A variable stiffness joint structure for an underwater flexible robotic finger

Abstract

The application relates to the technical field of nuclear industry robots, and particularly discloses a variable-rigidity joint structure of an underwater flexible mechanical finger. The joint structure comprises multiple joints and a support, the joints are connected through the support, low-melting-point metal is filled and sealed in the joints, the low-melting-point metal is melted and solidified in a heating and cooling mode, and then the rigidity of the joints is changed. The joint structure is ingenious in design, reliable in performance, and can effectively improve the underwater operation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of nuclear industry robot technology, specifically relating to a variable stiffness joint structure for an underwater flexible mechanical finger. Background Technology

[0002] There are many types of existing methods for varying the stiffness of robotic arms, and different driving methods can produce different effects.

[0003] Electric motor, pneumatic, or hydraulic drive methods work by using a motor in conjunction with a rigid spring to change the stiffness of finger joints, or by using high and low pressure differences created by pneumatic or hydraulic pressure to change the stiffness of soft mechanisms. However, electric motor, pneumatic, and hydraulic drive methods for changing stiffness have problems such as large size, complex structure, and noise.

[0004] Shape memory polymers, low-melting-point metals, and paraffin wax, among other phase change materials, can also achieve variable stiffness joints. The principle is to utilize the change in the elastic modulus of low-melting-point metals or shape memory materials during heating and cooling to alter the stiffness of the robotic hand joints. Compared to motor-driven or pneumatic / hydraulic-driven variable stiffness joints, this method simplifies the stiffness structure of finger joints, reduces joint mass, and is noiseless. However, because the elastic modulus of materials like shape memory polymers and paraffin wax changes only slightly with temperature, the range of joint stiffness variation is narrow. Furthermore, most variable stiffness fingers are not suitable for underwater operation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a variable stiffness joint structure for an underwater flexible mechanical finger, thereby solving the problems of lightweighting the mechanical finger joint structure, increasing the range of joint variable stiffness, and adapting the mechanical finger to the underwater working environment.

[0006] To solve the above problems, the technical solution of the present invention is as follows: a variable stiffness joint structure for an underwater flexible mechanical finger, comprising multiple joints and a support, wherein the joints are connected by the support, and the joints are filled and sealed with low melting point metal, and the low melting point metal is melted and solidified by heating and cooling, thereby changing the stiffness of the joint.

[0007] The joint includes a first joint, a second joint, and a third joint. The fingertip, the first joint, the second joint, the third joint, and the finger root are arranged in order from top to bottom. Each part is connected in series by a superelastic alloy (3) to achieve support and bending rebound of the entire joint structure.

[0008] The fingertip, the first joint, and the middle of the second joint are connected in series by a rope. The fingertip has a rope fixing hole to fix one end of the rope. The second joint, the third joint, and the base of the finger are connected in series by a shape memory alloy spring. The base of the finger has a spring fixing hole to fix one end of the shape memory alloy spring. The non-fixed end of the rope is connected to the non-fixed end of the shape memory alloy spring to control the bending deformation of the three joints.

[0009] The first joint includes a bearing, a cylindrical base, and a shaft. The middle part of the first joint is a cylindrical base, and the lower end of the cylindrical base is provided with a transverse cylindrical cavity. The shaft is horizontally disposed in the cylindrical cavity. The middle of the shaft is a cuboid structure with a threaded groove. The two ends of the shaft are provided with shaft threads, and the two ends of the shaft are also fitted with bearings.

[0010] There is a gap between the cylindrical base and the shaft on the inner wall of the cylindrical cavity, and the gap between the cylindrical base and the shaft is filled with a low-melting-point metal.

[0011] A heating wire is wound around the threaded groove of the shaft.

[0012] The bearing is fixed by a bearing bracket, which is an open ring structure. A retaining ring is provided on the outer side of the ring to prevent the bearing from falling out. A groove is provided on the inner side of the ring of the bearing bracket to connect with the cylindrical base. The bearing is fixed between the retaining ring and the cylindrical base to prevent the bearing from axial displacement during rotation.

[0013] The bearing bracket has an M3 threaded hole at the opening, and the opening is clamped by bearing fixing bolts, thereby clamping the bearing inside the bearing bracket.

[0014] The bearing bracket and the cylindrical base are fixedly connected by bolts.

[0015] The bearing bracket is equipped with a limiting frame at its lower end.

[0016] The cylindrical base has two symmetrical cylindrical base through holes on the front side of the cylindrical cavity, so that the two ends of the heating wire can be extended out from the two cylindrical base through holes.

[0017] A first joint bracket is provided below the cylindrical base. The first joint bracket is U-shaped and includes a large first joint connecting bracket and a small first joint connecting bracket. The large first joint connecting bracket has a screw hole at its left end for connection with the small first joint connecting bracket, and a first coupling hole at its right end for the right end thread of the shaft to pass through. A crossbeam is provided in the middle of the large first joint connecting bracket to enhance the lateral support of the large first joint connecting bracket. At the same time, when the joint rotates in the opposite direction, the limiting bracket is blocked by the crossbeam of the large joint connecting bracket to ensure that the joint can only bend and deform on one side. The small first joint connecting bracket has a first coupling hole at its top for the left end thread of the shaft to pass through. The large first joint connecting bracket has a connecting part at its bottom and is connected to the bearing bracket of the second joint by bolts.

[0018] The second joint includes a second joint support, the lower end of which is fixedly connected to the third cylindrical base of the third joint.

[0019] The shaft is equipped with silicone gaskets at both ends to seal the low-melting-point metal.

[0020] The low-melting-point metal is a tin-bismuth alloy.

[0021] The base of the finger root is provided with a finger root fixing hole.

[0022] The superelastic alloy consists of two strands, connected in series from the fingertip, the first joint, the second joint, the third joint, and the finger root on both sides.

[0023] The significant advantage of this invention lies in the variable stiffness joint structure of the underwater flexible mechanical finger. By heating and cooling the low-melting-point metal in the joint, the stiffness of the joint is altered, thereby enabling the finger to grasp heavier objects. This joint structure is ingeniously designed, reliable in performance, and effectively improves underwater operation efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the variable stiffness joint structure of an underwater flexible mechanical finger according to the present invention.

[0025] Figure 2 This is an exploded view of the first joint in the variable stiffness joint structure of an underwater flexible mechanical finger according to the present invention.

[0026] Figure 3 This is a schematic diagram of a bearing support for a variable stiffness joint structure of an underwater flexible mechanical finger according to the present invention.

[0027] Figure 4 This is a schematic diagram of the assembly of the shaft, heating wire, and cylindrical base of the variable stiffness joint structure of the underwater flexible mechanical finger described in this invention.

[0028] Figure 5 This is an assembly diagram of the first joint of a variable stiffness joint structure for an underwater flexible mechanical finger according to the present invention.

[0029] Figure 6 This is an assembly diagram of the second joint of a variable stiffness joint structure for an underwater flexible mechanical finger according to the present invention.

[0030] Figure 7 This is an assembly diagram of the third joint of a variable stiffness joint structure for an underwater flexible mechanical finger according to the present invention.

[0031] In the diagram: 1. Fingertip; 2. Rope; 3. Hyperelastic alloy; 4. Shape memory alloy spring; 5. First joint; 6. Second joint; 7. Third joint; 8. Finger root; 9. Bearing bracket; 10. Bearing; 11. Cylindrical base; 12. Silicone gasket; 13. Bearing fixing bolt; 14. Bolt connecting the bearing bracket and the cylindrical base; 15. Large bracket connecting the first joint; 16. Heating wire; 17. Shaft; 18. Small bracket connecting the first joint; 19. Bracket connecting bolt; 20. 21. M3 threaded hole; 22. First M2 threaded hole; 23. Retaining ring; 24. Groove; 25. Limiting bracket; 26. Rope fixing hole; 27. Rope through hole; 28. Shaft thread; 29. ​​Second M2 threaded hole; 30. Clearance between cylindrical base and shaft; 31. Cylindrical base through hole; 32. Crossbeam; 33. Second coupling hole; 34. Superelastic alloy through hole; 35. Square hole; 36. Spring fixing hole; 37. Finger root fixing hole; 38. Superelastic alloy fixing hole; 39. Third coupling hole. Detailed Implementation

[0032] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0033] In the description of this invention, it should be noted that the use of terms such as "above" to indicate orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings and is only for the purpose of facilitating and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0034] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] like Figure 1-7 As shown, a variable stiffness joint structure for an underwater flexible mechanical finger includes a variable stiffness joint, a fingertip 1, and a finger root 8. The variable stiffness joint comprises a first joint 5, a second joint 6, and a third joint 7. The three joints have similar internal structures and can perform various complex movements. The fingertip 1, first joint 5, second joint 6, third joint 7, and finger root 8 are arranged sequentially from top to bottom, and each part is connected in series by a superelastic alloy 3 to achieve support and bending resilience of the entire joint structure. In one embodiment, the number of superelastic alloy 3 is two, connected in series from both sides of the fingertip 1, first joint 5, second joint 6, third joint 7, and finger root 8.

[0037] The fingertip 1, the first joint 5, and the second joint 6 are connected in series via a rope 2. The fingertip 1 has a rope fixing hole 25 to fix one end of the rope 2. The second joint 6, the third joint 7, and the finger root 8 are connected in series via a shape memory alloy spring 4. The finger root 8 has a spring fixing hole 35 to fix one end of the shape memory alloy spring 4. The non-fixed end of the rope 2 is connected to the non-fixed end of the shape memory alloy spring 4 to control the bending deformation of the three joints. The bottom of the finger root 8 has a finger root fixing hole 36 to facilitate the connection of this joint structure with other structures (such as a robotic arm).

[0038] The first joint 5 includes a bearing bracket 9, a bearing 10, a cylindrical base 11, a silicone gasket 12, a large joint connecting bracket 15, a small joint connecting bracket 18, a heating wire 16, and a shaft 17. The first joint 5 has a cylindrical base 11 in the middle, and a transverse cylindrical cavity is provided at the lower end of the cylindrical base 11. The shaft 17 is horizontally disposed in the cylindrical cavity. The two ends of the shaft 17 are respectively provided with shaft threads 27, and the length of the shaft threads 27 is 3mm. The middle of the shaft 17 is a cuboid structure with a threaded groove, and the heating wire 16 is wound on the threaded groove. There is a gap 29 between the shaft 17 and the inner wall of the cylindrical cavity, and the gap 29 between the cylindrical base and the shaft is filled with a low melting point metal. As an example, the low melting point metal is a tin-bismuth alloy. When the low melting point metal filled in the gap 29 between the cylindrical base and the shaft is melted by the heating wire 16, the joint is in a low stiffness state and can rotate freely. When the heating wire 16 is de-energized, the metal cools and solidifies, causing the shaft 27 to connect with the cylindrical base 11. The joint is in a high-rigidity state and cannot rotate. Silicone gaskets 12 are provided at both ends of the shaft 17 to seal the low-melting-point metal. Bearings 10 are also sleeved at both ends of the shaft 17 and fixed by bearing brackets 9.

[0039] The bearing bracket 9 has an overall open ring structure. A retaining ring 22 is provided on the outer side of the ring to prevent the bearing 10 from falling out. A groove 23 is provided on the inner side of the ring of the bearing bracket 9 to connect with the cylindrical base 11. The bearing 10 is fixed between the retaining ring 22 and the cylindrical base 11 to prevent the bearing 10 from axially displacing during rotation. An M3 threaded hole 20 is provided at the opening of the bearing bracket 9. The opening is clamped by the bearing fixing bolt 13, thereby clamping the bearing 10 inside the bearing bracket 9. The upper and lower ends of the bearing bracket 9 are also provided with first M2 threaded holes 21. A limiting bracket 24 is provided at the lower part of the bearing bracket 9.

[0040] The cylindrical base 11 has a rope through hole 26 on the outer wall of the front side of the cylindrical cavity for the rope 2 to pass through; the cylindrical base 11 has two symmetrical cylindrical base through holes 30 on the front side of the cylindrical cavity, and the heating wire 16 extends from the two cylindrical base through holes 30 at both ends and is connected to the power supply through a cable; the upper and lower ends of the cylindrical cavity of the cylindrical base 11 are respectively provided with second M2 threaded holes 28, the second M2 threaded holes 28 and the first M2 threaded holes 21 are corresponding in position, and the bearing bracket and cylindrical base connecting bolt 14 are screwed into the first M2 threaded holes 21 and the second M2 threaded holes 28, so that the bearing bracket 9 is fixedly connected to the cylindrical base 11;

[0041] The cylindrical base 11 is provided with a first joint bracket below it. The first joint bracket is U-shaped and includes a first joint connecting large bracket 15 and a first joint connecting small bracket 18. The first joint connecting large bracket 15 has a screw hole at its left end for connection with the first joint connecting small bracket 18, and a first coupling hole at its right end for the right end thread 27 of the shaft 17 to pass through. The first joint connecting large bracket 15 also has a protruding plate at its right end, and a first superelastic alloy hole on the plate for the superelastic alloy 3 to pass through. A crossbeam 31 is provided in the middle of the first joint connecting large bracket 15 to strengthen the lateral support of the first joint connecting large bracket 15. At the same time, when the joint rotates in the opposite direction, the limiting frame 24 is blocked by the crossbeam of the joint connecting large bracket 15 to ensure that the joint can only bend and deform on one side.

[0042] The first joint connecting large bracket 15 is also provided with a first bracket rope hole in the lower part for passing through the rope 2; the first joint connecting small bracket 18 is connected to the first joint connecting large bracket 15 through a bracket connecting bolt 19, and the first joint connecting small bracket 18 is provided with a first superelastic alloy hole in the middle for passing through the superelastic alloy 3; the first joint connecting small bracket 18 is provided with a first coupling hole at the top for passing through the left end shaft thread 27 of the shaft 17; the first joint connecting large bracket 15 is provided with a connecting part at the bottom and is connected to the bearing bracket of the second joint 6 through bolts;

[0043] The structure of the second joint 6 is similar to that of the first joint 5, except that it includes a second joint bracket. The second joint bracket has second connecting holes 32 at both ends to allow the second joint shaft to pass through. The second joint bracket also has superelastic alloy through holes 33 at both ends to allow the superelastic alloy 3 to pass through. The second joint bracket has a square hole 34 in the middle to allow the shape memory alloy spring 4 to pass through. The lower end of the second joint bracket is fixedly connected to the third cylindrical base of the third joint 7.

[0044] The structure of the third joint 7 is similar to that of the first joint 5, except that it includes a third joint bracket. The third joint bracket has third connecting holes 38 at both ends to allow the third joint shaft to pass through. The third joint bracket also has superelastic alloy fixing holes 37 at both ends to fix one end of the superelastic alloy 3.

[0045] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A variable stiffness joint structure for an underwater flexible mechanical finger, characterized in that: It includes multiple joints, supports, fingertips (1), and finger roots (8). The joints are connected by supports. The joints are filled and sealed with low-melting-point metal, and the low-melting-point metal is melted and solidified by heating and cooling, thereby changing the stiffness of the joint. The joints include a first joint (5), a second joint (6), and a third joint (7). The fingertip (1), the first joint (5), and the second joint (6) are connected in series by a rope (2). The fingertip (1) has a rope fixing hole (25) to fix one end of the rope (2). The second joint (6), the third joint (7), and the finger root (8) are connected in series by a shape memory alloy spring (4). The finger root (8) has a spring fixing hole (35) to fix one end of the shape memory alloy spring (4). The non-fixed end of the rope (2) is connected to the non-fixed end of the shape memory alloy spring (4) to control the bending deformation of the three joints. The first joint (5) includes a bearing. (10) Cylindrical base (11) and shaft (17). The middle part of the first joint (5) is a cylindrical base (11). The lower end of the cylindrical base (11) is provided with a transverse cylindrical cavity. The shaft (17) is horizontally arranged in the cylindrical cavity. The middle of the shaft (17) is a cuboid structure with a threaded groove. The two ends of the shaft (17) are provided with shaft threads (27). The two ends of the shaft (17) are also fitted with bearings (10). There is a gap (29) between the shaft (17) and the inner wall of the cylindrical cavity. The gap (29) between the cylindrical base and the shaft is filled with low melting point metal. A heating wire (16) is wound on the threaded groove of the shaft (17).

2. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 1, characterized in that: The first joint (5), the second joint (6), the third joint (7) and the finger root (8) are arranged from top to bottom, and each part is connected in series by a superelastic alloy (3) to achieve the support and bending springback of the entire joint structure.

3. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 1, characterized in that: The bearing (10) is fixed by the bearing bracket (9). The bearing bracket (9) is an open ring structure. A retaining ring (22) is provided on the outer side of the ring to prevent the bearing (10) from falling out. A groove (23) is provided on the inner side of the ring of the bearing bracket (9) to connect with the cylindrical base (11). The bearing (10) is fixed between the retaining ring (22) and the cylindrical base (11) to prevent the bearing (10) from axially displacing during rotation.

4. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 3, characterized in that: The bearing bracket (9) has an M3 threaded hole (20) at the opening. The opening is clamped by the bearing fixing bolt (13), thereby clamping the bearing (10) inside the bearing bracket (9).

5. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 3, characterized in that: The bearing bracket (9) and the cylindrical base (11) are fixedly connected by bolts.

6. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 3, characterized in that: The bearing bracket (9) is provided with a limiting bracket (24) at its lower end.

7. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 3, characterized in that: The cylindrical base (11) has two symmetrical cylindrical base through holes (30) on the front side of the cylindrical cavity, so that the two ends of the heating wire (16) can be protruded from the two cylindrical base through holes (30).

8. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 3, characterized in that: The cylindrical base (11) is provided with a first joint bracket below it. The first joint bracket is U-shaped and includes a first joint connecting large bracket (15) and a first joint connecting small bracket (18). The first joint connecting large bracket (15) has a screw hole at the left end to connect with the first joint connecting small bracket (18), and a first coupling hole at the right end to pass through the right end shaft thread (27) of the shaft (17). The first joint connecting large bracket (15) has a crossbeam (31) in the middle to strengthen the lateral support of the first joint connecting large bracket (15). At the same time, when the joint rotates in the opposite direction, the limit frame (24) is blocked by the crossbeam of the joint connecting large bracket (15) to ensure that the joint can only bend and deform on one side. The first joint connecting small bracket (18) has a first coupling hole at the top to pass through the left end shaft thread (27) of the shaft (17). The first joint connecting large bracket (15) has a connecting part at the bottom and is connected to the bearing bracket of the second joint (6) by bolts.

9. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 1, characterized in that: The second joint (6) includes a second joint bracket, the lower end of which is fixedly connected to the third cylindrical base of the third joint (7).

10. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 1, characterized in that: The shaft (17) is provided with silicone gaskets (12) at both ends to seal the low melting point metal.

11. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 5, characterized in that: The low-melting-point metal is a tin-bismuth alloy.

12. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 1, characterized in that: The finger root (8) has a finger root fixing hole (36) at its bottom.

13. The variable stiffness joint structure of an underwater flexible mechanical finger according to claim 2, characterized in that: The number of the superelastic alloy (3) is two, which are connected in series from both sides of the fingertip (1), the first joint (5), the second joint (6), the third joint (7) and the finger root (8).

Images