Adaptive flexible gripper and method of driving

Abstract

The application discloses an adaptive flexible gripper and a driving method. The gripper is composed of a liquid crystal elastomer driving layer, a stiffness-adjustable polymer variable stiffness layer and a gripper support. The driving layer is deformed under thermal stimulation to provide a gripping power. The variable stiffness layer can be hardened and shaped by ultraviolet irradiation to realize configuration programming, and the stiffness can be reversibly adjusted through heating-cooling cycles. The driving method comprises the following steps: firstly, the pre-deformed gripper is configured by ultraviolet light; when the gripper is used to grip an object, the gripper is heated and softened to be rigidly locked after being quickly cooled, so that the load is enhanced and the power consumption is reduced; and the object is released by heating again. The application realizes the integration of configuration customization, load enhancement and passive maintenance of the flexible gripper, breaks through the technical bottleneck of low load and continuous power supply of the traditional flexible gripper, and is suitable for high-end scenes such as precise workpiece operation and heterogeneous part gripping.

Description

Technical Field

[0001] This invention relates to a gripper and its driving method in the field of soft robots, specifically to an adaptive flexible gripper and driving method. Background Technology

[0002] Flexible grippers, due to their inherent flexibility and adaptability, exhibit significant advantages in grasping fragile and irregularly shaped objects. However, existing flexible grippers typically face two core challenges: first, their load-bearing capacity is limited, making it difficult to grasp heavier objects; second, they often require a continuous energy supply to maintain the gripping force or shape during the gripping state, which limits their application in passive or energy-constrained scenarios.

[0003] To address load issues, existing technologies have proposed variable stiffness techniques, such as those based on particle blockage, low-melting-point alloys, or phase change materials. However, these solutions may suffer from slow response times, complex structures, or the need for continuous energy supply to maintain rigidity. To address the lack of energy retention, some technologies employ shape memory polymers, but their actuation and locking mechanisms are typically tightly coupled, making it difficult to achieve rapid and independent locking and releasing control.

[0004] Therefore, there is an urgent need in this field for an innovative flexible gripper solution that can integrate high adaptability, high load capacity, programmability, and energy-free maintenance. Summary of the Invention

[0005] The technical problem solved by this invention is to provide an adaptive flexible gripper and driving method to overcome the shortcomings of existing flexible grippers, such as insufficient adaptability, limited load capacity, and the need for continuous power supply during gripping. This invention aims to achieve one-time optical programming customization of the gripper configuration through a composite structure that integrates driving and controllable stiffness. This allows for rapid load enhancement during gripping and energy-free retention through rigid locking after the power supply is removed, ultimately achieving intelligent, energy-saving, and controllable complex gripping operations.

[0006] The technical solution for achieving the objective of this invention is as follows: I. An Adaptive Flexible Gripper It includes a driving layer, which is made of liquid crystal elastomer material and deforms under thermal stimulation to provide driving force; The variable stiffness layer and the driving layer are stacked and fixedly connected, and are made of a polymer material with adjustable stiffness. The gripper bracket is fixedly connected to the variable stiffness layer and is used to fix and support the drive layer and the variable stiffness layer.

[0007] The variable stiffness layer is divided into two states: a state without UV irradiation and a state with UV irradiation. Uncured state without ultraviolet light irradiation: The variable stiffness layer has not been cured by ultraviolet light, the glass transition temperature of the variable stiffness layer is lower than room temperature, the temperature of the variable stiffness layer at room temperature is higher than the glass transition temperature of the variable stiffness layer, and the stiffness of the variable stiffness layer is low, which is a soft state. Ultraviolet light irradiation hardening state: When the stiffness-adjustable polymer is irradiated with ultraviolet light, its glass transition temperature rises to above room temperature, while the room temperature is below the glass transition temperature of a predetermined region. The stiffness of the stiffness-adjustable polymer material in the predetermined region increases, thereby achieving a hardening state. The stiffness of the stiffness-adjustable polymer is reduced by heating it above its glass transition temperature, thereby unlocking the hardening state. Its stiffness is restored by cooling it below room temperature.

[0008] The driving layer uses a main-chain liquid crystal elastomer material pre-oriented through a stretching-UV crosslinking process. The raw materials for its preparation, by weight, include: 100 parts of mesocrystalline unit (RM257), 5.5-6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20-23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5-0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2-0.4 parts of catalyst (DPA). The initial state of the driving layer is achieved by heating above its phase transition temperature to form a contractile deformation state, which is then cooled below its phase transition temperature to restore the initial state. The stiffness-adjustable polymer material is a UV-curable shape memory polymer system. Its raw materials, by weight, include: 12-18 parts aliphatic polyurethane acrylic resin (AUD), 30-38 parts tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts epoxy resin (E-51), 10-15 parts polyetheramine (D230), and 0.3-0.8 parts photoinitiator benzoin dimethyl ether (DMPA).

[0009] The driving layer and the variable stiffness layer are fixedly connected by an adhesive, which is a silicone adhesive. The variable stiffness layer is in a hardened state after UV curing and is configured to have the following thermal response characteristics: when heated to a temperature exceeding its glass transition temperature and the phase transition temperature of the driving layer, the variable stiffness layer softens and undergoes coordinated deformation with the contraction deformation of the driving layer. During the cold quenching process, the variable stiffness layer rapidly hardens and locks in, restricting the recovery of the drive layer, which is still in a state of contraction deformation, thereby locking the deformation shape of the gripper. During natural cooling, the driving layer gradually recovers and drives the variable stiffness layer to return to its initial state. The cooling rate of the quenching process is greater than 40℃ / s.

[0010] There are two types of gripper: curved structure and wrapped structure. The curved gripper has the following shape: One side of the variable stiffness layer is fixedly connected to the drive layer, and the middle of the other side is fixedly connected to the gripper bracket. Both ends of the variable stiffness layer are bent in the direction of the variable stiffness layer to form an arc-shaped U-shaped bend for gripping objects. The gripper shape of the winding structure is as follows: The variable stiffness layer and the drive layer together form a continuous spiral shape for gripping objects.

[0011] III. A crawling system It includes at least one adaptive flexible gripper as its core actuation and structural unit.

[0012] IV. A Driving Method for an Adaptive Flexible Gripper V. The driving method includes a first working mode and a second working mode: The first working mode is to apply heat energy to the adaptive flexible gripper in its initial state to deform it for gripping a lightly loaded object, thereby moving the lightly loaded object. Under natural cooling in the environment, the adaptive flexible gripper returns to its initial state and releases the lightly loaded object. The second working mode involves applying heat energy to the adaptive flexible gripper in its initial state to deform it for gripping heavy-load objects. Then, the deformation of the adaptive flexible gripper is locked by cold quenching, thereby moving the heavy-load objects. Next, heat energy is applied again to unlock the deformation lock of the adaptive flexible gripper. Finally, under natural cooling in the environment, the adaptive flexible gripper returns to its initial state, thereby releasing the heavy-load objects.

[0013] The first working mode is as follows: Driving steps: Apply heat energy to the adaptive flexible gripper in its initial state, causing the temperature to rise above the phase transition temperature of its driving layer and the glass transition temperature of its variable stiffness layer, respectively. The variable stiffness layer softens and the driving layer contracts and deforms, causing the variable stiffness layer to deform, in order to grip the object. Release steps: The adaptive flexible gripper is cooled in the environment, and under the action of the driving layer, the adaptive flexible gripper returns to its initial state, thereby releasing the object.

[0014] The second working mode is as follows: Activation step: Apply heat to the adaptive flexible gripper in its initial state, raising the temperature to exceed the phase transition temperature of its driving layer and the glass transition temperature of its variable stiffness layer, respectively. The variable stiffness layer softens and the driving layer contracts and deforms, causing the variable stiffness layer to deform to conform to the object. Locking step: Then, the adaptive flexible gripper is subjected to cold quenching treatment to achieve hardening and locking of the adaptive flexible gripper, thereby driving the clamped object to move; Release steps: Apply heat energy again to the adaptive flexible gripper which is in a hardened locked state to release the hardened locked state. Finally, allow the adaptive flexible gripper to cool to the ambient temperature, and the gripper will return to its initial state, thereby releasing the object.

[0015] Divided into two types: gripper shape drive with curved structure and gripper shape drive with wound structure. When the adaptive flexible gripper is in the form of a curved gripper, the original U-shaped adaptive flexible gripper will continue to bend towards the drive layer at both ends of the variable stiffness layer in both the first and second working modes to clamp the object. When the adaptive flexible gripper is in the form of a wound structure gripper, the original continuously spirally coiled adaptive flexible gripper generates a variable stiffness layer that continues to contract in the direction of the driving layer in both the first and second working modes to deform for gripping the object.

[0016] The beneficial effects of this invention are: This invention integrates flexible gripper configuration customization, load enhancement, and passive holding, overcoming the technical bottlenecks of traditional flexible grippers that have low load capacity and require continuous power supply. It is suitable for high-end scenarios such as precision workpiece operation and heterogeneous part gripping.

[0017] 1. High adaptability Based on the properties of the stiffness-adjustable polymer, an external force is applied to the composite sheet to induce a pre-deformation that conforms to the contour of the target object; while maintaining the pre-deformation, ultraviolet light is applied to the stiffness-adjustable polymer to obtain a gripper that is highly adaptable to the shape and size of the object being grasped, including bending grippers, wrapping grippers, etc., to achieve customized grasping.

[0018] 2. Increase crawling load Based on the significant differences in the thermodynamic behavior of the variable stiffness layer and the driving layer, this invention achieves instantaneous locking of the gripping form and a leap in load capacity through a "heating-rapid quenching" process. Specifically, during rapid quenching, the variable stiffness layer can quickly cross the glass transition region and become rigid, thereby locking the structure; simultaneously, the phase transformation of the driving layer is maintained by kinetic lag, allowing it to retain its driving deformation. The synergistic effect of these two processes ultimately results in a substantial increase in gripping load.

[0019] 3. No energy input required for maintenance This invention achieves instantaneous locking of the grasping form through "heating-rapid cooling". After that, no additional energy input is required to maintain the grasping state. Once the designated position is reached or a preset time has elapsed, the locking state is released by reheating, and the release is achieved during the cooling process with the environment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the adaptive flexible gripper described in this invention; Figure 2 This is a schematic diagram of the manufacturing process of the adaptive bending flexible gripper described in this invention; Figure 3 This is a schematic diagram of the manufacturing process of the adaptive winding flexible gripper described in this invention; Figure 4 This is a schematic diagram of the working mode of the adaptive bending flexible gripper described in this invention; Figure 5 This is a schematic diagram of the working mode of the adaptive winding flexible gripper described in this invention; Figure 6 Experimental photographs of gripping tape using the adaptive bending flexible gripper described in this invention, in the first working mode; Figure 7 Experimental photographs of gripping weights using the adaptive bending flexible gripper described in this invention in the second working mode; Figure 8 Experimental photographs of gripping a cylindrical object using the adaptive winding flexible gripper described in this invention, in the first working mode.

[0021] In the diagram: Drive layer 1, variable stiffness layer 2, gripper bracket 3. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, an adaptive flexible gripper includes: The driving layer 1 is made of liquid crystal elastomer material and can undergo reversible macroscopic deformation under thermal stimulation to provide driving force; The variable stiffness layer 2 and the driving layer 1 are stacked and fixedly connected, and are made of a stiffness-adjustable polymer 2 material. The gripper bracket 3 is fixedly connected to the variable stiffness layer 2 and is used to fix and support the composite structure of the drive layer 1 and the variable stiffness layer 2.

[0024] The driving layer 1, the power source for the movement of the flexible gripper, is composed of a liquid crystal elastomer material, specifically a liquid crystal elastomer film with a uniaxial orientation structure. The liquid crystal molecules within this film achieve a macroscopically ordered arrangement during the fabrication process through a stretching-crosslinking technique. Its working mechanism is as follows: when subjected to external stimuli such as heating, or when heat is generated by doping with photothermal agents / absorbing specific wavelengths of light, the degree of order of the liquid crystal molecules changes, causing the film to undergo significant and reversible contraction along its orientation direction. After the stimulus is removed and the film cools, it returns to its initial length. This reversible contraction-recovery behavior provides the core, large-amplitude driving force for the flexible gripper.

[0025] The variable stiffness layer 2 is crucial for the flexible gripper to achieve adaptive configurations, increase gripping loads, and achieve energy-free holding. It is composed of a light / thermal responsive, stiffness-tunable polymer. The variable stiffness layer has two states: In the sheet-like structure, the material is in a state of hardening without UV irradiation. In this state, the variable stiffness layer has not been cured by UV light, its crosslinking density is at an initial low level, its glass transition temperature is lower than room temperature, and the material exhibits soft and highly elastic properties. In the gripper designed to adapt to the shape of the object being grasped, the stiffness-adjustable polymer is in a UV-cured state. In this state, the variable stiffness layer, after UV curing, exhibits a significantly increased cross-linking density and a glass transition temperature far exceeding room temperature. The material becomes rigid and possesses shape memory and fixation capabilities. This polymer possesses unique dynamic mechanical properties, with its elastic modulus being extremely sensitive to temperature changes: when heated above its glass transition temperature or phase transition temperature, the polymer chain segments become active, and the material transitions from a rigid to a soft state with a significantly reduced modulus. At this point, even a small stress generated by the driving layer 2 can cause it to deform accordingly. When the temperature is rapidly cooled below the transition temperature, the polymer chain segment movement is frozen, and the material returns to a high-modulus rigid state, effectively resisting the elastic restoring force of the driving layer and other parts, thus "locking" the overall shape of the flexible gripper in its current deformed state. The unlocking process can be achieved simply by reheating, forming a controllable cycle of "heating-deformation and softening-rapid cold quenching and locking-reheating and unlocking".

[0026] Among them, the variable stiffness layer 2 is divided into a state without ultraviolet light irradiation and a state with ultraviolet light irradiation: Uncured state without UV irradiation: In this state, the variable stiffness layer 2 has not been cured by UV light, its crosslinking density is at an initial low level, the glass transition temperature of the variable stiffness layer 2 is lower than room temperature, the temperature of the variable stiffness layer 2 at room temperature is higher than the glass transition temperature of the variable stiffness layer 2, the stiffness of the variable stiffness layer 2 is low and it is in a soft state, specifically exhibiting soft and highly elastic characteristics. UV-cured state: In the gripper designed to adapt to the shape of the object being gripped, the variable stiffness layer 2 is in a UV-cured state. After UV-curing, the crosslinking density of the stiffness-adjustable polymer 2 increases significantly, and its glass transition temperature rises to a level far above room temperature, while room temperature is far below the glass transition temperature of the predetermined region. The stiffness of the stiffness-adjustable polymer material in the predetermined region is increased, exhibiting rigidity, and possessing shape memory and fixation capabilities, thus achieving the cured state. The stiffness of the stiffness-adjustable polymer 2 can be reversibly reduced by heating it above its glass transition temperature, thus unlocking the cured state, and its stiffness can be restored by cooling it below room temperature, thus achieving configuration locking.

[0027] After the variable stiffness layer 2 switches from a state without UV irradiation to a state with UV irradiation, its room temperature elastic modulus is significantly improved, achieving a change across orders of magnitude.

[0028] The liquid crystal elastomer material used in the driving layer 1 is a main-chain liquid crystal elastomer pre-oriented by a stretching-ultraviolet crosslinking process. The raw materials for its preparation include, by weight, 100 parts of mesocrystalline unit (RM257), 5.5~6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20~23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5~0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2~0.4 parts of catalyst (DPA). The initial state of the driving layer 1 is formed by heating above its phase transition temperature to a shrinkage deformation state along its molecular orientation direction. The shrinkage deformation state is restored to its initial state by natural cooling in the environment to below its phase transition temperature. The reversible shrinkage strain range is between 40% and 50%. The stiffness-adjustable polymer material is a UV-curable shape memory polymer system. The raw materials for its preparation include, by weight, 12-18 parts of aliphatic polyurethane acrylic resin (AUD), 30-38 parts of tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts of epoxy resin (E-51), 10-15 parts of polyetheramine (D230), and 0.3-0.8 parts of photoinitiator benzoin dimethyl ether (DMPA).

[0029] The driving layer 1 and the variable stiffness layer 2 are fixedly connected by an adhesive to form an initial planar sheet structure. The adhesive is Sil-Poxy silicone adhesive. The adaptive flexible gripper is fixed in shape by a clamp and hardened by ultraviolet light irradiation according to the shape and size of the object being gripped, resulting in adaptive bending structure gripper shapes and winding structure gripper shapes. The variable stiffness layer 2 in the hardened state under ultraviolet light irradiation softens after being heated to a temperature exceeding its glass transition temperature in the initial state of the adaptive flexible gripper. Meanwhile, the driving layer 1 shrinks and deforms after being heated to a temperature exceeding its phase transition temperature, causing the softened variable stiffness layer 2 to deform as well. The variable stiffness layer 2 is then rapidly quenched to below room temperature to form a hardened and locked state. The hardened and locked state is released by reheating to a temperature exceeding its glass transition temperature. The nematic phase transition characteristics allow the driving layer 1 to return to its original state before heating during the natural and slow cooling process after heating. In rapid quenching with a cooling rate greater than 40℃ / s, the glass transition dynamics of the variable stiffness layer 2 takes precedence over the nematic phase transition of the driving layer 1. This makes the driving layer 1 unable to recover in time compared to the variable stiffness layer 2, resulting in the variable stiffness layer 2 hardening and locking, while the driving layer 1 remains in a state of shrinkage deformation. As the material cools slowly in the natural environment, the driving layer 1 has enough time to recover, thereby causing the variable stiffness layer 2 to recover to its initial state as well.

[0030] Adaptive flexible grippers are divided into two types: curved gripper form and wound gripper form. The curved structure gripper has the following shape: One side of the variable stiffness layer 2 is fixedly connected to the drive layer 1, and the middle of the other side is fixedly connected to the gripper bracket 3. Both ends of the variable stiffness layer 2 are bent towards the variable stiffness layer 2 to form an arc-shaped U-shaped bend with the opening facing downward, which is used to grip objects. The winding structure gripper shape is as follows: The variable stiffness layer 2 and the driving layer 1 together form a continuous spiral curl shape with a spiral surface extending along the axial direction for gripping objects.

[0031] The adaptive flexible gripper is prepared by providing a driving functional layer precursor solution, which is then cured in a first curing process to form a liquid crystal elastomer film; providing a variable stiffness functional layer precursor solution, which is then cured in a second curing process to form a stiffness-adjustable polymer layer that has not been cured by ultraviolet light; and then combining the liquid crystal elastomer film with the uncured stiffness-adjustable polymer layer to form a composite sheet.

[0032] An external force is applied to the composite sheet to induce a pre-deformation that conforms to the contour of the target object; while maintaining the pre-deformation, ultraviolet light is applied to the variable stiffness functional layer to change it from a state of no ultraviolet light hardening to a state of ultraviolet light hardening, thereby permanently fixing the pre-deformed shape.

[0033] Furthermore, such as Figure 2 and Figure 3 The specific manufacturing processes for the curved and wound grippers are shown separately: First, a liquid crystal elastomer and a stiffness-tunable polymer that has not been cured by ultraviolet light are provided.

[0034] The method for preparing the liquid crystal elastomer is characterized by the following steps: 5.75g of RM257 and 1.28g of toluene are mixed in a beaker and heated in an oven at 85°C for about 20 minutes. Then, 0.037g of HHMP is added to the beaker. After the mixture clarifies, 0.342g of PETMP and 1.238g of EDDET are mixed together and then added to the above mixture. Subsequently, 0.018g of DPA is poured into the beaker. The solution is stirred for about 1 minute, degassed in a vacuum chamber for about 5 minutes, and poured into a mold. Next, the mold is placed in a dark environment for 24 hours. In a subsequent step, the cured film-like LCE is placed in an oven at 85°C for 12 hours to evaporate the solvent. Finally, the LCE film is stretched to three times its original length and irradiated with ultraviolet light at 365nm and 10mW / cm² for 10 minutes.

[0035] The method for preparing a stiffness-tunable polymer is characterized by the following steps: 1.5g AUD, 3.45g TCDDA, 3.75g E-51, and 0.05g DMPA are mixed in a beaker and heated at 80°C for 5 minutes. Then, 1.25g D230 is added to the beaker. After stirring the mixture for 1 minute, it is degassed in a vacuum chamber for approximately 5 minutes to obtain a prepolymer of the stiffness-tunable polymer. Next, the obtained prepolymer is poured into a mold. It is then thermocured at 80°C for 4 hours, followed by post-curing at 120°C for 4 hours. Finally, it is subjected to a wavelength of 365nm and an intensity of 50mW / cm². 2 A polymer with adjustable stiffness was obtained by irradiating it with ultraviolet light for 300 seconds.

[0036] Subsequently, the two are firmly bonded together with an adhesive to form an initial sheet-like structure. External force is applied to this initial sheet-like structure using external tooling, causing it to undergo pre-deformation conforming to the contours of the target object. While maintaining this pre-deformation state, ultraviolet light is applied to the variable stiffness functional layer, transforming it from an uncured state to a UV-cured state. This photoprogramming curing process permanently fixes the gripper's configuration. Finally, this programmed structure is assembled onto the gripper bracket 3, resulting in the target gripper.

[0037] A gripping system includes at least one adaptive flexible gripper as its core actuation and structural unit.

[0038] like Figure 4 and Figure 5 As shown, a driving method employing an adaptive flexible gripper includes a first operating mode and a second operating mode: The first working mode is to apply heat energy to the adaptive flexible gripper in its initial state to deform it so as to grip a light load object less than 20 times the combined mass of the drive layer (1) and the variable stiffness layer (2), thereby moving the light load object by moving the gripper support 3. Under natural cooling in the environment, the adaptive flexible gripper returns to its initial state and releases the light load object. The second working mode involves applying heat energy to the adaptive flexible gripper in its initial state to deform it for gripping a heavy-load object that is more than 20 times the combined mass of the drive layer (1) and the variable stiffness layer (2). Then, the deformation of the adaptive flexible gripper is locked by cold quenching, thereby moving the heavy-load object by moving the gripper support 3. Then, the deformation lock of the adaptive flexible gripper is unlocked by applying heat energy again. Finally, under natural cooling in the environment, the adaptive flexible gripper returns to its initial state, thereby releasing the heavy-load object.

[0039] The flexible gripper of this invention has a high degree of flexibility and adaptability in its working mode, specifically manifested in: Based on the UV curing properties of stiffness-adjustable polymers, grippers with high shape adaptability, such as bending and wrapping types, can be manufactured to grasp objects of different shapes, achieving efficient grasping.

[0040] For lightly loaded objects to be grasped, the first grasping mode is adopted, namely: applying heat energy to the gripper softens the variable stiffness functional layer, and the driving functional layer drives the gripper to deform in order to grasp the object; after reaching the designated position, the gripper is cooled by the environment, the driving layer relaxes, and the gripper is driven to restore its shape, thereby releasing the object.

[0041] For heavy-load objects to be grasped, a second grasping mode is adopted, namely: applying heat energy to the gripper softens the variable stiffness functional layer, and after the driving functional layer drives the gripper to deform, the gripper is rapidly quenched to lock the gripper shape, thereby achieving grasping and energy-free holding; after reaching the designated position, applying heat energy to the gripper releases the locked state, and under environmental cooling, the driving layer expands, driving the gripper to restore its shape, thereby releasing the object.

[0042] Heating methods include hot air convection heating and infrared radiation heating; quenching methods include ice water bath immersion cooling, vortex tube cryogenic airflow cooling, and cryogenic spray cooling.

[0043] The first working mode is as follows: S11: Apply heat energy to the adaptive flexible gripper in its initial state, causing the temperature to rise above the phase transition temperature of its driving layer 1 and the glass transition temperature of its variable stiffness layer 2, respectively. The variable stiffness layer 2 softens and the driving layer 1 contracts and deforms, causing the variable stiffness layer 2 to deform, for clamping lightly loaded objects. S12: When the lightly loaded object is moved to the target position, the adaptive flexible gripper is allowed to cool naturally in the environment. Under the action of the drive layer 1, the adaptive flexible gripper returns to its initial state, thereby releasing the lightly loaded object.

[0044] The second working mode is as follows: S21: Apply heat energy to the adaptive flexible gripper in its initial state, causing the temperature to rise above the phase transition temperature of its driving layer 1 and the glass transition temperature of its variable stiffness layer 2, respectively. The variable stiffness layer 2 softens and the driving layer 1 contracts and deforms, causing the variable stiffness layer 2 to deform, for clamping high-load objects. S22: Then, the adaptive flexible gripper is subjected to rapid cold quenching treatment. By utilizing the dynamic lag of the phase change of the driving layer 1 and the rapid glass transition of the variable stiffness layer 2, the hardening and locking of the adaptive flexible gripper is achieved, and the overall configuration of the adaptive flexible gripper is locked in the driving deformation state. This can improve the gripping load and achieve energy-free holding, thereby driving the movement of the gripper support 3 to clamp the high-load object. S23: When the high-load object is moved to the target position, heat energy is applied again to the adaptive flexible gripper which is in a hardened locked state to release the rigid lock of the variable stiffness layer 2, thereby releasing the hardened locked state. Finally, under the natural cooling of the environment, the adaptive flexible gripper is restored to its initial state under the action of the drive layer 1, thereby releasing the high-load object.

[0045] More specifically, heat is applied to the gripper, raising its temperature above the phase transition temperature of the driving functional layer and above the glass transition temperature of the variable stiffness functional layer, thereby softening the variable stiffness functional layer and triggering the driving deformation of the driving functional layer. The gripper is then subjected to rapid cold quenching, utilizing the kinetic hysteresis of the phase transition of the driving functional layer and the rapid glass transition of the variable stiffness functional layer to lock the overall configuration of the gripper in the driving deformation state, which can increase the gripping load and achieve energy-free holding. Heat is then applied again to the gripper in the locked state to release the rigid lock of the variable stiffness functional layer. Subsequently, under ambient cooling, the gripper returns to its initial programmed shape, thereby releasing the object. The mechanism for locking the gripper deformation through rapid cold quenching is as follows: the phase transition dynamics of liquid crystal elastomers and stiffness-tunable polymers exhibit significant differences. The first-order phase transition of liquid crystal elastomers is significantly time-dependent; rapid cold quenching delays its phase transition process, keeping it in a contracted state. In contrast, the glass transition of stiffness-tunable polymers is a kinetically controlled second-order transition, relatively insensitive to the cooling rate, and can rapidly recover its high-modulus state during rapid cooling. Based on this mechanism, after the gripper deforms due to heat: if slow cooling is used, the order of the liquid crystal elastomer gradually recovers, driving the gripper back to its initial shape; if rapid cold quenching is implemented, the variable stiffness layer solidifies first and locks the system's mechanical state. At this time, the driving layer is still in a contracted state, thus effectively fixing the gripper deformation. The locked state can be released by reheating, and the shape can be fully restored through a subsequent slow cooling process, thereby releasing the object.

[0046] Divided into two types: gripper shape drive with curved structure and gripper shape drive with wound structure. When the adaptive flexible gripper is in the form of a curved gripper, the two ends of the original variable stiffness layer 2 bend towards the driving layer 1 in a U-shaped curved shape. In both the first and second working modes, the two ends of the variable stiffness layer 2 continue to bend towards the driving layer 1 to deform for clamping objects. When the adaptive flexible gripper is in the form of a wound structure gripper, the original continuously spirally coiled adaptive flexible gripper generates a variable stiffness layer 2 that continues to contract in the direction of the drive layer 1 in both the first and second working modes to deform for gripping the object. This results in the formation of a spiral contraction.

[0047] like Figure 6 As shown, the bending adaptive flexible gripper of the present invention, in a first working mode, grips a lightly loaded object, such as tape. After being heated, the gripper further bends and deforms, successfully gripping the tape. After moving it to a designated position, the gripper returns to its shape during the slow cooling process with the environment, thereby releasing the object.

[0048] like Figure 7As shown, the bending adaptive flexible gripper of the present invention employs a second working mode to grip heavy-load objects such as weights. Specifically, after being heated, the gripper further bends and deforms. If it directly grips the tape, the force provided by the liquid crystal elastomer is limited due to the flexible state of the stiffness-adjustable polymer, making it impossible to successfully grip the weight. If the gripper is rapidly cooled by cold air after being heated, the stiffness-adjustable polymer quickly hardens and locks the mechanical state of the system. At this time, the liquid crystal elastomer is still in a contracted state, thereby effectively fixing the deformation of the gripper. At this point, the weight can be successfully gripped and held without energy input. After reaching the designated position, the locked state is released by heating, and the weight is released.

[0049] like Figure 8 As shown, the winding-type adaptive flexible gripper of the present invention employs a first working mode to grip a cylindrical object. Specifically, after being heated, the gripper further winds and deforms, successfully gripping the object. After moving it to a designated position, the gripper returns to its shape during the slow cooling process with the environment, thereby releasing the object.

[0050] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of this invention should be included within the scope of protection of the claims of this invention. The scope of protection of this invention should be determined by the claims.

Claims

1. An adaptive flexible gripper, characterized in that, include: The driving layer (1) is made of liquid crystal elastomer material and deforms under thermal stimulation to provide driving force; The variable stiffness layer (2) and the driving layer (1) are stacked and fixedly connected, and are made of a stiffness-adjustable polymer (2) material; The gripper bracket (3) is fixedly connected to the variable stiffness layer (2) for fixed support of the drive layer (1) and the variable stiffness layer (2). The variable stiffness layer (2) is divided into a state of hardening without ultraviolet light irradiation and a state of hardening with ultraviolet light irradiation: Uncured state without ultraviolet light irradiation: The variable stiffness layer (2) has not been cured by ultraviolet light. The glass transition temperature of the variable stiffness layer (2) is lower than the room temperature. At room temperature, the temperature of the variable stiffness layer (2) is higher than the glass transition temperature of the variable stiffness layer (2). The variable stiffness layer (2) has low stiffness and is in a soft state. Ultraviolet light irradiation hardening state: After the stiffness adjustable polymer (2) is irradiated with ultraviolet light, its glass transition temperature rises to above room temperature, and the room temperature is below the glass transition temperature of a predetermined region. The stiffness of the stiffness adjustable polymer material in the predetermined region is increased, thereby achieving the hardening state; the stiffness of the stiffness adjustable polymer (2) is reduced by heating it to above its glass transition temperature, thereby unlocking the hardening state, and its stiffness is restored by cooling it to below room temperature; The driving layer (1) uses a liquid crystal elastomer material that is a main-chain liquid crystal elastomer pre-oriented by a stretching-ultraviolet crosslinking process. The raw materials for its preparation include, by weight, 100 parts of mesocrystalline unit RM257, 5.5~6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20~23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5~0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2~0.4 parts of catalyst DPA. The initial state of the driving layer (1) is formed by heating above its phase transition temperature to form a shrinkage deformation state. The shrinkage deformation state is cooled to below its phase transition temperature to restore the initial state. The stiffness-adjustable polymer material is a UV-curable shape memory polymer system, and its raw materials, by weight, include: 12-18 parts of aliphatic polyurethane acrylic resin (AUD), 30-38 parts of tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts of epoxy resin E-51, 10-15 parts of polyetheramine D230, and 0.3-0.8 parts of photoinitiator benzoin dimethyl ether (DMPA).

2. The adaptive flexible gripper according to claim 1, characterized in that: The driving layer (1) and the variable stiffness layer (2) are fixedly connected by an adhesive, which is a silicone adhesive. The variable stiffness layer (2) is in a hardened state after UV curing and is configured to have the following thermal response characteristics: when heated to a temperature exceeding its glass transition temperature and the phase transition temperature of the driving layer (1), the variable stiffness layer (2) softens and undergoes synergistic deformation with the contraction deformation of the driving layer (1). During the cold quenching process, the variable stiffness layer (2) is rapidly hardened and locked, restricting the recovery of the drive layer (1) which is still in a state of shrinkage deformation, thereby locking the deformation shape of the gripper. During natural cooling, the driving layer (1) gradually recovers and drives the variable stiffness layer (2) to recover to the initial state together; The cooling rate of the quenching process is greater than 40℃ / s.

3. The adaptive flexible gripper according to claim 1, characterized in that, There are two types of gripper: curved structure and wrapped structure. The curved gripper has the following shape: One side of the variable stiffness layer (2) is fixedly connected to the drive layer (1), and the middle of the other side is fixedly connected to the gripper bracket (3). The two ends of the variable stiffness layer (2) are bent in the direction of the variable stiffness layer (2) to form an arc-shaped U-shaped bend, which is used to grip objects. The gripper shape of the winding structure is as follows: The variable stiffness layer (2) and the drive layer (1) together form a continuous spiral curl shape for gripping objects.

4. A grasping system, characterized in that, It includes at least one adaptive flexible gripper as described in any one of claims 1-3 as its core actuation and structural unit.

5. A driving method for using an adaptive flexible gripper as described in any one of claims 1-3, characterized in that, The driving method includes a first working mode and a second working mode: The first working mode is to apply heat energy to the adaptive flexible gripper in its initial state to deform it for gripping a lightly loaded object, thereby moving the lightly loaded object. Under natural cooling in the environment, the adaptive flexible gripper returns to its initial state and releases the lightly loaded object. The second working mode involves applying heat energy to the adaptive flexible gripper in its initial state to deform it for gripping heavy-load objects. Then, the deformation of the adaptive flexible gripper is locked by cold quenching, thereby moving the heavy-load objects. Next, heat energy is applied again to unlock the deformation lock of the adaptive flexible gripper. Finally, under natural cooling of the environment, the adaptive flexible gripper returns to its initial state, thereby releasing the heavy-load objects.

6. The driving method for an adaptive flexible gripper according to claim 5, characterized in that, The first working mode is as follows: Driving steps: Apply heat energy to the adaptive flexible gripper in its initial state, so that the temperature rises to exceed the phase transition temperature of its driving layer (1) and the glass transition temperature of its variable stiffness layer (2), respectively. The variable stiffness layer (2) softens and the driving layer (1) contracts and deforms, causing the variable stiffness layer (2) to deform, for gripping objects. Release steps: Cool the adaptive flexible gripper in the environment, and under the action of the drive layer (1), the adaptive flexible gripper is restored to its initial state, thereby releasing the object.

7. The driving method for an adaptive flexible gripper according to claim 5, characterized in that, The second working mode is as follows: Activation step: Apply heat to the adaptive flexible gripper in its initial state, so that the temperature rises to exceed the phase transition temperature of its driving layer (1) and the glass transition temperature of its variable stiffness layer (2), respectively. The variable stiffness layer (2) softens and the driving layer (1) contracts and deforms, causing the variable stiffness layer (2) to deform, so as to conform to the object. Locking step: Then, the adaptive flexible gripper is subjected to cold quenching treatment to achieve hardening and locking of the adaptive flexible gripper, thereby driving the clamped object to move; Release steps: Apply heat energy again to the adaptive flexible gripper, which is in a hardened and locked state, thereby releasing the hardened and locked state. Finally, allow the adaptive flexible gripper to cool in the environment, and the gripper will return to its initial state, thereby releasing the object.

8. The driving method for an adaptive flexible gripper according to claim 5, characterized in that, Divided into two types: gripper shape drive with curved structure and gripper shape drive with wound structure. When the adaptive flexible gripper is in the form of a curved gripper, the original U-shaped flexible gripper in both the first and second working modes produces deformation in which the two ends of the variable stiffness layer (2) continue to bend towards the driving layer (1) to clamp the object. When the adaptive flexible gripper is in the form of a wound structure gripper, the original continuously spirally coiled adaptive flexible gripper generates a variable stiffness layer (2) in both the first and second working modes, which continues to contract in the direction of the driving layer (1) to deform for clamping the object.

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