A variable stiffness structure for a continuum robotic arm

Abstract

This disclosure discloses a variable stiffness structure for a continuum robotic arm, comprising: a structural body disposed outside the continuum robotic arm and wrapping the outer surface of the continuum robotic arm; a hollow structure within the structural body that adjusts the stiffness of the continuum robotic arm based on changes in pressure within the hollow structure. This disclosure utilizes negative pressure to achieve variable stiffness, offering improved safety compared to using electrorheological or thermorheological fluids.

Description

Technical Field

[0001] The present disclosure belongs to the field of robotics technology, and particularly relates to a variable stiffness structure for a continuum robotic arm. Background Art

[0002] As a new type of biomimetic robot, the continuum robot can adapt to unstructured, confined spaces by flexibly changing its shape. Thanks to its superior compliance and flexibility, the continuum robot is widely used in fields such as pipeline inspection, post-earthquake search and rescue, and aircraft engine maintenance.

[0003] On the other hand, the superior compliance of continuum robots also leads to insufficient stiffness. Unlike the rigid links of traditional industrial robots, their flexible links are often susceptible to yielding deformation due to factors such as their own gravity, cable drive forces, and external loads, which seriously affects their kinematic reliability and positioning accuracy. Although some continuum robots with universal joints have improved their stiffness to a certain extent, their rigid links also lead to insufficient compliance. Their large size makes them difficult to adapt to confined spaces, especially around narrow corners. These continuum robots have poor adaptability to unstructured environments. While continuum robots with flexible rods as joints exhibit excellent compliance, this comes at the expense of their stiffness. Some common variable stiffness methods, such as those based on active materials (magnetorheological fluids, electrorheological fluids, and thermorheological fluids) and phase change materials, often have long activation times, relatively limited stiffness after activation, and more complex system designs. Therefore, how to make the continuum robot have the ability to quickly respond to stiffness control and relatively good stiffness effect without sacrificing its own flexibility is a challenging task.

[0004] Therefore, those skilled in the art are committed to proposing a variable stiffness structure design of a wire-driven continuum robot and a system thereof, which can ensure the stiffness performance of the continuum robot without sacrificing its compliance. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present disclosure aims to provide a variable stiffness structure for a continuum robotic arm, which can adjust the stiffness state of the continuum robot so that it has both flexibility and high rigidity.

[0006] To achieve the above objectives, the present disclosure provides the following technical solutions:

[0007] A variable stiffness structure for a continuum robotic arm, comprising:

[0008] A structural body, wherein the structural body is arranged on the outside of the continuum robot arm and wraps the outer surface of the continuum robot arm;

[0009] The structure body is a hollow structure, and the structure body adjusts the stiffness of the continuum robot arm according to the change of the pressure in the hollow structure.

[0010] Preferably, a variable stiffness medium is provided in the structural body.

[0011] Preferably, the variable stiffness medium includes a particle damping medium or a friction interference layer medium.

[0012] Preferably, the variable stiffness structure further includes a vacuum pump.

[0013] Preferably, the continuum robotic arm includes a plurality of continuum robotic arm structural units with the same structure.

[0014] Preferably, each continuum robotic arm structure unit comprises a metal ring.

[0015] Preferably, blind holes are provided on both the upper surface and the lower surface of the metal ring, and flexible rods are inserted into the blind holes.

[0016] Preferably, both the upper surface and the lower surface of the metal ring are provided with beveled groove surfaces.

[0017] Preferably, earrings are symmetrically arranged on the upper surface of the metal ring, and miniature bearings are arranged on the outer sides of the earrings.

[0018] Preferably, grooves are evenly arranged on the side surfaces of the metal ring.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention adopts negative pressure to achieve variable stiffness, which is safer than using electrorheological fluid or thermorheological fluid.

[0021] 2. The present invention adopts a negative pressure method to achieve variable stiffness, which has a faster activation response time for variable stiffness and a faster stiffness recovery time;

[0022] 3. The variable stiffness system disclosed in the present invention is universally applicable to linearly driven continua. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic planar structural diagram of a variable stiffness system provided by another embodiment of the present disclosure;

[0024] Figure 2 is a schematic diagram of a three-dimensional structure of a variable stiffness system provided by another embodiment of the present disclosure;

[0025] Figure 3is a structural schematic diagram of a continuum robotic arm provided by another embodiment of the present disclosure;

[0026] The following are the descriptions of the reference numerals:

[0027] 1. Variable stiffness structure; 2. Structural body; 3. Variable stiffness medium; 4. Vacuum pump; 5. Catheter; 6. Continuum robot arm; 7. Continuum robot arm structural unit; 8. Set screw; 9. Flexible rod; 10. Pin; 11. Miniature bearing; 12. Weight-reducing bevel groove; 13. Arc-shaped bevel groove; 14. Bevel groove surface; 15. Earring; 16. Groove. DETAILED DESCRIPTION

[0028] The following will refer to the attached Figures 1 to 3 Specific embodiments of the present disclosure are described in detail. Although specific embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0029] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present disclosure, but the description is based on the general principles of the specification and is not used to limit the scope of the present disclosure. The scope of protection of the present disclosure shall be as defined by the attached claims.

[0030] To facilitate understanding of the embodiments of the present disclosure, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and the accompanying drawings do not constitute a limitation on the embodiments of the present disclosure.

[0031] In one embodiment, if Figure 1 、 Figure 2 As shown, the present disclosure provides a variable stiffness structure for a continuum robotic arm, the variable stiffness structure 1 comprising:

[0032] The structural body 2 is arranged on the outside of the continuum robot arm 6 and wraps the outer surface of the continuum robot arm;

[0033] The structure body 2 is a hollow structure, and the structure body 2 adjusts the stiffness of the continuum robot arm 6 according to the change of the pressure in the hollow structure.

[0034] In this embodiment, the structural body 2 is made of silicone material and is connected to an external vacuum pump 4 via a conduit 5. The vacuum pump 4 evacuates the structural body of a certain volume through the conduit 5, reducing the pressure within the structural body. A variable stiffness medium 3 is provided within the structural body. When the internal pressure of the structural body decreases, the variable stiffness medium produces a clustering effect under the action of negative pressure, i.e., the friction between the variable stiffness mediums increases, thereby imparting a high stiffness to the structural body 2. Furthermore, since the structural body is wrapped around the continuum robotic arm 6, it exerts a restraining effect on the continuum robotic arm 6, thereby achieving a high stiffness state for the continuum robotic arm 6. When the vacuum pump releases the negative pressure, the internal pressure of the structural body increases, causing the variable stiffness medium to release the clustering effect, i.e., the friction between the variable stiffness mediums correspondingly decreases, thereby decreasing the stiffness of the structural body, thereby transforming the continuum robotic arm 6 into a low stiffness state. It can be seen that by adjusting the pressure inside the structural body through the vacuum pump, the stiffness state of the continuum robot arm 6 can be adjusted according to actual needs, so that the continuum robot arm has both flexibility and high rigidity.

[0035] Furthermore, this structure has better safety than the existing use of electrorheological fluid and thermorheological fluid. The reason is that due to the metal structure design of the continuum robot, the medium wrapping the electrorheological fluid and thermorheological fluid may rupture during the bending deformation process, resulting in hidden dangers such as leakage and leakage, thereby causing damage to the operator.

[0036] Furthermore, this structure achieves faster activation response time and stiffness recovery time compared to existing methods. For example, thermorheological fluid is heated by a heating wire to a certain temperature, achieving stiffness change. This process takes about 1-3 minutes; however, the recovery time can be as long as 10 to 30 minutes because the liquid, which is as high as 60°C, needs to cool naturally. This process is usually quite long. However, this structure achieves stiffness change by using negative pressure, and the activation response and stiffness recovery can be completed in just a dozen seconds.

[0037] In another embodiment, the variable stiffness medium 3 includes a particle damping medium material or a friction interference layer medium material.

[0038] In this embodiment, the particle damping dielectric material includes spherical polystyrene, lightweight glass spheres, etc.; the friction interference layer dielectric material includes a plastic film layer.

[0039] In another embodiment, Figure 3 As shown, the continuum robot arm 6 includes a plurality of continuum robot arm structural units 7 with the same structure.

[0040] In this embodiment, each continuum robotic arm structural unit includes a metal ring, and blind holes are provided on the upper and lower surfaces of the metal ring. Flexible rods 9 are inserted into the blind holes to connect two adjacent metal rings. The blind holes on the upper surface of the metal are arranged alternately with the blind holes on the lower surface, and the connecting line between the two symmetrically arranged blind holes on the upper surface is perpendicular to the connecting line between the two symmetrically arranged blind holes on the lower surface. Superelastic nickel-titanium memory alloy flexible rods are inserted into the blind holes to fix adjacent metal rings. In addition, threaded holes are respectively provided on the four cylindrical side surfaces corresponding to the metal rings and the blind holes. The flexible rods are fixed by screwing set screws 8 into the threaded holes. Preferably, the size of the threaded holes is M2×2, and the set screws 8 are hexagonal flat-point set screws, and the specific model is GB / T 77-2000.

[0041] In another embodiment, both the upper surface and the lower surface of the metal ring are provided with beveled groove surfaces 14 , cable through holes are provided on the beveled groove surfaces 14 , and beveled grooves are provided between adjacent beveled groove surfaces.

[0042] In this embodiment, the upper and lower surfaces of the metal ring are each provided with four beveled grooves, with a bevel groove provided between two adjacent beveled grooves on each surface. The beveled grooves achieve weight reduction and facilitate processing. If the metal ring were flat instead of having beveled grooves, the surface roughness of this surface would affect the contact between the two metal rings. If the beveled surfaces of the beveled grooves already come into contact due to protrusions, the beveled surfaces of the threading holes on either side do not, affecting the bending angle of the joint.

[0043] The bevel grooves include two symmetrically arranged arc-shaped bevel grooves 13 and two symmetrically arranged weight-reducing bevel grooves 12, and the two arc-shaped bevel grooves on the upper surface of the metal ring and the two arc-shaped bevel grooves on the lower surface are staggered, and the two weight-reducing bevel grooves on the upper surface of the metal ring and the two weight-reducing bevel grooves on the lower surface are staggered.

[0044] In addition, each bevel groove surface is provided with a group of cable through holes, the number of which decreases from the outside to the inside, and the driving cable passes through the cable through holes to manipulate the robotic arm to perform bending movement.

[0045] In another embodiment, earrings 15 are symmetrically provided on the upper surface of the metal ring.

[0046] In this embodiment, earrings are symmetrically arranged at relative positions on the arc-shaped bevel groove on the upper surface of the metal ring, and micro bearings 11 are symmetrically arranged on the outer side of the earrings. The symmetrically arranged earrings and micro bearings are connected by pins 10. By arranging the micro bearings 11 on the metal ring, the adverse effects caused by friction between traditional rigid hinges can be avoided, and the friction between the metal rings can be reduced to the greatest extent. While greatly improving the flexibility of the robotic arm, the miniaturization of the overall structure is maintained.

[0047] In another embodiment, grooves 16 are evenly arranged on the side surfaces of the metal ring.

[0048] In this embodiment, four grooves are evenly arranged on the cylindrical side of the metal ring to reduce the weight of the metal ring and thus improve the bending flexibility of the robotic arm.

[0049] The above general description of the invention and the description of its specific embodiments involved in this application should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art may, without violating the constituent elements of the invention involved, add, subtract, or combine the disclosed technical features in the above general description and / or specific embodiments (including examples) to form other technical solutions within the scope of protection of this application.

Claims

1. A variable stiffness structure for a continuum robotic arm, comprising: A structural body, wherein the structural body is arranged on the outside of the continuum robot arm and wraps the outer surface of the continuum robot arm; The structure body is a hollow structure, and the structure body adjusts the stiffness of the continuum robot arm according to the change of the pressure in the hollow structure; The variable stiffness structure further includes a vacuum pump; The structural body is provided with a variable stiffness medium, which includes a particle damping medium or a friction interference layer medium. The structural body is made of a silicone material, and the structural body is externally connected to a vacuum pump through a conduit, and the vacuum pump evacuates the structural body through the conduit. When the internal pressure of the structural body decreases, the variable stiffness medium produces a gathering effect under the action of negative pressure, so that the structural body has a higher stiffness, thereby exerting a restraining effect on the continuum robot arm, so that the continuum robot arm achieves a high stiffness state. When the internal pressure of the structural body increases, the variable stiffness medium releases the gathering effect, the stiffness of the structural body decreases, and the continuum robot arm changes to a low stiffness state. in, The continuum robotic arm comprises a plurality of continuum robotic arm structural units with the same structure; Each continuum robotic arm structural unit includes a metal ring, with blind holes provided on both the upper and lower surfaces of the metal ring, and flexible rods inserted into the blind holes to connect two adjacent metal rings; the blind holes on the upper surface of the metal are arranged alternately with the blind holes on the lower surface, and the connecting line between the two symmetrically arranged blind holes on the upper surface is perpendicular to the connecting line between the two symmetrically arranged blind holes on the lower surface; superelastic nickel-titanium memory alloy flexible rods are inserted into the blind holes to fix the adjacent metal rings, and threaded holes are provided on the four cylindrical sides corresponding to the metal rings and the blind holes, and the flexible rods are fixed by screwing set screws into the threaded holes; The upper and lower surfaces of the metal ring are each provided with four beveled groove surfaces, each beveled groove surface is provided with a cable through hole, and beveled grooves are provided between adjacent beveled groove surfaces; The bevel grooves include two symmetrically arranged circular arc bevel grooves and two symmetrically arranged weight-reducing bevel grooves, and the two circular arc bevel grooves on the upper surface of the metal ring and the two circular arc bevel grooves on the lower surface are staggered, and the two weight-reducing bevel grooves on the upper surface of the metal ring and the two weight-reducing bevel grooves on the lower surface are staggered; Each bevel groove surface is provided with a group of cable through holes, the number of which decreases from the outside to the inside, and the driving cable passes through the cable through holes to manipulate the robotic arm to perform bending motion; Earrings are symmetrically arranged at positions relative to the arc-shaped bevel grooves on the upper surface of the metal ring; miniature bearings are symmetrically arranged on the outer sides of the earrings, and the symmetrically arranged earrings and miniature bearings are connected by pins; Four grooves are evenly arranged on the side surface of the metal ring.

Images