating a second three-dimensional point cloud image uniquely corresponding to each bolt, and generating a unique ID for the corresponding bolt based on the second three-dimensional point cloud image; S6. According to the working parameters of the two visual cameras (301), each second three-dimensional point cloud image acquired in step S5. is converted into a corresponding depth map.

8. The method for detecting bolt loosening for a planetary mixer according to claim 6, characterized in that: Calculating the real-time height difference between the vertex of each bolt and the corresponding connection surface in the order of numbers includes the following steps: First, the corresponding depth map is segmented to locate the bolt area and the connection surface area adjacent to the bolt; Then, the depth values ​​of the bolt area are averaged or the lowest value is calculated to obtain a first depth value, and the depth values ​​of the connection surface area are averaged or the highest value is calculated to obtain a second depth value; Finally, the difference between the first depth value and the second depth value is calculated and the absolute value is taken to obtain the real-time height difference.

9. The method for detecting bolt loosening for a planetary mixer according to claim 6, characterized in that: By comparing the real-time height difference and the initial height difference of a single bolt, the degree of looseness of the corresponding bolt is judged. If the absolute value of the difference between the real-time height difference and the initial height difference exceeds the set threshold, it is judged that the bolt is loose, otherwise, it is judged that the bolt is not loose.

10. The method for detecting bolt looseness for a planetary mixer according to claim 9, characterized in that: The threshold is 1mm-2mm.

Images