Parallel clamping-adaptive under-actuated robot hand with variable equivalent stiffness

Abstract

The invention relates to the field of robot hands, in particular to an equivalent stiffness variable parallel clamping-adaptive under-actuated robot hand which comprises two connecting rod-spring mechanisms, the number of the connecting rod-spring mechanisms is two, and two triangular connecting rods are arranged on the sides away from each other; the device further comprises a palm and a sliding block longitudinally connected to the palm in a sliding mode, the lower portions of the two first connecting rods are both rotationally connected to the sliding block, the two public rotating pairs A are installed on the palm, and the lower portions of the two springs are both fixed to the palm. And the two bent connecting rods are respectively provided with a finger. In the actual operation process of a traditional mechanical clamping hand, the core technical pain is that energy loss is too large, however, by means of the structural design, when the clamping hand executes the grabbing action, energy needed by self-adaptive inward bending of fingers can be reduced through driving by reducing a force arm acted by a spring, and therefore the mechanical clamping hand is driven to conduct the grabbing action. And optimization of energy consumption is realized from the source of action execution.

Description

Technical Field

[0001] This application relates to the field of robotic hands, and more particularly to a flat clamp-adaptive underactuated robotic hand with equivalent variable stiffness. Background Technology

[0002] A flat gripper robot hand is a gripping component that can be adapted to the actuator of a robotic arm or automated equipment. It is a specialized device that can clamp, lift, or release workpieces according to a preset stroke and gripping force. By matching different structural forms and drive methods, it can meet the gripping needs of various workpieces, combining the advantages of compact structure, fast response, and stable gripping in both construction and performance. Flat gripper robot hands are the core actuators of industrial robotic arms and are widely used in machining, automotive manufacturing, electronic assembly, warehousing and sorting, and food packaging.

[0003] Flat gripper robots have broad application prospects in industrial manufacturing, medical assistance, logistics sorting, and precision electronics. Domestic and international researchers have conducted in-depth research on the core theories of flat gripper robots, including their rigid-flexible hybrid configurations, data-driven control, and adaptive gripping strategies, and have completed related application development in practical scenarios such as flexible gripping and non-destructive manipulation. Currently, several companies have launched mature flat gripper robot products on the market. Among them, the EGU series of electric flat gripper robots from the German company SCHUNK has achieved large-scale application. This product boasts a repeatability accuracy of ±0.02mm, supports precise force control adjustment, and is one of the mainstream choices for automated operations in various application fields. Although existing products continue to improve in adaptability and accuracy, they still suffer from insufficient gripping stability and control precision, high energy consumption, and relatively limited gripping scenarios. Summary of the Invention

[0004] The purpose of this application is to provide an equivalent stiffness variable flat clamp-adaptive underactuated robotic hand that can reduce the energy required for adaptive inward bending of the fingers.

[0005] A linkage-spring mechanism includes a first link, a second link, a third link, a fourth link, a triangular link, and a fifth link. The upper part of the first link, the left end of the second link, and the lower part of the third link form a common revolute joint B. The other end of the second link, the lower part of the fourth link, and one end of the upper part of the triangular link form a common revolute joint A. The other end of the upper part of the triangular link and the lower part of the fifth link form a revolute joint C. The position of revolute joint A is higher than that of revolute joint C.

[0006] It also includes a curved connecting rod, the upper parts of the third connecting rod, the upper parts of the fourth connecting rod, and the upper parts of the fifth connecting rod are rotatably connected to the curved connecting rod from left to right, and the fourth connecting rod, the triangular connecting rod, the fifth connecting rod and the curved connecting rod form a parallelogram mechanism;

[0007] The triangular connecting rod is provided with a first sliding groove, in which a limiting shaft is slidably connected. The first sliding groove is inclined, so that the limiting shaft gradually rises near the rotating joint B and gradually decreases near the rotating joint C. One end of a tension spring is fixed on the limiting shaft. The curved connecting rod is used to install a finger. The upper parts of the third connecting rod, the upper parts of the fourth connecting rod, and the upper parts of the fifth connecting rod form a pin-shaft rotating joint with the curved connecting rod. All three pins are fixed on the finger.

[0008] The rotational connections of the third, fourth, and fifth links with the crank link form revolute joints G, F, and H from left to right, respectively. Revolute joint G is positioned higher than revolute joint F, and revolute joint B is positioned lower than revolute joint C.

[0009] Rotating joints A, C, F and H are located at the four ends of the parallelogram, and the fourth link is parallel to the fifth link.

[0010] All of the rotating joints mentioned are pin-shaft rotating joints.

[0011] A flat clamp-adaptive underactuated robot hand with equivalent variable stiffness includes the above-mentioned link-spring mechanism. There are two link-spring mechanisms arranged in a mirror symmetric manner, with the two triangular links arranged on the side away from each other.

[0012] It also includes a palm and a slider that is longitudinally slidably connected to the palm. The lower parts of the two first links are rotatably connected to the slider. The two common rotating joints A are installed on the palm. The lower parts of the two springs are fixed on the palm.

[0013] Each of the two connecting rods has a finger installed on it.

[0014] A hole is provided in the palm, and a first pin is fixed in the palm through the hole. The first pin passes through the triangular link, the fourth link and the second link in sequence from back to front, so that the triangular link, the fourth link and the second link are rotated around the first pin as a common axis.

[0015] The bottom of the slider is provided with a groove, which is connected to the first sliding groove. A flange that fits in the groove is fixed on the limiting shaft; or, the first sliding groove has a flange, and the limiting shaft is provided with a groove that fits in with the flange; or, the front and rear ends of the limiting shaft have flanges to slide and rub against the front and rear ends of the triangular connecting rod respectively.

[0016] E is located to the left of the first slide groove, causing the position where the triangular connecting rod connects to the spring to move to the left during subsequent movements after the first slide groove is horizontal, thus shortening the spring length. The palm has a longitudinally extending second slide groove, and the slider is connected to the palm via a key within the second slide groove.

[0017] Before contacting an object, the spring acts as a tension spring, keeping it in a stretched state, so that the connecting rod can only move in translational motion.

[0018] The slider moves longitudinally by being driven by a power source.

[0019] The beneficial effects of the equivalent variable stiffness flat clamp-adaptive underactuated robot hand proposed in this application are:

[0020] The linkage-spring mechanism leverages the rigid transmission characteristics of the linkage and the elastic buffering characteristics of the spring to achieve automatic and uniform force distribution. This allows the robotic hand to adapt to the shape of the object during grasping, conforming to surfaces of different shapes without additional sensor control. Furthermore, its geometrical motion constraints effectively limit unexpected displacement and swaying during grasping, improving stability and precision. This reduces surface scratches and damage caused by uneven force distribution and gripping posture deviations, and minimizes grasping failures due to insufficient fit and inaccurate positioning, significantly enhancing the reliability and yield of grasping operations.

[0021] A major technical challenge of traditional mechanical grippers during actual operation is excessive energy loss. However, thanks to the structural design of this invention, when the gripper performs a grasping action, the force arm driven by the reduced spring force is decreased, thereby reducing the energy required for the fingers to adaptively bend inward, optimizing energy consumption from the source of the action. When the gripper completes the task and performs the release action, the spring automatically returns to its original position. The spring in the mechanism utilizes its own elastic properties to achieve automatic reset. During this process, some of the energy that would have been lost as heat or friction in traditional designs can be converted and stored as the elastic potential energy of the spring. Through this design, this invention significantly reduces the overall energy loss of the mechanical gripper from two dimensions, significantly improving the energy utilization efficiency and operational economy of the equipment.

[0022] This flat-gripping robotic arm, leveraging the adaptive linkage characteristics of its invented linkage-spring mechanism, can autonomously adapt to workpieces of different shapes and sizes through its own motion coordination and elastic adjustment. During the gripping of different types of workpieces, it eliminates the need for frequent adjustments to control parameters and replacement of the robotic arm, significantly simplifying pre-operation preparation and effectively expanding the applicable gripping scenarios. Furthermore, addressing the issue of significant dimensional deviations in workpieces within the same batch during actual production, this robotic arm can effectively prevent unstable gripping or even gripping failure, ensuring the continuity and stability of batch gripping operations. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1This is a schematic diagram of the structure of an equivalent stiffness-variable flat clamp-adaptive underactuated robot hand according to this application;

[0025] Figure 2 This is a schematic diagram of the linkage-spring mechanism of this application;

[0026] Figure 3 This is a schematic diagram of the triangular linkage structure of this application;

[0027] Figure 4 This is a schematic diagram of the slider structure of this application;

[0028] Figure 5 This is a schematic diagram of the structure of the finger in this application;

[0029] Figure 6 This is a simplified diagram of the transmission system mechanism of this application.

[0030] Figure descriptions: 1. First link; 2. Second link; 3. Third link; 4. Fourth link; 5. Triangular link; 51. First slide groove; 52. Limiting shaft; 53. Spring; 6. Fifth link; 7. Curved link; 8. Hand; 81. Second slide groove; 9. Slider; 10. Finger. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "rotatably connected" to another element, it can be directly on the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used in this specification are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0033] like Figure 1 , 2As shown in Figure 6, an equivalent stiffness variable-stiffness flat-clamping adaptive underactuated robot hand includes two link-spring mechanisms arranged symmetrically on the left and right sides. For ease of explanation, the link-spring mechanism on the right side is used as an example. It includes a first link 1, a second link 2, and a third link 3. The upper part of the first link 1, the left end of the second link 2, and the lower part of the third link 3 are rotatably connected by the same pin, forming a common revolute joint, which is called B. The lower part of the fourth link 4 is rotatably connected to the left end of the upper part of the triangular link 5, forming a revolute joint, which is called A. The right end of the upper part of the triangular link 5 is rotatably connected to the fifth link 6, forming a revolute joint, which is called C. In terms of height, A is the highest, C is lower than A, and B is lower than C.

[0034] To further explain, the linkage-spring mechanism also includes a curved connecting rod 7. The upper parts of the third connecting rod 3, the fourth connecting rod 4, and the fifth connecting rod 6 are rotatably connected to the curved connecting rod 7 from left to right. The revolute joint formed by the third connecting rod 3 and the curved connecting rod 7 is G, the revolute joint formed by the fourth connecting rod 4 and the curved connecting rod 7 is F, and the revolute joint formed by the fifth connecting rod 6 and the curved connecting rod 7 is H, so that the relative positions of the upper parts of the third connecting rod 3, the fourth connecting rod 4, and the fifth connecting rod 6 are fixed.

[0035] To further explain, the triangular connecting rod 5 is provided with a first sliding groove 51, within which a limiting shaft 52 is slidably connected. The limiting shaft 52, fitting within the first sliding groove 51, aims to achieve only linear movement. The first sliding groove 51 is inclined, causing the limiting shaft 52 to gradually rise as it approaches its highest linear movement, and remaining below its second highest position even when it reaches the highest point of the first sliding groove 51. K and D represent the left and right ends of the limiting shaft 52 within the first sliding groove 51, respectively. The upper part of a spring 53 is fixed to the end of the limiting shaft 52.

[0036] To further explain, points G, F, and H of the connecting rod 7 are connected to the finger 10 via pins, thereby ensuring that the movement of the finger 10 is consistent with the movement of the connecting rod 7, making G, F, H, and I a whole, with I moving together with G, F, and H.

[0037] The fourth link (4), the triangular link (5), the fifth link (6), and the curved link (7) can form a parallelogram. A, C, F, and H are located at the four ends of the parallelogram, and G is higher than F.

[0038] Regarding the limiting scheme for the linear movement of the limiting shaft 52 within the first slide groove 51, a flange extending along the long side of the first slide groove 51 can be fixed within the first slide groove 51, and a groove that mates with the flange is provided on the limiting shaft 52. Alternatively, the front and rear ends of the limiting shaft 52 have flanges to slide and rub against the front and rear ends of the triangular connecting rod 5, respectively.

[0039] To further explain, for ease of description, the side of the two linkage-spring mechanisms that is closer to each other is the inner side, while the two first linkages 1 are located on the inner side and close to each other, and the two springs 53 are located on the outer side.

[0040] The equivalent stiffness variable-stiffness flat-clamp adaptive underactuated robot hand also includes a palm 8 and a slider 9 longitudinally slidably connected to the palm 8, with the slider 9 positioned at J. A cavity is formed at the top of the palm 8 to provide sufficient space for the linkage movement. The lower parts of both first linkages 1 are rotatably connected to the palm 8. The highest point of the triangular linkage 5 is also rotatably connected to the palm 8, allowing the triangular linkage 5 to rotate around its highest axis. Two pillars are also fixed to the palm 8 within the cavity, and the lower parts of two springs 11 are respectively fixed to the two pillars. The connection point between the right-side spring 11 and the pillar is E.

[0041] In this system, the connecting rods that are rotatably linked together, i.e., the connecting rods on the same axis of rotation, are connected by pins. Connecting rods and the hand 8 can also share a single pin. For example, in the connecting rod-spring mechanism on the right side: the hand 8 has a hole through which the first pin passes. Simultaneously, the first pin passes from back to front through the highest point of the triangular connecting rod 5, the lower part of the fourth connecting rod 4, and the right part of the second connecting rod 2. The first pin is then fixed to the hand 8, thus achieving a rotatable connection between the highest point of the triangular connecting rod 5 and the hand 8, a rotatable connection between the lower part of the fourth connecting rod 4 and the highest point of the fourth connecting rod 4, and a rotatable connection between the right part of the second connecting rod 2 and the lower part of the fourth connecting rod 4. Similarly, a second pin passes through the lower part of the third connecting rod 3, the upper part of the first connecting rod 1, and the left part of the second connecting rod 2, and uses the second pin to limit the relative axial movement of the three components. For example, a flat surface can be milled on the pin, and a limiting block can be welded to or secured to the side wall with screws. The second lowest part of the triangular link 5 and the bottom of the fifth link 6 are inserted into the third pin, and the third pin is used to axially limit the two.

[0042] Among them, the palm 8 is provided with a longitudinal second slide groove 81, and the slider 9 is formed with a key structure. Utilizing the keyway mating principle, it has only longitudinal degree of freedom in the second slide groove 81.

[0043] In this mechanism, a link-spring mechanism is matched with a finger 10. The finger 10 can be fixed to pins that pass through the top of the third link 3, the fourth link 4, and the fifth link 6 respectively. These three pins are fixed to the curved link 7, and the tops of the third link 3, the fourth link 4, and the fifth link 6 are respectively inserted into these three pins. These three pins provide axial restraint for the third link 3, the fourth link 4, and the fifth link 6. Alternatively, the finger 10 can be fixed to the curved link 7, with the inner end faces of the two fingers 10 parallel.

[0044] A power source such as a linear drive mechanism can be used to drive the slider 9 to move longitudinally. Moving the slider 9 downwards allows the two fingers 10 to come closer together and bend downwards to grasp. The parallelogram structure ensures that the fingers 10 remain vertical before contacting the object. Before contacting the object, the spring 53 acts as a tension spring, keeping it in a stretched state and pulling the triangular connecting rod 5 so that it cannot move. This ensures that one side of the parallelogram, namely the curved connecting rod 7, can only translate and cannot rotate, keeping the inner end face of the finger 10 vertical.

[0045] For ease of description, let's take an example of the operating state of the linkage-spring mechanism on the right:

[0046] After slider 9 moves downward along the second slide groove 81, slider 9 drives the first connecting rod 1 to start moving. The end of the second connecting rod 2 connected to the first connecting rod 1 rotates counterclockwise around the fixed outer end of the second connecting rod 2, which drives the third connecting rod 3 to also start moving counterclockwise. The curved connecting rod 7 moves in translation and drives the fourth connecting rod 4 to rotate counterclockwise through the curved connecting rod 7. The triangular connecting rod 5 does not rotate under the action of the spring 53, thereby realizing the grasping of the object.

[0047] After contact with the object, the fourth link 4 stops moving, so one side of the parallelogram stops moving, and the triangular link 5 begins to move counterclockwise. When the slider 9 continues to move downward, the triangular link 5 pulls the spring 53 to begin stretching and moving counterclockwise at the same time. The corresponding curved link 7 also begins to move counterclockwise, causing the finger 10 to no longer remain vertical and begin to bend counterclockwise towards the object. When the limiting shaft 52 in the third link 3 moves in the direction of movement, or when the first slide 51 becomes horizontal, the limiting shaft 52 begins to move inward, entering a pre-set node, such as the maximum inner stroke. Nodes can also be added as needed to lock the limiting shaft 52. The length of the spring 53 decreases, and the lever arm of the spring 53 decreases, reducing the force required for the finger 10 to bend inward and reducing the energy lost when releasing, thus achieving adaptive grasping of the object.

[0048] It should be noted that while preferred embodiments of this application are provided in the specification and accompanying drawings, this application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this application; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this application. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A linkage-spring mechanism, characterized in that, It includes a first link, a second link, a third link, a fourth link, a triangular link, and a fifth link. The upper part of the first link, the left end of the second link, and the lower part of the third link form a common revolute joint B. The other end of the second link, the lower part of the fourth link, and one end of the upper part of the triangular link form a common revolute joint A. The other end of the upper part of the triangular link and the lower part of the fifth link form a revolute joint C. The position of revolute joint A is higher than that of revolute joint C. It also includes a curved connecting rod, the upper parts of the third connecting rod, the upper parts of the fourth connecting rod, and the upper parts of the fifth connecting rod are rotatably connected to the curved connecting rod from left to right, and the fourth connecting rod, the triangular connecting rod, the fifth connecting rod and the curved connecting rod form a parallelogram mechanism; The triangular connecting rod is provided with a first sliding groove, and a limiting shaft is slidably connected in the first sliding groove. The first sliding groove is inclined so that the limiting shaft gradually rises as it approaches the rotating joint B and gradually decreases as it approaches the rotating joint C. One end of the limiting shaft is fixed with a tension spring.

2. The linkage-spring mechanism according to claim 1, characterized in that, The rotational connections of the third, fourth, and fifth links with the crank link form revolute joints G, F, and H from left to right, respectively. Revolute joint G is positioned higher than revolute joint F, and revolute joint B is positioned lower than revolute joint C.

3. The linkage-spring mechanism according to claim 2, characterized in that, Rotating joints A, C, F and H are located at the four ends of the parallelogram, and the fourth link is parallel to the fifth link.

4. The linkage-spring mechanism according to claim 1, characterized in that, All of the rotating joints mentioned are pin-shaft rotating joints.

5. A flat-clamping adaptive underactuated robot hand with equivalent variable stiffness, characterized in that, Includes the linkage-spring mechanism according to any one of claims 1 to 4, wherein two linkage-spring mechanisms are arranged in a mirror-symmetrical manner, and the two triangular linkages are arranged on the side away from each other; It also includes a palm and a slider that is longitudinally slidably connected to the palm. The lower parts of the two first links are rotatably connected to the slider. The two common rotating joints A are installed on the palm. The lower parts of the two springs are fixed on the palm. A finger is installed on each of the two connecting rods.

6. The equivalent stiffness variable flat clamp-adaptive underactuated robot hand according to claim 5, characterized in that, A hole is provided in the palm, and a first pin is fixed in the palm through the hole. The first pin passes through the triangular link, the fourth link and the second link in sequence from back to front, so that the triangular link, the fourth link and the second link are rotated around the first pin as a common axis.

7. The equivalent stiffness variable flat clamp-adaptive underactuated robot hand according to claim 5, characterized in that, The bottom of the slider is provided with a groove, which is connected to the first sliding groove. A flange that fits in the groove is fixed on the limiting shaft; or, the first sliding groove has a flange, and the limiting shaft is provided with a groove that fits in with the flange; or, the front and rear ends of the limiting shaft have flanges to slide and rub against the front and rear ends of the triangular connecting rod respectively. The palm has a second vertically extending groove, and the slider is connected to the palm in the second groove.

8. The equivalent stiffness variable flat clamp-adaptive underactuated robot hand according to claim 5, characterized in that, Before contacting an object, the spring acts as a tension spring, keeping it in a stretched state, so that the connecting rod can only move in translational motion.

9. The equivalent stiffness variable flat clamp-adaptive underactuated robot hand according to claim 5, characterized in that, E is located to the left of the first slide, causing the position where the triangular link connects to the spring to move to the left during the subsequent movement after the first slide is horizontal, and the length of the spring to shorten.

10. The equivalent stiffness variable flat clamp-adaptive underactuated robot hand according to claim 5, characterized in that, The slider moves longitudinally by being driven by a power source.

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