Variable rigidity structure of soft robot and soft robot

Abstract

The invention relates to the technical field of robots, and discloses a variable-rigidity structure of a soft robot and the soft robot. The variable-rigidity structure of the soft robot comprises an elastic pipe sleeve; each chain bundle comprises a plurality of mutually-stacked chains, each chain comprises a plurality of mutually-connected metal chain links, each metal chain link can rotate, gaps are formed between the metal chain links of every two adjacent chains in each chain bundle, every two adjacent chain bundles are arranged in a staggered mode, and the metal chain links of the metal chain links can rotate. Each chain of each chain bundle is filled with part of gaps of the adjacent chain bundles; when the interior of the elastic pipe sleeve is in a non-negative pressure state, the metal chain links of the two adjacent chain bundles can slide relatively, and when the interior of the elastic pipe sleeve is in a negative pressure state, the metal chain links of the two adjacent chain bundles abut against each other under the radial pressure of the elastic pipe sleeve so as to be locked with each other. In this way, the rigidity gain multiple of the variable-rigidity structure of the soft robot is increased.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of robotics technology, and particularly to a variable stiffness structure of a soft robot and the soft robot. Background Art

[0002] Currently, in the field of soft robotics, three structures—layer-blocking, particle-blocking, and fiber-blocking—all use the blocking principle to enhance or weaken stiffness. Among them, fiber-blocking structures have attracted attention due to the initial softness of flexible fiber materials and their ability to be braided and filled.

[0003] However, when traditional fiber materials (such as polymer fibers like nylon, polyester, and polyethylene) are stacked, friction and geometric entanglement between the fibers cause the fiber-jammed structure to have a certain stiffness even in a non-vacuum state. Furthermore, due to the elasticity of the fibers, when an external force acts on them, the fibers first undergo elastic deformation to absorb some of the energy, which limits the increase in the contact area between the fibers. Consequently, the overall stiffness adjustment range of the fiber-jammed structure is limited, making it difficult to simultaneously achieve high initial compliance and a large stiffness gain. Summary of the Invention

[0004] In view of the above problems, an embodiment of the present application provides a variable stiffness structure of a soft robot and a soft robot, which increases the stiffness gain multiple of the variable stiffness structure of the soft robot.

[0005] According to one aspect of an embodiment of the present application, a variable stiffness structure of a soft robot and a soft robot are provided, the variable stiffness structure of the soft robot comprising: an elastic tube sleeve; a plurality of chain bundles arranged in the elastic tube sleeve, each chain bundle comprising a plurality of chains stacked on each other, each chain comprising a plurality of metal links connected to each other, each metal link being rotatable, a gap being provided between the plurality of metal links of two adjacent chains in each chain bundle, and the two adjacent chain bundles being staggered so that each chain of each chain bundle fills part of the gap between the adjacent chain bundles; when the elastic tube sleeve is in a non-negative pressure state, the metal links of the two adjacent chain bundles can slide relative to each other, and when the elastic tube sleeve is in a negative pressure state, the metal links of the two adjacent chain bundles are abutted against each other by the radial pressure of the elastic tube sleeve to be locked with each other.

[0006] In an optional manner, each metal link includes a first metal link and a second metal link, both of which are annular structures. The multiple first metal links and the multiple second metal links of each chain are alternately arranged in pairs and are connected in sequence by loops. The first metal link and the second metal link of each chain are perpendicular to each other and rotatable. In two adjacent chains of each chain bundle, the multiple second metal links of one chain correspond to the positions of the multiple second metal links of the other chain and are stacked on each other, so that a gap is formed between the multiple first metal links of one chain and the multiple first metal links of the other chain in the two adjacent chains. The multiple first metal links of each chain of each chain bundle fill part of the gap between the adjacent chain bundles.

[0007] In an optional manner, the two stacked second metal links of two adjacent chains of each chain bundle are an integral structure.

[0008] In an optional manner, in each chain, there is a gap between two adjacent second metal links connected to the same first metal link collar, and there is a gap between two adjacent first metal links connected to the same second metal link collar.

[0009] In an optional manner, when the elastic tube sleeve is in a non-negative pressure state, there is a gap between the chain at the edge of each chain bundle and the elastic tube sleeve, and the ratio of the projected area of ​​the multiple chain bundles on the radial plane of the elastic tube sleeve to the inner diameter cross-sectional area of ​​the elastic tube sleeve is 95% to 105%.

[0010] In an optional embodiment, the roughness of the metal link surface is 0.15-0.3 μm, the static friction coefficient between the multiple metal links is 0.3-0.4, and the dynamic friction coefficient between the metal link and the elastic sleeve is 0.25-0.32.

[0011] In an optional embodiment, an end cap is provided at the end of the elastic tube sleeve, the end cap is sealed and connected to the elastic tube sleeve, a pipe is connected to the end of the end cap facing away from the elastic tube sleeve, a through hole is opened in the end cap, the pipe is connected to the elastic tube sleeve through the through hole, and the pipe is used to connect to the negative pressure control device to control the negative pressure state of the elastic tube sleeve through the negative pressure control device.

[0012] In an optional embodiment, the end of each chain is located at the same end as the end of the elastic tube sleeve, and a limit member is fixedly provided on the end cover toward one end of the elastic tube sleeve. The limit member is used to pass through the end metal link of each chain in turn to limit the axial displacement of each chain bundle along the elastic tube sleeve.

[0013] In an optional embodiment, the elastic sleeve is made of silicone and the metal link is made of titanium steel.

[0014] According to another aspect of an embodiment of the present application, a soft robot is provided, comprising: a negative pressure source, a pressure regulating valve, and the variable stiffness structure of the soft robot provided in any of the above embodiments; the pressure regulating valve is connected to the negative pressure source and the variable stiffness structure of the soft robot through a first pipe and a second pipe, respectively, and the negative pressure source is used to control the gas content in the elastic tube sleeve through the pressure regulating valve to control the negative pressure state in the elastic tube sleeve, thereby controlling the stiffness of the variable stiffness structure of the soft robot.

[0015] In an optional embodiment, the soft robot also includes a sensor and a controller, the sensor is arranged in the second pipeline, and the controller is electrically connected to the negative pressure source, the sensor and the pressure regulating valve respectively; the sensor is used to detect the pressure in the elastic tube sleeve and send the pressure to the controller; the controller is used to receive the pressure and control the operation of the negative pressure source and the pressure regulating valve according to the pressure to adjust the negative pressure in the elastic tube sleeve to the target negative pressure.

[0016] The variable stiffness structure provided in the embodiments of the present application includes multiple chain bundles disposed within an elastic sleeve. These are interconnected by multiple rotatable metal links to form a chain, and the multiple chains are stacked together to form a chain bundle. This allows the multiple chain bundles to bend freely, thereby providing the variable stiffness structure with a low bending stiffness. Furthermore, by staggering two adjacent chain bundles, each chain within each chain bundle can fill a portion of the gaps between the multiple metal links of two adjacent chains within the adjacent chain bundle. In this way, when the elastic sleeve is in a non-negative pressure state, the contact area between the metal links of two adjacent chain bundles is small, the friction wedge lock effect is weak, and the metal links can slide relatively, so that the variable stiffness structure still has a low bending stiffness; when the elastic sleeve is in a negative pressure state, all chain bundles undergo rigid body displacement under the action of the radial pressure of the elastic sleeve, multiple chains are squeezed against each other, and the contact area between the metal links of adjacent chain bundles is increased, so that the metal links of adjacent chain bundles have a strong friction wedge lock effect to lock each other, so that the variable stiffness structure has a higher bending stiffness, thereby increasing the stiffness gain multiple of the variable stiffness structure.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0019] Figure 1 A three-dimensional diagram of the variable stiffness structure of the soft robot provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of the structure of multiple chain bundles provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the structure of the chain bundle provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of the structure of the chain provided in an embodiment of the present application;

[0023] Figure 5 A radial cross-sectional view of the variable stiffness structure of the soft robot provided in an embodiment of the present application;

[0024] Figure 6 A force-displacement diagram of the variable stiffness structure of the soft robot provided in an embodiment of the present application when the negative pressure in the elastic sleeve is 0 kPa;

[0025] Figure 7 A force-displacement diagram of the variable stiffness structure of the soft robot provided in an embodiment of the present application when the negative pressure in the elastic sleeve is -80 kPa;

[0026] Figure 8 A schematic structural diagram of a soft robot provided in an embodiment of the present application is shown.

[0027] The accompanying drawings in the specific implementation manner are as follows:

[0028] 1. Soft robot; 10. Variable stiffness structure of the soft robot; 20. Negative pressure source; 30. Pressure regulating valve; 31. First pipeline; 32. Second pipeline; 40. Pressure relief valve; 50. Sensor; 60. Controller;

[0029] 100. Elastic sleeve; 120. First end cap; 130. Second end cap; 200, 200a, 200b, 200c. Chain bundle; 210. Chain; 211. Metal link; 2111. First metal link; 2112. Second metal link; 2111a, 2112a. Gap; 212. Space; 300. Pipe; 400. Negative pressure control device. DETAILED DESCRIPTION

[0030] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0032] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0033] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0034] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0035] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0036] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0037] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0038] The blocking principle is the core means of achieving reversible control of structural stiffness. Its essence is to change the state of the medium through external control (such as vacuum), thereby increasing or decreasing the stiffness. At present, this blocking principle is widely seen in the field of soft robotics in three variable stiffness structures: layer blocking, particle blocking, and fiber blocking. Among them, layer blocking uses multiple layers of thin sheets stacked and vacuumed to enhance stiffness, particle blocking uses granular media (such as coffee powder and small balls) to squeeze each other under vacuum to increase friction and enhance stiffness, and fiber blocking uses slender fiber media to entangle and rub under vacuum to increase stiffness.

[0039] In particle-blocking structures, stiffness can be enhanced by filling the structure with a number of endoskeletons and particle spheres and then using a vacuum pump to squeeze the particles together. These solutions use polymer filaments or particles as the medium. However, polymer filaments themselves have inherent stiffness and high bending resistance at normal pressure. When subjected to tension, the particles tend to disperse, causing the variable stiffness structure to fail. Therefore, existing particle-blocking structures suffer from limited stiffness enhancement.

[0040] Fiber-jammed structures have attracted attention due to the initial softness and weavable filling properties of flexible fiber materials. However, when traditional fiber materials (such as nylon, polyester, and polyethylene polymer fibers) are stacked, interfiber friction and geometric entanglement result in a certain stiffness in the non-vacuum state. Furthermore, due to the elasticity of the fibers, when an external force acts on them, they first undergo elastic deformation to absorb some of the energy, resulting in a limited increase in the interfiber contact area. Consequently, fiber-jammed structures suffer from the disadvantages of high initial stiffness and a limited stiffness change ratio. For example, studies have shown that nylon fibers exhibit high stiffness before vacuum application, but the stiffness gain is not significant after vacuum application. Natural fibers such as waxed cotton, while initially soft, only exhibit a stiffness gain of approximately 4.7 times. Other materials, such as PTFE (Polytetrafluoroethylene), PVC (Polyvinyl Chloride), silicone fibers, and leather strips, generally exhibit stiffness gains of 2-4 times under vacuum. In summary, the overall stiffness adjustment range of the fiber-blocking structure is limited, and it is difficult to simultaneously achieve high initial compliance and a large stiffness gain multiple.

[0041] After research, it was found that each metal link of the metal chain can rotate freely, making the metal chain more flexible. Therefore, the present application uses the metal chain as a blocking medium for the variable stiffness structure of the soft robot, which can make the variable stiffness structure more flexible. Furthermore, in order to increase the contact area between the metal chains, multiple metal chains are stacked on top of each other to form multiple metal chain bundles. Since gaps are formed between the stacked metal chains in each metal chain bundle, in order to increase the contact area between the metal chains of two adjacent metal chain bundles, the multiple metal chain bundles are staggered so that the metal chains of adjacent metal chain bundles can fill each other's gaps. In this way, when not subjected to radial pressure, the metal links of two adjacent metal chain bundles can slide relative to each other, so that the variable stiffness structure still has a relatively high initial softness; when subjected to radial pressure, all metal chain bundles undergo inward rigid body displacement, so that all metal chains are squeezed against each other, increasing the contact area of ​​the metal links of adjacent metal chain bundles, thereby generating a friction-wedge lock effect between the metal links of adjacent metal chain bundles and locking them with each other, improving the stiffness of the variable stiffness structure, and thereby increasing the stiffness gain multiple of the variable stiffness structure.

[0042] See also Figure 1-Figure 3 , Figure 1 A three-dimensional diagram of a variable stiffness structure of a soft robot provided in an embodiment of the present application is shown. Figure 2 A schematic diagram showing the structure of multiple chain bundles provided in an embodiment of the present application is shown ( Figure 2 Only three chains are used for illustration and are not limiting), wherein, Figure 2 (a), (b) and (c) show the front view, left view and stereogram of multiple chain bundles respectively. Figure 3 The schematic diagram of the structure of the chain bundle provided in the embodiment of the present application is shown (the figure only takes the chain bundle including 3 chains as an example for illustration, which is not limiting), wherein: Figure 3(a) and (b) show the front and left views of a chain bundle, respectively. As shown in the figure, the variable stiffness structure 10 of the soft robot (hereinafter referred to as the variable stiffness structure 10) includes an elastic sleeve 100 and multiple chain bundles 200. Each chain bundle 200 includes multiple stacked chains 210, each chain 210 including multiple interconnected metal links 211. Each metal link 211 is rotatable, and a gap 212 is defined between the multiple metal links 211 of two adjacent chains 210 in each chain bundle 200. The adjacent chain bundles 200 are staggered so that each chain 210 in each chain bundle 200 partially fills the gap 212 of the adjacent chain bundle 200. When the elastic tube sleeve 100 is in a non-negative pressure state, the metal links 211 of two adjacent chain bundles 200 can slide relative to each other. When the elastic tube sleeve 100 is in a negative pressure state (vacuum), the metal links 211 of two adjacent chain bundles 200 abut against each other under the radial pressure of the elastic tube sleeve 100 to be locked together.

[0043] The elastic sleeve 100 may be made of silicone, natural rubber, polyurethane, or thermoplastic elastomer (TPE), etc. The metal link 211 may be made of titanium steel, stainless steel, nickel-titanium alloy, or other metals or alloys.

[0044] The number of chain bundles 200 within the variable stiffness structure 10 can be set based on the desired diameter of the variable stiffness structure 10 and the chain bundle filling rate. The number of chains 210 in each chain bundle 200 can be set based on the desired diameter of the variable stiffness structure 10. The number of metal links 211 in each chain 210 can be set based on the desired length of the variable stiffness structure 10. In the embodiment of the present application, the variable stiffness structure 10 can be provided with 25 chains 210. Figure 2 In the embodiment shown, seven chains 210 are provided.

[0045] The chain 210 can be a miniature chain such as a Chopin chain, a ball chain, or a hinged chain. Each metal link 211 of the chain 210 has a rotation margin greater than 70°, allowing the metal link 211 to rotate freely, thereby ensuring that the chain 210 is not constrained from bending within the elastic tube 100. For example, when the chain 210 is a Chopin chain, two adjacent metal links 211 can be connected in a buckle manner. When the elastic tube 100 is in a non-negative pressure state, each metal link 211 can rotate to form a "V" shape with the adjacent metal link 211. When the chain 210 is a hinged chain, each metal link 211 can rotate 90° when the elastic tube 100 is in a non-negative pressure state.

[0046] like Figure 3 As shown, 3 Figure 4The chains 210 shown are stacked on each other to obtain Figure 3 The chain bundle 200 shown in (a) is formed between two adjacent chains 210. Figure 3 When three chains 210 are stacked on top of each other, the chain bundle 200 has four gaps 212 shown in (b).

[0047] Please continue reading Figure 2 Chain bundle 200b is staggered with chain bundle 200a and chain bundle 200c, respectively. This allows the chains 210 of chain bundle 200b to fill the gaps 212 of chain bundle 200a and chain bundle 200c, respectively. For example, the chains 210 of chain bundle 200a can fill the gaps 212 on the left side of chain bundle 200b, and the chains 210 of chain bundle 200c can fill the partial gaps 212 on the right side of chain bundle 200b. This not only prevents each chain 210 from becoming tangled within the elastic sleeve 100, but also ensures that each chain 210 is in contact with at least two other chains 210. Filling the partial gaps 212 means that a small portion of the adjacent surfaces of the metal chain links 211 of two adjacent chain bundles 200 are in contact with each other, while a gap a exists between the majority of the adjacent surfaces.

[0048] When the variable stiffness structure 10 is in its initial state, that is, when the elastic sleeve 100 is in a non-negative pressure state (0 kPa), for example, the air pressure within the elastic sleeve 100 is equal to the external air pressure (e.g., 0 kPa), the elastic sleeve 100 has no inward radial compressive force, and the multiple chain bundles 200 are loosely suspended within the elastic sleeve 100. The metal links 211 of the multiple chain bundles 200 only slightly contact each other, and the contact area between the metal links 211 of the multiple chain bundles 200 is relatively small. In this state, when an external force is applied to bend the variable stiffness structure 10, the friction between the metal links 211 of adjacent chain bundles 200 is insufficient to resist the weight of the metal links 211 and the external force, allowing the metal links 211 of adjacent chain bundles 200 to slide relative to each other. As a result, the variable stiffness structure 10 has an extremely low initial bending stiffness, allowing the variable stiffness structure 10 to be easily bent to the target bending angle under the action of an external force. After the external force is removed, the friction between the metal links 211 of adjacent chain bundles 200 can enable the variable stiffness structure 10 to still maintain the target bending angle.

[0049] When the elastic sleeve 100 is in a negative pressure state, for example, when the negative pressure in the elastic sleeve 100 is -20kPa, -40kPa or -80kPa, the elastic sleeve 100 contracts radially inward under the pressure of atmospheric pressure, exerting radial compression force on the multiple chain bundles 200, so that the multiple chain bundles 200 are Figure 2The straight arrows in (b) indicate inward movement, causing the multiple chains 210 to press inward against each other. During this process, the multiple chains 210 undergo rigid body displacement, and the metal links 211 of adjacent chain bundles 200 closely abut each other, increasing the contact area between the metal links 211 of adjacent chain bundles 200, thereby increasing the friction between the metal links 211 of adjacent chain bundles 200. At this time, when the variable stiffness structure 10 is bent using an external force, the friction between the metal links 211 of adjacent chain bundles 200 and the radial pressure of the elastic sleeve 100 on the metal links 211 can resist the weight of the metal links 211 themselves and the external force, resulting in a strong friction wedge lock effect between the metal links 211 of adjacent chain bundles 200, locking them together. In this way, the bending stiffness of the variable stiffness structure 10 is significantly improved compared to the initial bending stiffness, making it impossible for the variable stiffness structure 10 to bend to the target bending angle under the action of external force. After the external force is removed, the friction between the metal links 211 of adjacent chain bundles 200 and the radial pressure exerted by the elastic sleeve 100 on the metal links 211 still exist, allowing the variable stiffness structure 10 to maintain a high-stiffness locked state. By adjusting the negative pressure (vacuum level) within the elastic sleeve 100, the radial pressure exerted by the elastic sleeve 100 on the metal links 211 can be adjusted, thereby adjusting the stiffness of the variable stiffness structure 10, thereby achieving stiffness adjustment of the variable stiffness structure 10.

[0050] The variable stiffness structure 10 provided in the embodiment of the present application includes a plurality of chain bundles 200 disposed within an elastic sleeve 100. The chains 210 are interconnected by a plurality of rotatable metal links 211. The plurality of chains 210 are stacked together to form a chain bundle 200, allowing the plurality of chain bundles 200 to bend freely, thereby providing the variable stiffness structure 10 with a relatively low bending stiffness. Furthermore, by staggering two adjacent chain bundles 200, each chain 210 in each chain bundle 200 can fill a portion of the gaps 212 between the plurality of metal links 211 of two adjacent chains 210 in the adjacent chain bundle 200. In this way, when the elastic sleeve 100 is in a non-negative pressure state, the metal links 211 of two adjacent chain bundles 200 have a small contact area and a weak friction wedge lock effect, so the metal links 211 can slide relative to each other, so that the variable stiffness structure 10 still has a low bending stiffness; when the elastic sleeve 100 is in a negative pressure state, all the chain bundles 200 undergo rigid body displacement under the action of the radial pressure of the elastic sleeve 100, and multiple chains 210 are squeezed against each other, and the contact area between the metal links 211 of adjacent chain bundles 200 is increased, so that the metal links 211 of adjacent chain bundles 200 have a strong friction wedge lock effect and lock each other, thereby making the variable stiffness structure 10 have a higher bending stiffness, thereby increasing the stiffness gain multiple of the variable stiffness structure 10.

[0051] In order to increase the stiffness gain multiple of the variable stiffness structure 10, the present application further proposes an implementation method. Figure 3 and Figure 4 As shown in the figure, each metal link 211 includes a first metal link 2111 and a second metal link 2112. The first metal link 2111 and the second metal link 2112 are both ring-shaped structures. The multiple first metal links 2111 and the multiple second metal links 2112 of each chain 210 are alternately arranged in pairs and connected in a loop in sequence. The first metal link 2111 and the second metal link 2112 of each chain 210 are perpendicular to each other and can rotate. Please continue to refer to Figure 3 In each chain bundle 200, the multiple second metal links 2112 of one chain 210 correspond to and are stacked with the multiple second metal links 2112 of the other chain 210 in a one-to-one relationship. This creates a gap 212 between the multiple first metal links 2111 of one chain 210 and the multiple first metal links 2111 of the other chain 210. The multiple first metal links 2111 of each chain 210 in each chain bundle 200 partially fill the gap 212 of the chain bundle 200 adjacent to that chain bundle 200.

[0052] The first metal link 2111 and the second metal link 2112 can both have a square ring structure, such as a rounded rectangular ring structure. The square ring structure not only increases the stacking area between two stacked second metal links 2112, thereby improving the structural stability of each chain bundle 200, but also increases the contact area between the first metal links 2111 of two adjacent chain bundles 200, and between the first metal link 2111 and the second metal link 2112.

[0053] Please continue reading Figure 4 In each chain 210, except for the first metal link 2111 or the second metal link 2112 at the head and tail, the two ends of each first metal link 2111 are respectively connected to a second metal link 2112 ring, and the two ends of each second metal link 2112 are respectively connected to a first metal link 2111 ring.

[0054] Preferably, in order to ensure that the plurality of chain bundles 200 have a greater initial flexibility, please continue to refer to Figure 4In each chain 210, a gap 2112a is provided between two adjacent second metal links 2112 connected to the same first metal link 2111, and a gap 2111a is provided between two adjacent first metal links 2111 connected to the same second metal link 2112. This ensures that when one of the two first metal links 2111 connected to the same second metal link 2112 rotates along the second metal link 2112, the other first metal link 2111 does not block its rotation, ensuring free rotation. Similarly, when two second metal links 2112 connected to the same first metal link 2111 do not block the free rotation of the other second metal link 2112. By providing these gaps (2111a, 2112a), each chain 210 can be guaranteed to have a high initial flexibility, thereby ensuring that each chain bundle 200 has a high initial flexibility.

[0055] Since the first metal links 2111 and the second metal links 2112 of each chain 210 are perpendicular to each other, in two adjacent chains 210 of each chain bundle 200, when the multiple second metal links 2112 of one chain 210 and the multiple second metal links 2112 of the other chain 210 are stacked on each other, the multiple first metal links 2111 of one chain 210 and the multiple first metal links 2111 of the other chain 210 are parallel to each other, so that a larger gap 212 can be formed between the multiple first metal links 2111 of one chain 210 and the multiple first metal links 2111 of the other chain 210. When the multiple first metal links 2111 of each chain 210 of each chain bundle 200 fill a portion of the gap 212 of the chain bundle 200 adjacent to the chain bundle 200, the first metal links 2111 can be parallel to the two first metal links 2111 forming the gap 212. Therefore, when the multiple chain bundles 200 undergo inward rigid body displacement under the action of radial pressure, the contact area between the first metal links 2111 and the two first metal links 2111 forming the gap 212 can be increased, thereby increasing the friction between the first metal links 2111, thereby strengthening the friction wedge-locking effect between the chains 210 of two adjacent chain bundles 200, thereby increasing the stiffness of the variable stiffness structure 10 and further improving the stiffness gain multiple of the variable stiffness structure 10.

[0056] In order to prevent the misalignment between the chains 210 and ensure that the variable stiffness structure 10 has a larger stiffness gain multiple, the present application further proposes an implementation method. Figure 3 and Figure 4The two stacked second metal links 2112 of two adjacent chains 210 of each chain bundle 200 form an integrated structure. In this way, it can be ensured that the multiple chains 210 in each chain bundle 200 are fixedly connected in pairs, so that each chain bundle 200 forms an integral structure, avoiding dislocation of the chains 210 of the multiple chain bundles 200 when rigid body displacement occurs, and ensuring that the multiple first metal links 2111 of each chain 210 of each chain bundle 200 can fill part of the gap 212 of the chain bundle 200 adjacent to the chain bundle 200, ensuring that when the elastic tube sleeve 100 is in a negative pressure state, there is a larger contact area between the first metal links 2111 of the two adjacent chain bundles 200 and between the first metal link 2111 and the second metal link 2112, thereby enhancing the friction between the first metal links 2111 and between the first metal link 2111 and the second metal link 2112 of the two adjacent chain bundles 200, so that the variable stiffness structure 10 has greater stiffness, thereby ensuring that the variable stiffness structure 10 has a greater stiffness gain multiple.

[0057] In order to ensure that the variable stiffness structure 10 has a lower bending stiffness in a non-negative pressure state, the present application further proposes an implementation method. Figure 2 and Figure 3 , and combined with Figure 5 , Figure 5 A radial cross-sectional view of the variable stiffness structure provided by an embodiment of the present application is shown. As shown in the figure, when the elastic sleeve 100 is in a non-negative pressure state, a gap exists between the chain 210 located at the edge of each chain bundle 200 and the elastic sleeve 100. Specifically, a radial gap of 10 to 20 μm can exist between the metal links 211 of the chain 210 located at the edge of at least some of the chain bundles 200 and the elastic sleeve 100. This gap ensures that some of the chain bundles 200 do not contact the elastic sleeve 100 in the non-negative pressure state and are not affected by the radial pressure of the elastic sleeve 100. This allows the multiple chain bundles 200 to slide relative to each other, ensuring that the variable stiffness structure 10 has low bending stiffness in the non-negative pressure state.

[0058] Furthermore, in order to ensure that the variable stiffness structure 10 has a high bending stiffness under negative pressure, the present application further proposes an implementation method. Figure 5 As shown in the figure, the projected area of ​​the multiple chain bundles 200 on the radial plane of the elastic sleeve 100 is smaller than the inner diameter cross-sectional area of ​​the elastic sleeve 100. In some embodiments, the projected area of ​​the multiple chain bundles 200 on the radial plane of the elastic sleeve 100 may also be greater than or equal to the inner diameter cross-sectional area of ​​the elastic sleeve 100. Therefore, the ratio of the projected area of ​​the multiple chain bundles 200 on the radial plane of the elastic sleeve 100 to the inner diameter cross-sectional area of ​​the elastic sleeve 100 can be set to 95% to 105%, preferably 99% to 105%.

[0059] The projected area of ​​the plurality of chain bundles 200 on the radial plane of the elastic sleeve 100 is Figure 5 The sum of the areas of all metal links 211 shown in .

[0060] Because the elastic sleeve 100 is elastic, as more chain bundles 200 are filled into the elastic sleeve 100, the elastic sleeve 100 will deform. This deformation can cause the inner diameter of the elastic sleeve 100 filled with the chain bundles 200 to be larger than the radius of the undeformed elastic sleeve 100. In this case, the projected area of ​​the multiple chain bundles 200 on a radial plane of the elastic sleeve 100 is larger than the cross-sectional area of ​​the inner diameter of the elastic sleeve 100.

[0061] By setting the ratio of the projected area of ​​the multiple chain bundles 200 on the radial plane of the elastic sleeve 100 to the inner diameter cross-sectional area of ​​the elastic sleeve 100 to 95-105%, gaps are created between the multiple chain bundles 200 and between the chain bundles 200 and the inner wall of the elastic sleeve 100. In a non-negative pressure state, the multiple chain bundles 200 can be in a loosely suspended state, ensuring that the variable stiffness structure 10 has low bending stiffness. In a negative pressure state, the multiple chain bundles 200 can be squeezed inward and fully adhere to each other, ensuring that the variable stiffness structure 10 has high bending stiffness, thereby increasing the stiffness gain multiple of the variable stiffness structure 10.

[0062] In some embodiments, as Figure 4 As shown, the diameter r of each metal link 211 can be set to 1.5 mm. In order to improve the friction wedge locking effect between the metal links 211 of two adjacent chain bundles 200, the contact area between each metal link 211 and the contacting metal link 211 is set to 0.55-0.62 mm under negative pressure. 2 .

[0063] In order to increase the stiffness gain multiple of the variable stiffness structure 10, the present application further proposes an implementation method. Figure 4 As shown in the figure, the roughness of the surface of the metal link 211 is 0.15-0.3 μm, preferably 0.2 μm, the static friction coefficient between the multiple metal links 211 is 0.3-0.4, preferably 0.35, and the dynamic friction coefficient between the metal link 211 and the elastic sleeve 100 is 0.25-0.32, preferably 0.28.

[0064] Research has found that the surface roughness of the metal links 211 is positively correlated with their friction coefficient. When the roughness of the metal links 211 exceeds 0.3 μm, the metal links 211 surface easily wears, resulting in a stagnation in the static friction coefficient between the metal links 211 and the dynamic friction coefficient between the metal links 211 and the elastic sleeve 100. At this point, the friction between the metal links 211 and between the metal links 211 and the elastic sleeve 100 approaches saturation, causing the stiffness of the variable stiffness structure 10 to also approach saturation.

[0065] When the roughness of the metal links 211 is less than 0.15 μm, the static friction coefficient between the metal links 211 and the dynamic friction coefficient between the metal links 211 and the elastic sleeve 100 are relatively low. In this case, the friction between the metal links 211 and between the metal links 211 and the elastic sleeve 100 is relatively low, resulting in a relatively low stiffness of the variable stiffness structure 10.

[0066] When the surface roughness of the metal links 211 is set to 0.15-0.3 μm, the static friction coefficient between the metal links 211 is 0.3-0.4, and the dynamic friction coefficient between the metal links 211 and the elastic sleeve 100 is 0.25-0.32. At this point, the friction between the metal links 211 can reach its maximum value, resulting in the strongest friction wedge-locking effect between the metal links 211. Furthermore, the friction between the metal links 211 and the elastic sleeve 100 can also reach its maximum value, thereby maximizing the stiffness gain multiplier of the variable stiffness structure 10.

[0067] In order to achieve programmable stiffness adjustment of the variable stiffness structure 10, the present application further proposes an implementation method. Figure 1 ,like Figure 1 As shown, a first end cap 120 is provided at the end of the elastic tube sleeve 100, and the first end cap 120 is sealedly connected to the elastic tube sleeve 100. The end of the first end cap 120 facing away from the elastic tube sleeve 100 is connected to a pipe 300. The first end cap 120 is provided with a through hole (not shown in the figure), and the pipe 300 is connected to the elastic tube sleeve 100 through the through hole. The pipe 300 is used to connect to the negative pressure control device 400 to control the negative pressure state of the elastic tube sleeve 100 through the negative pressure control device 400.

[0068] The first end cap 120 can be made of engineering plastic PEEK (Polyetheretherketone) or titanium alloy. The first end cap 120 can be threadedly connected to the end of the elastic tube sleeve 100 or bonded to the end of the elastic tube sleeve 100 using an adhesive. To improve the sealing performance of the connection between the first end cap 120 and the elastic tube sleeve 100, a sealing ring or a conical sealing structure can be installed at the connection between the first end cap 120 and the elastic tube sleeve 100 to eliminate the gap between the first end cap 120 and the elastic tube sleeve 100 and achieve a long-term and reliable sealed connection.

[0069] In some embodiments, please refer to Figure 1 The first end of the elastic sleeve 100 can be provided with a second end cap 130, which can seal the first end of the elastic sleeve 100 to ensure the airtightness of the elastic sleeve 100. The second end cap 130 can be made of the same material as the first end cap 120.

[0070] The conduit 300 can be made of an elastic material, such as silicone. The negative pressure control device 400 can include a vacuum air pump and a pressure regulating valve, wherein the conduit 300, the pressure regulating valve, and the vacuum air pump are sequentially connected. Thus, when the pressure regulating valve is opened, the vacuum air pump can extract a preset volume of gas from the elastic tube sleeve 100 through the conduit 300 and the pressure regulating valve, thereby maintaining different negative pressure states within the elastic tube sleeve 100.

[0071] By controlling the vacuum air pump to extract the gas content from the elastic sleeve 100, the negative pressure within the elastic sleeve 100 can be adjusted, changing the radial pressure exerted by the elastic sleeve 100 on the multiple chain bundles 200, thereby adjusting the stiffness of the variable stiffness structure 10. When the negative pressure within the elastic sleeve 100 reaches the target negative pressure value, indicating that the variable stiffness structure 10 has achieved the target stiffness, the pressure regulating valve is closed. Due to the good airtightness between the first end cap 120 and the elastic sleeve 100, external gas is prevented from entering the elastic sleeve 100, thereby continuously maintaining the target stiffness of the variable stiffness structure 10.

[0072] In order to ensure that the overall structure of the variable stiffness structure 10 has greater stiffness, the present application further proposes an implementation method. Figure 3 ,like Figure 3 As shown, the end of each chain 210 is located at the same end as the end of the elastic tube sleeve 100, and a limiting member (not shown in the figure) is fixedly provided on the first end cover 120 toward one end of the elastic tube sleeve 100. The limiting member is used to pass through the end metal link 211 of each chain 210 in sequence to limit the axial displacement of each chain bundle 200 along the elastic tube sleeve 100.

[0073] The limiting member may be snap-fitted or threadedly connected to the first end cover 120 .

[0074] During repeated bending of the variable stiffness structure 10, friction between the elastic sleeve 100 and the chains 210 at the edge of each chain bundle 200 may cause each chain bundle 200 to displace axially along the elastic sleeve 100. The stopper limits the distance between the terminal metal link 211 of each chain 210 and the first end cap 120, thereby limiting the axial displacement of each chain 210 along the elastic sleeve 100. This prevents the head end of each chain bundle 200 from hanging loosely, ensures the stiffness of this portion of the variable stiffness structure 10, and ensures that the variable stiffness structure 10 as a whole has high stiffness.

[0075] In some embodiments, when the elastic sleeve 100 is made of silicone, the silicone can withstand repeated bending and vacuum pressure cycling, preventing deformation fatigue or cracking of the elastic sleeve 100, thereby ensuring the lifespan of the variable stiffness structure 10. Furthermore, silicone can withstand high-temperature, high-pressure sterilization and treatment with conventional sterilants, meeting the sterilization requirements of surgical instruments. For example, the elastic sleeve 100 can be made of medical silicone. Medical silicone has excellent biocompatibility and flexibility, allowing the outer diameter of the elastic sleeve 100 to be minimized while ensuring a certain compressive strength. This allows the variable stiffness structure 10 to be slender and flexible while providing an airtight seal.

[0076] The metal chain bundle 200 ensures that the variable stiffness structure 10 does not break or deform during repeated stiffness switching and load-bearing, maintaining consistent performance. The metal chain bundle 200 has a low coefficient of thermal expansion, resulting in negligible dimensional changes within the body temperature range, thus preventing vacuum relaxation or overtightening due to thermal effects. Furthermore, the silicone elastic tube sleeve 100 itself is transparent and shadowless, not interfering with imaging. The metal chain bundle 200 is opaque to X-rays, allowing the position and shape of the variable stiffness structure 10 to be clearly identified during intraoperative imaging, facilitating monitoring and positioning operations. Furthermore, when the metal chain links 211 are made of titanium steel, the chain bundle 200 is also a titanium steel chain bundle. The titanium steel chain bundle 200 combines high strength with corrosion resistance. Furthermore, the titanium steel chain bundle 200 is stable and non-toxic in the human body environment, does not release particulate impurities, and does not react harmfully with surrounding tissues.

[0077] In order to verify the stiffness gain multiple of the variable stiffness structure 10, this application uses a standard three-point bending test method to test and calibrate the stiffness of the variable stiffness structure 10. Specifically, the prepared variable stiffness structure 10 is selected and placed horizontally on two support points. The distance between the support points can be adjusted according to the effective length of the variable stiffness structure 10. For example, the distance between the support points can be set to 100mm. A pressure head is loaded at the center of the variable stiffness structure 10, and a vertical downward bending load is applied to the variable stiffness structure 10. The corresponding deflection displacement is recorded, and the force-displacement curves of the variable stiffness structure 10 in the initial soft state and the vacuum pressurized rigid state are respectively measured. The specific test and calibration steps are as follows:

[0078] Step S21: In the initial state (negative pressure in the elastic sleeve 100 is 0 kPa), both ends of the variable stiffness structure 10 are fixed to the support points with minimal preload, and the upper pressing head contacts the center of the variable stiffness structure 10 with zero load.

[0079] Step S22: Press the ram downward at a constant rate (e.g., 10 mm / min) to apply a bending force to the center of the variable stiffness structure 10, causing the variable stiffness structure 10 to produce a specified small deformation (e.g., deflection (the displacement of the variable stiffness structure 10 perpendicular to the axis under load) δ≈5 mm). The load F0 (the resistance generated by the variable stiffness structure 10) and deflection δ0 (initial state) at this time are recorded. After the load is removed, the variable stiffness structure 10 returns to its original shape to ensure that there is no residual deformation of the variable stiffness structure 10.

[0080] Figure 6 The figure shows a force-displacement diagram of the variable stiffness structure 10 when the negative pressure within the elastic sleeve 100 is 0 kPa. The horizontal axis represents the displacement (disp.) (mm) perpendicular to the axis of the variable stiffness structure 10 under load, and the vertical axis represents the resistance (force) (N) generated by the variable stiffness structure 10. As shown in the figure, when the variable stiffness structure 10 displaces 10 mm, the variable stiffness structure 10 generates a resistance of 0.01 N.

[0081] Step S23: Adjust the negative pressure within the elastic sleeve 100 of the variable stiffness structure 10 to the target negative pressure (e.g., -80 kPa), placing the variable stiffness structure 10 in a locked state with increased stiffness. Maintaining the negative pressure within the elastic sleeve 100, step S22 is repeated, and the required load F1 is recorded at the same deflection δ.

[0082] Figure 7 The force-displacement diagram of the variable stiffness structure 10 when the negative pressure in the elastic sleeve 100 is -80 kPa is shown. As shown in the diagram, when the variable stiffness structure 10 is displaced by 10 mm, the variable stiffness structure 10 can generate a resistance of 0.11 N.

[0083] Step S24: Calculate the bending stiffness K of the variable stiffness structure 10 under different negative pressures based on the force-displacement data obtained from the two tests. For example, when the negative pressure is 0 kPa, the bending stiffness K0 = 0.01 / 10 = 0.001 N / mm; when the negative pressure is -80 kPa, the bending stiffness K1 = 0.11 / 10 = 0.011 N / mm.

[0084] Step S25: The negative pressure of the elastic sleeve 100 is changed multiple times (for example, 0 kPa, -20 kPa, -40 kPa, -60 kPa, -80 kPa), and step S22 is repeated to measure the corresponding load values ​​of the variable stiffness structure 10 under different negative pressure states, and calculate the different stiffnesses K0, K1, ..., K of the variable stiffness structure 10. n Calculate the stiffness gain multiplier G and define G = K n / K0 is the ratio of the stiffness of the variable stiffness structure 10 after negative pressure is applied to its initial stiffness. For example, if the initial bending stiffness of the variable stiffness structure 10 is measured to be K0 = 0.001 N / mm and the bending stiffness of the variable stiffness structure 10 is measured to be K1 = 0.011 N / mm when the negative pressure is -80 kPa, then G = K1 / K0 = 11. Testing has shown that the initial bending stiffness of the variable stiffness structure 10 of this application is extremely low, and the stiffness gain under negative pressure can reach over 10 times.

[0085] See also Figure 8 , Figure 8 A schematic structural diagram of a soft robot provided in an embodiment of the present application is shown. As shown in the figure, the soft robot 1 includes a negative pressure source 20, a pressure regulating valve 30, and the variable stiffness structure 10 of the soft robot provided in any of the above embodiments. The pressure regulating valve 30 is connected to the negative pressure source 20 and the variable stiffness structure 10 of the soft robot through a first pipe 31 and a second pipe 32, respectively. The negative pressure source 20 is used to control the gas content within the elastic sleeve 100 through the pressure regulating valve 30, thereby controlling the negative pressure state within the elastic sleeve 100 and, in turn, controlling the stiffness of the variable stiffness structure 10 of the soft robot.

[0086] The first pipe 31 and the second pipe 32 can be made of silicone. The negative pressure source 20 can be a vacuum air pump for extracting gas from the elastic tube sleeve 100. The pressure regulating valve 30 can be an electric pressure regulating valve, which can adjust the air flow of the negative pressure source 20 by adjusting the valve core opening.

[0087] Specifically, when the negative pressure source 20 is operating and the pressure regulating valve 30 is open, the negative pressure source 20 can extract gas from the elastic tube sleeve 100 through the first pipe 31, the pressure regulating valve 30, and the second pipe 32. As the gas in the elastic tube sleeve 100 is extracted, the negative pressure in the elastic tube sleeve 100 continuously increases, and the stiffness of the variable stiffness structure 10 also continuously increases. When the stiffness of the variable stiffness structure 10 reaches the target stiffness, the pressure regulating valve 30 can be closed to prevent the negative pressure source 20 from further extracting gas from the elastic tube sleeve 100.

[0088] Preferably, please refer to Figure 6 The soft robot 1 may further include a pressure relief valve 40, which is in communication with the variable stiffness structure 10. For example, the pressure relief valve 40 may be in communication with the variable stiffness structure 10 via the second pipe 32. When it is necessary to reduce the stiffness of the variable stiffness structure 10 or restore the variable stiffness structure 10 to a soft state, the pressure relief valve 40 may be opened to allow external air to enter the elastic sleeve 100, thereby continuously reducing the negative pressure in the elastic sleeve 100, thereby continuously reducing the stiffness of the variable stiffness structure 10, and even restoring the variable stiffness structure 10 to its initial soft state.

[0089] Specifically, the stiffness adjustment of the variable stiffness structure 10 may include the following steps:

[0090] Step S1: In the initial state, the air pressure inside the elastic tube sleeve 100 is equal to the external air pressure (0 kPa), that is, the negative pressure inside the elastic tube sleeve 100 is 0 kPa. The multiple chains 210 of the multiple chain bundles 200 are loosely suspended in the elastic tube sleeve 100, and the metal links 211 of two adjacent chain bundles 200 are only slightly in contact with each other. The entire variable stiffness structure 10 is soft and bendable, showing extremely low initial bending stiffness.

[0091] Step S2: Activate the negative pressure source 20. This continuously extracts gas from the elastic sleeve 100 via the first conduit 31, the pressure regulating valve 30, and the second conduit 32, causing the negative pressure within the elastic sleeve 100 to drop below 0 kPa. At this point, the pressure differential between the ambient air pressure and the air pressure within the elastic sleeve 100 increases, increasing the negative pressure within the elastic sleeve 100 and causing the elastic sleeve 100 to contract radially, thereby continuously compressing the multiple chain bundles 200 within.

[0092] Step S3: As the negative pressure in the elastic sleeve 100 gradually increases, for example, to -20 to -40 kPa, the multiple chain bundles 200 are squeezed against each other by the radial pressure of the elastic sleeve 100. The contact area between the metal links 211 of two adjacent chain bundles 200 and between the metal link 211 of each chain bundle 200 and the inner wall of the elastic sleeve 100 begins to increase, and the friction between them increases significantly.

[0093] Step S4: When the negative pressure within the elastic sleeve 100 approaches the target negative pressure, for example, -80 kPa, the radial pressure on the multiple chain bundles 200 reaches its maximum. The contact area between the metal links 211 of two adjacent chain bundles 200, and between the metal links 211 of each chain bundle 200 and the inner wall of the elastic sleeve 100, reaches its maximum. This compresses the two adjacent chain bundles 200 into a stable supporting state, generating a frictional wedge-locking effect between them, thereby locking them together. While the elastic sleeve 100 maintains this negative pressure, the multiple chain bundles 200 transform from their initial, flexible structure into a rigid rod structure, significantly improving the bending stiffness of the variable stiffness structure 10 compared to its initial state.

[0094] Step S5: When the variable stiffness structure 10 needs to be restored to its soft state, the pressure relief valve 40 is opened, allowing the negative pressure within the elastic sleeve 100 to return to 0 kPa. This relieves the radial pressure on the multiple chain bundles 200, eliminates the frictional wedge-locking effect between the metal links 211 of adjacent chain bundles 200, and allows the chain bundles 200 to relax and separate under the action of gravity and elasticity, returning the variable stiffness structure 10 to its original soft and flexible state.

[0095] By repeating the above steps, the stiffness of the variable stiffness structure 10 can be adjusted to adapt to different working scenarios.

[0096] Preferably, please refer to Figure 1 The soft robot 1 may further include a sensor 50 and a controller 60. The sensor 50 may be a pressure sensor. The sensor 50 may be disposed within the elastic sleeve 100 or within the second conduit 32 to detect the pressure within the elastic sleeve 100. The controller 60 may be electrically connected to the negative pressure source 20, the pressure regulating valve 30, and the sensor 50, respectively.

[0097] Specifically, when the sensor 50 detects the pressure inside the elastic tube sleeve 100 and sends the pressure to the controller 60, the controller 60 can adjust the suction speed of the negative pressure source 20 and the valve core opening of the pressure regulating valve 30 according to the pressure, and control the volume of gas extracted by the negative pressure source 20 from the elastic tube sleeve 100 to accurately adjust the negative pressure inside the elastic tube sleeve 100 to the target negative pressure, thereby accurately controlling the stiffness of the variable stiffness structure 10.

[0098] The controller 60 may control the stiffness of the variable stiffness structure 10 by the following steps:

[0099] Step S11 : initializing the controller 60 and inputting a target negative pressure in the elastic sleeve 100 corresponding to the target stiffness of the variable stiffness structure 10 , for example, −60 kPa. The target pressure value corresponding to the target negative pressure is −60 kPa.

[0100] Step S12 : the sensor 50 collects the current actual pressure in the elastic tube sleeve 100 in real time, and transmits the current actual pressure to the controller 60 .

[0101] Step S13: The controller 60 compares the current actual pressure with the target pressure value, and calculates the pressure deviation ΔP between the current actual pressure and the target pressure value.

[0102] Step S14: The controller 60 executes a PID algorithm adjustment based on the pressure deviation ΔP. When the actual pressure within the elastic tube sleeve 100 is higher than the target pressure (insufficient vacuum), the controller 60 increases the power of the negative pressure source 20 or increases the valve opening of the pressure regulating valve 30 to increase the pumping speed, thereby reducing the pressure within the elastic tube sleeve 100. When the actual pressure is lower than the target pressure (excessive vacuum), the controller 60 reduces the power of the negative pressure source 20 or opens the pressure relief valve 40 to introduce appropriate amounts of external air, thereby increasing the pressure within the elastic tube sleeve 100.

[0103] Step S15: The controller 60 repeatedly executes steps S12-S14 above at a predetermined interval until the pressure deviation ΔP falls within a predetermined range. At this point, the negative pressure within the elastic sleeve 100 stabilizes at the target negative pressure, ensuring a constant stiffness of the variable stiffness structure 10 and enabling precise control of the stiffness of the variable stiffness structure 10.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A variable stiffness structure of a soft robot, characterized in that: The structure includes: elastic sleeves; A plurality of chain bundles are disposed in the elastic tube sleeve, each of the chain bundles comprising a plurality of chains stacked on each other, each of the chains comprising a plurality of interconnected metal links, each of the metal links being rotatable, a gap being provided between the plurality of metal links of two adjacent chains in each chain bundle, and two adjacent chain bundles being staggered so that each chain of each chain bundle fills part of the gap of the adjacent chain bundle; When the elastic sleeve is in a non-negative pressure state, the metal links of two adjacent chain bundles can slide relative to each other. When the elastic sleeve is in a negative pressure state, the metal links of two adjacent chain bundles abut against each other under the radial pressure of the elastic sleeve to be locked with each other.

2. The structure according to claim 1, characterized in that Each of the metal links includes a first metal link and a second metal link, both of which are annular structures. The first metal links and the second metal links of each chain are alternately arranged in pairs and are sequentially connected in a ring-like manner. The first metal link and the second metal link of each chain are perpendicular to each other and can rotate. In two adjacent chains of each chain bundle, the positions of the plurality of second metal links of one chain correspond to the positions of the plurality of second metal links of the other chain and are stacked on each other, so that the gap is formed between the plurality of first metal links of one chain and the plurality of first metal links of the other chain; The plurality of first metal links of each chain of each chain bundle fills a portion of the gaps between adjacent chain bundles.

3. The structure according to claim 2, characterized in that The two stacked second metal chain links of two adjacent chains of each chain bundle form an integral structure.

4. The structure according to claim 2, characterized in that In each of the chains, there is a gap between two adjacent second metal links connected to the same first metal link collar, and there is a gap between two adjacent first metal links connected to the same second metal link collar.

5. The structure according to claim 1, characterized in that When the elastic tube sleeve is in a non-negative pressure state, there is a gap between the chain at the edge of each chain bundle and the elastic tube sleeve, and the ratio of the projected area of ​​multiple chain bundles on the radial plane of the elastic tube sleeve to the inner diameter cross-sectional area of ​​the elastic tube sleeve is 95% to 105%.

6. The structure according to claim 1, characterized in that The roughness of the surface of the metal chain link is 0.15-0.3 μm, the static friction coefficient between the plurality of metal chain links is 0.3-0.4, and the dynamic friction coefficient between the metal chain link and the elastic tube sleeve is 0.25-0.

32.

7. The structure according to claim 1, characterized in that An end cap is provided at the end of the elastic tube sleeve, and the end cap is sealed with the elastic tube sleeve. A pipe is connected to the end of the end cap facing away from the elastic tube sleeve. The end cap is provided with a through hole, and the pipe is connected to the elastic tube sleeve through the through hole. The pipe is used to connect to a negative pressure control device to control the negative pressure state of the elastic tube sleeve through the negative pressure control device.

8. The structure according to claim 7, characterized in that The end of each chain is located at the same end as the end of the elastic tube sleeve, and a limit piece is fixedly provided on the end cover toward one end of the elastic tube sleeve. The limit piece is used to pass through the end metal link of each chain in sequence to limit the axial displacement of each chain bundle along the elastic tube sleeve.

9. The structure according to claim 1, characterized in that The elastic tube sleeve is made of silicone, and the metal chain link is made of titanium steel.

10. A soft robot, characterized in that: The soft robot comprises a negative pressure source, a pressure regulating valve and a variable stiffness structure of the soft robot according to any one of claims 1 to 9; The pressure regulating valve is connected to the negative pressure source and the variable stiffness structure of the soft robot through a first pipe and a second pipe respectively. The negative pressure source is used to control the gas content in the elastic tube sleeve through the pressure regulating valve to control the negative pressure state in the elastic tube sleeve, and then control the stiffness of the variable stiffness structure of the soft robot.

11. The soft robot according to claim 10, characterized in that: The soft robot further includes a sensor and a controller, wherein the sensor is disposed in the second pipe, and the controller is electrically connected to the negative pressure source, the sensor, and the pressure regulating valve respectively; The sensor is used to detect the pressure in the elastic sleeve and send the pressure to the controller; The controller is used to receive the pressure and control the operation of the negative pressure source and the pressure regulating valve according to the pressure, so as to adjust the negative pressure in the elastic tube sleeve to a target negative pressure.

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