High-integration passive anti-impact flexible joint

Abstract

This invention discloses a highly integrated passive impact-resistant flexible joint, relating to the field of robot drive and flexible transmission technology. It includes a stator assembly comprising a first and second base arranged opposite each other, a core sphere made of a non-magnetic, highly conductive material, rotatably positioned between the first and second bases, with internal wiring channels and countersunk holes on its surface communicating with these channels, and a magnetic array assembly. Utilizing the eddy current effect generated by a non-magnetic conductor cutting magnetic lines of force, upon encountering external high-frequency impacts, it instantaneously generates a reverse electromagnetic torque proportional to the velocity, achieving non-contact, highly efficient energy absorption and braking. Simultaneously, it reduces static friction to improve control precision: when stationary or undergoing low-speed fine-tuning, the system operates in a state of extremely low mechanical friction, eliminating static friction interference from traditional damping devices at the physical level, thus giving the robot extremely high motion reproduction accuracy.

Description

Technical Field

[0001] This invention relates to the field of robot drive and flexible transmission technology, and in particular to a highly integrated passive impact-resistant flexible joint. Background Technology

[0002] Line-driven flexible joint technology is widely used to assist lightweight robots, dexterous hands, or exoskeletons. However, as legged robots and industrial robots expand into complex environments and precision work scenarios, existing technologies face engineering bottlenecks in the following areas: First, there is a trade-off between impact resistance and lightweight design. When robots move through complex terrain or experience sudden collisions, their joint components are susceptible to high-frequency, instantaneous impacts. Traditional active electronic control strategies are limited by the latency of the sensing and control links, making it difficult to achieve real-time response. While adding mechanical or hydraulic damping devices can improve impact resistance, it significantly increases the weight and size of the joints, thereby affecting the robot's dynamic response and energy efficiency.

[0003] Second, there is a need to improve the accuracy of low-speed control. Some damping mechanisms exhibit static friction characteristics during operation. Under low-speed fine-tuning or precise operation conditions, this characteristic may cause a "sticky-slip" phenomenon, which adversely affects the accuracy and stability of multi-joint coordinated control.

[0004] Third, there are challenges in internal wiring and miniaturized integration. Within the limited space of a miniaturized flexible joint, the method of fixing the ends of the flexible transmission cables is quite restrictive. Traditional fastening structures often occupy a lot of internal space, increasing the complexity of wiring design and, to some extent, limiting the integration density of signal and power transmission within the joint.

[0005] Therefore, there is an urgent need in this field for a flexible joint that can solve the technical problems of existing robot joints in miniaturized spaces, such as difficulty in achieving high-frequency impact resistance, low-speed high-precision control, and easy failure of cable anchoring. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a highly integrated passive impact-resistant flexible joint, solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a highly integrated passive impact-resistant flexible joint, comprising: A stator assembly comprising a first base and a second base disposed opposite to each other; The core sphere is made of a non-magnetic, highly conductive material and is rotatably positioned between the first and second bases. It has a wiring channel inside and a countersunk hole on its surface that communicates with the wiring channel. A magnetic array assembly includes multiple first magnets embedded in a first base and multiple second magnets embedded in a second base; The flexible transmission cable extends through the guide holes on the first and second bases to the cable routing channel. Its end is a heat-fused shrinkable limiting ball head with an outer diameter larger than the inner diameter of the countersunk hole, forming physical interference and step limiting. The stator assembly has five independent guide holes that penetrate the first base and the second base; The layout of the first and second magnets satisfies the following: adjacent magnets on the same base have opposite magnetic poles, and magnets on opposite sides of each other have opposite magnetic poles; the mounting slots are located at 45°, 135°, 225°, and 315°, and have a preset offset in the axial direction relative to the equatorial plane of the core sphere. This offset is calculated based on the geometric reference of spatial distance provided by the Pythagorean theorem and the superposition compensation of magnetic field to form a uniform gradient magnetic field envelope.

[0008] As a further technical solution of the present invention, the five guide holes are distributed in the gaps between adjacent magnet mounting slots, wherein three of the guide holes are independently located in the three gaps, and the other two guide holes are arranged side by side in the remaining gap, forming an asymmetrical avoidance distribution.

[0009] As a further technical solution of the present invention, the first magnet and the second magnet are N52 neodymium iron boron strong magnets.

[0010] As a further technical solution of the present invention, the flexible transmission cable is a multi-strand braided PE wire, and the inner diameter of the guide hole is larger than the outer diameter of the flexible transmission cable.

[0011] As a further technical solution of the present invention, the air gap between the outer surface of the core sphere and the first magnet and the second magnet is 0.8 mm.

[0012] As a further technical solution of the present invention, the center azimuth angles of the five guide holes are respectively set at 0°, 90°, 180°, 255° and 285°.

[0013] As a further technical solution of the present invention, the interference between the inner diameter of the countersunk hole and the outer diameter of the end of the flexible transmission cable is 0.3 mm.

[0014] Furthermore, to generate an optimal gradient magnetic field with uniform intensity and penetrating the core sphere within a limited space, the layout of the first and second magnets employs a Z-axis offset and Pythagorean theorem compensation design. Specifically, the mounting slots on the first and second bases are arranged in a diagonal array at 45°, 135°, 225°, and 315° in the circumferential direction, and also have a preset offset relative to the equatorial plane of the core sphere in the axial direction. This offset is not arbitrarily set, but is based on the Pythagorean theorem, providing a spatial linear distance parameter between adjacent magnets as a geometric reference for subsequent optimization of the magnetic field superposition effect. Through this three-dimensional spatial layout optimization, the mutual weakening of magnetic fields between magnets or the formation of excessively strong local areas is avoided, thereby generating a uniform and penetrating static gradient magnetic field envelope outside the core sphere, improving the generation efficiency and controllability of the eddy current effect.

[0015] Furthermore, this invention integrates the end-heat-fused anchoring structure of the flexible drive cable with the anti-interference wiring array within the stator assembly. Of the five independent guide holes, three are independently located in three separate gaps, while the other two are arranged adjacent to each other in the remaining gap (e.g., azimuth angles set at 0°, 90°, 180°, 255°, and 285° respectively). After the flexible drive cable passes through these guide holes, its end undergoes heat fusion treatment to form a heat-fused shrinkable limiting ball-shaped end, the outer diameter of which is larger than the inner diameter of the countersunk hole on the core sphere surface. When the cable is under tension, this limiting ball-shaped end creates a strong step-limiting effect with the inner wall of the countersunk hole and the port of the wiring channel, forming a purely physical lock-in without the need for any fasteners. This combined structure achieves interference-free five-wire redundant drive and high-reliability cable fixation within a limited volume.

[0016] This invention provides a highly integrated passive impact-resistant flexible joint, which has the following advantages compared with the prior art: Rapid Response and Shock Resistance: Utilizing the eddy current effect generated by a non-magnetic conductor cutting magnetic lines of force, a reverse electromagnetic torque proportional to the velocity can be generated in a very short time when encountering external high-frequency impacts, achieving non-contact, highly efficient energy absorption and braking. Reduced Static Friction for Improved Control Precision: The core sphere is suspended and constrained within the stator cavity by the pre-tension of five flexible transmission cables, maintaining a non-contact air gap with the stator inner wall. Therefore, when stationary or undergoing low-speed fine-tuning of attitude, the system operates in a state of extremely low mechanical friction, eliminating the static friction interference of traditional damping devices from a physical level, and endowing the robot with extremely high motion reproduction accuracy.

[0017] Extreme weight reduction and improved layout: By utilizing the limiting steps formed by the heating and melting of the flexible wire ends and the step limiting effect formed by the inner wall of the countersunk hole, redundant fasteners are eliminated, and the complex electromagnetic and mechanical coupling system is compressed into a limited volume, greatly reducing the weight of the joint and providing optimized layout space for high-density signal and power transmission. Five-line redundant drive and anti-interference design: An asymmetric five-line routing array is constructed in the stator assembly to effectively avoid the magnet mounting slot, realizing interference-free three-dimensional attitude control and tension distribution in a limited space, which greatly improves the reliability of the multi-degree-of-freedom flexible drive of the joint. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall exploded structure of the present invention; Figure 2 for Figure 1 A schematic diagram of the three-dimensional structure of the second base.

[0019] In the diagram: 1. First base; 2. Core sphere; 3. Second base; 4. Mounting slot; 5. First magnet; 6. Second magnet; 7. Guide hole; 8. Wiring channel; 9. Countersunk hole. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1-2 The present invention provides a highly integrated passive impact-resistant flexible joint technology solution: including: a stator assembly, the stator assembly including a first base 1 and a second base 3 disposed opposite to each other; The core sphere 2 is rotatably positioned between the first base 1 and the second base 3. The core sphere 2 is made of a non-magnetic, highly conductive material. In this embodiment, it is made of lightweight aluminum alloy and has a radius of 15mm. The magnetic array assembly includes multiple first magnets 5 and multiple second magnets 6. The multiple first magnets 5 are embedded in a first base 1, and the multiple second magnets 6 are embedded in a second base 3. The first magnets 5 and the second magnets 6 together form an envelope gap outside the core sphere 2, and the air gap is strictly controlled at 0.8mm. To achieve the optimal gradient magnetic field, this embodiment uses Pythagorean theorem compensation calculations for the Z-axis offset of the magnets. Specifically, let ΔZ1 be the vertical distance between the lower surface of the first magnet on the first base and the equatorial plane of the core sphere, and ΔZ2 be the vertical distance between the upper surface of the second magnet on the second base and the equatorial plane, where ΔZ1 = ΔZ2 = 2mm. The straight-line distance D between the center points of two adjacent magnets (e.g., located at 45° and 135° azimuths) in space is calculated using the Pythagorean theorem: the chord length corresponding to the circumferential arc length L = 2R·sin(45°), where R is the radius of the mounting groove distribution circle (10.6mm in this embodiment), then L ≈ 15mm; the height difference H in the Z-axis direction = ΔZ1 + ΔZ2 = 4mm; therefore, the straight-line distance D in space = √(L 2 +H 2 )=√(15 2 +4 2 The distance D is approximately 15.5 mm. By controlling this distance D to about 1.3 times the magnet diameter (12 mm) and fine-tuning it through finite element simulation, the magnetic field superposition between adjacent magnets is made to achieve the most uniform state, avoiding magnetic field cancellation or local distortion, so that the rate of change of magnetic flux cut by the core sphere in the main working rotation range shows good linearity.

[0022] In this configuration, adjacent magnets on the same base face opposite magnetic poles, and magnets on the first base 1 and the second base 3 face opposite magnetic poles, thereby forming a static gradient magnetic field that penetrates the core sphere inside the core sphere.

[0023] Multiple mounting slots 4 are arranged in a diagonal cross array on the inner sides of both the first base 1 and the second base 3. The first magnet 5 and the second magnet 6 are respectively fixed in the mounting slots 4. In this embodiment, the mounting slots are respectively set at 45°, 135°, 225° and 315°, with a total of 8 N52 neodymium iron boron strong magnets, with a diameter of 12mm and a thickness of 4mm.

[0024] The stator assembly includes an anti-interference wiring array comprising five independent guide holes 7 penetrating the first base 1 and the second base 3; three of the guide holes 7 are independently located in three magnet gaps, while the other two guide holes 7 are arranged side-by-side adjacent to each other in a fourth magnet gap. For example, the azimuth angles of the five guide holes are precisely set at 0°, 90°, 180°, 255°, and 285°, respectively.

[0025] The flexible drive cable uses multi-strand braided PE wire with a diameter of 1.8mm, and the inner diameter of the guide hole 7 in the stator assembly is 2.7mm. The countersunk hole 9 on the surface of the core sphere 2 has a diameter of 2.1mm. The flexible drive cable passes through the guide holes 7 reserved on the first base 1 and the second base 3 and extends into the wiring channel 8; the end of the flexible drive cable is a heat-fused shrinkable limiting ball head and is embedded and fixed in the countersunk hole 9, forming a 0.3mm interference fit. Under tension, this rigid limiting end creates a strong step limit with the inner wall of the countersunk hole and the channel opening, achieving a purely physical deadlock without the need for fasteners.

[0026] According to the law of electromagnetic induction, the damping torque generated by eddy currents is approximately proportional to the relative angular velocity. Therefore, this joint can achieve adaptive damping when facing impacts of different intensities without the need for sensors or controllers.

[0027] The working principle of this invention is as follows: When an external impact causes the core sphere 2 to generate an instantaneous angular velocity relative to the stator assembly, the static gradient magnetic field generated by the first magnet 5 and the second magnet 6 is cut by the core sphere 2. Since the core sphere is made of a non-magnetic, highly conductive material (such as aluminum alloy), eddy currents are generated inside. These eddy currents interact with the magnetic field, instantaneously generating a reverse electromagnetic torque proportional to the relative angular velocity, thereby achieving non-contact, efficient energy absorption and braking. This damping response is an inherent physical characteristic, and its response time is extremely short and negligible compared to traditional sensing and control links. Specifically, the magnet layout of this invention employs a Z-axis offset and Pythagorean theorem compensation design: the mounting slot 4 is located at 45°, 135°, 225°, and 315° circumferentially, and has a preset offset (e.g., ΔZ1=ΔZ2=2mm) relative to the equatorial plane of the core sphere in the axial direction. The spatial straight-line distance between adjacent magnets is calculated using the Pythagorean theorem (e.g., 15.5mm, approximately 1.3 times the magnet diameter), resulting in uniform magnetic field superposition and stable gradient magnetic field envelope strength. This optimized layout enables the magnetic flux change rate of the core sphere to exhibit good linearity within the main working rotation angle range, and the ratio of damping torque to angular velocity to remain constant, thereby achieving adaptive damping for impacts of different intensities.

[0028] When stationary or making low-speed fine-tuning adjustments, the damping torque mentioned above is generated only under dynamic conditions related to speed, resulting in extremely low mechanical friction in the system. Unlike traditional mechanical or hydraulic dampers, this joint has no static friction components, eliminating the "stickiness-slippage" phenomenon at the physical level and giving the robot extremely high motion reproduction accuracy and low-speed fine-tuning stability.

[0029] By integrating the end heat-fused anchoring structure of the flexible drive cable with the five-wire asymmetric anti-interference routing array within the stator assembly, five independent guide holes 7 penetrating the first base 1 and the second base 3 are used. Three of these holes are independently located in the three magnet gaps, while the other two are arranged side-by-side adjacent to each other in the fourth magnet gap (e.g., azimuth angles precisely set at 0°, 90°, 180°, 255°, and 285° respectively), effectively avoiding the magnet mounting slot 4. After passing through these guide holes, the flexible drive cable extends into the routing channel 8 inside the core sphere. Its end is heat-fused to form a heat-fused shrinkable limiting ball-shaped end, the outer diameter of which is larger than the inner diameter of the countersunk hole 9 on the surface of the core sphere (e.g., interference of 0.3mm). When the cable is under tension, the limiting ball head, the inner wall of the countersunk hole, and the port of the routing channel create a strong step-limiting effect, forming a purely physical deadlock without any fasteners. This structure achieves interference-free five-wire redundant drive and high-reliability cable fixation within a limited volume, significantly improving the reliability of the multi-degree-of-freedom flexible drive of the joint.

[0030] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A highly integrated passive impact-resistant flexible joint, characterized in that, include: A stator assembly comprising a first base (1) and a second base (3) disposed opposite to each other; The core sphere (2) is made of a non-magnetic, highly conductive material and is rotatably positioned between the first base (1) and the second base (3). It has a wiring channel (8) inside and a countersunk hole (9) on its surface that communicates with the wiring channel (8). The magnetic array assembly includes multiple first magnets (5) embedded in a first base (1) and multiple second magnets (6) embedded in a second base (3). The flexible transmission cable extends through the guide hole (7) on the first base (1) and the second base (3) to the wiring channel (8). Its end is a heat-melted shrinkable limiting ball head with an outer diameter larger than the inner diameter of the countersunk hole (9), forming physical interference and step limiting. The stator assembly is provided with five independent guide holes (7) that penetrate the first base (1) and the second base (3); The layout of the first magnet (5) and the second magnet (6) satisfies the following: the magnetic poles of adjacent magnets on the same base are opposite, and the magnetic poles of opposite magnets on the top and bottom are opposite; the mounting slot (4) is located at 45°, 135°, 225°, and 315°, and has a preset offset in the axial direction relative to the equatorial plane of the core sphere (2). This offset is calculated based on the geometric reference of spatial distance provided by the Pythagorean theorem and the superposition compensation of magnetic field to form a uniform gradient magnetic field envelope.

2. According to claim 1, the five guide holes (7) are distributed in the gap between adjacent magnet mounting slots (4), wherein three of the guide holes (7) are independently located in three gaps, and the other two guide holes (7) are arranged side by side in the remaining gap, forming an asymmetrical avoidance distribution.

3. The highly integrated passive impact-resistant flexible joint according to claim 1, characterized in that, The first magnet (5) and the second magnet (6) are N52 neodymium iron boron strong magnets.

4. The highly integrated passive impact-resistant flexible joint according to claim 1, characterized in that, The flexible transmission cable is a multi-strand braided PE wire, and the inner diameter of the guide hole (7) is larger than the outer diameter of the flexible transmission cable.

5. The highly integrated passive impact-resistant flexible joint according to claim 1, characterized in that, The air gap between the outer surface of the core sphere (2) and the first magnet (5) and the second magnet (6) is 0.8 mm.

6. The highly integrated passive impact-resistant flexible joint according to claim 1, characterized in that, The center azimuth angles of the five guide holes (7) are respectively set at 0°, 90°, 180°, 255° and 285°.

7. The highly integrated passive impact-resistant flexible joint according to claim 1, characterized in that, The interference between the inner diameter of the countersunk hole (9) and the outer diameter of the end of the flexible transmission cable is 0.3 mm.

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