A serpentine arm structure based on negative Poisson's ratio metamaterial

Abstract

The present invention discloses a serpentine arm structure based on a negative Poisson's ratio metamaterial. The serpentine robotic arm is assembled from a plurality of mechanical metamaterial structures. The mechanical metamaterial structure is composed of an elastically deformable external frame unit and bionic scales. The elastically deformable external frame unit is formed by four connecting rods arranged between a vertical rod A and a vertical rod B placed in parallel. The elastically deformable external frame unit has the elastic deformation characteristics of a flexible mechanism. The mechanical metamaterial structure is divided into a first plane and a second plane from the spatial structure. The second plane is tilted upward at a certain angle α relative to the first plane. The α forms a micro-convex bionic scale structure with a certain backward angle, presenting a highly asymmetric ratchet characteristic with one side sharp and the other side flat. This causes the mechanical metamaterial structure to form friction anisotropy in the scale edge direction, that is, it exhibits different friction forces in different movement directions.

Description

Technical Field

[0001] The present invention relates to a snake-arm robot for pipeline operations, and more particularly to a snake-arm structure based on a negative Poisson's ratio metamaterial. Background Art

[0002] With the rise of robotics, and particularly the active development of biomimetic robots, the study of snake locomotion and the development of robotic snakes have become hot topics in the biomimetic field. Snake-like robots hold broad application prospects in fields requiring high reliability, such as battlefield mine clearance, blasting, exploration and rescue in mines and ruins, pipeline repair, and exoplanetary surface exploration, all under harsh conditions. The concept of a snake-arm robot, first proposed by Buckingham, primarily refers to a narrow, self-supporting, super-redundant robotic arm. Its ability to avoid obstacles in confined spaces and adapt to extreme environments has attracted the attention of researchers from all walks of life, leading to the emergence of a variety of different configurations. Research in structural design, kinematics, motion planning, dynamics, and control has steadily deepened. Based on the technical approach of configuration design, snake-arm robots can be divided into two categories: articulated super-redundant snake arms and variable-geometry truss snake arms. Due to their structural characteristics, snake-arm robots can freely navigate rough, rugged, steep, narrow, and complex spaces without causing significant damage to the environment. They can also retract along their entry path without disturbing the environment, enabling them to enter places inaccessible to humans and perform tasks in their place.

[0003] Mechanical metamaterials are artificial materials whose geometric structures employ specialized functional units to achieve extraordinary properties. Negative Poisson's ratio mechanical metamaterials are a typical example of mechanical metamaterials. Under uniaxial tension, these materials expand perpendicular to the load direction, improving their lateral and vertical load-bearing capacity. Compared to traditional materials, negative Poisson's ratio metamaterials offer advantages in shear performance, energy absorption, fracture toughness, and indentation resistance, offering promising applications in energy absorption and shock absorption.

[0004] As an innovative mechanical design concept, the core of flexible mechanisms is to utilize the elastic deformation properties of materials to achieve the transmission and conversion of motion, force, or energy. This type of mechanism is fundamentally different from traditional rigid structures. It does not rely on hard connections and contact, but instead completes the transmission of force and motion conversion through the elastic deformation of the components themselves. In traditional rigid structures, the transmission of motion is often accompanied by friction, wear, and transmission clearance. These problems not only limit mechanical efficiency but also increase maintenance costs. In contrast, flexible mechanisms, due to their frictionless and wear-free characteristics, can effectively reduce energy loss and improve transmission efficiency. In addition, since there is no hard contact, the transmission clearance is almost negligible, making the movement of the mechanism more precise and reliable.

[0005] Sharks, known for their "shark skin effect," have developed biomimetic scales that, through continuous adaptation, self-learning, and self-organization, possess a non-smooth grooved drag-reducing surface capable of rationally regulating the external fluid medium. Shark skin-like drag-reducing skins, fabricated through processes such as hot embossing, micro-molding, and micro-electroforming, can effectively reduce surface friction on ships, underwater vehicles, and other structures. Micro-embossing molding is a low-cost and rapid method for simultaneous micro- and nano-replication of structural patterns at the micro- and nanoscale. The principle is to cast a prepolymer in a low-viscosity, high-fluidity liquid onto a template surface. Then, by applying a certain pressure, the prepolymer fills the concave areas of the template, achieving the replication and transfer of the structural pattern. Summary of the Invention

[0006] In order to improve the ability of the serpentine arm robot to pass through and anchor in pipes or other narrow spaces, the present invention designs a serpentine robotic arm structure based on negative Poisson's ratio metamaterial suitable for the serpentine arm robot. A support frame of the mechanical metamaterial structure is designed based on the design method of the flexible mechanism. While maintaining the integrity of the elastically deformable external frame unit structure, it is given negative Poisson's ratio characteristics after being arranged in a spatial array, and provides a new solution for the axial controllable drive of the serpentine arm. At the same time, the structure of the snake scales in nature is biomimetic designed, and bionic scales are added to the elastically deformable external frame units in the form of elastic skin or flexible fins. Thanks to the elastic deformation and scale design of the external frame unit, the bionic scales form friction anisotropy in the direction along the scale edge and the reverse scale edge direction, which greatly enhances the ability of the serpentine arm to pass through and anchor in complex and narrow spaces such as pipes, and expands its applicable operating range and functions.

[0007] The present invention designs a serpentine arm structure based on a negative Poisson's ratio metamaterial. The serpentine arm structure is a mechanical arm of a serpentine arm robot and is a variable geometry truss serpentine arm. The serpentine arm is obtained by arranging a plurality of mechanical metamaterial structures.

[0008] The mechanical metamaterial structure is composed of elastically deformable external frame units and bionic scales;

[0009] The elastically deformable external frame unit is provided with four connecting rods between the A vertical rod (1) and the B vertical rod (2); wherein:

[0010] The upper end of the A vertical rod (1) is connected to one end of the A connecting rod (3), the other end of the A connecting rod (3) is connected to one end of the B connecting rod (4), and the other end of the B connecting rod (4) is connected to the upper end of the B vertical rod (2);

[0011] The lower end of the A vertical rod (1) is connected to one end of the C connecting rod (5), the other end of the C connecting rod (5) is connected to one end of the D connecting rod (6), and the other end of the D connecting rod (6) is connected to the lower end of the B vertical rod (2);

[0012] The junction between the A vertical rod (1), the B vertical rod (2) and the four connecting rods is the forming processing conversion point;

[0013] The A vertical rod (1), the C connecting rod (5), the D connecting rod (6) and the B vertical rod (2) are in the same plane, which is called the first plane, and the A vertical rod (1) is parallel to the B vertical rod (2);

[0014] The A link (3) and the B link (4) are in the same plane, which is called the second plane;

[0015] The angle between the first plane and the second plane is denoted as α, and α=1° to 45°;

[0016] The angle α between the lower end of the A vertical rod (1) and one end of the C connecting rod (5) 下 The angle β between the other end of the C link (5) and one end of the D link (6) is equal to one half 下 ,Right now

[0017] The angle δ between the other end of the A link (3) and one end of the B link (4) is equal to β 下 , that is, δ=β 下 ;

[0018] The relationship between the length H of the A vertical rod (1) and the length L of the C connecting rod (5) is L=0.3H~1.5H.

[0019] The serpentine arm structure based on negative Poisson's ratio metamaterial designed by the present invention has the following technical effects:

[0020] ① Bionic Design: The snake-arm robot utilizes a biomimetic design inspired by the structure of snake scales found in nature. This design not only gives the robot a unique appearance but also introduces a series of functional innovations. By mimicking the structure and function of organisms, the advantages of organisms are applied to engineering design, aiming to improve the performance of engineering systems.

[0021] ② Unique metamaterial structure: This metamaterial structure consists of an elastically deformable external frame and biomimetic scales. This design allows the elastically deformable external frame units to deform when subjected to external forces while maintaining structural integrity and functionality. The elastically deformable external frame units provide the basic shape and support of the mechanical metamaterial structure, while the biomimetic scales cover the external frame, providing a certain degree of deformation and coverage.

[0022] ③Negative Poisson’s ratio characteristics: The negative Poisson’s ratio characteristic means that when subjected to pressure, it will shrink and deform perpendicular to the direction of pressure, forming a “tension-expansion-compression” characteristic. At the same time, negative Poisson’s ratio materials have advantages over traditional materials in terms of shear bearing capacity, fracture resistance, energy absorption and indentation resistance. This characteristic significantly enhances the passability of the serpentine arm in narrow spaces, and its axial deformability can be used as an axial feed freedom. At the same time, its radial radius will become thicker when it extends forward (feeds), which also helps to improve the serpentine arm’s ability to grip the pipe wall when moving in the pipe. In addition, the tubular structure with a negative Poisson’s ratio can remain in a compact storage state when contracted, and produce larger deformations in all directions when unfolded. This has significant advantages for scenarios that require transportation through narrow spaces and require more comprehensive support forces (such as earthquake rescue, pipeline repair, vascular stents, etc.).

[0023] ④ Friction anisotropy: The second plane in the mechanical metamaterial structure forms a specific angle with the first plane, producing highly asymmetric detent properties, resulting in different friction forces in different directions of motion. This property, combined with the negative Poisson's ratio, further enhances the serpentine arm's ability to grip the pipe wall in specific directions during expansion and tightening, especially in pipes with a certain degree of flexible deformation. This facilitates the serpentine arm's ability to anchor at any position in the pipe, greatly enhancing its ability to pass through confined spaces.

[0024] ⑤ Axial controllable deformation characteristics: Traditional serpentine arms require a separate propulsion device in this direction to achieve axial feeding and retraction. However, the serpentine arm of the present invention can be used as an axial feeding degree of freedom due to the axial deformability of the metamaterial. Compared with traditional serpentine arms, the number of drivers can be reduced. At the same time, the radial radius will become thicker when extending forward (feeding), which helps to improve the serpentine arm's ability to grasp the pipe wall when moving in the pipe. Combined with anchoring and axial deformation at any position on the pipe wall in the pipe, the serpentine arm can achieve the effect of creeping forward in the pipe, which further expands the movement mode and application range of the serpentine arm.

[0025] ⑥ Broad Application Prospects: The serpentine arm, based on the properties of this metamaterial, has a wide range of applications, including pipeline operation serpentine arm robots that can anchor at any location within a pipeline; emergency structural repair / disaster relief robots that can navigate narrow passages and provide overall support at specific locations; and serpentine arm robots with excellent grasping capabilities. Their peristaltic propulsion capabilities can be used to develop vascular stent robots that can autonomously navigate within blood vessels. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram of the external structure of the serpentine arm based on the negative Poisson's ratio metamaterial structure of the present invention.

[0027] Figure 2 It is a structural diagram of a single mechanical metamaterial structure with a skin according to the present invention.

[0028] Figure 3 It is a structural diagram of a single mechanical metamaterial structure with bionic scales of the present invention.

[0029] Figure 4 It is a structural diagram of a single elastically deformable external frame unit of the present invention.

[0030] Figure 4A It is a right side view of a single elastically deformable outer frame unit of the present invention.

[0031] Figure 5 These are multiple facet projection views of the mechanical metamaterial structure and the elastically deformable external frame unit of the present invention; with (a) as a reference, (b) is a 30-degree downward projection of (a), (c) is a 90-degree left projection of (a), (d) is a 60-degree downward projection of (a) 90 degrees to the left, (e) is a 90-degree left projection of the elastically deformable external frame unit based on (a), (f) is a 60-degree downward projection of the 90-degree left projection of the elastically deformable external frame unit based on (a), (g) is a 180-degree left projection of (a), (h) is a 60-degree downward projection of the 180-degree left projection of (a), (i) is a 180-degree left projection of the elastically deformable external frame unit based on (a), and (j) is a 60-degree downward projection of the 180-degree left projection of the elastically deformable external frame unit based on (a).

[0032] Figure 6 This is a working diagram of the pipeline operation snake-arm robot.

[0033] Figure 7 It is a schematic diagram of the negative Poisson's ratio deformation of the serpentine arms obtained by curling the spatial array of the mechanical metamaterial structure of the present invention.

[0034] Figure 7A It is a schematic diagram of the motion state of the serpentine arm pipeline operation.

[0035] Figure 8 It is a schematic diagram of the zero Poisson's ratio deformation obtained by a single-row array of the mechanical metamaterial structure of the present invention.

[0036] Figure 9 It is a schematic diagram of the negative Poisson's ratio deformation obtained by the spatial array of the mechanical metamaterial structure of the present invention.

[0037] Figure 10 This is a friction anisotropy analysis diagram of the mechanical metamaterial structure of the present invention.

[0038] Figure 11 This is a test analysis diagram of the friction anisotropy of the serpentine arm based on the negative Poisson's ratio metamaterial structure of the present invention.

[0039] 1.A vertical bar 2.B vertical bar 3. Connecting rod A 4.B connecting rod 5.C connecting rod 6.D connecting rod 10. Group A bionic scales 20. Group B bionic scales 30. Group C bionic scales 40. Group D Bionic Scales 50. Group E Bionic Scales 60. Group F bionic scales 100.A Skin 200.B Skin 300.C Skin 400.D skin 500.E Skin 600.F Skin DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the accompanying drawings. The parameters listed are merely exemplary embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

[0041] Snake-like arm structure based on negative Poisson's ratio metamaterial

[0042] The mechanical arm (also called snake arm) in the snake-arm robot is composed of multiple mechanical metamaterial structures (such as Figure 2 、 Figure 3 As shown) assembled, as Figure 1 As shown, the dotted box in the figure is a mechanical metamaterial structure.

[0043] Mechanical metamaterial structure composed of bionic scales composed of drag-reducing skin

[0044] See also Figure 1 、 Figure 2 As shown, the mechanical metamaterial structure includes an elastically deformable external frame unit (such as Figure 4 shown) and bionic scales composed of drag-reducing skin ( Figure 2 The skin is provided on the elastically deformable external frame unit and conforms to the elastically deformable external frame unit.

[0045] A skin 100 is provided between the A vertical rod 1 and the A connecting rod 3;

[0046] A B skin 200 is provided between the A connecting rod 3 and the B connecting rod 4;

[0047] A C skin 300 is provided between the B connecting rod 4 and the B vertical rod 2;

[0048] A D skin 400 is provided between the B vertical rod 2 and the F connecting rod 6;

[0049] An E skin 500 is provided between the F link 6 and the E link 5;

[0050] An F skin 600 is provided between the E connecting rod 5 and the A vertical rod 1 .

[0051] Mechanical metamaterial structure composed of fins forming bionic scales

[0052] See also Figure 1 、 Figure 3 As shown, the mechanical metamaterial structure includes an elastically deformable external frame unit (such as Figure 4 ) and bionic scales composed of fins (as shown Figure 3 The bionic scales are arranged on the elastically deformable external frame unit and conform to the configuration of the elastically deformable external frame unit.

[0053] A group of fins 10 is provided between the A vertical rod 1 and the A connecting rod 3;

[0054] A group B of fins 20 is provided between the A connecting rod 3 and the B connecting rod 4;

[0055] A group C of fins 30 is provided between the B connecting rod 4 and the B vertical rod 2;

[0056] A group D of fins 40 is provided between the B vertical rod 2 and the F connecting rod 6;

[0057] A group E of fins 50 is provided between the F link 6 and the E link 5;

[0058] A group F of fins 60 is provided between the E connecting rod 5 and the A vertical rod 1 .

[0059] Elastically deformable external frame unit

[0060] See also Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 As shown, the elastically deformable external frame unit designed in the present invention is provided with four connecting rods between the vertical rod A 1 and the vertical rod B 2; wherein:

[0061] The upper end of the A vertical rod 1 is connected to one end of the A connecting rod 3, the other end of the A connecting rod 3 is connected to one end of the B connecting rod 4, and the other end of the B connecting rod 4 is connected to the upper end of the B vertical rod 2;

[0062] The lower end of the A vertical rod 1 is connected to one end of the C connecting rod 5, the other end of the C connecting rod 5 is connected to one end of the D connecting rod 6, and the other end of the D connecting rod 6 is connected to the lower end of the B vertical rod 2;

[0063] The structures of the vertical rod A 1 and the vertical rod B 2 are the same, and the structures of the link A 3, the link B 4, the link C 5 and the link D 6 are the same.

[0064] The joints between the vertical rod A 1, the vertical rod B 2 and the four links ( Figure 4 the dotted circles in) are the forming and processing conversion points. Figure 4 The display of the processing conversion points in as a triangle with chamfers is for the convenience of the three-dimensional software configuration schematic, and does not limit the present invention.

[0065] See Figure 4B As shown, the vertical rod A 1, the link C 5, the link D 6 and the vertical rod B 2 are in the same plane, which is called the first plane, and the vertical rod A 1 and the vertical rod B 2 are parallel.

[0066] See Figure 4B As shown, the link A 3 and the link B 4 are in the same plane, which is called the second plane.

[0067] The mechanical metamaterial structure is divided into a first plane and a second plane from the spatial structure. The second plane is tilted upward at a certain angle (i.e., α) relative to the first plane. This α forms a micro-convex bionic scale structure with a certain backward angle, presenting a highly asymmetric pawl characteristic with one side sharp and the other side gentle. This results in friction anisotropy formed by the mechanical metamaterial structure in the upward direction of the scale edge, that is, different frictional forces are shown in different movement directions.

[0068] In Figure 4 , the included angle at the joint between the lower end of the vertical rod A 1 of the elastically deformable outer frame unit and one end of the link C 5 is denoted as α 下 ; the included angles formed by the parallelly placed vertical rod A 1 and the vertical rod B 2 are the same, that is, the included angle at the joint between the lower end of the vertical rod B 2 and one end of the link D 6 is also α 下 . The included angle at the joint between the other end of the link C 5 and one end of the link D 6 is denoted as β 下 , and β 下 = 5° to 150°.

[0069] In Figure 4 , the included angle at the joint between the other end of the link A 3 and one end of the link B 4 of the elastically deformable outer frame unit is denoted as δ, and δ = β 下 .

[0070] In Figure 4A , Figure 4B , the included angle between the first plane and the second plane is denoted as α, and α = 1° to 45°. It looks like the Chinese character "Bu" (radish) from the projection view.

[0071] In Figure 4Among them, the size of the elastically deformable outer frame unit is such that the length of the A vertical rod 1 is denoted as H, the length of the C connecting rod 5 is denoted as L, and L = 0.3H to 1.5H. The vertical rod and the connecting rod have the same diameter, which is 0.5 mm to 30 mm.

[0072] In the present invention, the configuration of the elastically deformable outer frame unit can be microfabricated by 3D printing technology. The configuration of the elastically deformable outer frame unit can also be fabricated by bending an elastic wire in a mold. The elastic wire is made of a wire material with a diameter of 0.5 mm to 30 mm made of a metal or a polymer material. The metal can be stainless steel, aluminum alloy, nickel-based alloy, etc., or a nickel-based shape memory alloy.

[0073] In Figure 5 Among the multiple surface projections of the shown mechanical metamaterial structure body (or the elastically deformable outer frame unit), the front view of the elastically deformable outer frame unit is triangular. The rear view is the same as the front view, so the rear view is omitted. The right view of the elastically deformable outer frame unit is in the shape of the Chinese character "bu" of a radish.

[0074] The elastically deformable outer frame unit designed in the present invention can deform when subjected to an external force, while maintaining the integrity and functionality of the structure.

[0075] Pipe operation snake-arm robot

[0076] Figure 6 The shown pipe operation snake-arm robot is assembled using multiple mechanical metamaterial structure bodies, as Figure 7 shown. The mechanical metamaterial structure body (such as Figure 2 , Figure 3 shown) can obtain a pipe operation snake-arm robot that can be anchored at any position in the pipe as Figure 6 shown after configuration, and this snake-arm robot also has excellent grasping ability.

[0077] Roll the mechanical metamaterial structure body (such as Figure 2 , Figure 3 shown) into a reel-like structure according to a spatial array as the main body of the snake arm, as Figure 7 shown, Figure 7 (b) is the top view of Figure 7 (a). This design not only gives the snake arm a unique appearance, but also brings a series of functional innovations. The snake arm simultaneously has two characteristics of frictional anisotropy and negative Poisson's ratio, and the combination of these two characteristics greatly expands the application range and efficiency of the snake arm.

[0078] The mechanical metamaterial structure with a negative Poisson's ratio can significantly enhance the passability of the serpentine arm in narrow spaces. Its axial deformability can be utilized as an axial feed freedom. At the same time, its radial radius will become thicker when extending forward (feeding), which helps to improve the serpentine arm's ability to grasp the pipe wall when moving in the pipe.

[0079] At the same time, the friction anisotropy along the axial direction of the reel serpentine arm can significantly enhance the gripping ability of the serpentine arm. In the pipeline environment, combined with the negative Poisson's ratio characteristics, it further enhances the gripping ability of the pipe wall during expansion.

[0080] See also Figure 7A As shown, combining the two characteristics of negative Poisson's ratio and friction anisotropy, for pipeline environment ( Figure 7A -a) can realize axial feed motion by utilizing axial elastic deformation ( Figure 7A -b), using the negative Poisson's ratio to achieve radial controllable deformation and friction anisotropy while expanding and contracting in the axial direction, i.e., the release and locking of the ratchet pawl ( Figure 7A -c) The serpentine arm can partially grip the pipe wall while feeding. This allows the serpentine arm to be anchored at any position in the pipe, greatly enhancing its ability to navigate confined spaces. Furthermore, by controlling the serpentine arm's local axial expansion and contraction (accompanied by radial expansion and compression) at a specific rhythm, it can achieve a worm-like peristaltic motion along the pipe wall.

[0081] Array arrangement

[0082] See also Figure 8 As shown, the mechanical metamaterial structure is linearly arrayed in a first plane perpendicular to the scale edge direction to form a single row array, which is perpendicular to the scale edge direction (such as Figure 3 When the force is greater than 0.05, the theoretical deformation has the characteristic of zero Poisson's ratio, that is, the size in the direction of the scale edge does not change when it is stretched or compressed in the direction perpendicular to the scale edge.

[0083] like Figure 9 As shown, a single-row array of mechanical metamaterial structures is repeatedly arrayed in space, and the first plane of each single-row array is used as the second plane of the next single-row array. While ensuring that the spatial array always has a ratchet-scale blade structure, it also has a negative Poisson's ratio characteristic, that is, when subjected to pressure, it will shrink and deform perpendicular to the pressure direction, forming a tensile expansion and compression characteristic.

[0084] Friction anisotropy

[0085] See also Figure 10As shown in the figure, when the bionic scale surface of the mechanical metamaterial structure contacts a rough friction surface, the microscopically uneven surface of the contacted surface forms irregular ratchets, and the scale structure forms pawls when it moves relative to the rough friction surface, forming release and locking states of the ratchet pawls in the direction along the scale edge and in the direction against the scale edge, respectively, thereby forming different friction characteristics in the direction along the scale edge and in the direction against the scale edge, that is, exhibiting friction anisotropy.

[0086] Example 1: Snake-like arms of negative Poisson's ratio metamaterials for pipeline operation

[0087] See also Figure 11 As shown, the preferred dimensions of a single mechanical metamaterial structure are: the vertical rod and connecting rod are 304 capillary stainless steel tubes with a diameter of 0.7 mm; the lengths of the vertical rods A 1 and B 2 are H = 15 mm, the length of the connecting rod is L = 12 mm, the angles α and δ between the first plane and the second plane are 25° and 12°, respectively. 下 =60°,α 下 =30°; the bionic scales on the elastically deformable external frame unit are composite drag-reducing skins. The elastically deformable external frame unit is made by bending 304 capillary stainless steel tubes.

[0088] A single row is an array of 6 mechanical metamaterial structures, which are rolled into a roll-like structure according to the spatial 2-row array (2×6).

[0089]

[0090] Measurements were conducted on an ALJ-50 tensile tester (Fuzhou Aipu Instrument Co., Ltd.). Under identical test conditions (pipe material, diameter, and measurement method), the metamaterial serpentine arm was connected to a dynamometer and fixed relative to the test bench. The pipe and serpentine arm were pulled to produce relative motion, and the dynamometer reading during this relative motion was recorded as the frictional resistance between the serpentine arm and the pipe. The test results show a significant difference in frictional resistance along the scales and against the scales, with the frictional resistance in the against-scale direction having a multiplier effect compared to that in the along-scale direction.

[0091] Fabrication of composite drag-reducing skin by micro-plastic casting and embossing

[0092] (A) A condensation-type two-component (A, B two-component) room temperature vulcanized silicone rubber RTV-2 875 is used as the material for preparing the composite drag-reducing skin, wherein component A includes base rubber, filler, crosslinking agent, etc., and component B is a catalyst. Since the mass ratio of components A and B determines the curing time of the silicone rubber, the mass ratio of components A and B should be increased as much as possible while ensuring that the silicone rubber can be cured, and the curing time should be extended to facilitate the discharge of bubbles;

[0093] (B) Weigh a certain amount of silicone rubber so that the mass ratio of components A to B is 100:2. Stir well and pre-degassed in a vacuum drying oven to remove any air introduced during stirring. Maintain a vacuum degree of <0.1 bar for approximately 2 minutes.

[0094] (C) After pre-degassing, the silicone rubber obtained in the previous step was poured onto the front surface of Template A to the desired thickness. After curing for 5 minutes, Template B and a 0.4 kg weight plate were placed on top. Vacuum degassing was performed again for 5 minutes to expel any trapped air between the contact surfaces.

[0095] (D) The micro-plastic casting imprint template in the previous step is completely cured at room temperature and demolded to obtain a silicone rubber composite drag reduction skin.

Claims

1. A serpentine arm structure based on a negative Poisson's ratio metamaterial, characterized by: The snake-like robotic arm is formed by arranging multiple mechanical metamaterial structures; The mechanical metamaterial structure is composed of elastically deformable external frame units and bionic scales; The elastically deformable external frame unit is provided with four connecting rods between the A vertical rod (1) and the B vertical rod (2); wherein: The upper end of the A vertical rod (1) is connected to one end of the A connecting rod (3), the other end of the A connecting rod (3) is connected to one end of the B connecting rod (4), and the other end of the B connecting rod (4) is connected to the upper end of the B vertical rod (2); The lower end of the A vertical rod (1) is connected to one end of the C connecting rod (5), the other end of the C connecting rod (5) is connected to one end of the D connecting rod (6), and the other end of the D connecting rod (6) is connected to the lower end of the B vertical rod (2); The junction between the A vertical rod (1), the B vertical rod (2) and the four connecting rods is the forming processing conversion point; The A vertical rod (1), the C connecting rod (5), the D connecting rod (6) and the B vertical rod (2) are in the same plane, referred to as the first plane, and the A vertical rod (1) is parallel to the B vertical rod (2); The A link (3) and the B link (4) are in the same plane, which is called the second plane; The angle between the first plane and the second plane is ,and ; The angle between the lower end of the A vertical rod (1) and one end of the C connecting rod (5) Equal to half the angle between the other end of the C link (5) and one end of the D link (6) ,Right now ; The angle between the other end of the A connecting rod (3) and one end of the B connecting rod (4) equal ,Right now ; A. Length of vertical rod (1) The length of the C connecting rod (5) relation, .

2. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The mechanical metamaterial structure is rolled into a scroll-shaped structure according to a spatial array as a serpentine arm.

3. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: A single row array of mechanical metamaterial structures is repeatedly arrayed in space.

4. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The bionic scales are composite drag-reducing skins.

5. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The bionic scales are fins.

6. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The configuration of the elastically deformable external frame unit is micro-fabricated using 3D printing technology.

7. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The configuration of the elastically deformable external frame unit is manufactured by bending elastic wire in a mold.

8. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 7, characterized in that: The elastic wire is made of metal or polymer material with a diameter of 0.5mm to 30mm; the metal is stainless steel, aluminum alloy or nickel-based alloy.

9. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 8, characterized in that: The elastic wire is made of nickel-based shape memory alloy.

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