Pneumatic layered damping type rigidity-variable soft manipulator

Abstract

The invention discloses a pneumatic layered damping type rigidity-variable soft manipulator, and relates to the technical field of soft manipulators. The finger part comprises a driving layer, a rigidity-variable layer and a fixed end, the driving layer is provided with a plurality of air bags, notches are formed between the tops of the adjacent air bags, cavities of the air bags are sequentially communicated through air channels, the rigidity-variable layer is integrally arranged at the bottom of the driving layer, upper and lower channels are formed in the rigidity-variable layer, and the fixed end is integrally arranged at the roots of the driving layer and the rigidity-variable layer; the first positive-pressure air supply hole channel is communicated with the cavity of the root air bag, the second positive-pressure air supply hole channel is communicated with the upper-layer channel, the insertion port and the lower-layer channel are the same in size and are communicated, and a filling sheet layer material is inserted into the insertion port. By means of the open type variable rigidity layer and the positive pressure pneumatic driving structure design, sheet layer materials can be conveniently replaced according to requirements, the change of rigidity is achieved by combining positive pressure adjustment, a damping mechanism of the variable rigidity layer is beneficial to effectively restraining vibration in the rapid deformation process of the mechanical arm, and the grabbing stability and precision are improved.

Description

Technical Field

[0001] The invention relates to the technical field of soft manipulators, in particular to a pneumatic layered damping variable-rigidity soft manipulator. Background Art

[0002] Traditional rigid manipulators have great limitations in handling and manipulating complex, irregular and fragile objects due to the inherent rigidity of their structures. In contrast, soft manipulators, with their softness, deformability and adaptability, can achieve more flexible operations and have become a key technology that has been widely studied and applied in recent years, showing great potential in various fields. Soft manipulators are usually made of flexible materials, and their movement and deformation are controlled by pneumatic, hydraulic or electro-driven methods. However, existing soft manipulators still face challenges in structural rigidity, response speed and operational stability, especially when grasping objects of different shapes and materials. It is difficult for existing soft manipulators to take into account both grasping force and protection of objects at the same time. In practical applications, soft manipulators often need to have different stiffness to adapt to different working scenarios and task requirements. Therefore, how to design a soft manipulator that can dynamically adjust stiffness has become an important direction of current research.

[0003] Domestic researchers have conducted different studies on the problems of existing soft manipulators. The Chinese invention patent with publication number CN118024294A discloses a soft manipulator with variable stiffness based on textile materials and its use method. This soft manipulator uses the variable stiffness structure of textile materials to have a large-scale grasping operation capability, but because it adopts the traditional negative pressure drive method, it will cause the flexibility and stiffness of the soft manipulator to be difficult to match, affecting the grasping effect; the Chinese invention patent with publication number CN113601542B discloses a soft manipulator with variable stiffness based on bionic adhesion. This soft manipulator adopts a positive pressure pneumatic drive method, which effectively solves the imbalance between flexibility and stiffness. However, because it adopts a closed variable stiffness structure design, it is difficult to conveniently adjust the stiffness of the soft manipulator, which will limit the design in some applications and has a high maintenance cost. Summary of the invention

[0004] In order to address the shortcomings of the background technology, the present invention provides a pneumatic layered damping variable stiffness soft manipulator, which, through an open variable stiffness layer and a positive pressure pneumatic drive structure design, can conveniently replace the sheet material according to needs and combine positive pressure adjustment to achieve stiffness changes. The damping mechanism of the variable stiffness layer helps the manipulator to effectively suppress vibration during rapid deformation and improve the stability and accuracy of grasping.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a pneumatic layered damping variable stiffness soft manipulator, comprising a mounting base and a finger part fixed thereon, the finger part comprising a driving layer, a variable stiffness layer and a fixed end, the driving layer is evenly provided with a plurality of airbags from the fingertip to the finger root, the plurality of airbags are designed to be rectangular, and a notch is provided between the tops of each two adjacent airbags so that there is a gap between the airbags, an airway is provided inside the driving layer to connect the chambers of all the airbags in sequence, the variable stiffness layer is arranged at the bottom of the driving layer and the two are made as one, and the variable stiffness layer is arranged along the inside An upper and lower layer of grooves which are connected with the finger root direction are arranged in the length direction, and the arrangement of the two layers of grooves makes the cross section of the variable stiffness layer present a sun shape. The fixed end is integrally arranged at the root of the driving layer and the variable stiffness layer, and is provided with a first positive pressure air supply channel, a second positive pressure air supply channel and an insertion port at the fixed end. The first positive pressure air supply channel is connected with the chamber of the airbag located at the root, and the second positive pressure air supply channel is connected with the groove of the upper layer of the variable stiffness layer. The insertion port has the same size as the groove of the lower layer of the variable stiffness layer and is connected, and the filling sheet material is inserted into the groove of the lower layer of the variable stiffness layer through the insertion port.

[0006] Furthermore, the airway is arranged at a height of 2 mm from the bottom of the airbag chamber, and the airway is a through hole structure with a diameter of Φ=2 mm.

[0007] Furthermore, the bottom of the variable stiffness layer is reinforced to prevent cracking by arranging a textile material layer.

[0008] Furthermore, the bottom of the notch arranged between the tops of the airbags is an arc-shaped structure.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. The present invention adopts an open variable stiffness layer. Compared with the traditional closed design, it is convenient to flexibly select the sheet material to be inserted and filled in the bottom groove of the variable stiffness layer according to specific application requirements. By adjusting the air pressure of the top groove of the variable stiffness layer, the pressure of the sheet material can be changed to adjust the stiffness of the soft manipulator, which greatly expands the stiffness adjustment range, ensures a larger bearing capacity, and makes the structure manufacturing and assembly simpler, maintenance and repair more convenient, and improves the adaptability and practicality of the soft manipulator;

[0011] 2. The variable stiffness layer of the present invention combined with the positive pressure adjustment of its top groove can change the friction generated by the sheet material inserted and filled in the bottom groove. This damping mechanism helps the manipulator to effectively suppress vibration during rapid deformation, improve the stability and accuracy of grasping, and provide a wider design space;

[0012] 3. The present invention adopts positive pressure regulation. In the full slip stage, the flexibility of positive pressure and negative pressure regulation is similar, but positive pressure can provide a larger stiffness adjustment range in the non-slip stage. Compared with the traditional negative pressure regulation method, the stiffness improvement effect of positive pressure regulation is more significant, which can be increased by up to about 3 times, effectively improving the system performance and being suitable for a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic cross-sectional view of the finger portion of the soft manipulator of the present invention;

[0014] Figure 2 is a schematic diagram of the overall appearance of the finger portion of the soft manipulator of the present invention;

[0015] Figure 3 It is a schematic diagram of the appearance of the driving layer of the finger part of the soft manipulator of the present invention;

[0016] Figure 4 Schematic diagram of the appearance of the variable stiffness layer of the finger part of the soft manipulator of the present invention;

[0017] Figure 5 is a schematic cross-sectional view of the fixed end of the finger portion of the soft manipulator of the present invention;

[0018] Figure 6 This is an example diagram of a configuration of the soft manipulator of the present invention.

[0019] In the figure: 1. driving layer; 2. variable stiffness layer; 3. chamber; 4. airway; 5. fixed end; 6. airbag. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] like Figure 1 to Figure 6 As shown, a pneumatic layered damping variable stiffness soft manipulator includes a mounting seat and a finger portion fixed thereon. Figure 1-2 As shown, the finger portion includes a driving layer 1, a variable stiffness layer 2 and a fixed end 5. Figure 6As shown, a configuration example is given, in which three finger parts are fixed on the mounting seat, and the grasping action is achieved through the bending deformation of the three finger parts. This configuration is only an example, and the grasping action can also be achieved by using other finger parts of more than two numbers, or even by fixing a rigid limit plate on the mounting seat to cooperate with one finger part, and the grasping action is achieved by clamping the object to be grasped and the rigid limit plate through the bending deformation of this finger part. Therefore, the number of finger parts does not limit the practical application of the soft manipulator of this scheme.

[0022] Combination Figure 1 , Figure 3 As shown, the driving layer 1 is a fast pneumatic network structure, which is evenly arranged with multiple airbags 6 from the fingertip to the finger root. The multiple airbags 6 are designed to be rectangular, and a notch is set between the tops of each two adjacent airbags 6 so that there is a gap between the airbags 6, with a certain gap and wall thickness to optimize the bending performance and aerodynamic efficiency. Figure 3 A structural form is given in the figure, which includes 11 airbags 6 and 10 gaps. An air channel 4 is arranged inside the driving layer 1 to connect the chambers 3 of all the airbags 6 in sequence. Preferably, in order to prevent the bottom of the driving layer 1 from deforming and expanding under the action of air pressure and affecting the variable stiffness layer 2, the air channel 4 structure is not arranged at the bottom of the chamber 3 in the traditional pneumatic network structure, but the air channel 4 is arranged at a height of 2mm from the bottom of the chamber 3. The air channel 4 is a through-hole structure with a diameter of Φ=2mm. This design helps to better limit the expansion deformation of the bottom surface of the driving layer 1, so that it will not directly exert force on the sheet material in the variable stiffness layer 2. At the same time, the bottom of the notch arranged between the tops of the airbags 6 is designed as an arc structure. This structural design is not only conducive to the design of the air channel 4 structure, but also increases the gap depth of the airbag 6, which is conducive to the driving layer 1 to achieve a larger bending deformation. When the airbag 6 is inflated, the air pressure expands it, thereby pushing the driving layer 1 as a whole to bend toward one side of the variable stiffness layer 2. The deformation ability of the driving layer 1 enables the soft manipulator to complete corresponding bending movements under different air pressures to achieve grasping and manipulation tasks.

[0023] Combination Figure 1 , Figure 4As shown, the variable stiffness layer 2 adopts an open layered damping structure, which is arranged at the bottom of the driving layer 1 and the two are made into one body. The variable stiffness layer 2 is provided with two layers of upper and lower grooves that penetrate the finger root direction along the length direction. The arrangement of the two layers of grooves makes the cross section of the variable stiffness layer 2 present a Japanese shape, wherein the grooves of the lower layer of the variable stiffness layer 2 are filled with sheet materials, and the grooves of the upper layer of the variable stiffness layer 2 can change the friction between the sheet materials by adjusting the air pressure, thereby realizing the adjustment of the system stiffness. When the friction between the sheet materials increases, the system stiffness increases; when the friction between the sheet materials decreases, the system stiffness decreases. The variable stiffness structure of existing soft manipulators generally adopts a closed design, with a limited stiffness adjustment range, which is difficult to adapt to diverse application requirements. The present invention adopts an open design to allow the replacement of sheet materials according to different application scenarios, such as 304 steel or PET, so as to adjust the system stiffness within a larger range, simplify the manufacturing and assembly process, and make maintenance more convenient and quick, which helps to reduce downtime and maintenance costs, while providing greater design flexibility to adapt to different operation requirements. In addition, a textile material layer can be set at the bottom of the variable stiffness layer 2 to prevent cracking and strengthen, effectively preventing the structure from being deformed and cracked under pressure.

[0024] Combination Figure 1 , Figure 5 As shown, the fixed end 5 is integrally arranged at the root of the driving layer 1 and the variable stiffness layer 2, and the fixed end 5 is provided with a first positive pressure air supply channel, a second positive pressure air supply channel and an insertion port, the first positive pressure air supply channel is connected to the chamber 3 of the airbag 6 located at the root, the second positive pressure air supply channel is connected to the groove of the upper layer of the variable stiffness layer 2, the insertion port is the same size as the groove of the lower layer of the variable stiffness layer 2 and is connected, and the filling sheet material is inserted into the groove of the lower layer of the variable stiffness layer 2 through the insertion port. The design of the fixed end 5 is mainly to extend the root of the driving layer 1 and the variable stiffness layer 2, so as to facilitate the connection of pneumatic equipment. On the other hand, considering the difficulty in manufacturing the overall structure, it is easier to manufacture the finger part by dividing it into three parts: the driving layer 1, the variable stiffness layer 2 and the fixed end 5.

[0025] Different from the traditional negative pressure regulation, the present invention adopts positive pressure to regulate the friction between the sheet materials. The positive pressure can not only regulate the friction, but also directly affect the overall structural stiffness. When there is no sheet material in the variable stiffness layer 2, the positive pressure itself will cause the stiffness to change. Through experimental research, as the pressure in the positive pressure chamber 3 increases, the structural stiffness in the non-slip stage gradually increases. When the pressure reaches 120KPa, the stiffness is increased by about 3 times compared with 0KPa. The stiffness of the negative pressure regulation tends to be stable when the negative pressure is greater than 40KPa, and the stiffness in the non-slip stage does not change much. In the full slip stage, the compliance of positive and negative pressure regulation is close, but positive pressure regulation can provide a larger stiffness adjustment range in the non-slip stage. This shows that positive pressure drive can not only achieve the same compliance as negative pressure, but also significantly increase the system stiffness and adapt to a wider range of application scenarios.

[0026] The present invention uses food-grade 30 silica gel as the main material. This material not only has excellent mechanical properties, but also has good safety and environmental protection, and is suitable for operations in food-grade environments or in contact with the human body. In addition, the reasonable layer material design further enhances the gripping ability of the soft manipulator. Through systematic mechanical testing and finite element analysis, the bending ability and bearing capacity of the manipulator have been significantly optimized, ensuring its efficiency and reliability in practical applications.

[0027] The present invention solidifies the driving layer 1 and the variable stiffness layer 2 into one body. When the driving layer 1 is inflated under positive pressure, the airbag 6 deforms and expands under the action of the air pressure, so that the overall elongation of the driving layer 1 is greater than the elongation of the variable stiffness layer 2, thereby bending toward the side of the variable stiffness layer 2 to achieve a grasping action; when the driving layer 1 is deflated, due to the superelastic properties of the silicone material, the driving layer 1 and the variable stiffness layer 2 will return to their original shapes to achieve an opening action.

[0028] In summary, the finger part of the soft manipulator of the present invention can conveniently replace and select the sheet material in the variable stiffness layer 2, and freely adjust the stiffness by replacing the sheet material in the open variable stiffness layer 2, so as to achieve the purpose of adapting to various grasping tasks, especially when handling fragile or special-shaped objects. It can provide soft contact when grasping fragile objects, and can also provide sufficient supporting force when grasping heavy objects and special-shaped objects by replacing the sheet material, without the need to remanufacture the manipulator.

[0029] The soft manipulator of the present invention can be prepared by combining the soft shape deposition method and the soft lithography method. The soft manipulator is mainly divided into a mounting base and a finger part. The finger part includes a driving layer 1, a variable stiffness layer 2 and a fixed end 5. The traditional process usually casts each component in turn, and then uses silicone curing and bonding to combine them into a whole. The present solution replaces the bonding step in the traditional process with a step-by-step casting process. This step-by-step casting process can greatly enhance the connection strength of the joint surfaces of each component, thereby improving the stability of the overall structure. In addition, when preparing the fixed end 5, by embedding the silicone hose in the liquid silicone and curing it at the same time, it can effectively prevent air leakage at the fixed end and improve the air tightness of the soft manipulator. The specific casting method is as follows:

[0030] Casting of driver layer 1

[0031] First, use SolidWorks to build a three-dimensional model of the mold for casting the drive layer 1, and print the mold through a 3D printer. After assembling the mold, spray a rubber release agent on its inner surface to facilitate subsequent demolding. Next, prepare an appropriate amount of food-grade 30 silicone and slowly inject it into the mold. In order to remove bubbles in the liquid silicone, place the mold in a vacuum drying oven and evacuate for 10 minutes. After taking out the mold, place it in an oven at 45°C and heat it for about 30 minutes to promote the curing of the silicone. After curing is completed, remove and dismantle the mold to obtain the drive layer 1.

[0032] Casting of variable stiffness layer 2

[0033] The preparation of the variable stiffness layer 2 is relatively complicated. First, assemble the mold for casting the variable stiffness layer 2, and place a layer of textile material at the bottom of the mold to limit the flexibility of the variable stiffness area to avoid expansion and cracking. Subsequently, slowly pour in the prepared food-grade 30 silicone, and place the mold in a vacuum drying oven to evacuate for 15 minutes to ensure that the bubbles in the liquid silicone are completely discharged. After the silicone liquid surface is flat, use a scraper to flatten the surface. Then, the previously prepared drive layer 1 and the mold of the variable stiffness layer 2 are molded together to tightly combine the two-layer structure. After mold closing, place the mold again in a 45°C oven and heat for 30 minutes, and take it out after the silicone is completely cured. After demolding, trim the excess silicone around the bonding position to obtain a multi-cavity structure of the finger part except for the fixed end 5.

[0034] Casting of fixed end 5

[0035] During the casting process of the fixed end 5, first insert the silicone hose into the specified position of the mold, and seal the bottom of the mold with a glue stick to prevent the liquid silicone from leaking out. Then, slowly pour in the prepared food-grade 30 silicone, and place the mold in a vacuum drying oven and evacuate for 5 minutes to remove bubbles. After the bubbles are completely eliminated, take out the mold, and close the mold of the multi-cavity structure prepared above with the mold of the fixed end 5. After closing the mold, place the mold in a 45°C oven and heat it for 30 minutes. After the silicone is cured, take it out and demold it, and finally the finger part can be formed. According to the needs, the corresponding number of finger parts are fixed to the mounting seat to realize the overall manufacturing of the pneumatic layered damping variable stiffness soft manipulator of the present invention.

[0036] Precautions for integral molding

[0037] Through the above-mentioned three-step casting process, the pneumatic layered damping variable stiffness soft manipulator of the present invention can be successfully prepared. Compared with the traditional soft lithography method, the present invention does not require additional bonding operations, simplifies the manufacturing process, and improves the strength of the combination of various components. However, in the actual operation process, special attention should be paid to the height of the silicone liquid level when the mold is closed. If the liquid level is too high, it may cause too much silicone to fill the cavity, thereby affecting the driving and variable stiffness effects of the manipulator; if the liquid level is too low, it may leave gaps on the bonding surface after the silicone is cured, weakening the stability of the overall structure. Therefore, controlling the height of the silicone liquid level is a key link in ensuring the preparation quality.

[0038] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms of assembly without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0039] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A pneumatic layered damping variable stiffness soft manipulator, comprising a mounting seat and a finger portion fixed thereon, characterized in that: The finger part includes a driving layer (1), a variable stiffness layer (2) and a fixed end (5). The driving layer (1) is evenly provided with a plurality of air bags (6) from the fingertip to the finger root direction. The plurality of air bags (6) are all designed as rectangles, and a notch is provided between the tops of every two adjacent air bags (6) so that there is a gap between the air bags (6). An air passage (4) is arranged inside the driving layer (1) to sequentially connect the chambers (3) of all the air bags (6). The variable stiffness layer (2) is arranged along the whole length at the bottom of the driving layer (1) and the two are made into one body. Two layers of channels running through in the finger root direction are arranged inside the variable stiffness layer (2) along the length direction. The arrangement of the two layers of channels makes the cross section of the variable stiffness layer (2) in a shape of Chinese character 'Ri'. The fixed end (5) is integrally arranged at the roots of the driving layer (1) and the variable stiffness layer (2). The fixed end (5) is provided with a first positive pressure air supply passage, a second positive pressure air supply passage and an insertion port. The first positive pressure air supply passage is communicated with the chamber (3) of the air bag (6) at the root. The second positive pressure air supply passage is communicated with the upper layer channel of the variable stiffness layer (2). The insertion port has the same size as the lower layer channel of the variable stiffness layer (2) and is communicated with it. A filling sheet layer material is inserted into the lower layer channel of the variable stiffness layer (2) through the insertion port.

2. The pneumatic layered damping variable stiffness soft manipulator according to claim 1 is characterized in that: The air passage (4) is arranged at a position 2 mm above the bottom of the chamber (3) of the air bag (6). The air passage (4) is a through hole structure with a diameter Φ = 2 mm.

3. A pneumatic layered damping variable stiffness soft manipulator according to claim 1 or 2, characterized in that: The bottom of the variable stiffness layer (2) is strengthened against cracking by arranging a textile material layer.

4. The pneumatic layered damping variable stiffness soft manipulator according to claim 1, characterized in that: The bottom of the notch provided between the tops of the air bags (6) is in an arc structure.

Images