Mechanical signal modulation device

Abstract

The scheme belongs to the technical field of structural mechanics, and discloses a mechanical signal regulation and control device. The device comprises a metamaterial rod with a mechanical signal input end and an output end and a mechanical signal receiver connected to the mechanical signal output end. The metamaterial rod comprises an even number of guide rods arranged symmetrically and a plurality of cells linearly arranged on the guide rods. In the mechanical signal input direction, the first cell can be regulated or replaced with a first cell element or a second cell element, and the second to last cell is a second cell element. The stiffness of the first cell element is smaller than that of the second cell element. When the first cell is regulated or replaced with the first cell element, the mechanical signal receiver receives the mechanical signal after turning over or screening. When the first cell is regulated or replaced with the second cell element, the mechanical signal receiver receives the mechanical signal after attenuation. By using the external friction and the non-uniform distribution of the cell element with the stiffness softening effect, the turning over and screening functions of the elastic wave are realized, and by adjusting the first cell to open or close these functions, the mechanical signal is regulated and controlled.

Description

Technical Field

[0001] This solution belongs to the field of structural mechanics technology, specifically involving a mechanical signal control device. Background Technology

[0002] A long-standing challenge facing basic and applied sciences is designing new tools to manipulate physical signals. Building materials are achieving unprecedented properties unattainable by traditional materials. Significant progress has been made in recent years in the construction of building materials with properties determined by structure rather than composition, in the search for materials with novel properties. Through ingenious structural design, not only can metamaterials with anomalous static mechanical properties such as negative Poisson's ratio, negative compressibility, compression-torsion coupling, and programmability be obtained, but the propagation of elastic waves can also be manipulated, leading to many novel applications such as unidirectional propagation, transition waves, filtering, and mechanical signal logic gates. However, altering the tensile or compressive properties of elastic waves, and filtering out a single waveform from a mixture of tensile and compressive elastic waves to achieve a function similar to that of an electronic diode rectifying alternating current, remains difficult. In classical wave theory, a localized stress disturbance propagates to the undisturbed region. Although the propagation process may weaken the disturbance due to energy dissipation, it does not change the fundamental properties of the disturbance: compression of the input results in compression of the output; tension of the input results in tension of the output. Systems with stiffness-softening effects have been designed to convert compression pulses into leading rarefaction waves and decaying oscillating waves, allowing stress waves to decay independently of plasticity and damping. Although the output is primarily a tensile wave, according to the law of conservation of momentum, internal forces do not change the system's momentum, and the total output momentum will eventually equal the input momentum. Therefore, the presence of compression waves in the output is unavoidable, making it impossible to completely alter the properties of elastic waves. Other fields utilize nonlinear methods to modify functionality. Summary of the Invention

[0003] This solution aims to overcome at least one deficiency in the prior art and provide a mechanical signal control device.

[0004] To solve the above-mentioned technical problems, the following technical solution is adopted:

[0005] A mechanical signal control device includes a metamaterial rod having a mechanical signal input end and an output end, and a mechanical signal receiver connected to the mechanical signal output end; the metamaterial rod includes an even number of symmetrically arranged guide rods and a plurality of cells linearly arranged on the guide rods; along the mechanical signal input direction, the first cell can be controlled or replaced to be a first cell element or a second cell element, and the second to the last cells are all second cell elements; the stiffness of the first cell element is less than the stiffness of the second cell element;

[0006] Both the first and second cells include a first connecting plate, a second connecting plate, a first diagonal rod, a second diagonal rod, a third diagonal rod, a fourth diagonal rod, and a spring. The first and second connecting plates are parallel to each other. The first ends of the first and second diagonal rods are pivotally connected to the side of the first connecting plate facing the second connecting plate. The first ends of the third and fourth diagonal rods are pivotally connected to the side of the second connecting plate facing the first connecting plate. The second ends of the first and third diagonal rods are pivotally connected to the first end of the spring. The second ends of the second and fourth diagonal rods are pivotally connected to the second end of the spring. In adjacent cells, the second connecting plate of the preceding cell and the first connecting plate of the following cell are shared or connected as a single unit. The first and second connecting plates are provided with an even number of through holes for the guide rod to pass through. The mechanical signal receiver is connected to the second connecting plate of the last cell.

[0007] When the first cell is regulated or replaced by the first cell, the mechanical signal receiver receives the mechanical signal that has been flipped or filtered; when the first cell is regulated or replaced by the second cell, the mechanical signal receiver receives the mechanical signal that has been attenuated.

[0008] This scheme utilizes external friction and the non-uniform distribution of cells with a stiffness-softening effect to achieve the flipping and filtering function of elastic waves. By adjusting the first cell to open or close these functions, the mechanical signal can be controlled. Specifically, when the first cell is adjusted or replaced by the first cell element, the cells of the metamaterial rod are non-uniformly arranged. Combined with the frictional force between the cells and the guide rod, the momentum conservation of the multi-cell system is broken, thus achieving the unusual function of outputting only tensile waves. Regardless of whether an impact, sudden tension, or alternating tension and compression loads are applied to one end, only the tensile signal is output at the other end of the rod. This means that this material rod can completely flip compressive stress waves into tensile waves and can filter out tensile waves from waves subjected to mixed tensile and compressive loading. Therefore, the mechanical signal receiver will receive the flipped or filtered mechanical signal. It is worth noting that the metamaterial rod exhibits unidirectional (non-dissimilarity) behavior in its unique flipping and filtering function of elastic waves. Similar non-dissimilarity has shown strong application prospects in acoustics, optics, and mechanics. More importantly, we have found the key cell unit that controls these peculiar functions—the first cell unit, like a key gene switch on the DNA chain of a organism, can turn these functions on or off by adjusting the performance of this key cell unit, which opens up a powerful and designable platform for the manipulation of mechanical signals.

[0009] When the first cell is modulated or replaced by the second cell, the efficiency of converting the compression wave into the stretching wave in the first and second cells is not high. The converted stretching wave is quickly dissipated by friction, leaving only the incompletely attenuated compression wave at the output. Similarly, when a mixed waveform is input, the compression wave transmitted to the second cell has greater energy and will be output together with the stretching wave at the output. Therefore, the mechanical signal receiver will receive the attenuated mechanical signal and cannot achieve the elastic wave reversal and filtering functions.

[0010] A cell composed of hinged diagonal rods and springs not only exhibits large elastic deformation but also a strong stiffness softening effect. This effect stems from the cell's geometry and is primarily influenced by the longitudinal angle θ (the angle between the first, second, third, or fourth diagonal rod and the length direction of the metamaterial rod). A larger θ results in a weaker stiffness softening effect, thus it can be customized by altering the longitudinal angle θ. In addition, the stiffness and number of springs also affect the cell's stiffness. Therefore, the cell's stiffness can be customized by adjusting one or more of the spring stiffness, the number of springs, and the size of the longitudinal angle. To make the stiffness of the first cell less than that of the second cell, the spring stiffness of the first cell can be less than that of the second cell, the number of springs in the first cell can be less than that in the second cell, or the longitudinal angle of the first cell can be greater than that of the second cell.

[0011] The efficiency of momentum output after elastic wave conversion reflects the metamaterial rod's ability to reverse elastic waves. Studies show that the momentum conversion efficiency increases with increasing k2 / k1 and decreases with increasing θ2 / θ1, where k1 is the spring stiffness coefficient of the first cell, k2 is the spring stiffness coefficient of other cells, θ1 is the longitudinal angle of the first cell, and θ2 is the longitudinal angle of other cells. When k2 / k1 is between 3 and 4.5, and θ2 / θ1 is between 25° and 35°, the momentum conversion efficiency can reach above 0.5. Therefore, the spring stiffness coefficient k1 of the first cell and the spring stiffness coefficient k2 of the second cell preferably satisfy: 3 ≤ k2 / k1 ≤ 4.5, and the longitudinal angle θ1 of the first cell and the longitudinal angle θ2 of the second cell preferably satisfy: 25 / 35 ≤ θ2 / θ1 ≤ 35 / 35.

[0012] Metamaterial rods require a certain number of cells to propagate the wave in order to perform stress wave reversal or filtering. A lower critical cell number indicates a stronger reversal and filtering function. Theoretical results show that when a pulse of a certain amplitude is input, the critical cell number increases with the spring stiffness coefficient k1 of the first cell and decreases with the sliding friction coefficient μ. This is because a larger k1 means a smaller strain in the first cell, resulting in more energy transmitted to the second cell, thus increasing the number of cells required for the compression wave to attenuate to zero. When k1 approaches k2, the stress wave conversion and filtering function is lost. An increase in the sliding friction coefficient μ causes the compression wave to attenuate to zero more quickly. With appropriate values ​​for k1 and μ, only 7 cells are needed to achieve stress wave conversion and filtering. Therefore, the effective critical cell number of the metamaterial rod can be customized by designing the values ​​of k1 and μ.

[0013] The guide rod applies external friction (sliding friction) to the metamaterial rod, and its coefficient of sliding friction μ can be controlled by adjusting the surface roughness of the rod, thus ensuring the stability of the metamaterial rod for longitudinal wave propagation. Sliding bearings are installed between the guide rod and the through holes of the first and second connecting plates, which further improves the stability of the metamaterial rod for longitudinal wave propagation.

[0014] The second connecting plate of the first cell is detachably connected to the first connecting plate of the second cell, allowing replacement of the first cell to activate or deactivate the elastic wave's flipping and filtering function. Both the first and second connecting plates have mass blocks for adjusting their mass. These mass blocks can be nut-like. The ends of the first, second, third, and fourth inclined rods are pivotally connected via pivot shafts, with rolling bearings between the pivot shafts and the rods to reduce resistance during activation. The springs are tension and compression springs, with their ends pivotally connected to the first, second, third, and fourth inclined rods via connecting blocks. The mechanical signal receiver includes a sensor connected to the second connecting plate of the last cell.

[0015] Compared with existing technologies, this solution offers the following advantages: The metamaterial rod utilizes external friction and the non-uniform distribution of cells with a stiffness-softening effect to achieve the function of converting compression waves into tensile waves and filtering out tensile waves from waves subjected to mixed tensile and compression loading. These unique conversion and filtering functions are unidirectional (non-dissimilarity) and can be turned on or off by adjusting key cells. This provides a powerful designable platform for the manipulation of mechanical signals and opens up unprecedented opportunities for robotic actuators, impact resistance, novel material design, energy harvesting, and utilization. Attached Figure Description

[0016] 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.

[0017] Figure 1 This diagram illustrates the metamaterial rod, explaining its special properties and mechanisms. A shows the metamaterial rod's function in converting and filtering elastic wave signals, with red representing compression waves and blue representing tension waves. B is a schematic diagram of the propagation mechanism, where red lines represent compression waves, blue lines represent tension waves, and the arrows indicate the wave propagation direction. ρ a and ρ b Let c represent the initial density of the cell, respectively. a and c b A represents the wave speed propagating in a and b respectively; C is a schematic diagram of the metamaterial rod; D is the force-strain curve of the two cell elements (the first cell is labeled a, and the other cells are labeled b), the solid line represents the experimental results, the dashed line represents the theoretical results, and the shading represents the standard deviation of the three experiments; E is the stiffness-strain curve of the two cell elements.

[0018] Figure 2 This is a schematic diagram of a single cell assembly.

[0019] Figure 3 This is a schematic diagram of a static experiment on a single cell.

[0020] Figure 4 These are the equivalent stiffness curves of a unit cell under different parameters. Among them, A is the equivalent stiffness curve of a unit cell under four different spring stiffnesses; B is the equivalent stiffness curve of a unit cell under four different included angles.

[0021] Figure 5 This is a schematic diagram of the loading device. A represents the initial velocity plate impact loading; B represents the exciter loading.

[0022] Figure 6 This is a schematic diagram of a dynamic experiment. A shows the force-time curve measured using an oscilloscope and the motion-time curve of each cell element measured using a high-speed camera during the dynamic experiment; B shows the schematic diagram of the PVDF piezoelectric film being pasted.

[0023] Figure 7This is the dynamic response of the metamaterial rod. A represents experimental snapshots of the metamaterial rod at t = -0.03s, t = 0.1s, t = 0.2s, t = 0.25s, and t = 0.37s, where the red (blue) arrowed lines represent the axial compressive (tensile) displacement of the plate, and the length represents the magnitude of the displacement; B is the cell strain history corresponding to the experimental snapshots, where the strain at t = 0.1s, t = 0.2s, and t = 0.25s is shifted upwards by 0.6, 0.4, and 0.2, respectively; C is the force-time curve at the 3rd, 8th, 13th, and 17th plates; D represents the compression applied to the metamaterial rod. The cell strain contour plots obtained by applying pulses are shown below, where tensile strain is positive and compressive strain is negative. E shows the force-time curves at plates 1, 3, 8, and 17 obtained by applying compressive pulses, where the force-time curve at plate 1 is the input force-time curve and the force-time curve at plate 17 is the output force-time curve. F shows the cell strain contour plots obtained by applying mixed tensile and compressive pulses to the metamaterial rod. G shows the force-time curves at plates 1, 3, 8, and 17 obtained by applying mixed tensile and compressive pulses, where the output curve is shifted in the two-dimensional plot to compare the frequency changes of the input and output curves.

[0024] Figure 8 This section presents the switching cell function of the metamaterial rod and the proof of its non-dissimilarity. A shows the experimental results of the forward input, including the forward input compression pulse and mixed waveform. The red spring represents a small-stiffness spring, the gray spring represents a large-stiffness spring, and negative (positive) values ​​in the curves represent pressure (tension). B shows the experimental results of the forward input after changing the switching cell. C shows the experimental results of the reverse input.

[0025] Figure 9 These are the influencing factors of the conversion and screening function. Among them, A is a contour plot of the critical number of cells required for the metamaterial rod to complete the flipping function, and the contour lines at each major position have been marked on the figure; B is a contour plot of the critical number of cells required for the metamaterial rod to complete the screening function; C is a contour plot of the momentum conversion efficiency η.

[0026] Explanation of reference numerals in the attached drawings: guide rod 100, first connecting plate 211, second connecting plate 212, first inclined rod 221, second inclined rod 222, third inclined rod 223, fourth inclined rod 224, spring 230. Detailed Implementation

[0027] To enable those skilled in the art to better understand this solution, the following detailed description is provided in conjunction with specific embodiments.

[0028] This solution proposes a metamaterial rod that can completely reverse compressive stress waves into tensile waves, and can filter out tensile waves from waves subjected to mixed tensile and compressive loading, such as... Figure 1(A). The metamaterial rod has two types of cells. In this embodiment, each cell consists of four hinged diagonal rods, two tension / compression springs, and two connecting plates (the number of springs can also be configured as one or more, symmetrically or evenly arranged at any point on the pivot axis of the diagonal rod or on the diagonal rod parallel to the connecting plate). One type of cell has lower stiffness, and the other type has higher stiffness. The cell with lower stiffness is taken as the first cell, and all other cells starting from the second cell are periodically arranged in one dimension using cells with higher stiffness. Then, two stainless steel guide rods are symmetrically passed through the connecting plates at both ends of each cell to form the metamaterial rod, as shown below. Figure 1 (C) The two ends of the guide rod are fixed by supports.

[0029] I. Fabrication and Assembly of Metamaterial Rods

[0030] Using HY-303 adhesive, the spring and connecting block, the rolling bearing and the diagonal rod, and the sliding bearing and connecting plate are glued together. Then, M2 screws are used to connect the diagonal rod to the connecting plate and the connecting block of the spring, thus assembling a unit. Figure 2 As shown. The nut on the connecting plate acts as a mass block, which can be used to adjust the mass of the plate. The connecting plate and connecting block are 3D printed from 9400 resin material. The springs are custom-made from spring steel. The spring specifications for the two cell types are 0.6*10*18 (11 coils) and 0.5*7*18 (12 coils), with spring stiffnesses of 0.28 N / mm and 0.9 N / mm, respectively. The sliding bearing specification is LMUT13, and the rolling bearing specification is MF52ZZ. The mass of each part is shown in Table 1. Through extensive theoretical calculations, we determined the values ​​of each parameter in the experiment, where the length of the diagonal rod is 20 mm, and the angle θ with the longitudinal direction is 32°.

[0031] Table 1. Mass of each component in a unit cell

[0032]

[0033] Using a cell with lower stiffness as the first cell, and then arranging all other cells from the second cell onwards using cells with higher stiffness in a periodic one-dimensional arrangement, and then symmetrically passing two stainless steel guide rods through the connecting plates at both ends of each cell, a metamaterial rod is constructed, such as... Figure 1 (C) The two ends of the guide rod are fixed by supports.

[0034] II. Static Experimental Methods

[0035] To demonstrate the elastic deformation capacity and stiffness softening effect of the cell, a three-point bending testing machine with a range of 500N was used to measure the force-displacement curve and stiffness-strain curve of the cell. The upper and lower plates of the cell were fixed to the indenter of the testing machine and the clamps fixed to the worktable by pins, respectively. The upper plate moved up and down with the indenter, as... Figure 3As shown. Compression or tension loading was applied to the cell at a speed of 5 mm / min, and the force-displacement curves and stiffness-strain curves of the cell were obtained. Three experiments were performed for each cell type to verify repeatability. Figure 1 As shown in (D, E), the cell composed of the hinged link and the spring not only produces large elastic deformation but also exhibits a strong stiffness softening effect, with the stiffness dropping to zero when the strain reaches 0.3. This stiffness softening effect originates from the cell's geometric configuration and is mainly influenced by the longitudinal angle θ; the larger θ is, the weaker the cell stiffness softening effect (see...). Figure 4 Therefore, its stiffness softening effect can be customized by changing the longitudinal angle θ.

[0036] III. Dynamic Experiment

[0037] To demonstrate the flipping function of the metamaterial rod, we used a spring-launching device to impact the left end of the rod with a plate at a certain initial velocity. The right end of the rod was fixed to a support. The spring in the spring-launching device had a median diameter of 10cm, a length of 15cm, and a stiffness of 1N / mm. Both ends of the spring were glued to the 3D-printed plate, and one end was bolted to the support. Compression of the spring-launching device with the impact plate allowed the impact plate to be launched longitudinally at an initial velocity, which could be controlled by the spring compression strain. Magnets were attached to both the impact plate and the first plate of the metamaterial rod. After the impact plate collided with the first plate, the magnetic force caused them to move together as a single unit. Figure 5 As shown in (A).

[0038] Red dots were marked on the side of the plate with a marker pen. Then, a Nova S9 high-speed camera was used to capture the dynamic response of the metamaterial rod. Digital image correlation (DIC) technology was then used to analyze the motion of each cell in the metamaterial rod. A schematic diagram of the dynamic experimental measurement is shown below. Figure 6 (A). The rod deformation process captured by a high-speed camera and the resulting cell strain history, as shown in... Figure 7 As shown in (A, B).

[0039] Force-time curves at certain locations within the metamaterial rod were measured using polyvinylidene fluoride (PVDF) sensors. Specifically, plates 3, 8, and 13 were constructed by bonding two thin plates together to facilitate the attachment of PVDF sensors in the middle for measuring the corresponding force-time curves. Figure 6As shown. The sum of the masses of the two thin plates is equal to the masses of the plates at other locations. The PVDF sensor is a LDT1 028K, which is connected sequentially to a KD5008C charge amplifier and a TDS 2014C oscilloscope. The corresponding force-time curve can be derived from the voltage-time curve measured by the oscilloscope. Finally, the force-time curves of the 3rd, 8th, 13th, and 17th (last) plates are measured using the piezoelectric thin film embedded between the cells, as shown. Figure 7 As shown in (C).

[0040] from Figure 7 (A) It can be observed that at t = 0.1 seconds, the first cell initially exhibits significant compressive strain, but at t = 0.2 seconds, the first cell changes from a significant compressive state to a tensile state, while subsequent cells show only very small compressive strain. This indicates that the compressive wave has largely transformed into a tensile wave, which can also be seen from... Figure 7 In the force-time curve of the third plate in (C), it is observed that the pressure on the third plate is very small, while the tension is relatively large. It is important to note that as the wave propagates, under the influence of external friction, the compression wave decays rapidly, becoming very small at t = 0.25 seconds, and disappearing completely at t = 0.37 seconds. Only the tensile wave remains in the metamaterial rod. This can also be observed in... Figure 7 This is proven in (C). Figure 7 In (C), the 17th plate (output end) outputs pure tensile stress.

[0041] To more intuitively understand the metamaterial rod's ability to reverse elastic waves, we applied a compression pulse to the metamaterial rod using a JZQ-50 exciter. The exciter head was fixed to the 3D-printed rod, and an excitation force was applied to the metamaterial rod through the rod, as shown in 7(B). A dropable thin block was placed between the rod and the first plate. When the exciter output a sinusoidal excitation force, the metamaterial rod was only subjected to one cycle of compression pulse (when subjected to tensile force, the thin block falls, and the metamaterial rod is no longer affected by the exciter). The response of the metamaterial rod during the application of the compression pulse by the exciter is as follows: Figure 7 As shown in (D, E). From Figure 7 As can be seen in (D), the compression wave basically disappears after reaching the 15th cell, leaving only the tension wave, and only tensile stress is detected at the output end. Figure 7 (E)) achieves the reversal of the input compression wave to the output stretching wave.

[0042] To demonstrate the screening function of the metamaterial rod for mechanical signals, we glued the excitation head to the first plate, set the exciter to output a sinusoidal excitation force, and applied a 10-cycle tensile-compression hybrid sinusoidal stress wave to the first plate of the metamaterial rod using a JZQ-50 exciter. Figure 7As can be clearly observed in (F), after applying a mixed stress wave to the metamaterial rod, the compression wave disappears around the 15th cell, and only a periodic tensile wave is detected at the output end. Furthermore, the frequency of the output force basically corresponds to the frequency of the input force. Figure 7 (G)). This proves the screening function of the metamaterial rod. This function is achieved due to the stiffness softening effect of the metamaterial rod, which causes the amplitude of the compressive stress wave on the second cell to be significantly smaller than that of the tensile stress wave, such as... Figure 7 As shown in (G). Under the nonlinear dispersion of the compression wave by the cell and the action of external friction, the compression wave will disappear. In contrast, due to the isolated propagation characteristics of the metamaterial rod for the tensile wave (see the next paragraph), the tensile wave with a larger amplitude is retained (if the amplitude of the input mixed waveform is relatively large, the compression wave will be converted into a tensile wave, which will be superimposed with the input tensile wave to enhance the output tensile wave).

[0043] It is important to emphasize that the first weak cell is the switch that enables the elastic wave inversion and filtering functions. If the first cell is replaced with a cell identical to the others, the elastic wave inversion and filtering functions will not be possible. Figure 8 As shown in (B). As mentioned earlier, if the first and second cells are identical, the efficiency of converting the compression wave into the stretching wave is low. The converted stretching wave will be quickly dissipated by friction, leaving only the incompletely attenuated compression wave at the output. Similarly, when a mixed waveform is input, the compression wave transmitted to the second cell has greater energy and will be output at the output along with the stretching wave, as shown in (B). Figure 8 As shown in (B). It can be further concluded that the metamaterial rod exhibits non-dissimilarity in the propagation of compression waves and mixed waves; that is, when the wave is input in the opposite direction, the metamaterial rod does not possess the function of reversing and filtering elastic waves, as... Figure 8 As shown in (C).

[0044] Besides the switch cell, which is listed first, the friction between the guide rail and the rod also plays a crucial role in the transformation of the stress wave, preventing it from being simply converted into a leading rarefaction wave followed by an oscillating compression wave, as is often the case in many studies. Without external friction, according to the momentum theorem, internal forces would not change the system's momentum, and the total output momentum would eventually equal the input compression momentum after a long period of accumulation. The guide rail, through friction, plays a key role in the impulse of the metamaterial rod, transforming the output momentum into tensile momentum. Fortunately, in most cases, materials and structures require support rather than being suspended in mid-air, making friction between the material and the support unavoidable and providing the natural conditions for this peculiar phenomenon.

[0045] To gain a deeper understanding of the influencing factors of the flipping and filtering functions, we analyzed the theoretical results under different parameters. For a metamaterial rod to complete the stress wave flipping or filtering task, the wave propagation requires a certain number of cells; the lower this critical cell number, the stronger the flipping and filtering function. Theoretical results show that when a pulse of a certain amplitude is input, the critical cell number increases with the increase of the spring stiffness coefficient k1 of the first cell and decreases with the increase of the sliding friction coefficient μ, such as... Figure 9 As shown in (A, B). This is because a larger k1 means a smaller strain in the first cell, resulting in more energy transmitted to the second cell, thus increasing the number of cells required for the compression wave to attenuate to zero. As discussed earlier, when k1 approaches k2, the stress wave conversion and filtering function is lost. Furthermore, an increase in the sliding friction coefficient μ causes the compression wave to attenuate to zero more quickly. From Figure 9 As can be seen from the red dashed boxes in (A, B), with appropriate values ​​for k1 and μ, only 7 cells are needed to achieve stress wave conversion and filtering. Therefore, the effective critical cell number of metamaterial rods can be customized by designing the values ​​of k1 and μ.

[0046] It is worth noting that the metamaterial rod's ability to reverse stress waves is manifested not only in the critical cell number but also in the efficiency of momentum output after completing the elastic wave conversion. Here, the momentum conversion efficiency η is defined as -p out / p in , where p out p represents the momentum output at the critical cell. in This represents the momentum of the input system. (From...) Figure 9 (C) It can be observed that the value of η increases with increasing k2 / k1 and decreases with increasing θ2 / θ1. This is because both k2 / k1 and θ2 / θ1 change the stiffness of the first and second cells (see...). Figure 4 The greater the difference in stiffness between the two cells, the higher the conversion efficiency. When k2 / k1 is between 3 and 4.5, and θ2 / θ1 is between 25 / 35 and 35 / 35, the momentum conversion efficiency can reach above 0.5. Figure 9 As shown in the red dashed box in (C). Therefore, the momentum conversion efficiency of the metamaterial rod can also be controlled by changing the geometric parameters k1, k2, θ1, θ2 of the first two elements.

[0047] We demonstrate how a metamaterial rod with customizable stiffness softening effects can achieve unprecedented mechanical signal flipping and filtering capabilities. The non-dissimilarity and switchability of the metamaterial rod provide ample design space for the manipulation of mechanical signals. The metamaterial rod can completely convert impact compression pulses into tensile pulses, eliminating the impact at the rod's end. The mechanism of the flipping and filtering functions, as well as the design of the metamaterial structure, are of great significance in the field of reusable impact mitigation. Furthermore, the structure can move entirely in the loading direction under impact, enabling the design of impact-driven, reverse-motion soft robots. The filtering function of the metamaterial rod makes research into sound-driven robots, eliminating the need for motors, possible.

[0048] 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 mechanical signal control device, characterized in that, It includes a metamaterial rod with a mechanical signal input end and an output end, and a mechanical signal receiver connected to the mechanical signal output end; the metamaterial rod includes an even number of symmetrically arranged guide rods and multiple cells linearly arranged on the guide rods; along the mechanical signal input direction, the first cell can be adjusted or replaced with a first cell element or a second cell element, and the second to the last cells are all second cell elements; the stiffness of the first cell element is less than the stiffness of the second cell element; Both the first and second cells include a first connecting plate, a second connecting plate, a first diagonal rod, a second diagonal rod, a third diagonal rod, a fourth diagonal rod, and a spring. The first and second connecting plates are parallel to each other. The first ends of the first and second diagonal rods are pivotally connected to the side of the first connecting plate facing the second connecting plate. The first ends of the third and fourth diagonal rods are pivotally connected to the side of the second connecting plate facing the first connecting plate. The second ends of the first and third diagonal rods are pivotally connected to the first end of the spring. The second ends of the second and fourth diagonal rods are pivotally connected to the second end of the spring. In adjacent cells, the second connecting plate of the preceding cell and the first connecting plate of the following cell are shared or connected as a single unit. The first and second connecting plates are provided with an even number of through holes for the guide rod to pass through. The mechanical signal receiver is connected to the second connecting plate of the last cell. When the first cell is regulated or replaced by the first cell, the mechanical signal receiver receives the mechanical signal that has been flipped or filtered; when the first cell is regulated or replaced by the second cell, the mechanical signal receiver receives the mechanical signal that has been attenuated.

2. The mechanical signal control device according to claim 1, characterized in that, The spring stiffness of the first cell is less than that of the second cell; and / or the number of springs in the first cell is less than that in the second cell; and / or the longitudinal angle of the first cell is greater than that of the second cell, wherein the longitudinal angle is the angle between the first, second, third, or fourth diagonal rod and the length direction of the metamaterial rod.

3. The mechanical signal control device according to claim 1, characterized in that, The spring stiffness coefficient k1 of the first cell and the spring stiffness coefficient k2 of the second cell satisfy the following: 3≤k2 / k1≤4.5; and / or the longitudinal angle θ1 of the first cell and the longitudinal angle θ2 of the second cell satisfy the following: 25 / 35≤θ2 / θ1≤35 / 35.

4. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The second connecting plate of the first cell is detachably connected to the first connecting plate of the second cell.

5. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The mechanical signal receiver includes a sensor connected to a second connecting plate in the last cell.

6. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, A sliding bearing is provided between the guide rod and the through holes of the first connecting plate and the second connecting plate.

7. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The first and second connecting plates have mass blocks.

8. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The two ends of the first, second, third, and fourth diagonal bars are pivotally connected by a pivot shaft, and rolling bearings are provided between the pivot shaft and the first, second, third, and fourth diagonal bars.

9. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The spring is a tension / compression spring.

10. The mechanical signal control device according to any one of claims 1 to 3, characterized in that, The two ends of the spring are pivotally connected to the first, second, third, and fourth inclined rods via connecting blocks.

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