Quick response flexible driver based on natural rubber film instability expansion

Abstract

The invention discloses a quick-response flexible driver based on instability expansion of a natural rubber film. The quick-response flexible driver based on natural rubber film instability expansion comprises a plurality of dual-mode flexible rotating joints which are connected in series. Wherein each dual-mode flexible rotary joint comprises an expansion cavity assembly, and when the quick response flexible driver based on the instability expansion of the natural rubber film is in an initial state, the expansion cavity assembly is connected with the expansion cavity assembly; the distance between the expansion cavity assembly of any middle joint and other adjacent dual-mode flexible rotating joints is the expansion height reached by the expansion cavity assembly at the moment of instability. The flexible rotary joint has two motion modes of continuous controllable rotation and high-speed unstable rotation in the same structure, different actuation responses can be achieved under different working conditions, and the speed adjusting range can reach two orders of magnitude.

Description

Technical Field

[0001] This application relates to the field of flexible actuator technology, specifically to a fast-response flexible actuator based on the unstable expansion of a natural rubber membrane. Background Technology

[0002] Flexible actuators are core execution units in soft robots, minimally invasive medical devices, and bionic mechanisms. Existing flexible actuation methods mainly include pneumatic, hydraulic, dielectric elastomer, shape memory materials, and multistable mechanisms. Among these, conventional pneumatic actuators have a simple structure but limited response speed during expansion, making them unsuitable for transient applications such as high-speed grasping and rapid steering.

[0003] Biological systems in nature that rely on structural instability to achieve high-speed propulsion are widespread, such as the rapid closing of the Venus flytrap and the instantaneous bending of the hummingbird's mouthparts. These systems share the common characteristic of utilizing the nonlinear behavior of materials or geometry to produce abrupt velocity changes under critical conditions. However, the utilization of instability behavior in artificially driven systems remains very limited, mainly due to the following reasons: (1) Instability is often accompanied by uncontrollable deformation paths, which can easily lead to structural damage; (2) The deformation path is determined by the steady-state geometry, and its state switching has abrupt characteristics, making it impossible to achieve a continuous and controllable deformation process; (3) Dynamically adjusting the jump path between steady states usually requires redesign of the geometry and lacks a driving mechanism that can switch between "instability" and "continuous adjustment".

[0004] In summary, existing technologies urgently need a comprehensive technology that can utilize instability to achieve high-speed response, while also possessing continuous controllability and seamless switching of motion modes. This technology should have the advantages of high-speed driving capability, continuous adjustment capability, simple structure, long lifespan, and ease of manufacturing.

[0005] To overcome the above-mentioned technical shortcomings, this invention proposes a flexible actuator based on the unstable expansion of a natural rubber membrane. By introducing a bidirectional stretchable fiber confinement layer, utilizing the nonlinear expansion characteristics of the natural rubber membrane and the expansion offset effect caused by the non-uniform aspect ratio structure, and through a reasonable structural design layout, the flexible joint not only has high-speed response characteristics during movement, but also has in-situ state switching, continuous controllability of the drive, and designability. This solves the problems of existing multi-stable structures being unable to achieve continuous controllable actuation, the low response speed of traditional pneumatic drives, and the uncontrollability of unstable drives. Summary of the Invention

[0006] The purpose of this invention is to provide a fast-response flexible actuator based on the unstable expansion of a natural rubber membrane to at least solve one of the above-mentioned technical problems.

[0007] One aspect of the present invention provides a fast-response flexible actuator based on the unstable expansion of a natural rubber membrane. The fast-response flexible actuator includes multiple dual-mode flexible rotary joints connected in series, wherein the first dual-mode flexible rotary joint is called the head joint, the tail joint is called the tail joint, and the other dual-mode flexible rotary joints are called intermediate joints; wherein... Each of the dual-mode flexible rotary joints includes an expansion cavity assembly. When the fast-response flexible actuator based on the instability expansion of a natural rubber membrane is in its initial state, the distance between the expansion cavity assembly of any intermediate joint and other adjacent dual-mode flexible rotary joints is the expansion height reached by the expansion cavity assembly at the moment of instability.

[0008] Optionally, the dual-mode flexible rotary joint further includes: The base has a first mounting hole and a second mounting hole. Each of the dual-mode flexible rotary joints has four expansion cavity assemblies, two of which are disposed in the first mounting hole and the other two are disposed in the second mounting hole. Two expansion cavity assemblies are disposed within the first mounting hole. One expansion cavity assembly expands in a first direction during expansion, and the other expansion cavity assembly expands in a second direction during expansion. The first direction and the second direction are opposite to each other.

[0009] Optionally, the fast-response flexible actuator based on the instability expansion of a natural rubber membrane further includes: A gripper, wherein the gripper is connected to a tail end joint via a tail joint clamp; A top clamp, which is connected to the head joint via a head joint clamp.

[0010] Optionally, the fast-response flexible actuator based on the instability expansion of a natural rubber membrane includes: An inter-joint clamp, one end of which is connected to a dual-mode flexible rotary joint and the other end of which is connected to another dual-mode flexible rotary joint, wherein the two dual-mode flexible rotary joints connected by the same inter-joint clamp are adjacent dual-mode flexible rotary joints.

[0011] Optionally, the fast-response flexible actuator based on the unstable expansion of a natural rubber membrane further includes an inflation device and an inflation tube, wherein the output end of the inflation device is connected to the inflation tube, and the other end of the inflation tube is connected to each expansion cavity assembly.

[0012] Optionally, the expansion cavity assembly includes: A rubber expansion film layer, wherein an air inlet is provided on the rubber expansion film layer and the air inlet is connected to an inflation pipe; A biaxially oriented stretchable single-layer fiber, wherein the biaxially oriented stretchable single-layer fiber is connected to a rubber expansion film layer.

[0013] Optionally, the expansion cavity assembly further includes: A silicone sealing ring, one side of which is connected to the base and the other side of which is connected to one side of the rubber expansion film layer; A natural rubber layer clamp, wherein one side of the natural rubber layer is connected to the other side of the rubber expansion film layer, and the other side of the natural rubber layer is connected to one side of the biaxially oriented stretchable single-layer fiber; A fiber layer clamp, one side of which is connected to the other side of the bidirectional stretchable single-layer fiber.

[0014] Optionally, the gripper includes: A fixing frame, wherein a first connecting plate is provided at one end of the fixing frame and a second connecting plate is provided at the other end; A movable frame assembly is disposed on the fixed frame and between the first connecting plate and the second connecting plate; A first side drive cavity is disposed on the side of the first connecting plate facing the movable frame assembly, and a first gap exists between the movable frame assembly and the first side drive cavity. A second side drive cavity is disposed on the side of the second connecting plate facing the movable frame assembly, and a first gap exists between the movable frame assembly and the second side drive cavity; wherein the distance of the first gap is equal to the expansion height reached by the first side drive cavity at the moment of instability; and the distance of the second gap is equal to the expansion height reached by the second side drive cavity at the moment of instability.

[0015] Optionally, the movable frame assembly is connected to the fixed frame via a guide rail slider. The movable frame assembly includes: A first clamping finger, wherein a first rectangular expansion cavity assembly is provided on the first clamping finger; The second clamping finger is provided with a second rectangular expansion cavity assembly; wherein... The first rectangular expansion cavity assembly and the second rectangular expansion cavity assembly are arranged opposite to each other.

[0016] In the initial state of the fast-response flexible actuator based on the unstable expansion of a natural rubber membrane, the distance between the expansion cavity assembly of any intermediate joint and other adjacent dual-mode flexible rotary joints is the expansion height reached by the expansion cavity assembly at the moment of instability. Therefore, when a single air cavity is pressurized to the instability point, its expansion height is exactly equal to the joint pitch. Thus, after the sudden jump due to instability, the expansion cavity only makes slight contact with the adjacent intersegment, and the joint does not rotate immediately. After further pressurization into the continuous expansion phase, the cavity protrudes further outward, forming an offset thrust between the segments, causing the joint to produce continuous and adjustable bending, achieving smooth rotational output. Conversely, if the symmetrical air cavities on both sides are pressurized simultaneously, triggering instability at the same moment, the rapid jump expansion of the two cavities will instantaneously generate a large unbalanced torque, causing the joint to immediately undergo high-speed transient rotation. Based on this mechanism, the flexible rotary joint has both "continuous controllable rotation" and "high-speed unstable rotation" motion modes in the same structure, and can achieve different actuation responses under different working conditions, with a speed adjustment range of up to two orders of magnitude. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a fast-response flexible actuator based on the unstable expansion of a natural rubber membrane according to an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the overall structure of a dual-mode flexible rotary joint according to an embodiment of this application.

[0019] Figure 3 This is a cross-sectional schematic diagram of a dual-mode flexible rotary joint according to an embodiment of this application.

[0020] Figure 4 This is a schematic diagram of the structure of a gripper according to an embodiment of this application.

[0021] Figure 5 This is a schematic diagram of the structure of a fixing frame according to an embodiment of this application.

[0022] Figure 6 This is a cross-sectional schematic diagram of a movable frame assembly according to an embodiment of this application.

[0023] Figure 7 This is a schematic diagram of the structure of the first clamping finger according to an embodiment of this application.

[0024] Figure 8 This is a schematic diagram illustrating the principle of a fast-response flexible actuator based on the unstable expansion of a natural rubber membrane, according to an embodiment of this application.

[0025] Figure 9 This is a schematic diagram illustrating the expansion characteristics of natural rubber and the dual motion mode principle according to an embodiment of this application.

[0026] Figure 10 This is a schematic diagram illustrating the expansion and contact characteristics of a natural rubber film under geometrically asymmetric boundary conditions according to an embodiment of this application.

[0027] Figure label: 1. Dual-mode flexible rotary joint; 11. Base; 2. Gripper; 3. Top clamp; 4. Inter-joint clamp; 12. Rubber expansion membrane layer; 121. Air inlet; 13. Bidirectional stretchable single-layer fiber; 14. Silicone sealing ring; 15. Natural rubber layer clamp; 16. Fiber layer clamp; 21. Fixing frame; 211. First connecting plate; 212. Second connecting plate; 22. Movable frame assembly; 23. First side drive cavity; 24. Second side drive cavity; 241. First gripping finger; 2411. First rectangular expansion cavity assembly; 242. Second gripping finger; 2412. Second rectangular expansion cavity assembly. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0029] like Figure 1 The fast-response flexible actuator based on the instability and expansion of a natural rubber membrane shown includes multiple dual-mode flexible rotary joints 1 connected in series. The first dual-mode flexible rotary joint 1 is called the head joint, the tail joint is called the tail joint, and the other dual-mode flexible rotary joints 1 are called intermediate joints. Each of the aforementioned dual-mode flexible rotary joints 1 includes an expansion cavity assembly, in which the fast-response flexible actuator based on the instability expansion of a natural rubber membrane is in its initial state (see...). Figure 1 , Figure 1 The state shown is the initial state, that is, the state in which no gas is filled and deformation occurs. The distance between the expansion cavity assembly of any intermediate joint and other adjacent dual-mode flexible rotary joints is the expansion height reached by the expansion cavity assembly at the moment of instability.

[0030] See Figure 2as well as Figure 3 In this embodiment, the dual-mode flexible rotary joint 1 further includes a base 11, on which a first mounting hole and a second mounting hole are provided; Each dual-mode flexible rotary joint has four expansion cavity assemblies, two of which are located in the first mounting hole and the other two are located in the second mounting hole. Two expansion cavity assemblies are disposed within the first mounting hole. One expansion cavity assembly expands in a first direction during expansion, and the other expansion cavity assembly expands in a second direction during expansion. The first direction and the second direction are opposite to each other.

[0031] In this embodiment, the fast-response flexible actuator based on the instability and expansion of a natural rubber membrane further includes a gripper 2, a top clamp 3, and an inter-joint clamp 4, wherein, The gripper 2 is connected to the tail joint via a tail joint clamp; The top clamp 3 is connected to the head joint via the head joint clamp.

[0032] In this embodiment, the fast-response flexible actuator based on the unstable expansion of a natural rubber membrane includes: One end of the inter-joint clamp 4 is connected to a dual-mode flexible rotary joint 1, and the other end is connected to another dual-mode flexible rotary joint 1. The two dual-mode flexible rotary joints connected by the same inter-joint clamp 4 are adjacent dual-mode flexible rotary joints.

[0033] In this embodiment, the fast-response flexible actuator based on the unstable expansion of natural rubber membrane further includes an inflation device and an inflation tube. The output end of the inflation device is connected to the inflation tube, and the other end of the inflation tube is connected to each expansion cavity assembly.

[0034] See Figure 2 as well as Figure 3 In this embodiment, the expansion cavity assembly includes a rubber expansion film layer 12, a biaxially stretchable single-layer fiber 13, a silicone sealing ring 14, a natural rubber layer clamp 15, and a fiber layer clamp 16, wherein... An air inlet 121 is provided on the rubber expansion membrane layer 12, and the air inlet 121 is connected to the inflation tube; The bidirectional stretchable single-layer fiber 13 is connected to the rubber expansion membrane layer 12.

[0035] One side of the silicone sealing ring 14 is connected to the base 11, and the other side is connected to one side of the rubber expansion film layer 12; One side of the natural rubber layer clamp 15 is connected to the other side of the rubber expansion film layer 12, and the other side of the natural rubber layer clamp 15 is connected to one side of the biaxially stretchable single-layer fiber 13. One side of the fiber layer clamp 16 is connected to the other side of the bidirectional stretchable single-layer fiber 13.

[0036] The reasons for the above design in this embodiment are as follows: The natural rubber layer is circumferentially fixed by a natural rubber layer clamp with a circular opening structure. This structure can form axisymmetric boundary constraints during the expansion process before and after instability, effectively avoiding stress concentration and asymmetric expansion caused by boundary geometric discontinuities or sudden changes in local stiffness, thereby improving the consistency and repeatability of the rubber membrane's expansion at the moment of instability. This design gives the rubber membrane good stability in expansion height at the moment of instability, providing a foundation for the subsequent structural design of accurately matching this expansion height to the joint pitch (i.e., the expansion distance hs), which is one of the key prerequisites for realizing dual-motion mode switchable drive.

[0037] Because the natural rubber diaphragm is relatively thin, its local strain increases significantly during instability and sudden jumps. Directly relying on the diaphragm layer to seal against a rigid structure can easily create micro-gaps and lead to gas leakage, thus affecting the consistency of the instability trigger pressure and expansion height. Introducing a silicone sealing ring between the rubber diaphragm and the base significantly reduces gas leakage during the actuation process through a flexible interface. Furthermore, it acts as a buffer during the instability and sudden jump phase, preventing damage to the edges of the rubber diaphragm from rigid contact. This structure effectively improves the sealing stability and reliability of the expansion chamber under repeated high-speed instability actuation, ensuring the repeatability of the actuation performance.

[0038] To further improve the designability and consistency of the natural rubber membrane's unstable expansion process, a biaxially stretchable single-layer fiber confinement layer was applied to the outside of the rubber expansion membrane. Unlike the fiber coating, which only serves a protective function, the geometry and effective confinement range of this fiber layer were considered as important design parameters for the actuator.

[0039] In this embodiment, the geometric dimensions and effective constraint range of the fiber layer are determined as follows: During the free inflation and expansion of a circular natural rubber membrane, the membrane stretch ratio It can be calculated using the following formula:

[0040] Where the original radius of the circular membrane is After the membrane expands, the arc length from the center to the boundary is... The expansion height is The membrane stress-tensile relationship can be represented by the incompressible Neo-Hookean model, i.e.

[0041] in This is the shear modulus.

[0042] Under the constraint of the upper biaxially oriented stretchable fiber, its stress can be equivalent to,

[0043] in The equivalent average stiffness of the biaxially oriented stretchable fiber layer can be calculated using the following formula:

[0044] in This represents the average spacing between radial fibers. This represents the average spacing between circumferential fibers. This refers to the Young's modulus of the fiber. Let be the cross-sectional area of ​​the fiber. This can be obtained from the force balance relationship on the membrane.

[0045] The expansion height of the instability point can be calculated using the following formula:

[0046] Setting it to zero, we get:

[0047] Maximum expansion height of the driver The effective constraint range of the fiber is determined by the maximum tensile ratio of the fiber layer. ,as follows

[0048] The above calculation process can determine the buckling height of the actuator under fiber layer constraints within the given geometric dimensions and effective constraint range of the fiber layer. and maximum expansion height .

[0049] In this embodiment, by adjusting the coverage area, effective stretch length, and boundary fixing position of the biaxially stretchable fiber layer, the maximum expansion height after instability and sudden jump can be further limited and adjusted without changing the material parameters of the rubber membrane. After instability, the fiber layer gradually enters a stressed state, forming a flexible constraint on the outward bulging deformation of the rubber membrane, thus transforming the expansion process from being entirely material-driven to being controlled collaboratively by the material and structure.

[0050] This design allows the expansion height hs after instability to be structurally controlled not only by the rubber membrane thickness or pressure conditions, but also by the fiber layer size parameters, thus significantly improving the repeatability and designability of the instability expansion height. This feature provides crucial support for structural layouts that precisely match the joint pitch to the instability expansion height.

[0051] Furthermore, since the fiber layer is a bidirectional stretchable structure, it can maintain a relatively uniform stress distribution while limiting the maximum expansion height, without introducing obvious local stiffness abrupt changes or stress concentration. Experimental results show that this design further improves the service life of the rubber membrane under high strain cyclic conditions while ensuring the driving response speed.

[0052] See Figure 4 , Figure 5 , Figure 6 In this embodiment, the gripper 2 includes a fixed frame 21, a movable frame assembly 22, a first side driving cavity 23, and a second side driving cavity 24, wherein... In this embodiment, the fixing frame includes a horizontal plate, a first connecting plate 211, and a second connecting plate 212; A first connecting plate 211 is provided at one end of the horizontal plate, and a second connecting plate 212 is provided at the other end; The movable frame assembly 22 is mounted on the fixed frame 21 and positioned between the first connecting plate 211 and the second connecting plate 212; The first side drive cavity 23 is disposed on the side of the first connecting plate 211 facing the movable frame assembly 22, and there is a first gap between the movable frame assembly 22 and the first side drive cavity 23. The second side drive cavity 24 is disposed on the side of the second connecting plate 212 facing the movable frame assembly 22, and there is a first gap between the movable frame assembly 22 and the second side drive cavity 24; wherein, the distance of the first gap is equal to the expansion height reached by the first side drive cavity at the moment of instability; the distance of the second gap is equal to the expansion height reached by the second side drive cavity at the moment of instability.

[0053] In this embodiment, the movable frame assembly and the fixed frame are connected by a guide rail slider; wherein, a slide rail is provided on the horizontal plate, and a slider is provided on the movable frame assembly.

[0054] The movable frame assembly 24 includes a first clamping finger 241 and a second clamping finger 242, wherein the first clamping finger 241 is connected to the horizontal plate via a first slider, and the second clamping finger 242 is connected to the horizontal plate via a second slider.

[0055] The first clamping finger 241 is provided with a first rectangular expansion cavity assembly 2411; The second clamping finger 242 is provided with a second rectangular expansion cavity assembly 2412; wherein, the first rectangular expansion cavity assembly 2411 and the second rectangular expansion cavity assembly 2412 are disposed opposite to each other.

[0056] In this embodiment, the first clamping finger 241 includes a first clamping finger horizontal plate, which is connected to a first slider. One end of the first clamping finger horizontal plate is connected to a first rectangular expansion cavity assembly 2411, and the other end of the first clamping finger horizontal plate is connected to a first clamping finger vertical plate. The first clamping finger vertical plate is provided with a first clamping finger driving cavity with the same structure as the first side driving cavity 23, and the first side driving cavity 23 and the first clamping finger driving cavity are arranged opposite to each other.

[0057] In this embodiment, the second clamping finger includes a second clamping finger horizontal plate, which is connected to the second slider. One end of the second clamping finger horizontal plate is connected to the second rectangular expansion cavity assembly, and the other end of the second clamping finger horizontal plate is connected to the second clamping finger vertical plate. The second clamping finger vertical plate is provided with a second clamping finger driving cavity with the same structure as the second side driving cavity 23, and the second side driving cavity 23 and the second clamping finger driving cavity are arranged opposite to each other.

[0058] In this embodiment, all devices capable of expansion (such as the first rectangular expansion cavity assembly, the second rectangular expansion cavity assembly, the first side drive cavity, the second side drive cavity, and the dual-mode flexible rotary joint) are controlled by inflation, which will not be described in detail here.

[0059] In this embodiment, the natural rubber membrane exhibits typical nonlinear expansion instability characteristics under uniform air pressure, and its response curve is as follows: Figure 9 As shown, when the internal air pressure gradually increases, the rubber membrane undergoes only slow and limited deformation in the initial stage; when the air pressure rises to a certain critical point, the structure suddenly enters an unstable state, and the membrane will produce instantaneous and violent jump expansion. The instability triggering air pressure is directly proportional to the ratio of the pressure radius and the thickness.

[0060] Experiments show that natural rubber membranes undergo almost no significant deformation before the instability point, while even a tiny pressure difference at the critical point can cause significant expansion. After the sudden instability jump, the membrane's expansion behavior does not stop, but rather enters a continuous and controllable expansion phase as the air pressure continues to increase. Therefore, the entire process can be understood as consisting of two stages: "rapid instability expansion" and "continuous and gradual expansion," with the expansion height at the instant of instability denoted as hs.

[0061] The physical image of this application is as follows: Figure 8 As shown, in this embodiment, a number of dual-mode flexible rotary joints 1 are arranged in series based on a fast-response flexible actuator that utilizes the instability and expansion of a natural rubber membrane, and a flexible gripping mechanism is integrated at the end. The dual-mode flexible rotary joint 1 has the following structure: Figure 2 , Figure 3As shown, it includes four independently supplyable expansion chamber assemblies. Each expansion chamber assembly consists of a natural rubber expansion membrane layer, a bidirectional stretchable single-layer fiber restraint layer, a silicone sealing ring, and upper and lower clamps. The fiber layer is arranged in a bidirectional stretchable pattern, which restrains the rubber layer and provides tensile strength. Under repeated instability driving, it can significantly reduce local strain concentration and improve the membrane life.

[0062] The key design feature of the dual-mode flexible rotary joint lies in the precise setting of the pitch between the expansion chamber components of adjacent dual-mode flexible rotary joints to the expansion height hs reached by the rubber diaphragm at the moment of instability. Due to this structural relationship, when a single air chamber is pressurized to the instability point, its expansion height is exactly equal to the joint pitch. Therefore, after the instability jump, the expansion chamber only makes slight contact with the adjacent segment, and the joint does not rotate immediately. After further pressurization into the continuous expansion section, the chamber bulges outward further, forming an offset thrust between the segments, causing the joint to produce continuous and adjustable bending, achieving smooth rotational output. Conversely, if the symmetrical air chambers on both sides are pressurized simultaneously, triggering instability at the same moment, the rapid jump expansion of the two chambers will instantaneously generate a large unbalanced torque, causing the joint to immediately undergo high-speed transient rotation. Based on this mechanism, the flexible rotary joint possesses both "continuous controllable rotation" and "high-speed unstable rotation" motion modes in the same structure, enabling different actuation responses under different working conditions, with a speed adjustment range of up to two orders of magnitude.

[0063] In this embodiment, the bidirectional stretchable single-layer fiber confinement layer not only enhances the structural stability of the rubber membrane under high strain conditions, but its geometric dimensions and effective confinement range are also used as important structural parameters for regulating the expansion behavior after instability. By adjusting the coverage area, boundary fixing position, and stretchable length of the fiber layer, the maximum expansion height after the sudden instability jump can be further limited and adjusted without changing the intrinsic properties of the rubber membrane material. Therefore, the expansion height after the instantaneous instability is no longer entirely determined by material parameters or driving pressure, but is transformed into a geometric quantity that can be precisely controlled through structural design, thereby significantly improving the parameter consistency and repeatability of the actuator across different joints.

[0064] The end effector utilizes the buckling expansion characteristics of a natural rubber membrane under geometrically asymmetric boundary conditions. Specifically, when a uniform internal pressure load is applied to a natural rubber membrane with non-uniform boundary lengths, the membrane undergoes buckling and abrupt expansion only at its geometric center during the initial buckling phase, rather than buckling simultaneously across the entire membrane surface. Figure 10 )

[0065] When a rubber diaphragm comes into contact with an external target during its unstable expansion, the local constraint of the contact area on the diaphragm surface alters the original stress distribution, causing the instability trigger point to shift from its original geometric center to the non-contact area, thus creating a dynamic migration phenomenon of the instability point. This migration process is accompanied by a spatial shift in the maximum expansion area of ​​the rubber diaphragm, causing the diaphragm to automatically expand further towards the unconstrained direction under continuous air supply conditions.

[0066] Based on the above mechanism, this application employs a geometrically asymmetric natural rubber expansion cavity structure in the flexible end effector finger. This allows the flexible finger to adaptively adjust its expansion center upon initial contact with the object being grasped in high-dynamic grasping scenarios, without requiring additional sensing or control. This is achieved through an instability point transfer mechanism, enabling the finger to rapidly form a wrapping closure along the target object's surface. This structure enables adaptive grasping of targets of different sizes and shapes, significantly improving the stability and success rate of the flexible end effector under high-speed grasping conditions.

[0067] Experimental verification shows that the biaxially stretchable single-layer fiber structure used in this application can significantly enhance the service life of the rubber layer under high strain cycles; the designed flexible rotary joint can still reliably trigger instability and achieve rapid rotation under an external load of 2.3 kg (353 times the structure's own weight), indicating that the structure has high load-bearing capacity, excellent response speed and long-term durability.

[0068] See Figure 4 , Figure 5 , Figure 6 This application also develops a dual-mode gripper 2 for rapid closure and compliant adjustment of an end effector. The gripper 2 includes a fixed frame 21 and a movable frame assembly 22, connected by a guide rail slider. Similar to the aforementioned dual-mode flexible rotary joint, the first-side drive cavity 23 and the second-side drive cavity 24 each consist of a natural rubber expansion film layer, a bidirectional stretchable single-layer fiber restraint layer, a silicone sealing ring, and upper and lower clamps. Because the expansion height of the drive cavity at the moment of instability is limited to the pitch range, when one side of the air cavity is in the continuous expansion phase, the slider achieves a smooth and controllable linear output along the linear guide rail; however, when both sides of the air cavity simultaneously reach the instability critical point, the high-speed volume change caused by the sudden instability jump directly drives the slider to produce rapid transient movement. Therefore, this flexible linear joint possesses both "continuous and controllable linear motion" and "high-speed unstable linear motion" modes within the same structure, and can adjust the closing speed and dynamic response of the flexible finger within a wide range according to the air supply strategy.

[0069] See Figure 7In the flexible distal phalanx portion, this application provides a first gripping finger 241 and a second gripping finger 242. The first gripping finger 241 is provided with a first rectangular expansion cavity assembly 2411; the second gripping finger 242 is provided with a second rectangular expansion cavity assembly 2412. The first rectangular expansion cavity assembly 2411 and the second rectangular expansion cavity assembly 2412 have the same structure. The following description uses the first rectangular expansion cavity assembly 2411 as an example: The first rectangular expansion cavity assembly 2411 is a rectangular expansion cavity with an aspect ratio of 3:1, and its structural schematic is shown below. Figure 8 As shown, it is also composed of a natural rubber expansion membrane layer, a biaxially stretchable single-layer fiber restraint layer, a silicone sealing ring, and upper and lower clamps. Because this rectangular cavity has non-uniform boundary lengths, its initial instability position is at the center of the natural rubber membrane. However, under the influence of external contact forces, the instability expansion position shifts. When a finger contacts the target object, this geometric asymmetry and contact force work together to cause the expansion center to adaptively move along the target object contact, thus forming a rapid enveloping closure under instability-driven conditions. Based on this mechanism, this application proposes a highly dynamic response flexible gripper that can achieve adaptive and rapid enveloping gripping on target objects of different sizes and shapes, with an overall gripping time controlled within 92ms, significantly improving the transient response capability and gripping stability of the flexible end effector.

[0070] In this embodiment, the composition (rubber expansion film layer, air inlet, bidirectional stretchable single-layer fiber, silicone sealing ring, natural rubber layer clamp, fiber layer clamp) of the first side driving cavity, the second side driving cavity, the first rectangular expansion cavity assembly, the second rectangular expansion cavity assembly, and the expansion cavity assembly are all the same, and the arrangement of each component is not repeated here.

[0071] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A fast-response flexible actuator based on the instability expansion of a natural rubber membrane, characterized in that, The fast-response flexible actuator based on the instability expansion of a natural rubber membrane includes multiple dual-mode flexible rotary joints (1) connected in series. The dual-mode flexible rotary joint (1) located at the front is called the head joint, the dual-mode flexible rotary joint located at the tail is called the tail joint, and the other dual-mode flexible rotary joints (1) are called intermediate joints. Each of the dual-mode flexible rotary joints (1) includes an expansion cavity assembly. When the fast-response flexible actuator based on the instability expansion of the natural rubber membrane is in its initial state, the distance between the expansion cavity assembly of any intermediate joint and other adjacent dual-mode flexible rotary joints is the expansion height reached by the expansion cavity assembly at the moment of instability.

2. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 1, characterized in that, The dual-mode flexible rotary joint (1) further includes: The base (11) is provided with a first mounting hole and a second mounting hole; Each of the dual-mode flexible rotary joints has four expansion cavity assemblies, two of which are disposed in the first mounting hole and the other two are disposed in the second mounting hole. Two expansion cavity assemblies are disposed within the first mounting hole. One expansion cavity assembly expands in a first direction during expansion, and the other expansion cavity assembly expands in a second direction during expansion. The first direction and the second direction are opposite to each other.

3. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 2, characterized in that, The fast-response flexible actuator based on the instability expansion of a natural rubber membrane further includes: The gripper (2) is connected to the tail joint via a tail joint clamp; The top clamp (3) is connected to the head joint via the head joint clamp.

4. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 3, characterized in that, The fast-response flexible actuator based on the instability expansion of a natural rubber membrane includes: Inter-joint clamp (4), one end of which is connected to a dual-mode flexible rotary joint (1) and the other end is connected to another dual-mode flexible rotary joint (1). The two dual-mode flexible rotary joints connected by the same inter-joint clamp (4) are adjacent dual-mode flexible rotary joints.

5. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 2, characterized in that, The fast-response flexible actuator based on the unstable expansion of natural rubber membrane further includes an inflation device and an inflation tube. The output end of the inflation device is connected to the inflation tube, and the other end of the inflation tube is connected to each expansion cavity assembly.

6. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 5, characterized in that, The expansion cavity assembly includes: A rubber expansion film layer (12) is provided with an air inlet (121), which is connected to an inflation pipe; A biaxially oriented stretchable single-layer fiber (13) is connected to a rubber expansion membrane layer (12).

7. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 6, characterized in that, The expansion cavity assembly further includes: A silicone sealing ring (14) is connected to the base (11) on one side and to one side of the rubber expansion film layer (12) on the other side. A natural rubber layer clamp (15) is provided, with one side of the natural rubber layer clamp (15) connected to the other side of the rubber expansion film layer (12), and the other side of the natural rubber layer clamp (15) connected to one side of the biaxially stretchable single-layer fiber (13). A fiber layer clamp (16) is provided, one side of which is connected to the other side of the biaxially stretchable single-layer fiber (13).

8. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 3, characterized in that, The gripper (2) includes: A fixing frame (21) is provided with a first connecting plate (211) at one end and a second connecting plate (212) at the other end. A movable frame assembly (22) is disposed on the fixed frame (21) and between the first connecting plate (211) and the second connecting plate (212); A first side drive cavity (23) is disposed on the side of the first connecting plate (211) facing the movable frame assembly (22), and there is a first gap between the movable frame assembly (22) and the first side drive cavity (23). The second side drive cavity (24) is disposed on the side of the second connecting plate (212) facing the movable frame assembly (22), and there is a first gap between the movable frame assembly (22) and the second side drive cavity (24); wherein the distance of the first gap is equal to the expansion height reached by the first side drive cavity at the moment of instability; and the distance of the second gap is equal to the expansion height reached by the second side drive cavity at the moment of instability.

9. The fast-response flexible actuator based on the instability expansion of a natural rubber membrane as described in claim 8, characterized in that, The movable frame assembly is connected to the fixed frame via a guide rail slider. The movable frame assembly (24) includes: A first clamping finger (241) is provided with a first rectangular expansion cavity assembly (2411). The second clamping finger (242) is provided with a second rectangular expansion cavity assembly (2412); wherein, The first rectangular expansion cavity assembly (2411) is disposed opposite to the second rectangular expansion cavity assembly (2412).

Images