A rigid-flexible coupling adaptive manipulator based on rope-driven variable stiffness

Abstract

The application discloses a kind of rigid-flexible coupling adaptive manipulator based on rope drive variable stiffness, belong to manipulator technical field.The manipulator includes installation shell and adapter component, variable stiffness component, finger component and drive component, drive component is built in installation shell and adapter component, provides stiffness adjustment driving force for variable stiffness component by variable stiffness drive rope, finger component is the structure of pneumatic drive type, its bending action drives variable stiffness component synchronous flexion and extension;Variable stiffness component relies on the dead point characteristics of crank slider mechanism and the torsional elasticity of torsion spring to realize stiffness accurate regulation and control, soft finger is provided with recessed cavity and bottom limiting layer, guarantee the controllability and large-angle characteristics of bending.The application has compact structure, stiffness adjustment is continuous and fast response, high precision and stability of gripping, can realize rigid-flexible coupling adaptive gripping, modular design can be adapted to diversified gripping scene, can be widely applied to medical rehabilitation, precision assembly, fragile product sorting and other fields.

Description

Technical Field

[0001] This invention relates to the field of robotic arm technology, and in particular to a rigid-flexible coupling adaptive robotic arm based on rope-driven variable stiffness. Background Technology

[0002] As robotics extends into unstructured environments, soft robotic grippers have become a research hotspot. Their core components, the rope-driven variable stiffness structure and the pneumatic soft mechanical fingers, are key to achieving both "flexible fit" and "rigid load-bearing capacity." The two-finger assembly, due to its simple structure and convenient control, has become the mainstream choice for small soft grippers. The rope-driven variable stiffness structure, with its advantages of compactness, flexibility, and low energy consumption, can adjust stiffness through rope tension and is widely used in soft robotic arms and bionic grippers. The pneumatic soft mechanical fingers, relying on the expansion and contraction of soft material air cavities to simulate finger flexion, are suitable for grasping irregular and fragile items. Currently, the industry has attempted to combine these two technologies to assemble a two-finger gripper that balances flexibility and stability. However, existing technologies still have many shortcomings, making it difficult to meet the demands for high-precision and high-stability grasping. The rope-driven variable stiffness structure suffers from poor adjustment continuity and a narrow range, slow response, unreasonable rope force distribution leading to loosening and wear, and poor integration with the pneumatic soft fingers, resulting in a relatively large gripper size. Secondly, pneumatic soft mechanical fingers suffer from poor controllability in bending and weak load-bearing capacity. Improper integration with variable stiffness structures can easily lead to motion interference. Furthermore, it's difficult to balance material flexibility and wear resistance, resulting in insufficient grasping accuracy. Finally, poor coordination in two-finger assembly, inconvenient adjustment of spacing and opening angle, insufficient drive synchronization, and difficulty in coordinating rope and pneumatic drives, failing to fully leverage the advantages of both. Additionally, some structural power sources are bulky, limiting mobile operation capabilities. Specifically, the limitations of variable stiffness adjustment, insufficient controllability of finger movements, and poor multi-finger coordination collectively make existing two-finger soft grippers unsuitable for practical applications requiring high grasping accuracy, stability, and adaptability, such as medical rehabilitation, precision assembly, and fragile item sorting. They cannot fully utilize the technical advantages of combining rope-driven variable stiffness with pneumatic drive, thus limiting the further promotion and industrial application of soft gripper technology. Summary of the Invention

[0003] The purpose of this invention is to provide a rope-driven variable stiffness rigid-flexible coupling adaptive manipulator, which has a compact structure, precise and continuous variable stiffness adjustment, strong controllability of finger bending movements, and smooth two-finger coordination. This invention promotes the upgrading and iteration of the technology combining rope-driven variable stiffness and pneumatic soft mechanical fingers, and meets the high-end application needs of flexible grippers in various fields.

[0004] To achieve the above objectives, the present invention provides a rope-driven variable stiffness rigid-flexible coupling adaptive manipulator, comprising a mounting housing and adapter assembly, a variable stiffness assembly, a finger assembly, and a drive assembly; the drive assembly is disposed inside the mounting housing and adapter assembly, and the two ends of the variable stiffness assembly are respectively connected to the mounting housing and adapter assembly and the finger assembly; the drive assembly is connected to the variable stiffness assembly via a variable stiffness drive rope, providing a driving force for stiffness adjustment of the variable stiffness assembly; the finger assembly is a pneumatically driven structure, and its bending action drives the variable stiffness assembly to bend and straighten synchronously.

[0005] Preferably, the mounting housing and adapter assembly includes a robotic arm adapter, an upper mounting housing, a drive component mounting housing, a lower mounting housing, and a mounting base; the robotic arm adapter mates with the shaft hole of the upper mounting housing and is connected by bolts, the upper mounting housing is bolted to the lower mounting housing, the drive component mounting housing is located inside the upper mounting housing, the lower mounting housing is connected to the mounting base, and the mounting base is connected to the variable stiffness component and the finger component respectively.

[0006] Preferably, the mounting housing has a mounting shaft hole, a wire passage hole, and a first through hole, a second through hole, and a third through hole; the robotic arm adapter is mounted at the mounting shaft hole and is bolted in place through the second and third through holes. The drive assembly mounting shell has an internal drive first through hole for fixing the drive plate, a drive second through hole and a drive recessed through hole for mounting the servo, a wiring hole for servo wires connecting the servo and the drive plate, and a drive third through hole for connecting the mounting shell; the drive second through hole is used for servo positioning, and the drive recessed through hole is used for bolt connection with the servo. The mounting base has a first through hole for connecting a rope pulley, a second through hole for placing an air pipe connector, a recessed through hole for mounting a finger assembly, a rope guide hole for threading a variable stiffness drive rope, and a third through hole for connecting the mounting lower shell; the mounting base is equipped with a rope pulley.

[0007] Preferably, the drive assembly includes a drive plate, a servo motor, a servo motor adapter, a cable fixing disc, and a hexagon head screw; the drive plate is fixed inside the column of the drive assembly mounting housing at the drive first through hole, and the servo motor is fixed to the drive assembly mounting housing through the drive second through hole and the drive recessed through hole; the cable fixing disc is connected to the servo motor through the servo motor adapter and fixed with a hexagon head screw, and a variable stiffness drive cable is wound on the cable fixing disc, the variable stiffness drive cable passes through the cable guide hole of the mounting base and the cable pulley and is connected to the variable stiffness assembly.

[0008] Preferably, the variable stiffness assembly includes a variable stiffness joint unit, a lower connecting rod, a middle connecting rod, an upper connecting rod, a cylindrical head screw, and a set screw; the variable stiffness joint unit is connected to the lower connecting rod, the middle connecting rod, and the upper connecting rod via set screws; the upper part of the variable stiffness assembly is connected to the first through hole of the finger assembly connector via the upper connecting rod mounting shaft of the upper connecting rod; and the lower part of the variable stiffness assembly is connected to the soft finger variable stiffness joint mounting hole of the finger assembly via the lower connecting rod mounting shaft of the lower connecting rod.

[0009] Preferably, the lower connecting rod has a lower connecting rod threaded hole and a lower connecting rod mounting shaft; the middle connecting rod has a middle connecting rod first threaded hole, a middle connecting rod second threaded hole and a middle connecting rod through hole for wiring; the upper connecting rod has an upper connecting rod first threaded hole, an upper connecting rod second threaded hole, a wire passage hole and an upper connecting rod mounting shaft.

[0010] Preferably, the variable stiffness joint unit includes a joint end, a joint cavity, a clamping block, a joint connecting rod, a torsion spring, a circular turntable, a triangular turntable, a joint set screw, and a joint countersunk screw; the triangular turntable is threadedly connected to the connecting rod through holes of the three joint connecting rods through the joint countersunk screws, and the clamping block mounting shafts of the three joint connecting rods are respectively connected to the three clamping blocks, forming three sets of crank-slider mechanisms, and the three clamping blocks move synchronously centripetally or centrifugally along a fixed slide rail; the torsion spring is respectively connected to the circular turntable and the triangular turntable; the variable stiffness drive rope is tied to the bottom of the triangular turntable and is connected to the drive assembly for transmission.

[0011] Preferably, the circular turntable has a circular torsion spring groove, a circular through hole, a circular threaded hole, and a circular wire hole; the triangular turntable has a triangular wire hole, a triangular torsion spring groove, and a triangular through hole; the torsion spring is engaged in the circular torsion spring groove and the triangular torsion spring groove; the joint connecting rod has a connecting rod through hole and a clamping block mounting shaft; the clamping block has a light hole that mates with the clamping block mounting shaft.

[0012] Preferably, the finger assembly includes a soft finger, a finger connector, an air tube connector, and a countersunk screw; the soft finger is connected to the finger connector, the air tube connector passes through the air tube mounting through hole of the finger connector and the second through hole of the mounting base, the finger connector is fixed to the recessed through hole of the mounting base by the countersunk screw, and the finger connector has a first through hole, a second through hole, and an air tube mounting through hole.

[0013] Preferably, the soft finger includes a soft finger body and a limiting layer. The soft finger body has an air intake line, a finger joint chamber, and a variable stiffness joint mounting hole inside. The finger joint chamber is groove-shaped. The air intake line is connected to each finger joint chamber. The limiting layer is located in the middle of the bottom sealing layer of the soft finger body. The sealing layer is used to ensure the sealing of the soft finger body, and the bottom of the sealing layer is made of silicone to increase the friction when grasping objects. The limiting layer restricts the stretching of the bottom of the soft finger body and guides the soft finger to bend in a preset direction.

[0014] Therefore, the present invention adopts the above-mentioned rigid-flexible coupling adaptive manipulator based on rope-driven variable stiffness, which has a compact structure, continuous stiffness adjustment and fast response, strong controllability of soft finger bending and large bending angle, and can realize rigid-flexible coupling adaptive grasping with high grasping accuracy and stability; the modular design can flexibly adjust the structure to adapt to diverse grasping scenarios.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is an assembly drawing of the variable stiffness pneumatic manipulator according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the assembly drawing of the variable stiffness pneumatic manipulator according to an embodiment of the present invention; Figure 3 This is an assembly diagram of the driving component according to an embodiment of the present invention; Figure 4 This is an exploded view of the assembly of some components of the drive component according to an embodiment of the present invention; Figure 5 This is an assembly diagram of the mounting housing and adapter assembly according to an embodiment of the present invention; Figure 6 This is the mounting shell for the driver component in an embodiment of the present invention; Figure 7 This is an assembly diagram of the finger assembly according to an embodiment of the present invention; Figure 8 This is an assembly diagram of the variable stiffness component according to an embodiment of the present invention; Figure 9 This is an assembly diagram of the variable stiffness joint unit according to an embodiment of the present invention; Figure 10 This is an assembly diagram of some parts of the variable stiffness joint unit according to an embodiment of the present invention; Figure 11 This is an assembly diagram of the soft finger according to an embodiment of the present invention; Figure 12 This is a cross-sectional view of a soft finger according to an embodiment of the present invention; Figure 13 This is an overall structural diagram of the soft finger according to an embodiment of the present invention; Figure 14 This is the mounting base according to an embodiment of the present invention; Figure 15 This is the mounting shell according to an embodiment of the present invention; Figure 16 This is a variable stiffness structural link according to an embodiment of the present invention; Figure 17 These are the circular turntable and the triangular turntable of this invention. Figure 18 This is an installation diagram of the variable stiffness structure connecting rod according to an embodiment of the present invention; Figure 19 This is an installation diagram of the variable stiffness torsion spring structure according to an embodiment of the present invention; Figure 20 This invention relates to the principle of stiffness increase based on centering clamping and the dead point position of the connecting rod. Figure 21 This is a schematic diagram illustrating the principle of variable stiffness control according to an embodiment of the present invention; Figure 22 This is the principle of finger pneumatic bending in this embodiment of the invention.

[0017] Figure Labels 1. Mounting housing and adapter assembly; 2. Variable stiffness assembly; 3. Finger assembly; 4. Drive assembly; 11. Robotic arm adapter; 12. Mounting upper housing; 12A. Mounting shaft hole; 12B. Wiring hole; 12C. Upper housing first through hole; 12D. Upper housing second through hole; 12E. Upper housing third through hole; 13. Drive assembly mounting housing; 13A. Drive first through hole; 13B. Drive second through hole; 13C. Drive recessed through hole; 13D. Wiring hole; 13E. Drive third through hole; 14. Mounting lower housing; 15. Mounting base; 15A. Base first... 15B, Second through hole in the base; 15C, Recessed through hole in the base; 15D, Third through hole in the base; 15E, Rope passage hole; 21, Variable stiffness joint unit; 22, Lower connecting rod; 22A, Threaded hole in the lower connecting rod; 22C, Mounting shaft of the lower connecting rod; 23, Middle connecting rod; 23A, First threaded hole in the middle connecting rod; 23B, Through hole in the middle connecting rod; 23C, Second threaded hole in the middle connecting rod; 24, Upper connecting rod; 24A, First threaded hole in the upper connecting rod; 24B, Second threaded hole in the upper connecting rod; 24C, Passing hole; 24D, Mounting shaft of the upper connecting rod; 25, Cylindrical head screw. 26. Set screw; 211. Joint end; 212. Joint cavity; 213. Clamping block; 213A. Smooth hole; 214. Joint connecting rod; 214A. Clamping block mounting shaft; 214B. Connecting rod through hole; 215. Torsion spring; 216. Circular turntable; 216A. Circular turntable torsion spring slot; 216B. Circular turntable through hole; 216C. Circular turntable threaded hole; 216D. Circular turntable wire hole; 217. Triangular turntable; 217A. Triangular turntable wire hole; 217B. Triangular turntable torsion spring slot; 217C. Triangular turntable through hole; 218. Joint set screw; 2 19. Joint countersunk screw; 31. Soft finger; 311. Soft finger body; 312. Restriction layer; 31A. Air intake line; 31B. Finger joint chamber; 31C. Variable stiffness joint mounting hole; 32. Finger connector; 32A. Connector first through hole; 32B. Connector second through hole; 32C. Air pipe mounting through hole; 33. Air pipe connector; 34. Countersunk screw; 41. Drive plate; 42. Servo; 43. Servo adapter; 44. Rope retaining disc; 45. Socket head cap screw; 46. Variable stiffness drive rope; 47. Rope pulley. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example 1 like Figure 1-2 As shown, the rope-driven variable stiffness-based rigid-flexible coupling adaptive manipulator of this embodiment mainly consists of four parts: a mounting housing and adapter component 1, a variable stiffness component 2, a finger component 3, and a drive component 4. The drive component 4 is integrated inside the mounting housing and adapter component 1, improving the overall integration of the manipulator. The upper and lower ends of the variable stiffness component 2 are connected to the mounting housing and adapter component 1 and the finger component 3, respectively, to achieve synchronous motion transmission. The drive component 4 is connected to the variable stiffness component 2 via a variable stiffness drive rope 46, providing a stable driving force for the stiffness adjustment of the variable stiffness component 2. The finger component 3 is a pneumatically driven flexible structure, and its bending and straightening movements under pneumatic action can drive the variable stiffness component 2 to complete bending and straightening synchronously, realizing rigid-flexible coupling motion coordination.

[0021] The specific structure and connection relationship of the mounting housing and adapter assembly 1 are as follows: like Figure 2 , 5 As shown in Figures 6, 14, and 15, the mounting housing and adapter assembly 1 forms the basic support structure for the robotic arm, including a robotic arm adapter 11, an upper mounting housing 12, a drive component mounting housing 13, a lower mounting housing 14, and a mounting base 15. The robotic arm adapter 11 is positioned with the upper mounting housing 12 via a shaft-hole fit and is secured with bolts, achieving a stable connection between the robotic arm and the external robotic arm. The upper mounting housing 12 and the lower mounting housing 14 are directly and detachably connected via bolts, facilitating the installation and maintenance of internal components. The drive component mounting housing 13 is located inside the upper mounting housing 12, providing dedicated installation space for the drive component 4. The lower end of the lower mounting housing 14 connects to the mounting base 15, which serves as the mounting carrier for the variable stiffness component 2 and the finger component 3, respectively connecting to both.

[0022] The upper housing 12 has a mounting shaft hole 12A, a wire passage hole 12B, and three through holes: a first through hole 12C, a second through hole 12D, and a third through hole 12E. The robotic arm adapter 11 is precisely installed at the mounting shaft hole 12A to enable docking with an external robotic arm. The wire passage hole 12B is used to pass through the internal circuit connection wires of the robotic arm, preventing messy wiring from affecting the movement of the components. The other through holes are for auxiliary installation and weight reduction.

[0023] The drive assembly mounting shell 13 is designed to accommodate the precise installation of the drive assembly 4. It has an internal drive first through hole 13A for fixing the drive plate 41, a drive second through hole 13B for mounting the servo motor 42, and a drive recessed through hole 13C. It also has a wiring hole 13D for arranging the connection line between the servo motor and the drive plate, and a drive third through hole 13E for connecting the mounting shell 14. Each hole is precisely opened according to the component layout of the drive assembly 4 to ensure the coaxiality and motion stability of the drive components after installation. The wiring hole 13D enables the concealed arrangement of the wiring to prevent interference between the wiring and the moving parts.

[0024] The mounting base 15 has a first through hole 15A, a second through hole 15B, a recessed through hole 15C, a third through hole 15D, and a rope passage hole 15E. The rope pulley 47 is mounted at the first through hole 15A via a pivot shaft, used to change the transmission direction of the variable stiffness drive rope 46 and reduce the friction of the rope transmission. The second through hole 15B is used to pass through the air pipe connector 33, enabling communication between the pneumatic pipeline and the finger assembly 3. The recessed through hole 15C is the mounting positioning hole for the finger connector 32, ensuring the installation angle of the finger assembly 3. The third through hole 15D is used to connect to the mounting lower shell 14. The rope passage hole 15E is a dedicated routing hole for the variable stiffness drive rope 46, preventing the rope from contacting and wearing with other components.

[0025] The structure and transmission relationship of drive component 4: like Figure 3 , 4As shown, the drive assembly 4 is the power output unit of the robot, including a drive plate 41, a servo motor 42, a servo motor adapter 43, a cable fixing disc 44, and an internal hexagon head screw 45. The drive plate 41 is bolted to the inside of the column of the drive assembly mounting housing 13 at the drive first through hole 13A, providing power and control signals to the servo motor 42. The servo motor 42 is positioned by driving the second through hole 13B and is securely fixed to the drive assembly mounting housing 13 by driving the recessed through hole 13C, ensuring no vibration or deviation during operation. One side of the cable fixing disc 44 is coaxially connected to the output shaft of the servo motor 42 via the servo motor adapter 43, and the other side is locked in place by the internal hexagon head screw 45 to prevent slippage during transmission. The outer circumferential surface of the rope fixing plate 44 is provided with a rope slot. One end of the variable stiffness drive rope 46 is wound around and fixed in the rope slot, and the other end passes through the rope passage hole 15E of the mounting base 15 and the rope pulley 47 in sequence, and then is wrapped and tied to the bottom of the triangular turntable 217 of the variable stiffness component 2, so as to realize the flexible transmission between the drive component 4 and the variable stiffness component 2. The rotational motion of the servo motor 42 can be converted into the linear tensioning motion of the variable stiffness drive rope 46 through the rope fixing plate 44.

[0026] The structure and connection relationship of variable stiffness component 2: like Figure 8 , 9 As shown in Figures 10, 16, 17, 18, and 19, the variable stiffness assembly 2 is the core structure for realizing the stiffness-flexibility switching of the robotic arm. It includes a variable stiffness joint unit 21, a lower connecting rod 22, a middle connecting rod 23, an upper connecting rod 24, a cylindrical head screw 25, and a set screw 26. The variable stiffness joint unit 21 is the actuator for variable stiffness adjustment. It is circumferentially locked and axially fixed with the lower connecting rod 22, the middle connecting rod 23, and the upper connecting rod 24 through the set screw 26, ensuring the synchronization of movement between the connecting rods and the joint unit. The upper part of the variable stiffness assembly 2 is connected to the first through hole 32A of the connecting member on the finger connector 32 of the finger assembly 3 through the upper connecting rod mounting shaft 24D at the end of the upper connecting rod 24. The lower part of the variable stiffness component 2 is connected to the soft finger variable stiffness joint mounting hole 31C on the soft finger 31 of the finger component 3 through the lower connecting rod mounting shaft 22C at the end of the lower connecting rod 22, thereby realizing the connection between the variable stiffness component 2 and the finger component 3 and ensuring that the bending action of the finger component 3 can be synchronously transmitted to the variable stiffness component 2.

[0027] The lower connecting rod 22, middle connecting rod 23, and upper connecting rod 24 form the linkage transmission structure of the variable stiffness assembly 2. Different hole positions are designed according to the motion transmission path: the lower connecting rod 22 has a lower connecting rod threaded hole 22A and a lower connecting rod mounting shaft 22C; the middle connecting rod 23 has a middle connecting rod first threaded hole 23A, a middle connecting rod second threaded hole 23C, and a middle connecting rod through hole 23B for wiring; the upper connecting rod 24 has an upper connecting rod first threaded hole 24A, an upper connecting rod second threaded hole 24B, a wire passage hole 24C, and an upper connecting rod mounting shaft 24D. Except for the upper connecting rod second threaded hole 24B, which connects to the connector first through hole 32A via a cylindrical head screw 25, the threaded holes of each connecting rod are used for connection to the variable stiffness joint unit 21, the through holes are for weight reduction and auxiliary mounting, and the wire passage hole 24C of the upper connecting rod 24 is used to thread the variable stiffness drive rope 46.

[0028] The variable stiffness joint unit 21 includes a joint end 211, a joint cavity 212, a clamping block 213, a joint connecting rod 214, a torsion spring 215, a circular turntable 216, a triangular turntable 217, a joint set screw 218, and a joint countersunk screw 219. The three ends of the triangular turntable 217 are coaxially threaded to the connecting rod through holes 214B of the three joint connecting rods 214 via the joint countersunk screws 219. Each of the three joint connecting rods 214 has a clamping block mounting shaft 214A integrally formed at the end furthest from the triangular turntable 217. The clamping block mounting shaft 214A is connected to the light hole 213A at the bottom of the clamping block 213. The three joint connecting rods 214 and the three clamping blocks 213 respectively constitute three sets of symmetrically distributed crank-slider mechanisms. The three clamping blocks 213 can perform synchronous centripetal or centrifugal linear motion along a fixed slide rail. The circular turntable 216 and the triangular turntable 217 are arranged coaxially. The two ends of the torsion spring 215 are respectively engaged in the circular torsion spring slot 216A of the circular turntable 216 and the triangular torsion spring slot 217B of the triangular turntable 217, providing a restoring elastic force for the triangular turntable 217. The free end of the variable stiffness drive rope 46 is tied to the triangular wire hole 217A at the bottom of the triangular turntable 217, forming a transmission engagement with the drive assembly 4. The joint set screw 218 is used to connect the joint cavity 212 to the circular turntable 216.

[0029] The circular turntable 216 and the triangular turntable 217 are provided with multiple sets of holes and slots according to functional requirements: the circular turntable 216 has a disc torsion spring slot 216A, a disc through hole 216B, a disc threaded hole 216C, and a disc wire hole 216D. The disc through hole 216B is used to connect with the triangular turntable 217, and the disc threaded hole 216C is used to connect with the lower connecting rod 22, the middle connecting rod 23, and the upper connecting rod 24. The disc wire hole 216D is used to pass through the variable stiffness drive rope 46. The triangular turntable 217 has a triangular disc wire hole 217A, a triangular disc torsion spring slot 217B, and a triangular disc through hole 217C. The joint link 214 has a connecting rod through hole 214B and an integrally formed clamping block mounting shaft 214A. The connecting rod through hole 214B and the triangular disk through hole 217C are installed by a joint countersunk screw 219. The clamping block mounting shaft 214A achieves a precise connection with the clamping block 213. The tension of the variable stiffness drive rope 46 drives the rotation of the triangular turntable 217, thereby driving the joint link 214 fixed at the three holes of the triangular turntable 217 to rotate, which in turn drives the movement of the clamping block 213.

[0030] Structure and pneumatic drive design of finger assembly 3: like Figure 7 , 11 As shown in Figures 12 and 13, the finger assembly 3 is a flexible grasping and actuation structure for the robotic arm, including a soft finger 31, a finger connector 32, an air pipe connector 33, and a countersunk screw 34. The upper end of the soft finger 31 is connected to the lower end of the finger connector 32 to ensure a tight and stable connection. One end of the air pipe connector 33 passes through the air pipe mounting hole 32C of the finger connector 32 and connects to the air inlet line 31A of the soft finger 31. The other end passes through the second through hole 15B of the mounting base 15 and connects to an external pneumatic air supply device to achieve a stable delivery of compressed gas. The finger connector 32 is locked and fixed to the countersunk through hole 15C of the mounting base 15 via the second through hole 32B using the countersunk screw 34. The head of the countersunk screw 34 is recessed into the countersunk through hole 15C to prevent protrusion from affecting the movement of other components. The finger connector 32 also has a first through hole 32A and a second through hole 32B. The first through hole 32A is used to connect with the upper connecting rod mounting shaft 24D of the variable stiffness assembly 2, and the second through hole 32B is a threaded hole.

[0031] The soft finger 31 is a flexible pneumatic structure, comprising a soft finger body 311 and a limiting layer 312. The soft finger body 311 is integrally molded from a flexible elastic material, and its interior has an air inlet line 31A, a finger joint chamber 31B, and a variable stiffness joint mounting hole 31C. The air inlet line 31A is arranged along the length of the soft finger body 311 and connects to each finger joint chamber 31B, providing uniform compressed gas to each chamber. The finger joint chamber 31B is grooved, and compared to the traditional circular air chamber, this structure has a stronger extrusion deformation capacity, enabling the air chamber to expand in two stages (upper and lower). Multiple layers of grooves can be stacked according to design requirements to achieve multi-stage expansion, expanding the deformation control methods and application range of the soft finger. The variable stiffness joint mounting hole 31C is used to connect to the lower connecting rod mounting shaft 22C of the variable stiffness component 2. The limiting layer 312 is located in the middle of the bottom sealing layer of the soft finger body 311. The sealing layer is used to ensure the sealing of the soft finger body 311, and the bottom of the sealing layer is made of silicone to increase the friction when grasping objects. The limiting layer 312 restricts the stretching of the bottom of the soft finger body 311 and guides the soft finger 31 to bend in a preset direction.

[0032] The robotic hand in this embodiment achieves adaptive grasping of objects of different sizes, shapes, and materials through the pneumatic bending of the finger assembly, the stiffness adjustment of the variable stiffness assembly, and the rigid-flexible coupling and coordinated motion of the two. The specific working principle is as follows: The pneumatic bending principle of soft fingers: like Figure 22 As shown, an external pneumatic air supply device introduces compressed gas into the air inlet line 31A of the soft finger 31 through the air pipe connector 33. The compressed gas enters each finger joint chamber 31B evenly along the air inlet line 31A. Under the action of gas pressure, the soft finger body 311 undergoes elastic expansion and deformation. Since the bottom of the soft finger body 311 is equipped with a limiting layer 312, the soft finger 31 will make an arc-shaped bending movement along a preset direction. The bending angle increases with the increase of the air supply pressure. Under the condition of an air supply pressure of 30 kPa, the bending angle of the soft finger 31 can reach 300°, which has the characteristics of significant bending effect, flexible movement and fast response speed. When the compressed gas in the finger joint chamber 31B is discharged, the soft finger body 311 returns to its original position under its own elastic action, causing the soft finger 31 to straighten. During the bending and straightening process, the soft finger 31 will drive the variable stiffness component 2 to complete the bending and straightening synchronously through the lower connecting rod 22 and the upper connecting rod 24, realizing the coordinated movement of the two.

[0033] The stiffness control principle of variable stiffness components: like Figure 20 , 21 As shown, the stiffness adjustment of the variable stiffness component 2 is divided into two processes: stiffness enhancement and stiffness release. Stable stiffness locking is achieved by relying on the dead-point characteristics of the crank-slider mechanism, and rapid recovery of flexibility is achieved by relying on the restoring force of the torsion spring. Stiffness Enhancement: When it is necessary to enhance the stiffness of the manipulator to achieve rigid load-bearing capacity, the drive plate 41 sends a control signal to the servo motor 42. The output shaft of the servo motor 42 rotates clockwise, causing the rope fixing plate 44 to rotate synchronously, thereby tensioning the variable stiffness drive rope 46. The variable stiffness drive rope 46 pulls the triangular turntable 217 to rotate around its central axis. The triangular turntable 217 drives three clamping blocks 213 to move synchronously along the fixed slide rail via three joint connecting rods 214. When the joint connecting rods 214 move to the dead point position of the crank-slider mechanism, the three clamping blocks 213 clamp and lock the shaft of the joint end 211. At this time, no matter how much external force is applied to the joint end 211, it is impossible to drive the clamping blocks 213 and the joint connecting rods 214 to move, thus locking the joint and completing the stiffness enhancement of the variable stiffness component 2.

[0034] Stiffness Release: When it is necessary to reduce the stiffness of the manipulator to achieve flexible fit, the drive plate 41 controls the servo motor 42 to stop working, and the variable stiffness drive rope 46 loses its tension and is in a relaxed state. At this time, the torsion spring 215 connected to the circular turntable 216 and the triangular turntable 217, under the action of its own elastic restoring force, drives the triangular turntable 217 to rotate in the opposite direction to reset. The triangular turntable 217 drives the three clamping blocks 213 to make synchronous centrifugal motion along the fixed slide rail through the three joint connecting rods 214, loosening the grip on the shaft of the joint end 211, realizing joint unlocking, and restoring the flexibility of the variable stiffness component 2.

[0035] The adaptive grasping principle of rigid-flexible coupling: When the robotic arm grasps an object, low-pressure compressed gas is first introduced into the soft finger 31 through an external pneumatic air supply device. The soft finger 31 slowly bends, causing the variable stiffness component 2 to bend synchronously. At this time, the variable stiffness component 2 is in a flexible state, allowing the soft finger 31 to fully and flexibly conform to the surface of the object being grasped, avoiding crushing damage to fragile or precision parts. Once the soft finger 31 is fully in contact with the object, the drive component 4 drives the variable stiffness component 2 to increase its stiffness, switching the robotic arm to a rigid state and achieving stable rigid support for the object. After grasping, the drive component 4 first drives the variable stiffness component 2 to release its stiffness, then discharges the compressed gas from the soft finger 31, causing the soft finger 31 to straighten and return to its original position, completing the unloading process. Throughout the grasping process, the movement and stiffness switching of the finger component 3 and the variable stiffness component 2 are coordinated, achieving adaptive grasping with rigid-flexible coupling.

[0036] Therefore, the present invention adopts the above-mentioned rigid-flexible coupling adaptive manipulator based on rope-driven variable stiffness, which has a compact structure, continuous stiffness adjustment and fast response, strong controllability of soft finger bending and large bending angle, and can realize rigid-flexible coupling adaptive grasping with high grasping accuracy and stability; the modular design can flexibly adjust the structure to adapt to diverse grasping scenarios.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A rigid-flexible coupled adaptive manipulator based on cable-driven variable stiffness, characterized in that, The system includes a mounting housing and adapter assembly (1), a variable stiffness assembly (2), a finger assembly (3), and a drive assembly (4). The drive assembly (4) is located inside the mounting housing and adapter assembly (1). The two ends of the variable stiffness assembly (2) are connected to the mounting housing and adapter assembly (1) and the finger assembly (3), respectively. The drive assembly (4) is connected to the variable stiffness assembly (2) via a variable stiffness drive rope (46) to provide a driving force for stiffness adjustment of the variable stiffness assembly (2). The finger assembly (3) is a pneumatically driven structure, and its bending action drives the variable stiffness assembly (2) to bend and straighten synchronously. The variable stiffness assembly (2) includes a variable stiffness joint unit (21), a lower connecting rod (22), a middle connecting rod (23), an upper connecting rod (24), a cylindrical head screw (25), and a set screw (26); the variable stiffness joint unit (21) is connected to the lower connecting rod (22), the middle connecting rod (23), and the upper connecting rod (24) by the set screw (26); the upper part of the variable stiffness assembly (2) is connected to the first through hole (32A) of the connector of the finger assembly (3) through the upper connecting rod mounting shaft (24D) of the upper connecting rod (24); and the lower part of the variable stiffness assembly (2) is connected to the soft finger variable stiffness joint mounting hole (31C) of the finger assembly (3) through the lower connecting rod mounting shaft (22C) of the lower connecting rod (22). The variable stiffness joint unit (21) includes a joint end (211), a joint cavity (212), a clamping block (213), a joint connecting rod (214), a torsion spring (215), a circular turntable (216), a triangular turntable (217), a joint set screw (218), and a joint countersunk screw (219); the triangular turntable (217) is threadedly connected to the connecting rod through holes (214B) of the three joint connecting rods (214) through the joint countersunk screw (219). The clamping block mounting shaft (214A) of the three joint connecting rods (214) is connected to the three clamping blocks (213) respectively, forming three sets of crank-slider mechanisms. The three clamping blocks (213) move synchronously in a centripetal or centrifugal motion along the fixed slide rail. The torsion spring (215) is connected to the circular turntable (216) and the triangular turntable (217) respectively. The variable stiffness drive rope (46) is tied to the bottom of the triangular turntable (217) and is connected to the drive assembly (4) for transmission. The circular turntable (216) has a circular torsion spring groove (216A), a circular through hole (216B), a circular threaded hole (216C), and a circular wire hole (216D); the triangular turntable (217) has a triangular wire hole (217A), a triangular torsion spring groove (217B), and a triangular through hole (217C); the torsion spring (215) is engaged in the circular torsion spring groove (216A) and the triangular torsion spring groove (217B); the joint connecting rod (214) has a connecting rod through hole (214B) and a clamping block mounting shaft (214A); the clamping block (213) has a light hole (213A) that mates with the clamping block mounting shaft (214A).

2. The adaptive manipulator based on rope-driven variable stiffness with rigid-flexible coupling according to claim 1, characterized in that, The mounting housing and adapter assembly (1) includes a robotic arm adapter (11), an upper mounting housing (12), a drive assembly mounting housing (13), a lower mounting housing (14), and a mounting base (15). The robotic arm adapter (11) is fitted with the shaft hole of the upper mounting housing (12) and connected by bolts. The upper mounting housing (12) is bolted to the lower mounting housing (14). The drive assembly mounting housing (13) is located inside the upper mounting housing (12). The lower mounting housing (14) is connected to the mounting base (15). The mounting base (15) is connected to the variable stiffness assembly (2) and the finger assembly (3) respectively.

3. The adaptive manipulator based on rope-driven variable stiffness with rigid-flexible coupling according to claim 2, characterized in that, The mounting housing (12) has a mounting shaft hole (12A), a wire hole (12B), a first through hole (12C), a second through hole (12D), and a third through hole (12E); the robotic arm adapter (11) is installed in the mounting shaft hole (12A) and is bolted in place through the second through hole (12D) and the third through hole (12E). The drive assembly mounting shell (13) has an internal drive first through hole (13A) for fixing the drive plate (41), a drive second through hole (13B) and a drive recessed through hole (13C) for mounting the servo motor (42), a wiring hole (13D) for arranging the servo motor cable connecting the servo motor (42) and the drive plate (41), and a drive third through hole (13E) for connecting the mounting lower shell (14); the drive second through hole (13B) is used for servo motor positioning, and the drive recessed through hole (13C) is used for bolt connection with the servo motor (42); The mounting base (15) has a first through hole (15A) for connecting the rope pulley (47), a second through hole (15B) for placing the air pipe connector, a recessed through hole (15C) for installing the finger assembly (3), a rope through hole (15E) for threading the variable stiffness drive rope (46), and a third through hole (15D) for connecting the mounting lower shell (14); the mounting base (15) is equipped with the rope pulley (47).

4. The adaptive manipulator based on rope-driven variable stiffness with rigid-flexible coupling according to claim 3, characterized in that, The drive assembly (4) includes a drive plate (41), a servo motor (42), a servo motor adapter (43), a cable fixing disc (44), and an internal hexagon head screw (45). The drive plate (41) is fixed inside the column of the drive assembly mounting shell (13) at the drive first through hole (13A). The servo motor (42) is fixed on the drive assembly mounting shell (13) through the drive second through hole (13B) and the drive recessed through hole (13C). The cable fixing disc (44) is connected to the servo motor (42) through the servo motor adapter (43) and fixed by the internal hexagon head screw (45). A variable stiffness drive cable (46) is wound on the cable fixing disc (44). The variable stiffness drive cable (46) passes through the cable guide hole (15E) and the cable pulley (47) of the mounting base (15) and is connected to the variable stiffness assembly (2).

5. The adaptive manipulator based on rope-driven variable stiffness with rigid-flexible coupling according to claim 1, characterized in that, The lower connecting rod (22) has a lower connecting rod threaded hole (22A) and a lower connecting rod mounting shaft (22C); the middle connecting rod (23) has a middle connecting rod first threaded hole (23A), a middle connecting rod second threaded hole (23C) and a middle connecting rod through hole (23B) for wiring; the upper connecting rod (24) has an upper connecting rod first threaded hole (24A), an upper connecting rod second threaded hole (24B), a wire through hole (24C) and an upper connecting rod mounting shaft (24D).

6. The adaptive manipulator based on rope-driven variable stiffness with rigid-flexible coupling according to claim 1, characterized in that, The finger assembly (3) includes a soft finger (31), a finger connector (32), an air tube connector (33), and a countersunk screw (34). The soft finger (31) is connected to the finger connector (32). The air tube connector (33) passes through the air tube mounting through hole (32C) of the finger connector (32) and the second through hole (15B) of the base of the mounting base (15). The finger connector (32) is fixed to the base recessed through hole (15C) of the mounting base (15) by the countersunk screw (34). The finger connector (32) has a first through hole (32A), a second through hole (32B), and an air tube mounting through hole (32C).

7. The rope-driven variable stiffness rigid-flexible coupling adaptive manipulator according to claim 6, characterized in that, The soft finger (31) includes a soft finger body (311) and a limiting layer (312). The soft finger body (311) has an air intake line (31A), a finger joint chamber (31B), and a variable stiffness joint mounting hole (31C) inside. The finger joint chamber (31B) is in the shape of a groove. The air intake line (31A) is connected to each finger joint chamber (31B). The limiting layer (312) is located in the middle of the bottom sealing layer of the soft finger body (311). The sealing layer is used to ensure the sealing of the soft finger body (311), and the bottom of the sealing layer is a silicone surface to improve the friction when grasping objects. The limiting layer (312) restricts the stretching of the bottom of the soft finger body (311) and guides the soft finger (31) to bend in a preset direction.

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