A stiffness-adjustable soft actuator based on directional biomimetic adhesive material

Abstract

The application provides a stiffness-adjustable soft driver based on a directional bionic adhesive material, which comprises a front end cover, a sealing film, a directional bionic adhesive material, a soft continuum and a rear end cover; a plurality of air cavities are arranged in the soft continuum; the front end cover is provided with a plurality of positive pressure air holes and a vacuum air hole; each positive pressure air hole is connected with one air cavity; and the vacuum air hole is connected with a vacuum sealed cavity; by inputting different air pressures into the air cavities on the soft continuum, the whole driver can realize bending at different angles and directions; by inputting the same air pressure into the air cavities on the soft continuum, the whole driver can realize overall stretching and contraction; by inputting different negative pressures into the vacuum sealed cavity, the size of the adhesive force is controlled, so that the stiffness of the soft driver is adjustable. The application proposes a stiffness-adjustable method based on a directional bionic adhesive material, which is completely different from the traditional soft robot stiffness-adjustable method, has a brand-new stiffness-adjustable theory, and can greatly improve the stiffness change range of the soft driver.

Description

Technical Field

[0001] This invention relates to the field of drive technology, and in particular to a stiffness-adjustable soft actuator based on directional biomimetic adhesive materials. Background Technology

[0002] Traditional actuators are mostly made of rigid materials with limited elastic deformation capabilities. Their shape adapts to specific external constraints and obstacles, exhibiting high precision. However, the limitations of rigid actuator structure and materials present two major, insurmountable problems: Firstly, rigid actuators are often composed of chain and linkage structures. Each additional degree of freedom requires the addition of corresponding kinematic pairs, resulting in an extremely complex actuator structure with limited flexibility. Secondly, the use of rigid materials makes it difficult for rigid actuators to exhibit high deformability and adaptability to different situations. Although they can interact with humans or the environment through sensor feedback control, significant safety hazards remain. These drawbacks pose significant challenges to rigid actuators in certain specialized applications (such as human-machine interaction for grasping complex and fragile objects and operations in confined spaces).

[0003] Methods for varying stiffness in soft robots or actuators can be broadly categorized into two types: structural stiffness variation methods and material stiffness variation methods. Structural stiffness variation methods typically achieve stiffness variation through ingenious structural design, based on interactions between structures, including antagonistic and blocking effects. Material stiffness variation methods generally utilize external stimuli, such as temperature, magnetic fields, or electric fields, to induce changes in the physical or chemical properties of the material, thereby achieving stiffness variation. These methods primarily utilize materials such as low-melting-point alloys, electrorheological fluids, magnetorheological fluids, and shape memory polymers.

[0004] Soft actuators possess inherent compliance and safety, coupled with their deformability and virtually unlimited degrees of freedom, compensating for the shortcomings of rigid robots in environmental adaptability and operational safety. By actively deforming the robot's body, they alter its original shape, structure, and dimensions to adapt to changing environments and perform specific operations. While soft actuators offer advantages that rigid robots lack, they still suffer from drawbacks such as limited motion space and a narrow range of stiffness variation. Consequently, they cannot meet the challenges of heavy-load operations in complex environments, significantly limiting the practical application and widespread adoption of soft actuator technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a stiffness-adjustable soft actuator based on directional biomimetic adhesive materials.

[0006] To address the problems of existing technologies, this invention discloses a stiffness-adjustable soft actuator based on a directional biomimetic adhesive material, comprising a front end cap, a sealing membrane, a directional biomimetic adhesive material, a soft continuum, and a rear end cap; the front end cap and the rear end cap are connected by the sealing membrane, forming a sealed cavity inside the sealing membrane; the soft continuum is disposed within the sealed cavity inside the sealing membrane, and a vacuum sealing cavity is provided between the surface of the soft continuum and the inner side of the sealing membrane; the directional biomimetic adhesive material is disposed in the vacuum sealing cavity and adhered to the surface of the soft continuum; multiple air chambers are provided within the soft continuum, and the front end cap has multiple positive pressure air holes and vacuum air holes, each positive pressure air hole connecting to one air chamber, and the vacuum air holes connecting to the vacuum sealing cavity;

[0007] The positive pressure vent is used to connect the external positive pressure to the air cavity. When multiple positive pressure vents are filled with different air pressures, the bending of the soft continuum is controlled; when multiple positive pressure vents are filled with the same air pressure, the expansion and contraction of the soft continuum is controlled.

[0008] The vacuum vent is used to connect the external negative pressure to the vacuum sealing cavity. The directional biomimetic adhesive material is stacked layer by layer in the vacuum sealing cavity. When the soft continuum stretches or bends, the directional biomimetic adhesive material is misaligned, resulting in changes in the contact area between the layers. Different negative pressures introduced into the vacuum sealing cavity cause different contact lengths between the directional biomimetic adhesive material and the surface of the soft continuum, controlling the magnitude of the adhesion force, thereby realizing the stiffness adjustment of the soft actuator.

[0009] Furthermore, the contact surface between the directional biomimetic adhesive material and the soft continuum is provided with a micro-nano array structure.

[0010] Furthermore, the outer side of the soft continuum is provided with several clamps.

[0011] Furthermore, the outer side of the soft continuum is provided with several clamp mounting ports.

[0012] Furthermore, the directional biomimetic adhesive material is provided with several thread holes, and the directional biomimetic adhesive material is wrapped around the surface of the soft continuum by passing a thread through the thread holes.

[0013] Furthermore, there are three positive pressure vents and three air chambers, with the positive pressure vents arranged in a triangular pattern.

[0014] The beneficial effects of this invention are as follows:

[0015] By introducing different levels of air pressure into the air cavity of the soft continuum, the entire actuator can achieve bending at different angles and orientations; by introducing the same level of air pressure into the air cavity of the soft continuum, the entire actuator can achieve overall expansion and contraction; by introducing different levels of negative pressure into the vacuum-sealed cavity, the magnitude of the adhesive force can be controlled, thereby achieving adjustable stiffness of the soft actuator. This invention proposes a variable stiffness method based on directional biomimetic adhesive materials, which is completely different from traditional methods for variable stiffness in soft robots. It has a novel theory of adjustable stiffness and can greatly improve the range of stiffness variation of the soft actuator. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram of the present invention;

[0017] Figure 2 for Figure 1 A schematic diagram of section AA marked on the cross-sectional view;

[0018] Figure 3 for Figure 1 Enlarged view of B marked on the cross-sectional view;

[0019] Figure 4 This is a three-dimensional internal structure diagram of the present invention;

[0020] Figure 5 This is a schematic diagram of the bent state;

[0021] Figure 6 This is a schematic diagram of a soft continuum structure;

[0022] Figure 7 A schematic diagram of the microstructure of a typical directional biomimetic adhesive material;

[0023] Figure 8 This is a macroscopic planar schematic diagram of the adhesive material.

[0024] In the diagram: 1. Front cover, 101. Vacuum vent, 102. Positive pressure vent; 2. Sealing membrane; 3. Directional biomimetic adhesive material, 301. Micro-nano array structure, 302. Threading hole; 4. Clamp; 5. Soft continuum, 501. Air cavity, 502. Clamp mounting port; 6. Rear cover; 7. Vacuum sealing cavity. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0026] like Figure 1-8 As shown, the present invention provides a stiffness-adjustable soft actuator based on a directional biomimetic adhesive material, comprising a front end cover 1, a sealing film 2, a directional biomimetic adhesive material 3, a clamp 4, a soft continuum 5, and a rear end cover 6.

[0027] The front cover 1 is made of rigid material and has three positive pressure air holes 102 and several vacuum air holes 101. The soft continuum 5 has three air chambers 501. The three positive pressure air holes 102 are respectively connected to the three air chambers 501 of the soft continuum 5. The positive pressure air holes 102 are connected to external positive pressure. The sealing membrane 2 is made of flexible material and is sealed to the front cover 1 and the rear cover 6 at both ends. The directional biomimetic adhesive material 3 has a thread hole 302. A non-stretchable thread is passed through the thread hole 302 and wound into a ring and fixed to the surface of the soft continuum 5. The clamp 4 is made of rigid material and is ring-shaped. It is fixedly installed on the clamp mounting port 502 on the surface of the soft continuum 5. The clamp 4 is used to limit the axial deformation of the soft continuum under pressure.

[0028] The front cover 1, sealing membrane 2, soft continuum 5, and rear cover 6 are sealed together to form a vacuum sealing cavity 7. Several vacuum holes 101 on the front cover 1 are connected to the vacuum sealing cavity 7, and the vacuum holes 101 are connected to the external negative pressure.

[0029] Preferably, the directional biomimetic adhesive material 3 has a micro-nano array structure 301 on its surface. Different expansion and contraction directions of the soft continuum 5 will generate adhesive forces of different magnitudes and directions. The directional biomimetic adhesive material 3 is stacked layer by layer in the vacuum sealing cavity 7. When the soft continuum 5 expands, contracts and bends, the directional biomimetic adhesive material 3 will be misaligned, resulting in changes in the contact area between the layers. Different negative pressures introduced into the vacuum sealing cavity 7 will cause different contact lengths between the micro-nano array structure 301 and the surface of the soft continuum 5, controlling the magnitude of the adhesive force, thereby achieving adjustable stiffness of the soft actuator.

[0030] Preferably, by introducing different air pressures into the three air chambers 501 on the soft continuum 5, different stresses and strains will be generated on the material limiting surface and the moving surface of the soft continuum 5, so the actuator can achieve bending at different angles and orientations. By introducing the same air pressure into the three air chambers 501 on the soft continuum 5, the entire actuator can achieve overall extension and retraction.

[0031] The mechanical analysis of the actuator during extension and retraction is as follows:

[0032] F = F P +F a -F eo -F ei

[0033] In the formula, F is the output force of the soft actuator; F P The pressure generated by the pressure difference between the internal cavity pressure of the soft continuum 5 and atmospheric pressure; F eo F is the elastic force of the sealing membrane 2; ei For the elastic force of the soft continuum 5; F a Peeling force provided for directional biomimetic adhesive material 3.

[0034] The mechanical analysis of the driver under bending conditions is as follows:

[0035] M = M P +M a -M eo -M ei

[0036] In the formula, M is the torque output by the soft actuator; M p M is the torque generated by the pressure difference between the soft actuator's internal cavity pressure and atmospheric pressure on the outer end cap; eo and M ei These are the torques generated by the elastic forces of the sealing membrane 2 and the soft continuum 5, respectively; M a The torque generated by the peeling force of the directional biomimetic adhesive material 3.

[0037] Analysis of the actuator's extension and bending moment mechanics reveals that the directional biomimetic adhesive material 3 can generate peeling force or peeling torque under negative pressure, which can increase the actuator's stiffness.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Additionally, in the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the accompanying drawings of this invention, the fill patterns are only for distinguishing layers and do not constitute any other limitation.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A stiffness-adjustable soft actuator based on directional biomimetic adhesive materials, characterized in that, The device includes a front cover (1), a sealing membrane (2), a directional biomimetic adhesive material (3), a soft continuum (5), and a rear cover (6). The front cover (1) and the rear cover (6) are connected by the sealing membrane (2), forming a sealed cavity inside the sealing membrane (2). The soft continuum (5) is located in the sealed cavity inside the sealing membrane (2), and a vacuum sealing cavity (7) is provided between the surface of the soft continuum (5) and the inside of the sealing membrane (2). The directional biomimetic adhesive material (3) is located in the vacuum sealing cavity (7) and adhered to the surface of the soft continuum (5). The soft continuum (5) has multiple air chambers (501). The front cover (1) has multiple positive pressure air holes (102) and vacuum air holes (101). Each positive pressure air hole (102) is connected to an air chamber (501), and the vacuum air hole (101) is connected to the vacuum sealing cavity (7). The positive pressure vent (102) is used to connect the external positive pressure and the air chamber (501). When multiple positive pressure vents (102) are filled with different air pressures, the soft continuum (5) is controlled to bend. When multiple positive pressure vents (102) are filled with the same air pressure, the soft continuum (5) is controlled to expand and contract. The vacuum vent (101) is used to connect the external negative pressure with the vacuum sealing cavity (7). The directional biomimetic adhesive material (3) is stacked layer by layer in the vacuum sealing cavity (7). When the soft continuum (5) stretches or bends, the directional biomimetic adhesive material (3) is misaligned, resulting in changes in the contact area between the layers. Different negative pressures introduced into the vacuum sealing cavity (7) cause different contact lengths between the directional biomimetic adhesive material (3) and the surface of the soft continuum (5), controlling the magnitude of the adhesion force, thereby realizing the stiffness adjustment of the soft actuator. The contact surface between the directional biomimetic adhesive material (3) and the soft continuum (5) is provided with a micro-nano array structure (301). Different negative pressures introduced into the vacuum sealing cavity (7) cause different contact lengths between the micro-nano array structure (301) and the surface of the soft continuum (5), controlling the magnitude of the adhesion force, thereby realizing the adjustable stiffness of the soft actuator. By introducing the same amount of air pressure into the air chamber (501) of the soft continuum (5), the entire actuator achieves overall extension and retraction; The mechanical analysis of the actuator during extension and retraction is as follows: ； In the formula, F is the output force of the soft actuator; F P The pressure generated by the pressure difference between the cavity pressure and atmospheric pressure of the soft continuum (5); F eo The elastic force of the sealing membrane (2); F ei The elastic force of the soft continuum (5); F a The peeling force provided for the directional biomimetic adhesive material (3); The mechanical analysis of the driver under bending conditions is as follows: ； In the formula, M is the torque output by the soft actuator; M p M is the torque generated by the pressure difference between the soft actuator's internal cavity pressure and atmospheric pressure on the outer end cap; eo and M ei These are the torques generated by the elastic forces of the sealing membrane (2) and the soft continuum (5), respectively; M a The torque generated by the peeling force of the directional biomimetic adhesive material (3); Analysis of the extensibility and bending moment of the actuator shows that the directional biomimetic adhesive material (3) generates peeling force or peeling torque under negative pressure, which increases the stiffness of the actuator.

2. The stiffness-adjustable soft actuator based on directional biomimetic adhesive material according to claim 1, characterized in that, The soft continuum (5) has several clamps (4) on its outer side.

3. The stiffness-adjustable soft actuator based on directional biomimetic adhesive material according to claim 2, characterized in that, The soft continuum (5) has several clamp mounting ports (502) on its outer side.

4. The stiffness-adjustable soft actuator based on directional biomimetic adhesive material according to claim 1, characterized in that, The directional biomimetic adhesive material (3) is provided with several thread holes (302), and the directional biomimetic adhesive material (3) is wrapped around the surface of the soft continuum (5) by passing a thread through the thread holes (302).

5. The stiffness-adjustable soft actuator based on directional biomimetic adhesive material according to claim 1, characterized in that, There are three positive pressure vents (102) and three air chambers (501), and the positive pressure vents (102) are distributed in a triangular pattern.

Images