Flexible clamping mechanical arm based on tensegrity structure

Abstract

The application discloses a kind of flexible clamping mechanical arm based on tensegrity structure, belong to mechanical arm technical field.The mechanical arm includes top drive module, tensegrity trunk and end self-adapting clamping mechanism;The tensegrity trunk is stacked by multiple layers Snelson tetrahedron tensegrity unit, each layer unit includes integrated rigid element, transverse flexible body and axial flexible body, and rigid-flexible coupling structure is formed by internal self-stress balance;The top drive module is provided with four trunk drive units and an independent gripper drive unit, and the bending and torsional deformation of the trunk and the opening and closing of the end clamping mechanism are controlled by trunk drive rope and gripper drive rope respectively.The application utilizes the mechanical reorientation characteristics of tensegrity structure, realizes the continuum large deformation and bending and torsional composite motion of mechanical arm, has excellent compliance and passive adaptability, solves the problem of large cumulative error and high control precision requirement of traditional rope-driven flexible mechanical arm.

Description

Technical Field

[0001] This invention relates to the field of robotic arm technology, and in particular to a flexible clamping robotic arm based on a tensioned integral structure. Background Technology

[0002] In recent years, bionic robotic arms have been widely used in numerous fields such as nature exploration, national defense and aviation, logistics and transportation, maintenance, entertainment and leisure, and rehabilitation and nursing. The research results of robotic arms have provided significant convenience to many aspects of life and industry. For example, in industrial production, robotic arms are often used to replace human hands in repetitive tasks, greatly saving labor costs and freeing up human hands and time. However, in the field of agricultural and rural modernization in my country, the level of mechanization is still not high. While agricultural mechanization in my country has covered the main stages of plowing, planting, and harvesting, the mechanization rate of fruit and vegetable harvesting is less than 40%. As a major agricultural country, my country has a vast territory and a very large population. From a certain perspective, intelligent fruit and vegetable harvesting equipment is of great significance to my country and is an important manifestation of my country's comprehensive national strength. The application of flexible intelligent fruit and vegetable harvesting equipment in the field of agricultural and rural modernization in my country is a key development area for the country. In the current context of accelerating modernization, this invention has a potentially vast market and immeasurable economic value.

[0003] Meanwhile, existing rope-driven flexible robotic arms capable of combined bending and torsional deformation, such as patent CN121670611A, still have certain limitations in practical applications. First, this solution highly relies on the pre-compression and deformation characteristics of the chiral elastic component. Once the parameters such as the diameter and tilt angle of the elastic rod are formed, they are difficult to adjust dynamically, making it difficult for a single device to adapt to the stiffness requirements of multiple scenarios and lacking passive adaptability in the face of sudden external force interference. In addition, although its bending and torsional drive achieves decoupling, the structure in which the middle section of the rope passes through the center of the substrate and the outer peripheral ropes are distributed at the edge is prone to cumulative errors after multiple sections are connected in series. This places high demands on the closed-loop control accuracy of the drive motor, increasing the debugging difficulty and cost of the control system. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a flexible clamping manipulator based on a tensioned integral structure. By combining the tensioned integral topology with the end-effector rope-driven clamping mechanism, and utilizing a super-redundant tensioned integral structure composed of multiple sets of cross-arranged integrated rigid elements and continuous transverse and axial flexible bodies, the manipulator can achieve continuous large deformation and bending-torsional composite motion in three-dimensional space. This invention achieves extreme compliance, high fault tolerance, and lightweight while also possessing excellent structural stiffness and dynamic response capabilities. It solves the problems of large cumulative error, high control precision requirements, and lack of passive adaptability under sudden external forces caused by multiple connected segments in traditional rope-driven flexible manipulators.

[0005] This invention achieves full-scale, multi-degree-of-freedom continuous bending of a robotic arm through an innovative stacked, layered tensioned modular design. It decouples the self-stress equilibrium state formed by the compression members and tension cable nets within each module from the release and retraction of the external trunk-driven ropes, enabling the robotic arm to perform obstacle avoidance and exploration similar to biological tentacles in complex, unstructured environments. Furthermore, by utilizing the unique mechanical redirection characteristics of axial compression and radial tension inherent in the tensioned modular structure, it can generate synergistic deformation through the structural transmission of the main trunk when the end effector performs torsional operations. This allows for precise bending and torsional combination control of the robotic arm in confined spaces, effectively overcoming the frictional accumulation and hysteresis effects generated by traditional discrete rope drives in serial structures.

[0006] It should be noted that the naming of related components in this invention is for descriptive purposes only and is used to illustrate the technical solution. It should not be construed as a limitation of this invention.

[0007] This invention proposes a flexible gripping robotic arm based on a tensioned integral structure, mainly comprising a top drive module, a tensioned integral torso, and an end-effector adaptive gripping mechanism. The end-effector adaptive gripping mechanism is coaxially mounted to the bottom of the tensioned integral torso, and the two are rigidly connected for secure engagement. This establishes the relative position of the gripper and the torso, preventing torsional instability of the end effector due to force eccentricity during multi-dimensional bending and gripping operations.

[0008] The top drive module mainly includes an outer shell frame, a top mounting plate, four torso drive units, one gripper drive unit, four torso active drums, one gripper active drum, and a central guide pulley. The outer shell frame has a rectangular ring structure, providing an installation reference for the internal components. The four torso drive units are arranged in a rectangular array and fixed to the upper surface of the top mounting plate. Four torso active drums are keyed to their output shafts for directly winding and unwinding high-strength torso drive ropes. The individual gripper drive unit is located outside the rectangular array, and a gripper active drum is keyed to its output shaft. The top mounting plate is bolted and fixed to the top of the outer shell frame. The central guide pulley is fixed to the geometric center of the top mounting plate via a bearing seat, used to change the direction of travel of the gripper drive rope, guiding it to the gripper active drum. The torso drive ropes output from the four torso active drums directly and vertically downwards pass through the interlayer nodes for tensioning the entire torso. Specifically, the four torso drive units achieve differential operation through program control, respectively retracting and extending the torso drive ropes. The connection point between the ropes and the tensioning unit generates tension, thereby breaking the original prestress balance of the torso and forcing the torso to produce a predetermined bending or torsional deformation. The gripper drive unit independently controls the forward and reverse rotation of the gripper active drum. Through the reversal of the central guide pulley, the gripper drive rope is used to achieve precise opening and closing of the end gripping mechanism.

[0009] The tensioned monolithic frame is constructed by stacking eight layers of Snelson tetrahedral tensioned monolithic units along the axial direction. Each unit contains only two types of components: integrated rigid elements and flexible bodies, completely eliminating the traditional central load-bearing column and limiting tie rod. Specifically, the integrated rigid element is a 3D-printed X-shaped structure, consisting of two horizontal rigid connecting rods and two inclined rigid connecting rods integrated together, with connecting lugs at the ends of the four connecting rods. It is important to note that the integrated rigid elements in each layer do not contact each other, but are only topologically connected in space through the flexible bodies, thereby forming a stable self-stress equilibrium system under preload.

[0010] The flexible bodies are divided into two categories: transverse flexible bodies and axial flexible bodies. There are four transverse flexible bodies, used to connect the bottom connecting lugs of the upper-layer integrated rigid element to the top connecting lugs of the current-layer integrated rigid element. This cross-layer oblique connection provides transverse prestress to each layer of integrated rigid element and restricts relative displacement between layers. There are also four axial flexible bodies, arranged around the outer perimeter of the trunk, connecting the bottom connecting lugs of the upper-layer integrated rigid element to the bottom connecting lugs of the current-layer integrated rigid element, and always remaining parallel to the central axis. These maintain the axial prestress and structural stiffness of the entire tensioned trunk. Through this tensioned overall configuration, the eight layers of integrated rigid elements simultaneously bear axial and transverse pressure. All flexible bodies are always in a bidirectional tensioned state, relying entirely on the structure's own self-stress balance characteristics to achieve structural continuity and overall load-bearing capacity of the robotic arm during significant bending.

[0011] The end-effector adaptive clamping mechanism includes a gripper base, four gripper links, and a gripper transmission assembly. The gripper base is cylindrical, with its upper end connected to the lowest integrated rigid element of the tensioned monolithic body. The gripper transmission assembly includes a central rod, a cross-shaped connecting block, and four active connecting rods. The central rod is supported inside the gripper base by bearings, and one end is connected to the gripper drive drum via a gripper drive rope passing through the central cavity of the tensioned monolithic body. The ends of the four gripper links are hinged to the gripper base, and the center of each gripper link is hinged to an active connecting rod, forming a linkage force amplification mechanism. Specifically, the up-and-down movement of the central rod drives the cross-shaped connecting block to move axially, thereby pushing the active connecting rods, causing the four gripper links to synchronously retract inward or expand outward under the constraint of the active connecting rods.

[0012] The specific opening and closing configuration of the multi-link gripper is controlled by the forward and reverse rotation of the top outer gripper drive unit. It should be noted that the gripper drive drum converts rotational motion into linear motion of the central rod by winding and unwinding the gripper drive rope. Utilizing the lever amplification principle, the small torque of the motor is amplified into a large gripping force of the gripper. When gripping a target object, the gripper drive unit rotates forward, pulling the gripper transmission assembly through the gripper drive rope, causing the four gripper links to quickly retract under the constraint of the drive link, enveloping the outline of the target object. When release is needed, the gripper drive unit rotates backward, using the action of the central rod spring to automatically open the gripper. It should be noted that due to the use of a linkage transmission structure, this gripping mechanism can generate a large gripping force with a relatively small motor torque input, effectively preventing the object from slipping during transport.

[0013] Beneficial Effects: By using four differentially driven motors at the top to drive the torso, and one motor independently driving the gripper, in conjunction with the eight layers of Snelson tetrahedrons tensioning the entire torso, the robotic arm achieves continuous bending and large-angle torsion in three-dimensional space without singularities, as well as precise positioning and constant-force gripping of the end effector. The end effector employs a parallel four-bar adaptive gripping mechanism, enabling constant-force envelope gripping of objects of different geometric sizes. This flexible gripping robotic arm organically combines 3D-printed integrated rigid components with continuous transverse and axial flexible bodies, introducing the classic Snelson tetrahedral self-stress balance network. This completely eliminates the traditional central load-bearing column design, providing sufficient structural rigidity and load-bearing capacity while achieving extremely high environmental adaptability and human-machine interaction safety. It effectively solves the problems of poor obstacle avoidance ability of traditional rigid robotic arms and insufficient gripping force and low control precision of purely soft robotic arms. Furthermore, the independent control of five motors gives the robotic arm extremely high degrees of freedom of movement and control flexibility, enabling it to handle complex exploration and delicate operation tasks in narrow, unstructured environments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] Figure 1 The attached figure is a perspective view of a flexible clamping robotic arm based on a tensioned integral structure provided by the present invention.

[0016] Figure 2 The attached figure is a partially enlarged view of a flexible clamping robotic arm based on a tensioned integral structure provided by the present invention.

[0017] Figure 3The attached figure is a schematic diagram of the top drive module structure of a flexible clamping robotic arm based on a tensioned integral structure provided by the present invention.

[0018] Figure 4 The attached figure is a schematic diagram of a Snelson tetrahedral tensioned monolithic unit structure for a flexible gripping robotic arm based on a tensioned monolithic structure.

[0019] Figure 5 The attached figure is a schematic diagram of a flexible clamping robotic arm based on a tensioned integral structure.

[0020] Figure 6 The attached figure is a schematic diagram of the bending motion of a flexible clamping robotic arm based on a tensioned integral structure.

[0021] Labeling Explanation: 1. Top Drive Module; 101. Outer Frame; 102. Top Mounting Plate; 103. Torso Drive Unit; 104. Torso Active Drum; 105. Gripper Drive Unit; 106. Gripper Active Drum; 107. Central Guide Pulley; 108. Torso Drive Rope; 109. Gripper Drive Rope; 2. Tensioning Integrated Torso; 201. Snelson Tetrahedral Tensioning Integrated Unit; 20101. Lateral Flexible Body; 20102. Integrated Rigid Element; 20103. Axial Flexible Body; 3. End Adaptive Clamping Mechanism; 301. Gripper Transmission Assembly; 30101. Central Rod; 30102. Cross Connecting Block; 30103. Active Link; 302. Gripper Link; 303. Central Rod Spring; 304. Gripper Base. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other implementation methods obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] See Figure 1 and Figure 2This invention provides a flexible gripping robotic arm based on a tensioned integral structure, mainly comprising a top drive module 1, a tensioned integral body 2, and an end-effector adaptive gripping mechanism 3. The tensioned integral body 2 is coaxially mounted below the top drive module 1, and the end-effector adaptive gripping mechanism 3 is coaxially mounted at the bottom of the tensioned integral body 2. Specifically, the top drive module 1 is fixedly connected to the upper end of the tensioned integral body 2 by bolts to establish the relative position of the drive source and the body, avoiding uneven force on the drive rope due to installation errors; the lower end of the tensioned integral body 2 is connected to the end-effector adaptive gripping mechanism 3 through a rigid flange to ensure accurate transmission of gripping force and prevent torsional instability of the end effector due to eccentric force during multi-dimensional bending and gripping operations.

[0024] See Figures 1 to 3 The top drive module 1 is the core component that enables the robotic arm to bend, twist, and grasp. It mainly includes a housing frame 101, a top mounting plate 102, five stepper motors (four for torso drive units 103, one for gripper drive unit 105), four torso active drums 104, one gripper active drum 106, and a central guide pulley 107. The four torso drive units 103 are arranged in a rectangular array and fixed to the lower surface of the top mounting plate 102, with the torso active drums 104 keyed to their output shafts. The gripper drive unit 105 is located outside the rectangular array, with the gripper active drum 106 keyed to its output shaft.

[0025] See Figure 2 and Figure 3 The top mounting plate 102 is fixed to the top of the outer shell frame 101 by bolts. The central guide pulley 107 is fixedly installed at the geometric center of the top mounting plate 102 by a bearing seat, and is used to change the extension direction of the gripper drive rope 109, so that the gripper drive rope 109 is guided to the gripper drive unit 105; the torso drive ropes 108 output from the four torso active drums 104 directly and vertically penetrate into the interlayer nodes of the tensioned overall torso 2, and the attitude control of the torso is achieved through differential winding and unwinding. Specifically, the four torso drive units 103 achieve differential operation through program control, respectively winding and unwinding the torso drive ropes 108, and using the tension generated by the connection point between the rope and the tensioning unit to break the original prestress balance of the torso, forcing the torso to produce a predetermined bending or torsional deformation; the gripper drive unit 105 independently controls the forward and reverse rotation of the gripper active drum 106, and through the reversal of the central guide pulley 107, uses the gripper drive rope 109 to achieve precise opening and closing of the end adaptive clamping mechanism 3.

[0026] See Figure 4 and Figure 5The tensioned integral body is the core for achieving rigid-flexible coupling and large deformation motion, and is composed of eight layers of Snelson tetrahedral tensioned integral units 201 stacked along the axial direction. Each unit contains only an integral rigid element 20102 and two types of flexible elements, completely eliminating the traditional central load-bearing column and limiting tie rod.

[0027] Specifically, the integrated rigid element 20102 is a 3D-printed X-shaped structure, composed of four integrated inclined rigid rods, each with a connecting lug at its end. It should be noted that the integrated rigid elements 20102 in each layer do not contact each other; they are only spatially connected via flexible bodies, thus forming a stable self-stress equilibrium system under preload.

[0028] See Figure 4 , Figure 5 and Figure 6 The flexible bodies are divided into two categories: transverse flexible bodies 20101 and axial flexible bodies 20103. There are four transverse flexible bodies 20101, used to connect the bottom connecting lugs of the upper-layer integrated rigid element 20102 to the top connecting lugs of the current-layer integrated rigid element 20102. Through cross-layer oblique tensioning, they provide transverse prestress to each layer of rigid elements and limit inter-layer relative displacement. There are also four axial flexible bodies 20103, arranged around the outer perimeter of the torso, connecting the bottom connecting lugs of the upper-layer integrated rigid element 20102 to the bottom connecting lugs of the current-layer integrated rigid element 20102, and always remaining parallel to the central axis. They are used to maintain the axial prestress and structural stiffness of the entire tensioned torso 2. Through this tensioned overall configuration, the eight layers of integrated rigid elements 20102 simultaneously bear axial and transverse pressure. All flexible bodies are always in a bidirectional tensioned state, relying entirely on the structure's own self-stress balance characteristics to achieve structural continuity and overall load-bearing capacity of the robotic arm during significant bending.

[0029] See Figure 2 , Figure 5 and Figure 6 The end-effector adaptive clamping mechanism 3 mainly includes a gripper base 304, a central rod spring 303, a gripper connecting rod 302, and a gripper transmission assembly 301. The gripper base 304 is cylindrical, and its upper end is connected to the lowest integrated rigid element 20102 of the tensioned integral body 2. The gripper transmission assembly 301 includes a central rod 30101, a cross connecting block 30102, and four active connecting rods 30103. The central rod 30101 is supported inside the gripper base 304 by bearings, and one end of it is connected to the gripper active drum 106 through a gripper drive rope 109 that passes through the central cavity of the tensioned integral body 2.

[0030] See Figure 5 and Figure 6The linkage gripper consists of four gripper links 302 hinged to the gripper base 304. The center of each of the four gripper links 302 is hinged to the active link 30103 in the gripper transmission assembly 301, forming a linkage force amplification mechanism. Specifically, the axial movement of the center link 30101 drives the cross connecting block 30102 to move axially, thereby pushing the active link 30103, causing the four gripper links 302 to synchronously retract inward or open outward under the constraint of the active link 30103.

[0031] The opening and closing configuration of the linkage gripper is controlled by the forward and reverse rotation of the gripper drive unit 105. The gripper drive drum 106 converts rotational motion into linear motion of the central rod 30101 by winding and unwinding the gripper drive rope 109. Utilizing the lever principle, the small torque of the motor is amplified into a large gripping force of the gripper. When it is necessary to grasp the target object, the gripper drive unit 105 rotates forward, pulling the gripper transmission assembly 301 through the gripper drive rope 109, causing the four gripper linkages 302 to quickly retract and enclose the outline of the target object. When release is required, the gripper drive unit 105 rotates in reverse, using the action of the central rod spring 303 to automatically open the gripper. Due to the use of a linkage transmission structure, this gripping mechanism can generate a large gripping force with a relatively small motor torque input, effectively preventing the object from slipping during handling.

[0032] See Figures 1 to 6 The working mechanism of this invention is as follows: When bending and twisting combined control of the robotic arm is required, the four torso drive units 103 achieve differential operation through program control. When the drive rope in a certain quadrant tightens, the tensioning unit on that side is compressed, the integrated rigid element 20102 deflects, and the transverse flexible body 20101 and the axial flexible body 20103 maintain structural stability through internal force redistribution, thereby forcing the robotic arm to bend or twist towards the tightened side. Since the rigid elements of each layer do not contact each other and are only connected by flexible bodies, the robotic arm maintains good structural rigidity and impact resistance while possessing extremely high bending freedom. This stacked, tensioned modular design enables continuous bending of the robotic arm across multiple degrees of freedom across the entire scale. It decouples the self-stress equilibrium state formed by the compression members and tension cable nets within each module from the release and retraction of the external drive cable. This allows the robotic arm to perform obstacle avoidance and probe in complex, unstructured environments, similar to biological tentacles. Furthermore, by utilizing the unique mechanical redirection characteristics of axial compression and radial tension inherent in the tensioned modular structure, it generates synergistic deformation through the structural transmission of the main body when the end effector performs torsional operations, thereby achieving precise bending and torsion combination control within confined spaces.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible gripping robotic arm based on a tensioned integral structure, characterized in that, include: The structure comprises a top drive module (1), a tensioned integral torso (2), and an end-effector adaptive clamping mechanism (3). The tensioned integral torso (2) is composed of multiple layers of Snelson tetrahedral tensioned integral units (201). Each layer of Snelson tetrahedral tensioned integral unit (201) includes an integral rigid element (20102), a transverse flexible body (20101), and an axial flexible body (20103). The integral rigid elements (20102) of each layer do not contact each other and are connected in spatial topology only through the two types of flexible bodies. The top drive module... (1) Includes a torso drive unit (103), a gripper drive unit (105), a torso active drum (104), a gripper active drum (106), a central guide pulley (107), a torso drive rope (108), and a gripper drive rope (109). The gripper drive unit (105) is located outside the rectangular array formed by the four torso drive units (103). The end adaptive clamping mechanism (3) is connected to the gripper drive unit (105) through the gripper drive rope (109) that passes through the central cavity of the tensioned overall torso (2).

2. The flexible gripping robotic arm according to claim 1, characterized in that, The integrated rigid element (20102) is a 3D-printed X-shaped structure, consisting of two horizontal rigid connecting rods and two inclined rigid connecting rods integrated together. The flexible body is divided into a transverse flexible body (20101) and an axial flexible body (20103). The transverse flexible body (20101) connects the bottom lug of the upper integrated rigid element (20102) to the top lug of the current integrated rigid element (20102). The axial flexible body (20103) connects the bottom lug of the upper integrated rigid element (20102) to the bottom lug of the current integrated rigid element (20102) and remains parallel to the central axis.

3. The flexible gripping robotic arm according to claim 1, characterized in that, The central guide pulley (107) is mounted at the geometric center of the top mounting plate (102) to change the extension direction of the gripper drive rope (109) and guide the rope axially to the gripper drive unit (105) located outside the rectangular array.

4. The flexible gripping robotic arm according to claim 1, characterized in that, One end of the torso drive rope (108) is fixed to the torso active drum (104), and the other end is inserted vertically downward into the node in the middle of each layer of the tensioned whole torso 2, and finally fixed to the Snelson tetrahedral tensioning whole unit (201) at the bottom of the tensioned whole torso (2); the attitude control of the tensioned whole torso (2) is achieved by adjusting the rotation angle of the four torso drive units (103).

5. The flexible gripping robotic arm according to claim 1, characterized in that, The end-effector adaptive clamping mechanism (3) includes a gripper base (304), a central rod spring (303), a gripper connecting rod (302), and a gripper transmission assembly (301); the gripper transmission assembly (301) includes a central rod (30101), a cross connecting block (30102), and four active connecting rods (30103); the central rod (30101) is connected to the inside of the gripper base (304) by a bearing, one end of which passes through the central cavity of the tensioned integral torso (2) and is connected to the gripper drive rope (109), and the other end is connected to the ten The cross connecting block (30102) is connected, and the central rod (30101) can drive the cross connecting block (30102) to move axially; the top ends of the four gripper connecting rods (302) are hinged to the gripper base (304), and the center position of the four gripper connecting rods (302) is hinged to one end of the active connecting rod (30103) to form a connecting rod force amplification mechanism; the axial movement of the cross connecting block (30102) drives the rotation of a pair of active connecting rods (30103), which in turn is converted into the synchronous closing or opening of the four gripper connecting rods (302).

6. The flexible gripping robotic arm according to claim 4, characterized in that, The gripper transmission assembly (301) is also provided with a center rod spring (303); the center rod spring (303) is sleeved on the center rod (30101), one end is fixed to the inner wall of the gripper base (304), and the other end is fixed to the surface of the cross connecting block (30102); when the gripper drive unit (105) reverses and releases the gripper drive rope (109), the center rod spring (303) pushes the center rod (30101) forward along the axial direction of the robotic arm, pushes the cross connecting block (30102) to reset, and then realizes the automatic opening of the end adaptive gripping mechanism (3) through linkage.

7. The flexible gripping robotic arm according to claim 1, characterized in that, The tensioned integral body (2) is composed of eight layers of Snelson tetrahedral tensioned integral units (201) stacked together; the gripper base (304) of the end adaptive clamping mechanism (3) is cylindrical, and its upper end is directly connected to the bottom connecting rod end of the integral rigid element (20102) in the bottom layer, and its lower end is fastened by a rigid flange, forming a pure tensioning mechanical arm structure without a central load-bearing column.

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