A cargo positioning system based on crane

Abstract

The present invention relates to the field of crane control technology, and in particular to a cargo positioning system based on a crane. The present invention lifts cargo through a lifting mechanism, a positioning mechanism, obtains cargo images, a detection module obtains a clamp force value, and obtains a cargo movement trajectory during the cargo lifting process. A classification unit identifies a cargo center point according to the cargo image, controls the clamp to clamp the cargo, controls the lifting mechanism to lift the cargo to a preset height and maintains it for a preset time, calculates a cargo stability characterization value to classify the cargo, a control unit selects a cargo positioning strategy according to the cargo category, and a determination unit determines whether cargo positioning identification is accurate according to the cargo movement trajectory during the cargo lifting process. The present invention classifies cargo according to weight balance and adopts different cargo positioning methods for different categories of cargo, thereby preventing cargo from tilting during the cargo lifting process and improving the safety of crane operation.

Description

Technical Field

[0001] The invention relates to the technical field of crane control, and in particular to a cargo positioning system based on a crane. Background Art

[0002] A crane is a piece of mechanical equipment used to move cargo, and is commonly used in various fields such as industry, construction, and ports. It is able to move in both vertical and horizontal directions, and can lift and lower various types and weights of cargo. It is very important to ensure that the crane is clamped accurately when clamping cargo, in order to prevent the cargo from being clamped unsteadily, thereby reducing potential risks.

[0003] Chinese Patent Publication No.: CN115092822A, discloses an unmanned crane control system, which solves the technical problems of poor positioning accuracy and low positioning efficiency of manually controlled cranes; the present invention obtains a construction site image of a construction site through an image acquisition device, a data processing module receives the construction site image, establishes a two-dimensional model of the construction site according to the high-definition image of the construction site, establishes a rectangular coordinate system on the two-dimensional model of the construction site with the crane position as the origin, and obtains the coordinates of the cargo storage position, the coordinates of the cargo target position, the first arm length and the second arm length; the intelligent control module controls the rotating mechanism of the crane according to the cargo storage position coordinates, controls the operating mechanism of the crane according to the first arm length, controls the rotating mechanism of the crane according to the cargo target position coordinates, and controls the operating mechanism of the crane according to the first arm length, thereby improving the positioning efficiency and positioning accuracy of the crane.

[0004] However, there are still the following problems in the prior art:

[0005] In the prior art, consideration is not given to how cargo with uneven gravity should be positioned during clamping, and precise positioning methods are not adopted according to different types of cargo, resulting in poor safety in cargo clamping and certain operational risks during crane operation. Summary of the invention

[0006] To this end, the present invention provides a cargo positioning system based on a crane to overcome the problems in the prior art that how cargo with uneven gravity should be positioned during clamping is not considered, and accurate positioning methods are not adopted according to different types of cargo, resulting in poor safety of cargo clamping and certain operational risks during crane operation.

[0007] To achieve the above object, the present invention provides a cargo positioning system based on a crane, comprising:

[0008] A lifting mechanism, comprising a clamp for clamping the cargo, and a crane arm connected to the clamp for lifting the cargo;

[0009] A positioning mechanism, including an image acquisition unit for acquiring an image of the cargo;

[0010] The detection module includes a force sensing unit arranged on the fixture to obtain the force value of the fixture, and a video acquisition unit to obtain the movement trajectory of the cargo during the cargo lifting process;

[0011] The upper computer is connected to the lifting mechanism, the positioning mechanism and the detection module respectively, and includes a classification unit, a control unit and a determination unit.

[0012] The classification unit is used to identify the center point of the cargo according to the cargo image, control the clamp to move to the top of the center point of the cargo to clamp any opposite side of the cargo, control the lifting mechanism to lift the cargo to a preset height and hold it for a preset time, calculate the cargo stability characterization value according to the angle between the cargo and the horizontal plane and the force difference of the clamp, and classify the cargo according to the cargo stability characterization value;

[0013] The control unit is used to select a strategy for positioning the cargo according to the cargo category, including:

[0014] Identify the center point of the cargo, locate the cargo according to the center point of the cargo, control the clamp to move above the center point of the cargo, clamp any opposite side of the cargo and lift the cargo;

[0015] Control the clamp to clamp the four bottom corners of the goods in sequence and lift them to the preset measurement height, obtain the force value of the clamp when clamping each bottom corner, identify the gravity tilt side, select the clamp moving position, control the clamp to move to the clamp moving position to clamp the designated opposite side of the goods and lift the goods;

[0016] The determination unit determines whether the cargo positioning identification is accurate according to the cargo movement trajectory during the cargo lifting process.

[0017] Furthermore, the classification unit extracts a cargo contour according to the cargo image, and identifies a center point of the cargo contour as a cargo center point.

[0018] Furthermore, the classification unit calculates the cargo stability characterization value according to formula (1):

[0019]

[0020] In formula (1), W represents the stability characterization value of the cargo, θ represents the angle between the cargo and the horizontal plane, θ0 represents the preset angle threshold, F represents the clamp force difference, F0 represents the preset clamp force difference threshold, and the clamp force difference is the difference between the maximum clamp force value and the minimum clamp force value when the lifting mechanism holds the cargo at a preset height for a preset time.

[0021] Furthermore, the classification unit compares the cargo stability characterization value with a preset cargo stability characterization value comparison threshold value.

[0022] If the cargo stability characterization value is less than a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity balance category;

[0023] If the cargo stability characterization value is greater than or equal to a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity imbalance class.

[0024] Furthermore, the control unit selects a strategy for positioning the cargo according to the cargo category, wherein:

[0025] If the cargo category is gravity balanced, the control unit selects and identifies the center point of the cargo, positions the cargo according to the center point of the cargo, controls the clamp to move to the top of the center point of the cargo, clamps any opposite side of the cargo, and lifts the cargo;

[0026] If the cargo category is a gravity imbalance category, the control unit selects the control clamp to clamp the four bottom corners of the cargo in sequence and lift them to the preset measuring height, obtains the force value of the clamp when clamping each bottom corner, identifies the gravity tilted side, selects the clamp moving position, controls the clamp to move to the clamp moving position to clamp the specified opposite side of the cargo and lift the cargo.

[0027] Furthermore, the control unit obtains the force value of the clamp when the clamp clamps each bottom angle, sums the force values ​​of the two clamps corresponding to the two bottom angles on the same side to obtain the force sum value, and identifies the side with the largest force sum value as the gravity tilt side.

[0028] Furthermore, the control unit selects the clamp movement position according to the ratio of the sum of forces on the gravity inclined side and the side opposite to the gravity inclined side, wherein the ratio of the distance between the clamping position and the side opposite to the gravity inclined side and the distance between the clamping position and the gravity inclined side is the ratio of the sum of forces on the gravity inclined side and the side opposite to the gravity inclined side.

[0029] Furthermore, the control unit controls the clamp to move to the clamp moving position to clamp the goods on two sides adjacent to the gravity inclined side.

[0030] Furthermore, the determination unit identifies the cargo contour moving path as a cargo motion trajectory, and fits the cargo motion trajectory with the cargo sample motion trajectory in the sample library to obtain a fitting value.

[0031] Furthermore, the determination unit compares the fitting value with a preset fitting value comparison threshold value. If the fitting value is greater than the preset fitting value comparison threshold value, the determination unit determines that the cargo positioning identification is accurate.

[0032] Compared with the prior art, the present invention lifts the cargo by a lifting mechanism, the positioning mechanism obtains the cargo image, the detection module obtains the force value of the clamp, and obtains the cargo movement trajectory during the cargo lifting process. The classification unit identifies the center point of the cargo according to the cargo image, controls the clamp to clamp the cargo, controls the lifting mechanism to lift the cargo to a preset height and maintain it for a preset time, calculates the cargo stability characterization value to classify the cargo, the control unit selects a cargo positioning strategy according to the cargo category, and the judgment unit determines whether the cargo positioning and identification is accurate according to the cargo movement trajectory during the cargo lifting process. The present invention classifies the cargo according to the weight balance and adopts different cargo positioning methods for different categories of cargo, thereby preventing the cargo from tilting during the cargo lifting process and improving the safety of the crane operation.

[0033] In particular, the classification unit of the present invention calculates the cargo stability characterization value based on the angle between the cargo and the horizontal plane and the force difference of the clamp. In actual situations, the weight of the cargo is not necessarily balanced. When the weight of the cargo is unbalanced, the center position of the clamped cargo will cause the cargo to shift during the lifting process. The angle between the cargo and the horizontal plane and the force difference of the clamp are important parameters for determining whether the cargo is shifted. Calculating the cargo stability characterization value can provide data reference for subsequent use.

[0034] In particular, the classification unit of the present invention divides the cargo categories according to the cargo stability characterization value. When the cargo stability characterization value is small, it can be judged to a certain extent that the weight of the cargo is relatively balanced. At this time, it is only necessary to obtain the center point of the cargo outline when positioning the cargo. When the cargo stability characterization value is large, it can be judged to a certain extent that the weight of the cargo is relatively unbalanced. At this time, the cargo cannot be positioned according to the center point of the cargo outline. By classifying the cargo categories, inaccurate cargo positioning and identification during the operation of the crane can be prevented, which may cause the cargo to tilt or even fall, thereby improving the operating safety of the crane.

[0035] In particular, the control unit of the present invention controls the clamp to clamp the four bottom corners of the cargo in sequence and lift them to a preset measuring height, obtains the force value of the clamp when clamping each bottom corner, and identifies the gravity tilt side. Since the weight of the cargo is uneven, other methods should be adopted to position the cargo at this time. By lifting the four bottom corners of the cargo and clamping the force values ​​of each bottom corner, the gravity distribution of the cargo can be characterized to a certain extent, thereby providing effective data support for cargo positioning and improving the safety of crane operation.

[0036] In particular, the determination unit of the present invention determines whether the cargo positioning and identification is accurate based on the cargo movement trajectory during the cargo lifting process. When the cargo position is reliably identified, the crane operation process is stable, and the cargo movement trajectory should be highly consistent with the cargo movement trajectory in the sample library when the crane is operating smoothly. By comparing the fitting values, it can be determined whether the current cargo positioning and identification is accurate, thereby improving the safety of the crane operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural diagram of a cargo positioning system based on a crane according to an embodiment of the invention;

[0038] Figure 2 This is a structural diagram of a host computer of a cargo positioning system based on a crane according to an embodiment of the invention;

[0039] Figure 3 A logical decision diagram for classifying goods into categories by the classification unit of the embodiment of the invention;

[0040] Figure 4 This is a logical decision diagram for a decision unit in an embodiment of the present invention to determine whether cargo location identification is accurate. DETAILED DESCRIPTION

[0041] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; 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.

[0042] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0043] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] See also Figure 1-Figure 4 As shown, Figure 1 This is a structural diagram of a cargo positioning system based on a crane according to an embodiment of the invention. Figure 2 This is a structural diagram of the host computer of the cargo positioning system based on a crane according to an embodiment of the invention. Figure 3 A logical decision diagram for classifying goods into categories by the classification unit of the embodiment of the invention, Figure 4 The logic determination diagram of whether the cargo positioning identification is accurate is determined by the determination unit of the embodiment of the invention. The cargo positioning system based on the crane of the present invention comprises:

[0045] A lifting mechanism, comprising a clamp for clamping the cargo, and a crane arm connected to the clamp for lifting the cargo;

[0046] A positioning mechanism, including an image acquisition unit for acquiring an image of the cargo;

[0047] The detection module includes a force sensing unit arranged on the fixture to obtain the force value of the fixture, and a video acquisition unit to obtain the movement trajectory of the cargo during the cargo lifting process;

[0048] The upper computer is connected to the lifting mechanism, the positioning mechanism and the detection module respectively, and includes a classification unit, a control unit and a determination unit.

[0049] The classification unit is used to identify the center point of the cargo according to the cargo image, control the clamp to move to the top of the center point of the cargo to clamp any opposite side of the cargo, control the lifting mechanism to lift the cargo to a preset height and hold it for a preset time, calculate the cargo stability characterization value according to the angle between the cargo and the horizontal plane and the force difference of the clamp, and classify the cargo according to the cargo stability characterization value;

[0050] The control unit is used to select a strategy for positioning the cargo according to the cargo category, including:

[0051] Identify the center point of the cargo, locate the cargo according to the center point of the cargo, control the clamp to move above the center point of the cargo, clamp any opposite side of the cargo and lift the cargo;

[0052] Control the clamp to clamp the four bottom corners of the goods in sequence and lift them to the preset measurement height, obtain the force value of the clamp when clamping each bottom corner, identify the gravity tilt side, select the clamp moving position, control the clamp to move to the clamp moving position to clamp the designated opposite side of the goods and lift the goods;

[0053] The determination unit determines whether the cargo positioning identification is accurate according to the cargo movement trajectory during the cargo lifting process.

[0054] Specifically, the present invention does not limit the specific structure of the clamp. A clamp that matches the size of the goods is selected according to the size of the goods. The clamp can stably clamp the goods. This is existing technology and will not be described in detail.

[0055] Specifically, the present invention does not limit the specific structure of the image acquisition unit, which can be an industrial CCD camera that can acquire images of goods. This is a prior art and will not be described in detail.

[0056] Specifically, the present invention does not limit the specific structure of the detection module. The force sensing unit can be a force sensor, which can obtain the force value of the clamp clamping the goods. The video acquisition unit can be a camera, which can obtain the video of the cargo lifting process. This is the existing technology and will not be repeated.

[0057] Specifically, the present invention does not limit the specific structure of the upper computer. The classification unit, control unit and determination unit can all be composed of logical components or a combination of logical components. The logical components include a field programmable processor, a computer or a microprocessor in a computer. This is a prior art and will not be repeated here.

[0058] In this embodiment, the cargo contour of the cargo image is extracted by image analysis software, and the image analysis software may be ImageJ or MATLAB, which is a prior art and will not be described in detail.

[0059] Specifically, the classification unit extracts the cargo outline according to the cargo image, and identifies the center point of the cargo outline as the cargo center point.

[0060] Specifically, the classification unit calculates the cargo stability characterization value according to formula (1):

[0061]

[0062] In formula (1), W represents the stability characterization value of the cargo, θ represents the angle between the cargo and the horizontal plane, θ0 represents the preset angle threshold, F represents the clamp force difference, F0 represents the preset clamp force difference threshold, and the clamp force difference is the difference between the maximum clamp force value and the minimum clamp force value when the lifting mechanism holds the cargo at a preset height for a preset time.

[0063] In this embodiment, θ0 is selected within the range of [0°, 3°], F0 is obtained in advance from the experiment, a clamping test is performed on the gravity-balanced cargo in advance, the clamp is controlled to move to above the center point of the gravity-balanced cargo to clamp any opposite sides of the cargo, the lifting mechanism is controlled to lift the gravity-balanced cargo to a preset height and maintain it for a preset time, and the average force difference Fe of the clamp is obtained. It is assumed that F0=a×Fe, a is the force difference coefficient, 0.9<a<1.1.

[0064] In this embodiment, the preset height is selected within the range of [0.3m, 0.5m], and the preset duration is selected within the range of [20s, 30s].

[0065] Specifically, the classification unit of the present invention calculates the cargo stability characterization value based on the angle between the cargo and the horizontal plane and the force difference of the clamp. In actual situations, the weight of the cargo is not necessarily balanced. When the weight of the cargo is unbalanced, the center position of the clamped cargo will cause the cargo to shift during the lifting process. The angle between the cargo and the horizontal plane and the force difference of the clamp are important parameters for determining whether the cargo is shifted. Calculating the cargo stability characterization value can provide data reference for the follow-up.

[0066] Specifically, the classification unit compares the cargo stability characterization value with a preset cargo stability characterization value comparison threshold value.

[0067] If the cargo stability characterization value is less than a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity balance category;

[0068] If the cargo stability characterization value is greater than or equal to a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity imbalance class.

[0069] In this embodiment, the preset cargo stability characterization value comparison threshold is selected within the range of [1, 1.3].

[0070] Specifically, the classification unit of the present invention classifies cargo categories according to the cargo stability characterization value. When the cargo stability characterization value is small, it can be judged to a certain extent that the weight of the cargo is relatively balanced. At this time, it is only necessary to obtain the center point of the cargo outline when positioning the cargo. When the cargo stability characterization value is large, it can be judged to a certain extent that the weight of the cargo is relatively unbalanced. At this time, the cargo cannot be positioned according to the center point of the cargo outline. By classifying cargo categories, inaccurate cargo positioning and identification during crane operation can be prevented, which may cause the cargo to tilt or even fall, thereby improving the operating safety of the crane.

[0071] Specifically, the control unit selects a strategy for positioning the cargo according to the cargo category, wherein:

[0072] If the cargo category is gravity balanced, the control unit selects and identifies the center point of the cargo, positions the cargo according to the center point of the cargo, controls the clamp to move to the top of the center point of the cargo, clamps any opposite side of the cargo, and lifts the cargo;

[0073] If the cargo category is a gravity imbalance category, the control unit selects the control clamp to clamp the four bottom corners of the cargo in sequence and lift them to the preset measuring height, obtains the force value of the clamp when clamping each bottom corner, identifies the gravity tilted side, selects the clamp moving position, controls the clamp to move to the clamp moving position to clamp the specified opposite side of the cargo and lift the cargo.

[0074] In this embodiment, the cargo is a cube with a side length of ZA. The control clamp sequentially clamps the four bottom corners of the cargo, and the preset measurement height of the lift is selected within the range of [0.5ZA, 0.8ZA].

[0075] Specifically, the control unit obtains the force value of the clamp when the clamp clamps each bottom angle, sums the force values ​​of the two clamps corresponding to the two bottom angles on the same side to obtain the force sum value, and identifies the side with the largest force sum value as the gravity tilt side.

[0076] In this embodiment, the four bottom corners are the upper left corner, the lower left corner, the upper right corner, and the lower right corner. The upper left corner and the lower left corner are on the same side, named the left side, the upper left corner and the upper right corner are on the same side, named the back side, the upper right corner and the lower right corner are on the same side, named the right side, and the lower left corner and the lower right corner are on the same side, named the front side. There are four sides in total. The sum of forces on each side is calculated. For example, the sum of forces on the left side is the sum of the force value of the clamp when clamping the upper left corner and the force value of the clamp when clamping the lower left corner. If the sum of forces on the left side is the largest among the four sides, the left side is the gravity inclined side. It can be understood that the gravity value of the gravity inclined side is larger. If the clamp clamps the middle position of the two adjacent sides of the gravity inclined side of the cargo, the cargo will tilt toward the gravity inclined side.

[0077] Specifically, the control unit selects the clamp movement position according to the ratio of the sum of forces on the gravity inclined side and the side opposite to the gravity inclined side, wherein the ratio of the distance between the clamping position and the side opposite to the gravity inclined side to the distance between the clamping position and the gravity inclined side is the ratio of the sum of forces on the gravity inclined side and the side opposite to the gravity inclined side.

[0078] Specifically, the control unit controls the clamp to move to the clamp moving position to clamp the goods on both sides adjacent to the gravity inclined side.

[0079] It can be understood that if the left side is the gravity inclined side, the front side and the rear side are two sides adjacent to the gravity inclined side.

[0080] Specifically, the control unit of the present invention controls the clamp to clamp the four bottom corners of the cargo in sequence and lift them to a preset measuring height, obtains the force value of the clamp when clamping each bottom corner, and identifies the gravity tilt side. Since the weight of the cargo is uneven, other methods should be adopted to position the cargo at this time. By lifting the four bottom corners of the cargo and clamping the force values ​​of each bottom corner, the gravity distribution of the cargo can be characterized to a certain extent, thereby providing effective data support for cargo positioning and improving the safety of crane operation.

[0081] Specifically, the determination unit identifies the moving path of the cargo contour as a cargo motion trajectory, fits the cargo motion trajectory with the cargo sample motion trajectory in the sample library, and obtains a fitting value.

[0082] In this embodiment, the sample library stores the movement trajectories of goods with the same contour running stably during the lifting process.

[0083] Specifically, the determination unit compares the fitting value with a preset fitting value comparison threshold. If the fitting value is greater than the preset fitting value comparison threshold, the determination unit determines that the cargo positioning identification is accurate.

[0084] In this embodiment, the preset fitting value comparison threshold is selected within the range of [0.95, 1].

[0085] Specifically, the determination unit of the present invention determines whether the cargo positioning and identification is accurate based on the cargo movement trajectory during the cargo lifting process. When the cargo position is reliably identified, the crane operation process is stable, and the cargo movement trajectory should be highly consistent with the cargo movement trajectory in the sample library when the crane is operating smoothly. By comparing the fitting values, it can be determined whether the current cargo positioning and identification is accurate, thereby improving the safety of the crane operation.

[0086] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A cargo positioning system based on a crane, characterized in that: include: A lifting mechanism, comprising a clamp for clamping the cargo, and a crane arm connected to the clamp for lifting the cargo; A positioning mechanism, including an image acquisition unit for acquiring an image of the cargo; The detection module includes a force sensing unit arranged on the fixture to obtain the force value of the fixture, and a video acquisition unit to obtain the movement trajectory of the cargo during the cargo lifting process; The upper computer is connected to the lifting mechanism, the positioning mechanism and the detection module respectively, and includes a classification unit, a control unit and a determination unit. The classification unit is used to identify the center point of the cargo according to the cargo image, control the clamp to move to the top of the center point of the cargo to clamp any opposite side of the cargo, control the lifting mechanism to lift the cargo to a preset height and hold it for a preset time, calculate the cargo stability characterization value according to the angle between the cargo and the horizontal plane and the force difference of the clamp, and classify the cargo according to the cargo stability characterization value; The control unit is used to select a strategy for positioning the cargo according to the cargo category, including: Identify the center point of the cargo, locate the cargo according to the center point of the cargo, control the clamp to move above the center point of the cargo, clamp any opposite side of the cargo and lift the cargo; Control the clamp to clamp the four bottom corners of the goods in sequence and lift them to the preset measurement height, obtain the force value of the clamp when clamping each bottom corner, identify the gravity tilt side, select the clamp moving position, control the clamp to move to the clamp moving position to clamp the designated opposite side of the goods and lift the goods; The determination unit determines whether the cargo positioning identification is accurate according to the cargo movement trajectory during the cargo lifting process.

2. The crane-based cargo positioning system according to claim 1, characterized in that: The classification unit extracts a cargo outline according to the cargo image, and identifies a center point of the cargo outline as a cargo center point.

3. The crane-based cargo positioning system of claim 1, wherein: The classification unit calculates the cargo stability characterization value according to formula (1): In formula (1), W represents the stability characterization value of the cargo, θ represents the angle between the cargo and the horizontal plane, θ0 represents the preset angle threshold, F represents the clamp force difference, F0 represents the preset clamp force difference threshold, and the clamp force difference is the difference between the maximum clamp force value and the minimum clamp force value when the lifting mechanism holds the cargo at a preset height for a preset time.

4. The crane-based cargo positioning system according to claim 3, characterized in that: The classification unit compares the cargo stability characterization value with a preset cargo stability characterization value comparison threshold value, If the cargo stability characterization value is less than a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity balance class; If the cargo stability characterization value is greater than or equal to a preset cargo stability characterization value comparison threshold, the classification unit classifies the cargo into a gravity imbalance class.

5. The crane-based cargo positioning system according to claim 4, characterized in that: The control unit selects a strategy for positioning the cargo according to the cargo category, wherein: If the cargo category is gravity balanced, the control unit selects and identifies the center point of the cargo, positions the cargo according to the center point of the cargo, controls the clamp to move to the top of the center point of the cargo, clamps any opposite side of the cargo, and lifts the cargo; If the cargo category is a gravity imbalance category, the control unit selects the control clamp to clamp the four bottom corners of the cargo in sequence and lift them to the preset measuring height, obtains the force value of the clamp when clamping each bottom corner, identifies the gravity tilted side, selects the clamp moving position, controls the clamp to move to the clamp moving position to clamp the specified opposite side of the cargo and lift the cargo.

6. The crane-based cargo positioning system of claim 1, wherein: The control unit obtains the force value of the clamp when the clamp clamps each bottom angle, sums the force values ​​of the two clamps corresponding to the two bottom angles on the same side to obtain the force sum value, and identifies the side with the largest force sum value as the gravity tilt side.

7. The crane-based cargo positioning system of claim 6, wherein: The control unit selects the clamp movement position according to the ratio of the sum of the forces on the gravity inclined side and the side opposite to the gravity inclined side, wherein the ratio of the distance between the clamping position and the side opposite to the gravity inclined side to the distance between the clamping position and the gravity inclined side is the ratio of the sum of the forces on the gravity inclined side and the side opposite to the gravity inclined side.

8. The crane-based cargo positioning system of claim 7, wherein: The control unit controls the clamp to move to the clamp moving position to clamp the goods on both sides adjacent to the gravity inclined side.

9. The crane-based cargo positioning system of claim 1, wherein: The determination unit identifies the cargo contour moving path as the cargo motion trajectory, fits the cargo motion trajectory with the cargo sample motion trajectory in the sample library, and obtains a fitting value.

10. The crane-based cargo positioning system of claim 9, wherein: The determination unit compares the fitting value with a preset fitting value comparison threshold, and if the fitting value is greater than the preset fitting value comparison threshold, the determination unit determines that the cargo positioning identification is accurate.

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