A controllable friction bionic flexible gripping device

Abstract

The application discloses a controllable friction bionic flexible gripping device, and relates to the technical field of clamping equipment. The controllable friction bionic flexible gripping device comprises a gripping device body, the gripping device body is provided with a flexible gripper, a bionic variable-rigidity friction regulation layer is arranged on a gripping surface of the flexible gripper, the bionic variable-rigidity friction regulation layer comprises a variable-rigidity shape memory resin layer and a heating structure capable of heating the variable-rigidity shape memory resin layer, and an orientation rigidity array capable of contacting a clamping piece is arranged on the variable-rigidity shape memory resin layer. The controllable friction bionic flexible gripping device can realize mutual conversion between two states of flexible contact in a low elastic modulus, low rotational rigidity and high contact area attaching stage and mechanical locking in a high elastic modulus, high rotational rigidity and high static friction coefficient gripping stage, and the stability of gripping is improved.

Description

Technical Field

[0001] This invention relates to the field of clamping equipment technology, and in particular to a biomimetic flexible gripping device with controllable friction. Background Technology

[0002] Flexible gripping devices are flexible actuators that maintain their flexibility to grasp target objects without causing damage. They have attracted widespread attention due to their simple actuation methods, good environmental adaptability, and excellent performance in establishing safe and coexisting interactions with humans. However, due to their inherent structural flexibility and bending characteristics, they exhibit instability under complex gripping conditions. Their gripping end interface (e.g., silicone elastomers) is usually composed of low-stiffness materials, and insufficient stiffness and friction control capabilities result in insufficient gripping load capacity and gripping stability. Gripping stability depends on the contact state and friction coefficient of the contact surfaces. Therefore, to improve gripping stability, common methods include changing the gripper stiffness or altering the friction coefficient between the gripper and the object's contact surface.

[0003] Existing flexible gripping devices use grippers made of composite adjustable stiffness shape memory materials, which gives the gripper the ability to vary stiffness. While maintaining the flexibility and adaptability of the gripper, the load capacity of the flexible gripper is improved. However, in terms of gripping stability, the material of the flexible gripper is usually low modulus, which makes it easy to undergo large deformation under the action of interfacial shear force. The gripping ability is weaker than that of rigid grippers, and it is easy to cause delamination.

[0004] The main existing approaches to improving the surface friction of grippers include increasing the coefficient of friction of the material surface. The materials used mainly include polydimethylsiloxane, silicone, or biomimetic high-adhesion materials based on the above materials. These materials are characterized by a high coefficient of friction, low elastic modulus, and good flexibility, but they lack stiffness during the gripping stage and have limited gripping quality.

[0005] Therefore, it is necessary to design a highly stable gripping end surface. The gripping device in this invention focuses on controlling the stiffness of the contact area of ​​the gripper surface during both the contact and gripping stages. In the first stage, establishing contact (applying interfacial normal force), sufficient flexibility of the gripper material is required to increase the contact area. In the second stage, the gripping stage (applying interfacial shear force), maintaining the static friction of the interface is necessary. By adjusting its own surface stiffness and friction characteristics according to the surface stiffness and roughness of different target surfaces, gripping stability is improved. Summary of the Invention

[0006] The purpose of this invention is to provide a biomimetic flexible gripping device with controllable friction to solve the problems existing in the prior art. It can realize the mutual conversion between two states: flexible contact with low elastic modulus, low rotational stiffness and high contact area during the attachment stage and mechanical locking with high elastic modulus, high rotational stiffness and high static friction coefficient during the gripping stage, and improve the stability of gripping.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a biomimetic flexible gripping device with controllable friction, including a gripping device body. The gripping device body has a flexible gripper. A biomimetic variable stiffness friction control layer is provided on the gripping surface of the flexible gripper. The biomimetic variable stiffness friction control layer includes a variable stiffness shape memory resin layer and a heating structure capable of heating the variable stiffness shape memory resin layer. An orientation rigid array capable of contacting a clamping member is provided on the variable stiffness shape memory resin layer.

[0009] Preferably, the orientation rigid array includes a plurality of uniformly arranged orientation rigid units, and the variable stiffness shape memory resin layer has an accommodating space for placing the orientation rigid units, and the ends of the orientation rigid units can extend out from the accommodating space.

[0010] Preferably, the orientation rigid unit is made by 3D printing photosensitive resin.

[0011] Preferably, the orientation rigid unit is teardrop-shaped.

[0012] Preferably, the variable stiffness shape memory resin layer has recesses corresponding to each of the accommodating spaces.

[0013] Preferably, the heating structure is a stretchable resistance heating circuit arranged in a serpentine pattern.

[0014] Preferably, the stretchable resistance heating circuit is formed by printing conductive ink using a direct-write ink printing method and then curing it.

[0015] The present invention achieves the following technical effects compared to the prior art:

[0016] The friction-controllable biomimetic flexible gripping device provided by this invention utilizes the variable stiffness characteristics of a variable stiffness shape memory resin layer to design and fabricate an array structure with adjustable stiffness, resembling a toothed tongue surface. This allows for the switching between two states: flexible contact with low elastic modulus, low rotational stiffness, and high contact area during the attachment stage, and mechanical locking with high elastic modulus, high rotational stiffness, and high static friction coefficient during the gripping stage. Furthermore, after contacting the surface of the object being gripped, the friction-controllable biomimetic flexible gripping device provided by this invention will not detach the object when pulled in any direction, achieving stable gripping in multiple directions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the gripping device body provided by the present invention;

[0019] Figure 2 An exploded view of the biomimetic variable stiffness friction control layer provided by the present invention;

[0020] Figure 3 An assembly diagram of the biomimetic variable stiffness friction control layer provided by the present invention;

[0021] Figure 4 A schematic diagram of the bottom structure of the biomimetic variable stiffness friction control layer provided by the present invention;

[0022] Figure 5 A cross-sectional view of the biomimetic variable stiffness friction control layer provided by the present invention;

[0023] Figure 6 for Figure 5 A partial structural diagram of part A in the middle;

[0024] In the figure: 1-Bionic variable stiffness friction control layer; 11-Oriented rigid array; 12-Variable stiffness shape memory resin layer; 13-Stretchable resistance heating circuit; 2-Flexible finger module; 3-Sliding mounting plate; 4-Flange connection module; 5-Accommodation space; 6-Dent. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The purpose of this invention is to provide a biomimetic flexible gripping device with controllable friction to solve the problems existing in the prior art. It can realize the mutual conversion between two states: flexible contact with low elastic modulus, low rotational stiffness and high contact area in the attachment stage and mechanical locking with high elastic modulus, high rotational stiffness and high static friction coefficient in the gripping stage, and improve the stability of gripping.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] This invention provides a biomimetic flexible gripping device with controllable friction, such as Figures 1-6 As shown, in this embodiment, the device includes a gripping device body, which includes a flange connection module 4, a sliding mounting plate 3, and a flexible finger module 2. The gripping device body has a flexible gripper, and a biomimetic variable stiffness friction control layer 1 is attached to the gripping surface of the flexible gripper with silicone adhesive. The biomimetic variable stiffness friction control layer 1 includes a variable stiffness shape memory resin layer 12 and a heating structure that can heat the variable stiffness shape memory resin layer 12. An orientation rigid array 11 that can contact the clamping member is provided on the variable stiffness shape memory resin layer 12. The orientation rigid array 11 is embedded in the variable stiffness shape memory resin layer 12 in an orderly manner.

[0029] The orientation rigid array 11 includes a plurality of uniformly arranged orientation rigid units. The variable stiffness shape memory resin layer 12 has an accommodating space 5 for placing the orientation rigid units. The ends of the orientation rigid units can extend out of the accommodating space 5 to contact the clamping member. The surface of the orientation rigid units can fit against the inner wall of the accommodating space 5 to limit the orientation rigid units and prevent them from falling out of the accommodating space 5.

[0030] The orientation rigid unit is made by 3D printing photosensitive resin. The orientation rigid array 11 is placed in a prepared mold, and variable stiffness shape memory resin is poured into the mold and then cured to form a variable stiffness shape memory resin layer 12. In addition to photosensitive resin, the orientation rigid unit can also be made of other materials with equivalent modulus.

[0031] The orientation rigid unit is teardrop-shaped so that it can better fit the surface of the clamping part. Depending on the requirements, the orientation rigid unit can be set to other different shapes.

[0032] The variable stiffness shape memory resin layer 12 has a recess 6 corresponding to each accommodating space 5. The recess 6 is located at the top of the orientation rigid unit and is spherical. The purpose of setting the recess 6 is to increase the rotational freedom of the orientation rigid unit in the accommodating space 5, so that after the gripping end surface comes into contact with the clamping part, the orientation rigid unit can better fit with the surface of the clamping part to increase friction. The recess 6 is prepared by immersing the top of the orientation rigid array 11 in paraffin wax, then curing the paraffin wax, and then casting the variable stiffness shape memory resin. After the resin is cured, the spherical paraffin wax is removed to obtain the array recess 6.

[0033] The heating structure is a stretchable resistance heating circuit 13 arranged in a serpentine pattern.

[0034] The stretchable resistance heating circuit 13 is formed by printing conductive ink on the bottom end of the variable stiffness shape memory resin layer 12 according to a pre-set printing path using direct-write ink printing (DIW) and then curing it. The stretchable resistance heating circuit 13 uses commercial conductive ink, which has good stretching properties. When the biomimetic variable stiffness friction control layer 1 on the gripping end surface bends and deforms, the stretchable resistance heating circuit 13 can be stretched while ensuring good conductivity and providing Joule heating.

[0035] The friction-controllable biomimetic flexible gripping device provided by this invention requires energizing the stretchable resistance heating circuit 13 to generate Joule heating before gripping. When the temperature reaches the glass transition temperature of the variable stiffness shape memory resin layer 12, the surface stiffness of the gripper decreases sharply. The device then opens the gripper to grasp the object and closes it to allow the biomimetic variable stiffness friction control layer 1 on the gripper surface to adaptively fit with the clamping element. At this point, the oriented rigid array 11 can effectively interlock with the surface of the clamping element. Then, energizing the stretchable resistance heating circuit 13 is stopped, and the surface temperature of the variable stiffness shape memory resin layer 12 decreases accordingly. When the temperature falls below the glass transition temperature of the variable stiffness shape memory resin layer 12... After the temperature change, the stiffness of the shape memory resin layer 12 increases, the rotational stiffness of the orientation rigid array 11 increases, and the mechanical interlocking formed between the orientation rigid array 11 and the surface of the clamping member will not fail due to the relative slippage tendency of the gripping interface. This significantly increases the static friction of the interface, and the target object is firmly gripped by the gripper. Then, it can be transferred or used for other tasks. To release the object, it is only necessary to reheat it with electricity. When the temperature is higher than the glass transition temperature of the shape memory resin layer, the gripper can open to release the object. At this time, due to its shape memory characteristics, the structure of the gripper surface is restored to its original state, and the orientation rigid array 11 can also be restored to its orderly arrangement. Then, the gripping work of the next cycle can be carried out.

[0036] The biomimetic variable stiffness friction control layer 1 on the gripping end surface of the present invention can meet the different requirements of the gripping device for surface contact stiffness and friction in two stages when performing a gripping task: the attachment stage requires the gripper surface to have high flexibility in order to increase the contact area and the degree of fitting with the micro-protrusions on the surface of the target object; the gripping stage requires the gripper surface to have high stiffness so that after the gripping load is applied, the contact surface and the micro-protrusions can be kept in a static friction state to achieve stable mechanical fitting between the two contact surfaces.

[0037] Because this invention has an elastic modulus of several GPa at room temperature, it can greatly improve the load-bearing capacity of flexible grippers. Furthermore, due to the simple manufacturing process of this invention, it can produce surfaces of different shapes, allowing for adaptation and installation to different models of flexible grippers. This invention can also be used to increase the gripping stability of rigid grippers.

[0038] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A controllably frictional bionic flexible gripping device comprising a gripping device body having a flexible gripper, characterized in that: The flexible gripper has a biomimetic variable stiffness friction control layer on its gripping surface. This layer includes a variable stiffness shape memory resin layer and a heating structure capable of heating the resin layer. The resin layer has an orientation rigid array that can contact the clamping element. The orientation rigid array includes multiple uniformly arranged orientation rigid units. The resin layer has accommodating spaces for placing these units, and the ends of the units can extend from these spaces. Each orientation rigid unit is teardrop-shaped. The resin layer has recesses corresponding to each accommodating space.

2. The controllably frictional bionic flexible gripping device according to claim 1, characterized in that: The orientation rigid unit is made by 3D printing photosensitive resin.

3. The friction-controllable biomimetic flexible gripping device according to claim 1, characterized in that: The heating structure is a stretchable resistance heating circuit arranged in a serpentine pattern.

4. The friction-controllable biomimetic flexible gripping device according to claim 3, characterized in that: The stretchable resistance heating circuit is formed by printing conductive ink using a direct-write ink printing method and then curing it.

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