A pneumatic layered damping variable stiffness soft manipulator

Abstract

A pneumatic, layered, damped, variable stiffness soft manipulator is disclosed, relating to the field of soft manipulator technology. The finger portion includes a drive layer, a variable stiffness layer, and a fixed end. The drive layer has multiple air bladders, with notches between the tops of adjacent air bladders. Air channels connect the chambers of the air bladders sequentially. The variable stiffness layer is integrally formed at the bottom of the drive layer, containing upper and lower channels. The fixed end is integrally formed at the root of the drive layer and the variable stiffness layer. A first positive pressure air supply channel connects to the chamber of the root air bladder, and a second positive pressure air supply channel connects to the upper channel. An insertion port has the same size as and connects to the lower channel, and is filled with sheet material. The open design of the variable stiffness layer and positive pressure pneumatic drive structure allows for convenient replacement of sheet materials and adjustment of stiffness by combining positive pressure as needed. Furthermore, the damping mechanism of the variable stiffness layer helps the manipulator effectively suppress vibration during rapid deformation, improving the stability and accuracy of grasping.

Description

Technical Field

[0001] This invention relates to the field of soft manipulator technology, specifically a pneumatic layered damping variable stiffness soft manipulator. Background Technology

[0002] Traditional rigid manipulators, due to their inherent structural rigidity, have significant limitations when grasping and manipulating complex, irregular, and fragile objects. In contrast, soft manipulators, with their flexibility, deformability, and adaptability, enable more flexible operations and have become a key technology widely researched and applied in recent years, demonstrating enormous potential in various fields. Soft manipulators are typically made of flexible materials and their movement and deformation are controlled by pneumatic, hydraulic, or electro-actuated actuation. However, existing soft manipulators still face challenges in terms of structural stiffness, response speed, and operational stability, especially when grasping objects of different shapes and materials, where current soft manipulators struggle to simultaneously maintain grasping force and protect the object. In practical applications, soft manipulators often need to possess varying stiffness to adapt to different working scenarios and task requirements. Therefore, designing a soft manipulator with dynamically adjustable stiffness has become an important research direction.

[0003] Domestic researchers have conducted various studies to address the problems existing in current soft robotic hands. Chinese invention patent CN118024294A discloses a soft robotic hand based on textile materials with variable stiffness and its usage method. This soft robotic hand utilizes the variable stiffness structure of textile materials to achieve large-scale grasping capabilities. However, because it uses a traditional negative pressure drive method, the compliance and stiffness of the soft robotic hand are not easily matched, affecting the grasping effect. Chinese invention patent CN113601542B discloses a flexible robotic hand based on biomimetic adhesion with variable stiffness. This flexible robotic hand uses a positive pressure pneumatic drive method, effectively solving the imbalance between compliance and stiffness. However, due to its closed variable stiffness structure design, the stiffness of the soft robotic hand is difficult to adjust conveniently, which limits the design in some applications and results in high maintenance costs. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a pneumatic layered damping variable stiffness soft manipulator. Through its open variable stiffness layer and positive pressure pneumatic drive structure design, it can easily replace the layer material as needed and combine it with positive pressure adjustment to achieve stiffness variation. Furthermore, the damping mechanism of the variable stiffness layer helps the manipulator effectively suppress vibration during rapid deformation, thereby improving the stability and accuracy of grasping.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A pneumatic laminated damping variable stiffness soft manipulator, including a mounting base and a finger part fixed thereon. The finger part includes a driving layer, a variable stiffness layer and a fixed end. The driving layer is provided with a plurality of air bags evenly arranged from the fingertip to the finger root direction. The plurality of air bags are all designed as rectangles, and a notch is provided between the tops of every two adjacent air bags to leave a gap between the air bags. An air duct is arranged inside the driving layer to sequentially connect the chambers of all the air bags. The variable stiffness layer is arranged throughout the length at the bottom of the driving layer and the two are made into one body. Two layers of channels penetrating in the finger root direction are arranged inside the variable stiffness layer along the length direction. The arrangement of the two layers of channels makes the cross section of the variable stiffness layer in the shape of a Chinese character 'Ri'. The fixed end is integrally arranged at the roots of the driving layer and the variable stiffness layer. The fixed end 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 of the air bag at the root. The second positive pressure air supply channel is connected to the upper layer channel of the variable stiffness layer. The insertion port has the same size as the lower layer channel of the variable stiffness layer and is connected. A sheet layer material is inserted into the lower layer channel of the variable stiffness layer through the insertion port.

[0006] Further, the air duct is arranged at a position 2 mm above the bottom of the chamber of the air bag, and the air duct is a through hole structure with a diameter Φ = 2 mm.

[0007] Further, the bottom of the variable stiffness layer is strengthened against cracking by arranging a textile material layer.

[0008] Further, the bottom of the notch provided between the tops of the air bags is an arc structure.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[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 layer material to be inserted and filled in the bottom channel of the variable stiffness layer according to specific application requirements. By adjusting the air pressure in the top channel of the variable stiffness layer, the pressure of the sheet layer material can be changed to adjust the stiffness of the soft manipulator, greatly expanding the stiffness adjustment range, ensuring a large bearing capacity, and making the structure manufacturing and assembly simpler, and the maintenance and repair more convenient, improving 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 channel can change the friction force generated by the sheet layer material inserted and filled in the bottom channel. This damping mechanism helps the manipulator effectively suppress vibration during the rapid deformation process, improving the stability and accuracy of grasping, and providing a wider design space;

[0012] 3. This invention uses positive pressure adjustment. In the full sliding stage, the compliance of positive pressure and negative pressure adjustment is similar, but positive pressure can provide a larger stiffness adjustment range in the non-sliding stage. Compared with the traditional negative pressure adjustment method, the stiffness improvement effect of positive pressure adjustment is more significant, up to about 3 times, effectively improving system performance and making it suitable for a wider range of application scenarios. Attached Figure Description

[0013] Figure 1 This is a cross-sectional schematic diagram of the finger portion of the soft robotic hand of the present invention;

[0014] Figure 2 This is a schematic diagram showing the overall appearance of the finger portion of the soft robotic hand of the present invention;

[0015] Figure 3 This is a schematic diagram of the external appearance of the driving layer of the finger portion of the soft robotic hand of the present invention;

[0016] Figure 4 This is a schematic diagram of the external appearance of the variable stiffness layer of the finger portion of the soft robotic hand of the present invention;

[0017] Figure 5 This is a cross-sectional schematic diagram of the fixed end of the finger portion of the soft robotic hand of the present invention;

[0018] Figure 6 This is a schematic diagram illustrating one configuration of the soft robotic arm of the present invention.

[0019] In the diagram: 1. Drive layer; 2. Variable stiffness layer; 3. Chamber; 4. Airway; 5. Fixed end; 6. Airbag. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1-6 As shown, a pneumatic, layered, damped, variable stiffness soft manipulator includes a mounting base and finger portions fixed thereon. Figures 1-2 As shown, the finger portion includes a driving layer 1, a variable stiffness layer 2, and a fixed end 5. Combined with... Figure 6As shown, an example configuration is provided, in which three finger-like components are fixed to the mounting base. The grasping action is achieved through the bending and deformation of these three finger-like components. This configuration is only one example; grasping actions can also be achieved using two or more finger-like components. Furthermore, a rigid limiting plate can be fixed to the mounting base in conjunction with a single finger-like component, whose bending and deformation clamps the object to be grasped to the rigid limiting plate, thus achieving the grasping action. Therefore, the number of finger-like components does not limit the practical application of this soft robotic arm.

[0022] Combination Figure 1 , Figure 3 As shown, the driving layer 1 is a rapid aerodynamic network structure, in which multiple airbags 6 are evenly arranged from the fingertip to the base of the finger. Each airbag 6 is designed to be rectangular, and a notch is provided between the tops of every two adjacent airbags 6 to create a gap between them. This design incorporates a certain gap and wall thickness to optimize bending performance and aerodynamic efficiency. Figure 3 The paper describes a structure consisting of 11 airbags 6 and 10 gaps. An airway 4 is provided inside the drive layer 1, sequentially connecting the chambers 3 of all the airbags 6. Preferably, to prevent the bottom of the drive layer 1 from deforming and expanding under air pressure, thus affecting the variable stiffness layer 2, the airway 4 is not located at the bottom of the chamber 3 as in traditional pneumatic network structures. Instead, the airway 4 is positioned 2mm above the bottom of the chamber 3, and is a through-hole structure with a diameter Φ = 2mm. This design helps to better limit the expansion and deformation of the bottom surface of the drive layer 1, preventing it from directly exerting force on the sheet material in the variable stiffness layer 2. Simultaneously, the bottom of the notch between the tops of the airbags 6 is designed as an arc shape. This structural design not only facilitates the design of the airway 4 structure but also increases the gap depth of the airbags 6, allowing the drive layer 1 to achieve greater bending deformation. When the airbags 6 are inflated, the air pressure causes them to expand, thereby pushing the entire drive layer 1 towards one side of the variable stiffness layer 2. The deformability of the drive layer 1 enables the soft robotic arm to perform corresponding bending movements under different air pressures, thereby achieving grasping and manipulation tasks.

[0023] Combination Figure 1 , Figure 4As shown, the variable stiffness layer 2 adopts an open-layered damping structure, which is longitudinally arranged at the bottom of the driving layer 1 and integrated with it. Inside the variable stiffness layer 2, there are two upper and lower channels running through in the finger root direction along the length direction. The setting of the two channels makes the cross-section of the variable stiffness layer 2 in a figure-eight shape. Among them, a filling sheet material is inserted into the channel of the lower layer of the variable stiffness layer 2, and the friction between the sheet materials can be changed by adjusting the air pressure in the channel of the upper layer of the variable stiffness layer 2, so as to realize 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 structures of existing soft manipulators generally adopt a closed design, with a limited stiffness adjustment range and difficulty in adapting to diverse application requirements. However, the present invention adopts an open design, allowing 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 large range. It also simplifies the manufacturing and assembly processes, is more convenient and fast during maintenance, helps to reduce downtime and maintenance costs, and at the same time provides 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 for anti-cracking reinforcement to effectively prevent the structure from being deformed and cracked under pressure.

[0024] Combined Figure 1 、 Figure 5 [[ID=,7]]As shown, 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 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 channel of the upper layer of the variable stiffness layer 2, and the insertion port has the same size as and is connected to the channel of the lower layer of the variable stiffness layer 2. The filling sheet material is inserted into the channel of the lower layer of the variable stiffness layer 2 through the insertion port. The design of the fixed end 5 is mainly an extension of the roots of the driving layer 1 and the variable stiffness layer 2 to facilitate the connection of pneumatic equipment. On the other hand, it is also considered that there are difficulties in the overall manufacturing of the 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] Unlike traditional negative pressure regulation, this invention uses positive pressure to regulate the friction between the sheet materials. Positive pressure not only regulates friction but also directly affects the overall structural stiffness. When there is no sheet material in the variable stiffness layer 2, the positive pressure itself causes a change in stiffness. Experimental studies show that as the pressure in the positive pressure chamber 3 increases, the structural stiffness in the non-slip stage gradually increases, reaching approximately three times that of 0 kPa at a pressure of 120 kPa. In contrast, the stiffness of negative pressure regulation tends to stabilize when the negative pressure exceeds 40 kPa, with little change in stiffness in the non-slip stage. In the fully slipping stage, the compliance of positive and negative pressure regulation is similar, but positive pressure regulation provides a wider range of stiffness adjustment in the non-slip stage. This indicates that positive pressure drive can not only achieve the same compliance as negative pressure but also significantly increase system stiffness, adapting to a wider range of applications.

[0026] This invention uses food-grade 30 silicone as the main material. This material not only possesses excellent mechanical properties but also exhibits good safety and environmental friendliness, making it suitable for food-grade environments or operations involving human contact. Furthermore, the rational layered material design further enhances the gripping ability of the soft robotic arm. Through systematic mechanical testing and finite element analysis, the bending capacity and load-bearing capacity of the robotic arm have been significantly optimized, ensuring its high efficiency and reliability in practical applications.

[0027] This invention integrates the driving layer 1 and the variable stiffness layer 2 into one unit. When the driving layer 1 is inflated under positive pressure, the airbag 6 deforms and expands under the action of 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 towards the variable stiffness layer 2 to achieve the grasping action. When the driving layer 1 is deflated, due to the superelastic properties of the silicone material, both the driving layer 1 and the variable stiffness layer 2 will return to their original shape, achieving the opening action.

[0028] In summary, the finger portion of the soft robotic hand of the present invention allows for easy replacement of the sheet material within the variable stiffness layer 2. By changing the sheet material in the open variable stiffness layer 2, the stiffness can be freely adjusted to adapt to various grasping tasks. In particular, when handling fragile or irregularly shaped objects, it can provide soft contact when grasping fragile objects, and can also provide sufficient support force when grasping heavy or irregularly shaped objects by changing the sheet material, without the need to remanufacture the robotic hand.

[0029] This invention relates to a soft robotic hand, which can be fabricated using a combination of soft shape deposition and soft plate printing. The soft robotic hand mainly consists of a mounting base and finger parts. The finger parts include a drive layer 1, a variable stiffness layer 2, and a fixed end 5. Traditional processes typically involve casting each component sequentially and then bonding them together using silicone curing. This invention, however, replaces the bonding step in a step-by-step casting process. This step-by-step casting process significantly enhances the connection strength of the joint surfaces of each component, thereby improving the overall structural stability. Furthermore, during the fabrication of the fixed end 5, embedding a silicone tube into liquid silicone and simultaneously curing it effectively prevents air leakage at the fixed end, improving the airtightness of the soft robotic hand. The specific casting method is as follows:

[0030] Casting of Drive Layer 1

[0031] First, a 3D model of the mold for casting driving layer 1 was created using SolidWorks and printed using a 3D printer. After assembling the mold, a rubber release agent was sprayed onto its inner surface to facilitate subsequent demolding. Next, an appropriate amount of food-grade 30 silicone was prepared and slowly injected into the mold. To remove air bubbles from the liquid silicone, the mold was placed in a vacuum drying oven and evacuated for 10 minutes. After removing the mold, it was placed in an oven at 45°C and heated for approximately 30 minutes to promote silicone curing. Once curing was complete, the mold was removed and dismantled to obtain driving layer 1.

[0032] Casting of variable stiffness layer 2

[0033] The preparation of the variable stiffness layer 2 is relatively complex. First, a mold for casting the variable stiffness layer 2 is assembled. A textile material layer is placed at the bottom of the mold to limit the flexibility of the variable stiffness area and prevent expansion and cracking. Then, the prepared food-grade 30 silicone is slowly poured in, and the mold is placed in a vacuum drying oven and evacuated for 15 minutes to ensure that air bubbles in the liquid silicone are completely removed. After the silicone surface is level, it is smoothed with a scraper. Next, the previously prepared drive layer 1 and the mold of the variable stiffness layer 2 are joined together, ensuring a tight bond between the two layers. After joining, the mold is placed again in a 45°C oven for 30 minutes until the silicone is completely cured. After demolding, excess silicone around the bonding area is trimmed, resulting in a multi-cavity structure for the finger portion, excluding the fixed end 5.

[0034] Casting of fixed end 5

[0035] During the casting process of fixed end 5, a silicone tube is first inserted into the designated position of the mold, and the bottom of the mold is sealed with a glue stick to prevent liquid silicone from leaking out. Then, the prepared food-grade 30 silicone is slowly poured in, and the mold is placed in a vacuum drying oven to evacuate for 5 minutes to remove air bubbles. After the air bubbles are completely eliminated, the mold is removed, and the multi-cavity structure prepared above is joined with the mold of fixed end 5. After joining the molds, the molds are placed in a 45°C oven and heated for 30 minutes. After the silicone has solidified, the molds are removed and demolded, thus forming the finger parts. The corresponding number of finger parts are then fixed to the mounting base as needed, thus realizing the overall manufacturing of the pneumatic layered damping variable stiffness soft manipulator of this invention.

[0036] Precautions for integral molding

[0037] The pneumatic layered damping variable stiffness soft manipulator of this invention can be successfully fabricated through the three-step casting process described above. Compared with the traditional soft flatbed printing method, this invention does not require additional bonding operations, simplifying the manufacturing process and improving the bonding strength of each component. However, in actual operation, the height of the silicone liquid level during mold closing requires special attention. If the liquid level is too high, excessive silicone may fill the cavity, affecting the manipulator's drive and variable stiffness effect; if the liquid level is too low, gaps may remain at the bonding surface after the silicone cures, weakening the overall structural stability. Therefore, controlling the height of the silicone liquid level is a key step in ensuring the quality of the fabrication.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A pneumatic layered damping variable stiffness soft manipulator, comprising a mounting base and finger portions 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 provided with a plurality of air bags (6) uniformly 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 duct (4) is arranged inside the driving layer (1) to connect the chambers (3) of all the air bags (6) in sequence. 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 penetrating 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 figure-eight shape. The fixed end (5) is integrally arranged at the root of the driving layer (1) and the variable stiffness layer (2). 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 air bag (6) at the root. The second positive pressure air supply channel is connected to the upper layer channel of the variable stiffness layer (2). The insertion port has the same size as and is connected to the lower layer channel of the variable stiffness layer (2). A sheet material layer is inserted into the lower layer channel of the variable stiffness layer (2) through the insertion port. The upper layer channel of the variable stiffness layer (2) can change the friction force between the sheet materials by inputting positive pressure, so as to realize the adjustment of the stiffness of the manipulator. By replacing the sheet material in the open variable stiffness layer (2), the stiffness can be freely adjusted to achieve the purpose of adapting to various grasping tasks.

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

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