Snakelike arm structure based on negative Poisson's ratio metamaterial

Abstract

The invention discloses a snakelike arm structure based on a negative Poisson's ratio metamaterial. A snakelike mechanical arm is obtained by assembling a plurality of mechanical metamaterial structural bodies. The mechanical metamaterial structural body is composed of an external frame unit capable of elastically deforming and bionic scales; the elastically-deformable outer frame unit is formed by arranging four connecting rods between a vertical rod A and a vertical rod B which are arranged in parallel. The elastically deformable outer frame unit has an elastic deformation characteristic of the flexible mechanism. The mechanical metamaterial structural body is divided into a first plane and a second plane from the space structure, the second plane tilts upwards by a certain angle alpha relative to the first plane, the alpha forms a micro-convex bionic scale structure with a certain backward angle, the highly asymmetric pawl characteristic with one sharp side and the other gentle side is shown, and the mechanical metamaterial structural body is formed. Therefore, the mechanical metamaterial structural body forms friction anisotropy in the scale blade direction, namely, different friction forces are shown in different movement directions.

Description

Technical Field

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

[0002] With the rise of robotics, especially the activeness of bionic robots, the study of snake movement and the development of robot snakes have become the research hotspots in the field of bionics. Snake robots have broad application prospects in fields with harsh conditions and high reliability, such as mine sweeping, blasting, detection and rescue in mines and ruins, pipeline maintenance, and surface exploration of outer planets. The concept of snake arm robot was first proposed by Buckingham. It mainly refers to a narrow, self-supporting, super-redundant robotic arm. It has the ability to avoid obstacles in confined spaces and adapt to extreme environments, which has attracted the attention of researchers from all walks of life. A variety of different configurations have emerged, and research on structural design, kinematics, motion planning, dynamics and control has gradually deepened. From the perspective of the technical route 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 its own structural characteristics, snake arm robots can freely shuttle in rough, rugged, steep, narrow and complex spaces, and are not easy to cause great damage to the environment. They can also retract along their entry path without disturbing the environment, thereby entering places that humans cannot reach to replace human work.

[0003] Mechanical metamaterials refer to artificial materials that have special functional structural units based on geometric structures to achieve extraordinary properties. Negative Poisson's ratio mechanical metamaterials are a typical type of mechanical metamaterial. Under the action of uniaxial tension, this type of negative Poisson's ratio metamaterial expands in the direction perpendicular to the load. This type of negative Poisson's ratio metamaterial can improve the lateral and vertical bearing capacity of the material. Compared with traditional materials, negative Poisson's ratio metamaterials have more advantages than traditional materials in shear performance, energy absorption performance, fracture toughness and indentation resistance. Therefore, this material has a good application prospect in the direction of energy absorption and shock reduction.

[0004] As an innovative mechanical design concept, the core of flexible mechanism is to use the elastic deformation characteristics of materials to realize the transmission and conversion of motion, force or energy. This mechanism is fundamentally different from the traditional rigid structure. It does not rely on hard connection and contact, but completes the transmission of force and the conversion of motion 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 the mechanical efficiency, but also increase the maintenance cost. In contrast, the flexible mechanism can effectively reduce energy loss and improve transmission efficiency due to its friction-free and wear-free characteristics. In addition, since there is no hard contact, the transmission clearance can be almost ignored, making the movement of the mechanism more precise and reliable.

[0005] Bionic scales Sharks, known for their "shark skin effect", have a non-smooth grooved drag-reducing surface that can reasonably regulate the external fluid medium through continuous adaptation, self-learning and self-organization. The shark skin-like drag-reducing skin made by hot embossing, micro-plastic casting, micro-electroforming and other processes can effectively reduce the surface friction of ships, underwater vehicles, etc. Micro-embossing plastic casting is a low-cost and fast method for simultaneously micro-replicating and nano-replicating structural patterns at the micro-nano scale. The principle is to cast the prepolymer on the template surface in a liquid state with low viscosity and high fluidity, and then fill the prepolymer into the concave area on the template by applying a certain pressure, thereby realizing the replication and transfer of the structural pattern. Summary of the invention

[0006] In order to improve the passing and anchoring ability of the serpentine arm robot in pipelines or other narrow spaces, the present invention designs a serpentine mechanical arm structure based on negative Poisson's ratio metamaterial suitable for the serpentine arm robot. The 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 a negative Poisson's ratio characteristic 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 bionic designed, and bionic scales are added to the elastically deformable external frame units in the form of elastic skins 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 passing and anchoring ability of the serpentine arm in complex and narrow spaces such as pipelines, 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, wherein the serpentine arm structure is a mechanical arm of a serpentine arm robot, and belongs to a variable geometry truss serpentine arm; the serpentine mechanical arm is obtained by arranging and configuring 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 joints between the A vertical rod (1), the B vertical rod (2) and the four connecting rods are forming processing conversion points;

[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, referred to as 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) is 下 The angle β between the other end of the C connecting rod (5) and one end of the D connecting rod (6) is equal to one half 下 ,Right now

[0017] The angle δ between the other end of the A connecting rod (3) and one end of the B connecting rod (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 adopts a bionic design based on the structure of snake scales in nature. This design not only gives the robot a unique appearance, but also brings a series of functional innovations. By imitating 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: The metamaterial structure consists of an elastically deformable external frame and bionic scales. This design enables the elastically deformable external frame unit to deform when subjected to external forces while maintaining the integrity and functionality of the structure. The elastically deformable external frame unit provides the basic shape and support of the mechanical metamaterial structure, while the bionic scales cover the external frame, providing a certain degree of deformation and coverage.

[0022] ③ Negative Poisson's ratio characteristics: Negative Poisson's ratio characteristics mean 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. 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 large deformations in all directions when unfolded. This has significant advantages for scenarios that require transportation through narrow spaces and require more comprehensive support (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 a highly asymmetric ratchet characteristic, resulting in different friction forces in different movement directions. This characteristic enables the serpentine arm to further enhance its ability to grasp the pipe wall in a specific direction during expansion in a pipeline environment (especially a pipeline environment where the pipe wall has a certain degree of flexible deformation), combined with the negative Poisson's ratio characteristic, which is conducive to the serpentine arm to anchor at any position in the pipeline, greatly enhancing the serpentine arm's ability to pass through narrow spaces.

[0024] ⑤ Axial controllable deformation characteristics: In order to achieve axial feeding and retraction, the traditional serpentine arm needs to be equipped with a propulsion device in this direction. However, the axial deformability of the serpentine arm of the present invention can be used as the axial feeding freedom due to the metamaterial. Compared with the traditional serpentine arm, the driver 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. In combination with anchoring and axial deformation at any position of the pipe wall in the pipe, the effect of the serpentine arm creeping forward in the pipe can be achieved, which further expands the movement mode and application range of the serpentine arm.

[0025] ⑥ Broad application prospects: The snake-like arm based on the characteristics of this metamaterial has a very broad application prospect, such as a pipeline operation snake-like arm robot that can be anchored at any position in the pipeline, an emergency structural repair / disaster relief robot that can achieve overall support at a specific position after passing through a narrow passage, a snake-like arm robot with excellent grasping performance, and a vascular stent robot that can walk autonomously in a blood vessel using its creeping forward ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an external structural diagram 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 external frame unit of the present invention.

[0031] Figure 5 These are multiple surface projection views of the mechanical metamaterial structure and the elastically deformable external frame unit of the present invention; taking (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 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 (a) 180 degrees to the left, (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 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] Fig. 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 zero Poisson's ratio deformation obtained by a single-row array of the mechanical metamaterial structure of the present invention.

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

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

[0038] Fig.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.A connecting rod 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 various parameter demonstrations listed are only preferred embodiments of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

[0041] Snake-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) is 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 arranged 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 made of fins (as shown Figure 3 The bionic scale is arranged on the elastically deformable external frame unit and conforms to the elastically deformable external frame unit.

[0053] A group of fins 10 are 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] An E group 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 by the present invention is provided with four connecting rods between the A vertical rod 1 and the B vertical rod 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 vertical rod A 1 and vertical rod B 2 are the same, and the structures of link A 3, link B 4, link C 5 and link D 6 are the same.

[0064] The joints between vertical rod A 1, 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 point 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, vertical rod A 1, link C 5, link D 6 and vertical rod B 2 are in the same plane, which is called the first plane, and vertical rod A 1 is parallel to vertical rod B 2.

[0066] See Figure 4B As shown, link A 3 and 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 by 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 the formation of friction anisotropy in the mechanical metamaterial structure in the direction of the scale edge, that is, different frictional forces are exhibited in different movement directions.

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

[0069] In Figure 4 , the included angle at the joint between the other end of link A 3 and one end of 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° - 45°. It looks like the Chinese character "卜" (radish) from the projection view.

[0071] In Figure 4In the embodiment, the size of the elastically deformable external frame unit is: the length of the A vertical rod 1 is recorded as H, the length of the C connecting rod 5 is recorded as L, and L = 0.3H to 1.5H. The diameters of the vertical rod and the connecting rod are the same, and the diameters are 0.5 mm to 30 mm.

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

[0073] exist Figure 5 Among the multiple face projections of the mechanical metamaterial structure (or the elastically deformable external frame unit), the front view of the elastically deformable external frame unit is a triangle. The rear view is the same as the front view, so the rear view is omitted. The right view of the elastically deformable external frame unit is in the shape of a radish.

[0074] The elastically deformable external frame unit designed in the present invention can deform when subjected to external forces while maintaining structural integrity and functionality.

[0075] Pipeline operation snake-arm robot

[0076] Figure 6 The pipeline operation snake-arm robot shown is assembled by using multiple mechanical metamaterial structures, such as Figure 7 As shown. Mechanical metamaterial structure (such as Figure 2 , Figure 3 After configuration, the following can be obtained: Figure 6 The pipeline operation snake-arm robot shown can be anchored at any position in the pipeline, and the snake-arm robot also has excellent grasping ability.

[0077] The mechanical metamaterial structure (such as Figure 2 , Figure 3 As shown in FIG. 1 , the space array is rolled into a roll-like structure as the main body of the serpentine arm, as shown in FIG. Figure 7 As shown, Figure 7 (b) Yes Figure 7 (a) The top view of the serpentine arm. This design not only gives the serpentine arm a unique appearance, but also brings a series of functional innovations. The serpentine arm has both friction anisotropy and negative Poisson's ratio. The combination of these two characteristics greatly expands the application range and efficiency of the serpentine arm.

[0078] The mechanical metamaterial structure with negative Poisson's ratio can significantly enhance the passability of the serpentine arm in narrow spaces. Its axial deformability can be utilized as the axial feeding freedom. At the same time, its radial radius will become thicker when extending (feeding) forward, which helps to improve the serpentine arm's ability to grip 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 Fig. 7A As shown, combining the two characteristics of negative Poisson's ratio and friction anisotropy, for pipeline environment ( Fig. 7A -a), the axial feed motion can be realized by utilizing the axial elastic deformation ( Fig. 7A -b), using the negative Poisson's ratio to achieve radial controllable deformation and friction anisotropy while axially extending and contracting, i.e., the release and locking of the ratchet pawl ( Fig. 7A -c), the serpentine arm can partially grasp the pipe wall while feeding. This allows the serpentine arm to be anchored at any position in the pipe, greatly enhancing the passability of the serpentine arm in narrow spaces. In addition, by controlling the local axial expansion and contraction of the serpentine arm with a specific rhythm (accompanied by radial expansion and compression), a worm-like peristaltic motion can be achieved in the pipe wall along the extension direction of the pipe.

[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 200 μm (as shown in the figure), the theoretical deformation has the characteristic of zero Poisson's ratio, that is, there is no change in the size in the direction of the scale edge when it is stretched or compressed in the direction perpendicular to the scale edge.

[0083] like Fig. 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, ensuring that the spatial array always has a ratchet-scale blade structure while having a negative Poisson's ratio characteristic, that is, when subjected to pressure, it will shrink and deform perpendicular to the direction of pressure, forming a tensile expansion and compression characteristic.

[0084] Friction Anisotropy

[0085] See also Fig.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 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-shaped arm of negative Poisson's ratio metamaterial for pipeline operation

[0087] See also Fig.11 As shown, the preferred size of a single mechanical metamaterial structure is: the vertical rod and the connecting rod are 304 capillary stainless steel tubes with a diameter of 0.7 mm; the length of the A vertical rod 1 and the B vertical rod 2 is H = 15 mm, the length of the connecting rod is L = 12 mm, the angle between the first plane and the second plane is α = 25°, δ = β 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 a 304 capillary stainless steel tube.

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

[0089]

[0090] The test was conducted on the tensile tester ALJ-50 (Fuzhou Aipu Instrument Co., Ltd.). Under the same test environment (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 the serpentine arm were pulled to produce relative motion, and the reading of the dynamometer during the relative motion was recorded as the friction resistance between the serpentine arm and the pipe. The test results show that there is a significant difference in the friction resistance in the direction along the scale and in the direction against the scale, and the friction resistance in the direction against the scale has a multiple gain effect relative to the direction along the scale.

[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 reduction 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, it is necessary to ensure that the mass ratio of components A and B is increased as much as possible on the basis of curability, and the curing time is prolonged 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 evenly, and then pre-degassed in a vacuum drying oven to expel the air mixed in during the stirring process, maintaining the vacuum degree <0.1 bar for about 2 minutes;

[0094] (C) After pre-degassing, the silicone rubber obtained in the previous step is poured onto the front side of template A until the required thickness is reached. After curing for 5 minutes, template B and a 0.4 kg weight plate are placed on top of the template A and vacuum degassed for another 5 minutes to expel the air stored between the contact surfaces.

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

Claims

1. A serpentine arm structure based on negative Poisson's ratio metamaterial, characterized in that: The snake-like robotic arm is obtained by arranging and configuring 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 joints between the A vertical rod (1), the B vertical rod (2) and the four connecting rods are forming processing conversion points; 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 denoted as α, and α=1° to 45°; The angle α between the lower end of the A vertical rod (1) and one end of the C connecting rod (5) is 下 The angle β between the other end of the C connecting rod (5) and one end of the D connecting rod (6) is equal to one half 下 ,Right now The angle δ between the other end of the A connecting rod (3) and one end of the B connecting rod (4) is equal to β 下 , that is, δ=β 下 ; 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.

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-like 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: The mechanical metamaterial structures are linearly arrayed in a first plane perpendicular to the scale edge direction to form a single row array.

4. 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.

5. The serpentine arm structure based on negative Poisson's ratio metamaterial according to claim 1, characterized in that: The bionic scale is a composite drag-reducing skin.

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

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 micro-fabricated using 3D printing technology.

8. 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.

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 metal or polymer material with a diameter of 0.5 mm to 30 mm; the metal may be stainless steel, aluminum alloy, nickel-based alloy, etc., or may be a nickel-based shape memory alloy.

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