Cracking and embracing type variable-curvature gripper based on logarithmic spiral curve and operation method thereof

Abstract

The invention discloses a holding type variable-curvature gripper based on a logarithmic spiral curve and an operation method of the holding type variable-curvature gripper. The cable-embracing type variable-curvature gripper comprises a variable-curvature gripping arm and a driving rope. When the variable-curvature grabbing arm grabs an object, the variable-curvature grabbing arm is pulled by the driving rope to be bent in the direction of the grabbed object, the grabbed object is pushed, and by means of the gradually-increased bending curvature of the variable-curvature grabbing arm, the front end of the variable-curvature grabbing arm is curled to catch the object, and the grabbed object is gradually bound to the position with the moderate curvature. Grabbing force closing is formed at the contact point of the variable-curvature gripper and the grabbed object through the pulling force of the driving rope, and enveloping of the grabbed object is achieved. The mechanical arm is composed of a rigid structure, a variable-curvature holding type grabbing mode based on the logarithmic spiral curve is adopted, the mechanical arm has the advantages of being high in grabbing stability, adaptability and accuracy and low in structure control complexity, and objects of different sizes and shapes can be grabbed.

Description

Technical Field

[0001] This invention relates to the field of mechanical gripper technology, specifically to a gripper with variable curvature based on a logarithmic spiral curve and its operation method. Background Technology

[0002] With the rapid development of robotics technology, various mechanical grippers are being used in production and daily life. Therefore, mechanical grippers require high gripping stability and speed, as well as flexible gripping range and good adaptability. These are often contradictory. Currently, the main solutions are rigid mechanical grippers and soft mechanical grippers. Rigid mechanical grippers grip objects very firmly and efficiently, but they require high positional accuracy of the gripped object, have limited flexibility, and are less adaptable to complex and changing working environments. Soft mechanical grippers are usually made of soft materials, have a high degree of freedom in gripping, and possess advantages such as good compliance and strong adaptability. However, due to the low stiffness of the material itself, their gripping force, load-bearing capacity, gripping speed, and stability are far inferior to rigid mechanical grippers. Therefore, they are often configured with three or more grippers to form a gripping device to improve related performance, but this also brings problems such as complex system structure and control. Summary of the Invention

[0003] To meet the operational requirements of high stability, speed, flexible gripping range, and good adaptability of mechanical grippers, this invention provides a design method for realizing logarithmic spiral curve bending based on a rigid structure linkage bending form, as well as a hugging-type variable curvature gripper based on a logarithmic spiral curve.

[0004] The technical solution adopted by this invention to address the shortcomings of existing technologies is as follows:

[0005] According to a first aspect of this specification, a cradle-type variable curvature gripper based on a logarithmic spiral curve is provided. The cradle-type variable curvature gripper includes a drive rope and a variable curvature gripping arm. The variable curvature gripping arm is composed of a plurality of gripping components, each gripping component including a rigid frame and two rigid linkage units. The rigid linkage units have through holes at both ends.

[0006] The rigid frame is a hollow square frame that is symmetrical from left to right. It has two through holes in the center, the same size as the through holes on the rigid connecting rod unit, extending horizontally through each other. Each side of the rigid frame has two square slots, the width of which is the same as the thickness of the rigid connecting rod unit, allowing the rigid connecting rod unit to pass through the square slots and be hinged to the through holes on the rigid frame via the through holes on the rigid connecting rod unit. The lower end of the rigid frame has two symmetrical arc-shaped bosses, and the upper end has another arc-shaped boss. The distance between the two lower arc-shaped bosses is equal to the width of the upper arc-shaped boss. Above each boss is a through hole of the same size and position, allowing the rigid frame to be hinged to another rigid frame end-to-end via the through holes on the upper and lower arc-shaped bosses.

[0007] The rigid frame of the gripping component has two rigid connecting rod units in the square slots on the left and right sides, and they are hinged through through holes. These two rigid connecting rod units pass through the square slots on the left and right sides of the rigid frame of the next gripping component, and are hinged to the square slots on the left and right sides of the rigid frame of the next gripping component through through holes.

[0008] The rigid frame has several circular threading holes on the arc-shaped bosses at both ends. The drive rope passes through the threading hole starting from the first rigid frame, then passes through the threading holes on the same side of the rigid frame as the variable curvature gripping arm, and finally passes through the threading hole of the last rigid frame and is fixed. The other side of the variable curvature gripping arm also passes through another drive rope. By pulling the drive ropes on both sides, the bending control of the variable curvature gripping arm is achieved.

[0009] The variable curvature gripping arm adopts a logarithmic spiral curve variable curvature bending design. Given any logarithmic spiral curve, each rigid frame is placed sequentially starting from the end of the logarithmic spiral curve. The starting position of the first rigid frame is at the end of the logarithmic spiral curve, and the end position is inside the logarithmic spiral curve but does not fall on the logarithmic spiral curve. The end of the second rigid frame is hinged to the end of the first rigid frame, and its end position falls on the logarithmic spiral curve. The remaining links are continuously placed in the above manner to form a series structure in which every two rigid frames form a bending unit.

[0010] Furthermore, in the variable curvature gripping arm, each rigid frame is considered as a link. The angle between the line connecting the point of the second link of each bending unit on the logarithmic spiral curve and the origin, and the line connecting the point of the first link on the logarithmic spiral curve and the origin, is a fixed angle, called the bending angle of the bending unit, denoted as θ. The angle between the first link of each bending unit and the line connecting its point on the logarithmic spiral curve and the origin is another fixed angle, denoted as α. By controlling the angle γ between the first and second links in each bending unit, the lengths of the two links can be changed. The lengths of all sequentially connected links are successively reduced by a specific ratio β.

[0011] The length of all links is calculated and modeled to obtain the angle γ between the first and second links in each bending unit and the reduction ratio β, thereby calculating the point in each bending unit that falls inside the logarithmic spiral curve.

[0012] Furthermore, in the variable curvature gripping arm, two rigid linkage units are considered as stacked rods, and an inverse four-bar linkage structure is introduced through the design of stacked rods; the first linkage of each bending unit has a first stacked rod hinge hole in the middle, and the second linkage has a second stacked rod hinge hole in the middle. The first stacked rod hinge hole of this bending unit and the first stacked rod hinge hole of the next bending unit are respectively hinged to the two ends of a stacked rod, and the second stacked rod hinge hole of this bending unit and the second stacked rod hinge hole of the next bending unit are respectively hinged to the two ends of another stacked rod. Each stacked rod... Each of the two hinged links and the intersecting but not connected links constitutes a reverse four-bar linkage unit. In the first reverse four-bar linkage unit, the lengths of the two hinged holes on the corresponding links are m and n, respectively. After determining the link lengths related to the helical shape, two arbitrary values ​​m and n are given within the length range to determine the length of the intermediate stacked links and the hinged hole positions of the stacked links. Each reverse four-bar linkage unit gradually shrinks according to a uniform ratio. In the k-th reverse four-bar linkage unit, the lengths of the two hinged holes on the corresponding links are correspondingly reduced to m and n, respectively. and

[0013] Furthermore, the rigid linkage unit includes two connectors and two fixed narrow plates. The connectors are T-shaped with a through hole at the top and two threaded holes at the bottom. The fixed narrow plates are rectangular with two countersunk holes at each end. The two threaded holes on the connectors are connected to the countersunk holes on the fixed narrow plates by bolts. The rigid linkage unit has one symmetrically arranged connector at the top and bottom, which is connected to the left and right sides of the T-shape by the fixed narrow plates.

[0014] According to a first aspect of this specification, a method for operating a cradle-type variable curvature gripper based on a logarithmic spiral curve is provided, the method comprising the following steps:

[0015] S1. In the initial state of the grasping task, the variable curvature grasping arm is in a vertically extended state, and the drive rope is in a slack state.

[0016] S2. Move the variable curvature gripper to the side of the object being gripped, pull the drive rope on the side of the object being gripped, so that the variable curvature gripper bends towards the object being gripped, and the drive rope changes from a slack state to a taut state.

[0017] S3. After the object being grasped is pushed by the variable curvature gripper, the drive rope is pulled further. With the help of the gradually increasing curvature of the variable curvature gripper arm, the front end curls up to embrace the object, gradually binding the object to a position with a suitable curvature, thus completing the embrace. The drive rope remains taut. The tension of the drive rope forms a gripping force closure at the contact point between the variable curvature gripper and the object being grasped, achieving a stable envelope gripping of the object being grasped.

[0018] S4. After the gripping is completed, release the drive rope on this side and pull the drive rope on the other side to make the variable curvature gripping arm extend vertically. This completes one workflow.

[0019] Furthermore, the drive rope of the embracing variable curvature gripper can be pulled by a drive motor, controlling the motor rotation to achieve a gripping effect at a specified speed and acceleration.

[0020] Furthermore, the gripper with variable curvature is fixed to the robotic arm via a connecting seat, and the gripper works with the robotic arm to complete complex grasping tasks.

[0021] Furthermore, the variable curvature gripping arm produces different variable curvature gripping effects according to different logarithmic spiral curves; the greater the pulling force and speed of the drive rope, the greater the gripping force and speed of the variable curvature gripping arm.

[0022] The beneficial effects of this invention are as follows: The gripping components of this invention are all composed of rigid structures, enabling rapid and secure gripping, and providing high gripping stability. This invention employs a variable curvature gripping method based on a logarithmic spiral curve. During the gripping process, the object being gripped is pushed, and with the help of the gradually increasing curvature of the variable curvature gripping arm, the front end curls to embrace the object, gradually binding objects of different sizes to a position with a suitable curvature. The tension of the driving rope forms a gripping force closure at the contact point between the variable curvature gripper and the object, achieving high gripping adaptability and accuracy. This invention is a single-arm embracing gripping method, with lower structural and control complexity. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a logarithmic spiral curve mechanical structure based on a rigid structure with linked bending.

[0025] Figure 2A schematic diagram of a three-dimensional structure of a cradle-type variable curvature gripper based on a logarithmic spiral curve;

[0026] Figure 3 This is a schematic diagram illustrating the effect of a cradle-type variable curvature gripper based on a logarithmic spiral curve in grasping smaller objects.

[0027] Figure 4 This is a schematic diagram illustrating the effect of a cradle-type variable curvature gripper based on a logarithmic spiral curve in grasping a large object.

[0028] Figure 5 To capture a schematic diagram of the component's 3D structure;

[0029] Figure 6 This is a schematic diagram of a rigid linkage unit structure. Detailed Implementation

[0030] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0031] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0032] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] Example 1

[0034] This embodiment provides a design method for achieving logarithmic spiral curve bending based on a rigid structure linkage bending form. Specifically, it includes: given an arbitrary logarithmic spiral curve, each rigid link is sequentially placed starting from the end point of the logarithmic spiral curve. The starting position of the first link is at the end point of the logarithmic spiral curve, and the end position is inside the logarithmic spiral curve but does not fall on the logarithmic spiral curve. The end of the second link is hinged to the end of the first link, and its end position falls on the logarithmic spiral curve. The remaining links are continuously placed in the above manner to form a series structure in which every two links form a bending unit.

[0035] In this context, the angle between the line connecting the second link of each bending unit to the origin on the logarithmic spiral curve and the line connecting the first link of each bending unit to the origin on the logarithmic spiral curve is a fixed angle, called the bending angle of the bending unit, denoted as θ; the angle between the first link of each bending unit and the line connecting its point to the origin on the logarithmic spiral curve is another fixed angle, denoted as α; it can be found that by controlling the angle γ between the first and second links in each bending unit, the lengths of the two links can be changed.

[0036] In this process, the connecting rods of each bending unit are reduced by a specific ratio, and the connecting rods of adjacent bending units are also reduced by a specific ratio, and the reduction ratio is the same, denoted as β. That is, all the connecting rods connected in sequence are reduced in sequence according to the ratio β.

[0037] Based on the above conditions, the length of all links is calculated and modeled to obtain the angle γ between the first and second links in each bending unit and the reduction ratio β. Thus, the points in each bending unit that fall inside the logarithmic spiral curve are calculated. These calculated points that fall inside the logarithmic spiral curve also fall on another logarithmic spiral curve similar to the logarithmic spiral curve, which is reflected in the same spiral rate, only the minimum radius and the maximum radius are reduced accordingly.

[0038] The following detailed explanation, using specific examples, illustrates the calculation process for the included angle γ and the reduction ratio β between the two links in each bending element. For instance... Figure 1 As shown, given any logarithmic spiral curve, including the minimum radius r, maximum radius R, and total number of spiral turns l, let... Then any point (x) on the logarithmic spiral curve t ,y t It can be expressed as the following formula:

[0039]

[0040] Where t is the number of spiral rotations starting from the minimum radius, and s is the spiral rate of the logarithmic spiral curve.

[0041] like Figure 1 As shown, links AB and BC form the first bending element, links CD and DE form the second bending element, and so on. The angle between link AB and the line AO ​​connecting its point A on the logarithmic spiral curve to the origin is α. The angle between link CD and the line CO is α. The angle between the line CO connecting link BC's point C on the logarithmic spiral curve to the origin and the line AO ​​connecting link AB's point A on the logarithmic spiral curve to the origin is θ. The angle between link AB and link BC is γ.

[0042] To make the sequentially connected links scale down proportionally, let the length of link AB be a, the length of link BC be b, and the length of link CD be c. Find the included angle γ such that... β is the reduction ratio of the length of adjacent links.

[0043] The coordinates of point C can be obtained from the above conditions.

[0044]

[0045] Similarly, the coordinates of point E can be obtained.

[0046]

[0047] Using the coordinates of the points mentioned above, the expressions for lines AB, BC, and DE can be obtained:

[0048] y AB =k AB ·(x+R)=tanα·x+tanα·R

[0049]

[0050] Since BC can be obtained by dividing the distance from point C to line AB by the sine of the angle γ between the two lines, AB can be obtained by dividing the distance from point A to line BC by the sine of the angle γ between the two lines, and CD can be obtained by dividing the distance from point C to line DE by the sine of the angle γ between the two lines, we can obtain the expressions for a, b, and c:

[0051]

[0052]

[0053] Depend on We can obtain the following formula:

[0054]

[0055] Since the above equation contains a combination of exponential and trigonometric functions, it has no analytical closed-form solution. Numerical methods (such as vpasolve) must be used to obtain approximate values ​​for γ and β. Based on the calculated γ and β, the lengths of each link are determined.

[0056] Example 2

[0057] On the basis of Embodiment 1, an anti-four-bar linkage unit structure is introduced by designing overlapping bars. Specifically, the middle part of the first link of each bending unit has a first overlapping bar hinge hole position, and the middle part of the second link has a second overlapping bar hinge hole position. The two ends of an overlapping bar are respectively hinged to the first overlapping bar hinge hole position of this bending unit and the first overlapping bar hinge hole position of the next bending unit. The two ends of another overlapping bar are respectively hinged to the second overlapping bar hinge hole position of this bending unit and the second overlapping bar hinge hole position of the next bending unit. Each overlapping bar and the two links hinged to it, as well as the link that intersects but is not connected to it, form an anti-four-bar linkage unit. As Figure 1 shown, the first overlapping bar and links AB, BC, and CD form the first anti-four-bar linkage unit, and the second overlapping bar and links BC, CD, and DE form the second anti-four-bar linkage unit, and so on. In the first anti-four-bar linkage unit, the lengths of the two overlapping bar hinge hole positions on links AB and CD are m and n respectively.

[0058] After determining the lengths of links AB, BC, CD, etc. related to the spiral shape in the present invention, any two values m (m < a) and n (n < c) are given within the length range to determine the length of the middle overlapping bar and the hinge hole positions of the overlapping bar. In the present invention, each anti-four-bar linkage unit gradually shrinks according to a unified ratio. In the kth anti-four-bar linkage unit, the lengths of the two overlapping bar hinge hole positions on the corresponding links are correspondingly reduced, which are respectively and As Figure 1 shown.

[0059] Embodiment 3

[0060] This embodiment provides a hugging-type variable curvature gripper based on a logarithmic spiral curve. As Figure 2 shown, taking the grasping of a cylindrical object as an example, the hugging-type variable curvature gripper includes a driving rope 1 and a variable curvature grasping arm 2. The variable curvature grasping arm 2 is controlled by the driving rope 1, and the variable curvature grasping arm 2 is bent with variable curvature from the vertically extended state to perform a hugging-type grasping on the grasped object. As Figure 3 、 Figure 4 shown, the variable curvature bending effect of the variable curvature grasping arm 2 can hug and bind grasped objects of different sizes at the end of the gripper to achieve adaptive and stable grasping.

[0061] Specifically, the variable curvature grasping arm 2 is composed of a number of grasping components with similar shapes. Each grasping component includes a rigid frame and two rigid link units.

[0062]

[0063] ​The rigid linkage unit includes two connectors and two fixed narrow plates. The connectors are T-shaped with a through hole at the top and two threaded holes at the bottom. The fixed narrow plates are rectangular with two countersunk holes at each end. The two threaded holes on the connectors are connected to the countersunk holes on the fixed narrow plates by bolts. The rigid linkage unit has one symmetrically arranged connector at the top and bottom, which is connected to the left and right sides of the T-shape by the fixed narrow plates.

[0064] The rigid frame is a hollow square frame, symmetrical from left to right. In the center of the rigid frame are two through holes of the same size as the through holes on the connector head. Each side of the rigid frame has two square slots, the width of which is the same as the thickness of the rigid connecting rod unit, allowing the rigid connecting rod unit to pass through the square slots and be hinged to the through holes on the rigid frame via the through holes on the connector head. The lower end of the rigid frame has two symmetrical arc-shaped bosses, and the upper end has another arc-shaped boss. The distance between the two lower arc-shaped bosses is equal to the width of the upper arc-shaped boss. Above each boss is a through hole of the same size and position, allowing the rigid frame to be hinged to another rigid frame end-to-end via the through holes on the upper and lower arc-shaped bosses. In other words, all rigid frames are sequentially hinged together end-to-end.

[0065] In the variable curvature gripping arm, two rigid link units are connected through the square slots on the left and right sides of the rigid frame of the gripping assembly and hinged through through holes. The other end through holes of the two rigid link units will pass through the square slots on the left and right sides of the rigid frame of the next gripping assembly and be connected through through holes. The two rigid link units will pass through the square slots on the left and right sides of the rigid frame of the next gripping assembly, but will not be connected in any way. That is, the two rigid link units of each gripping assembly pass through the square slots of the rigid frame of the next gripping assembly and are hinged to the through holes in the middle of the rigid frame of the next gripping assembly.

[0066] The rigid frame has several circular threading holes on each of its upper and lower arc-shaped bosses. The drive rope passes through the threading hole starting from the first rigid frame, then through the threading holes on the same side of the rigid frame as the variable curvature gripping arm, and finally through the threading hole of the last rigid frame for fixation. The other side of the variable curvature gripping arm also passes through another drive rope. By pulling the drive ropes on both sides, the bending control of the variable curvature gripping arm is achieved.

[0067] In the variable curvature gripping arm, the length or shape parameters of the rigid frame and the rigid link unit in each gripping component are designed according to the design methods in Embodiments 1 and 2 to achieve the logarithmic spiral curve variable curvature bending of the variable curvature gripping arm. Specifically, the rigid frame is designed according to the design method of achieving logarithmic spiral curve bending based on the rigid structure linkage bending form in Embodiment 1. The link connected end to end in Embodiment 1 is the rigid frame that is hinged end to end in this embodiment, and the link length is the distance between the two hinged ends of the rigid frame. The rigid link unit is designed according to the stacked link design method in Embodiment 2. The stacked link hinge hole in Embodiment 2 is the through hole in the middle of the rigid frame in this embodiment.

[0068] exist Figure 5 In the example of the gripping component structure shown, the gripping component 21 consists of a rigid frame 211 and two rigid link units 212 and 213. The rigid frame 211 is hinged to the middle arc-shaped boss through the through holes on the two arc-shaped bosses on its upper end. The connection method of the remaining rigid frames is the same as described above. The lower through holes of the rigid link units 212 and 213 are hinged to the through hole in the upper middle part of the rigid frame 211. The rigid link unit 222 of the next gripping component passes through another square slot on the right side of the rigid frame 211 but is not connected. The upper through hole of the rigid link unit 232 of the next gripping component is hinged to the through hole in the lower middle part of the rigid frame 211. The connection method of the remaining rigid links is the same as described above.

[0069] exist Figure 6 In the rigid linkage unit structure example shown, the rigid linkage unit 212 consists of two connectors 2121 and 2122 and two fixed narrow plates 2123 and 2124. The two threaded holes on the connector 2121 are connected to the countersunk holes of the fixed narrow plates 2123 and 2124 by bolts.

[0070] The operation method of this embracing variable curvature gripper based on logarithmic spiral curves is as follows:

[0071] S1. In the initial state of the grasping task, the variable curvature grasping arm is in a vertically extended state, and the drive rope is in a slack state.

[0072] S2. Move the variable curvature gripper to the side of the object being gripped, pull the drive rope on the side of the object being gripped, so that the variable curvature gripper bends towards the object being gripped, and the drive rope changes from a slack state to a taut state.

[0073] S3. After the object being grasped is pushed by the variable curvature gripper, the drive rope is pulled further. With the help of the gradually increasing curvature of the variable curvature gripper arm, the front end curls up to embrace the object, gradually binding the object to a position with a suitable curvature, thus completing the embrace. The drive rope remains taut. The tension of the drive rope forms a gripping force closure at the contact point between the variable curvature gripper and the object being grasped, achieving a stable envelope gripping of the object being grasped.

[0074] S4. After the gripping is completed, release the drive rope on this side and pull the drive rope on the other side to make the variable curvature gripping arm extend vertically. This completes one workflow.

[0075] In addition, depending on actual needs, the drive rope of the grabbing variable curvature gripper can be pulled by a drive motor to control the rotation of the motor, thereby achieving a grabbing effect at a specified speed and acceleration.

[0076] Depending on actual needs, the connecting seat of the gripper with variable curvature can be fixed on the robotic arm, and the gripper works with the robotic arm to complete other complex grasping tasks.

[0077] Depending on actual needs, the variable curvature gripping arm can produce different variable curvature gripping effects according to different logarithmic spiral curves; the greater the pulling force and speed of the driving rope, the greater the gripping force and speed of the variable curvature gripping arm.

[0078] The above description is merely a preferred embodiment of the present invention. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A cradle-type variable curvature gripper based on a logarithmic spiral curve, characterized in that, It includes a drive rope and a variable curvature gripping arm; the variable curvature gripping arm is composed of several gripping components, each gripping component including a rigid frame and two rigid linkage units; the two ends of the rigid linkage units have through holes; The rigid frame is a hollow square frame that is symmetrical from left to right. It has two through holes in the center, the same size as the through holes on the rigid connecting rod unit, extending horizontally through each other. Each side of the rigid frame has two square slots, the width of which is the same as the thickness of the rigid connecting rod unit, allowing the rigid connecting rod unit to pass through the square slots and be hinged to the through holes on the rigid frame via the through holes on the rigid connecting rod unit. The lower end of the rigid frame has two symmetrical arc-shaped bosses, and the upper end has another arc-shaped boss. The distance between the two lower arc-shaped bosses is equal to the width of the upper arc-shaped boss. Above each boss is a through hole of the same size and position, allowing the rigid frame to be hinged to another rigid frame end-to-end via the through holes on the upper and lower arc-shaped bosses. The rigid frame of the gripping component has two rigid connecting rod units in the square slots on the left and right sides, and they are hinged through through holes. These two rigid connecting rod units pass through the square slots on the left and right sides of the rigid frame of the next gripping component, and are hinged to the square slots on the left and right sides of the rigid frame of the next gripping component through through holes. The rigid frame has several circular threading holes on the arc-shaped bosses at both ends. The drive rope passes through the threading hole starting from the first rigid frame, then passes through the threading holes on the same side of the rigid frame as the variable curvature gripping arm, and finally passes through the threading hole of the last rigid frame and is fixed. The other side of the variable curvature gripping arm also passes through another drive rope. By pulling the drive ropes on both sides, the bending control of the variable curvature gripping arm is achieved. The variable curvature gripping arm adopts a logarithmic spiral curve variable curvature bending design. Given any logarithmic spiral curve, each rigid frame is placed sequentially starting from the end of the logarithmic spiral curve. The starting position of the first rigid frame is at the end of the logarithmic spiral curve, and the end position is inside the logarithmic spiral curve but does not fall on the logarithmic spiral curve. The end of the second rigid frame is hinged to the end of the first rigid frame, and its end position falls on the logarithmic spiral curve. The remaining links are continuously placed in the above manner to form a series structure in which every two rigid frames form a bending unit.

2. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 1, characterized in that, In the variable curvature gripping arm, each rigid frame is considered as a link. The angle between the line connecting the second link of each bending unit to the origin on the logarithmic spiral curve and the line connecting the first link to the origin on the logarithmic spiral curve is a fixed angle, called the bending angle of the bending unit, denoted as θ. The angle between the first link of each bending unit and the line connecting its point to the origin on the logarithmic spiral curve is another fixed angle, denoted as α. By controlling the angle γ between the first and second links in each bending unit, the lengths of the two links can be changed. The lengths of all sequentially connected links are successively reduced by a specific ratio β. The length of all links is calculated and modeled to obtain the angle γ between the first and second links in each bending unit and the reduction ratio β, thereby calculating the point in each bending unit that falls inside the logarithmic spiral curve.

3. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 2, characterized in that, In the variable curvature gripping arm, two rigid linkage units are considered as stacked rods, and an inverse four-bar linkage structure is introduced through the design of stacked rods. Each bending unit has a first stacked rod hinge hole in the middle of its first linkage, and a second stacked rod hinge hole in the middle of its second linkage. The first stacked rod hinge hole of this bending unit and the first stacked rod hinge hole of the next bending unit respectively hinge to the two ends of a stacked rod. The second stacked rod hinge hole of this bending unit and the second stacked rod hinge hole of the next bending unit respectively hinge to the two ends of another stacked rod. Each stacked rod is connected to... The two connecting rods hinged to it, and the connecting rods intersecting but not connected to it, constitute a reverse four-bar linkage unit. In the first reverse four-bar linkage unit, the lengths of the two stacked rod hinge holes on the corresponding connecting rods are m and n, respectively. After determining the length of the connecting rods related to the helical shape, two arbitrary values ​​m and n are given within the length range to determine the length of the intermediate stacked rods and the hinge hole positions of the stacked rods. Each reverse four-bar linkage unit gradually shrinks according to a uniform ratio. In the k-th reverse four-bar linkage unit, the lengths of the two stacked rod hinge holes on the corresponding connecting rods are correspondingly reduced to m and n, respectively. and 4. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 1, characterized in that, The rigid linkage unit includes two connectors and two fixed narrow plates. The connectors are T-shaped with a through hole at the top and two threaded holes at the bottom. The fixed narrow plates are rectangular with two countersunk holes at each end. The two threaded holes on the connectors are connected to the countersunk holes on the fixed narrow plates by bolts. The rigid linkage unit has one symmetrically arranged connector at the top and bottom, which is connected to the left and right sides of the T-shape by the fixed narrow plates.

5. A method for operating a clasping variable curvature gripper based on a logarithmic spiral curve as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. In the initial state of the grasping task, the variable curvature grasping arm is in a vertically extended state, and the drive rope is in a slack state. S2. Move the variable curvature gripper to the side of the object being gripped, pull the drive rope on the side of the object being gripped, so that the variable curvature gripper bends towards the object being gripped, and the drive rope changes from a slack state to a taut state. S3. After the object being grasped is pushed by the variable curvature gripper, the drive rope is pulled further. With the help of the gradually increasing curvature of the variable curvature gripper arm, the front end curls up to embrace the object, gradually binding the object to a position with a suitable curvature, thus completing the embrace. The drive rope remains taut. The tension of the drive rope forms a gripping force closure at the contact point between the variable curvature gripper and the object being grasped, achieving a stable envelope gripping of the object being grasped. S4. After the gripping is completed, release the drive rope on this side and pull the drive rope on the other side to make the variable curvature gripping arm extend vertically. This completes one workflow.

6. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 1, characterized in that, The drive rope of the embracing variable curvature gripper can be pulled by a drive motor, controlling the motor rotation to achieve a gripping effect at a specified speed and acceleration.

7. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 1, characterized in that, The gripper with variable curvature is fixed to the robotic arm via a connecting seat, and the gripper works with the robotic arm to complete complex grasping tasks.

8. The embracing variable curvature gripper based on a logarithmic spiral curve according to claim 1, characterized in that, The variable curvature gripping arm produces different variable curvature gripping effects according to different logarithmic spiral curves; the greater the pulling force and speed of the drive rope, the greater the gripping force and speed of the variable curvature gripping arm.

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