A flexible mechanism with negative Poisson's ratio characteristics

Abstract

A flexible mechanism with negative Poisson's ratio characteristics is composed of a plurality of identical flexible units stacked together; the flexible unit is a symmetrical flexible Sarrus mechanism, characterized in that it comprises two identical isosceles trapezoidal plates and four identical rectangular plates, the six plates are connected by notch-type flexible hinges to form a single-degree-of-freedom spatial six-bar flexible mechanism, the six plates are respectively a first isosceles trapezoidal plate, a second isosceles trapezoidal plate, a first rectangular plate, a second rectangular plate, a third rectangular plate, and a fourth rectangular plate, each plate is provided with a notch-type flexible hinge on the opposite sides, and a plurality of the flexible units are periodically stacked together by sharing a common plate to form a hollow cylindrical flexible mechanism; when subjected to pressure in the direction of the cylindrical axis, the mechanism produces axial contraction and radial contraction, and when subjected to tension in the direction of the cylindrical axis, the flexible mechanism produces axial extension and radial extension; the flexible mechanism can be used in a precision snake-like robot to adjust the size of the robot.

Description

Technical Field

[0001] The invention relates to a hollow cylindrical flexible mechanism, in particular to a flexible mechanism with negative Poisson's ratio characteristics. Background Art

[0002] The Poisson's ratio of ordinary materials is generally a positive number. When it is subjected to pressure in one direction, it will shrink in that direction and expand in the vertical direction. When a structure with a negative Poisson's ratio is subjected to pressure in one direction, it will shrink in that direction and in the vertical direction at the same time. Negative Poisson's ratio structures have good rebound characteristics and fracture resistance, so they are widely used in buffering energy absorption, pressure bearing, explosion protection, robots, etc. Usually, negative Poisson's ratio structures are composed of cells of special shapes through periodic superposition. In the invention patent with publication number CN110015255A, an energy absorption box is disclosed. The energy absorption box is composed of multiple star-shaped cells through linear superposition and has good negative Poisson's ratio characteristics; in the utility model with publication number CN207882902U, an explosion-proof car door based on a negative Poisson's ratio structure is proposed, which can effectively improve the energy absorption during explosion; in the invention patent with publication number CN110801085A, a ring body structure based on a negative Poisson's ratio effect is disclosed, and its diameter can be adjusted, which is suitable for fat people to wear.

[0003] Most of the current negative Poisson's ratio structures are composed of cells stacked linearly, and fewer are composed of cells stacked circularly. When the negative Poisson's ratio structure obtained by cells stacked circularly is subjected to axial pressure, it will shrink in both the axial and radial directions, and can be applied to robots to adjust the robot's spatial dimensions. The existing negative Poisson's ratio structure formed by the circumferential superposition of cells is more flexible and has more deformable areas, making it suitable for non-precision purposes such as buffering and energy absorption; however, the deformation of this structure is more complex, making it difficult to establish an accurate kinematic model, and the shape controllability is not high, so its application in robots is limited. Summary of the invention

[0004] The present invention provides a negative Poisson's ratio flexible mechanism with simple structure, relatively concentrated flexibility and high controllability, which can be used in a precision snake-like robot to adjust the size of the robot.

[0005] The present invention provides a flexible mechanism with negative Poisson's ratio characteristics, which is composed of a plurality of identical flexible units stacked together. The flexible unit 1 is a symmetrical flexible Sarrus mechanism, which is characterized in that: it includes two identical isosceles trapezoidal plates and four identical rectangular plates, and the six plates are connected by notch-type flexible hinges to form a single-degree-of-freedom spatial six-bar flexible mechanism; the six plates are respectively a first isosceles trapezoidal plate, a second isosceles trapezoidal plate, a first rectangular plate, a second rectangular plate, a third rectangular plate, and a fourth rectangular plate; the first isosceles trapezoidal plate is connected to a long side of the first rectangular plate on one side of the waist by a first notch-type flexible hinge; the first isosceles trapezoidal plate is connected to a long side of the second rectangular plate on the other side of the waist by a second notch-type flexible hinge. The first rectangular plate is connected to one long side of the third rectangular plate at the other long side through a third notch-type flexible hinge; the second rectangular plate is connected to one long side of the fourth rectangular plate at the other long side through a fourth notch-type flexible hinge; the third rectangular plate is connected to one side waist of the second isosceles trapezoidal plate at the other long side through a fifth notch-type flexible hinge; the fourth rectangular plate is connected to one side waist of the second isosceles trapezoidal plate at the other long side through a sixth notch-type flexible hinge; the isosceles trapezoidal plate and the rectangular plate are rigid plates; a plurality of the flexible units are periodically superimposed through a common plate to form a flexible mechanism with negative Poisson's ratio characteristics. Two adjacent flexible units are superimposed through a common plate, and the common plate includes two methods: the first method is to share an isosceles trapezoidal plate and connect through a notch-type flexible hinge, and the second method is to share a rectangular plate and connect through a notch-type flexible hinge.

[0006] The thickness m of the isosceles trapezoidal plate and the rectangular plate in the flexible mechanism and the thickness n of the notch-type flexible hinge satisfy: 3<m / n<6. The first isosceles trapezoidal plate and the second isosceles trapezoidal plate in the flexible unit are parallel to each other, and the angle between the two waists of the isosceles trapezoidal plate in the flexible unit can divide 180 degrees; in the flexible mechanism, the trapezoidal surfaces of all isosceles trapezoidal plates are parallel to each other or coplanar.

[0007] The flexible mechanism is in the shape of a hollow cylinder and can be processed by 3D printing. When subjected to pressure in the direction of the cylindrical axis, the mechanism simultaneously produces axial contraction and radial contraction; when subjected to tension in the direction of the cylindrical axis, the mechanism simultaneously produces axial extension and radial extension. Due to this characteristic, the flexible mechanism can be used in a snake-like robot to adjust the size of the robot.

[0008] The flexible mechanism with negative Poisson's ratio provided by the present invention has the following beneficial effects. (1) The structure of the present invention is simple, easy to design by parameters, and can be processed by 3D printing; (2) The deformable area of ​​the present invention is relatively concentrated, the deformation process is easy to accurately model, and has a large deformation amplitude; (3) The two end faces of the present invention are completely parallel, which is convenient for applying pressure or tension. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the axial side of the present invention when it is not under stress.

[0010] Figure 2 It is a schematic diagram of the shaft side of the present invention under axial tension.

[0011] Figure 3 It is a schematic diagram of the shaft side of the present invention under axial compression.

[0012] Figure 4 It is an axial schematic diagram of the flexible unit of the present invention in a compressed state.

[0013] Figure 5 It is a schematic axial view of the flexible unit of the present invention when it is not under stress.

[0014] Figure 6 It is an axial schematic diagram of the flexible unit of the present invention in a stretched state.

[0015] Figure 7 It is a front schematic diagram of the flexible unit of the present invention in a compressed state.

[0016] In the figure: 1-flexible unit, 101-first isosceles trapezoidal plate, 102-second isosceles trapezoidal plate, 103-first rectangular plate, 104-second rectangular plate, 105-third rectangular plate, 106-fourth rectangular plate, 107-first notch flexible hinge, 108-second notch flexible hinge, 109-third notch flexible hinge, 110-fourth notch flexible hinge, 111-fifth notch flexible hinge, 112-sixth notch flexible hinge, 2-common isosceles trapezoidal plate, 3-common rectangular plate DETAILED DESCRIPTION

[0017] In order to further facilitate the understanding of the technical means and functions implemented by the present invention, the present invention is described in detail with reference to the accompanying drawings.

[0018] The present invention provides a flexible mechanism with negative Poisson's ratio characteristics, which is composed of a plurality of identical flexible units. Figure 1-Figure 3 As shown, the flexible unit is Figure 4-Figure 7As shown, the flexible unit is a symmetrical flexible Sarrus mechanism, which is characterized in that: it includes two identical isosceles trapezoidal plates and four identical rectangular plates, and the six plates are connected by notch-type flexible hinges to form a single-degree-of-freedom spatial six-bar flexible mechanism; the six plates are respectively a first isosceles trapezoidal plate 101, a second isosceles trapezoidal plate 102, a first rectangular plate 103, a second rectangular plate 104, a third rectangular plate 105, and a fourth rectangular plate 106; the first isosceles trapezoidal plate 101 is connected to a long side of the first rectangular plate 103 on one side of the waist through a first notch-type flexible hinge 107; the first isosceles trapezoidal plate 101 is connected to a long side of the second rectangular plate 104 on the other side of the waist through a second notch-type flexible hinge 108; the first rectangular plate 103 is connected to a long side of the second rectangular plate 104 on the other side of the waist through a second notch-type flexible hinge 108; One long side is connected to one long side of the third rectangular plate 105 through a third notch-type flexible hinge 109; the second rectangular plate 104 is connected to one long side of the fourth rectangular plate 106 at the other long side through a fourth notch-type flexible hinge 110; the third rectangular plate 105 is connected to one side waist of the second isosceles trapezoidal plate 102 at the other long side through a fifth notch-type flexible hinge 111; the fourth rectangular plate 106 is connected to one side waist of the second isosceles trapezoidal plate 102 at the other long side through a sixth notch-type flexible hinge 112; the isosceles trapezoidal flat plate and the rectangular flat plate are rigid plates; in the flexible unit 1, the first isosceles trapezoidal plate 101 and the second isosceles trapezoidal plate 102 are parallel to each other; and the angle between the two waists of the isosceles trapezoidal plates in the flexible unit 1 can be divided by 180 degrees.

[0019] like Figure 1 As shown, a plurality of the flexible units 1 are periodically superimposed through a common plate to form a flexible mechanism with negative Poisson's ratio characteristics. Two adjacent flexible units 1 are superimposed through a common plate, and the common plate includes two types: the first type is a common isosceles trapezoidal plate 2, and is connected through a notch-type flexible hinge; the second type is a common rectangular plate 3, and is connected through a notch-type flexible hinge. The thickness m of the isosceles trapezoidal plate and the rectangular plate in the flexible mechanism and the thickness n of the notch-type flexible hinge satisfy: 3<m / n<6. In the flexible mechanism, the trapezoidal surfaces of all isosceles trapezoidal plates are parallel or coplanar to each other. As Figure 1-Figure 3 As shown, the flexible mechanism is in the shape of a hollow cylinder and can be processed by 3D printing. When subjected to pressure in the direction of the cylindrical axis, the mechanism will simultaneously produce axial contraction and radial contraction; when subjected to tension in the direction of the cylindrical axis, the mechanism will simultaneously produce axial extension and radial extension. The flexible mechanism can be used as a module of a snake-like robot to adjust the radial size of the robot by applying an axial force.

[0020] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit it. All flexible units in the negative Poisson's ratio flexible mechanism of the present invention can adopt the same or different cross-sectional shapes, can use the same or different materials, and can be designed with functional parameters according to different usage requirements. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, and they should all be included in the scope of the claims of the present invention.

Claims

1. A flexible mechanism with negative Poisson's ratio characteristics, which is composed of a plurality of identical flexible units stacked together; the flexible unit (1) is a symmetrical flexible Sarrus mechanism, characterized in that: The invention comprises two identical isosceles trapezoidal plates and four identical rectangular plates, wherein the six plates are connected by notch-type flexible hinges to form a single-degree-of-freedom spatial six-bar flexible mechanism, wherein the six plates are respectively a first isosceles trapezoidal plate (101), a second isosceles trapezoidal plate (102), a first rectangular plate (103), a second rectangular plate (104), a third rectangular plate (105), and a fourth rectangular plate (106); the first isosceles trapezoidal plate (101) is connected to one long side of the first rectangular plate (103) on one waist by a first notch-type flexible hinge (107); the first isosceles trapezoidal plate (101) is connected to the long side of the second rectangular plate (104) on the other waist by a second notch-type flexible hinge (108); the first rectangular plate (103) is connected to one long side of the third rectangular plate (105) on the other long side by a third notch-type flexible hinge (109); The second rectangular plate (104) is connected to one long side of the fourth rectangular plate (106) at the other long side through a fourth notch-type flexible hinge (110); the third rectangular plate (105) is connected to one side waist of the second isosceles trapezoidal plate (102) at the other long side through a fifth notch-type flexible hinge (111); the fourth rectangular plate (106) is connected to one side waist of the second isosceles trapezoidal plate (102) at the other long side through a sixth notch-type flexible hinge (112); a plurality of the flexible units (1) are periodically superimposed through a common plate to form a flexible mechanism with negative Poisson's ratio characteristics; the thickness m of the isosceles trapezoidal plate and the rectangular plate in the flexible mechanism and the thickness n at the notch-type flexible hinge satisfy: 3<m / n<6; the isosceles trapezoidal plate and the rectangular plate are rigid plates.

2. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: In the flexible unit (1), the first isosceles trapezoidal plate (101) and the second isosceles trapezoidal plate (102) are parallel to each other.

3. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: Two adjacent flexible units (1) are stacked via a common flat plate, and the common flat plate includes two types: the first type is a common isosceles trapezoidal plate connected via a notch-type flexible hinge; the second type is a common rectangular plate connected via a notch-type flexible hinge.

4. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: In the flexible mechanism, the trapezoidal surfaces of all isosceles trapezoidal plates are parallel or coplanar with each other.

5. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: The included angle between the two waists of the mid-waist trapezoidal plate in the flexible unit (1) can divide 180 degrees.

6. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: The flexible structure can be processed by 3D printing.

7. The flexible mechanism with negative Poisson's ratio characteristic according to claim 1, characterized in that: The flexible mechanism is in the shape of a hollow cylinder. When subjected to pressure in the direction of the cylindrical axis, the flexible mechanism produces axial contraction and radial contraction; when subjected to tension in the direction of the cylindrical axis, the flexible mechanism produces axial extension and radial extension; it can be used in precision snake-like robots to adjust the size of the robot.

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