Tendon-driven sheath, tendon-driven system and humanoid robot hand

Abstract

The utility model belongs to the field of robot transmission technology, especially relates to a tendon driving sheath, tendon driving system and humanoid robot hand. A tendon driving sheath, comprising: inner layer, be made of self -lubricating high molecule material, is used to accommodate and guide tendon rope, and metal layer, the outside of inner layer is covered, is used for providing radial support for the inner layer, to prevent the inner layer from collapsing when bending.

Description

Technical Field

[0001] This utility model belongs to the field of robot transmission technology, and in particular relates to a tendon chord drive sheath, a tendon chord drive system, and a humanoid robot hand. Background Technology

[0002] In the design of humanoid robots, especially their dexterous hands or bionic feet, chord actuation systems play a crucial role. These systems use flexible chords, such as steel wire ropes or polymer fiber ropes, to precisely transmit the power and torque generated by actuators located far from the joints to the end joints. This arrangement effectively reduces the rotational inertia of the limb's end, thereby enabling faster, more flexible, and precise motion control. To protect the chords during reciprocating motion in complex paths and to reduce frictional losses, sheaths are typically placed on the outside of the chords for guidance and isolation.

[0003] Currently, most existing sheath structures for chord actuation are single-layer tubular or simple composite structures. These existing technologies have revealed several problems in practical applications: First, when using general-purpose polymer materials as the inner wall of the sheath, the chords generate significant friction under high speed and high load, leading to energy loss, reduced transmission efficiency, accelerated wear between the chords and the sheath, and shortened service life. Second, to maintain flexibility, some sheaths lack sufficient radial stiffness, making them prone to collapse or cross-sectional deformation under pressure when passing through curved paths, such as robot joints, thus squeezing the chords and severely affecting their smoothness of movement. Third, some composite sheath structures, such as those using metal spring tubes as the inner layer for support, solve the collapse problem, but the direct contact between the metal inner wall and the chords exacerbates the friction issue. Fourth, other solutions attempt to address friction by introducing lubricant pathways and oil supply systems, but this undoubtedly significantly increases structural complexity, manufacturing costs, and maintenance difficulty, and introduces the potential risk of lubricant leakage, reducing system reliability.

[0004] Therefore, there is an urgent need in the field to provide a novel chord drive protective sleeve that simultaneously addresses the technical pain points of existing technologies, such as high friction between the chord and the inner wall of the sleeve, and insufficient support of the sleeve during bending. Specifically, the industry urgently needs a solution that can provide a low-friction sliding environment for the chord internally, while ensuring sufficient radial support strength in its external structure to resist bending deformation. This would significantly improve the transmission efficiency, stability, and long-term reliability of the chord drive system while simplifying the overall structure and reducing maintenance costs. Utility Model Content

[0005] The purpose of this invention is to address the above-mentioned shortcomings by providing a tendon chord drive sheath, a tendon chord drive system, and a humanoid robot hand.

[0006] Firstly, a tendon chord drive sheath, employing the following technical solution: A tendon chord drive sheath, comprising: The inner layer, made of a self-lubricating polymer material, is used to house and guide the tendon chords; and A metal layer, fitted over the outside of the inner layer, provides radial support to the inner layer to prevent it from collapsing when bent.

[0007] Furthermore, the tendon drive sheath also includes an outer layer, which is fitted over the metal layer to fix the metal layer and prevent relative displacement between it and the inner layer.

[0008] Furthermore, the material of the inner layer is selected from at least one of polytetrafluoroethylene, fluorinated ethylene propylene copolymer, and polyoxymethylene.

[0009] Furthermore, the inner diameter of the inner layer is 1.2 to 1.7 times the outer diameter of the tendon cord.

[0010] Furthermore, the structure of the metal layer is a circular spring or a stainless steel tube-cut spring.

[0011] Furthermore, the outer layer is a fixed layer formed by coating or shrinking with heat shrink tubing.

[0012] Secondly, a tendon chord drive system adopts the following technical solution: A chord drive system, comprising: tendons; and As described above, the tendon cord is threaded through the inner layer of the sheath.

[0013] Furthermore, the tendon rope is a steel wire rope or a polymer fiber rope.

[0014] Thirdly, a humanoid robotic hand employs the following technical solution: A humanoid robotic hand includes: At least one joint; A actuator that drives the joint movement; and As described above, in the tendon chord drive system, the tendon chord connects the actuator and the joint to transmit driving force.

[0015] Furthermore, the tendon drive system is located in the finger joints, palm area, or inside the arm.

[0016] The beneficial effects of this utility model are: The tendon chord drive sheath provided by this utility model adopts a double-layer composite structure. On the one hand, its inner layer is made of self-lubricating polymer material, which directly contacts the tendon chord inside, forming an inherent and durable low-friction motion interface between the two. When the tendon chord slides back and forth at high speed and high frequency inside the sheath, the sliding resistance is greatly reduced, which directly reduces the loss of driving energy in the transmission process, thereby significantly improving the transmission efficiency of the entire tendon chord drive system. This low-friction characteristic also greatly slows down the mutual wear between the tendon chord and the inner wall of the sheath, effectively extending the overall service life of the core transmission components. Furthermore, since no external oil supply or lubrication maintenance is required, the system structure is simplified and the reliability of long-term operation is improved. Secondly, a more rigid metal layer is tightly fitted outside the inner layer. This metal layer provides stable and reliable radial support for the relatively flexible inner layer. This design ensures that the circular cross-section of the internal channel can be maintained when the sheath is subjected to external pressure or when it is bent at a large angle at the robot joint, without collapsing or deforming. This ensures that the movement path of the tendon rope is always unobstructed, ensuring the smoothness and stability of power transmission, and improving the accuracy and response speed of the robot's end effector. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the first embodiment of the tendon chord drive sheath provided in this application; Figure 2 for Figure 1 A three-dimensional structural diagram of the tendon chord drive sheath shown; Figure 3 A schematic diagram of the structure of the second embodiment of the tendon chord drive sheath provided in this application; Figure 4 for Figure 3 A three-dimensional structural diagram of the tendon chord drive sheath shown; Figure 5 To adopt Figure 1 A schematic diagram of the tendon chord drive system shown in the diagram; Figure 6 To adopt Figure 3 The diagram shows the structural schematic of the tendon chord drive system of the sheath shown.

[0018] Reference numerals: 100, sheath; 110, inner layer; 120, metal layer; 130, outer layer; 200, tendon chord drive system; 210, tendon chord. Detailed Implementation

[0019] The following detailed description, in conjunction with embodiments, provides an additional description of the tendon chord drive sheath, tendon chord drive system, and humanoid robot hand described in this utility model. For the sake of simplicity, this document cannot exhaustively list all alternative technical features and implementation schemes included in this utility model. Therefore, those skilled in the art should understand that any technical feature and implementation scheme within this embodiment does not limit the scope of protection of this utility model. The scope of protection includes all alternative technical features and implementation schemes adopted by those skilled in the art without inventive effort. Specifically, any implementation scheme obtained by replacing any technical feature in this utility model or combining any two or more technical features provided by this utility model should be within the scope of protection of this utility model.

[0020] Please see Figures 1 to 6 This application provides a tendon chord drive technology solution for precision equipment such as humanoid robots.

[0021] This embodiment provides a tendon chord drive sheath 100. For example... Figure 1 and Figure 2 As shown, the basic structure of the sheath 100, namely structure one, includes at least two core layers: an inner layer 110 and a metal layer 120.

[0022] Specifically, the inner layer 110 is a channel component that directly contacts the tendon tract 210. Its core function is to accommodate the tendon tract 210 and form a smooth guiding path within it. To achieve this function, the inner layer 110 is made of a self-lubricating polymer material. The "self-lubricating" characteristic here refers to the material's extremely low coefficient of friction. When the tendon tract 210 reciprocates at high speed within it, no additional lubricating oil or grease is needed to reduce sliding friction to an extremely low level. This design fundamentally solves the problems of energy loss and component wear caused by friction in existing technologies. Because the frictional heat generation effect is significantly weakened, the thermal stability of the system under high load and high frequency operation is also guaranteed. Structurally, the inner layer 110 is typically a thin-walled tubular structure with precise inner diameter and wall thickness.

[0023] The metal layer 120 serves as the supporting framework for the sheath 100, fitted over the inner layer 110. Its primary function is to provide strong radial support for the relatively flexible inner layer 110. In robotic applications, the sheath 100 needs to bend with joint movement, experiencing radial pressure from external structures or chord tension at the bending points. Without sufficient support, the tubular channels of the inner layer 110 could be flattened or collapse, potentially jamming or severely hindering the movement of the chords 210, leading to transmission failure. The metal layer 120, with its inherent high rigidity and strength, effectively resists these radial pressures, ensuring that even when the sheath 100 bends at large angles, the internal channels of the inner layer 110 maintain a smooth, circular or near-circular cross-section, thus guaranteeing the smoothness of the chord movement and the stability of power transmission. Furthermore, to ensure the overall flexibility of the sheath, the metal layer 120 is not a solid metal tube but rather employs a flexible structure, such as a spring.

[0024] Through the synergistic effect of the inner layer 110 and the metal layer 120, the sheath 100 of this embodiment achieves both low-friction guidance and high-strength support simultaneously, relying solely on its own structure and material properties, without the need for a complex oil supply system. This significantly improves the transmission efficiency, reliability, and service life of the tendon drive system, while simplifying the overall system design, manufacturing, and subsequent maintenance, perfectly solving the technical problems raised in the background art.

[0025] This embodiment provides a preferred sheath, namely structure two. For example... Figure 3 and Figure 4 As shown, in addition to the inner layer 110 and the metal layer 120, the tendon chord drive sheath 100 further includes an outer layer 130.

[0026] The outer layer 130 is tightly fitted over the metal layer 120. Its core function is to secure the metal layer 120, firmly binding it to the outer surface of the inner layer 110. Since the metal layer 120 is often a spring-like structure, slight relative slippage or displacement may occur between the turns of the spring and between the spring as a whole and the inner layer 110 during repeated bending and stretching of the sheath 100. Over time, this interlayer displacement accumulates and leads to wear, reducing the structural stability and durability of the sheath. The presence of the outer layer 130 acts like a secure "outer garment," locking the position of the metal layer 120 and preventing relative displacement with the inner layer 110, thus forming a stable and reliable overall structure and significantly improving the durability of the sheath. Furthermore, the outer layer 130 can provide additional protective functions, such as enhancing the sheath's impact resistance, abrasion resistance, chemical corrosion resistance, and electrical insulation, enabling it to withstand more demanding industrial application environments.

[0027] In one specific embodiment, the material of the inner layer 110 is selected from at least one of polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), and polyoxymethylene (POM), or is made of a modified material thereof.

[0028] Polytetrafluoroethylene (PTFE), commonly known as the "King of Plastics," is renowned for having one of the lowest coefficients of friction among all solid materials, with a dynamic coefficient of friction of approximately 0.04. It is an ideal choice for achieving self-lubricating and low-friction functions.

[0029] Fluorinated ethylene propylene copolymer (FEP) is a copolymer of PTFE. It retains the excellent low friction, chemical stability and high and low temperature resistance of PTFE, while having better thermoplastic processability and being easier to be precisely extruded into thin-walled capillaries.

[0030] Polyoxymethylene (POM) is an engineering plastic with excellent comprehensive performance. It not only has a low coefficient of friction and good self-lubricating properties, but also high rigidity, high fatigue strength and excellent dimensional stability.

[0031] Choosing any one of these materials or a combination thereof ensures that the inner layer 110 achieves excellent low-friction performance, thereby reducing energy consumption and extending lifespan.

[0032] In one specific embodiment, the inner diameter of the inner layer 110 is 1.2 to 1.7 times the outer diameter of the tendon cord 210.

[0033] If the ratio of the inner diameter to the outer diameter of the tendon cord is less than 1.2, the gap between the two will be too small, which will increase the difficulty of assembly. Furthermore, when bending, the tendon cord 210 is more likely to have excessive contact with the inner wall, resulting in increased friction.

[0034] If the ratio is greater than 1.7, the gap between the two is too large, and the radial movement space of the tendon rope 210 inside the sheath is too large. During transmission, it is easy to generate vibration or whipping effect, which reduces the accuracy and stability of transmission and may generate noise.

[0035] Therefore, controlling this dimensional relationship within the range of 1.2 to 1.7 times represents the optimal balance between ensuring smooth passage of the tendon 210 and achieving precise and stable guidance. For example, for a tendon 210 with an outer diameter of 1.0 mm, a PTFE tube with an inner diameter of 1.3 mm can be selected as the inner layer 110, which provides sufficient clearance for movement while ensuring good guidance.

[0036] In one specific embodiment, the structure of the metal layer 120 is a circular spring or a stainless steel tube cutting spring, also known as a snake tube.

[0037] Circular springs, such as tension springs made of tightly wound 304, 316, or 316L stainless steel wire, are a classic structure for achieving radial support and axial flexibility. The diameter of the spring wire, for example 0.3 mm, and the pitch, for example 0.5 mm, can be adjusted according to the required support strength and flexibility. This structure is low in cost and simple to manufacture.

[0038] Stainless steel tube-cut spring serpentine tubes represent a more advanced structure. They are created by using precision machining techniques such as laser cutting to create specific spiral or serpentine grooves on thin-walled stainless steel tubes, giving them the flexibility of a spring while maintaining the tube's overall integrity. Compared to wound springs, serpentine tubes have smoother inner and outer surfaces, more uniform stress distribution, better torsional resistance, and provide more stable and consistent support.

[0039] Both structures effectively provide rigid radial support while allowing the sheath to bend 100° freely, perfectly adapting to the complex motion requirements of robot joints.

[0040] In one specific embodiment, the outer layer 130 is a fixing layer formed by coating or shrinking with heat shrink tubing.

[0041] The coating process refers to uniformly coating liquid or powdered polymer materials such as FEP, PTFE, PVDF, silicone rubber, PEEK, etc. onto the outer surface of the metal layer 120, and then forming a seamless protective layer through heating, curing, melting, or other methods.

[0042] Heat shrink tubing shrinkage is a simpler and more efficient process. The specific operation involves first placing a heat shrink tubing with an inner diameter slightly larger than the outer diameter of the metal layer 120. Materials such as FEP, PVDF, and modified cross-linked polyolefins can be used. This tubing is then uniformly heated using a heat gun or oven. Upon heating, the heat shrink tubing shrinks radially, eventually tightly wrapping around and adhering to the surface of the metal layer 120, even partially penetrating the gaps in the spring, thus achieving excellent fixation and sealing. This method is mature, consistent, and can quickly form a strong and aesthetically pleasing outer layer 130.

[0043] This embodiment provides a tendon chord drive system 200. For example... Figure 5 and Figure 6 As shown, the chord drive system 200 is a fully functional transmission unit, comprising the aforementioned sheath 100 and a chord 210. In this system, the chord 210 is threaded through the inner layer 110 of the sheath 100, forming the core assembly for motion transmission. The sheath 100 provides full protection, support, and low-friction guidance for the movement of the chord 210, while the chord 210, as a flexible transmission medium, precisely transmits tension under the constraint and guidance of the sheath 100.

[0044] In one specific embodiment, the tendon rope 210 is a steel wire rope or a polymer fiber rope. Steel wire ropes have extremely high tensile strength and low elongation, making them suitable for high-load, high-precision transmission applications. Polymer fiber ropes, such as those woven from ultra-high molecular weight polyethylene (UHMWPE), aramid, and other high-performance fibers, are characterized by being significantly lighter than steel wire ropes at the same strength, possessing excellent flexibility and fatigue resistance, which helps reduce the system's moment of inertia and achieve faster dynamic response.

[0045] This embodiment provides a humanoid robotic hand, which is a specific application scenario of the aforementioned sheath and drive system. The humanoid robotic hand includes at least one joint, such as an interphalangeal joint or metacarpophalangeal joint; a actuator for generating power, typically a servo motor mounted in the wrist or forearm; and the aforementioned tendon cable drive system 200. In this robotic hand, one end of the tendon cable 210 is connected to the actuator, the other end is connected to the joint structure to be driven, such as a phalanx, and the middle portion passes through the sheath 100. When the actuator operates, it transmits tension by retracting and expanding the tendon cable 210. This tension, precisely guided by the sheath 100, ultimately acts on the joint, causing it to produce the desired flexion and extension movements.

[0046] In one specific embodiment, the tendon-driven system is deployed within the finger joints, palm area, or arm. For example, to drive the distal joint of a finger, the sheath 100 and tendon 210 need to meander through the palm, proximal phalanx, and middle phalanx, forming bends at each joint. The sheath 100 of this application, with its excellent flexibility, support, and low friction, is perfectly suited for efficient transmission tasks under such complex paths, ensuring that driving force is transmitted to the distal actuator with minimal loss, thereby enabling the robotic hand to perform flexible, precise, and powerful grasping and manipulation.

[0047] The working principles of the chord drive sheath, chord drive system, and humanoid robot hand disclosed in this application are as follows: In humanoid robot hand applications, actuators such as motors that drive joint movements are typically integrated into the relatively spacious forearm or wrist to reduce the weight and inertia of the hand and fingers. Power needs to be transmitted to the various joints of the fingers in a lightweight and flexible manner. The tendon chord drive system 200 of this application is the core component responsible for this task.

[0048] Its working process is as follows: when the actuator, such as the motor, starts and rotates, it winds or releases the tendon cord 210 connected to it, thereby generating a precise tension on the tendon cord 210. This tendon cord 210 starts from the actuator, passes through the sheath 100 pre-laid inside the robot hand, such as the arm, palm, and fingers, and finally connects to the corresponding mechanical structure of the target joint.

[0049] In this process, the sheath 100 plays a crucial and multifaceted role: Low-friction guidance: The tendon 210 slides within a channel made of an inner layer 110, such as PTFE material. Due to the extremely low coefficient of friction of the inner layer 110 material itself, the tendon 210 experiences minimal energy loss during the transmission of tension. This ensures that the force output from the actuator can be efficiently transmitted to the end joint, resulting in rapid response and precise control of the robotic hand.

[0050] Path constraint and support: When the sheath 100 bends with the wrist or finger joints, the outer metal layer 120, like a stainless steel spring, provides strong radial support. This ensures that the channels of the inner layer 110 are not flattened or collapsed, always maintaining unobstructed space for the movement of the tendon 210, thereby avoiding the risk of transmission jamming or interruption.

[0051] Structural stability: The outermost layer 130, such as FEP heat shrink tubing, tightly secures the metal layer 120 and the inner layer 110 together, forming a robust whole. This prevents relative slippage and wear between the layers during long-term repeated bending movements, ensuring the structural integrity and long service life of the entire sheath 100.

[0052] Ultimately, the tension, efficiently and stably guided by the sheath 100, acts on the finger joints, driving them to perform flexion and extension movements, thus realizing the complex functions of the robotic hand such as grasping and manipulation. In summary, this application, through an innovative multi-layer composite sheath structure, successfully solves the core technical challenges of tendon chord drive systems, providing a reliable, efficient, and durable key component for realizing high-performance humanoid robotic hands.

[0053] For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, but obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this invention.

Claims

1. A tendon chord drive sheath, characterized in that, include: The inner layer, made of a self-lubricating polymer material, is used to house and guide the tendon chords; and A metal layer, fitted over the outside of the inner layer, provides radial support to the inner layer to prevent it from collapsing when bent.

2. The sheath according to claim 1, characterized in that, The tendon drive sheath also includes an outer layer, which is fitted over the metal layer to fix the metal layer and prevent relative displacement between it and the inner layer.

3. The sheath according to claim 1, characterized in that, The inner diameter of the inner layer is 1.2 to 1.7 times the outer diameter of the tendon cord.

4. The sheath according to claim 1, characterized in that, The structure of the metal layer is a circular spring or a stainless steel tube cut spring.

5. The sheath according to claim 2, characterized in that, The outer layer is a fixed layer formed by coating or shrinking with heat shrink tubing.

6. A chord drive system, characterized in that, include: tendon ligaments; as well as The sheath as described in any one of claims 1 to 5, wherein the tendon cord is threaded through the inner layer of the sheath.

7. The chord drive system according to claim 6, characterized in that, The tendon rope is a steel wire rope or a polymer fiber rope.

8. A humanoid robotic hand, characterized in that, include: At least one joint; A actuator that drives the movement of the joint; as well as The tendon cord drive system as claimed in any one of claims 6 to 7, wherein the tendon cord in the tendon cord drive system connects the actuator and the joint for transmitting driving force.

9. The humanoid robot hand according to claim 8, characterized in that, The tendon drive system is located in the finger joints, palm area, or inside the arm.

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