A variable stiffness two-degree-of-freedom flexible joint

Abstract

The application belongs to the technical field of robots, and discloses a two-degree-of-freedom flexible joint with variable rigidity, which comprises a mounting platform connected to a work platform or a base, a center column is arranged at the center of the surface of the mounting platform, a rotating platform is connected to the top of the center column, a plurality of rigidity adjusting mechanisms and identification modules are uniformly arranged between the rotating platform and the mounting platform; the rigidity adjusting mechanism comprises a driving unit which is uniformly arranged at the outer edge of the top of the mounting platform, an adjusting sliding block assembly is movably connected to the driving end of the driving unit, and the adjusting sliding block assembly is connected to the rotating platform through a flexible rod. The rigidity of the flexible joint can be flexibly changed through the rigidity adjusting mechanism. The driving unit drives the adjusting sliding block assembly to move, changes the stress state of the flexible rod, thereby realizing real-time adjustment of the rigidity, adapting to different contact force change scenes, and solving the problem that the traditional rigid mechanical arm cannot adapt to the change of the contact force.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a two-degree-of-freedom flexible joint with variable stiffness. Background Technology

[0002] A flexible joint is a mechanical connection device that achieves movement through the elastic deformation of materials or a flexible structure. Compared with traditional robotic arm joints, it does not require the use of traditional hinges, relying on the elasticity or geometric deformation of the material itself. It is suitable for scenarios involving interaction with humans or fragile objects and has great potential in fields such as biomedicine, aerospace, and biomimetic robotics.

[0003] Currently, traditional robotic arms with rigid structures rely on precise position control during assembly, making them unable to adapt to changes in contact force and lacking real-time force feedback. This can easily lead to damage to assembled parts or the robotic arm itself. Furthermore, collisions generate significant impact forces, potentially causing injury to people or equipment. Traditional robotic arms also lack end-effector flexibility and the ability to passively compensate for positional deviations and geometric errors in parts and fixtures, necessitating the deployment of high-precision fixtures to meet assembly requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a two-degree-of-freedom flexible joint with variable stiffness to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A variable stiffness two-degree-of-freedom flexible joint includes a mounting platform connected to a working platform or a base. A central column is provided at the center of the surface of the mounting platform, and a rotating platform is connected to the top of the central column. Multiple stiffness adjustment mechanisms and identification modules are also uniformly arranged between the rotating platform and the mounting platform.

[0007] The stiffness adjustment mechanism includes a drive unit evenly distributed at the top outer edge of the mounting platform. The drive end of the drive unit is movably connected to an adjustment slider assembly, which is also connected to the rotating platform via a flexible rod.

[0008] More preferably, the drive unit includes a plurality of connecting bases evenly arranged on the outer edge of the top of the mounting platform. Each connecting base is connected to a DC motor via a fixed base. The drive end of the DC motor is connected to a lower bevel gear through the surface of the fixed base. The lower bevel gear meshes with an upper bevel gear on the outer side of the connecting base. The other end of the upper bevel gear is connected to a lead screw through the connecting base. A sliding nut is fitted on the surface of the lead screw. A guide rail is symmetrically arranged at the bottom of the connecting base near the lead screw. The ends of the lead screw and the guide rails away from the connecting base are both connected to the surface of the central column.

[0009] More preferably, the adjusting slider assembly includes a stiffness adjusting slider and a sliding adjusting slider, which are fixedly connected by bolts. A rolling bearing is provided at the center of the surface of the stiffness adjusting slider, and a stepped hole and a sliding bearing are respectively provided on the surface of the sliding adjusting slider corresponding to the lead screw and the guide rail. A sliding nut is fixedly connected inside the stepped hole by a plurality of evenly arranged screws, and a guide rail is movably connected inside the sliding bearing.

[0010] More preferably, a flexible rod is connected through the inside of the rolling bearing. One end of the flexible rod is fixedly connected to a fixed block, and the other end of the flexible rod is fixedly connected to a central column. The fixed block is fixedly connected to the bottom of an L-shaped connecting block by bolts. The L-shaped connecting block is located at the bottom edge of the rotating platform, corresponding to the position of the stiffness adjustment mechanism.

[0011] More preferably, the rotating platform includes a moving platform, and a spring cavity is fixedly connected to the center of the bottom of the moving platform. The bottom end of the spring cavity is connected to the center of the top of the central column through a ball joint.

[0012] More preferably, the spring cavity includes an upper cavity that is fixedly connected to the center of the bottom of the moving platform by bolts. A damping spring is provided inside the upper cavity. A lower cavity is also provided at the bottom of the damping spring. One end of the lower cavity is fitted inside the upper cavity. A connecting gasket is fixedly connected to the bottom end of the upper cavity by bolts. The connecting gasket passes through the other end of the lower cavity.

[0013] More preferably, the central column includes a lower column disposed at the center of the surface of the mounting platform, an upper column connected to the top of the lower column, and a joint base disposed at the center of the surface of the upper column, the joint base being hinged to a ball joint.

[0014] More preferably, the mounting platform includes a fixed platform, the bottom of which is connected to a mounting washer by a plurality of evenly arranged screws, and a plurality of mounting studs are evenly distributed on the mounting washer, the mounting studs being screwed to the working platform or base.

[0015] More preferably, the identification module includes multiple visual sensing modules disposed on the surface of the fixed platform and multiple coded identification patches disposed on the bottom surface of the moving platform. The visual sensing modules and coded identification patches are disposed corresponding to each other, and the angle between the visual sensing modules and coded identification patches in the same longitudinal direction and the adjacent stiffness adjustment mechanism is 45°.

[0016] More preferably, the visual sensing module is composed of a Raspberry Pi camera module, and the visual sensing module is used to identify changes in the coded identification patch to determine the attitude of the moving platform.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The stiffness of the flexible joint can be flexibly changed through the stiffness adjustment mechanism. The drive unit moves the adjustment slider assembly, changing the force state of the flexible rod, thereby realizing real-time adjustment of stiffness. It can adapt to different scenarios with varying contact forces, solving the problem that traditional rigid robotic arms cannot adapt to changes in contact forces.

[0019] The rotating platform is connected to the central column via ball joints. Combined with the deformation of flexible rods, it can rotate in multiple directions and has two degrees of freedom of movement, which improves the flexibility of the joints and enhances the ability to work in complex environments.

[0020] The rotating platform has a spring cavity with shock-absorbing springs inside, which can effectively buffer the impact force when the joint moves or a collision occurs, reducing the risk of injury to people or equipment and overcoming the defect of large impact force when traditional robotic arms collide.

[0021] The visual sensing module in the recognition module can identify changes in the coded recognition patch, thereby accurately determining the posture of the moving platform, providing a basis for precise joint control and helping to improve operational accuracy.

[0022] The components are reliably connected and have a compact layout. The mounting platform is easy to connect to the work platform or base via mounting studs, and is easy to disassemble and maintain. It is suitable for applications in various fields such as biomedicine, aerospace, and bionic robots. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 This is an exploded view of the rotating platform structure of the present invention;

[0025] Figure 3 This is a schematic diagram of the structure of the driving unit of the present invention;

[0026] Figure 4 This is a schematic diagram of the structure of the adjusting slider assembly of the present invention;

[0027] Figure 5 This is a schematic diagram of the structure of the central column of the present invention;

[0028] In the diagram: 1. Rotating platform; 11. Moving platform; 12. L-shaped connecting block; 13. Spring cavity; 131. Upper cavity; 132. Lower cavity; 133. Connecting gasket; 14. Shock-absorbing spring; 15. Ball joint; 16. Fixing block; 21. Upper column; 22. Lower column; 23. Joint base; 3. Flexible rod; 411. Stiffness adjustment slider; 412. Sliding adjustment slider; 413. Sliding bearing; 414. Rolling bearing; 421. Lead screw; 422. Sliding nut; 423. Guide rail; 424. Upper bevel gear; 425. Lower bevel gear; 426. Fixed base; 427. Connecting base; 428. DC motor; 5. Mounting platform; 51. Fixed platform; 52. Mounting gasket; 53. Mounting stud; 61. Vision sensing module; 62. Encoding recognition patch; 7. Bolt; 8. Screw. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figures 1-5 The present invention provides a technical solution:

[0031] A variable stiffness two-degree-of-freedom flexible joint includes a mounting platform 5 connected to a working platform or a base. A central column is provided at the center of the surface of the mounting platform 5. A rotating platform 1 is connected to the top of the central column. Multiple stiffness adjustment mechanisms and identification modules are also evenly arranged between the rotating platform 1 and the mounting platform 5.

[0032] The stiffness adjustment mechanism includes drive units evenly distributed at the top outer edge of the mounting platform 5. The drive end of the drive unit is movably connected to an adjustment slider assembly, which is also connected to the rotating platform 1 via a flexible rod 3.

[0033] In this invention, the drive unit includes multiple connecting bases 427 evenly arranged on the outer edge of the top of the mounting platform 5. Each connecting base 427 is connected to a DC motor 428 via a fixed base 426. The drive end of the DC motor 428 passes through the surface of the fixed base 426 and is connected to a lower bevel gear 425. The lower bevel gear 425 and the upper bevel gear 424 on the outer side of the connecting base 427 are meshed with each other. The other end of the upper bevel gear 424 passes through the connecting base 427 and is connected to a lead screw 421. A sliding nut 422 is sleeved on the surface of the lead screw 421. A guide rail 423 is symmetrically arranged at the bottom of the end of the connecting base 427 near the lead screw 421. The ends of the lead screw 421 and the guide rail 423 away from the connecting base 427 are both connected to the surface of the central column. The adjusting slider assembly includes a stiffness adjusting slider 411 and a sliding adjusting slider 412, which are fixedly connected by bolts 7. A rolling bearing 414 is provided at the center of the surface of the stiffness adjusting slider 411. The surface of the sliding adjusting slider 412 is provided with stepped holes and sliding bearings 413 corresponding to the lead screw 421 and guide rail 423, respectively. A sliding nut 422 is fixedly connected inside the stepped hole by multiple evenly arranged screws 8. The guide rail 423 is movably connected inside the sliding bearing 413. A flexible rod 3 is connected through the rolling bearing 414. One end of the flexible rod 3 is fixedly connected to the fixed block 16, and the other end is fixedly connected to the central column. The fixed block 16 is fixedly connected to the bottom of the L-shaped connecting block 12 by bolts 7. The L-shaped connecting block 12 is located at the bottom edge of the rotating platform 1, corresponding to the position of the stiffness adjusting mechanism.

[0034] In this invention, the rotating platform 1 includes a moving platform 11, with a spring cavity 13 fixedly connected to the center of the bottom of the moving platform 11. The bottom end of the spring cavity 13 is connected to the center of the top of the central column via a ball joint 15. The spring cavity 13 includes an upper cavity 131 fixedly connected to the center of the bottom of the moving platform 11 via bolts 7. A damping spring 14 is provided inside the upper cavity 131, and a lower cavity 132 is provided at the bottom of the damping spring 14. One end of the lower cavity 132 is fitted inside the upper cavity 131, and a connecting gasket 133 is fixedly connected to the bottom end of the upper cavity 131 via bolts 7. The other end of the lower cavity 132 passes through the connecting gasket 133. The central column includes a lower column 22 located at the center of the surface of the mounting platform 5. An upper column 21 is connected to the top of the lower column 22, and a connector base 23 is provided at the center of the surface of the upper column 21. The connector base 23 is hinged to the ball joint 15.

[0035] In this invention, the mounting platform 5 includes a fixed platform 51. The bottom of the fixed platform 51 is connected to a mounting washer 52 by a plurality of screws 8 evenly arranged. A plurality of mounting studs 53 are evenly distributed on the mounting washer 52. The mounting studs 53 are screwed to the working platform or base.

[0036] In this invention, the identification module includes multiple visual sensing modules 61 disposed on the surface of the fixed platform 51 and multiple coded identification patches 62 disposed on the bottom surface of the moving platform 11. The visual sensing modules 61 and the coded identification patches 62 are arranged correspondingly to each other, and the angle between the visual sensing modules 61 and the coded identification patches 62 in the same longitudinal direction and the adjacent stiffness adjustment mechanism is 45°. The visual sensing modules 61 are constructed using Raspberry Pi camera modules, and the visual sensing modules 61 are used to identify changes in the coded identification patches 62 to determine the attitude of the moving platform 11.

[0037] Example: The fixed platform 51 of the mounting platform 5 is made of aluminum alloy and is fixed to the working platform by four mounting studs 53. The mounting pads 52 are made of rubber, which serves to cushion and prevent slipping. The lower column 22 and the upper column 21 of the central column are both made of stainless steel. The lower column 22 is fixed to the center of the surface of the fixed platform 51 by welding. The upper column 21 is connected to the lower column 22 by bolts 7. The connector base 23 is integrally formed with the upper column 21.

[0038] The moving platform 11 of the rotating platform 1 is also made of aluminum alloy. Four L-shaped connecting blocks 12 are fixed to the bottom edge of the moving platform 11 by bolts 7, evenly distributed around the perimeter of the moving platform 11. The upper cavity 131 and lower cavity 132 of the spring cavity 13 are both made of metal. The upper cavity 131 is fixed to the center of the bottom of the moving platform 11 by bolts 7. The damping spring 14 is a cylindrical helical spring made of high-strength spring steel. One end of the lower cavity 132 is fitted inside the upper cavity 131, and the other end is hinged to the connector base 23 via a ball joint 15. The connecting gasket 133 is made of copper to reduce wear between the lower cavity 132 and the upper cavity 131.

[0039] Four stiffness adjustment mechanisms are provided, evenly distributed along the outer edge of the top of the mounting platform 5. The connecting base 427 of the drive unit is fixed to the fixed platform 51 by bolts 7. The fixed base 426 is also fixedly connected to the connecting base 427 by bolts 7. The DC motor 428 is model DCX-16-S. The lower bevel gear 425 and the upper bevel gear 424 are both made of brass and mesh with each other for transmission. The lead screw 421 works in conjunction with the sliding nut 422. The guide rail 423 is a linear guide rail to ensure the smooth movement of the adjustment slider assembly.

[0040] The stiffness adjusting slider 411 and the sliding adjusting slider 412 of the adjusting slider assembly are both made of aluminum alloy and are fixedly connected by four bolts 7. The rolling bearing 414 is a deep groove ball bearing, the sliding bearing 413 is a linear bearing, and the sliding nut 422 is fixed in the stepped hole of the sliding adjusting slider 412 by three screws 8. The flexible rod 3 is made of ABS plastic or carbon fiber, which has high strength and elasticity. One end of the flexible rod 3 is fixed to the surface of the fixing block 16, and the fixing block 16 is fixed to the bottom of the L-shaped connecting block 12 by bolts 7. The other end of the flexible rod 3 is fixed to the surface of the upper column 21.

[0041] In the recognition module, the visual sensing module 61 uses a Raspberry Pi camera module, model RaspberryPi Camera v2, and a total of 4 are set up, evenly distributed on the surface of the fixed platform 51. The coding recognition patch 62 is a black and white QR code patch, which is set on the bottom surface of the moving platform 11 corresponding to the position of the visual sensing module 61. The angle between the visual sensing module 61 and the coding recognition patch 62 in the same longitudinal direction and the adjacent stiffness adjustment mechanism is 45°, ensuring that the visual sensing module 61 can clearly capture the image of the coding recognition patch 62.

[0042] When the variable stiffness two-degree-of-freedom flexible joint is in operation, if the joint stiffness needs to be changed, the DC motor 428 starts, driving the lower bevel gear 425 to rotate. The lower bevel gear 425 drives the upper bevel gear 424 to rotate, thereby rotating the lead screw 421. The sliding nut 422 moves on the lead screw 421, driving the adjusting slider assembly to move along the guide rail 423, thereby changing the bending degree and stress state of the flexible rod 3, and realizing the adjustment of stiffness. When the rotating platform 1 is subjected to external force, the moving platform 11 rotates through the ball joint 15. At the same time, the damping spring 14 is compressed or extended, playing a buffering role. The vision sensing module 61 captures the coded recognition patch 62 in real time and transmits the image information to the control system. The control system judges the posture of the moving platform 11 based on the image changes, thereby realizing precise control of the joint.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A variable stiffness two-degree-of-freedom flexible joint, comprising a mounting platform (5) connected to a working platform or a base, characterized in that: A central column is provided at the center of the surface of the installation platform (5), and a rotating platform (1) is connected to the top of the central column. Multiple stiffness adjustment mechanisms and identification modules are also evenly arranged between the rotating platform (1) and the installation platform (5). The stiffness adjustment mechanism includes a drive unit evenly arranged on the top outer edge of the mounting platform (5). The drive end of the drive unit is movably connected to an adjustment slider assembly. The adjustment slider assembly is also connected to the rotating platform (1) through a flexible rod (3). The drive unit includes multiple connecting bases (427) evenly arranged on the outer edge of the top of the mounting platform (5). Each connecting base (427) is connected to a DC motor (428) via a fixed base (426). The drive end of the DC motor (428) passes through the surface of the fixed base (426) and is connected to a lower bevel gear (425). The lower bevel gear (425) meshes with an upper bevel gear (424) on the outer side of the connecting base (427). The other end of the upper bevel gear (424) passes through the connecting base (427) and is connected to a lead screw (421). A sliding nut (422) is sleeved on the surface of the lead screw (421). A guide rail (423) is symmetrically arranged at the bottom of the connecting base (427) near the lead screw (421). The ends of the lead screw (421) and the guide rail (423) away from the connecting base (427) are both connected to the surface of the central column. The adjusting slider assembly includes a stiffness adjusting slider (411) and a sliding adjusting slider (412). The stiffness adjusting slider (411) and the sliding adjusting slider (412) are fixedly connected by bolts (7). A rolling bearing (414) is provided at the center of the surface of the stiffness adjusting slider (411). The surface of the sliding adjusting slider (412) is provided with a stepped hole and a sliding bearing (413) respectively corresponding to the lead screw (421) and the guide rail (423). A sliding nut (422) is fixedly connected inside the stepped hole by a plurality of evenly arranged screws (8). The guide rail (423) is movably connected inside the sliding bearing (413).

2. The variable stiffness two-degree-of-freedom flexible joint according to claim 1, characterized in that: The rolling bearing (414) has a flexible rod (3) that runs through it. One end of the flexible rod (3) is fixedly connected to the fixed block (16), and the other end of the flexible rod (3) is fixedly connected to the central column. The fixed block (16) is fixedly connected to the bottom of the L-shaped connecting block (12) by bolts (7). The L-shaped connecting block (12) is located at the bottom edge of the rotating platform (1) corresponding to the position of the stiffness adjustment mechanism.

3. A variable stiffness two-degree-of-freedom flexible joint according to claim 1, characterized in that: The rotating platform (1) includes a moving platform (11), and a spring cavity (13) is fixedly connected at the bottom center of the moving platform (11). The bottom end of the spring cavity (13) is connected to the top center of the central column through a ball joint (15).

4. A variable stiffness two-degree-of-freedom flexible joint according to claim 3, characterized in that: The spring cavity (13) includes an upper cavity (131) fixedly connected to the center of the bottom of the moving platform (11) by bolts (7). A damping spring (14) is provided inside the upper cavity (131). A lower cavity (132) is also provided at the bottom of the damping spring (14). One end of the lower cavity (132) is sleeved inside the upper cavity (131), and a connecting gasket (133) is fixedly connected to the bottom end of the upper cavity (131) by bolts (7). The other end of the lower cavity (132) is provided through the connecting gasket (133).

5. A variable stiffness two-degree-of-freedom flexible joint according to claim 3, characterized in that: The central column includes a lower column (22) located at the center of the surface of the mounting platform (5), an upper column (21) connected to the top of the lower column (22), a connector base (23) located at the center of the surface of the upper column (21), and the connector base (23) hinged to the ball joint (15).

6. A variable stiffness two-degree-of-freedom flexible joint according to claim 5, characterized in that: The installation platform (5) includes a fixed platform (51). The bottom of the fixed platform (51) is connected to an installation washer (52) by a plurality of screws (8) evenly arranged. A plurality of installation studs (53) are evenly distributed on the installation washer (52). The installation studs (53) are screwed to the working platform or base.

7. A variable stiffness two-degree-of-freedom flexible joint according to claim 6, characterized in that: The identification module includes multiple visual sensing modules (61) disposed on the surface of the fixed platform (51) and multiple coded identification patches (62) disposed on the bottom surface of the moving platform (11). The visual sensing modules (61) and the coded identification patches (62) are disposed corresponding to each other. The angle between the visual sensing modules (61) and the coded identification patches (62) in the same longitudinal direction and the adjacent stiffness adjustment mechanism is 45°.

8. A variable stiffness two-degree-of-freedom flexible joint according to claim 7, characterized in that: The visual sensing module (61) is composed of a Raspberry Pi camera module. The visual sensing module (61) is used to identify changes in the coded identification patch (62) to determine the posture of the moving platform (11).

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