A finger with variable stiffness and a gripper thereof

Abstract

The present invention discloses a finger with variable stiffness and a clamping claw thereof, wherein the finger comprises a lever module, a spring module, a variable stiffness module and a base; the lever module comprises a finger lever, a connecting lever, a driving lever and a driven lever; the spring module comprises a driving lever slider, a spring guide seat and a spring; the lever module is connected to the base; the spring module and the lever module slide relative to each other along the driving lever and the driven lever; the two ends of the variable stiffness module are respectively connected to the base and the lever module; the variable stiffness module drives the spring guide seat to slide along the extension direction of the driven lever; the driving lever slider connected to the spring guide seat slides along the extension direction of the driving lever, thereby changing the resistance arm of the driven lever exerting force on the driving lever. The present invention has a simple and compact structure, good adjustability, can perform stepless adjustment of stiffness over a wide range, and has good scalability, and can be formed into various forms of clamping claws.

Description

Technical Field

[0001] The present invention relates to the technical field of robot end grippers, and in particular to a finger with variable stiffness and a gripper thereof. Background Art

[0002] With the continuous development of robotics technology, robots have played an increasingly important role in industrial production, gradually replacing many manual production and manufacturing processes. Mechanical grippers play a vital role in the field of robotics. They can be used as the end effector of robots to perform various gripping operations and are widely used in assembly, transportation, material sorting and other fields. However, traditional robotic grippers are generally rigid structures and cannot adapt to the shape of the object to be gripped, nor can they change the gripper's own stiffness according to the strength of the object to be gripped. Therefore, when gripping fragile objects, they are prone to damage.

[0003] For example, the variable stiffness mechanical gripper with patent publication number CN115533953A uses a leaf spring at the rear of the gripper as an elastic component and a ball screw as a driving device to adjust the position of the leaf spring under force, thereby adjusting the overall stiffness of the gripper. However, the fingers in the gripper are fixedly connected to the motor, and the movement of the fingers is restricted by the motor, making it impossible to passively adapt. Moreover, the direction of force applied by the finger structure to the leaf spring is unstable, making the leaf spring stiffness adjustment and control complex. Furthermore, the gripper is large in size and has a complex structure.

[0004] For example, patent publication number CN115781750A describes a fast-response flexible three-finger hand based on a bistable mechanism. This utilizes a bistable structure to enable the gripper to have two fixed states: grasping and opening. This simplifies the gripper's control strategy, and a series of connecting rods allow the gripper to adapt to the shape of an object. While this adapts to the object's shape, it lacks the ability to vary its stiffness, making it difficult to adjust the gripping stiffness, which can easily damage the object. Furthermore, the gripper is bulky and complex. Summary of the Invention

[0005] In order to overcome the defects and shortcomings of the existing technology, the present invention provides a finger and a clamping claw with variable stiffness. The present invention has a simple and compact structure, good variable stiffness effect, strong scalability, and can achieve infinite stiffness adjustment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a variable stiffness finger, comprising: a lever module, a spring module, a variable stiffness module and a base;

[0008] The lever module includes a finger lever, a connecting lever, a driving lever, and a driven lever;

[0009] The finger lever, connecting lever, driving lever and driven lever are in the same plane, and the plane is perpendicular to the bottom plane of the base. One end of the driving lever is provided with a first boss, and the first boss is movably connected to one end of the driven lever. The first boss is movably connected to the base. The other end of the driven lever is provided with a second boss, and the second boss is provided with a groove. The other end of the driving lever is embedded in the groove. One end of the finger lever is provided with a bent portion for clamping an object. The other end of the finger lever is movably connected to the second boss. One end of the connecting lever is movably connected to the middle part of the finger lever, and the other end of the connecting lever is movably connected to the base.

[0010] The spring module includes a driving lever slider, a spring guide seat and a spring;

[0011] The top of the driving lever slider is provided with a first groove, the first groove is matched with the driving lever, the driving lever slider slides along the extension direction of the driving lever, the bottom of the driving lever slider is connected to the spring guide seat, the spring is located in the spring guide seat, the outer side of the spring is provided with a sleeve, the sleeve and the spring guide seat are spaced apart, a third boss is provided on the side of the spring guide seat, the third boss is connected to the variable stiffness module, the bottom of the spring guide seat is provided with a second groove, the second groove is matched with the driven lever, and the spring guide seat slides along the extension direction of the driven lever;

[0012] The variable stiffness module is used to drive the spring guide seat to slide along the extension direction of the driven lever, and the driving lever slider connected to the spring guide seat slides along the extension direction of the driving lever.

[0013] As a preferred technical solution, the lever module is further provided with a lever motor, the lever motor is fixedly connected to the base, and the output shaft of the lever motor is connected to the first boss to drive the lever to rotate.

[0014] As a preferred technical solution, the variable stiffness module includes a variable stiffness motor, an active synchronous pulley, a driving gear, a driven synchronous pulley, a synchronous belt and a deep groove ball bearing;

[0015] The output shaft of the variable stiffness motor is connected to the driving gear, the driving gear is engaged with the driving synchronous pulley, the output shaft of the lever motor is connected to the driving synchronous pulley, the driven synchronous pulley is connected to the second boss, the synchronous belt is engaged with the driving synchronous pulley and the driven synchronous pulley, the driving synchronous pulley drives the driven synchronous pulley to rotate through the synchronous belt, and the third boss is fixedly connected to the synchronous belt.

[0016] As an optimal technical solution, the active synchronous pulley adopts a circular metal wheel with a trapezoidal groove on the surface, a gear boss on one side and a third groove on the other side. The gear boss is engaged with the driving gear, and the deep groove ball bearing is embedded in the third groove.

[0017] As a preferred technical solution, the driven synchronous pulley is a circular metal wheel with a trapezoidal groove on its surface, and is provided with a fourth groove, and the deep groove ball bearing is embedded in the fourth groove.

[0018] As a preferred technical solution, the synchronous belt adopts an elastic belt with a trapezoidal boss provided on the surface, and the trapezoidal boss is matched and engaged with the driving synchronous pulley and the driven synchronous pulley.

[0019] As a preferred technical solution, the lever module, the spring module and the variable stiffness module are provided in at least one group, and the base is provided in one group.

[0020] As a preferred technical solution, the first groove is a circular groove or an incomplete cylindrical groove, which matches and fits with the driving lever, and the second groove is a circular groove, which matches and fits with the driven lever.

[0021] The present invention also provides a multi-finger gripper with variable stiffness, which is provided with a plurality of groups of fingers with variable stiffness.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The present invention transmits the contact force between the end and the outside world through a lever assembly based on the lever principle, and realizes the infinite change of the length of the lever resistance arm through the mutual cooperation of the lever module, the spring module, and the variable stiffness module, thereby enabling the finger and its clamping claw to achieve the infinite variable stiffness effect.

[0024] (2) The present invention utilizes a synchronous belt drive to drive the slider to slide linearly along the optical axis of the lever, thereby changing the size of the resistance arm of the lever. It has good adjustability, continuous stiffness changes, and good scalability. It can form various forms of clamps, allowing the robotic arm to meet the needs of various production scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an axonometric diagram of the variable stiffness finger structure of the present invention;

[0026] Figure 2 A front view of a finger structure with variable stiffness according to the present invention;

[0027] Figure 3 This is an exploded schematic diagram of the variable stiffness module structure of the variable stiffness finger of the present invention;

[0028] Figure 4 Schematic diagram of the combined structure of the lever assembly and the spring assembly of the present invention;

[0029] Figure 5 It is a partial structural schematic diagram of the lever assembly of the present invention;

[0030] Figure 6 It is a structural schematic diagram of the spring assembly of the present invention;

[0031] Figure 7 Schematic diagram of the movement of the variable stiffness finger of the present invention;

[0032] Figure 8 Schematic diagram of the structure of the two-finger gripper with variable stiffness of the present invention;

[0033] Figure 9 Schematic diagram of the structure of the three-finger gripper with variable stiffness of the present invention;

[0034] Figure 10 Schematic diagram of the structure of the four-finger gripper with variable stiffness of the present invention.

[0035] Among them, 1-finger lever, 2-connecting lever, 3-driving lever, 4-driven lever, 5-spring module, 6-lever motor, 7-variable stiffness motor, 8-driving synchronous pulley, 9-driving gear, 10-driven synchronous pulley, 11-synchronous belt, 12-base, 13-deep groove ball bearing, 14-driving lever slider, 15-spring guide, 16-spring. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example

[0038] like Figure 1-Figure 7 As shown, this embodiment provides a variable stiffness finger, which is mainly used for adaptive gripping operations of objects during robot assembly and transportation. The finger includes a lever module, a spring module 5, a variable stiffness module and a base 12. The lever module contacts the spring module 5, and the lever module and the variable stiffness module are fixed on the base 12.

[0039] In this embodiment, at least one group of fingers is provided, and at least one group of lever modules, spring modules and variable stiffness modules are provided in the fingers. In this embodiment, the fingers are preferably provided in one group, and the lever modules, spring modules and variable stiffness modules are connected and contacted one by one. A group of bases 12 is provided, and the lever modules and variable stiffness modules are both installed on the bases 12.

[0040] In this embodiment, base 12 is positioned below the entire finger. Its bottom features a mounting base for securely connecting the finger to other external devices. Above it, a vertical mounting plate features multiple holes and a cylindrical shaft for mounting internal finger components. The connecting lever 2 and driving lever 3 in the lever module are hingedly connected to the cylindrical shaft on base 12, allowing for rotation around their axes. The lever motor 6 in the lever module and the variable stiffness motor 7 in the variable stiffness module are fixed to holes in base 12, allowing their output shafts to rotate freely.

[0041] Combine Figure 1-Figure 5As shown, the lever module includes a finger lever 1, a connecting lever 2, a driving lever 3, a driven lever 4, and a lever motor 6. The finger lever 1 and the connecting lever 2 are rectangular rod-shaped components with two hinges. The driving lever 3 has a hinge at one end and a cylindrical rod-shaped component with the other end being free. The driven lever 4 is a cylindrical rod-shaped component with hinges at both ends. The two hinges of the finger lever 1 are located at one end and the middle. The end without the hinge has a bent part, which can be used as a finger to clamp an object. The driving lever 3 has a boss structure at one end with a hinge, and the boss has two hinges. The center line of the two hinges is parallel to the center line of the cylindrical surface of the driving lever 3. The hinge at one end of the driven lever 4 is smaller, and the hinge at the other end has a boss with a certain groove. The surface roughness of the driving lever 3 and the driven lever 4 is relatively low. The hinge in the middle of finger lever 1 connects to the hinge at one end of connecting lever 2. The hinge at one end of finger lever 1 connects to the hinge with a boss on driven lever 4. The hinge at the other end of connecting lever 2 connects to the cylindrical shaft on base 12. The lower of the two hinges on the boss of driving lever 3 is fixedly connected to the output shaft of lever motor 6, while the upper hinge is connected to the smaller end of driven lever 4. The free end of driving lever 3 fits into a groove on the boss of driven lever 4, limiting its range of motion. The ends of spring module 5 are connected to driving lever 3 and driven lever 4, respectively, and spring module 5 can slide linearly relative to driving lever 3 and driven lever 4. Furthermore, finger lever 1, connecting lever 2, driving lever 3, and driven lever 4 are always located in the same plane. They are essentially parallel and of equal length. The centerline connecting the two hinges on the other side of finger lever 1 and connecting lever 2 and driving lever 3 remains parallel. Therefore, finger lever 1, connecting lever 2, driving lever 3, and driven lever 4 form a parallelogram linkage structure, which allows the side surfaces of the finger structure at the end of finger lever 1 to remain essentially vertical, facilitating gripping of objects. Lever motor 6 is fixed to base 12, with its output shaft fixedly connected to the hinge below driving lever 3, thereby driving driving lever 3 to rotate. When the lever motor 6 drives the driving lever 3 to rotate, the driving lever 3 drives the spring module 5 to pull or push the driven lever 4 to rotate, and finally drives the finger lever 1 to rotate. When the finger lever 1 contacts an external object, the driving lever 3 remains relatively stationary under the constraint of the lever motor 6. The finger lever 1 transmits the external force to the driven lever 4. The hinge has a boss at one end. The driven lever 4 rotates to the side opposite to the object under the external force. The distance between the driven lever 4 and the driving lever 3 is shortened, and the spring module 5 is pressed by the force of the driven lever 4 and then compressed. Therefore, for the driven lever 4, the external force applied by the finger lever 1 to the hinge of the driven lever 4 is the power, and the spring reaction force applied by the spring module 5 to the driven lever 4 is the resistance.

[0042] Combine Figure 7 As shown, the spring module of this embodiment includes a driving lever slider 14, a spring guide 15, and a spring 16. The driving lever slider 14 has an incomplete cylindrical groove above it, which allows it to engage and slide relative to the driving lever 3. The groove has a low surface roughness. The driving lever slider 14 is hinged to the top of the spring guide 15 below, allowing for relative rotation. The spring 16 is mounted within the spring guide 15, which limits its range of motion, restricting its telescopic movement to a linear direction. A sleeve (i.e., a continuous cylindrical surface in the figure) is sleeved around the outside of the spring 16, separated from the spring guide 15 by a gap. The spring guide 15 has a large boss below it, and an incomplete cylindrical groove below it with a low surface roughness. This groove can engage and slide relative to the driven lever 4. The side surfaces of the boss of the spring guide 15 extend outward, allowing for fixed connection to the synchronous belt 11 in the variable stiffness module. Since the driving lever 3 and the driven lever 4 are located in the same plane, the driving lever slider 14 can slide relatively along the driving lever 3, the spring guide seat 15 can slide relatively relative to the driven lever 4, and the driving lever slider 14 can rotate relative to the spring guide seat 15, and the spring 16 can expand and contract accordingly. Therefore, the spring module of this embodiment can also expand and contract linearly while sliding linearly. Since the spring 16 can only expand and contract linearly along the center line of the cylindrical surface of the spring guide seat 15 sleeve under the constraint of the spring guide seat 15, and the center line of the cylindrical surface of the spring guide seat 15 is always perpendicular to the center line of the cylindrical surface of the driven lever 4, it is ensured that the force applied by the spring module 5 as a whole to the driven lever 4 is always perpendicular to the driven lever 4.

[0043] Combine Figure 3As shown, the variable stiffness module of this embodiment includes a variable stiffness motor 7, an active synchronous pulley 8, a driving gear 9, a driven synchronous pulley 10, a synchronous belt 11 and a deep groove ball bearing 13. The active synchronous pulley 8 is a circular metal wheel with a trapezoidal groove on its surface, with a gear boss on one side and a groove on the other side, wherein the gear boss is engaged with the driving gear 9, and a deep groove ball bearing 13 is embedded in the groove. The active synchronous pulley 8 is installed on the output shaft of the lever motor 6. Under the action of the deep groove ball bearing 13, it can be driven by the lever motor 6 instead of being driven. The driving gear 9 is fixed on the output shaft of the variable stiffness motor 7. The variable stiffness motor 7 can drive the driving gear 9 to rotate, and then drive the active synchronous pulley 8 engaged with the driving gear 9 to rotate. The driven synchronous pulley 10 is a metal wheel similar to the driving synchronous pulley 8. It does not have a gear boss but has a groove. The driven synchronous pulley 10 is fixed to a hinge on one end of the driven lever 4 with a boss and can rotate freely under the action of a deep groove ball bearing 13. The synchronous belt 11 is an elastic belt with a trapezoidal boss on its surface. The synchronous belt 11 is interlocked with the driving synchronous pulley 8 and the driven synchronous pulley 10 and can be driven to rotate by the driving synchronous pulley 8. The driving synchronous pulley 8 is relatively fixed in position under the constraint of the lever motor 6. The driven synchronous pulley 10 will move with the movement of the driven lever 4, but the relative distance between the driving synchronous pulley 8 and the driven synchronous pulley 10 remains basically unchanged. The motion trajectory plane of the synchronous belt 11 remains basically parallel to the centerline of the cylindrical surface of the driven lever 4. Therefore, the synchronous belt 11 can drive the spring guide seat 15 fixed to it to slide linearly along the driven lever 4, and the spring guide seat 15 then drives the driving lever slider 14 to slide linearly along the driving lever 3.

[0044] In this embodiment, when an adaptive two-finger gripper with variable stiffness is in operation, the finger lever 1 will come into contact with an external object and be subjected to a certain force. Since the driving lever 3 is relatively fixed in position under the constraint of the lever motor 6, the finger lever 1 will drive the connecting lever 2 and the driven lever 4 to rotate in the opening direction, and the finger lever 1 will apply a certain force to the hinge on the side of the driven lever 4 with the boss. Since the driving lever 3 is embedded in the groove of the boss at one end of the driven lever 4, the driven lever 4 can approach the driving lever 3 and transmit the force to the spring 16 through the spring guide seat 15 connected to the driven lever 4, causing the spring 16 to expand and contract to a certain extent. After that, the force is transmitted to the driving lever 3 through the driving lever slider 14, and then to the lever motor 6, and finally to the base 12. The main principle of stiffness adjustment is to adjust the force transmitted to the spring guide seat 15 by the driven lever 4. The driven lever 4 acts as a lever, wherein the external force transmitted from the finger lever 1 to the driven lever 4 can be regarded as the power in the lever, and the reaction force transmitted from the spring 16 to the spring guide seat 15 and then to the driven lever 4 can be regarded as the resistance in the lever. The hinge below the driven lever 4 fixed to the boss hinge of the driving lever 3 can be regarded as the fulcrum of the lever. The power arm does not change and therefore remains unchanged. The stiffness adjustment in the present invention is to adjust the length of the resistance arm in the lever. During stepless adjustment of stiffness, the variable stiffness motor 7 rotates the drive gear 9, which in turn rotates the meshing drive synchronous pulley 8, which in turn rotates the synchronous belt 11. This causes the spring guide 15, which is fixed to the synchronous belt 11, to slide linearly along the driven lever 4. This also causes the drive lever slider 14, connected to the spring guide 15, to slide linearly along the drive lever 3. As a result, the position of the spring guide 15 on the driven lever 4 changes, and the length of the resistance arm transmitted by the spring guide 15 to the driven lever 4 changes. Consequently, the force transmitted by the spring guide 15 to the driven lever 4 also changes. Consequently, the magnitude of the force between the spring 16 and the spring guide 15 changes, resulting in different compression levels and, consequently, different stiffness characteristics for the entire finger. Because the distance that the spring guide 15 moves along the driven lever 4 in the variable stiffness module is steplessly variable, the stiffness adjustment of the two-finger gripper is stepless.

[0045] The variable stiffness fingers of this embodiment can be arranged in multiple groups to form a multi-finger gripper, such as Figures 8-10 As shown, two-finger, three-finger, and four-finger grippers are formed.

[0046] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A finger with variable stiffness, characterized in that: include: Lever module, spring module, variable stiffness module and base; The lever module includes a finger lever, a connecting lever, a driving lever, and a driven lever; The finger lever, connecting lever, driving lever and driven lever are in the same plane, and the plane is perpendicular to the bottom plane of the base. One end of the driving lever is provided with a first boss, and the first boss is movably connected to one end of the driven lever. The first boss is movably connected to the base. The other end of the driven lever is provided with a second boss, and the second boss is provided with a groove. The other end of the driving lever is embedded in the groove. One end of the finger lever is provided with a bent portion for clamping an object. The other end of the finger lever is movably connected to the second boss. One end of the connecting lever is movably connected to the middle part of the finger lever, and the other end of the connecting lever is movably connected to the base. The spring module includes a driving lever slider, a spring guide seat and a spring; The top of the driving lever slider is provided with a first groove, the first groove is matched with the driving lever, the driving lever slider slides along the extension direction of the driving lever, the bottom of the driving lever slider is connected to the spring guide seat, the spring is located in the spring guide seat, the outer side of the spring is provided with a sleeve, the sleeve and the spring guide seat are spaced apart, a third boss is provided on the side of the spring guide seat, the third boss is connected to the variable stiffness module, the bottom of the spring guide seat is provided with a second groove, the second groove is matched with the driven lever, and the spring guide seat slides along the extension direction of the driven lever; The variable stiffness module is used to drive the spring guide seat to slide along the extension direction of the driven lever, and the driving lever slider connected to the spring guide seat slides along the extension direction of the driving lever.

2. The variable stiffness finger according to claim 1, characterized in that: The lever module is further provided with a lever motor, which is fixedly connected to the base. The output shaft of the lever motor is connected to the first boss to drive the lever to rotate.

3. The variable stiffness finger according to claim 2, characterized in that: The variable stiffness module includes a variable stiffness motor, an active synchronous pulley, a driving gear, a driven synchronous pulley, a synchronous belt and a deep groove ball bearing; The output shaft of the variable stiffness motor is connected to the driving gear, the driving gear is engaged with the driving synchronous pulley, the output shaft of the lever motor is connected to the driving synchronous pulley, the driven synchronous pulley is connected to the second boss, the synchronous belt is engaged with the driving synchronous pulley and the driven synchronous pulley, the driving synchronous pulley drives the driven synchronous pulley to rotate through the synchronous belt, and the third boss is fixedly connected to the synchronous belt.

4. The variable stiffness finger according to claim 3, characterized in that: The active synchronous pulley is a circular metal wheel with a trapezoidal groove on its surface, a gear boss on one side and a third groove on the other side. The gear boss is engaged with the driving gear, and the deep groove ball bearing is embedded in the third groove.

5. The variable stiffness finger according to claim 3, characterized in that: The driven synchronous pulley is a circular metal wheel with a trapezoidal groove on its surface, and is provided with a fourth groove, and the deep groove ball bearing is embedded in the fourth groove.

6. The variable stiffness finger according to claim 3, characterized in that: The synchronous belt adopts an elastic belt with a trapezoidal boss provided on the surface, and the trapezoidal boss is matched and embedded with the driving synchronous pulley and the driven synchronous pulley.

7. The variable stiffness finger according to claim 1, characterized in that The lever module, the spring module and the variable stiffness module are provided in at least one group, and the base is provided in one group.

8. The variable stiffness finger according to claim 1, characterized in that The first groove is a circular groove or an incomplete cylindrical groove, which is matched with the driving lever, and the second groove is a circular groove, which is matched with the driven lever.

9. A multi-finger gripper with variable stiffness, characterized in that: A plurality of groups of fingers with variable stiffness as described in any one of claims 1 to 8 are provided.

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