Image feature point comparison-based storage tank landing guidance system and method

Abstract

The application relates to a storage tank landing guiding system and method based on image feature point comparison, and relates to the technical field of automatic control of material hoisting. The guiding system is applied to an automatic radioactive powder material feeding system. The automatic radioactive powder material feeding system comprises a lower support, a carrying trolley, a storage tank and a crane. The guiding system comprises a depth camera, a horizontal conveying part and a positioning mark part. The storage tank landing guiding method based on image feature point comparison is based on the guiding system. The steps are as follows: 1, shooting a reference image and recording feature point data; 2, multi-dimensional posture judgment based on feature point comparison; and 3, space offset judgment and space offset adjustment. The application is applied to an existing automatic radioactive powder material feeding system, realizes automatic adjustment and alignment during the hoisting and placing of the storage tank, does not need manual close-range operation, and avoids radioactive irradiation of the operator during close-range operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automatic control of material hoisting, and in particular to a storage tank landing guiding system and method based on image feature point comparison. BACKGROUND

[0002] Uranium ore is the main raw material for preparing nuclear fuel. In the entire preparation process from uranium ore to nuclear fuel, two steps of uranium purification and uranium conversion will be experienced. The UO2 powder produced by the uranium purification step is stored in a specially designed storage tank for later use. When the uranium conversion step is reached, the UO2 powder in the storage tank needs to be discharged into a transfer bin, which is referred to as the UO2 feeding operation. Since the UO2 powder is radioactive, relevant production enterprises have been committed to the research and development of UO2 automatic feeding technology in order to reduce the risk of radiation exposure to front-line operators.

[0003] A batch of content-related invention patents with an application date of August 8, 2023 (Uranium dioxide powder storage tank and its disassembly and cover method (CN116913569), Radioactive powder negative pressure conveying link and its application method (CN117023152), Gas path conveying type radioactive powder feeding system (CN116853823) and gas path conveying type radioactive powder feeding method (2023109869971)) disclose a set of radioactive powder material automatic feeding system and its corresponding feeding method, which realizes the automatic feeding operation of UO2 powder in the uranium conversion process.

[0004] Taking the gas path conveying type radioactive powder feeding system (CN116853823) as an example, referring to paragraph 0037 of its specification, in the first step of the feeding operation, the hoisting and placing of the storage tank is involved: the storage tank to be fed is hoisted to the placement station of the carrying trolley by a cantilever crane; during the hoisting process, first, the guide wheel set rolls in contact with the guide edge of the storage tank, playing a role in correcting deviation, then the inclined surface inside the guide enclosure slides in contact with the guide edge of the storage tank, playing a role in centering; finally, the storage tank is accurately positioned in the placement station of the carrying trolley.

[0005] However, the above-mentioned hoisting and placing process has the following difficulties in actual operation: the original design intention of the feeding system is to reduce the risk of radiation exposure to front-line operators. In theory, the operator should stand far away to control the crane, but the size of the mouth-shaped area surrounded by the guide wheel set around the placement station of the carrying trolley basically matches the size of the rectangular area formed by the four legs at the lower end of the storage tank, and the adjustable space is small. The accuracy of the position during the hoisting and placing of the storage tank is relatively high, and the operator still needs to observe and adjust at close range in actual operation to ensure the accuracy of the placing position, which poses a risk of radioactive exposure.

[0006] Under the premise of adjusting the accuracy of the lowering position, the guide edges of the two bottom plates at the lower end of the storage tank will be in contact with two rows of oppositely arranged guide roller sets at the same time, at which time the storage tank is guided in the vertical direction. In the case of deviation of the lowering position from the reasonable position, the lower end support leg or the bottom plate of the storage tank will collide with the guide roller set, thereby causing the storage tank to tilt and shake, affecting the smooth execution of the lifting and placing operation, and there is a certain safety hazard. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art and provide a storage tank falling position guiding system and method based on image feature point comparison, which is applied to an existing radioactive powder material automatic feeding system, and solves the problem that the storage tank lifting and placing process has high requirements for position accuracy when the feeding system performs feeding operation, and thus requires manual close-range operation (observation and adjustment), which has the risk of radioactive radiation.

[0008] The technical scheme of the present application is: a storage tank falling position guiding system based on image feature point comparison, which is applied to a radioactive powder material automatic feeding system; the radioactive powder material automatic feeding system comprises a lower support, a carrying trolley, a storage tank and a crane; the lower support is directly or indirectly fixedly installed on the ground, and two parallel arranged horizontal rails are arranged on the lower support; the carrying trolley is provided with a plurality of horizontally arranged guide roller sets at the upper end, all the guide roller sets are arranged at the same height and jointly enclose a plurality of mouth-shaped areas, each mouth-shaped area is a placing station, and the carrying trolley is provided with a discharging hole in each placing station; the carrying trolley is provided with rollers on both sides at the lower end, and the carrying trolley is movably installed on the two horizontal rails through the rollers; the storage tank is internally provided with an inner cavity for containing UO2 powder, the center of the lower end of the storage tank is provided with an outer protective cover, four support legs are evenly welded in a ring shape on the outer wall of the lower end of the storage tank, and each two support legs are fixedly connected with a strip-shaped bottom plate at the lower end, and there are two parallel arranged bottom plates; the crane is used for lifting and placing the storage tank placed on the ground into the placing station of the carrying trolley, when the storage tank is lifted and placed into any placing station of the carrying trolley, the outer protective cover of the storage tank is located directly above the discharging hole in the placing station;

[0009] The guiding system comprises a depth camera, a horizontal conveying member and a positioning mark; a plurality of horizontal conveying members are respectively fixedly installed beside each blanking hole at the lower end of the carrier trolley and correspond to the blanking holes one by one; a plurality of depth cameras are respectively fixedly installed on each horizontal conveying member and correspond to the horizontal conveying members one by one, each depth camera moves into or exits the area below the corresponding blanking hole under the drive of the corresponding horizontal conveying member, there is a shooting position in the path of the depth camera moving to the area below the blanking hole, when the depth camera is at the shooting position, the center line of the lens of the depth camera is vertically upward arranged to obtain a vertically upward shooting angle, the depth camera and the corresponding blanking hole form a relatively fixed placement orientation and positional relationship; at least two positioning marks are fixedly pasted on the lower end surface of the outer protective cover of the storage tank, which provides the basis for the depth camera to shoot and identify and provide the storage tank position adjustment.

[0010] A further technical solution of the present application is that the horizontal conveying member is a linear motor, and the positioning mark is a self-luminous patch.

[0011] A further technical solution of the present application is that the guiding system further comprises a hemispherical glass cover, and the hemispherical glass cover is installed on the horizontal conveying member and covers the depth camera inside.

[0012] A further technical solution of the present application is that the number of positioning marks is two, and the straight-line distance between the center points of the two positioning marks is 0.75-0.95D, where D is the diameter of the lower end surface of the outer protective cover of the storage tank.

[0013] The technical solution of the present application is a storage tank landing guiding method based on image feature point comparison, based on the above guiding system, the steps are as follows:

[0014] S01, shooting a reference image and recording feature point data:

[0015] After the crane is controlled to hoist the storage tank to the reference position directly above any installation station, the corresponding horizontal conveying member is driven to move the corresponding depth camera to the shooting position below the installation station, the depth camera is started to take a picture, the picture obtained by shooting is defined as a reference image, an image coordinate system is established in the reference image, the x-axis and y-axis in the image coordinate system are the length and width directions of the image respectively; the included angle between the line connecting the two positioning marks in the reference image and the x-axis is recorded, which is used for subsequent horizontal angle determination of the storage tank; the straight-line distance of the two positioning marks in the reference image is recorded, which is used for subsequent vertical height difference determination of the lower end surface of the bottom plate of the storage tank and the depth camera; the depth information and the depth difference of the two positioning marks in the reference image are recorded, which is used for subsequent vertical inclination determination of the storage tank; the corresponding relationship between the unit distance of the x-axis in the reference image and the moving distance of the crane along the x-axis is established, and the corresponding relationship between the unit distance of the y-axis in the reference image and the moving distance of the crane along the y-axis is established.

[0016] In this step, the crane can translate along the x-axis and y-axis in the horizontal plane, the x-axis of the crane is parallel to the x-axis of the image coordinate system, and the y-axis of the crane is parallel to the y-axis of the image coordinate system;

[0017] In this step, the positioning mark is simplified as a feature point to facilitate data recording, which is the center point of the area occupied by the positioning mark in the reference image;

[0018] In this step, the correspondence between the straight-line distance of the two positioning marks in the reference image and the vertical height difference between the lower end face of the storage tank bottom plate and the depth camera is determined as prior knowledge;

[0019] In this step, when the storage tank is in the reference position, the distance between the lower end face of the storage tank bottom plate and the uppermost point of the guide roller set is s, the value of s is in the range of 2-4 cm, the center line of the storage tank coincides with the center line of the discharge hole below it, and the outer edges of the two bottom plates are respectively parallel to the two oppositely arranged guide roller sets below them;

[0020] S02, multi-dimensional posture determination based on feature point comparison:

[0021] After the crane is controlled to hoist the storage tank above any installation station, the corresponding horizontal conveying member is driven to move the corresponding depth camera to the shooting position below the installation station, and the depth camera is started to take continuous photos; while controlling the storage tank to slowly descend, the descending speed is determined by whether the storage tank shakes or not; during the shooting and lowering process, vertical tilt determination and horizontal angle determination are simultaneously performed; both vertical tilt determination and horizontal angle determination are completed before the storage tank is lowered to the reference height;

[0022] In this step, the vertical tilt determination is as follows: the difference between the depth values of the two positioning marks in each frame of the shooting image is calculated, and the calculated depth difference is compared with the pre-stored depth difference; if they are consistent, it indicates that the storage tank is in a vertical posture, and no additional operation is taken, if they are inconsistent, it indicates that the storage tank has vertical tilt, then the crane immediately controls the storage tank to move away from the upper end of the installation station and puts the storage tank back on the ground, and after the operator checks and adjusts the steel cable connection, the storage tank is hoisted again;

[0023] In this step, the horizontal angle determination is as follows: the included angle between the line connecting the two positioning marks in each frame of the shooting image and the x-axis is calculated, and the calculated included angle is compared with the pre-stored included angle; if they are consistent, it indicates that the storage tank meets the requirements in horizontal orientation, and no additional operation is taken, if they are inconsistent, it indicates that the storage tank has horizontal deflection, then the crane is controlled to pause lowering the storage tank, and according to the difference between the current included angle and the pre-stored included angle, the crane is controlled to act to rotate the storage tank by the corresponding difference angle, so that the current included angle and the pre-stored included angle are consistent;

[0024] In this step, the reference height refers to the height of the storage tank at the reference position;

[0025] In this step, the same shooting parameters as when the reference image is shot are used when the depth camera takes a picture;

[0026] S03, spatial offset determination and spatial offset adjustment:

[0027] When the storage tank that meets the horizontal angle determination and the vertical tilt determination is lowered to the reference height, the depth camera is started to take a picture, and an image coordinate system is established in the current image, the x-axis and y-axis in the image coordinate system are the length and width directions of the image respectively, and the positions of the two positioning markers in the image coordinate system are obtained; any one of the positioning markers is selected, the position J1 of the positioning marker in the image coordinate system of the current image is compared with the position J2 of the positioning marker in the image coordinate system of the reference image, the x-axis unit distance and y-axis unit distance required for the positioning marker to move from position J1 to position J2 are obtained, and then the distance that the crane needs to control to move is obtained according to the corresponding relationship between the x-axis unit distance in the reference image and the distance moved by the crane along the x-axis and the corresponding relationship between the y-axis unit distance in the reference image and the distance moved by the crane along the y-axis, and the crane is controlled to move, so that the storage tank is moved to the reference position; the crane controls the storage tank to slowly drop, and through the guiding effect of the guide roller set arranged around the placement station, the storage tank is finally stably landed in the target placement station;

[0028] In this step, the same shooting parameters as when the reference image is shot are used when the depth camera takes a picture;

[0029] In this step, the x and y axis unit distances in the current image are consistent with the x and y axis unit distances in the reference image.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] 1. It is applied in the existing automatic radioactive powder material feeding system, realizes automatic adjustment and alignment during the hoisting and dropping process of the storage tank, does not need manual close-range operation (observation and adjustment), and avoids the radioactive irradiation of the operator during close-range operation.

[0032] 2. It does not use the traditional photographing image comparison scheme, but performs posture determination based on the depth recognition of feature points (positioning markers) by the depth camera. This scheme is not affected by environmental light conditions, has good applicability, and can perform posture determination in multiple dimensions, including storage tank vertical tilt determination, storage tank horizontal angle determination, and storage tank spatial offset determination. According to the determination results, the storage tank is adjusted in multiple dimensions, and then the storage tank is accurately adjusted to the reference position, and after being adjusted to the reference position, it is vertically dropped to accurately land in the placement station of the carrying trolley. Attached Figure Description

[0033] Figure 1 This is a structural diagram of the automatic feeding system for radioactive powder materials used in this invention;

[0034] Figure 2 This is a diagram showing the installation position of the positioning marker on the storage tank in this invention;

[0035] Figure 3 This is a diagram showing the storage tank in its baseline position from a bottom-up view of the bottom of the transport trolley.

[0036] Figure 4 This is a diagram showing the storage tank not being in the reference position, viewed from below the bottom of the transport trolley.

[0037] Figure 5 This diagram shows the installation positions of the horizontal conveyor and the depth camera at the bottom of the transport trolley.

[0038] Legend: 1. Lower support; 11. Horizontal track; 2. Carrying trolley; 21. Drop hole; 22. Roller; 23. Guide wheel assembly; 3. Storage tank; 31. Outer protective cover; 32. Support leg; 33. Base plate; 4. Horizontal conveyor; 5. Depth camera; 6. Positioning marker.

[0039] Special Note: Figures 3-4 The bottom plate of the medium transport trolley is semi-transparent, so that the position of the four legs and two bottom plates of the storage tank can be clearly seen through the bottom plate. Implementation

[0040] Example

[0041] like Figures 1-5 As shown, a storage tank positioning guidance system based on image feature point comparison is applied to an automatic feeding system for radioactive powder materials. The automatic feeding system for radioactive powder materials includes, but is not limited to, a lower support 1, a transport trolley 2, a storage tank 3, and a crane (not shown in the figure).

[0042] The lower support 1 is directly or indirectly fixedly installed on the ground, and two parallel horizontal tracks 11 are arranged on the lower support 1. The upper end of the carrier trolley 2 is provided with a plurality of horizontally arranged guide wheel groups 23, all the guide wheel groups 23 are arranged at the same height and jointly enclose a plurality of mouth-shaped areas, each mouth-shaped area is a placing station, and the carrier trolley 2 is provided with a blanking hole 21 in each placing station. The lower end of the carrier trolley 2 is provided with a roller 22 on each side, and the carrier trolley 2 is movably installed on the two horizontal tracks 11 through the rollers 22. The inside of the storage tank 3 is provided with an inner cavity for containing UO2 powder, the lower end of the storage tank 3 is provided with an outer protective cover 31, and four support legs 32 are evenly welded in a ring shape on the outer wall of the lower end of the storage tank 3. Each two support legs 32 are fixedly connected with a strip-shaped bottom plate 33 at the lower end, and there are two parallel bottom plates 33. The crane is used to hoist the storage tank 3 placed on the ground into the placing station of the carrier trolley 2, and when the storage tank 3 is hoisted into any placing station of the carrier trolley 2, the outer protective cover 31 of the storage tank 3 is located directly above the blanking hole 21 in the placing station.

[0043] The guiding system comprises horizontal conveying members 4, depth cameras 5 and positioning markers 6. A plurality of horizontal conveying members 4 are fixedly installed beside each blanking hole 21 at the lower end of the carrier trolley 2 and correspond to the blanking holes 21 one by one. A plurality of depth cameras 5 are fixedly installed on the horizontal conveying members 4 and correspond to the horizontal conveying members 4 one by one. Each depth camera 5 moves into or exits the area below the corresponding blanking hole 21 under the drive of the corresponding horizontal conveying member 4. There is a shooting position in the path of the depth camera 5 moving to the area below the blanking hole 21. When the depth camera 5 is at the shooting position, the center line of the lens of the depth camera 5 is vertically upward arranged to obtain a vertically upward shooting angle. The depth camera 5 and the corresponding blanking hole 21 form a relatively fixed placement orientation and positional relationship. At least two positioning markers 6 are fixedly attached to the lower end surface of the outer protective cover 31 of the storage tank 3, which provides a basis for the depth camera 5 to shoot and identify and adjust the position of the storage tank 3.

[0044] Preferably, the horizontal conveying member 4 is a linear motor, and the positioning marker 6 is a self-luminous patch.

[0045] Preferably, the guiding system further comprises a hemispherical glass cover (not shown in the figure), which is installed on the horizontal conveying member 4 and covers the depth camera 5 inside. The hemispherical glass cover is provided for dustproof of the lens of the depth camera.

[0046] Preferably, the number of positioning markers 6 is two, and the straight-line distance between the center points of the two positioning markers 6 is 0.75-0.95D, D being the diameter of the lower end surface of the outer protective cover 31 of the storage tank 3.

[0047] Briefly describe the working principle of the present application:

[0048] The storage tank landing guiding method based on image feature point comparison is based on the guiding system described above, and the steps are as follows:

[0049] S01, shooting reference image and feature point data recording:

[0050] After the crane is controlled to hoist the storage tank to the reference position above any installation station, the corresponding horizontal conveying member is driven to move the corresponding depth camera to the shooting position below the installation station, the depth camera is started to take a picture, the picture obtained by shooting is defined as a reference image, an image coordinate system is established in the reference image, the x-axis and y-axis in the image coordinate system are the length and width directions of the image respectively; the included angle between the connecting line of the two positioning mark members in the reference image and the x-axis is recorded, which is used for subsequent storage tank horizontal angle determination; the straight line distance of the two positioning mark members in the reference image is recorded, which is used for subsequent determination of the vertical height difference between the lower end face of the storage tank bottom plate and the depth camera; the depth information and depth difference of the two positioning mark members in the reference image are recorded, which are used for subsequent storage tank vertical inclination determination; the corresponding relationship between the unit distance of the x-axis in the reference image and the moving distance of the crane along the x-axis is established, and the corresponding relationship between the unit distance of the y-axis in the reference image and the moving distance of the crane along the y-axis is established.

[0051] In this step, the crane can be translated along the x-axis and y-axis in the horizontal plane, the x-axis of the crane is parallel to the x-axis of the image coordinate system, and the y-axis of the crane is parallel to the y-axis of the image coordinate system.

[0052] In this step, the positioning mark member is simplified as a feature point for data recording, and the feature point is the center point of the area occupied by the positioning mark member in the reference image.

[0053] In this step, the corresponding relationship between the "straight line distance of the two positioning mark members in the reference image" and the "vertical height difference between the lower end face of the storage tank bottom plate and the depth camera" is determined as prior knowledge.

[0054] In this step, when the storage tank is at the reference position, the distance between the lower end face of the storage tank bottom plate and the uppermost point of the guide roller set is s, the value range of s is 2-4 cm, the center line of the storage tank coincides with the center line of the lower discharge hole, and the outer edges of the two bottom plates are respectively parallel to the two oppositely arranged guide roller sets below.

[0055] S02, multi-dimensional posture determination based on feature point comparison:

[0056] After the crane is used to lift the storage tank to any placement position, the corresponding horizontal conveyor is driven to move the corresponding depth camera to the shooting position below the placement position and start taking continuous pictures. At the same time, the storage tank is controlled to descend slowly, with the descent speed being such that the storage tank does not shake. During the taking pictures and lowering process, vertical tilt determination and horizontal deflection determination are performed simultaneously. Both vertical tilt determination and horizontal deflection determination are completed before the storage tank is lowered to the reference height.

[0057] In this step, the vertical tilt determination is as follows: calculate the difference in depth values ​​between the two positioning markers in each frame of the captured image, and compare the calculated difference in depth values ​​with the pre-stored depth difference value; if they match, it means that the storage tank is in a vertical position and no additional operation is required; if they do not match, it means that the storage tank has tilted vertically, and the crane will immediately control the storage tank to move it away from the upper end of the placement position and put the storage tank back on the ground. After the operator checks and adjusts the steel cable connection, the storage tank will be hoisted again.

[0058] In this step, the horizontal deflection angle is determined as follows: Calculate the angle between the line connecting the two positioning markers in each frame of the captured image and the x-axis, and compare the calculated angle with the pre-stored angle; if they match, it means that the storage tank meets the horizontal orientation requirements, and no additional operation is required; if they do not match, it means that the storage tank has deflected horizontally, so control the crane to pause lowering the storage tank, and then control the crane to rotate the storage tank by the corresponding difference angle according to the difference between the current angle and the pre-stored angle, so that the current angle matches the pre-stored angle.

[0059] In this step, the reference height refers to the height of the storage tank at the reference position.

[0060] In this step, the depth camera takes pictures using the same shooting parameters as when shooting the reference image.

[0061] S03, Spatial Offset Determination and Spatial Offset Adjustment:

[0062] Once the storage tank, meeting both the horizontal tilt and vertical tilt criteria, descends to the reference height, a depth camera is activated to take a picture. An image coordinate system is established in the current image, with the x-axis and y-axis representing the length and width of the image, respectively. The positions of the two positioning markers in the image coordinate system are obtained. One of the positioning markers is selected, and its position J1 in the current image's coordinate system is compared with its position J2 in the reference image's coordinate system. This yields the x-axis and y-axis unit distances required for the marker to move from position J1 to position J2. Based on the correspondence between the x-axis unit distance in the reference image and the crane's x-axis movement distance, and the y-axis unit distance in the reference image and the crane's y-axis movement distance, the required crane movement distance is determined. The crane is then controlled to move the storage tank to the reference position. The crane then slowly lowers the storage tank, guided by the guide wheels around the placement station, ensuring the tank lands smoothly in the target placement station.

[0063] In this step, the depth camera takes pictures using the same shooting parameters as when shooting the reference image.

[0064] In this step, the unit distances on the x and y axes in the current image are consistent with the unit distances on the x and y axes in the reference image.

Claims

1. A storage tank placement guidance system based on image feature point comparison, applied to an automatic feeding system for radioactive powder materials; the automatic feeding system for radioactive powder materials includes a lower support, a transport trolley, a storage tank, and a crane; the lower support is directly or indirectly fixed to the ground, and has two rows of parallel horizontal tracks on it; the upper end of the transport trolley has multiple horizontally arranged guide wheel groups, all of which are arranged at the same height and together form multiple U-shaped areas, each U-shaped area being a placement station, and the transport trolley has a material dropping hole in each placement station; the lower end of the transport trolley has two sides... The trolley is equipped with rollers and is mounted on two horizontal tracks via rollers. The storage tank has an inner cavity for holding UO2 powder. An outer protective cover is located at the center of the lower end of the storage tank. Four legs are evenly welded in a ring on the outer wall of the lower end of the storage tank. A strip-shaped base plate is fixedly connected to the lower end of each pair of legs. There are two parallel base plates in total. The crane is used to lift the storage tank placed on the ground to the placement position of the trolley. When the storage tank is lifted to any placement position of the trolley, the outer protective cover of the storage tank is located directly above the material drop hole in that placement position. Its characteristics are: The guiding system includes depth cameras, horizontal conveyors, and positioning markers. Multiple horizontal conveyors are fixedly installed next to each material drop hole at the lower end of the transport trolley, corresponding one-to-one with the drop holes. Multiple depth cameras are fixedly installed on each horizontal conveyor, corresponding one-to-one with the horizontal conveyor. Each depth camera moves under the drive of its corresponding horizontal conveyor, entering or exiting the area below the corresponding drop hole. There are shooting positions along the path of the depth camera moving to the area below the drop hole. When the depth camera is in the shooting position, the center line of the depth camera lens is vertically upward to obtain a vertically upward shooting angle. The depth camera and its corresponding drop hole form a relatively fixed orientation and positional relationship. At least two positioning markers are affixed and fixed at intervals to the lower end face of the outer protective cover of the storage tank, providing a basis for depth camera identification and thus adjusting the position of the storage tank.

2. The storage tank positioning guidance system based on image feature point comparison as described in claim 1, characterized in that: The horizontal conveyor is a linear motor, and the positioning marker is a self-illuminating patch.

3. The storage tank positioning guidance system based on image feature point comparison as described in claim 2, characterized in that: The guidance system also includes a hemispherical glass dome, which is mounted on the horizontal conveyor and houses the depth camera.

4. The storage tank positioning guidance system based on image feature point comparison as described in claim 3, characterized in that: There are two positioning markers, and the straight-line distance between the center points of the two positioning markers is 0.75-0.95D, where D is the diameter of the lower end face of the outer protective cover of the storage tank.

5. A storage tank placement guidance method based on image feature point comparison, based on the storage tank placement guidance system based on image feature point comparison as described in any one of claims 1-4; Its characteristic is that the steps as follows: S01, Capture the baseline image and record the feature point data: After the crane is used to lift the storage tank to the reference position directly above any placement station, the corresponding horizontal conveyor is driven to move the corresponding depth camera to the shooting position below the placement station. The depth camera is then activated to take a picture, and the resulting image is defined as the reference image. An image coordinate system is established in the reference image, with the x-axis and y-axis representing the length and width of the image, respectively. The angle between the line connecting the two positioning markers in the reference image and the x-axis is recorded for subsequent determination of the horizontal deflection angle of the storage tank. The straight-line distance between the two positioning markers in the reference image is also recorded for subsequent determination of the vertical height difference between the lower end face of the storage tank bottom plate and the depth camera. Record the depth information and depth difference of the two positioning markers in the reference image for subsequent vertical tilt determination of the storage tank; establish the correspondence between the unit distance on the x-axis in the reference image and the distance the crane moves along the x-axis, and establish the correspondence between the unit distance on the y-axis in the reference image and the distance the crane moves along the y-axis. In this step, the crane can translate along the x-axis and y-axis on the horizontal plane. The crane's x-axis is parallel to the x-axis of the image coordinate system, and the crane's y-axis is parallel to the y-axis of the image coordinate system. In this step, the positioning marker is simplified into a single feature point to facilitate data recording. The feature point is the center point of the area occupied by the positioning marker in the reference image. In this step, the correspondence between "the straight-line distance between the two positioning markers in the reference image" and "the vertical height difference between the bottom surface of the storage tank and the depth camera" is determined as prior knowledge. In this step, when the storage tank is in the reference position, the distance between the lower end face of the bottom plate of the storage tank and the highest point of the upper end of the guide wheel assembly is s. The value of s ranges from 2 to 4 cm. The center line of the storage tank coincides with the center line of the material drop hole below it. The outer edges of the two bottom plates of the storage tank are parallel to the two guide wheel assemblies arranged opposite to each other below it. S02, Multi-dimensional pose determination based on feature point comparison: After the crane is used to lift the storage tank to above any placement position, the corresponding horizontal conveyor is driven to move the corresponding depth camera to the shooting position below the placement position, and the depth camera is started to take continuous pictures. While controlling the storage tank to descend slowly, the descent speed should be such that the storage tank does not shake; during the process of taking pictures and lowering, vertical tilt judgment and horizontal deflection angle judgment are performed simultaneously; both vertical tilt judgment and horizontal deflection angle judgment are completed before the storage tank is lowered to the reference height; In this step, the vertical tilt is determined as follows: calculate the difference in depth values ​​between the two positioning markers in each frame of the captured image, and compare the calculated difference in depth values ​​with the pre-stored depth difference value; if they match, it means that the storage tank is in a vertical position and no additional operation is required; if they do not match, it means that the storage tank is vertically tilted, and the crane immediately controls the storage tank to be moved away from the upper end of the placement position and put back on the ground. After the operator checks and adjusts the steel cable connection, the storage tank is lifted again. In this step, the horizontal deflection angle is determined as follows: calculate the angle between the line connecting the two positioning markers in each frame of the captured image and the x-axis, and compare the calculated angle with the pre-stored angle. If they match, it means that the storage tank meets the requirements in terms of horizontal orientation, and no additional operation is required. If they do not match, it means that the storage tank has been deflected horizontally. In this case, the crane is controlled to stop lowering the storage tank, and then the crane is controlled to rotate the storage tank by the corresponding difference angle according to the difference between the current angle and the pre-stored angle, so that the current angle matches the pre-stored angle. In this step, the reference height refers to the height of the storage tank at the reference position; In this step, the depth camera takes pictures using the same shooting parameters as when shooting the reference image; S03, Spatial Offset Determination and Spatial Offset Adjustment: Once the storage tank, meeting both the horizontal tilt and vertical tilt criteria, descends to the reference height, a depth camera is activated to take a picture. An image coordinate system is established in the current image, with the x-axis and y-axis representing the length and width of the image, respectively. The positions of the two positioning markers in the image coordinate system are obtained. One of the positioning markers is selected, and its position J1 in the current image's coordinate system is compared with its position J2 in the reference image's coordinate system. This yields the x-axis and y-axis unit distances required for the marker to move from position J1 to position J2. Based on the correspondence between the x-axis unit distance in the reference image and the crane's x-axis movement distance, and the correspondence between the y-axis unit distance in the reference image and the crane's y-axis movement distance, the required crane movement distance is determined. The crane is then controlled to move the storage tank to the reference position. The crane then slowly lowers the storage tank, guided by the guide wheels around the placement station, ensuring the tank lands smoothly in the target placement station. In this step, the depth camera takes pictures using the same shooting parameters as when shooting the reference image; In this step, the unit distances on the x and y axes in the current image are consistent with the unit distances on the x and y axes in the reference image.

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