Self-adaptive variable stiffness vibration isolator

Abstract

The invention discloses a self-adaptive variable-stiffness vibration isolator which comprises a load platform, a vibration isolation element and a base, the vibration isolation element is arranged between the base and the load platform, the self-adaptive variable-stiffness vibration isolator further comprises a variable-stiffness control unit, the vibration isolation element is made of memory alloy with the shape changing along with the temperature, and the vibration isolation element is bent in shape at the normal temperature and becomes straight after being heated. The variable stiffness control unit is connected with the vibration isolation element and used for adjusting the temperature of the vibration isolation element. The strategy of changing the rigidity of the vibration isolation element is adopted to change the vibration isolation performance, different damping strategies are adopted for high-frequency vibration and low-frequency vibration, the vibration isolation element is heated to be straight for high-frequency vibration, the straight beam is high in bearing capacity and rigidity, and the corresponding high-frequency vibration reduction and isolation effect is good; and for low-frequency vibration, the vibration isolation element is cooled and bent, the curved beam is low in rigidity, and the low-frequency vibration reduction and isolation effect is good. The structure is simple, the number of assemblies is small, the design effect is remarkable, and the practical engineering application value is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of vibration reduction and noise reduction, and particularly relates to an adaptive variable stiffness vibration isolator. Background Art

[0002] Vibration reduction has always been a critical issue in engineering. As aerospace equipment evolves toward lightweight, integrated, and intelligent design, many engineering structures and precision equipment require isolation from unwanted vibrations to prevent external vibrations from interfering with precision components and causing fatigue damage. Traditional vibration isolators, primarily rubber and metal spring types, achieve this by isolating the vibration source from the object being protected. While offering advantages such as good load-bearing capacity and robust stability, these isolators often suffer from short lifespans and poor environmental adaptability. Furthermore, traditional vibration and noise reduction technologies are not only ineffective at low-frequency vibration isolation but also result in heavy equipment, contradicting the concept of lightweight design. Furthermore, in complex and changing environments, external excitations are increasingly variable, and existing methods for controlling vibration and noise are no longer able to meet the design requirements for vibration reduction under these varying excitations. Therefore, the design of adaptive variable-stiffness isolators, which can achieve the required vibration isolation under varying external excitations by varying stiffness, plays a significant role in ensuring the safe operation of the system.

[0003] 4D printing adds a time dimension to 3D printing. This means that 4D printing involves creating products whose shape, function, and dimensions change over time under specific conditions and under stimuli such as light, magnetism, water, heat, and electricity. Using 4D printing to integrally mold materials with shape memory and modify their configuration through thermal stimulation is an effective approach for designing and manufacturing variable-stiffness superstructures.

[0004] The invention patent application with the patent application number "202310321574.8" and the name "An Electromagnetic Variable Stiffness and Variable Damping Vibration Isolator" discloses a variable stiffness and variable damping vibration isolator that uses the Ampere force to achieve variable system stiffness and damping with a large dynamic adjustable range. The vibration signal is measured by a vibration sensor, and the current control board adjusts the magnitude and direction of the coil energization, thereby generating the required damping force or equivalent negative stiffness, thereby achieving adaptive adjustment of the stiffness and damping of the vibration isolator. Although this patent has variable stiffness adaptive performance and can isolate vibrations from different external excitations, its structure is very complex and requires a large number of external facilities to be added to the vibration isolator. It is difficult to implement in some situations where the requirements for the size and weight of the vibration isolator are strict and the working environment is harsh. It is also different from the principle of the variable stiffness vibration isolator based on the shape memory superstructure of this patent. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an adaptive variable stiffness vibration isolator in response to the deficiencies of the above-mentioned prior art. The vibration isolator of the present invention utilizes the principle of switching between straight beams and curved beams to achieve adjustable stiffness and vibration reduction and isolation performance of the vibration isolator. Straight beams and curved beams have significant differences in stiffness. Straight beams have strong bearing capacity and high stiffness, and have good high-frequency vibration reduction and isolation effects. Curved beams have low stiffness and can exhibit quasi-zero stiffness characteristics after design, and have good low-frequency vibration reduction and isolation effects. A straight beam-curved beam core is provided inside the vibration isolator, and a material with a shape memory effect is selected to construct the straight beam-curved beam core. Under the condition of controlling external excitation, the shape of the core can be controlled to change, thereby achieving variable stiffness controllability and vibration reduction effect frequency range controllability to meet vibration reduction requirements at different frequencies. In addition, the shape memory alloy material itself will also exhibit different material properties under temperature control, so the stiffness and vibration reduction and isolation performance of the structure can be further adjusted. The present invention can be used to protect precision instrument components such as optoelectronic equipment from interference with the equipment caused by vibrations from transportation vehicles, transmission machinery, etc., which affects the accuracy of the equipment. In particular, considering that the external vibration load will change in different service conditions, the corresponding vibration source frequency and amplitude will change. A vibration isolator with a variable stiffness superstructure design with a shape memory function is used. The shape of the temperature-controlled superstructure is regulated by temperature changes, so that the structural stiffness changes significantly, thereby achieving the purpose of resisting external vibrations of different frequencies.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] An adaptive variable stiffness vibration isolator includes a load platform, a vibration isolation element and a base. The vibration isolation element is arranged between the base and the load platform. The adaptive variable stiffness vibration isolator also includes a variable stiffness control unit. The vibration isolation element is made of a memory alloy whose shape changes with temperature. The vibration isolation element is bent at room temperature and straightens after heating. The variable stiffness control unit is connected to the vibration isolation element and is used to adjust the temperature of the vibration isolation element.

[0008] To optimize the above technical solutions, specific measures taken also include:

[0009] The above-mentioned vibration isolation element is a nickel-titanium shape memory alloy made by 4D printing.

[0010] The above-mentioned variable stiffness control unit consists of a vibration sensor, a heating film, and a main control board. The vibration sensor is fixed to the load platform, and the heating film is attached to the surface of the vibration isolation element. The heating film and the vibration sensor are both connected to the main control board. The vibration sensor is used to detect the frequency information of the external excitation applied to the load platform and send the frequency information to the main control board. The main control board applies temperature excitation to the vibration isolation element through the heating film based on the frequency information, causing the vibration isolation element to deform and produce a stiffness change that is adapted to the frequency of the external excitation applied to the load platform.

[0011] The above-mentioned heating film is a PI heating film.

[0012] The upper end of the vibration isolation element is fixedly connected to the lower surface of the load platform, and the lower end of the vibration isolation element is fixedly connected to the upper surface of the base. The load platform and the base are both made of hard materials.

[0013] The above-mentioned main control board includes a spectrum analyzer, a switch controller and a current adjustable circuit. The vibration sensor is connected to the spectrum analyzer signal, the spectrum analyzer is connected to the switch controller, and the switch controller is connected to the current adjustable circuit. The current adjustable circuit is used to energize and heat the heating film. The spectrum analyzer is used to detect the frequency information transmitted by the vibration sensor, convert the electrical signal into a frequency domain signal, and divide it into different frequency bands according to the frequency. The frequency band data is then transmitted to the switch controller. The switch controller controls the on and off of the current adjustable circuit and the current in the circuit according to the frequency band data.

[0014] The load platform and the base are both provided with screw holes, which are used to cooperate with bolts to fix the vibration isolator to the equipment and the vibration source.

[0015] There are one or more vibration isolation elements between the load platform and the base.

[0016] The initial shape of the above-mentioned vibration isolation element is C-shaped or S-shaped. When heated to 90°C, it becomes straight and linear. When cooled to 25°C and compressed by external force, it returns to its original shape.

[0017] The number of the screw holes is multiple.

[0018] The present invention has the following advantages:

[0019] (1) In addition to having good vibration isolation performance, the present invention has a strong load-bearing capacity before and after the stiffness changes. Therefore, unlike a spring isolator, the present invention can also be used as a load-bearing structure.

[0020] (2) The present invention uses a strategy of changing the stiffness of the isolation element to alter the vibration isolation performance, employing different damping strategies for high- and low-frequency vibrations. Specifically, for high-frequency vibrations, the isolation element is heated and straightened. Straight beams have strong load-bearing capacity and high stiffness, resulting in better high-frequency vibration isolation. For low-frequency vibrations, the isolation element is cooled and bent. Curved beams have low stiffness, resulting in better low-frequency vibration isolation. Furthermore, the present invention reduces stiffness while minimizing the decrease in load-bearing capacity. Through structural design, the stiffness change is approximately 8 times, while the maximum load is reduced by only 20%.

[0021] (3) The present invention has a simple structure, a small number of components, and a significant design effect, and has certain practical engineering application value.

[0022] (4) The design method of the present invention is supported by response simulation results, has strong scalability, and has a broad design space. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the overall structure of the vibration isolation element of the present invention before deformation;

[0024] Figure 2 This is a schematic diagram of the structure of the vibration isolation element after deformation of the present invention;

[0025] Figure 3 The specific shape diagrams of the vibration isolation element of the present invention at 90°C and 25°C respectively;

[0026] Figure 4 Relationship curves between loss factor, loss modulus and storage modulus of the shape memory alloy of the vibration isolation element of the present invention at different temperatures;

[0027] Figure 5 This is a simulation diagram of the load-displacement curve of the vibration isolator of the present invention;

[0028] Figure 6 This is a simulation diagram of the vibration transmissibility curve of the present invention; the vertical axis dB in the figure is the acceleration transmissibility, and the formula is express.

[0029] The reference numerals in the figure are: 1 is a load platform, 2 is a vibration isolation element, 3 is a base, 4 is a screw hole, 5 is a vibration sensor, 6 is a heating film, and 7 is a main control board. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0031] Obviously, the drawings described below are merely examples or embodiments of the present application. Those skilled in the art can, without inventive effort, apply the present application to other similar scenarios based on these drawings. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, changes in design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in this application.

[0032] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0033] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "a", "an", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or units (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The words "multiple" / "several" used in this application refer to two or more. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, or B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0034] like Figure 1 As shown, an adaptive variable stiffness vibration isolator includes a load platform 1, a vibration isolation element 2, a base 3 and a variable stiffness control unit. The variable stiffness control unit mainly includes a vibration sensor 5 fixed on the load platform, a heating film 6 fixed on the shape memory alloy of the vibration isolation element 2, and a main control board 7. Among them, the main control board 7 is composed of a spectrum analyzer, a switch controller and a current adjustable circuit. In this example, there are four M16 screw holes on the load platform and the support respectively, which are used to fix the vibration isolator to the equipment and the vibration source. The number of screw holes and the position of the holes can be changed according to the working conditions. The load platform and the base both use a fillet with a radius of 10mm, and its size can also be selected according to the actual application scenario.

[0035] The vibration isolation element 2 is fixed between the load platform 1 and the base 3. Both the load platform 1 and the base 3 are made of rigid materials, usually the more common 45 steel, or directly selected according to the required application scenario, and it is only necessary to ensure that it does not undergo large deformation. The vibration isolation element 2 is made of nickel-titanium shape memory alloy by 4D printing technology. Its shape can change with temperature. It is set to two periodic units. The arrangement and number of periodic units can be selected according to the required application scenario. The example of the present invention only describes one of the examples, not all examples. Similarly, this application also only describes S-type or C-type deformation mode examples. Different length and width combinations can be designed according to different deformation needs. Based on the embodiments of the invention, without departing from the spirit and essence of the invention, any technician familiar with this technical field can make various corresponding changes and deformations according to the present invention. Any technical solution formed by equivalent replacement or equivalent transformation should fall within the scope of protection of the claims attached to the present invention.

[0036] The nickel-titanium shape memory alloy vibration isolation element is as follows: Figure 3 As shown, the shape memory alloy is two-way, with an initial shape of C or S. When heated to 90°C, it changes from curved to straight and becomes a straight line; when cooled to room temperature 25°C, it recovers its initial configuration after being compressed by external force.

[0037] The relationship curves of the loss factor, storage modulus and loss modulus of the nickel-titanium shape memory alloy vibration isolation element and temperature are as follows: Figure 4 As shown in the figure, the storage modulus curve shows that the nickel-titanium shape memory alloy has good elastic properties, is suitable for scenes requiring frequent loading and unloading, and is suitable for the design of vibration isolators; the loss factor curve shows that the nickel-titanium shape memory alloy has good damping performance and is suitable for the design of vibration isolators; Figure 4 The curve shows that the nickel-titanium shape memory alloy has good durability during cyclic loading and unloading, can be repeatedly heated and cooled and deformed, and is suitable for the design of variable stiffness vibration isolators.

[0038] The vibration sensor 5 in the variable stiffness control unit is fixed on the load platform 1 and is used to sense external vibration signals. The vibration sensor 5 is connected to the main control board 7. The specific control measures are as follows: the vibration sensor transmits the external vibration signal detected on the load platform to the spectrum analyzer of the main control board 7. The spectrum analyzer is used to detect the frequency information transmitted by the vibration sensor, convert the electrical signal into a frequency domain signal, and divide it into different frequency bands according to the frequency. The frequency band data is then transmitted to the switch controller. The switch controller controls the on and off of the current adjustable circuit and the current in the circuit according to the frequency band data, and then controls the temperature to cause the vibration isolation element 2 to deform.

[0039] Further explanation of control measures, such as Figure 6As shown in the figure, when the external excitation is 700-1000Hz, the straight rod vibration reduction effect is obvious. When the vibration sensor detects that the external excitation is in this frequency range, the switch controller closes the current adjustable circuit switch, adjusts the sliding rheostat to the minimum resistance, turns on the PI heating film, heats it to 90℃, and the structure changes to a straight rod shape, which can effectively reduce the amplitude of this frequency range; when the external excitation is 300-500Hz, the curved rod vibration reduction effect is obvious. When the vibration sensor detects that the external excitation is in this frequency range, the switch controller turns on the current adjustable circuit switch and turns off the PI heating film. The membrane is cooled to room temperature of 25°C, and the structure becomes a curved rod shape, which can effectively reduce the amplitude of this frequency band; when the external excitation is 500-700Hz, the vibration isolation element has a better vibration reduction effect in the intermediate state between the curved rod and the straight rod. When the vibration sensor detects that the external excitation is in this frequency band, the switch controller closes the current-adjustable circuit switch, adjusts the sliding rheostat, and the current of the current-adjustable circuit, turns on the PI heating film, and adjusts the current to adjust the heating film power and thus control the temperature at 25°C-90°C. The structure becomes an intermediate state, which can effectively reduce the amplitude of this frequency band.

[0040] The following parameters are used in this case to further illustrate the vibration isolator: The vibration isolation element is 54mm high, 120mm long, 110mm wide, and 3mm thick. It consists of two periodic units. To improve the reliability of the structure, a 3×3mm square reinforcement is used at the stress concentration point at the bottom of the support rods on both sides; the base is 190mm long, 110mm wide, and 8mm thick; the load platform is 176mm long, 110mm wide, and 8mm thick. The elastic characteristics of the vibration isolation element are described by Young's modulus E = 1.4GPa and Poisson's ratio v = 0.4. The structure is simulated and calculated using COMSOL. Figure 5 The displacement-load diagram shown and Figure 6 The acceleration transmissibility curves shown match the out-of-plane compression scenario and the load plane vibration excitation scenario, respectively.

[0041] like Figure 5 As shown in the figure, the stiffness of the vibration isolation element changes by 7.85 times before and after deformation, and the stiffness changes significantly. The maximum load only decreases by 20.42%, and the static performance is excellent. Figure 6 As shown, the effective frequency range for vibration isolation before structural deformation is 620-1000Hz, and after structural deformation, the effective frequency range is 350-700Hz. Vibration sensor 5 senses the external vibration signal and transmits it to the main control board. The main control board analyzes the vibration signal from the vibration sensor and determines the excitation frequency f of the load platform. Based on the excitation frequency f, the main control board determines the variable stiffness strategy. If f>700Hz, structural deformation is not required and the original temperature is maintained. If f<700Hz, the signal is transmitted to the heating film, heating the vibration isolation element, causing the isolation element structure to deform and isolate the excitation vibration.

[0042] Depend on Figure 5 The load-displacement curves of isolation element 2 at different temperatures further illustrate the design of the isolator. These load-displacement curves, derived from quasi-static compression tests using a universal compressor, show that when the structure is at 90°C, it is a straight rod. Before deformation, it exhibits high stiffness and a strong load-bearing capacity, capable of carrying heavy equipment. However, due to its high stiffness, it only provides vibration isolation at higher frequencies, with poor isolation at lower frequencies. Therefore, the component is bent to adjust its stiffness. When the structure is at 25°C, it becomes a curved rod. After deformation, its stiffness decreases significantly, and it exhibits a quasi-zero stiffness characteristic, resulting in significant vibration reduction in the relatively low-frequency range. Therefore, given that isolator performance can be improved by lowering its natural frequency, this structure, while sacrificing a certain degree of load-bearing capacity, reduces its overall stiffness and lowers its natural frequency by modifying the curved beam shape, resulting in improved isolator performance and more pronounced vibration reduction at lower frequencies. At the same time, materials with shape memory effect are selected to build curved beams. Under the condition of controlling external excitation, the structural shape can be controlled to change, thereby achieving controllable variable stiffness and controllable frequency range of vibration reduction effect to adapt to vibration reduction needs at different frequencies.

[0043] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An adaptive variable stiffness vibration isolator, comprising a load platform (1), a vibration isolation element (2) and a base (3), wherein the vibration isolation element (2) is arranged between the base and the load platform, and is characterized in that: The adaptive variable stiffness vibration isolator also includes a variable stiffness control unit. The vibration isolation element (2) is made of a memory alloy whose shape changes with temperature. The vibration isolation element (2) is bent at room temperature and becomes straight after heating. The variable stiffness control unit is connected to the vibration isolation element (2) and is used to adjust the temperature of the vibration isolation element (2).

2. The adaptive variable stiffness vibration isolator according to claim 1, characterized in that: The vibration isolation element (2) is a nickel-titanium memory alloy made by 4D printing.

3. The adaptive variable stiffness vibration isolator according to claim 2, characterized in that: The variable stiffness control unit is composed of a vibration sensor (5), a heating film (6), and a main control board (7). The vibration sensor (5) is fixed to the load platform (1), and the heating film (6) is attached to the surface of the vibration isolation element (2). The heating film (6) and the vibration sensor (5) are both connected to the main control board (7). The vibration sensor (5) is used to detect the frequency information of the external excitation applied to the load platform (1) and send the frequency information to the main control board (7). The main control board (7) applies temperature excitation to the vibration isolation element (2) through the heating film (6) based on the frequency information, so that the vibration isolation element (2) is deformed, thereby generating a stiffness change adapted to the frequency of the external excitation applied to the load platform (1).

4. The adaptive variable stiffness vibration isolator according to claim 1, characterized in that: The heating film (6) is a PI heating film.

5. The adaptive variable stiffness vibration isolator according to claim 1, characterized in that: The upper end of the vibration isolation element (2) is fixedly connected to the lower surface of the load platform (1), and the lower end of the vibration isolation element (2) is fixedly connected to the upper surface of the base (3). The load platform (1) and the base (3) are both made of hard materials.

6. The adaptive variable stiffness vibration isolator according to claim 3, characterized in that: The main control board (7) includes a spectrum analyzer, a switch controller and a current adjustable circuit. The vibration sensor (5) is connected to the spectrum analyzer signal, the spectrum analyzer is connected to the switch controller, and the switch controller is connected to the current adjustable circuit. The current adjustable circuit is used to energize and heat the heating film (6). The spectrum analyzer is used to detect the frequency information transmitted by the vibration sensor (5), convert the electrical signal into a frequency domain signal, and divide it into different frequency bands according to the frequency. The frequency band data is then transmitted to the switch controller. The switch controller controls the on and off of the current adjustable circuit and the current size in the circuit according to the frequency band data.

7. The adaptive variable stiffness vibration isolator according to claim 1, characterized in that: Screw holes (4) are provided on the load platform (1) and the base (3), and the screw holes (4) are used to cooperate with bolts to fix the vibration isolator on the equipment and the vibration source.

8. The adaptive variable stiffness vibration isolator according to claim 1, characterized in that: The number of the vibration isolation elements (2) between the load platform (1) and the base (3) is one or more.

9. The adaptive variable stiffness vibration isolator according to claim 2, characterized in that: The initial shape of the vibration isolation element (2) is C-shaped or S-shaped. When heated to 90°C, it changes from a bend to a straight line. When cooled to 25°C and compressed by an external force, it recovers its initial shape.

10. The adaptive variable stiffness vibration isolator according to claim 7, characterized in that: The number of the screw holes (4) is multiple.

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