Bionic robot leg anti-impact lightweight structure based on multistage fractal nesting

Abstract

The invention provides a bionic robot leg bone impact-resistant lightweight structure based on multistage fractal nesting, which comprises a hollow cylindrical main body, an annular reinforcing rib network and a nested fractal honeycomb layer, and through a Koch-Sierpinski composite fractal design, dynamic stiffness regulation and control and an asymmetric torsion-resistant strategy, the impact-resistant lightweight structure of the bionic robot leg bone is obtained. And the impact resistance, the torsional rigidity and the light weight level are obviously improved. Compared with a traditional structure, the energy absorption efficiency is improved, and the fatigue life is prolonged. Through axial pressure and torque simulation verification, the stress distribution uniformity is remarkably improved, and the method is suitable for a high-dynamic robot scene.

Description

Technical Field

[0001] The invention relates to the technical field of high-performance bionic structures, and in particular to an anti-impact lightweight structure of a bionic robot leg bone based on multi-level fractal nesting. Background Art

[0002] With the rapid development of robotics technology, the coordinated optimization of lightweight and impact resistance has become a core challenge to improve the mobility and durability of mobile robots. Traditional robot leg structures generally adopt homogeneous hollow cylinders or honeycomb sandwich designs (such as patent CN112606009B). Although they can achieve basic lightweight, they have problems such as excessive axis deformation and low energy absorption efficiency under high dynamic loads, which can easily lead to structural fatigue damage. For example, when the existing honeycomb sandwich structure is subjected to impact, the energy absorption efficiency is less than 4.2 J / g, and the symmetrical filling strategy makes it difficult to disperse the torsional load. The torsional stiffness is generally less than 180 N·m / rad, and the stress concentration factor is as high as 1.8 or more.

[0003] In nature, the hollow curved shape and trabecular gradient distribution characteristics of the ibex tibia can effectively disperse the peak stress of jumping impact; the Koch curve fractal structure of the beetle elytra prolongs the crack propagation path through multi-level geometric nesting, significantly improving the energy dissipation efficiency; and the collapse deformation mechanism of the kangaroo calcaneus achieves efficient absorption of impact energy. These biological characteristics provide important inspiration for the design of robot leg structures.

[0004] Although existing research has attempted to combine bionics to optimize the structure (such as the tension knee joint design proposed by Changchun University of Technology), there are still limitations such as a single energy absorption level and insufficient torsional performance. For example, the traditional honeycomb structure lacks multi-level fractal nesting and cannot achieve step-by-step dissipation of impact energy; the homogeneous filling strategy leads to a prominent contradiction between lightweight and strength, and the modular design can reduce weight but sacrifices impact resistance. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a multi-level impact-resistant lightweight structure for the leg bones of a bionic robot, aiming to solve the problems of insufficient deformation resistance and low energy absorption efficiency of existing lightweight structures under complex impact loads, while achieving coordinated optimization of high energy dissipation and lightweight through a multi-level fractal honeycomb design.

[0006] In order to realize the above technical features, the object of the present invention is achieved as follows: a bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting, comprising: Hollow cylindrical body: the cross-sectional area at both ends is larger than that in the middle, and the central axis has a vertical cylindrical hollow structure; Annular reinforcement rib network: formed by connecting upper and lower circular rings and inclined ribs, dividing each layer inside the main body into six equilateral triangle areas; Nested fractal honeycomb layers, including: Main honeycomb structure: regular hexagonal units are arranged periodically, with a unit side length of L h =3-8mm, its thickness is one tenth of the unit side length; Secondary fractal honeycomb: embedded in the center and vertices of the main honeycomb, using the Koch curve fractal configuration, the ratio of its side length to the main structure is 0.618.

[0007] Preferably, the fractal iteration number of the Koch curve fractal configuration is ≥2, and the fractal angle θ=60°.

[0008] Preferably, the vertical cylindrical hollow structure of the hollow cylindrical body is filled with different areas from bottom to top, specifically including: Distal buffer contact area: The inner wall is provided with a spiral collapse guide groove, and the groove depth is 30%-50% of the wall thickness; Middle backbone area: interval filling with secondary fractal honeycomb, three filling areas are distributed periodically at 120°; Proximal joint area: fully filled with main honeycomb structure.

[0009] Preferably, the hexagonal side length of the main honeycomb structure filled in the annular reinforcement rib network is L h , the side length of the triangle is L t , meet 0.4L t ≤L h ≤ 1.2 L t , and the three sides of the hexagon are parallel to the three sides of the triangle formed by the annular reinforcement network.

[0010] Preferably, the diameter D of the hexagonal inscribed circle of the main honeycomb structure is h The diameter D of the inscribed circle of the triangle formed by the annular reinforcement network t Satisfy D h =0.6D t .

[0011] Preferably, the secondary fractal honeycomb is a hexagonal structure, and its secondary side length L h2 =0.3L h , and the secondary hexagon vertices are aligned with the midpoints of the primary hexagon edges.

[0012] Preferably, the energy absorption mechanism of the nested fractal honeycomb layer includes: Primary energy dissipation: The main honeycomb structure absorbs 60%-70% of the impact energy; Secondary energy dispersion: The secondary fractal honeycomb disperses the remaining energy through fractal branch fractures.

[0013] The present invention has the following beneficial effects: 1. The present invention uses a multi-level energy absorption mechanism of nested fractal honeycomb layers (main honeycomb buckling, fractal branch fracture, micropore compression) to achieve an energy absorption efficiency of 6.8 J / g, which is 62% higher than that of traditional honeycomb structures, effectively avoiding structural fatigue or damage under dynamic impact.

[0014] 2. The present invention combines a hollow cylindrical body with a gradient filling strategy (full filling at the proximal end and hollow at the distal end), which reduces the overall weight by 28% and achieves a specific strength of 140 MPa•cm³ / g, taking into account both lightweight and high load-bearing requirements.

[0015] 3. The present invention forms an asymmetric torsional support system by periodically filling fractal honeycombs at 120° in the middle backbone area, and the torsional stiffness is increased to 280 N•m / rad, and the stress concentration coefficient is ≤1.3, which is significantly better than the traditional symmetrical structure (180 N•m / rad, coefficient ≥1.8).

[0016] 4. The present invention uses the synergistic effect of the design of thick ends and fractal honeycomb layout. The simulation results show that the uniformity of stress distribution under axial pressure and torsional load is improved by 40% and 50% respectively, and the maximum stress peak is reduced by 35% (compared with the traditional cylindrical structure).

[0017] 5. The present invention supports partial replacement through modular partition design (proximal, middle, and distal), shortening maintenance time by 50% and reducing life cycle costs by 25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] Figure 1 It is a schematic diagram of the bionic process of the lightweight structure of the robot leg imitating the tibia of the blue sheep of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of the middle annular reinforcement rib of the present invention.

[0021] Figure 3 The present invention is a schematic diagram of a bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting and three different middle filling structures.

[0022] Figure 4 It is a complete schematic diagram of the middle filling structure of the present invention.

[0023] Figure 5 It is a schematic diagram of the plane expansion of the honeycomb filling structure of the present invention.

[0024] Figure 6 It is a deformation diagram of the non-bending structure and the invented lightweight structure of the robot limb leg imitating the tibia of the blue sheep when subjected to a 1Mpa pressure in the lateral direction at the same time.

[0025] Figure 7 Comparison chart of the non-bending structure and the lightweight structure of the robot leg invented to imitate the tibia of the blue sheep when subjected to 1Mpa positive pressure at the same time.

[0026] In the figure: a hollow cylindrical body 1, an annular reinforcement rib network 2, upper and lower rings 21, and inclined ribs 22, a nested fractal honeycomb layer 3, a main honeycomb structure 31, a secondary fractal honeycomb 32, a distal buffer contact area 4, a middle backbone area 5, and a proximal joint area 6. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Embodiment 1: See also Figure 1 The present invention is inspired by the tibia of the blue sheep. The main shape characteristics of the blue sheep tibia are refined and simplified. The cross-section is a cylinder that gradually shrinks from both ends to the center. A graded honeycomb structure is designed in the hollow interior to imitate the characteristics of biological leg bones. While ensuring the structural strength, the structure is lightweight.

[0032] Embodiment 2: See also Figure 1-5 , a bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting, including: a hollow cylindrical body 1: the cross-sectional area of ​​the two ends is larger than the middle part, and the central axis is provided with a vertical cylindrical hollow; the vertical hollow axis is designed in this way to provide additional collapse space, which is suitable for high-impact scenes (such as jumping, falling) The hollow main body of the annular reinforcement network 2 and the annular reinforcement ribs 22 simulate the hollow gradient structure of the ibex tibia, reducing the overall weight by 28%: it is formed by connecting the upper and lower rings 21 and the inclined ribs 22, dividing six equilateral triangle areas; nested fractal honeycomb layer 3: the main honeycomb structure 31 and the secondary fractal honeycomb 32 form a multi-level impact resistance system. The fractal honeycomb absorbs energy in layers (the main honeycomb is bent and the fractal branches are broken), and the energy absorption efficiency is improved; See also Figure 3 The hollow part is divided from bottom to top into: a distal buffer contact area 4, a middle backbone area 5, and a proximal joint area 6. This design of full proximal filling improves fatigue resistance, asymmetric filling in the middle section enhances torsional rigidity, and significantly improves the distal energy absorption efficiency; at the same time, the gradient filling strategy balances lightweight and strength requirements; Furthermore, the hexagonal side length of the main honeycomb structure 31 is L h , the side length of the triangle is L t , meet 0.4L t ≤L h ≤ 1.2 L t , and the three sides of the hexagon are parallel to the three sides of the triangle formed by the annular reinforcement network 2. Thus, the collinear edges form a continuous load path, the interface stress concentration is reduced, and the bending efficiency is improved.

[0033] Furthermore, the diameter D of the hexagonal inscribed circle of the main honeycomb structure 31 is h The diameter D of the incircle of the triangle t Satisfy D h =0.6D t The inscribed circle ratio is 0.6:1 to simulate the gradient distribution of trabecular density, which improves the uniformity of stress dispersion; the hexagonal filling density is adapted to the triangular area, reducing redundant materials.

[0034] Furthermore, the hexagonal structure 32 is nested inside the hexagonal structure, and the secondary side length L h2 =0.3L h , and the secondary vertices are aligned with the midpoints of the main hexagonal edges. This design is fractal energy absorption strengthening: the secondary hexagons extend the crack propagation path and the energy absorption is hierarchical; the nested design inhibits the initiation of microcracks and prolongs the fatigue life.

[0035] Embodiment 3: In order to verify the performance of the anti-impact lightweight structure of the leg bone of a bionic robot based on multi-level fractal nesting in the present invention, a corresponding comparative test is provided. Figure 6-7 .

[0036] When a uniform pressure of 100 MPa is applied axially, the comparison between the spacing filling structure of the present invention and the annular non-hollow structure of the same height shows: uniformity of stress distribution and optimization of strain response: under the same load, the strain gradient of the spacing filling structure is 30% smoother than that of the annular non-hollow structure, indicating that its buffering capacity for impact energy is significantly enhanced; the spacing filling strategy reduces material usage by 15%, while the stiffness loss is only 5%, and the specific strength is improved.

[0037] When applying 10N·mm -1 During torque, stress-strain analysis of the two groups of structures showed that the uniformity of shear stress distribution in the gap filling structure was improved by 40%, and the asymmetric support of the gap filling area reduced the torsion angle and increased the torsional stiffness.

[0038] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting, characterized in that: include: Hollow cylindrical body (1): the cross-sectional area of ​​the two ends is larger than that of the middle part, and the central axis has a vertical cylindrical hollow structure; Annular reinforcement rib network (2): formed by connecting upper and lower circular rings (21) and inclined ribs (22), dividing each layer inside the main body into six equilateral triangle areas; Nested fractal honeycomb layer (3), including: Main honeycomb structure (31): regular hexagonal units are arranged periodically, with a unit side length of L h =3-8mm, its thickness is one tenth of the unit side length; Secondary fractal honeycomb (32): embedded in the center and vertex of the main honeycomb, using the Koch curve fractal configuration, the ratio of its side length to the main structure is 0.

618.

2. According to claim 1, a bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting, characterized in that: The fractal iteration number of the Koch curve fractal configuration is ≥2, and the fractal angle θ=60°.

3. The bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting according to claim 1, characterized in that: The vertical cylindrical hollow structure of the hollow cylindrical body (1) is filled with different areas from bottom to top, specifically including: Distal buffer contact area (4): a spiral collapse guide groove is provided on the inner wall, and the groove depth is 30%-50% of the wall thickness; Middle backbone area (5): interval filling secondary fractal honeycombs (32), three filling areas are distributed periodically at 120°; Proximal joint region (6): fully filled with main honeycomb structure (31).

4. The bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting according to claim 1, characterized in that: The main honeycomb structure (31) filled in the annular reinforcement rib network (2) has a hexagonal side length of L. h , the side length of the triangle is L t , meet 0.4L t ≤L h ≤ 1.2 L t , and the three sides of the hexagon are parallel to the three sides of the triangle formed by the annular reinforcement network (2).

5. The bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting according to claim 1, characterized in that: The main honeycomb structure (31) has a hexagonal inscribed circle diameter D h The diameter D of the inscribed circle of the triangle enclosed by the annular reinforcement network (2) t Satisfy D h =0.6D t .

6. The bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting according to claim 1, characterized in that: The secondary fractal honeycomb (32) is a hexagonal structure, and its secondary side length L h2 =0.3L h , and the secondary hexagon vertices are aligned with the midpoints of the primary hexagon edges.

7. The bionic robot leg bone impact-resistant lightweight structure based on multi-level fractal nesting according to claim 1, characterized in that: The energy absorption mechanism of the nested fractal honeycomb layer (3) includes: Primary energy dissipation: the main honeycomb structure (31) absorbs 60%-70% of the impact energy; Secondary energy dispersion: The secondary fractal honeycomb (32) disperses the remaining energy by fractal branch fractures.

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