A Negative Pressure Pneumatic Artificial Muscle Actuator with Built-in Pre-Strain

Abstract

The present invention discloses a negative pressure pneumatic artificial muscle driver with built-in pre-strain, which includes an extendable and deformable flexible cavity and a wire cage-shaped support structure arranged in the pre-stretched flexible cavity; the support structure includes at least three support plates with the same outer contour arranged in parallel from top to bottom, and several inextensible flexible wires are vertically connected between two adjacent support plates. The flexible wires are evenly distributed at equal intervals along the edge of the support plate to form a flexible wire group, thus forming a wire cage-shaped support structure; an air hole is opened at the center of the top support plate for negative pressure driving, and holes are opened in the middle of all intermediate support plates except the top support plate and the bottom support plate; the flexible cavity is cylindrical. After the flexible cavity is pre-stretched circumferentially until its inner diameter is equal to the outer diameter of the support structure, the support structure is placed in the flexible cavity, and then the flexible cavity is sealed to obtain the artificial muscle driver. The present invention solves the problems of uncertainty in the output characteristics and poor controllability of the negative pressure pneumatic artificial muscle driver.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial muscle drive, and in particular to a negative pressure pneumatic artificial muscle driver with built-in pre-strain. Background Art

[0002] Artificial muscles refer to a type of driver that can simulate the deformation characteristics of biological muscles and is flexible, and has important application values in the fields of flexible / soft robots, wearable devices, medical devices, rehabilitation devices, etc. At present, negative pressure pneumatic artificial muscles have great development potential due to their high power density, large output strain, good safety, compact structure, environmental friendliness and other advantages. Currently, negative pressure pneumatic artificial muscle drivers mainly consist of two parts: a support structure (such as a spring, origami structure, rubber beam, etc.) and an inextensible flexible cavity (such as a plastic bag, plastic cavity, fabric bag, etc.). Under the action of negative air pressure, the soft cavity will contract inward. By designing a suitable support structure inside it, the deformation mode of the soft cavity can be guided, and then the contraction deformation can be realized to simulate the driving function of the muscle. By different support structure and flexible cavity designs, different negative pressure pneumatic drivers can be obtained. However, under the action of negative air pressure, the flexible cavity will contract inward, and at the same time the artificial muscle will contract along the axis. During this process, the inextensible flexible cavity will produce wrinkles and buckling deformations. The randomness of the wrinkles and buckling deformations leads to certain uncertainties in the deformation and output force of this type of artificial muscle driver, and it cannot be applied to actual scenarios with high accuracy requirements.

[0003] In order to weaken the uncertainty of the epidermal wrinkle deformation during the contraction process of this type of artificial muscle driver, one method is to design an origami structure for the epidermis. By folding the corners of the epidermis, during the contraction process of the artificial muscle, the epidermis can deform orderly according to the creases, thereby weakening the uncertainty of the wrinkle deformation and obtaining a negative pressure pneumatic artificial muscle driver with high deformation accuracy and good controllability. This type of artificial muscle can simulate the contraction deformation of the muscle, but due to relying on inextensible flexible cavity materials, random wrinkles and buckling deformations occur in the flexible cavity during the contraction deformation process, reducing the accuracy and controllability of the deformation of this type of driver, which brings limitations to practical applications. Moreover, during the deformation process of the artificial muscle driver under negative pressure, the generation of wrinkles also weakens the overall flexibility of the driver to a certain extent. In addition, through origami design, the flexible cavity can deform orderly as the artificial muscle driver contracts and deforms, but this method is not applicable to circular cross-section drivers and also brings design complexity. Summary of the Invention

[0004] In order to solve the problems of uncertainty in the output characteristics and poor controllability of negative pressure pneumatic artificial muscle drivers, the present invention provides a negative pressure pneumatic artificial muscle driver with built-in pre-strain.

[0005] The negative pressure pneumatic artificial muscle driver with built-in pre-strain provided by the present invention includes a flexible cavity that can be elongated and deformed, and a wire cage-shaped support structure arranged inside the flexible cavity after pre-stretching.

[0006] The support structure includes at least three support plates with the same outer contour arranged in parallel from top to bottom, and several non-elongable flexible wires are vertically connected between two adjacent support plates. The lengths of all the flexible wires are equal, and each is equal to the distance between two support plates. The flexible wires are evenly distributed at equal intervals along the edge of the support plate to form a flexible wire group, thus forming a wire cage-shaped support structure. An air hole is opened at the center of the support plate located at the top of the support structure for negative pressure driving use, and holes are opened in the middle of all intermediate support plates except the top and bottom support plates. The outer shape of the support plate can be one of a circle, a semi-circle or a polygon. Preferably, the support plate is circular, and all intermediate support plates except the top and bottom support plates are circular rings with circular holes opened in the middle.

[0007] The pre-stretched flexible cavity is obtained by stretching the initial flexible cavity along the circumferential direction. The initial flexible cavity is formed by casting or 3D printing using one of the materials such as silicone rubber, Ecoflex, and hydrogel. The initial flexible cavity is a cylindrical shape with one end open; the initial inner diameter of the cylinder is smaller than the outer diameter of the support structure. After pre-stretching the initial flexible cavity along the circumferential direction until its inner diameter is equal to the outer diameter of the support structure, the support structure is placed inside the flexible cavity to support the flexible cavity, and then the opening of the flexible cavity is sealed to obtain the negative pressure pneumatic artificial muscle driver with built-in pre-strain.

[0008] Preferably, the support plate is made of one of the materials such as resin, plastic, metal or wood.

[0009] Preferably, all the support plates are arranged at equal intervals up and down.

[0010] Preferably, the flexible wire is selected from one of cotton thread, hemp thread, and nylon thread; the flexible wire and the support plate are connected by bonding or anchoring.

[0011] The artificial muscle driver of the present invention undergoes passive elongation deformation: under the action of an external load, the artificial muscle driver will undergo elongation deformation, the distance between the support structures increases, causing the flexible wires to stretch, and by restricting the outward deformation of the flexible cavity until the flexible wires are completely straightened and reach the initial design length. This process is the passive elongation process of the driver.

[0012] The active contraction process of the driver under negative pressure: under the action of negative air pressure, the flexible cavity contracts inward, generating tension inside the flexible wires. The tension acts on the support structure, causing the support structure to contract and output a driving force.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) The artificial muscle actuator provided by the present invention uses a non-elongable flexible wire group connected to a support structure to form a wire cage structure. A stretchable soft material is used as the flexible cavity, and the flexible cavity is pre-stretched circumferentially in advance and supported by the wire cage structure, so that there is a certain pre-strain inside. During the contraction of the artificial muscle under negative pressure, the pre-strain inside the flexible cavity is gradually released with deformation, ensuring that the flexible cavity does not produce wrinkles or buckling deformation, while maintaining the advantages of large output stress and output strain of this type of actuator.

[0015] (2) By the idea of built-in pre-strain, the problems of uncertainty and poor controllability of the output characteristics of the negative pressure pneumatic artificial muscle actuator are solved, and a new type of negative pressure pneumatic artificial muscle with accurately describable and controllable driving behavior is obtained.

[0016] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Structural schematic diagram of the negative pressure pneumatic artificial muscle actuator with built-in pre-strain of the present invention.

[0018] Reference numerals in the figure:

[0019] 1 - Support plate, 2 - Flexible wire, 3 - Initial flexible cavity, 4 - Flexible cavity after pre-stretching, 5 - Artificial muscle actuator, 6 - Support structure, 7 - Air hole, 8 - Middle opening, 9 - Sealing cover plate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not used to limit the present invention.

[0021] As Figure 1 shown, the negative pressure pneumatic artificial muscle actuator with built-in pre-strain provided by the present invention includes an initial flexible cavity 3 that can be stretched and deformed and a wire cage-shaped support structure 6 disposed inside the flexible cavity 4 after pre-stretching.

[0022] The support structure 6 includes at least three support plates 1 with the same outer contour arranged in parallel from top to bottom. Adjacent support plates 1 are vertically connected by several inextensible flexible lines 2. The lengths of all the flexible lines 2 are equal and are all equal to the distance between two support plates 1. The flexible lines 2 are evenly distributed at equal intervals along the edge of the support plate 1 to form a flexible line group, and finally a wire cage-shaped support structure 6 is formed. An air hole 7 is opened at the center of the top support plate for negative pressure driving. Holes 8 are opened in the middle of all intermediate support plates except the top support plate and the bottom support plate. The outer shape of the support plate can be one of a circle, a semicircle or a polygon. Preferably, the support plate 1 is circular, and all intermediate support plates except the top support plate and the bottom support plate are circular rings with circular holes opened in the middle; there are multiple intermediate support plates, and adjacent support plates are arranged at equal intervals.

[0023] After pre-stretching, the flexible cavity 4 is obtained by stretching the initial flexible cavity 3 along the circumferential direction. The initial flexible cavity 3 is formed by casting or 3D printing with a material such as silicone rubber, Ecoflex, or hydrogel. The initial flexible cavity 3 is a cylindrical shape with one end open. The initial inner diameter of the initial flexible cavity 3 is smaller than the outer diameter of the support structure 6. The initial flexible cavity 3 is pre-stretched along the circumferential direction to obtain the pre-stretched flexible cavity 4, so that a certain strain is pre-stored inside its material along the circumferential direction. The inner diameter of the pre-stretched flexible cavity 4 is the same as the diameter of the support structure 6. The support structure 6 is placed in the pre-stretched flexible cavity 4 to support the pre-stretched flexible cavity 4, and then the pre-stretched flexible cavity 4 is sealed with a sealing cover plate 9 to obtain a negative pressure pneumatic artificial muscle driver 5 with internal pre-strain. In the initial state, due to the existence of the pre-strain in the flexible cavity, the artificial muscle driver will contract, making the height of the flexible cavity the same as the height of the support structure. The material of the sealing cover plate 9 is the same as the material used for the flexible cavity, and it is also made of flexible materials such as silicone rubber, Ecoflex, and hydrogel. The sealing cover plate 9 and the pre-stretched flexible cavity 4 can be fixed and sealed by bonding, but it is not limited to this form of fixation.

[0024] The design of the wire cage structure in the present invention can constrain the deformation of the flexible cavity during the passive elongation or active contraction deformation of the driver. That is, the flexible line group will always fit with the flexible cavity, and the inextensible property of the flexible line converts the deformation of the flexible cavity into a tensile force acting on the support structure, ensuring the advantages of large output force and output deformation of this type of driver.

[0025] By pre-stretching the initial flexible cavity, pre-strain exists inside it in advance. During its contraction deformation, the internal strain is gradually released but is always non-zero, thereby ensuring that the wall surface of the flexible cavity does not fold or buckle, and realizing stable and accurately controllable deformation behavior.

[0026] In summary, the present invention utilizes a wire cage structure combined with a stretchable and deformable flexible cavity. By means of the idea of built-in pre-strain, the problems of uncertainty in the output characteristics and poor controllability of the negative pressure pneumatic artificial muscle driver are solved, and a new type of negative pressure pneumatic artificial muscle with accurately describable and controllable driving behavior is obtained. At the same time, the passive elongation and active contraction deformation of the negative pressure pneumatic artificial muscle driver are taken into account, and the large output stress and output strain characteristics of this type of driver are maintained. This type of driver has a compact structure and low manufacturing cost, which is conducive to practical applications in production and life.

[0027] The above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or equivalent changes and modifications using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as the content does not depart from the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A negative pressure pneumatic artificial muscle actuator with built-in prestrain, characterized in that: It includes a flexible cavity that can be stretched and deformed, and a wire cage type support structure arranged in the pre-stretched flexible cavity; The support structure includes at least three support plates with the same outer contour arranged in parallel from top to bottom, and two adjacent support plates are vertically connected by a plurality of inextensible flexible wires, the lengths of all flexible wires being equal to the distance between the two support plates, and the flexible wires being evenly distributed at equal intervals along the edges of the support plates to form a flexible wire group, forming a wire cage-type support structure; The center of the support plate at the top of the support structure has an air hole for negative pressure drive. The middle of all the middle support plates has an opening, and the bottom support plate has no opening. The pre-stretched flexible cavity is obtained by stretching the initial flexible cavity along the circumferential direction; the initial flexible cavity is a cylinder with an open end, and the initial inner diameter of the cylinder is smaller than the outer diameter of the supporting structure. After the initial flexible cavity is pre-stretched along the circumferential direction until its inner diameter is equal to the outer diameter of the supporting structure, the supporting structure is placed in the flexible cavity to support the flexible cavity, and then the opening of the flexible cavity is sealed to obtain a negative pressure pneumatic artificial muscle actuator with built-in prestrain.

2. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: The support plate is in the shape of a circle, a semicircle or a polygon.

3. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 2, characterized in that: The support plate is made of one of resin, plastic, metal or wood.

4. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: All support plates are set at equal intervals up and down.

5. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: The flexible line is selected from one of cotton line, hemp line and nylon line.

6. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 5, characterized in that: The flexible wire is connected to the support plate by bonding or anchoring.

7. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: The initial flexible cavity is formed from silicone rubber by casting or 3D printing.

8. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: The initial flexible cavity is formed by Ecoflex through casting or 3D printing.

9. The negative pressure pneumatic artificial muscle actuator with built-in prestrain according to claim 1, characterized in that: The initial flexible cavity is formed from hydrogel by casting or 3D printing.

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