A variable stiffness hybrid dual-mode two-finger soft gripper and its grasping method

Abstract

The present invention discloses a variable-rigidity hybrid dual-mode two-finger soft gripper and a grasping method thereof, belonging to the field of robotic grasping technology. The gripper comprises a drive structure, a grasping structure, a rotational connection structure, and a traction structure. The drive structure and the grasping structure are rotationally connected via the rotational connection structure, and the drive structure pulls the grasping structure via the traction structure. The grasping structure comprises two symmetrically arranged grippers, each comprising a spring steel sheet, a plurality of heating sheets, and a plurality of memory alloy sheets. The present invention provides a variable-rigidity two-finger soft gripper having two grasping modes: enveloping and clamping. The gripping mode can be switched in real time to adapt to the grasping process of different objects. The designed variable-rigidity two-finger soft gripper can ensure both the gripping force of a rigid hand and the flexibility of a soft hand, effectively avoiding damage or destruction of objects.

Description

Technical Field

[0001] The present invention relates to the technical field of robot grasping, and in particular to a variable-rigidity hybrid dual-modal two-finger soft grasper and a grasping method thereof. Background Art

[0002] In robotic grasping operations, traditional rigid manipulators achieve grasping through rigid contact, which easily poses a risk of damage to the manipulator itself and the target being grasped. To achieve compliant operations, the robot needs to be equipped with expensive sensing equipment and complex closed-loop control algorithms. Therefore, soft grippers made of flexible materials have emerged in recent years. The overall structure of the fingers is soft and adaptable. At the same time, the low contact stiffness provides a natural protective effect on the object and is less likely to cause damage to the surface of the grasped object. However, softness can also lead to insufficient gripping force. Therefore, it is particularly important to develop various variable stiffness gripper mechanisms that have the advantages of stiffness and soft feel. To this end, a variable stiffness hybrid dual-modal two-finger soft gripper and its grasping method are proposed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: how to solve the problem that the traditional two-finger hand grasping action is single and does not consider the specific grasping mode suitable for the object, and the rigid hand grasping is prone to damage or destruction of the object, and the soft hand has insufficient grasping force. A variable stiffness hybrid dual-mode two-finger soft gripper is provided.

[0004] The present invention solves the above technical problems through the following technical solutions, which include: a driving structure, a grasping structure, a rotation connection structure, and a traction structure; the driving structure and the grasping structure are rotationally connected through the rotation connection structure, and the driving structure pulls the grasping structure through the traction structure;

[0005] The grasping structure includes two symmetrically arranged claws, each of which includes a spring steel sheet, a plurality of heating sheets, and a plurality of memory alloy sheets. The spring steel sheet is rotatably connected to the driving structure via the rotating connection structure. The plurality of heating sheets are spaced apart on the outer surface of the spring steel sheet, and the plurality of memory alloy sheets are spaced apart on the inner surface of the spring steel sheet.

[0006] Furthermore, the driving structure comprises a top bracket, a top cover plate, and a digital servo, wherein the top cover plate is arranged at the upper end of the top bracket, and the digital servo is arranged inside the top bracket.

[0007] Furthermore, a connecting block is provided on the outer surface of the digital servo, a mounting seat is provided inside the top bracket, and the connecting block is detachably connected to the mounting seat.

[0008] Furthermore, the outer cover of the gripper is provided with a silicone cover that matches its outer shape.

[0009] Furthermore, the inner surface of the silicone sleeve is provided with a plurality of anti-slip strips.

[0010] Furthermore, the rotating connection structure includes a first fixed seat, a second fixed seat, a torsion spring, and a cylindrical pin. The second fixed seat is arranged at the top of the spring steel sheet, and the first fixed seat is arranged at the lower end of the top bracket. The second fixed seat and the first fixed seat are rotationally connected through the cylindrical pin and the torsion spring.

[0011] Furthermore, the traction structure includes a traction rope and multiple connecting seats, which are arranged at intervals on the inner surface of the spring steel sheet and staggered with the memory alloy sheet. One end of the traction rope is connected to the digital servo, and the other end passes through the top bracket, the second fixed seat and each connecting seat in sequence and is fixedly connected to the connecting seat at the very end.

[0012] The present invention also provides a grasping method of a variable stiffness hybrid dual-mode two-finger soft gripper, which grasps an object using the variable stiffness hybrid dual-mode two-finger soft gripper, comprising the following steps:

[0013] S1: Based on the properties of the contact surface between the two-finger soft gripper and the object, select the envelope grasping mode or the clamping mode for grasping;

[0014] S2: When the enveloping grasping mode is selected, the traction rope is rotated by the digital servo to drive the spring steel sheet to bend from the bottom up, and the bending deformation fits the outer surface of the object as much as possible, thus achieving the enveloping state; when the clamping mode is selected, the heating plate is powered by a DC source and the temperature rises. The memory alloy sheet on the inner surface of the spring steel sheet bends into a C shape as the temperature rises. Under the restriction of the silicone sleeve, the inner side of the gripper is flat and non-concave. Finally, the traction rope is pulled to make the two grippers move closer to the center of the object, forming the clamping mode.

[0015] Furthermore, when the contact surface between the two-finger soft gripper and the object has a curvature change, such as apples, ping-pong balls, teddy bears, etc., the object is grasped through the envelope grasping mode; when the contact surface between the two-finger soft gripper and the object does not change in curvature, such as square objects such as the Rubik's Cube and flat objects, the object is grasped through the clamping mode. The above grasping mode classification is a summary result of the rules obtained by deep reinforcement learning based on a large amount of data.

[0016] The present invention is a variable-rigidity two-finger soft hand with two grasping modes: enveloping and clamping. The grasping mode can be converted in real time to adapt to the grasping process of different objects. The designed variable-rigidity two-finger soft hand can ensure both the gripping force of a rigid hand and the flexibility of a soft hand, which can effectively avoid destruction or damage to objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is an exploded view of a variable stiffness hybrid dual-mode two-finger soft gripper according to an embodiment of the present invention;

[0018] Figure 2 Schematic diagram of the overall structure of a variable stiffness hybrid dual-mode two-finger soft gripper in an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of the gripping mode of the variable stiffness hybrid dual-mode two-finger soft gripper in an embodiment of the present invention;

[0020] Figure 4 Schematic diagram of the envelope grasping mode of the variable stiffness hybrid dual-mode two-finger soft gripper in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0022] like Figure 1 、 2 As shown, this embodiment provides a technical solution: a variable stiffness hybrid dual-mode two-finger soft gripper, including a driving structure and a grasping structure;

[0023] The drive structure includes a top bracket 11, a top cover 12, and a digital servo 13. The top cover 12 is disposed at the upper end of the top bracket 11 and is detachably connected thereto. The digital servo 13 is installed inside the top bracket 11 and is detachably connected thereto. The top cover 12 is connected to the end of the UR5 robotic arm, and the digital servo 13 is controlled by an Arduino board comprising hardware and software (Arduino IDE).

[0024] A connecting block 131 is provided on the outer surface of the digital servo 13 , and a mounting seat 111 is provided inside the top bracket 11 . The connecting block 131 and the mounting seat 111 are detachably connected via connecting bolts, thereby achieving a detachable connection between the digital servo 13 and the top bracket 11 .

[0025] The grasping structure includes two grippers symmetrically arranged at the lower end of the top bracket 11 , and both grippers are rotatably connected to the top bracket 11 , and the grasping action is achieved under the control of the digital servo 13 .

[0026] The gripper includes a spring steel sheet 21 (elastic metal sheet), multiple heating sheets 22, and multiple memory alloy sheets 23. The upper end of the spring steel sheet 21 is rotatably connected to the lower end of the top bracket 11. The multiple heating sheets 22 are arranged at intervals on the outer surface of the spring steel sheet 21 and fixedly connected thereto. The multiple memory alloy sheets 23 are arranged at intervals on the inner surface of the spring steel sheet 21 and fixedly connected thereto.

[0027] In this embodiment, two heating plates 22 are provided on a single gripper, spaced longitudinally on the outer surface of the spring steel sheet 21. The longitudinal distribution of the heating plates 22 allows for uniform heating of the memory alloy sheet 23 through heat conduction from the spring steel sheet 21. The heating plates 22 are controlled on and off by a DC power source.

[0028] In this embodiment, the number of the memory alloy sheets 23 on a single gripper is three, and the three memory alloy sheets 23 are arranged laterally and spaced apart on the inner surface of the spring steel sheet 21. The installation position of the memory alloy sheets 23 is designed based on the position of human finger joints.

[0029] In this embodiment, the spring steel sheet 21 is shaped like a shovel.

[0030] In this embodiment, the outer cover of the gripper is provided with a silicone cover 24 that matches its shape, and a plurality of anti-slip strips 241 are provided at the lower end of the inner surface of the silicone cover 24. The silicone cover 24 and the anti-slip strips 241 are used together to provide a good anti-slip effect when grasping objects.

[0031] In this embodiment, the variable stiffness hybrid dual-modal two-finger soft gripper also includes a rotating connection structure, which includes a first fixed seat 43, a second fixed seat 41, a torsion spring, and a cylindrical pin 42. The second fixed seat 41 is arranged on the top of the spring steel sheet 21 and is detachably connected thereto. The first fixed seat 43 is arranged at the lower end of the top bracket 11 and is integrally formed therewith. The second fixed seat 41 and the first fixed seat 43 are rotatably connected through a torsion spring and a cylindrical pin 42, and the torsion spring is sleeved on the cylindrical pin 42.

[0032] The variable stiffness hybrid dual-mode two-finger soft gripper also includes a traction structure, which includes a traction rope 31 and multiple connecting seats 32. The multiple connecting seats 32 are arranged at intervals on the inner surface of the spring steel sheet 21 and are detachably connected thereto, and are staggered with the memory alloy sheet 23. One end of the traction rope 31 is connected to the digital servo 13 and is driven by the digital servo 13, and the other end passes through the top bracket 11, the second fixing seat 41, and each connecting seat 32 in sequence and is fixedly connected to the connecting seat at the end. Multiple connecting seats 32 are arranged on the inner surface of the spring steel sheet 21, and the traction ropes are sequentially connected and fixed to the ends of the spring steel sheet 21. When the variable stiffness hybrid dual-mode two-finger soft gripper performs an enveloping or gripping mode, it can control the bending movement of the gripper.

[0033] In this embodiment, the number of the connecting seats 32 on a single gripper is three.

[0034] It should be noted that experimental tests have shown that the memory alloy sheet 23 carried by this variable stiffness hybrid dual-modal two-finger soft gripper can undergo arch deformation at a temperature of about 50 degrees Celsius. This deformation can drive the spring steel sheet 21 to undergo elastic deformation. By changing the shape, the bending moment of the entire spring steel sheet 21 in the normal direction is also correspondingly improved.

[0035] During the initial heating phase, the entire spring steel sheet 21 remains flat and unaffected by the shape memory alloy sheet 23. After the heating temperature is raised above 50°C, the shape memory alloy sheet 23 fully deforms, and the spring steel sheet 21, simultaneously experiencing the traction force, also changes from flat to arched. The entire deformation process takes approximately 20 seconds, ensuring that the variable-stiffness hybrid dual-modal two-finger soft gripper can rapidly deform in actual use.

[0036] like Figure 3 、 4 As shown, the working principle is: when the heating plate 22 is in the starting heating state, the memory alloy sheet 23 shrinks toward the inside of the claw due to its properties, and is C-shaped when viewed from above, driving the spring steel sheet 21 to produce an arched deformation. At this time, the bending moment of the spring steel sheet 21 in the normal direction is greatly increased, and the maximum grasping force is improved. At this time, the grasping mode is switched to clamping; when the heating plate 22 is turned off for heating, the memory alloy sheet 23 is flattened, and the bending moment in the normal direction is small, so that the spring steel sheet 21 can bend to the opposite side, and the grasping mode is switched to enveloping.

[0037] To sum up, the variable stiffness hybrid dual-mode two-finger soft gripper of the above embodiment is a variable stiffness two-finger soft hand with two grasping modes of enveloping and clamping, and can convert the grasping mode in real time to adapt to the grasping process of different objects. The designed variable stiffness two-finger soft hand can ensure both the gripping force of a rigid hand and the flexibility of a soft hand, which can effectively avoid destruction or damage to objects.

[0038] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A grasping method of a variable stiffness hybrid dual-mode two-finger soft gripper, characterized in that: Grasping an object using a variable stiffness hybrid dual-mode two-finger soft gripper includes the following steps: S1: Based on the properties of the contact surface between the two-finger soft gripper and the object, select the envelope grasping mode or the clamping mode for grasping; S2: When the enveloping grasping mode is selected, the traction rope is driven by the rotation of the digital servo to drive the spring steel sheet to bend from the bottom up. The bending deformation fits the outer surface of the object, thus achieving an enveloping state. When the clamping mode is selected, the heating plate is powered by a DC power source and the temperature rises. The memory alloy sheet on the inner surface of the spring steel sheet bends into a C shape as the temperature rises. Under the restraint of the silicone sleeve, the inner side of the gripper is flat and not concave. Finally, the traction rope is pulled to make the two grippers move closer to the center of the object, forming a gripping mode. In step S1, when the contact surface between the two-finger soft gripper and the object has a curvature change, the object is grasped using the envelope grasping mode; when the contact surface between the two-finger soft gripper and the object has no curvature change, the object is grasped using the clamping mode; The variable stiffness hybrid dual-mode two-finger soft gripper includes: a driving structure, a grasping structure, a rotation connection structure, and a traction structure; the driving structure and the grasping structure are rotationally connected via the rotation connection structure, and the driving structure pulls the grasping structure via the traction structure; The grasping structure includes two symmetrically arranged claws, each of which includes a spring steel sheet, a plurality of heating sheets, and a plurality of memory alloy sheets. The spring steel sheet is rotatably connected to the driving structure via the rotating connection structure. The plurality of heating sheets are spaced apart on the outer surface of the spring steel sheet, and the plurality of memory alloy sheets are spaced apart on the inner surface of the spring steel sheet. The driving structure comprises a top bracket, a top cover plate, and a digital servo, wherein the top cover plate is arranged at the upper end of the top bracket, and the digital servo is arranged inside the top bracket; The outer cover of the gripper is provided with a silicone cover that matches its shape; The rotation connection structure includes a first fixing seat, a second fixing seat, a torsion spring, and a cylindrical pin. The second fixing seat is arranged on the top of the spring steel sheet, and the first fixing seat is arranged at the lower end of the top bracket. The second fixing seat and the first fixing seat are rotationally connected through the cylindrical pin and the torsion spring. The traction structure includes a traction rope and multiple connecting seats. The multiple connecting seats are arranged at intervals on the inner surface of the spring steel sheet and staggered with the memory alloy sheet. One end of the traction rope is connected to the digital servo, and the other end passes through the top bracket, the second fixed seat and each connecting seat in sequence and is fixedly connected to the connecting seat at the end.

2. The grasping method of the variable stiffness hybrid dual-mode two-finger soft gripper according to claim 1 is characterized by: The outer surface of the digital servo is provided with a connecting block, the interior of the top bracket is provided with a mounting seat, and the connecting block is detachably connected to the mounting seat.

3. The grasping method of the variable stiffness hybrid dual-mode two-finger soft gripper according to claim 2 is characterized by: The inner surface of the silicone sleeve is provided with a plurality of anti-slip strips.

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