CN116460835A - Air-wire Hybrid Soft Actuator with Variable Stiffness Based on Fiber Blockage - Google Patents

Abstract

The present invention is a variable stiffness air-wire hybrid soft driver based on fiber blocking, which includes a variable stiffness part and a driving part. The variable stiffness part is located at the upper end of the driving part. The variable stiffness part realizes the stiffness change of the driver through fiber blocking, and the driving part realizes the bending of the driver through wire rope driving. The variable stiffness part includes an outer tube, a fiber blocking layer and an inner tube. The fiber blocking layer is located between the outer tube and the inner tube. The fiber blocking layer includes a large fiber layer and a small fiber layer. The fiber rotation of the fiber layer is opposite, and the gap between two adjacent large fiber layers is filled with two small fiber layers, and the fiber rotation of each small fiber layer is the same as that of the adjacent large fiber layer. The driver has the advantages of variable stiffness, controllable bending deformation, large output force, and fast response.

Description

Air-wire Hybrid Soft Actuator with Variable Stiffness Based on Fiber Blockage

technical field

The invention belongs to the technical field of soft robots, and in particular relates to a variable-stiffness air-line hybrid-driven soft driver based on fiber blockage, which has broad application prospects in the fields of exploration and rescue, object grasping, etc., and is suitable for grasping objects with complex shapes, soft surfaces, and easy damage, and can also be used for bending and stiffness changes of soft robotic arms.

Background technique

As robots become more and more widely used and play an increasingly important role in people's production and life, some special occasions put forward higher requirements for the flexibility and compliance of robot structures, which also makes traditional rigid robots unsuitable for some special occasions, such as: exploration and rescue, grasping of soft objects, etc. With the continuous development of materials, combined with the relevant knowledge of bionics, the concept of a new type of soft robot based on soft materials has been gradually proposed.

Soft robots are mainly made of soft functional materials. Because of their various degrees of freedom of movement and good environmental adaptability, they have great application prospects in exploration, rescue and grasping of soft objects. However, due to the low stiffness of soft robots, their carrying capacity and output force are greatly limited, making it difficult to complete operations under load, and accompanied by great motion uncertainty. Therefore, more and more scientific research institutions have begun to conduct research on the technology of variable stiffness of soft robots.

The existing variable stiffness technology of soft robots mainly includes: electrostatic adsorption variable stiffness technology, electrostatic layer density variable stiffness technology, PVC gel stool stiffness technology, origami variable stiffness technology, minimum potential energy variable stiffness technology, magnetic/electrorheological variable stiffness technology, active/semi-active antagonism mechanism variable stiffness technology, and blockage variable stiffness technology. The above-mentioned variable stiffness technologies for soft robots, such as electrostatic adsorption and electrostatic layer density, need to be connected to a kilovolt-level working voltage, and residual static electricity will be generated during work, which is not suitable for practical applications; PVC gel itself has relatively high stiffness, which will be limited in some soft structures; although origami technology and minimum potential energy technology have better effects in variable stiffness, they are still in the experimental stage, and their application in actual production and life needs to be studied. , and the yield rate in the actual production process is low; the active/semi-active antagonism technology and the blockage variable stiffness technology have good flexibility and safety, and are suitable for application in actual production and life. The University of Salford in the United Kingdom has used semi-active antagonism mechanism variable stiffness technology to produce multiple drive units. Although the response is fast and the flexibility is good, the degree of freedom is too large and difficult to control. The State Key Laboratory of Fluid Power and Electromechanical Systems of Zhejiang University has used plugging and variable stiffness technology to produce a soft actuator. By filling the interior with particles, the friction between the particles will be significantly increased under the action of external pressure, so as to achieve the purpose of variable stiffness. However, particle filling will increase the weight of the soft actuator. After being damaged by shearing, the fine particles will easily leak and cause the actuator to fail to work normally.

The driving methods of the existing soft actuators include wire rope driving, air pressure driving, shape memory material driving, electroactive polymer driving, magnetic driving, responsive gel driving, chemical driving, biological driving, and hybrid driving. Although each driving method has its own advantages and disadvantages, the most commonly used driving methods are pneumatic driving and wire driving. Both of these driving methods can provide large driving force, precise control, easy access to driving materials, non-toxic and harmless, simple structure, and low cost. They are suitable for soft robotic arms, exploration and rescue, medical surgery, object grasping, and bionic sports. With the continuous research on software drivers, in order to minimize the disadvantages caused by a certain driving method, a new type of driving method, that is, hybrid driving, has emerged. The biggest advantage of this driving method is that it can complement each other by combining a variety of different driving methods. The tiger beetle larva multi-drive soft robot developed by Soochow University adopts SMA spring drive in the head to realize the bite movement, and the air pressure drive in the tail to realize forward and turning movements.

Soft actuators that can be used in areas such as exploration, rescue, and object grasping need to meet two basic functions. First, they can perform controllable bending deformation at a lower stiffness state, and second, they can stabilize shape and load work at a higher stiffness state.

Contents of the invention

Aiming at the deficiencies of the existing technology, the technical problem to be solved by the present invention is to provide a variable stiffness air-wire hybrid soft actuator based on fiber blocking, which has the advantages of variable stiffness, controllable bending deformation, large output force, and fast response speed.

The technical scheme that the present invention adopts to solve described technical problem is as follows:

A variable stiffness air-wire hybrid soft driver based on fiber blocking, characterized in that the driver includes a variable stiffness part and a driving part, the variable stiffness part is located at the upper end of the driving part, the variable stiffness part realizes the stiffness change of the driver through fiber blocking, and the driving part realizes the bending of the driver through wire rope driving;

The variable stiffness part includes an outer tube, a fiber blocking layer and an inner tube, and the fiber blocking layer is located between the outer tube and the inner tube; wherein, the fiber blocking layer includes a large fiber layer and a small fiber layer, and a plurality of large fiber layers are stacked together, the fibers of two adjacent large fiber layers have opposite directions of rotation, and the gap between two adjacent large fiber layers is filled with two small fiber layers, and the fiber rotation of each small fiber layer is the same as that of the adjacent large fiber layer.

Further, both the large fiber layer and the small fiber layer are formed by a plurality of fiber arrays with the same rotation direction and an angle of 30° with the horizontal direction, and there is a gap between two adjacent fibers, which is 1/5 of the fiber diameter of the small fiber layer.

Further, the outer tube and the inner tube are both silicone hoses.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The soft actuator designed by the present invention adopts the fiber blocking variable stiffness structure in the variable stiffness part. Compared with the traditional particle blocking variable stiffness soft actuator, the fiber blocking layer has the advantages of light weight, large stiffness variation range, and is not easy to damage and fail.

2. The soft actuator designed by the present invention has designed the arrangement and structure of the helical fibers in the fiber blocking layer. Compared with the traditional soft actuator in the past, this structure is beneficial to enhance the ability of the soft actuator to resist shear stress, and also has the ability to resist tensile fracture to a certain extent.

3. The soft actuator designed in the present invention, the designed driving structure includes wire rope driving and air pressure driving, and the bending deformation of the soft actuator is controlled through the wire rope driving, and the wire rope driving bending is more precise, controllable and responsive. The air pressure change of the fiber blocking layer is controlled by the air pressure, so that the radial compression is more uniform and controllable. Compared with the traditional single driver, the hybrid drive of wire rope and air pressure can better complement each other, making the driver more precise and controllable.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is a radial sectional view of the present invention;

Fig. 3 is the axial sectional view of variable stiffness part of the present invention;

Fig. 4 is the structural representation of the large fiber layer of the present invention;

Fig. 5 is the structural representation of the fibrous layer of the present invention;

Figure 6 is a radial cross-sectional view of the fiber blocking layer of the present invention;

Fig. 7 is a structural schematic diagram of the driving part of the present invention;

Reference signs are: 1. upper end cover; 2. variable stiffness part; 3. driving part; 4. outer tube; 5. fiber blocking layer; 6. inner tube; 7. large fiber layer; 8. small fiber layer; 9. pneumatic valve; 10. notch.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The air-wire hybrid soft driver with variable stiffness based on fiber blocking of the present invention comprises an upper end cover 1, a variable stiffness part 2 and a driving part 3; the upper end cover 1 is at the upper end of the variable stiffness part 2, and the variable stiffness part 2 is located at the upper end of the driving part 3, and fiber blocking is used to realize the stiffness change of the driver; the driving part 3 realizes bending of the driver through wire rope driving.

The variable stiffness part 2 is composed of an outer tube 4, a fiber blocking layer 5 and an inner tube 6, and the fiber blocking layer 5 is located between the outer tube 4 and the inner tube 6; the outer tube 4 and the inner tube 6 are silicone hoses cast by molds, which can be bent and folded at any angle; the fiber blocking layer 5 includes four large fiber layers 7 and six small fiber layers 8, and each large fiber layer is composed of 45 nylon fibers with the same direction of rotation and a horizontal angle of 30° with rough surfaces, but two adjacent large fiber layers 7 The fiber rotation is opposite, and two small fiber layers 8 are filled in the gap between each adjacent two large fiber layers 7; each small fiber layer 8 is also composed of 45 nylon fibers with the same rotation direction and a horizontal angle of 30° with a rough surface, and its wire diameter is about 1/4 of the large fiber diameter. In addition, there is a gap between every two adjacent fibers, the gap is about 1/5 of the diameter of the small fiber, so that in the initial state, no large friction force will be generated between the fibers, and a certain degree of rigidity support can be provided, thereby ensuring that the initial stiffness of the software driver is low, and a large range of bending deformation can occur at a low stiffness. In addition, when the fiber blocking layer is vacuumed, the fiber blocking layer 5 can be radially shrunk, so that the fibers are squeezed each other and generate a large friction force, and then produce a large stiffness change. In the case of rigidity, the soft actuator is not easy to bend and deform, and maintains the desired bending shape to perform subsequent work. Let each helical fiber have an angle of 30° with the horizontal direction, and each layer of fibers is composed of 45 helical fibers, and the adjacent large fiber layer 7 has the opposite direction of rotation, and the small fiber layer 8 has the same direction of rotation as the nearest large fiber layer 7, and the direction of rotation of the nearest small fiber layer is opposite. It has a certain deformation ability when it is stretched and deformed, and it will not be easily destroyed by a large stretching force.

The drive layer part 3 consists of four pneumatic valves 9 and four slots 10 for mounting drive wires. The pneumatic valve 9 is externally connected to a vacuum pump, and the fiber blocking layer 5 is vacuum-pumped through the vacuum pump. The design of four pneumatic valves 9 can make the force applied to the fiber blocking layer 5 more uniform, so that the inner tube 6 and the outer tube 4 can evenly compress the fiber blocking layer 5, so that each fiber layer can be evenly stressed and squeezed evenly, and avoid bending and deformation of the software driver due to air pressure deviation during vacuum extraction. Install the driving wires on the soft driver through four notches 10 for installing the driving wires. The driving wires can be controlled by an external motor, and each wire can pull the software driver to bend in one direction. The four wires can be evenly distributed and used in conjunction with each other to make the soft driver perform 360° bending deformation. The four pneumatic valves are evenly distributed at 90° apart on the annular surface of the lower end cap corresponding to the fiber blocking layer, and the four channels for installing the driving wires are evenly distributed at 90° on the annular surface of the lower end cap corresponding to the outermost layer.

Both the outer tube 4 and the inner tube 6 are flexible tubes made of silica gel, which can be bent and deformed with multiple degrees of freedom. The fibers filled in the fiber blocking layer 5 are all composed of nylon helical fibers with rough surfaces, and there are certain gaps between the fibers in the initial state, which can ensure that the soft actuator has a certain ability to bend and deform under the initial low stiffness, and has a certain supporting stiffness to ensure the controllability of the actuator itself. When vacuuming the fiber blocking layer, the inner tube and the outer tube will radially squeeze the fiber blocking layer, causing the fibers in the fiber blocking layer to be radially squeezed. At this time, there is no gap between the fibers, and the mutual extrusion between the fibers generates a large friction force, thereby improving the overall stiffness of the software driver.

If multiple software drivers of the invention are used to grab an object, the motor can be used to control the wire rope to cause the driver to bend and deform. After reaching the expected deformation, vacuum pumping can be performed by a vacuum pump, so that the rigidity of the driver can be greatly improved. When the rigidity reaches the maximum, the load capacity of the driver itself reaches the maximum and the deformation capacity reaches the minimum, thereby achieving stable grasping of the grasped object.

What is not mentioned in the present invention is applicable to the prior art.

Claims (3)

1. The variable-rigidity air line hybrid soft driver based on fiber blockage is characterized by comprising a variable-rigidity part and a driving part, wherein the variable-rigidity part is positioned at the upper end of the driving part, the variable-rigidity part realizes the rigidity change of the driver through fiber blockage, and the driving part realizes the bending of the driver through the driving of a rope;

the rigidity-changing part comprises an outer layer pipe, a fiber blocking layer and an inner layer pipe, and the fiber blocking layer is positioned between the outer layer pipe and the inner layer pipe; the fiber blocking layer comprises a large fiber layer and a small fiber layer, a plurality of large fiber layers are stacked together, the fiber rotation directions of two adjacent large fiber layers are opposite, two small fiber layers are filled in gaps between two adjacent large fiber layers, and the fiber rotation direction of each small fiber layer is the same as that of the adjacent large fiber layer.

2. The variable stiffness air line hybrid software driver based on fiber blockage according to claim 1, wherein the large fiber layer and the small fiber layer are formed by a plurality of fiber arrays which are in the same rotation direction and form an included angle of 30 degrees with the horizontal direction, and a gap is formed between every two adjacent fibers, and is 1/5 of the fiber diameter of the small fiber layer.

3. The fiber blockage based variable stiffness gas line hybrid software driver of claim 1 or 2, wherein the outer and inner layers are silicone hoses.