A multi-grasping mode soft gripper based on bistable origami

Abstract

The present invention discloses a multi-grasping mode soft gripper based on bistable origami, which comprises a bistable origami structure, a rigid connector, soft fingers, an origami driver, a sealing bottom plate and an inflation system. The multi-grasping mode soft gripper based on bistable origami of the present invention can realize a fast passive grasping action or a fast active grasping (releasing) action or an active slow grasping (releasing) action by driving the origami driver and the bistable origami structure with air pressure. The bistable origami structure is an arched origami structure, which has two stable states: an initial state and a grasping state. The origami driver is a prismatic foldable structure. The soft gripper has the advantages of controllable grasping mode, controllable response speed and low cost, and can be applied to a space capture system to grasp fast-moving objects; it can also be applied to the operator of an industrial robot to grasp various fragile objects quickly and repeatedly.

Description

Technical Field

[0001] The invention relates to soft robot technology, in particular to a soft gripper imitating a human hand based on bistable origami. Background Art

[0002] Soft robotics technology has received widespread attention from the society and has developed rapidly. Compared with traditional rigid grippers, soft grippers are generally made of soft materials or structures that can undergo large deformations. They have the characteristics of good flexibility and strong adaptability, and can effectively grasp various shapes or fragile objects. Most soft grippers only have a single grasping mode. For example, soft grippers that rely on elastic deformation to grasp objects can only grasp objects slowly, but cannot achieve fast grasping; bistable grippers that rely on steady-state changes to grasp objects can only grasp objects quickly, but cannot achieve slow grasping, etc., and this fast grasping is not friendly to fragile objects. These problems hinder the further application of soft grippers in practice. Summary of the invention

[0003] The purpose of the present invention is to improve the shortcomings of traditional soft grippers such as slow grasping speed, single grasping mode, and complex structure, and to provide a multi-grasping mode soft gripper based on bistable origami.

[0004] The technical solution of the present invention is as follows:

[0005] A multi-grasping mode soft gripper based on bistable origami includes a bistable origami structure, a rigid connector, soft fingers, an origami driver, a sealed bottom plate, and an inflation and exhaust system. The soft fingers are connected to the bistable origami structure through a rigid connector; the bistable origami structure includes a bistable arched origami structure and a flexible side wall, the upper end of the flexible side wall is fixedly connected to the bistable arched origami structure, and the lower end is fixed to the sealed bottom plate; the bistable origami structure and the sealed bottom plate constitute an external origami airbag; the origami driver is arranged in the external origami airbag, and the origami driver includes an upper and lower end plate and a flexible origami side wall, and the three together constitute an internal origami airbag, wherein the upper end plate is connected to the inner side of the bistable arched origami structure, and the lower end plate is fixed to the sealed bottom plate. The bistable origami structure is made of soft material (TPU) 3D printing, and PVC plates are attached to both the inner and outer sides of the bistable origami structure (the crease position needs to be reserved when attaching), and the shape of the PVC plate is similar to the folding surface of the bistable origami structure. The crease position of the bistable origami structure is a soft material (TPU), so the bistable origami structure can be folded and deformed according to the arrangement of the crease. The bistable origami structure has two stable states: an initial state and a grasping state. When an external force is applied to the top of the bistable origami structure, it will quickly switch from the initial state to the grasping state. During this process, the soft fingers connected to the bistable origami structure will quickly move towards each other to achieve a rapid passive grasping action. Applying negative pressure to the internal origami airbag can also make the bistable origami structure quickly switch from the initial state to the grasping state, achieving rapid active grasping. When a positive pressure is applied to the internal origami airbag, the bistable origami structure will quickly switch from the grasping state to the initial state to achieve a rapid release action. By repeating the above driving method, the soft gripper can achieve repeated and rapid grasping and releasing actions. In addition, when negative pressure is applied inside the inner origami airbag and positive pressure is applied inside the outer origami airbag, the bistable origami structure can slowly switch from the initial state to the grasping state, achieving a slow active grasping action. When positive pressure is applied inside the inner origami airbag and negative pressure is applied inside the outer origami airbag, the bistable origami structure can slowly switch from the grasping state to the initial state, achieving a slow active release action.

[0006] In the above technical solution, further, the basic origami unit is arrayed 4 times along the X and Y axes respectively to obtain the folding pattern of the flexible origami side wall. In addition, the flexible origami side wall is composed of two layers of plastic film and a PVC plate sandwiched therein, and the shape of the PVC plate is similar to the shape of the folding surface of the origami driver (the PVC plate needs to avoid the crease position when placed). The crease position of the origami driver is a deformable plastic film, so the origami driver can undergo axial elongation or contraction deformation according to the arrangement of the crease. The thickness of the plastic film is small (0.05mm), so the stiffness of the plastic film as a crease is also small, and further, the energy consumed by the folding of the crease is also small, which is conducive to using the energy input by the air pressure mainly to cause the stable state conversion of the bistable origami structure and improve energy efficiency. The upper and lower end plates of the origami driver are both made of 3D printing, and the upper end plate is attached to the inner side of the bistable origami structure to ensure that the two can move at the same time. The lower end plate is a flat thin plate, and an air hole is left on the thin plate, through which the internal origami airbag can be inflated and evacuated.

[0007] Furthermore, the soft fingers are made of Ecoflex material by mold casting. The rigid connector is made of resin material by 3D printing. One end of the rigid connector is a triangular thin plate, which is pasted on the bistable origami structure, and the other end is a semi-cylinder, on which the soft fingers are nested. The two ends of the rigid connector have a certain angle to ensure the gripping effect of the soft gripper.

[0008] Furthermore, the sealing bottom plate is made of resin material by 3D printing. There are three air holes on the sealing bottom plate, the middle air hole is connected to the internal origami airbag; the other two air holes are connected to the external airbag, and the air pressure of each part of the external origami airbag changes relatively evenly by simultaneously inflating and deflating the two air holes. Under the condition that the air hole of the lower end plate of the origami driver is aligned with the middle air hole of the sealing bottom plate, the origami driver and the sealing bottom plate are pasted together. And the extension part of the end of the bistable origami structure is pasted together with the side of the sealing bottom plate.

[0009] The beneficial effects of the present invention are:

[0010] The bistable origami-based soft gripper adopted by the present invention realizes multiple grasping modes by air pressure drive. The gripper can realize fast passive grasping action or fast active grasping (releasing) action or active slow grasping (releasing) action by air pressure controlling the origami driver and the bistable origami structure according to different grasping requirements. The gripper has the advantages of controllable grasping mode, controllable response speed, low cost, etc., and has strong functionality and a wide range of applications: it can be applied to space capture systems to grasp fast-moving objects; it can also be applied to the operator of industrial robots to quickly and repeatedly grasp various fragile objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of a soft gripper with multiple grasping modes based on bistable origami;

[0012] Figure 2 It is the cross-sectional intention of a soft gripper with multiple grasping modes based on bistable origami;

[0013] Figure 3 It is a structural schematic diagram of a rigid connector;

[0014] Figure 4 It is a schematic diagram of the structure of the soft finger;

[0015] Figure 5 It is a schematic diagram of the structure of the sealing bottom plate;

[0016] Figure 6 :(1) is a schematic diagram of a bistable origami structure;(2) is a schematic diagram of a bistable arched origami structure;(3) is a schematic diagram of a bistable arched origami unit;(4) is a schematic diagram of a flexible side wall;(5) is a schematic diagram of a flexible side wall unit;

[0017] Figure 7 :(1) is a schematic diagram of the structure of the origami actuator; (2) is a schematic diagram of an origami unit; (3) is a schematic diagram of the upper end plate structure; (4) is a schematic diagram of the lower end plate structure.

[0018] Among them, 1: bistable origami structure; 2: rigid connector; 3: soft finger; 4: sealing bottom plate; 5: origami actuator; 6: PVC plate; 7: TPU crease; 8: bistable arched origami structure; 9: a unit of the bistable arched origami structure; 10: flexible side wall; 11: a unit of the flexible side wall; 12: upper end plate of the origami actuator; 13: plastic film crease; 14: lower end plate of the origami actuator. DETAILED DESCRIPTION

[0019] The scheme of the present invention is further explained below in conjunction with the accompanying drawings.

[0020] like Figure 1 The figure shows a multi-grasping mode soft gripper based on bistable origami of the present invention, which is mainly composed of a bistable origami structure 1, a rigid connector 2, soft fingers 3, a sealing base plate 4 and an origami driver 5.

[0021] like Figure 6(1) is a bistable origami structure 1 of the present invention. The bistable origami structure 1 is made of TPU material by 3D printing, and PVC plates 6 are attached to both the inner and outer sides thereof (avoiding the creases), and the shape of the PVC plates 6 is similar to the shape of the folding surface of the bistable origami structure 1. The crease 7 of the bistable origami structure 1 is located at a soft material (TPU), so the bistable origami structure 1 can be folded and deformed according to the arrangement of the crease 7. The bistable origami structure 1 has two stable states: an initial state and a grasping state. The bistable origami structure 1 includes a bistable arched origami structure 8 and a flexible side wall 10. The bistable arched origami structure 8 (such as Figure 6 (2)) Any adjacent peak folds and valley folds are evenly and alternately arranged at intervals of 30° along the circumferential direction. Each peak fold is extended for a period of time and then divided into two peak folds at a suitable position (point M in the figure, the angle between the peak fold and the plane formed by the two valley folds (i.e., the OPQ plane) is 67.97°. The flexible side wall 10 is a truncated cone folding surface structure and has a plurality of peak folds and valley folds. The bistable arched origami structure 8 includes a plurality of origami units (such as Figure 6 (3)), each origami unit includes a peak fold and two valley folds (the angle formed by two adjacent valley folds in space is 49.86°), and is divided into two peak folds at point M of the peak fold. The plane formed by the two peak folds and the bottom is used to fix the rigid connector 2 (such as Figure 3 , one end of the rigid connector 2 is a triangular thin plate), thereby fixing the soft finger on the bistable origami structure 1. The flexible side wall 10 is a truncated cone folding surface structure (such as Figure 6 (4)), and has a plurality of peak folds and valley folds, the peak folds of the flexible side wall 10 and the peak folds of the bistable arched origami structure 8 coincide with each other at the end points on the connecting surface, and the valley folds of the two coincide with each other at the end points on the connecting surface. Figure 6 (5) shows a unit 11 of the flexible side wall, which corresponds one-to-one to the origami unit of the bistable arched origami structure 8.

[0022] like Figure 7(1) is the origami driver 5 of the present invention. The flexible origami side wall is prism-shaped, and its basic origami unit is rectangular. A node D is set on the middle horizontal line of the basic origami unit. The node D connects three valley folds (AD, BD, DE) and a peak fold CD, and divides a basic origami unit into four parts consisting of two folding surfaces; the two folding surfaces are respectively a triangular folding surface surrounded by a peak fold CD, a valley fold (AD) and the unit boundary, and a trapezoidal folding surface surrounded by two valley folds (AD and DE) and the unit boundary. The folding pattern of the flexible origami side wall can be obtained by arranging the basic origami units 4 times along the X and Y axes respectively, and the flexible origami side wall can be formed by closing all the basic origami units around the Y direction. In addition, the flexible origami side wall is composed of two layers of inner and outer plastic films and a PVC plate 6 sandwiched therein, and the shape of the PVC plate 6 is similar to the shape of the folding surface of the origami driver 5. The folding position of the paper folding driver 5 is a deformable plastic film folding 13, so the paper folding driver 5 can be axially extended or contracted according to the arrangement of the folding.

[0023] Method for realizing axial contraction (extension) of origami actuator 5: (1) Axial contraction: When air is evacuated from origami actuator 5, the flexible origami side wall folds, and the distance between the upper and lower end plates 12 and 14 of the origami actuator gradually decreases. (2) Axial extension: When air is inflated from origami actuator 5, the flexible origami side wall unfolds, and the distance between the upper and lower end plates 12 and 14 of the origami actuator gradually increases.

[0024] Methods for implementing different grasping modes of the bistable origami structure 1: (1) Rapid passive grasping: When the pressure generated by the contact between the grasped object and the bistable origami structure 1 acts on its peak fold, the bistable arched origami structure expands in all directions, and its apex moves downward. As the contact pressure further increases, when the configuration of the bistable origami structure 1 exceeds the maximum state of elastic potential energy, it will quickly transform into a grasping state. (2) Rapid active grasping: When the internal origami airbag is evacuated, the contraction deformation of the origami actuator 5 provides a pulling force to the bistable origami structure 1. Under the action of the pulling force, as the negative pressure increases, the bistable origami structure 1 gradually passes the maximum position of elastic potential energy and quickly transforms into a grasping state. (3) Rapid active release: When the internal origami airbag is inflated, the origami actuator 5 generates axial extension, exerts pressure on the bistable origami structure 1, and as the positive pressure increases, the bistable origami structure 1 gradually passes the maximum position of elastic potential energy and quickly transforms into the initial state. Repeat (2) and (3), and the bistable gripper can achieve repeated and rapid grasping and releasing actions. (4) Slow active grasping: When negative pressure is applied inside the inner origami airbag and positive pressure is applied to the outer origami airbag, after appropriately reducing the value of the positive pressure, the configuration of the bistable origami structure 1 will gradually transition to the maximum potential energy state. When the configuration of the bistable origami structure 1 passes the maximum potential energy state, the negative pressure in the inner origami airbag is restored to the ambient pressure, and the positive pressure in the outer origami airbag is gradually reduced. During this process, the bistable origami structure 1 will slowly switch to the grasping state, achieving slow active grasping of objects. (5) Slow active release: When the bistable origami structure 1 is in the grasping state, the driving mode is opposite to (4), specifically, positive pressure is applied to the inner origami airbag and negative pressure is applied to the outer origami airbag. After the negative pressure value is appropriately reduced, the configuration of the bistable origami structure 1 will gradually transition to the maximum potential energy state. When the configuration of the bistable origami structure 1 passes the maximum potential energy state, the positive pressure in the inner origami airbag is restored to the ambient pressure, and the negative pressure in the outer origami airbag is gradually reduced. In this process, the bistable origami structure 1 will slowly switch to the initial state to achieve slow active release of the object. Repeating (4) and (5), the bistable gripper can achieve repeated slow grasping and releasing actions.

[0025] The multi-grasping mode soft gripper based on bistable origami of the present invention has the advantages of controllable grasping mode, controllable response speed, low cost, etc. The soft gripper can be applied to space capture systems to grasp fast-moving objects; it can also be applied to the operator of industrial robots to quickly and repeatedly grasp various fragile objects. It has broad application scenarios and strong development potential.

Claims

1. A multi-grasping mode soft gripper based on bistable origami, characterized in that: It includes a bistable origami structure, a rigid connector, a soft finger, an origami driver and a sealed bottom plate; the soft finger is connected to the bistable origami structure through a rigid connector; the bistable origami structure includes a bistable arched origami structure and a flexible side wall, the upper end of the flexible side wall is fixedly connected to the bistable arched origami structure, and the lower end of the flexible side wall is fixed on the sealed bottom plate; the bistable origami structure and the sealed bottom plate form an external origami airbag; the origami driver is arranged in the external origami airbag, the origami driver includes an upper and lower end plate and a flexible origami side wall, and the three together form an internal origami airbag, wherein the upper end plate is fixedly connected to the inner side of the bistable arched origami structure, and the lower end plate is fixed on the sealed bottom plate; the soft gripper drives the origami driver and the bistable origami structure through air pressure to realize a fast passive grasping action or a fast active grasping / releasing action or an active slow grasping / releasing action; Any adjacent peak folds and valley folds of the bistable arched origami structure are evenly and alternately arranged at intervals of 30° along the circumferential direction; each peak fold is divided into two peak folds after extending for a period, and the plane formed by the two peak folds and the bottom of the bistable arched origami structure is used to fix the rigid connector; the flexible side wall of the bistable origami structure is a truncated cone folding surface structure, and has a plurality of peak folds and valley folds, the peak folds of the flexible side wall and the peak folds of the bistable arched origami structure coincide with each other at the endpoints on the connecting surface, and the valley folds of the two coincide with each other at the endpoints on the connecting surface; the bistable origami structure has two stable states: an initial state and a grasping state, and can realize mutual switching between the initial state and the grasping state under the action of an external force, thereby driving the soft finger to quickly / slowly grasp / release the object; The flexible origami side wall is prism-shaped, and its basic origami unit is rectangular. A node is set on the middle horizontal line of the basic origami unit, and the node connects three valley folds and a peak fold, and divides a basic origami unit into four parts consisting of two folding surfaces; the two folding surfaces are respectively a triangular folding surface surrounded by a peak fold, a valley fold and a unit boundary, and a trapezoidal folding surface surrounded by two valley folds and a unit boundary; a plurality of basic origami units are arrayed along the X and Y directions and closed around the Y direction to form a flexible origami side wall; when the origami actuator is inflated or deflated, the flexible origami side wall realizes axial extension or contraction deformation according to the designed folds.

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