CN114670185A

CN114670185A - Unrestrained lightweight flexible electric heating pneumatic actuator and flexible clamping jaw

Info

Publication number: CN114670185A
Application number: CN202210463494.1A
Authority: CN
Inventors: 许明; 孙启民
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2022-06-28

Abstract

The invention discloses an unconstrained lightweight flexible electrothermal pneumatic actuator and a flexible clamping jaw. The actuator includes a first elastic layer, a liquid storage layer, a first confinement layer, a heating layer, and a second confinement layer, which are stacked in this order. The first elastic layer is connected with the edge of the opposite side surface of the liquid storage layer in a sealing way. The liquid storage layer is absorbed with conversion liquid; the boiling point of the conversion liquid is 30-50 ℃. When the conversion liquid is gasified, an expansion air cavity is formed between the first elastic layer and the liquid storage layer; the first limiting layer and the second limiting layer limit the length and the width of the brake to change; the expansion air chamber expands causing the actuator to bend. In the invention, a porous nanofiber pad is used for adsorbing the conversion liquid with a lower boiling point; heating the conversion liquid to boiling and gasifying, so that gas is generated in the actuator, and expansion bending is generated; repeated bending and straightening of the actuator can be realized through heating and cooling of the conversion liquid, and miniaturization and light weight of the bending actuator are realized.

Description

Unrestraint lightweight flexible electric heating pneumatic actuator and flexible clamping jaw

Technical Field

The invention belongs to the technical field of soft robots, and particularly relates to a pneumatic actuator and a flexible clamping jaw which are light in weight, portable and free of an external bolt connected with an air pump under the condition that flexible contact is needed.

Background

Flexible actuators are the core of soft robots and have evolved rapidly in recent years. There are many ways of driving flexible actuators, the most common and mature way of driving being pneumatic at present. Pneumatic actuation typically uses an external air pump to provide a source of high pressure air to the soft actuator. However, in practice, the soft actuator does not have the characteristics of light weight, portability and portability due to the bulkiness of the external air pump and the use of its associated mechanical components. In view of this problem, in recent years, pneumatic driving is performed by using gas generated or input by an external heat source, a magnetic field, or the like. However, this method still does not solve the problem of the portability of the pneumatic actuator. The present invention therefore proposes a containment structure in a stretchable material, which provides a source of gas inside it. The outside of the pneumatic actuator is only required to be connected with a small battery for supplying power, and the lightweight and portability functions of the pneumatic actuator are realized.

Disclosure of Invention

The invention aims to provide a method and a structure for realizing a lightweight and portable pneumatic flexible driver system, and provides a manufacturing process of the structure and materials thereof.

In a first aspect, the present invention provides an unconstrained lightweight flexible electrothermal pneumatic actuator comprising, in sequential order, a first elastic layer, a reservoir layer, a first confinement layer, a heating layer, and a second confinement layer. The first elastic layer is connected with the edge of the opposite side surface of the liquid storage layer in a sealing way. The liquid storage layer is absorbed with conversion liquid; the boiling point of the conversion liquid is 30-50 ℃. When the conversion liquid is gasified, an expansion air cavity is formed between the first elastic layer and the liquid storage layer; the first limiting layer and the second limiting layer limit the length and the width of the brake to change; the expansion air chamber expands causing the actuator to bend.

Preferably, the unconstrained lightweight flexible electrothermally pneumatic actuator further comprises a second elastic layer; the second elastic layer is arranged on one side, away from the heating layer, of the second limiting layer.

Preferably, the first elastic layer and the second elastic layer are made of silicone. The young's modulus of the first elastic layer is less than the young's modulus of the second elastic layer.

Preferably, the heating layer adopts an electric heating wire.

Preferably, the two length edges of the first elastic layer are both provided with limiting strips; the two limiting strips are symmetrical to each other, and the distance between the middle parts of the two limiting strips is smaller than the distance between the end parts of the two limiting strips.

Preferably, the liquid storage layer is a porous nanofiber mat absorbed with a conversion liquid.

Preferably, the porous nanofiber mat is made of polyacrylonitrile and N, N-dimethylformamide through electrospinning.

Preferably, the conversion solution is Novec 7000 solution.

Preferably, the liquid storage layer, the first restriction layer and the second restriction layer have the same length and width dimensions and are smaller than the length and width dimensions of the first elastic layer and the second elastic layer. The first elastic layer is joined to the second elastic layer at opposite side edges.

The preparation method of the unconstrained lightweight flexible electrothermal pneumatic actuator comprises the following steps:

dissolving polyacrylonitrile solution in N, N-dimethylformamide solution to form polymer solution; the polymer solution was added to the dispenser. The polymer silk is output by the dispenser and falls on a rotating roller collector; and taking off the cylindrical polymer layer formed on the roller collector, cutting, and dripping the conversion liquid to form a liquid storage layer.

Step two, curing the silica gel by using the mold, and adding the limiting strips on two sides in the curing process to form a first elastic layer

And step three, sequentially bonding the first elastic layer, the liquid storage layer, the first limiting layer, the heating layer and the second limiting layer together.

And step four, curing and molding the second elastic layer on one side, away from the heating layer, of the second limiting layer by using a mold.

In a second aspect, the present invention provides an unconstrained flexible jaw comprising a base and a plurality of said unconstrained lightweight flexible electro-thermal pneumatic actuators; the inner ends of the three actuators are all fixed with the base and are uniformly distributed along the circumference of the central axis of the base. The first resilient layer of the three actuators faces a side away from the central axis of the base.

The invention has the beneficial effects that:

1. in the invention, a porous nanofiber pad is used for adsorbing the conversion liquid with a lower boiling point; heating the conversion liquid to boiling and gasifying, so that gas is generated in the actuator, and expansion bending is generated; repeated bending and straightening of the actuator can be realized through heating and cooling of the conversion liquid, and miniaturization and light weight of the bending actuator are realized.

2. The invention realizes the electro-thermal-pneumatic conversion in the nano-fiber material containing liquid and the heating layer, and the small-sized battery and the circuit system can complete the energy supply and control of the actuator, thereby realizing the light-weight pneumatic drive, further getting rid of the problem that the traditional flexible pneumatic actuator is bolted with an external heavy driver, and realizing the portable light-weight self-drive.

4. The invention provides a porous nanofiber mat manufacturing method and a whole actuator manufacturing process aiming at the actuator structure and the material thereof, and the preparation of the actuator structure can be simply completed and the actuator structure has high stability.

Drawings

Fig. 1 is an exploded view of an actuator provided in embodiment 1 of the present invention.

Fig. 2 is a schematic cross-sectional view of an actuator provided in embodiment 1 of the present invention.

Fig. 3 is a schematic structural diagram of an actuator provided in embodiment 1 of the present invention in a bent state.

Fig. 4 is a flowchart of the preparation of the actuator provided in embodiment 1 of the present invention.

Fig. 5 is a schematic structural diagram of a flexible clamping jaw provided in embodiment 2 of the invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Example 1

As shown in fig. 1 and 2, an unconstrained lightweight flexible electro-thermal pneumatic actuator for realizing unidirectional bending actuation comprises a first elastic layer 1, a liquid storage layer 2, a first limiting layer 3, a heating layer 4, a second limiting layer 5 and a second elastic layer 6 which are sequentially stacked. The first elastic layer 1 and the second elastic layer 6 are both made of silica gel. The edges of the opposite side surfaces of the first elastic layer 1 and the liquid storage layer 2 are sealed and bonded together; the first elastic layer 1 is only contacted with the middle position of the opposite side surfaces of the liquid storage layer 2, so that an expansion air cavity 7 can be generated between the first elastic layer 1 and the liquid storage layer 2. The heating layer adopts an electric heating wire and is powered by a small battery and a circuit system 8.

As shown in fig. 1 and 2, the first elastic layer 1 includes a silicone film 1-1 and a restriction strip 1-2. The silicone film is a film of about 1mm thick made of a silicone material having a low Young's modulus and a high elongation. Limiting strips 1-2 are arranged at the edges of the two lengths of the silica gel film 1-1; the width of the middle part of the limiting strip 1-2 is larger than the width of the two ends. The limiting strips 1-2 adopt non-stretchable fiber layers arranged in a grid shape.

As shown in fig. 1, the liquid storage layer 2 is a porous nanofiber mat absorbed with a conversion liquid; the conversion liquid has volatility and low boiling point (30-50 ℃); the porous nanofiber mat is made of polyacrylonitrile and N, N-dimethylformamide through electrostatic spinning. The conversion solution is preferably Novec 7000 solution; the boiling point of the Novec 7000 solution is 35 c, enabling gas-liquid conversion to be accomplished at lower temperatures. When the conversion liquid is heated and gasified, the expansion air cavity 7 between the first elastic layer 1 and the liquid storage layer 2 is expanded; because the actuator is restrained by the restraint limiting strips 1-2, the first limiting layer 3 and the second limiting layer 5, the expansion of the expansion air cavity 7 mainly drives the actuator to be bent integrally along the length direction of the actuator.

The first and

second restriction layers

3 and 5 are made of the same material, and are flexible, low-stretchability thin films with a thickness of 300 μm, which allow the actuator to bend, but restrict the length and width of the actuator from changing. The first limiting layer 3 and the second limiting layer 5 both have high hydrophobicity and high temperature resistance.

The heating layer 4 is a rectangular ring-shaped heating wire with bendable stability and low resistivity. The second elastic layer 6 is a film made of a silicone material. The young's modulus of the second elastic layer 6 is greater than the young's modulus of the first elastic layer 1. The outline areas and the shapes of the liquid storage layer 2, the first limiting layer 3, the heating layer 4 and the second limiting layer 5 are the same. The outline areas of the first elastic layer 1 and the second elastic layer 6 are larger than the liquid storage layer 2 and other layer structures. The edges of the first elastic layer 1 and the second elastic layer 6 are bonded and fixed together, and the liquid storage layer 2, the first limiting layer 3, the heating layer 4 and the second limiting layer 5 are packaged inside.

As shown in fig. 2 and 3, the actuator operates in room temperature, and the driving principle and the operation mode thereof are as follows:

step one, as shown in fig. 2, the small battery and the circuit system 8 are controlled to be disconnected, that is, the heating layer 4 is not electrified and is in a non-operating state. The liquid storage layer 2 contains a conversion liquid in a liquid state at room temperature. The expansion air chamber 7 does not undergo expansion change.

Step two, as shown in fig. 3, when the actuator needs to be bent, the small battery and the circuit system 8 are connected, that is, the heating layer 4 is powered on, and the actuator is in a working state. The heating layer 4 operates to generate heat. The liquid storage layer 2 is at high temperature, and the conversion liquid contained in the liquid storage layer is rapidly converted into a gas state from a liquid state due to heating. At this time, the generated gas generates acting force on the periphery of the expansion gas cavity 7, and the acting force is larger along with the increasing of the gas. At this time, since the first elastic layer 1 has a high stretchability, the first restriction layer 3 and the second restriction layer 5 are hardly elastically deformed such as stretched. Therefore, when the expansion air cavity 7 expands asymmetrically, namely the first elastic layer 1 is stressed to expand and deform, the first limiting layer 3 only bends and deforms. Therefore, the actuator is subjected to bending deformation.

And step three, when the actuator needs to be straightened, the small battery and the circuit system 8 are controlled to be disconnected, the heating layer 4 stops heating, the temperature in the expansion air cavity is reduced under the action of heat exchange, and the gas in the expansion air cavity 7 is condensed into liquid and is adsorbed into the liquid storage layer 2 again. The volume of the expansion air chamber 7 is reduced to the initial state and the actuator is restored from the bent state to the straightened state.

The preparation method of the unconstrained lightweight flexible electro-thermal pneumatic actuator comprises the following steps

Step one, as shown in a part of fig. 4, dissolving polyacrylonitrile solution in N, N-dimethylformamide solution to form polymer solution; the polymer solution is added to the dispenser 11. The glue dispenser 11 outputs polymer filaments, and the polymer filaments fall on a roller collector 12 which rotates and has the radius of 200 mm; the rotating speed of the roller collector 12 is 200 r/min. The pinhole model of the dispenser 11 is 18G, and a potential difference of 8kV is applied to release the polymer solution. The distance between the roller collector 12 and the pinhole outlet of the dispenser 11 is 150 mm. Direct current is applied to the polymer solution for charging and electrostatic spinning. The dispenser 11 discharges the spun polymer at a fixed flow rate of 800. mu.L/h. Finally, a PAN-NF thin plate is formed, and then Novec 7000 solution is fully dripped on the PAN-NF thin plate to finally form the liquid storage layer 2.

Step two, as shown in part b of fig. 4, pouring the first silica gel solution into a mold 13 and curing to form a silica gel film 1-1; in the process of curing the silica gel, the limiting strips 1-2 are respectively attached to the two sides of the silica gel film 1-1 to form the first elastic layer 1.

And step three, as shown in the part c-g of fig. 4, sequentially bonding the first elastic layer 1, the liquid storage layer 2, the first limiting layer 3, the heating layer 4 and the second limiting layer 5 together.

Step four, as shown in part h of fig. 4, pouring a second silicone solution into the mold and curing, so that a second elastic layer 6 is formed on the outer side of the second restriction layer 5, and thus a complete actuator is obtained, as shown in part i of fig. 4. The second silica gel has greater hardness and Young's modulus than the first silica gel.

Example 2

An unconstrained flexible jaw comprising a base 10 and three unconstrained lightweight flexible electro-thermal pneumatic actuators as described in example 1; the inner ends of the three actuators are all fixed with the base 10 and are evenly distributed along the circumference of the central axis of the base 10. The first resilient layer 1 of the three actuators faces the side away from the central axis of the base 10. The three actuators share the same small battery and circuitry 8. When the heating layer 4 in the actuator is energized, the outer end of the actuator is bent synchronously inwards, forming a gripping action.

Claims

1. An unconstrained lightweight flexible electro-thermal pneumatic actuator, comprising: comprises a first elastic layer (1), a liquid storage layer (2), a first limiting layer (3), a heating layer (4) and a second limiting layer (5) which are sequentially overlapped; the first elastic layer (1) is connected with the edge of the opposite side surface of the liquid storage layer (2) in a sealing way; the liquid storage layer (2) is absorbed with conversion liquid; the boiling point of the conversion liquid is 30-50 ℃; when the conversion liquid is gasified, an expansion air cavity (7) is formed between the first elastic layer (1) and the liquid storage layer (2); the first limiting layer (3) and the second limiting layer (5) limit the length and the width of the brake to change; the expansion air cavity (7) expands to bend the actuator.

2. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: further comprising a second elastic layer (6); the second elastic layer (6) is arranged on one side, far away from the heating layer (4), of the second limiting layer (5); the first elastic layer (1) and the second elastic layer (6) are both made of silica gel; the Young's modulus of the first elastic layer (1) is smaller than that of the second elastic layer (6).

3. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: the heating layer adopts an electric heating wire.

4. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: limiting strips (1-2) are arranged on two length edges of the first elastic layer (1); the two limiting strips (1-2) are symmetrical to each other, and the distance between the middle parts of the two limiting strips (1-2) is smaller than the distance between the end parts of the two limiting strips (1-2).

5. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: the liquid storage layer (2) adopts a porous nanofiber mat absorbed with conversion liquid.

6. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 5, wherein: the porous nanofiber mat is prepared from polyacrylonitrile and N, N-dimethylformamide through electrostatic spinning.

7. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: the conversion solution is preferably a Novec 7000 solution.

8. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: the length and the width of the liquid storage layer (2), the first limiting layer (3) and the second limiting layer (5) are the same and smaller than those of the first elastic layer (1) and the second elastic layer (6); the first elastic layer (1) and the second elastic layer (6) are joined together at opposite side edges.

9. An unconstrained lightweight flexible electro-thermal pneumatic actuator according to claim 1, wherein: the preparation process comprises the following steps:

dissolving polyacrylonitrile solution in N, N-dimethylformamide solution to form polymer solution; adding the polymer solution into a dispenser (11); the polymer silk is output by a glue dispenser (11) and falls on a rotating roller collector (12); taking off and cutting the cylindrical polymer layer formed on the roller collector (12), and then dripping the cylindrical polymer layer into a conversion liquid to form a liquid storage layer (2);

secondly, curing the silica gel by using a mold, and adding limiting strips at two sides in the curing process to form a first elastic layer (1)

Step three, sequentially bonding the first elastic layer (1), the liquid storage layer (2), the first limiting layer (3), the heating layer (4) and the second limiting layer (5) together;

and fourthly, curing and molding a second elastic layer (6) on one side, far away from the heating layer (4), of the second limiting layer (5) by using a mold.

10. A flexible jaw, characterized by: comprising a base (10) and a plurality of unconstrained lightweight flexible electro-thermo-pneumatic actuators according to any of claims 1-9; the inner ends of the three actuators are all fixed with the base (10) and are uniformly distributed along the circumferential direction of the central axis of the base (10); the first elastic layer (1) of the three actuators faces to the side far away from the central axis of the base (10).