A low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics

Abstract

This solution belongs to the field of low-frequency vibration isolation technology and discloses a low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics. It includes a vertically arrayed multi-layer vibration isolation unit, with each layer comprising multiple horizontally arrayed unit cells. Each unit cell includes a horizontally arranged first platform and second platform, and a first spring, a second spring, a third spring, and four sets of connecting rods disposed between the first and second platforms. Each layer of vibration isolation unit has different unit cell parameters, enabling the low-frequency vibration isolation device to have continuous quasi-zero stiffness characteristics. The unit cell parameters include the length l1 and stiffness k1 of the first spring, the stiffness k2 of the second spring, and the length l3 and stiffness k3 of the third spring.

Description

Technical Field

[0001] This solution belongs to the field of low-frequency vibration isolation technology, specifically involving a low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics. Background Technology

[0002] Isolating undesirable vibrations is of paramount importance in many engineering structures and precision equipment. In particular, isolating micro-vibrations in orbiting satellites, optical components, and space telescopes has always been a challenge. From a passive vibration isolation perspective, one of the most common methods is to utilize traditional linear passive vibration isolators. However, linear passive vibration isolators only work when the frequency is more than 2 times the natural frequency. 0.5 Vibrations several times stronger than normal are required for effective isolation. To achieve better vibration isolation performance, isolators can reduce their stiffness to lower the resonant frequency, but this also reduces the structure's load-bearing capacity, making it unable to support the load of the isolated object itself. Therefore, directly using a near-linear, low-stiffness system cannot achieve ultra-low frequency vibration isolation.

[0003] To overcome this drawback, researchers have attempted to design isolators with nonlinear characteristics to improve ultra-low frequency vibration isolation performance. For vibration isolation or suppression, ideal stiffness not only needs to withstand large static loads but also possess extremely low dynamic stiffness, i.e., quasi-zero stiffness (QZS) with high static and low dynamic stiffness characteristics. Observing the force-displacement curve, QZS is a quasi-plateau interval on the curve, indicating that the force remains almost constant within this displacement range. Quasi-zero stiffness can achieve good low-frequency vibration isolation without affecting load-bearing capacity, thus resolving the contradiction between load and low-frequency vibration isolation.

[0004] Traditional nonlinear isolators typically achieve optimal isolation performance only within a small range of isolation masses. However, in engineering applications, the mass of the isolation target often varies randomly. For example, surgical transfer beds are frequently subjected to mechanical vibrations from ambulances or roads during transport, which can easily cause irreversible damage to patients, especially those with brain injuries and newborns whose bodies are not yet fully developed. The patients using surgical transfer beds are unpredictable, with varying weights, but generally within a certain range. Currently, addressing the random variation of the isolation target mass within a large range remains a significant challenge. Therefore, developing a vibration isolation device that can effectively reduce low-frequency vibrations under a large range of randomly varying isolation masses is extremely urgent. Summary of the Invention

[0005] This solution aims to overcome at least one deficiency in the existing technology and provide a low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics to solve the problem of narrow effective load range and only being able to function as a single vibration isolator.

[0006] To solve the above-mentioned technical problems, the following technical solution is adopted:

[0007] A low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics includes a vertically arrayed multi-layer vibration isolation unit, each layer comprising a horizontally arrayed multiple unit cells. Each unit cell includes a horizontally arranged first platform and a second platform, and a first spring, a second spring, a third spring, and four sets of connecting rods disposed between the first and second platforms. The unit cell has a vertical central axis, and the four sets of connecting rods are distributed at equal angles around the central axis of the unit cell. Each set of connecting rods includes a first inclined rod and a second inclined rod, one end of which is hinged to each other to form a joint. The other end of the first inclined rod is hinged to the first platform, and the other end of the second inclined rod is hinged to the second platform. The first spring is horizontally arranged, with its two ends connected to the joints of the two opposing sets of connecting rods. The second spring is vertically arranged, with its two ends connected to the centers of the first and second platforms, respectively. The third spring is coaxially disposed outside the second spring, with one end connected to the second platform and the other end free. Each layer of vibration isolation unit has different unit cell parameters, giving the low-frequency vibration isolation device continuous quasi-zero stiffness characteristics; the unit cell parameters include the length l1 and stiffness k1 of the first spring, the stiffness k2 of the second spring, and the length l3 and stiffness k3 of the third spring.

[0008] This solution proposes and implements a highly adaptable low-frequency vibration isolation device, composed of three mechanical elements: a plate, a rod, and a linear spring. A broad design space for mechanical behavior is achieved through series and parallel mechanical unit cells. The isolation device, composed of layers with different unit cell parameters, exhibits QZS characteristics with continuous effective load, demonstrating excellent low-frequency vibration isolation performance even with randomly varying isolation masses over a relatively large range. Experiments prove that the isolation device can achieve low-frequency vibration isolation over a wide range of isolation masses. It is important to note that when the number of layers is sufficiently large, the QZS region widens further, i.e., the effective load range of QZS expands. Therefore, a single isolation device can effectively isolate objects with random masses over a certain wide range. The on-site rapid reverse engineering strategy provides a fast solution to meet various demanding isolation requirements.

[0009] When the length l1 of the first spring in each layer of vibration isolation unit is the same, the stiffness of the first spring in the first to third layers of vibration isolation units arranged sequentially from top to bottom preferably satisfies: k 11 <k 12 <k 13 And k 12 <k 13 <2k 11 More preferably, satisfying: k 11 :k 12 :k 13 =186:260:306; The optimal solution satisfies: k 11 =0.186 N / mm, k 12=0.260 N / mm, k 13 = 0.306 N / mm.

[0010] Assuming the length l2 of the second spring is the same in each layer of vibration isolation units, the stiffness of the second spring of the first to third layers of vibration isolation units arranged sequentially from top to bottom preferably satisfies: 3k 22 <3k 23 <k 21 And 4K 22 <k 21 <4k 23 More preferably, satisfying: k 21 :k 22 :k 23 =220:45:73; The optimal solution satisfies: k 21 =0.220 N / mm, k 22 =0.045 N / mm, k 23 =0.073 N / mm.

[0011] When the stiffness k3 of the third spring in each layer of vibration isolation unit is the same, the length of the third spring in the first to third layers of vibration isolation units arranged sequentially from top to bottom preferably satisfies: l 31 >l 32 >l 33 And 2l 32 >2l 33 >l 31 More preferably, satisfying: l 31 :l 32 :l 33 =28:24:18; The optimal solution satisfies: l 31 =28mm, l 32 =24mm, l 33 =18mm.

[0012] Compared with existing technologies, this solution has the following advantages: by connecting and paralleling unit cells with specific structures and parameters, this solution can achieve low-frequency vibration isolation of quasi-zero stiffness effective loads in a continuous range. Attached Figure Description

[0013] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this solution. To better illustrate the solution, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0014] Figure 1 This is a schematic diagram of a low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics.

[0015] Figure 2 This is a schematic diagram of a single cell.

[0016] Figure 3 This is the design of a vibration isolation device with on-site adjustable continuous quasi-zero stiffness characteristics. (a) shows the unit cell structure; (b) shows the force-displacement curve corresponding to the unit cell (the highlighted bar represents the quasi-plateau segment, i.e., the quasi-zero stiffness range); (c) shows the structure of the vibration isolation device; (d) shows the force-displacement curve corresponding to the vibration isolation device; (e) shows a schematic diagram of the vibration isolation mass under random variation within a certain large range; (f) shows the excitation acceleration response and output acceleration response curves acquired by the dynamic signal acquisition system (DH5922D) (when the isolated mass corresponds to the quasi-zero stiffness range of the vibration isolation device, the vibration will be almost completely isolated by the vibration isolation device).

[0017] Figure 4 It is the quasi-static loading mechanical behavior of the vibration isolation device 4[S1,S2,S3]T as measured experimentally and predicted numerically.

[0018] Figure 5 The vibration transmittance curves of the vibration isolation device 4[S1,S2,S3]T under five typical support masses were obtained experimentally, where three support masses correspond to the QZS effective load.

[0019] Explanation of reference numerals in the attached drawings: vibration isolation unit 100, unit cell 110, first platform 111, second platform 112, first spring 113, second spring 114, third spring 115, first inclined rod 116, second inclined rod 117. Detailed Implementation

[0020] like Figure 1 As shown, this solution proposes a low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics, comprising a vertically arrayed multi-layer vibration isolation unit 100, each layer of the vibration isolation unit 100 comprising a horizontally arrayed plurality of unit cells 110. Figure 2As shown, each unit cell 110 includes a horizontally arranged first platform 111 and second platform 112, and a first spring 113, a second spring 114, a third spring 115, and four sets of connecting rods disposed between the first platform 111 and the second platform 112. The unit cell 110 has a vertical central axis, and the four sets of connecting rods are distributed at equal angles around the central axis of the unit cell 110. Each set of connecting rods includes a first inclined rod 116 and a second inclined rod 117, one end of which is hinged to each other to form a joint. The other end of the first inclined rod 116 is hinged to the first platform 111, and the other end of the second inclined rod 117 is hinged to the second platform 112. The first spring 113 is horizontally arranged, with its two ends connected to the joints of the two opposing sets of connecting rods. The second spring 114 is vertically arranged, with its two ends connected to the center of the first platform 111 and the center of the second platform 112, respectively. The third spring 115 is coaxially disposed outside the second spring 114, with one end connected to the second platform 112 and the other end free. Each layer of vibration isolation unit 100 has different unit cell 110 parameters, so that the low-frequency vibration isolation device has continuous quasi-zero stiffness characteristics; the unit cell 110 parameters include the length l1 and stiffness k1 of the first spring 113, the stiffness k2 of the second spring 114, and the length l3 and stiffness k3 of the third spring 115.

[0021] The aforementioned low-frequency vibration isolation device is composed of series and parallel connections of unit cells with specific structures and parameters, enabling low-frequency vibration isolation with quasi-zero stiffness effective load over a continuous range. The intermediate layer vibration isolation unit can use the second platform of the upper layer vibration isolation unit as the first platform, or the first platform of the lower layer vibration isolation unit as the second platform. In adjacent layers of vibration isolation units, the second platform of the upper layer vibration isolation unit and the first platform of the lower layer vibration isolation unit are combined into one.

[0022] To enable those skilled in the art to better understand this solution, a more detailed description is provided below.

[0023] The core idea of ​​constructing vibration isolation devices with multiple extremely low stiffness characteristics, such as... Figure 3 As shown. Considering the important role of high static and low dynamic stiffness characteristics in low-frequency vibration isolation, this implies a force-displacement curve with a quasi-plateau within a certain loading range. Our primary task is to develop a novel vibration isolation device with deformation stability, whose load response curve fully conforms to the desired "larger range of quasi-plateau" characteristics. To achieve this, a novel polyhedral unit cell is formed by two plates with side length a2 connected by four pairs of links, as shown. Figure 3 As shown in (a). Each pair of links consists of two diagonal rods of length a1 connected by a shaft hole and attached to the plate in the same manner. A horizontal spring (spring 1) of length l1 is connected at the intermediate joint of the two pairs of links. Figure 3 (a) Joints 1 and 2). When the element is loaded to a certain extent, spring 1 will cause the element to exhibit negative stiffness characteristics. Figure 3(b) Orange curve). A vertical spring (spring 2) connects to the center of the upper and lower plates. A shorter, larger-diameter spring 3 is connected to the lower plate and nested outside spring 2. Springs 2 and 3 will exhibit positive stiffness characteristics under vertical loads. Under a given load, the positive stiffness provided by vertical spring 2 ( Figure 3 (b) The dark green curve and the negative stiffness provided by the horizontal spring 1 cancel each other out, allowing QZS to operate over a large displacement range (see...). Figure 3 (b) Columnar highlighted area). Spring 3 can provide more positive stiffness in the vertical direction, thus preventing the unit cell from entering negative stiffness during further deformation. Therefore, the spring parameters are one of the key elements that the unit cell needs to be carefully designed. By changing the spring parameters, the effective load of the unit cell (i.e., the load range from the start to the end of QZS) and the displacement range of QZS can be adjusted.

[0024] Different units are assembled by series and parallel connections (see...) Figure 3 (c) This allows for a wider range of stiffness tuning behavior. The plates and rods of the vibration isolation device are manufactured using additive manufacturing with curable resin. Cells in the same layer are connected together using the same stainless steel rods as hinges to ensure the stability of the vibration isolation device. Rubber sleeves are installed at both ends of the stainless steel rods to maintain the tightness of the hinges. Since the deformation of each layer is discrete and has the ability to deform independently, when assembled in parallel, its effective load increases in multiples of the number of parallel cells. In the series assembly method, the force on all layers is equal to the external force, and the deformation of each layer is the total deformation. The parallel and series relationships in the structural topology and the unit cells with load curves of quasi-platform shape are crucial for realizing rich stiffness behavior concepts and can produce rich stiffness behaviors. The combination of parallel and series assembly methods allows for a wider range of stiffness tuning of the vibration isolation device. The QZS effective load can be adjusted by the number of cells in each layer and the bearing capacity of each unit cell, and the QZS displacement range can be adjusted by the number of layers and the QZS displacement range of each unit cell. For example, when there is a gentle gradient between multiple layers, a force-displacement curve with zero stiffness can be obtained over a large force range. Figure 3 (d) Under the condition that the vibration isolation quality varies randomly within a certain range, the multi-cell vibration isolation device also remains within the QZS region. Figure 3 (e) demonstrates excellent low-frequency vibration isolation performance. The force-displacement curve of the quasi-platform represents an ideal stiffness characteristic for achieving low-frequency vibration attenuation without sacrificing loading capacity. When the mass of the isolated object is within the effective load range, the ultra-low dynamic stiffness of the vibration isolation device perfectly isolates harmful vibrations, such as... Figure 3 As shown in (f).

[0025] To fully demonstrate the rich QZS behavior of this vibration isolation device, this paper mainly uses three elements S1, S2, and S3 with different parameters to construct the vibration isolation device, as shown in Table 1 (k1, k2, and k3 represent the stiffnesses of springs 1, 2, and 3). The vibration isolation device consists of elements S1, S2, and S3 from top to bottom, with each layer containing 4 cells, as shown in Table 1. Figure 3 As shown in (c), the sample is named 4[S1,S2,S3]T. A uniaxial quasi-static compression test was conducted on the vibration isolation device sample 4[S1,S2,S3]T using a testing machine. The experiment was controlled using a displacement loading method, with a constant displacement rate of 5 mm / min. The reaction force and displacement response of the sample were captured, thus obtaining the force-displacement curve, as shown in (c). Figure 4 and 5 As shown.

[0026] Table 1 Geometric parameters of the unit cell constituting the vibration isolation device

[0027]

[0028] The loading curves corresponding to vibration isolation device 4[S1,S2,S3]T are as follows: Figure 4 As shown, the stiffness-displacement curve is derived from the force-displacement curve. A stiffness of v = 0.1 N / mm is quantitatively chosen as the threshold (i.e., stiffness 0–0.1 N / mm) to define the QZS region. The vibration isolation device gradually achieves three quasi-plateaus on the force-displacement curve. Therefore, the effective load and QZS displacement range of the vibration isolation device are determined by the mechanical properties of the unit. Based on the effective stiffness of the unit in each layer, it is entirely conceivable that the vibration isolation device reaches the QZS plateau sequentially from small to large. In general, the force-displacement curve exhibits a slight stepped QZS characteristic. It can be observed that their quasi-zero stiffness interval is continuous, which greatly widens the quasi-zero stiffness range of the vibration isolation device. The effective load range is superimposed at 4.0–5.9 N, and the QZS displacement range is as high as 32.5 m. The effective load range and QZS displacement range of the vibration isolation device are three times that of ordinary multi-layer vibration isolation devices. When the number of layers is sufficient, the effective load and QZS displacement range will be expanded indefinitely, so only one vibration isolation system is needed to effectively isolate objects of almost all masses at low frequencies.

[0029] To verify the vibration isolation performance of the vibration isolation device 4[S1,S2,S3]T under objects with a large mass range, the vibration transmission rate of the vibration isolation device under five typical support masses was obtained, such as... Figure 5 As shown. The supporting masses M1 = 223g, 478g, 547g, 589g and 792g, respectively, correspond to Figure 4Points A′, B′, C′, D′, and E′ are included, with B′, C′, and D′ falling within the QZS range. From a support mass of 478g (B′) to M1 = 589g (D′), the effective isolation frequency band starts at 2.6Hz, 2.8Hz, and 2.8Hz, respectively. When the excitation frequency increases to 10Hz, the transmission rate decreases to -22.0dB, -19.2dB, and -11.4dB, respectively. When the support mass is M1 = 223g (A′) and 792g (E′), the vibration isolation device only begins to suppress vibration after the excitation frequency exceeds 1.89Hz and 2.11Hz, respectively, both higher than the initial isolation frequencies for the above load masses (M1 = 478g (B′), 547g (C′), 589g (D′)). This indirectly indicates that within the mass range of 478–589g, the proposed vibration isolation device exhibits good low-frequency vibration isolation performance. This further verifies that the vibration isolation device can indeed isolate objects with a large range of continuously varying mass, and is not limited to objects with a small mass range.

[0030] In summary, we proposed and experimentally implemented a highly adaptable vibration isolation device based on rod and spring connections for low-frequency vibration isolation. This device allows for a vast customization space for its force-displacement curve, exhibiting a continuous effective load QZS characteristic (i.e., a large QZS effective load range), thus achieving excellent low-frequency vibration isolation performance for objects with random masses over a wide range. Furthermore, the required vibration isolation device can be rapidly reverse-engineered on-site according to the needs of the isolated object and the excitation amplitude. Notably, the proposed device's unique mechanical behavior customization strategy enables tailored mechanical behavior, opening new avenues for various engineering applications such as automotive suspensions, vibration isolation brackets, and operating tables.

[0031] Obviously, the above embodiments of this solution are merely examples for clearly illustrating this solution, and are not intended to limit the implementation of this solution. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this solution should be included within the scope of protection of the claims of this solution.

Claims

1. A low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics, characterized in that, The low-frequency vibration isolation device includes a vertically arrayed multi-layer vibration isolation unit, each layer comprising multiple horizontally arrayed unit cells. Each unit cell includes a horizontally arranged first platform and second platform, and a first spring, a second spring, a third spring, and four sets of connecting rods disposed between the first and second platforms. The unit cell has a vertical central axis, and the four sets of connecting rods are distributed at equal angles around the central axis of the unit cell. Each set of connecting rods includes a first inclined rod and a second inclined rod, one end of which is hinged to each other to form a joint. The other end of the first inclined rod is hinged to the first platform, and the other end of the second inclined rod is hinged to the second platform. The first spring is horizontally arranged, with its two ends connected to the joints of the two opposing sets of connecting rods. The second spring is vertically arranged, with its two ends connected to the center of the first platform and the center of the second platform, respectively. The third spring is coaxially arranged outside the second spring, with one end connected to the second platform and the other end free. Vibration isolation units in the same layer have the same unit cell parameters, while vibration isolation units in different layers have different unit cell parameters, giving the low-frequency vibration isolation device continuous quasi-zero stiffness characteristics; the unit cell parameters include the length of the first spring. l 1n and stiffness k 1n Stiffness of the second spring k 2n and the length of the third spring l 3n and stiffness k 3n ,in n This represents the number of layers of vibration isolation units from top to bottom; The length of the first spring in each vibration isolation unit l 1n Similarly, the stiffness of the first spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies: k 11 < k 12 < k 13 and k 12 < k 13 <2 k 11 The stiffness of the first spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies: k 11 : k 12 : k 13 =186: 260: 306; The length of the second spring in each vibration isolation unit l 2n Similarly, the stiffness of the second spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies: 3 k 22 <3 k 23 < k 21 And 4 k 22 < k 21 <4 k 23 The stiffness of the second spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies the following: k 21 : k 22 : k 23 =220: 45: 73; Stiffness of the third spring in each vibration isolation unit k 3n Similarly, the lengths of the third springs in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfy the following: l 31 > l 32 > l 33 And 2 l 32 >2 l 33 > l 31 The lengths of the second springs in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfy the following: l 31 : l 32 : l 33 =28: 24:

18.

2. The low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics according to claim 1, characterized in that, The stiffness of the first spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies: k 11 =0.186 N / mm, k 12 =0.260 N / mm, k 13 =0.306 N / mm.

3. The low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics according to claim 1 or 2, characterized in that, The stiffness of the second spring in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfies: k 21 =0.220 N / mm, k 22 =0.045 N / mm, k 23 =0.073 N / mm.

4. The low-frequency vibration isolation device with continuous quasi-zero stiffness characteristics according to claim 1 or 2, characterized in that, The lengths of the second springs in the first to third layers of vibration isolation units, arranged sequentially from top to bottom, satisfy the following: l 31 =28 mm, l 32 =24 mm, l 33 =18 mm.

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