CN201098219Y - A Multi-DOF Intelligent Pneumatic Muscle Based on Shape Memory Alloy Deformable Mesh - Google Patents

Abstract

The utility model discloses a multi-degree-of-freedom intelligent pneumatic muscle based on a shape memory alloy deformation net. A deformed net composed of bending guide alloy springs, rotation guide alloy springs and shape memory alloy braided nets is installed tightly and axially on the outside of the elastic rubber tube, and the two ends of the elastic rubber tube are sealed with outer clamps and internal components. When the rubber inner tube is expanded by air pressure, the deformable net is based on passive deformation, adding active deformation to constrain the deformation of the aerodynamic muscle, so as to realize the characteristics of adjustable characteristics and multiple degrees of freedom. The shape memory alloy smart material is heated by a pulsed current to actively generate deformation. Bend-guided and helically-rotated-guided shape memory alloy springs enable the bending and rotation of the pneumatic muscle. The positive effect of the utility model is reflected in that the driving characteristic of the pneumatic muscle is improved, the degree of freedom of the pneumatic muscle is increased, and the utility model can be used in fields requiring high precision, flexibility and complicated driving. The pneumatic muscle of the utility model can be directly connected to the load, and can also be connected to the load through a transmission mechanism.

Description

A Multi-DOF Intelligent Pneumatic Muscle Based on Shape Memory Alloy Deformable Mesh

technical field

The utility model relates to pneumatic muscle technology and shape-memory alloy materials, in particular, the shape-memory alloy is used to make a deformable mesh with a special structure that can be actively deformed.

Background technique

Pneumatic muscles were first proposed by Russian inventor S.Garasiev in the 1930s. American doctor Mckibben invented a working pneumatic muscle in the 1950s. In the 1980s, Japanese engineers developed the Rubbertuator pneumatic muscle based on the Mckibben pneumatic muscle. British engineers developed the Air Muscle pneumatic muscle based on the Mckibben pneumatic muscle. Pneumatic muscle is a revolution in pneumatic technology, and it is also an important development direction of intelligent drives. The pneumatic muscle is mainly composed of an inflatable elastic hose and an external load-bearing component that constrains the expansion and deformation of the elastic tube. The stress is generated due to the deformation being restrained by the external load-bearing component.

The advantages of pneumatic muscles are high power-to-weight ratio, no pollution, no sliding, compliance with human or animal muscles, and easy miniaturization, which has a good application prospect. The earliest Mckibben pneumatic muscles were used as motion actuation devices for assisting disabled fingers. Pneumatic muscles are also used in the industrial field, especially industrial manipulators and robots, as an efficient driver that can generate sufficient force while maintaining a certain degree of compliance, making the driven device "environmentally friendly", Perform tasks such as nursing patients, grasping fragile objects, and more.

Pneumatic muscles can be divided into woven mesh type, mesh type, embedded and special structure pneumatic muscles according to the structure. The braided mesh pneumatic muscle uses a fiber braided mesh to constrain the deformation of the airtight elastic tube. The mesh-type pneumatic muscle adopts a woven net with relatively large mesh and sparse fibers. Embedded artificial muscles load-bearing silk, fiber components are embedded in elastic membranes. The above-mentioned pneumatic muscles can only produce axial telescopic movements, and a single pneumatic muscle can only produce one kind of movement, that is, only one degree of freedom (the number of free movement directions). The special structure pneumatic muscle is essentially to combine multiple pneumatic muscles according to a certain structure, which can obtain complex movements and multiple degrees of freedom. The principles of the existing pneumatic muscle mechanisms are similar. The movement of the pressurized trachea (sac) is restricted by a mesh member. The mesh member only deforms passively, and the deformation is mainly reflected in the passive change of the angle between the wire and the muscle axis. The main disadvantages and deficiencies of current pneumatic muscles are as follows:

First of all, the driving characteristics of existing aerodynamic muscles are fixed, and the static and dynamic characteristics such as length-load characteristics, shrinkage rate, output per unit cross-sectional area, and stiffness changes cannot be adjusted according to changes in the driving load. This leads to different load-driving tasks requiring the design of aerodynamic muscles with different characteristics. The biological muscle characteristics of the human body can be adjusted and changed. The constrained deformation of the mesh member is a key factor determining the actuation characteristics of the aerodynamic muscle.

Second, a single pneumatic muscle has only one driving action capability, which is not suitable for fields that require complex driving actions. In an existing three-degree-of-freedom pneumatic muscle, the trachea is equally divided into three independent fan-shaped columnar cavities. The air pressure of the three cavities should be adjusted separately, so it is essentially a combination of three pneumatic muscles. Combining multiple pneumatic muscles to realize complex driving actions will lead to complex pneumatic muscle mechanisms, large volume, and the need to adjust the air pressure of multiple cavities, resulting in high cost.

These two deficiencies are the key issues affecting the development and application of pneumatic muscles. Solving these two deficiencies will improve the performance of aerodynamic muscles and promote the application of aerodynamic muscles in the field of high-precision and compliant driving, thereby promoting the development of manufacturing and bionic robots.

Shape memory alloy is a kind of intelligent material that utilizes the shape memory effect and can change its shape through temperature changes. It is the earliest driving element used in intelligent structures. Shape memory alloys can be made into various shapes such as coil springs, filaments, torsion springs, thin sheets, and butterflies. They are characterized by large bending capacity, high plasticity, shape recovery above the memory temperature, simple structure, and no noise. They are widely used. In the fields of artificial bones, satellite antennas, dental orthodontics, pipeline connection parts, brakes, and small humanoid robot drives.

According to the working principle of pneumatic muscles, it should be possible to improve the characteristics of pneumatic muscles by actively adjusting the angle between the wires in the constraining mesh and the muscle axis; it is possible to constrain a single tracheal pneumatic muscle with meshes that actively deform in multiple directions deformation, so as to realize multi-degree-of-freedom complex movements. Although the action frequency of shape memory alloys is not very high, the frequency of muscle-driven actions is not high. Therefore, introducing the controllable active deformation characteristics of shape memory alloy materials into the mesh components of aerodynamic muscles will result in innovative technologies and products.

Contents of the invention

The purpose of this utility model is to provide a multi-degree-of-freedom intelligent pneumatic muscle based on a shape memory alloy deformation net, which can be adjusted according to load changes, and can perform multiple degrees of freedom such as stretching, bending, and rotation, and its driving characteristics can be adjusted. An intelligent pneumatic muscle actuator that adjusts to changes in load.

In order to achieve the above-mentioned purpose of the invention, the technical scheme that the utility model adopts is as follows:

Bending guiding alloy springs, rotating guiding alloy springs and shape memory alloy braided nets are installed tightly and axially outwardly on the elastic rubber tube; one end of the elastic rubber tube is sequentially equipped with an outer clamp for front-end sealing, an inner member for front-end sealing and Front-end connecting piece; the other end of the elastic rubber tube is equipped with an outer clamp for back-end sealing, an inner member for back-end sealing and a back-end connecting piece; the inner member for front-end sealing is provided with a gas inlet and outlet, and the trachea connector and the wiring port are respectively installed on the inner member for front-end sealing; one end of the air pipe is connected to the elastic rubber pipe through the air pipe connector, and the other end of the air pipe is connected to the external clean air pressure source A through the external air pipe connection port; one end of the electric wire is connected to the current C , the other end of the electric wire is respectively connected with the shape memory alloy braided mesh, the axially installed bending guide alloy spring and the rotation guide alloy spring through the connection port.

There are four axially installed bending guide alloy springs, which are installed in pairs in radial direction with axial grooves on the outer wall of the rubber inner tube, and different currents are passed through.

The said rotation guiding alloy spring is installed with a spiral groove on the outer wall of the rubber inner tube.

The beneficial effect that the utility model has is:

The driving characteristic of the pneumatic muscle of the utility model can be adjusted through the active deformation of the shape memory alloy deformation net, so that it can adapt to different driving load requirements and has intelligence. At the same time, because the deformation net adopts a special structure with deformation-guiding alloy springs, the aerodynamic muscles can use a single trachea and a single air pressure source to realize the driving action of multiple degrees of freedom such as bending, rotation, and expansion. The positive effect of the utility model is reflected in that the driving characteristic of the pneumatic muscle is improved, the degree of freedom of the pneumatic muscle is increased, and the utility model can be used in fields requiring high precision, flexibility and complicated driving. The pneumatic muscle of the utility model can be directly connected to the load, and can also be connected to the load through a transmission mechanism.

Description of drawings

Fig. 1 is a schematic diagram of the structural principle of the utility model pneumatic muscle.

Fig. 2 is a B-B sectional view of Fig. 1 .

In the figure: 1. Shape memory alloy woven mesh; 2. Bending guide alloy spring; 3. Rotation guide alloy spring; 4. Elastic rubber inner tube; 5. Gas inlet and outlet; 6. Trachea connector; 7. Trachea; 8. Front-end connector; 9. External gas pipe connection port; 10. Wiring port; 11. Electric wire; 12. Internal member for front-end sealing; 13. External clamp for front-end sealing; 14. External clamp for rear-end sealing; 15. Internal member for back-end sealing; 16, back-end connector; A, gas; C, electric current.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

The pneumatic muscle driver of the utility model comprises: a rubber elastic inner tube, an actively deformable deformation net attached to the outer wall of the inner tube, air inlet and outlet ports for air supply of the trachea, and seals at the front and rear ends for precise connection of the trachea and the deformation net. Clamps, as well as wiring ports, air pipes, electric wires, etc. The specific technology lies in:

A. Using the principle that the deformation of the rubber inner tube is constrained by the external deformable mesh that can be actively deformed, the aerodynamic muscle driving characteristics and the deformation direction can be adjusted. The deformation net adopts a special structure, which is composed of a shape memory alloy wire braided net and a deformation guiding alloy spring, wherein the deformation guiding alloy spring is composed of a bending guiding alloy spring and a rotation guiding alloy spring. The deformation mesh structure is tightly wound and sheathed on the outer wall of the rubber elastic inner tube to constrain the deformation of the inner tube.

B. By applying different PWM pulse currents to the shape memory alloy wire for heating and natural cooling, the temperature of the alloy wire is changed, resulting in a change in the length of the alloy wire, so that the structure of the braided mesh can be changed under the control of pulse current heating to realize braiding The active deformation of the net enables the intelligence of the pneumatic muscles. During the deformation process, the alloy wire length and mesh surface area will actively change.

C. In order to realize bending deformation with the pneumatic muscle with a single air cavity, the utility model is designed and distributed with multiple pairs of shape memory alloy springs with bending deformation guiding function along the axial direction of the braided mesh in the inner wall of the braided mesh. Pairs of bend-guiding alloy springs are mounted symmetrically and deform in opposite directions, thus allowing the pneumatic muscle to bend and deform. Grooves are installed on the outer wall of the rubber inner tube to install curved guiding alloy springs. The bending deformation direction and number of the pneumatic muscle of the utility model are determined by the position and number of the symmetrically installed bending guide alloy springs.

D. In order to use the pneumatic muscle with a single air cavity to achieve rotational deformation, the utility model designs a rotational guide alloy spring, which is spirally wound on the outer wall of the rubber inner tube, and is slotted on the outer wall of the rubber inner tube to install the rotational guide alloy spring. The rotation and deformation direction of the pneumatic muscle of the utility model is determined by the helical direction when the rotation guide alloy spring is installed.

E. The seal at both ends of the pneumatic muscle is composed of an inner member and an outer clamp designed for coaxial screw clamping. Put the rubber inner tube of the pneumatic muscle and the two ends of the deformable mesh on the inner member, tighten the outer clamp and the inner member and apply sealant, so as to conveniently realize the sealing of the two ends of the pneumatic muscle. The internal component for sealing the front end is designed with a gas inlet and outlet and a shape memory alloy heating current connection port.

The characteristics and deformation adjustment method of the intelligent pneumatic muscle of the utility model include:

A. The method of adjusting the driving characteristics of pneumatic muscles is mainly aimed at the adjustment of two characteristics: expansion ratio and variable stiffness.

a. Stretching rate refers to the ratio of the maximum stretching deformation of the pneumatic muscle to the original length. Under the condition of constant air pressure, the amount of stretching and deformation of the pneumatic muscle depends on the angle of the braided mesh, and the angle of the braided mesh is related to the length of the braided mesh. By heating and deforming the shape memory alloy wire, changing the length of the wire, the angle of the braided mesh can be changed, thereby adjusting the stretching deformation of the pneumatic muscle, and then adjusting the stretching rate. Pneumatic muscles with different stretching ratios can be used for different motion driving requirements, so that the utility model's pneumatic muscles can be applied to different driving requirements.

b. The stiffness of biological muscles can vary with tension and load. The characteristic of variable stiffness makes the movement of joints composed of muscles very flexible. In the movement of a joint, both position control and force control can be realized. The stiffness of the pneumatic muscle varies as a function of inflation pressure and length. However, the length of traditional aerodynamic muscles remains constant under constant inflation pressure, so the variable stiffness characteristics of traditional aerodynamic muscles cannot be adjusted according to different driving tasks. The utility model can change the length of the aerodynamic muscle through the active deformation of the shape memory alloy braided net under a certain inflation pressure, and can also constrain the trachea through the active deformation of the shape memory alloy braided net under the condition that the length of the aerodynamic muscle remains unchanged. Inflatable pressure inside, so as to realize the flexible adjustment of stiffness.

B. Implementation method of different degrees of freedom driving action. By applying different currents to the bending-guiding alloy springs installed in pairs in specific directions, the opposite active deformation is caused, resulting in the bending deformation of the aerodynamic muscle, while other bending-guiding alloy springs do not apply current and only passively deform. By applying different currents to a helically mounted rotation-guiding alloy spring, active deformation of the alloy spring is induced, resulting in rotational deformation of the pneumatic muscle.

As shown in Fig. 1 and Fig. 2, the utility model installs bending guide alloy spring 2, rotation guide alloy spring 3 and shape memory alloy braided mesh 1 tightly and axially outwards in the elastic rubber tube 4 in sequence; one end of the elastic rubber tube 4 faces Outer clamp 13 for front-end sealing, inner member 12 for front-end sealing and front-end connecting piece 8 are installed in sequence; the other end of elastic rubber tube 4 is equipped with outer clamp 14 for rear-end sealing and inner member 14 for rear-end sealing. The component 15 and the rear end connector 16; the inner member 12 for front-end sealing is provided with a gas inlet and outlet 5, and the trachea connector 6 and the wiring port 10 are respectively installed on the inner member 12 for front-end sealing; one end of the air pipe 7 passes through the trachea connector 6 communicates with the elastic rubber tube 4, and the other end of the trachea 7 is connected to the external clean air pressure source A through the external trachea connection port 9; one end of the electric wire 11 passes a current C, and the other end of the electric wire 11 passes through the wiring port, respectively connected to the shape memory The alloy braided mesh 1, the axially installed bending guide alloy spring 2 and the rotation guide alloy spring 3 are connected.

There are four axially installed bending guide alloy springs 2, which are installed in pairs with axial grooves on the outer wall of the rubber inner tube, evenly distributed in the radial direction, and connected with PWM pulse current. The paired two guide alloy springs must pass through different PWM pulse currents to produce different length deformations, so that the pneumatic muscles can be bent and deformed.

The rotation-guiding alloy spring 3 is installed in a spiral groove on the outer wall of the rubber inner tube, and when different PWM pulse currents pass through, the alloy spring produces different degrees of rotation deformation.

Device embodiment of the present utility model:

A high-elastic rubber tube with an outer diameter of Φ24mm, an inner diameter of Φ20mm, a length of 120mm, and a maximum pressure resistance of 0.5MPa is selected as the inner tube of the pneumatic muscle.

The braided mesh adopts the Ti-Ni series shape memory alloy material that has been put into practical use at present, which has the advantages of large recovery force during recovery deformation, large deformation recovery, high resistivity, long fatigue life, high energy density, and corrosion resistance of the material. The weaving of the woven net adopts the twist net weaving method. The shape-memory alloy wire used for the braided net adopts an alloy wire with a diameter of 0.2mm, a length of 600mm, a maximum expansion and contraction of 50mm, and a maximum tensile stress of 100N. The deformation guiding alloy spring is closely connected with the inner wall of the braided mesh.

Design and install 4 bending guide alloy springs, choose Ti-Ni alloy coil springs, wire diameter 250μm, diameter 4mm, length 120mm. 4 bending guide alloy springs are evenly distributed on the outer wall of the rubber inner tube, which can make the pneumatic muscle bend and deform around two axes. Axial linear grooves are machined on the outer wall of the rubber inner tube for the installation and rotation of the bending guide alloy spring.

Design and install a single rotary guide alloy spring, choose Ti-Ni alloy coil spring, wire diameter 400μm, diameter 4mm, length 300mm. A spiral groove is machined on the outer wall of the rubber inner tube for the installation of the rotating guide alloy spring.

The installation of the deformed net should be prestressed to ensure the close contact between the deformed net and the rubber inner tube.

The PWM pulse current is used to heat the shape memory alloy and cool down naturally, the heating time is less than 0.7s, and the cooling time is less than 1.3s. The selected shape memory alloy wire has a heating deformation temperature of 70°C and a cooling temperature of 40°C. In order to reduce the influence of the alloy wire temperature on the rubber tube, heat insulating glue is sprayed on the outer wall of the rubber tube.

The magnitude of the pulling force produced by the pneumatic muscle is affected by the friction factor between the deformable mesh and the rubber inner tube and the deformation of the rubber hose. In order to reduce the friction between the braided mesh and the rubber inner tube, a small amount of lubricant should be applied to the outer wall of the rubber inner tube during assembly.

The sealing element is machined from aluminum alloy material. Trachea 7 adopts nylon tube. The electric wire 11 adopts a copper core wire with a diameter of 1 mm. The gas inlet and outlet 5 are designed in the inner member 12 of the front end clamp, and the wiring port 10 is installed on the inner member 12 of the front end clamp.

When assembling, first apply heat-insulating glue and lubricant on the rubber inner tube, and then wrap the fabricated deformed mesh including 1, 2 and 3 on the outer wall of the rubber inner tube 4. Insert the seal clamp inner members 12 and 15 into both ends of the rubber inner tube. Clamp the outer clamps for sealing to both ends of the rubber inner tube to ensure the seal. The front and rear end connectors 8 and 16 are welded to the inner members 12 and 15 respectively. The gas tube 7 is connected with the gas inlet 5 by the gas tube connector 6 . Connect the wire 11 to the terminal 10.

The overall weight of this device embodiment can be controlled at about 0.5kg, the maximum output force can be 800N, and the maximum load can be 50kg. The number of terminals in the wiring port is 6, one is used to connect the woven mesh, one is used to connect the rotating guide alloy spring, and 4 are used to connect the bending guide alloy spring. The end point of the pneumatic muscle can output 40mm linear displacement and 10mm bending displacement.

The use method step embodiment of the present utility model:

Take the humanoid robot elbow joint driver as an example. Pneumatic muscles can only provide one-way driving force, so using the bio-antagonist method, two pneumatic muscles are installed against the two sides of the revolving joint to drive the revolving joint. How to use steps:

A. Choose a suitable air pressure regulating device and a shape memory alloy heating current control circuit.

B. Install the pneumatic muscle of the utility model on the inner and outer sides of the elbow joint of the robot through the connecting members 8 and 16 at the front and rear ends.

C. Connect the air pipe 7 to an external clean air pressure source through the external air pipe connection port 9 .

D. Connect the deformation network with the external PWM pulse current C through the wiring port 10.

E. Apply the minimum pressure, which not only satisfies the gas to overcome the elasticity of the rubber tube, but also keeps the minimum pressure of the braided mesh and the rubber inner tube fully attached, which is about 0.05MPa.

F. Without applying current to the deformable mesh, gradually increase the inner tube air pressure of the unilateral pneumatic muscle to drive the rotation of the elbow joint.

G. In the case of constant air pressure, changing the load at the end of the elbow joint will reduce the accuracy of the position of the pneumatic muscle due to the change of the load. At this time, by adjusting the current of the braided mesh, the braided mesh is actively deformed to compensate for the decrease in position accuracy. When the load becomes larger, heat the shape memory alloy wire braided mesh, and the mesh will tighten. When the load decreases, the shape memory alloy wire braided mesh cools down and the mesh relaxes.

Since the above-mentioned embodiment is only used to drive the rotating joint, it does not embody the rotation and bending driving functions of the pneumatic muscle of the utility model. This pneumatic muscle can be used as a finger of a robotic dexterous hand. The front connecting part 8 is connected with the robot palm, and the rear connecting part 16 is connected with a small load. At this time, on the basis of the same method of use as above, by adjusting the PWM pulse current of the bending and rotation guide alloy spring, the flexible bending deformation driving action and rotating driving action similar to human fingers can be realized.

In use, the driving of large loads should be realized mainly through inflation air pressure, and the deformation of the deformable net plays an auxiliary driving function, improving driving precision, enriching driving actions, and improving driving performance.

After use, the PWM pulse current should be cut off first, and then the gas source should be cut off.

Claims (3)

1. A multi-degree-of-freedom intelligent pneumatic muscle based on shape-memory alloy deformable nets is characterized in that: a bending-guiding alloy spring (2) and a rotating-guiding alloy spring (3) are tightly axially installed outwards in the elastic rubber tube (4) ) and a shape memory alloy braided mesh (1); one end of the elastic rubber tube (4) is sequentially equipped with an outer clamp (13) for front-end sealing, an inner member (12) for front-end sealing and a front-end connector (8); The other end of the elastic rubber tube (4) is equipped with an outer clamp (14) for back-end sealing, an inner member (15) for back-end sealing and a rear-end connecting piece (16) outwards in sequence; an inner member (12) for front-end sealing ) is provided with a gas inlet and outlet (5), and the gas pipe connector (6) and wiring port (10) are respectively installed on the inner member (12) for front-end sealing; one end of the gas pipe (7) connects with the gas pipe connector (6) The elastic rubber tube (4) is connected, and the other end of the trachea (7) is connected to the external clean air pressure source A through the external trachea connection port (9); one end of the electric wire (11) is passed a current C, and the other end of the electric wire (11) is Through the wiring port, they are respectively connected with the shape memory alloy braided mesh (1), the axially installed bending guide alloy spring (2) and the rotation guide alloy spring (3). 2. A kind of multi-degree-of-freedom intelligent pneumatic muscle based on shape memory alloy deformation net according to claim 1, characterized in that: said axially installed bending guide alloy springs (2) are four, and the rubber inner tube Axial slots are opened on the outer wall and installed in pairs evenly distributed in the radial direction, and different currents are passed through. 3. A multi-degree-of-freedom intelligent pneumatic muscle based on a shape memory alloy deformation net according to claim 1, characterized in that: said rotation-guiding alloy spring (3) is installed in a spiral groove on the outer wall of the rubber inner tube.