A negative pressure pneumatic artificial muscle actuator capable of active and passive deformation

Abstract

The present invention discloses a negative pressure pneumatic artificial muscle actuator capable of active and passive deformation, comprising a cylindrical flexible cavity inner layer and a flexible cavity outer layer, the flexible cavity outer layer being sleeved on the outside of the flexible cavity inner layer to form a double-layer structure sleeve, an open cylindrical spring being arranged in the inner cavity of the sleeve; the flexible cavity outer layer and the flexible cavity inner layer have the same structure, and are cast into a cylindrical shape by flexible material and lines; the lines are vertically and evenly arranged along the height direction of the cylinder inside the upper and middle walls of the cylinder to form a wired area; the lower part of the cylinder has no lines distributed to form a wireless area; the wired area of the flexible cavity outer layer and the wireless area of the flexible cavity inner layer in the double-layer structure sleeve are arranged relative to each other. The present invention utilizes a tensile layered variable stiffness structure regulated by negative pressure as a flexible cavity, taking into account the passive elongation and active contraction deformation of the negative pressure pneumatic artificial muscle actuator, while maintaining the large output stress and output strain characteristics of this type of actuator.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial muscle driving, in particular to a negative pressure pneumatic artificial muscle driver capable of active and passive deformation. Background Art

[0002] Artificial muscles refer to a type of actuator that can simulate the deformation characteristics of biological muscles and has flexibility. They have important application value in the fields of flexible / soft robots, wearable devices, medical devices, rehabilitation equipment, 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, and environmental friendliness. The key components of negative pressure pneumatic artificial muscle actuators include "support structure" and "flexible cavity". Under the action of negative air pressure, the soft cavity will shrink inward. By designing a suitable support structure inside it, the deformation mode of the soft cavity can be guided, thereby realizing the driving function of contraction and deformation to simulate muscles. Different negative pressure pneumatic actuators can be obtained by different support structure and flexible cavity designs, which are accompanied by corresponding advantages and disadvantages.

[0003] Existing literature S. Li, D. Vogt, D. Rus, et al., “Fluid-driven origami-inspired artificial muscles,” Proc. Natl. Acad. Sci. USA, 114(50): 13132-13137. J. Lee, H. Rodrigue. Origami-Based Vacuum Pneumatic Artificial Muscles with Large Contraction Ratios, Soft Robotics, 6(1): 109-117. The supporting structure of the negative pressure pneumatic artificial muscle actuator disclosed therein is composed of an origami structure or a hard thin plate, and the flexible cavity is composed of a non-stretchable (non-extensible) plastic film or fabric. Under the action of negative air pressure, the flexible cavity will shrink inward, thereby exerting a contraction force on the internal origami structure or hard thin plate, causing the entire structure to shrink and deform, thereby achieving the driving function. Studies have shown that using a non-stretchable material membrane as a flexible cavity can enable this type of actuator to obtain large output stress and output strain, while using a stretchable material as a flexible cavity will greatly weaken its output stress and output strain. The disadvantages of this type of structure are: (1) This type of artificial muscle can simulate the contraction and deformation of muscles, but due to the limitation of the non-stretchable flexible cavity material, it cannot achieve passive elongation deformation similar to muscles, which limits the application of this type of artificial muscle. (2) Even if the flexible cavity is made of stretchable materials and passive elongation deformation is achieved, its output stress and output strain will be greatly weakened. (3) This type of artificial muscle actuator is limited by the supporting structure, has a relatively large volume, and has a certain degree of adverse effect on its flexibility. Summary of the Invention

[0004] Aiming at the problem that existing negative pressure pneumatic artificial muscle actuators are difficult to achieve passive elongation and deformation, the present invention provides a negative pressure pneumatic artificial muscle actuator that can actively and passively deform.

[0005] The artificial muscle actuator of the present invention utilizes a spring as a supporting structure and a stretchable negative pressure-regulated soft variable-rigidity membrane as a flexible cavity, taking into account both passive elongation and active contraction deformation, while maintaining the large output stress and output strain characteristics of this type of actuator.

[0006] The present invention provides a negative pressure pneumatic artificial muscle actuator capable of active and passive deformation. The specific structure includes a cylindrical flexible cavity inner layer and a flexible cavity outer layer. The flexible cavity outer layer is sleeved on the outside of the flexible cavity inner layer to form a double-layer structure sleeve. An open cylindrical spring is disposed in the cavity within the sleeve. The outer diameter of the spring is equal to the inner diameter of the flexible cavity inner layer, and the free length of the spring is equal to the height of the sleeve. The upper and lower ends of the sleeve are sealed by sealing plates made of flexible material, and an trachea connector is disposed on one of the sealing plates. The trachea connector connects the gap between the flexible cavity outer layer and the flexible cavity inner layer and the internal space where the spring is located.

[0007] The flexible cavity outer layer and the flexible cavity inner layer have the same structure, being cast into a cylindrical shape from a flexible material and lines. The lines are evenly and vertically arranged along the height of the cylinder within the upper and middle walls, forming wired areas. The lower portion of the cylinder has no lines, forming a wireless area. In this double-layered sleeve, the wired area of the flexible cavity outer layer is positioned opposite the wireless area of the flexible cavity inner layer.

[0008] The lines and flexible materials used in the flexible cavity inner layer and the flexible cavity outer layer may be the same or different in material selection.

[0009] Preferably, the thread is selected from cotton thread or hemp thread.

[0010] Preferably, the flexible material comprises one of silicone rubber, Ecoflex, and hydrogel.

[0011] The spring can be a common spring or a plastic spring.

[0012] Compared with the prior art, the present invention is beneficial in that:

[0013] The present invention utilizes a stretchable negative pressure-controlled soft layered variable-stiffness structure to create a flexible cavity, achieving an artificial muscle that allows for both passive stretching and active contraction. Specifically, when no negative pressure is applied, the material of the flexible cavity is in a state of low stiffness, allowing the artificial muscle to passively stretch and deform. However, when negative pressure is applied, the material stiffness of the flexible cavity increases, reaching an inextensible state, allowing the artificial muscle to actively contract and output large strains and stresses. Furthermore, the negative pressure driving the artificial muscle is connected to the negative pressure regulating the stiffness of the flexible cavity material. This means that a single negative pressure can simultaneously regulate the stiffness of the flexible cavity and contract the artificial muscle, without increasing the number of driving air sources, ensuring a compact structure.

[0014] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1, schematic structural diagram of the flexible cavity inner layer and the flexible cavity outer layer.

[0016] Figure 2 , schematic diagram of the spring structure.

[0017] Figure 3 , Schematic diagram of the structure of the negative pressure pneumatic artificial muscle driver that can be actively and passively deformed according to the present invention.

[0018] Numbers in the figure:

[0019] 1-trachea connector, 2-spring, 3-flexible cavity inner layer, 4-line, 5-flexible cavity outer layer, 6-sealing plate, 1-1-wired area, 1-2-wireless area. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0021] like Figure 1-3 As shown, the negative pressure pneumatic artificial muscle actuator capable of active and passive deformation provided by the present invention comprises a cylindrical flexible cavity inner layer 3 and a flexible cavity outer layer 5; the flexible cavity outer layer 5 is sleeved on the outside of the flexible cavity inner layer 3 to form a double-layer structure sleeve. The height of the flexible cavity inner layer 3 and the flexible cavity outer layer 5 are the same, that is, equal to the height of the sleeve. An open cylindrical spring 2 is arranged in the inner cavity of the sleeve, the outer diameter of the spring 2 is equal to the inner diameter of the flexible cavity inner layer, and the free length of the spring 2 is equal to the height of the sleeve. The upper and lower ends of the sleeve are sealed by a sealing plate 6, which is made of a flexible material; and an air pipe joint 1 is arranged on one of the sealing plates. The air pipe joint 1 connects the gap between the flexible cavity outer layer 5 and the flexible cavity inner layer 3, as well as the internal space where the spring 2 is located, so as to simultaneously apply negative air pressure to the flexible cavity and the actuator.

[0022] The flexible cavity outer layer 5 and the flexible cavity inner layer 3 have the same structure and are cast into a cylindrical shape from a flexible material and lines 4. During the molding process, the lines 4 are solidified into the flexible material. The lines 4 are evenly arranged vertically along the height of the cylinder, forming a wired area 1-1 on the upper and middle walls of the cylinder; the lower part of the cylinder has no lines, forming a wireless area 1-2. In the resulting double-layer sleeve, the wired area of the flexible cavity outer layer is arranged opposite the wireless area of the flexible cavity inner layer. For example, if the wired area of the flexible cavity inner layer is located at the lower end of the driver, then the wired area of the flexible cavity outer layer is located at the upper end of the driver, and vice versa.

[0023] The preparation process of the artificial muscle actuator of the present invention is as follows:

[0024] The first step is to prepare a flexible cavity outer layer 5 and a flexible cavity inner layer 3 by casting liquid flexible materials and lines through molds of different sizes;

[0025] The second step is to sleeve the flexible cavity outer layer 5 onto the flexible cavity inner layer 3 to form a sleeve. The spring is then installed in the internal cavity of the flexible cavity inner layer 3. The upper and lower ends of the sleeve are then sealed, and the trachea connector 1 is provided. The sealing plate of the sealing sleeve is made of a flexible material. The sealing method can be to first cast a circular sealing plate made of liquid flexible material, and then use an adhesive to bond the sealing plate to the upper and lower ends of the sleeve. Another method is to pour the liquid flexible material into the mold of the paper cup sealing plate, and then insert one end of the sleeve below the liquid level of the liquid flexible material in the mold. The liquid flexible material is dried and solidified to form a whole with the sleeve, thus achieving the purpose of sealing. The other end of the sleeve is sealed using the same method.

[0026] When the driver of the present invention is stretched and deformed, negative air pressure is not applied. At this time, no extrusion occurs between the inner and outer layers of the flexible cavity, and there is no friction. The wireless areas of the inner and outer layers of the flexible cavity can be stretched and deformed. When the driver is contracted and deformed, negative air pressure is applied. At this time, extrusion occurs between the inner and outer layers of the flexible cavity, generating friction, which hinders the relative sliding of the two. The wire-containing area of one layer will hinder the deformation of the wireless area of the other layer, and finally the entire flexible cavity layer becomes a non-stretchable cavity. This is consistent with the use of non-stretchable material cavities in the prior art. The driver will contract and deform, and at the same time have a larger output stress and output strain.

[0027] In summary, the present invention utilizes a negative pressure-regulated stretchable layered variable stiffness structure as a flexible cavity, taking into account the passive elongation and active contraction deformation of the negative pressure pneumatic artificial muscle driver, while maintaining the large output stress and output strain characteristics of this type of driver, so that the artificial muscle driver can simulate all the deformation behaviors of biological muscles; and the negative air pressure that drives the artificial muscle and the negative air pressure that regulates the stiffness of the flexible cavity can be connected, so only one negative air pressure can be used to simultaneously achieve the stiffness adjustment of the flexible cavity and the contraction deformation of the artificial muscle, thereby ensuring the compactness of the structure.

[0028] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A negative pressure pneumatic artificial muscle actuator capable of active and passive deformation, characterized in that: It includes a cylindrical flexible cavity inner layer and a flexible cavity outer layer. The flexible cavity outer layer is sleeved on the outside of the flexible cavity inner layer to form a double-layer structure sleeve. An open cylindrical spring is set in the cavity inside the sleeve. The outer diameter of the spring is equal to the inner diameter of the flexible cavity inner layer. The free length of the spring is equal to the height of the sleeve. The upper and lower ends of the sleeve are sealed by sealing plates, and a trachea joint is set on one of the sealing plates. The outer layer and the inner layer of the flexible cavity have the same structure and are cast into a cylindrical shape by flexible material and lines; the lines are vertically and evenly arranged along the height direction of the cylinder inside the upper and middle walls of the cylinder to form a wired area; there is no line distribution in the lower part of the cylinder to form a wireless area; the wired area of the outer layer of the flexible cavity in the double-layer structure sleeve is located at the upper end of the driver, and the wired area of the inner layer of the flexible cavity is located at the lower end of the driver; or, the wired area of the outer layer of the flexible cavity in the double-layer structure sleeve is located at the lower end of the driver, and the wired area of the inner layer of the flexible cavity is located at the upper end of the driver.

2. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 1, characterized in that: The thread is selected from cotton thread or hemp thread.

3. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 2, characterized in that: The flexible material includes one of silicone rubber, Ecoflex, and hydrogel.

4. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 3, characterized in that: The lines and flexible materials used in the flexible cavity inner layer and the flexible cavity outer layer are the same or different.

5. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 1, characterized in that: The spring is a common spring or a plastic spring.

6. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 1, characterized in that: The trachea joint communicates with the gap between the flexible cavity outer layer and the flexible cavity inner layer, as well as the internal space where the spring is located.

7. The negative pressure pneumatic artificial muscle actuator capable of active and passive deformation according to claim 1, characterized in that: The sealing plate is made of flexible material.

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