Optical fiber power composite cable for humanoid robots

Abstract

The application discloses a kind of optical fiber power composite cable for human type robot.The composite cable adopts self-supporting structure of no central reinforcing unit, mainly by power insulation wire and optical fiber communication unit to adopt self-supporting star type stranding to form cable body, after stranding, annular tape is coated on cable body, and gap is provided with cotton thread;Optical fiber communication unit includes central buffer cavity, optical fiber unit and reinforcing tube, central buffer cavity includes tubular structure and its inside axially spirally arranged beam-shaped strip, and air cavity is formed on both sides of beam-shaped strip;Power insulation wire includes power transmission unit and composite insulation layer, composite insulation layer is modified ETFE material, including ETFE base resin, polytetrafluoroethylene micro powder and EFEP toughening agent.Compared with prior art, without reinforcing element self-supporting, after canceling reinforcing element, dynamic friction coefficient can be improved, bending fatigue life is reduced, weight and operating force are reduced.

Description

Technical Field

[0001] This invention relates to the field of robot joint cable technology, and in particular to a flexible composite cable without a central reinforcement and with ETFE insulation, suitable for high-frequency torsional bending conditions. Background Technology

[0002] There are two major contradictions in existing technology: 1. Material limitations: Traditional FEP insulation layers are prone to microcracks after 5 million bending cycles, while unmodified ETFE materials have insufficient dynamic fatigue strength, making it difficult to meet the requirement of 10 million torsional cycles.

[0003] 2. Structural dependence: Most composite cables rely on central reinforcement components (such as nylon wires and Kevlar) to bear mechanical stress. Removing these components will lead to a significant decrease in structural stability and dynamic performance. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention provides an optical fiber power composite cable for humanoid robots.

[0005] The technical solution adopted in this invention is: The composite cable adopts a self-supporting structure without a central reinforcing unit. It mainly consists of a power insulated wire and an optical fiber communication unit, which are twisted together in a self-supporting star shape to form the cable body. The twisted cable body is covered with an annular wrapping tape, and cotton thread is placed in the gap between the annular wrapping tape and the cable body.

[0006] The optical fiber communication unit includes a central buffer cavity at the very center, optical fiber units surrounding the central buffer cavity, and an outermost reinforcing tube. Several optical fiber units are arranged circumferentially around the central buffer cavity and then placed as a whole in the reinforcing tube.

[0007] The fiber unit uses three bend-insensitive optical fibers with PEEK corrugated tubes, which are spirally twisted around the central buffer cavity with a 120° phase difference and a 0.01mm air gap between them.

[0008] The central buffer cavity is made of polyimide material to form a tubular structure, and inside the tubular structure, there are also polyimide material to form beams arranged along the axis. Each cross section of the beams along the axis passes through the center of the tubular structure and is arranged radially. The beams along the axis are arranged in a spiral direction, so that air cavities are formed on both sides of the beams at each point along the axis inside the structure.

[0009] The power insulated wire includes a power transmission unit and a composite insulation layer, with the power transmission unit placed in the inner layer and the composite insulation layer covering the power transmission unit.

[0010] The power transmission unit is a silver-plated copper alloy conductor with a Z-shaped stranded structure, i.e., a Z-shaped conductor, with 37 outer wires arranged in a wave shape and an undulation height of 0.2mm.

[0011] The composite insulation layer is a modified ETFE material, mainly composed of 75 parts by weight of ETFE base resin, 10 parts by weight of polytetrafluoroethylene micro powder and 12 parts by weight of EFEP toughening agent. After 10 million cycles of ±180° torsion at a length of 300mm, the fiber attenuation change is ≤0.3dB / km, and the bending life at ±90° with a 7D bending radius is ≥5 million cycles.

[0012] The composite insulating layer is formed by electron beam irradiation crosslinking process, with a thickness of 0.8-1.2 mm. The EFEP toughening agent is an ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer, and nano-zinc oxide modified with silane coupling agent and triallyl isocyanurate are added as irradiation sensitizers. All formulation components are as follows by weight: ETFE base resin: 75 parts Polytetrafluoroethylene micro powder: 10 parts Ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer: 12 parts Nano zinc oxide modified with silane coupling agent: 3 parts Triallyl isocyanurate: 2 parts.

[0013] Thus, the material is modified by ETFE ternary composite, PTFE micro powder reduces the dynamic friction coefficient, EFEP provides reversible deformation capability, and nano zinc oxide inhibits silver ion migration, synergistically improving the fatigue resistance of the material.

[0014] The structural design and material modification of this invention are not simply superimposed, but rather synergistically enhanced: Synergy between Z-shaped conductor and modified ETFE: The reverse torque of the Z-shaped conductor requires the insulation layer to have good flexibility (otherwise the insulation layer will crack due to the torque). The high elongation at break (350%) and low coefficient of friction (0.15) of modified ETFE meet this requirement, ensuring that the reverse torque of the conductor is effectively transmitted to the entire cable and achieving self-support. Synergy between fiber optic levitation positioning and composite insulation layer: The levitation positioning of fiber optics requires the insulation layer to have uniform pressure transmission (otherwise the bellows will shift due to the shrinkage of the insulation layer). The composite insulation layer achieves a uniform molecular cross-linking structure through electron beam irradiation cross-linking process (gel content 65-70%), which ensures the uniformity of pressure of the insulation layer on the internal structure (deviation ≤5%) and avoids the displacement of the bellows. Synergy between the central buffer cavity and the conductor: The stress buffering effect of the central buffer cavity reduces the axial strain of the conductor (from 0.12% to 0.07%), while the Z-shaped stranded structure of the conductor further absorbs the residual stress. The synergy between the two keeps the conductor wire breakage rate at 0.8% (≤1%).

[0015] The beneficial effects of this invention are: 1) Structural innovation: The self-supporting structure without a central reinforcement achieves the torsional and tensile resistance functions of traditional central reinforcement through the synergy of a central buffer cavity, fiber double helix suspension, and conductor Z-shaped stranding, while reducing weight (42g / m). 2) Material innovation: The ETFE ternary composite formula (ETFE+PTFE+EFEP+nano zinc oxide) solves the problems of "insufficient dynamic fatigue strength" and "high coefficient of friction" of traditional ETFE, and increases the bending fatigue life to 5.8 million cycles (16% over the target). 3) Collaborative innovation: The synergy between structural design and material modification has enabled the cable's torsional life, bending life, weight and other indicators to far exceed those of existing technologies, achieving a breakthrough of "no reinforcement, long life and lightweight".

[0016] Compared with existing technologies, this invention achieves three major breakthroughs: 1. Self-supporting without reinforcement: Through the topological interlocking of Z-shaped conductor stranding and spiral fiber unit, a reverse torque (≤0.3N·m) is generated when twisted at 300mm, replacing the function of traditional center reinforcement.

[0017] 2. ETFE material modification and enhancement: Adding 10% PTFE micro powder reduces the dynamic friction coefficient by 40%, and the EFEP toughening phase increases the bending fatigue life to 6 million cycles (20% over the target).

[0018] 3. Lightweight Breakthrough: After eliminating the reinforcing parts, the weight is reduced to 42g / m, which is 28% lighter than that with Kevlar reinforcement, and the operating force during 7D bending is reduced by 35%. Attached Figure Description

[0019] Figure 1 This is a cable structure diagram of the present invention.

[0020] In the figure: central buffer cavity (1), optical fiber unit (2), power transmission unit (3), composite insulation layer (4), reinforcing tube (5), cotton thread (6), and ring wrapping tape (7). Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1As shown, the composite cable adopts a self-supporting structure without a central reinforcing unit. It mainly consists of a power insulated wire and an optical fiber communication unit, which are self-supporting star-shaped twisted together to form the cable body. The twisted cable body is covered with an annular wrapping tape 7, and cotton thread 6 is placed to fill the gap between the annular wrapping tape 7 and the cable body.

[0023] The specific implementation includes two power-insulated wires and one optical fiber communication unit, which are self-supporting star-shaped stranded to form the core of the composite cable.

[0024] like Figure 1 As shown, the optical fiber communication unit includes a central buffer cavity 1 located at the very center, optical fiber units 2 located around the central buffer cavity 1, and an outermost reinforcing tube 5. The central buffer cavity 1 and the optical fiber units 2 are placed inside the reinforcing tube 5. Several optical fiber units 2 are arranged circumferentially around the central buffer cavity 1 and then placed as a whole in the reinforcing tube 5.

[0025] Fiber unit 2 uses three bend-insensitive optical fibers with PEEK corrugated tubes, spirally twisted around the central buffer cavity 1 with a 120° phase difference and a 25mm pitch, with a 0.01mm air gap between them. This forms a triple-helix fiber levitation positioning. The 0.01mm air gap between the corrugated tubes and the optical fibers ensures that the optical fibers are in a "stress-free levitation" state when bent, and the micro-bending loss is controlled within 0.2dB / km.

[0026] The central buffer cavity 1 is mainly made of polyimide to form a tubular structure. Inside the tubular structure, there are also polyimide beams arranged along the axis. Each cross-section of the beams passes through the center of the tubular structure radially. The beams are arranged in a helical direction along the axis, so that air cavities are formed on both sides of the beams at each point along the axis inside the structure, forming an air spring system. The tubular structure and the beams are integrally molded from polyimide.

[0027] The central buffer cavity 1 consists of two helical air cavities with semi-circular cross sections. When assembled, they form an air cavity with a diameter of 1.2 mm. The cavity contains a helical polyimide beam strip with a thickness of 0.02 mm and a pitch of 5 mm, creating an air spring effect.

[0028] In the air spring buffer system, the spiral polyimide beam strip in the central buffer cavity generates an elastic deformation of 0.15mm when twisted, absorbing the axial impact generated by ±180° torsion (strain reduction of 35%).

[0029] like Figure 1 As shown, the power insulated wire includes a power transmission unit 3 and a composite insulation layer 4. The power transmission unit 3 is placed in the inner layer, and the power transmission unit 3 is covered by the composite insulation layer 4.

[0030] The power transmission unit 3 is a silver-plated copper alloy conductor with a Z-shaped stranded structure, i.e., a Z-shaped conductor, with 37 outer wires arranged in a wavy pattern. The composite insulation layer 4 is made of modified ETFE material.

[0031] The embodiments of the present invention are as follows: Example 1: A) The composite cable adopts a self-supporting star-shaped stranded structure, such as Figure 1 As shown, from the inside out are: Fiber optic communication unit: Central buffer chamber 1: An air cavity with a diameter of 1.2 mm, containing a spiral polyimide beam (thickness 0.02 mm, pitch 5 mm) to create an air spring effect. Fiber unit 2: 3 Φ0.25mm bend-insensitive optical fibers (G.657.B3), using double-helix suspension positioning: - Positioning structure: Polyetheretherketone (PEEK) micro-corrugated tube (inner diameter 0.3mm, wave pitch 0.8mm) - Distribution method: Three corrugated pipes are spirally twisted with a 120° phase difference (pitch 25mm) to form a dynamic stress dispersion system. Reinforcing tube 5: Made of PEEK extrusion molding.

[0032] The power insulated wire: Power transmission unit 3: 2 silver-plated copper alloy conductors (cross-sectional area 0.5-2.0 mm²) 2 ), using a Z-shaped stranded structure: - Monofilament specifications: Φ0.05mm ultrafine copper alloy wire (silver content 0.3%, tensile strength ≥450MPa) - Stranding parameters: Inner layer 19 strands stranded (pitch 6mm), outer layer 18 strands arranged in a Z-shape (undulation height 0.2mm) to achieve self-balance of tensile and compressive stress.

[0033] Composite insulation layer 4: Modified ETFE material, formed by electron beam irradiation crosslinking process, thickness 0.8-1.2mm, formulation composition (by weight): ETFE base resin (melt index 3.5 g / 10 min): 75 parts Polytetrafluoroethylene micro powder (particle size 0.5μm): 10 parts Ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer (EFEP): 12 parts Nano zinc oxide (modified with silane coupling agent): 3 parts Irradiation sensitizer: Triallyl isocyanurate (TAIC): 2 parts.

[0034] B) Key Preparation Processes 1. Fiber unit forming: PEEK corrugated tubes are formed by micro-extrusion (temperature 380℃). After the fiber is inserted, an air gap of 0.01mm is injected, and negative pressure is used to ensure the suspension state. 2. Conductor stranding process: A variable pitch star stranding machine is used, and the Z-shaped outer layer stranding pitch changes periodically in the pattern of "15mm-20mm-15mm" to form a dynamic stress buffer zone; 3. Irradiation crosslinking of the insulating layer: Electron beam irradiation dose of 80-100kGy (accelerating voltage of 180kV) to make the ETFE gel content reach 65-70%, which improves fatigue resistance while maintaining flexibility; 4. Overall sintering process: 180℃ hot air circulation treatment for 2 hours to eliminate internal stress in the material and ensure the coordinated deformation capability of the insulation layer and the internal structure.

[0035] In the existing technology, "structural dependence on central stiffeners" and "insufficient dynamic fatigue of materials" are two independent problems. The conventional solutions are to "optimize the central stiffeners" (such as using lighter Kevlar) or "improve ETFE materials" (such as adding toughening agents).

[0036] The concept of this invention is "structural replacement material" + "material-reinforced structure": a structure of "central buffer cavity + Z-shaped conductor + optical fiber spiral stranding" is used to synergistically replace the central reinforcing component (solving structural dependence), and "ETFE ternary composite formula" is used to enhance the fatigue resistance of the structure (solving material limitations). This approach of synergistically resolving the dual contradictions through "structure-material" is not something that those skilled in the art would easily conceive of based on existing technology.

[0037] The synergistic effect of the structural design (central buffer cavity, fiber optic levitation positioning, Z-shaped conductor) and material modification (ETFE ternary composite) of this invention cannot be derived by those skilled in the art using existing technology. For example, the reverse torque of the Z-shaped conductor requires the insulation layer to have good flexibility, which is precisely met by the low coefficient of friction and high fatigue resistance of modified ETFE; the levitation positioning of the fiber optic requires the insulation layer to have uniform pressure transmission, which is precisely guaranteed by the uniformity of the composite insulation layer (achieved through irradiation crosslinking process). This synergistic effect is the core embodiment of the inventiveness of this invention.

[0038] Test data from this invention show that the torsional life of the cable without a central reinforcement reaches 12.5 million cycles (25% exceeding the target), far exceeding that of cables with Kevlar reinforcement in the prior art (maximum 8 million cycles); the weight is reduced to 42 g / m (6.7% exceeding the target), a 28% reduction compared to cables with Kevlar reinforcement. These results are an unexpected breakthrough from the conventional understanding that "removing the reinforcement reduces lifespan," demonstrating the significant progress made by this invention.

[0039] The dynamic performance test data for this embodiment is as follows: The comparison in the table above shows that the cable of this invention exhibits superior performance in core indicators such as torsion life, bending life, fiber attenuation, insulation performance, and weight, comprehensively surpassing traditional ETFE cables and meeting or exceeding the required specifications. The torsion life reaches 12.5 million cycles, more than three times that of traditional cables and exceeding the target by 25%; the bending life is 5.8 million cycles, 1.6 times that of traditional cables, slightly exceeding the 5 million cycle target; the fiber attenuation change is only 0.28 dB / km, meeting the standard of ≤0.3 dB / km, far lower than the 1.2 dB / km of traditional cables; the insulation layer showed no cracks after testing, while traditional cables developed circumferential cracks after 5 million cycles; the overall weight is 42 g / m, not only meeting the ≤45 g / m target but also being 6 g / m lighter than traditional cables. These data further verify that the innovative design of this invention, which eliminates the central reinforcement, breaks through conventional understanding, achieving lightweight while ensuring performance, and is more suitable for the complex working environment of humanoid robots involving high-frequency torsion and bending, demonstrating significant technological progress and application value.

[0040] After multiple tests, the solution of this invention can achieve the following effects: Dynamic durability: 10 million cycles of ±180° twisting at a length of 300mm (frequency 1Hz), fiber attenuation change ≤0.3dB / km, conductor breakage rate ≤1%.

[0041] Bending performance: 5 million bends at ±90° with a bending radius of 7D (D is the cable diameter) (speed 30 times / min), the insulation layer does not crack and the signal transmission is uninterrupted.

[0042] Structural parameters: diameter ≤ 8.5mm, weight ≤ 45g / m, 22% weight reduction compared to the design with reinforcement.

[0043] Example 2: Comparison of air spring systems with central buffer cavity and spiral polyimide beam. In existing technologies, the central cavity is mostly solid or simply hollow, and axial stress is easily transmitted to the internal structure during torsion, leading to conductor breakage or fiber micro-bending. This invention uses a helical polyimide beam to fill the central hollow cavity. Its helical structure generates elastic deformation during torsion (change in the helix angle of the film during axial tension / compression), combined with the "air spring" effect of the air cavity (pressure buffering during volume changes), significantly reducing internal stress transmission.

[0044] Experimental comparison (supplementary): Example 3: Comparison of Fiber Optic Unit and Double Helix Suspension Positioning System In existing technologies, optical fibers are mostly positioned using tight-packing or filled methods, which easily lead to micro-bending loss (≥0.5dB / km) due to compression when bent. In this invention, the optical fiber is inserted into a PEEK corrugated tube (leaving a 0.01mm air gap between the tube and the fiber to achieve "levitation"), and three corrugated tubes are spirally twisted with a 120° phase difference to form a "dynamic stress dispersion system": when bent, the spiral structure of the corrugated tube rotates slightly along the bending direction, so that the optical fiber always maintains a micro-bending radius of ≥20mm (far greater than the minimum bending radius of 5mm for G.657.B3 optical fiber), effectively controlling micro-bending loss.

[0045] Experimental comparison (supplementary): Example 4: Comparison of Composite Insulation Layer Materials The composite insulation layer of this invention adopts an ETFE ternary composite formula (75 parts by weight of ETFE base resin + 10 parts by weight of PTFE micro powder + 12 parts by weight of EFEP toughening agent + 3 parts by weight of nano zinc oxide), which solves the problems of "insufficient dynamic fatigue strength" (cracking after 5 million bending cycles) and "high coefficient of friction" (resulting in high operating force) of traditional ETFE materials.

[0046] The role of PTFE micro powder: to reduce the dynamic coefficient of friction (from 0.25 to 0.15) and reduce frictional loss between the insulation layer and the internal structure during bending; The role of EFEP toughening agent: to provide reversible deformation capability (increasing elongation at break from 250% to 350%), and to increase the crack resistance of the insulation layer; The role of nano zinc oxide: to inhibit silver ion migration (silver ions in silver-plated conductors tend to diffuse into the insulating layer, leading to a decrease in insulation resistance) and improve long-term reliability.

[0047] Experimental comparison (supplementing the performance of different formulations): As can be seen from this implementation, compared with the prior art, the present invention generates a reverse torque (≤0.3N·m) through the topological interlocking of the Z-shaped conductor stranding and the spiral optical fiber unit without the self-support of the reinforcing member. After eliminating the reinforcing member, it can improve the dynamic friction coefficient, reduce bending fatigue life, and reduce weight and operating force.

[0048] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

[0049] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A fiber optic power composite cable for humanoid robots, characterized in that: The composite cable adopts a self-supporting structure without a central reinforcing unit. It is mainly composed of a power insulated wire and an optical fiber communication unit, which are self-supporting star-shaped twisted together to form the cable body. The twisted cable body is covered with an annular wrapping tape (7), and cotton thread (6) is placed in the gap between the annular wrapping tape (7) and the cable body.

2. The fiber optic power composite cable for humanoid robots according to claim 1, characterized in that: The optical fiber communication unit includes a central buffer cavity (1) at the very center, optical fiber units (2) surrounding the central buffer cavity (1), and an outermost reinforcing tube (5). Several optical fiber units (2) are arranged circumferentially around the central buffer cavity (1) and then placed as a whole in the reinforcing tube (5).

3. The fiber optic power composite cable for humanoid robots according to claim 2, characterized in that: The fiber unit (2) uses three bend-insensitive optical fibers with PEEK corrugated tubes, which are spirally twisted around the central buffer cavity (1) with a 120° phase difference and an air gap of 0.01 mm between them.

4. The fiber optic power composite cable for humanoid robots according to claim 2, characterized in that: The central buffer cavity (1) is made of polyimide material to form a tubular structure, and in the tubular structure, the same polyimide material is used to form beams arranged along the axis. Each section of the beams along the axis passes through the center of the tubular structure and is arranged radially. The beams along the axis are arranged in a spiral direction, so that air cavities are formed on both sides of the beams at each point along the axis inside the structure.

5. The fiber optic power composite cable for humanoid robots according to claim 1, characterized in that: The power insulated wire includes a power transmission unit (3) and a composite insulation layer (4). The power transmission unit (3) is placed in the inner layer and the power transmission unit (3) is covered by the composite insulation layer (4).

6. The fiber optic power composite cable for humanoid robots according to claim 5, characterized in that: The power transmission unit (3) is a silver-plated copper alloy conductor with a Z-shaped stranded structure. The outer 37 wires are arranged in a wave shape with an undulation height of 0.2 mm.

7. The fiber optic power composite cable for humanoid robots according to claim 5, characterized in that: The composite insulation layer (4) is a modified ETFE material, mainly composed of ETFE base resin, polytetrafluoroethylene micro powder and EFEP toughening agent. The mass ratio of ETFE base resin, polytetrafluoroethylene micro powder and EFEP toughening agent is 75:10:

12. After 10 million cycles of ±180° torsion at a length of 300mm, the fiber attenuation change is ≤0.3dB / km, and the bending life at ±90° under a 7D bending radius is ≥5 million cycles.

8. The fiber optic power composite cable for humanoid robots according to claim 5, characterized in that: The composite insulating layer (4) is formed by electron beam irradiation crosslinking process. The EFEP toughening agent is an ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer, and nano zinc oxide modified with silane coupling agent and triallyl isocyanurate are added. All the formulation components are in the following parts by weight: ETFE base resin: 75 parts Polytetrafluoroethylene micro powder: 10 parts Ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer: 12 parts Nano zinc oxide modified with silane coupling agent: 3 parts Triallyl isocyanurate: 2 parts.

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