CN112428259A

CN112428259A - Self-sensing bag type pneumatic artificial muscle based on shrinkage amplification mechanism

Info

Publication number: CN112428259A
Application number: CN202010973383.6A
Authority: CN
Inventors: 左思洋; 解迪生; 刘建彬
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2020-09-16
Filing date: 2020-09-16
Publication date: 2021-03-02
Anticipated expiration: 2040-09-16
Also published as: CN112428259B

Abstract

The invention discloses a self-sensing bag type pneumatic artificial muscle based on a shrinkage amplification mechanism, which comprises: the device comprises a rectangular flat multi-chamber air bag and a shrinkage rate amplifying mechanism matched with the multi-chamber air bag, wherein the shrinkage rate amplifying mechanism comprises an I-shaped frame formed by connecting two transverse plates and a longitudinal plate and two metal columns arranged between the two transverse plates, the two metal columns are symmetrically arranged at two sides of the longitudinal plate, and a first gap and a second gap are formed between the longitudinal plates respectively; the multi-chamber air bag sequentially penetrates through the first gap, the top end of the longitudinal plate and the second gap to be connected with the frame, and air bag chambers are uniformly distributed on one side of the longitudinal plate; and a displacement sensor for feeding back the displacement of the artificial muscle is arranged between the frame and the multi-chamber air bag. The pneumatic muscle has the characteristics of high shrinkage, high integration, self-sensing and easy expansion.

Description

Self-sensing bag type pneumatic artificial muscle based on shrinkage amplification mechanism

Technical Field

The invention relates to the technical field of artificial muscles, in particular to a self-sensing bag type pneumatic artificial muscle based on a shrinkage amplification mechanism.

Background

The pneumatic artificial muscle is an actuator which is powered by an external air pressure source and outputs pushing and pulling acting force outwards. The bionic robot has the characteristics of high compliance, high power-to-mass ratio, high man-machine compatibility and the like, and is widely applied to scenes such as bionic robots, medical robots, exoskeletons, industries and the like.

However, the contraction rate of the conventional positive pressure driven artificial muscle is generally about thirty percent, and the thickness or the radial direction of the artificial muscle is drastically changed during action, so that the artificial muscle cannot be used in high-compactness application, and if the contraction rate is to be increased, for example, the Mckibben muscle, the radial expansion factor of the artificial muscle needs to be greatly increased. The higher the shrinkage, the greater the radial variation, causing it to cause additional compression on the skin in wearable device applications, reducing the wearing comfort. In addition, existing artificial muscle control generally relies on external sensors, typically a dynamometer, a displacement sensor, etc., which causes the device to be bulky and provides unnecessary rigid components in the device.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a self-sensing bag type pneumatic artificial muscle based on a shrinkage rate amplifying mechanism, which can obtain higher shrinkage rate, has no thickness change during action, avoids additional extrusion, has higher shrinkage rate and does not extrude skin; and has self-sensing property, so that the volume of the device is more compact.

The technical scheme adopted for realizing the purpose of the invention is as follows:

a self-sensing bag-type pneumatic artificial muscle based on a shrinkage amplification mechanism comprises:

the device comprises a rectangular flat multi-chamber air bag and a shrinkage rate amplifying mechanism matched with the multi-chamber air bag, wherein the shrinkage rate amplifying mechanism comprises an I-shaped frame formed by connecting two transverse plates and a longitudinal plate and two metal columns arranged between the two transverse plates, the two metal columns are symmetrically arranged at two sides of the longitudinal plate, and a first gap and a second gap are formed between the longitudinal plates respectively; the multi-chamber air bag sequentially penetrates through the first gap, the top end of the longitudinal plate and the second gap to be connected with the frame, and air bag chambers are uniformly distributed on one side of the longitudinal plate; and a displacement sensor for feeding back the displacement of the artificial muscle is arranged between the frame and the multi-chamber air bag.

The multi-chamber air bag comprises a joint part and a non-joint part, wherein the non-joint part forms the air bag and the air passage which are communicated, and the joint part is arranged between two adjacent air bags.

The displacement sensor comprises electrode plates which are respectively arranged on the contact surfaces of the frame and the multi-cavity air bag, an insulating layer is coated on one of the electrode plates to form a capacitance sensor, and the capacitance sensor is connected with the capacitance voltage conversion module through a lead to form the displacement sensor.

And holes are formed in the transverse plate to install the metal columns.

The transverse plates are triangular plates, and the longitudinal plates are arranged in an axisymmetric mode.

The invention improves the shrinkage rate of the positive-pressure artificial muscle, solves the problem of additional extrusion to the human body caused by thickness expansion when the positive-pressure pneumatic muscle is applied to wearable auxiliary equipment, and solves the problem that the existing artificial muscle does not have a proper built-in displacement sensor; compared with the traditional pneumatic muscle, the pneumatic muscle has the characteristics of high shrinkage rate, high integration, self-sensing and easiness in expansion.

Drawings

FIGS. 1a-1b are schematic diagrams of a multi-chambered bladder of a self-sensing bag-type pneumatic artificial muscle based on a contraction rate amplification mechanism inflated before and inflated after, respectively;

FIGS. 1c-1d are schematic diagrams of the inflation of a self-sensing bag-type pneumatic artificial muscle based on a contraction rate amplification mechanism before and after inflation, respectively;

FIGS. 2a-2b are three-dimensional and top views of a shrinkage magnification mechanism of the present invention;

FIG. 3a is a schematic view of a method of making a multi-chamber bladder;

FIG. 3b is a schematic view of a method of installing the airbag into the frame;

FIGS. 4a-4c are schematic views of the driving of the artificial muscle of the present invention;

fig. 5a-5c are schematic diagrams illustrating the principle of detecting the expansion displacement of the artificial muscle by adding the capacitance displacement sensor according to the invention.

[ notation ] 1-balloon; 2-a frame; 3-a metal rod; 4, opening holes; 5-a binding moiety; 6-nonbonding portion; 7-electrode slice.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The self-sensing positive pressure driven pneumatic artificial muscle based on the modular design, which increases the soft pneumatic muscle shrinkage rate by the hard frame, can be used in application scenes of a flexible exoskeleton system, a bionic robot system and the like.

As shown in figure 1, the self-sensing bag type pneumatic artificial muscle based on the shrinkage amplification mechanism comprises: a multi-chamber airbag 1, a shrinkage ratio enlarging mechanism, and an electrode sheet 7.

The multi-chamber air bag is divided into an expansion part, a non-expansion part and an air passage. All three parts are formed by hot pressing two thermoplastic materials once according to a certain rule. The non-expansion part is a hot pressing or bonding joint part, and the air channel and the expansion part are non-hot pressing or bonding parts, namely two thermoplastic materials are not bonded and are surrounded by the surrounding hot pressing part to form an air channel capable of passing air and an expansion chamber. The thickness of the two thermoplastic materials can be designed according to actual needs, and the thicker the thermoplastic materials, the higher the overall strength. When the air bag is not inflated, the multi-cavity air bag is flat; when the high-pressure gas is filled in the air passage, the multi-chamber air bag expands and contracts in the length direction to exert the effect of output force. The muscles may contract in the vertical direction after inflation of the respective bladder chambers.

In the above technical solution, the multi-chamber airbag may be formed by hot pressing or bonding thermoplastic soft materials, such as TPU, PE, and the like, and the strength of the airbag may be further improved by hot pressing the woven fabric and the thermoplastic material.

The shrinkage amplification mechanism is an I-shaped structural frame 2 and consists of transverse plates and longitudinal plates on two sides. The diaphragm bottom has four trompils, can penetrate two metal bars. A gap exists between the metal rod and the longitudinal plate, and the metal rod can penetrate through the multi-chamber air bag. And sequentially enabling the multi-chamber air bag to pass through the first gap, the top end of the longitudinal plate and the second gap, flattening the non-expansion part along the transverse plate direction, and uniformly distributing the multi-chamber air bag on one side of the longitudinal plate.

Fig. 2a is a three-dimensional view of a shrinkage magnification mechanism. The frame structure is I-shaped as shown in the figure, and four openings 4 are arranged at the bottom of the I-shape and can penetrate through the metal rod 3. As shown in the top view of fig. 2b, there is a gap between the metal rod and the frame, which can pass through the airbag 1.

In the above technical solution, the two ends of the non-inflatable part of the multi-chamber airbag may be connected with the acting object. When the structure is inflated, the multi-cavity expands and contracts, and the multi-cavity and the vertical plate act, so that the non-expansion part contracts along the transverse plate direction to generate force action outwards. When the inflation is not carried out, the non-expansion part is pulled by external force to restore the initial state.

In the above technical solution, the shrinkage amplification mechanism is i-shaped and can be manufactured by additive or subtractive materials, such as 3D printing, CNC, wire cutting, injection molding, and the like.

FIG. 3a illustrates a method of making a multi-chamber airbag. The bonded portions 5 are bonded together by an adhesive or thermocompression, and the unbonded portions 6 form an air cell and an air passage that allows air to flow to inflate the air cell. Fig. 1a is a photograph of a typical balloon, before and after inflation. The shrinkage after expansion was 36%.

Figure 3b illustrates a method of mounting the airbag into the frame. The air bag is sequentially passed through the first gap, the top end of the frame and the second gap, the non-combined part of the air bag is aligned with the side surface of the vertical plate of the frame, and then the two ends of the air bag are tightened.

Because the shrinkage amplifying mechanism places the inflatable and contractible air bag on one side of the longitudinal plate, the other side of the transverse plate is always a plane, and the plane can be used for contacting with the skin and does not generate extrusion on the skin caused by expansion. Because the acting direction is the transverse plate direction, the longitudinal plates limit the retractable air bags far beyond the transverse plate in the non-acting direction, and therefore the shrinkage rate in the transverse plate direction can be greatly improved.

Fig. 4a-4c illustrate the driving principle of pneumatic muscles. Fig. 4a shows the initial state, when the lower part is longest. When the air bag is inflated when external air enters through the air passage, the air bag contracts itself on the one hand and interacts with the vertical portion of the frame on the other hand, tilting the air bag, as shown in fig. 4b, pulling the lower coupling portion 6 to shorten the total length. Fig. 4c shows the limit of contraction when the bladder is in contact with the latter frame, which is 50% contraction.

The electrodes are respectively attached to the surfaces of the longitudinal plate of the frame, which are in contact with the air bag, the two layers of electrodes are led out by using a lead, and the capacitance-to-voltage module is connected, so that the voltage and the displacement of the whole pneumatic artificial muscle are in a direct proportion relation, and the voltage can linearly represent the displacement of the artificial muscle, and self-sensing is completed.

Fig. 5a-5c are muscle diagrams of an incremental capacitive displacement sensor. Electrode pads 7 (such as copper electrode pads) are respectively attached to the contact surfaces of the frame 2 and the airbag 1, and an insulating layer is coated on one of the electrode pads, so that the capacitive sensor is formed. The capacitance of this capacitive sensor is linear with the contraction length of the muscle. And reading the voltage by using a capacitance-to-voltage module. Therefore, the sensor can be used as a displacement sensor of muscles.

The self-sensing bag type pneumatic artificial muscle based on the shrinkage amplification mechanism provided by the invention is based on the shrinkage amplification mechanism, so that the shrinkage of the positive pressure artificial muscle is greatly improved; one surface in the acting direction is a plane, and the inflatable air bag cannot expand due to inflation, can be used by being attached to the skin, and cannot extrude the skin; the flexible module is distributed and arranged by the modules, has flexibility, and can be used by being attached to surfaces with different curvatures; the initial cavity of the pneumatic muscle is small in size, and the response speed is increased; the pneumatic muscle has self-sensing property and can feed back displacement, so that the whole control system is further compact.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The self-sensing bag type pneumatic artificial muscle based on the shrinkage amplification mechanism is characterized by comprising a rectangular flat multi-chamber air bag and the shrinkage amplification mechanism matched with the multi-chamber air bag, wherein the shrinkage amplification mechanism comprises an I-shaped frame formed by connecting two transverse plates and a longitudinal plate and two metal columns arranged between the two transverse plates, the two metal columns are symmetrically arranged at two sides of the longitudinal plate, and a first gap and a second gap are respectively formed between the longitudinal plates; the multi-chamber air bag sequentially penetrates through the first gap, the top end of the longitudinal plate and the second gap to be connected with the frame, and air bag chambers are uniformly distributed on one side of the longitudinal plate; and a displacement sensor for feeding back the displacement of the artificial muscle is arranged between the frame and the multi-chamber air bag.

2. The self-sensing bag-type pneumatic artificial muscle based on the contraction rate amplification mechanism according to claim 1, wherein the multi-chamber air bag comprises a joint portion and a non-joint portion, the non-joint portion forms the air bag and the air passage which are communicated, and a joint portion is arranged between two adjacent air bags.

3. The self-sensing bag type pneumatic artificial muscle based on the shrinkage amplification mechanism according to claim 1, wherein the displacement sensor comprises electrode plates respectively arranged on contact surfaces of the frame and the multi-chamber air bag, an insulating layer is coated on one electrode plate to form a capacitance sensor, and the capacitance sensor is connected with a capacitance voltage conversion module through a lead to form the displacement sensor.

4. The self-sensing bag-type pneumatic artificial muscle based on the contraction rate amplification mechanism according to claim 2, wherein the transverse plate is provided with a hole for installing the metal column.

5. The self-sensing bag-type pneumatic artificial muscle based on the shrinkage amplification mechanism of claim 1, wherein the transverse plates are triangular plates and are arranged in an axisymmetric manner with respect to the longitudinal plates.