An electromagnetic quasi-zero stiffness vibration isolation device with adjustable stiffness

Abstract

This invention provides an electromagnetic quasi-zero stiffness vibration isolation device with adjustable stiffness. It utilizes an electromagnetic coil to provide variable nonlinear negative stiffness, achieving quasi-zero stiffness characteristics. The invention includes a lower housing of a support, a lower end cover, a lower coil, a lower annular permanent magnet, a top block, an upper coil, an upper housing of the support, an upper end cover, a guide rod, an upper outer spring, an upper housing of the permanent magnet, an upper inner spring, an upper permanent magnet, an intermediate permanent magnet, a lower housing of the permanent magnet, a lower inner spring, and a lower outer spring. The permanent magnet and the electromagnetic coil provide variable nonlinear negative stiffness, achieving variable quasi-zero stiffness characteristics. This invention is particularly suitable for applications requiring isolation of wide-frequency excitations, including low-frequency ones.

Description

Technical Field

[0001] This invention relates to the field of vibration isolation technology, and in particular to an electromagnetic quasi-zero stiffness vibration isolation device with adjustable stiffness. Background Technology

[0002] According to vibration theory, only when the excitation frequency is greater than... Vibration isolation devices can only reduce vibration when the system's natural frequency is twice that of the vibration isolation device. To isolate low-frequency external excitation, the stiffness of the isolation device is usually reduced to achieve vibration reduction, but this also leads to increased static deformation and decreased system stability. This paper proposes a vibration isolation device that simultaneously possesses high static stiffness to overcome system stability issues and low dynamic stiffness to improve the ability to isolate low-frequency external excitation.

[0003] By utilizing vibration isolation devices with quasi-zero stiffness, a vibration isolation system can achieve nonlinear stiffness characteristics of "high static and low dynamic". Quasi-zero stiffness refers to the fact that the stiffness of the vibration isolation device is close to 0 near the static equilibrium position, thereby increasing the vibration isolation effect when the system is subjected to external excitation at the equilibrium position.

[0004] Quasi-zero stiffness vibration isolation devices can achieve nonlinear quasi-zero stiffness based on geometric nonlinearity, nonlinear quasi-zero stiffness based on quasi-zero stiffness metamaterials, or nonlinear quasi-zero stiffness based on electromagnetic force. Geometric nonlinear vibration isolation devices only use springs and rigid components (cams, connecting rods, etc.), utilizing the motion of the components to generate nonlinear stiffness and achieve quasi-zero stiffness. However, under large external forces or long-term loads, they will produce large residual deformations, affecting their performance and lifespan.

[0005] Vibration isolation devices based on quasi-zero stiffness metamaterials achieve quasi-zero stiffness by periodically inserting structures with special functions into a continuum. However, research on quasi-zero stiffness metamaterials is still in the research and development stage, and issues such as the long-term stability, reliability, and large-scale production process of their vibration isolation devices need to be addressed.

[0006] Electromagnetic vibration isolation devices provide negative stiffness through the interaction force between magnets, achieving near-zero stiffness when combined with a rationally designed positive stiffness structure. Electromagnetic vibration isolation devices offer advantages such as withstanding large loads, fast response speed, and good isolation effect. The magnetic force generated by the electromagnetic coil is adjusted by current, facilitating intelligent control. However, the magnetic force is greatly affected by the positional relationship between the permanent magnets (electromagnetic coils), requiring sophisticated installation and a suitable magnetic field environment. Therefore, electromagnetic vibration isolation devices are well-suited for applications involving large loads, periodic excitation, and small displacements, such as the foundations of power equipment and automotive suspension shock absorbers. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide an electromagnetic quasi-zero stiffness vibration isolation device with adjustable stiffness, which can quickly isolate impact excitation, reduce the dynamic response of the isolated equipment, and at the same time, the device can isolate the harmonic excitation generated by the isolated equipment for a long time and isolate its external radiated vibration response.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: an electromagnetic quasi-zero stiffness vibration isolation device with adjustable stiffness, comprising a lower outer shell of a support (1), a lower end cover (2), a lower coil (3), a lower permanent magnet (4), a top block (5), an upper coil (6), an upper outer shell of a support (7), an upper end cover (8), a shaft (9), an upper outer spring (10), an upper shell of a permanent magnet (11), an upper inner spring (12), an upper permanent magnet (13), a middle permanent magnet (14), a lower shell of a permanent magnet (15), a lower inner spring (16), and a lower outer spring (17); the lower outer shell of the support (1), the upper outer shell of the support (7), the upper end cover (8), and the lower end... The cover (2), upper coil (6), and lower coil (3) form the basic components of the vibration isolation device. The upper outer shell (1) of the support is connected to the lower outer shell (7). The upper end cover (8) and lower end cover (2) are connected to the corresponding upper and lower outer shells, respectively. The upper coil (6) and lower coil (3) are rigidly connected coaxially to the upper outer shell (7) and lower outer shell (1) of the support using metal glue. The basic components are rigidly connected to the mounting foundation through the holes on the flange of the lower outer shell (1) of the support by bolts. The shaft (9), intermediate permanent magnet (14), and top block (5) form a linear motion structure component. The axial positioning of the intermediate permanent magnet (14) is achieved by machining on the shaft. The step is achieved, and circumferential positioning is achieved by the inner cavity of the permanent magnet and the shaft (9). One end of the shaft (9) is connected to the external load through a thread. The upper permanent magnet (13), the lower permanent magnet (4), the upper shell (11) of the permanent magnet and the lower shell (15) of the permanent magnet form a negative stiffness component. The upper shell (11) and the lower shell (15) of the permanent magnet are connected by threads. The upper permanent magnet (13) and the lower permanent magnet (4) are rigidly connected coaxially to the upper shell (11) and the lower shell (15) of the permanent magnet using metal glue. One end of the upper inner spring (12) is pressed against the step of the shaft (9), and the other end is pressed against the upper end cover (8). On the upper part, the lower inner spring (16) rests on the top block (5) at one end and on the lower end cover (2) at the other end. Based on this, the linear motion component and the base component are elastically connected through the upper inner spring (12) and the lower inner spring (16). One end of the upper outer spring (10) rests in the groove of the upper housing (11) of the permanent magnet and the other end rests on the upper outer shell (7) of the support. One end of the lower outer spring (17) rests in the groove of the lower housing (15) of the permanent magnet and the other end rests on the lower outer shell (1) of the support. The groove is used for the axial positioning of the two outer springs. Based on this, the negative stiffness component and the base component are elastically connected through the upper outer spring (10) and the lower outer spring (16).

[0009] In a preferred embodiment, the basic components, linear motion structure components, and negative stiffness components, except for the permanent magnets and electromagnetic coils therein, are all made of low magnetic permeability materials with a relative permeability higher than 2.

[0010] In a preferred embodiment, the intermediate permanent magnet (14) is spaced 6 mm apart from the upper permanent magnet (13) and the lower permanent magnet (4). The working stroke of the upper inner spring (12) and the lower inner spring (16) after pre-tensioning should be greater than 6 mm. The working stroke of the outer spring is set to 5 mm, that is, the working stroke of the upper outer spring (10) and the lower outer spring (17) after pre-tensioning is 5 mm. The upper inner spring (12), the lower inner spring (16), the upper outer spring (10) and the lower outer spring (17) are all selected as helical compression springs. Based on this, the movement stroke of the permanent magnet is 22 mm and the quasi-zero stiffness working stroke is 12 mm.

[0011] In a preferred embodiment, the upper housing (1) of the support and the lower housing (7) of the support are connected by threads.

[0012] In a preferred embodiment, the upper end cover (8) and the lower end cover (2) are respectively connected to the corresponding upper and lower outer shells by threads.

[0013] Compared with existing technologies, the present invention has the following advantages: The present invention utilizes a coaxially opposed arrangement of an electromagnetic coil and a permanent magnet to provide variable nonlinear negative stiffness, and a coaxially opposed arrangement of a helical spring to provide linear positive stiffness, enabling the vibration isolation device to be in a quasi-zero stiffness state at static equilibrium. When the excitation changes, the quasi-zero stiffness state of the vibration isolation device can be maintained by changing the current in the electromagnetic coil, thus ensuring that the device always has excellent low-frequency vibration isolation performance. Even when the electromagnetic coil fails, the permanent magnet still provides negative stiffness, and the device still has low-frequency vibration isolation capability. The electromagnetic quasi-zero stiffness vibration isolation device of the present invention has a wide range of applications, broad frequency vibration isolation capability, especially excellent low-frequency vibration isolation capability, is easy to control, has a compact structure, and is simple to operate. Attached Figure Description

[0014] Figure 1 This is an isometric sectional view of a preferred embodiment of the present invention.

[0015] Figure 2 These are three views of a preferred embodiment of the present invention, including a front view, a top view, and a left view.

[0016] Figure 3 This is a schematic diagram of the installation method of a preferred embodiment of the present invention.

[0017] Figure 4 This is a diagram showing the relative positions of the upper permanent magnet, lower permanent magnet, upper coil, and lower coil in a preferred embodiment of the present invention.

[0018] Figure 5 This is the stiffness curve of the vibration isolation device when no current is passed through the coil in a preferred embodiment of the present invention.

[0019] Figure 6 These are electromagnetic force-displacement curves under different currents in a preferred embodiment of the present invention.

[0020] exist Figure 1-4 In the middle, 1. Lower outer shell of the support, 2. Lower end cover, 3. Lower coil, 4. Lower permanent magnet, 5. Top block, 6. Upper coil, 7. Upper outer shell of the support, 8. Upper end cover, 9. Guide rod, 10. Upper outer spring, 11. Upper shell of the permanent magnet, 12. Upper inner spring, 13. Upper permanent magnet, 14. Middle permanent magnet, 15. Lower shell of the permanent magnet, 16. Lower inner spring, 17. Lower outer spring. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] refer to Figure 1-6 An electromagnetic quasi-zero stiffness vibration isolation device consists of a lower outer shell 1, a lower end cover 2, a lower coil 3, a lower permanent magnet 4, a top block 5, an upper coil 6, an upper outer shell 7, an upper end cover 8, a shaft 9, an upper outer spring 10, an upper shell 11 of the permanent magnet, an upper inner spring 12, an upper permanent magnet 13, a middle permanent magnet 14, a lower shell 15 of the permanent magnet, a lower inner spring 16, and a lower outer spring 17.

[0025] The lower housing 1, upper housing 7, upper end cover 8, lower end cover 2, upper coil 6, and lower coil 3 constitute the basic components of the vibration isolation device. The upper housing 1 and lower housing 7 are connected by threads. The upper end cover 8 and lower end cover 2 are respectively connected to the corresponding upper and lower housings by threads. The upper coil 6 and lower coil 3 are rigidly connected coaxially inside the upper housing 7 and lower housing 1 using metal glue. The basic components are rigidly connected to the mounting foundation through the holes on the flange of the lower housing 1 by bolts.

[0026] Shaft 9, intermediate permanent magnet 14 and top block 5 form a linear motion structure assembly. The axial positioning of intermediate permanent magnet 14 is achieved by machining steps on the shaft, and the circumferential positioning is achieved by the inner cavity of the permanent magnet cooperating with shaft 9. One end of shaft 9 is connected to an external load through a thread.

[0027] The upper permanent magnet 13, the lower permanent magnet 4, the upper permanent magnet shell 11, and the lower permanent magnet shell 15 constitute a negative stiffness assembly. The upper permanent magnet shell 11 and the lower permanent magnet shell 15 are connected by threaded connections. The upper permanent magnet 13 and the lower permanent magnet 4 are rigidly connected coaxially to the upper permanent magnet shell 11 and the lower permanent magnet shell 15 respectively using metal glue.

[0028] One end of the upper inner spring 12 rests on the step of the shaft 9, and the other end rests on the upper end cover 8. One end of the lower inner spring 16 rests on the top block 5, and the other end rests on the lower end cover 2. Based on this, the linear motion component and the base component are elastically connected through the upper inner spring 12 and the lower inner spring 16.

[0029] One end of the upper outer spring 10 rests in the groove of the upper housing 11 of the permanent magnet, and the other end rests on the upper housing 7 of the support. One end of the lower outer spring 17 rests in the groove of the lower housing 15 of the permanent magnet, and the other end rests on the lower housing 1 of the support. The groove is used for axial positioning of the two outer springs. Based on this, the negative stiffness component and the base component are elastically connected through the upper outer spring 10 and the lower outer spring 16.

[0030] Except for the permanent magnet and the electromagnetic coil, the basic components, linear motion structure components and negative stiffness components are all made of low magnetic permeability materials with a relative permeability higher than 2, such as high carbon steel, aluminum alloy, thermosetting plastics, etc. The electromagnetic coil is made of enameled wire.

[0031] The intermediate permanent magnet 14 is spaced 6mm apart from the upper permanent magnet 13 and the lower permanent magnet 4. The working stroke of the upper inner spring 12 and the lower inner spring 16 after pretensioning should be greater than 6mm. In order to increase the working stroke of the vibration isolation device, the working stroke of the outer spring is set to 5mm, that is, the working stroke of the upper outer spring 10 and the lower outer spring 17 after pretensioning is 5mm. The upper inner spring 12, the lower inner spring 16, the upper outer spring 10 and the lower outer spring 17 are all selected as helical compression springs. Based on this, the movement stroke of the permanent magnet is 22mm and the quasi-zero stiffness working stroke is 12mm.

[0032] like Figure 1As shown, the linear motion structure component is connected in parallel with the base component by an inner spring, and the negative stiffness component is connected in parallel with the base component by an outer spring. When the vibration isolation device is subjected to external excitation, the linear motion structure component will generate relative displacement with the base component. At this time, one inner spring will be compressed, and the other inner spring will be extended. The middle permanent magnet 14 is close to the permanent magnet on one side. At this time, the magnetic force generated between the permanent magnets is not balanced, and the magnetic force will cancel the elastic force of the inner spring. The vibration isolation device exhibits quasi-zero stiffness characteristics. When the linear motion structure component moves to the set limit position, the linear motion structure component will eventually continue to move in the previous direction together with the negative stiffness component. The linear motion structure component and the negative stiffness component generate relative displacement with the base component. Like the inner spring, one side of the outer spring is compressed and the other side of the outer spring is extended. At this time, the inner and outer springs are connected in parallel. The displacement of the vibration isolation device has exceeded the range of quasi-zero stiffness. The stiffness of the vibration isolation device is the sum of the stiffness of the inner and outer springs, similar to ordinary vibration isolation devices.

[0033] like Figure 6 As shown, after current is passed through the electromagnetic coil, the upper coil 6 will generate electromagnetic force on the middle permanent magnet 14 and the lower permanent magnet 4, and the lower coil 3 will generate electromagnetic force on the middle permanent magnet 3 and the upper permanent magnet 13. According to Ampere's law, the electromagnetic force is proportional to the current, that is, the additional negative stiffness is proportional to the current. When the current increases, the total negative stiffness will increase, and the excitation force corresponding to the vibration isolation device in the quasi-zero stiffness range will decrease. Therefore, for simple harmonic excitations of different magnitudes, changing the magnitude of the current can make the vibration isolation device be in the optimal vibration isolation working state.

[0034] When the vibration isolation device is subjected to harmonic excitation generated by the isolated equipment, it should be ensured that the device always operates within the quasi-zero stiffness range, that is, the outer spring should not participate in vibration isolation for a long time. When the vibration isolation device is subjected to impact excitation, in order to improve the vibration isolation effect, the current in the two electromagnetic coils should be controlled in real time so that the vibration isolation device can return to the quasi-zero stiffness operating range as soon as possible.

[0035] The isolation effect of different stiffnesses of the device under different excitations varies greatly. The technical solution adopted to solve the above technical problems is: by designing the vibration isolation device to have quasi-zero stiffness characteristics, the helical spring provides positive stiffness, and the magnetic force between permanent magnets provides basic negative stiffness. The combination of the two forms the quasi-zero stiffness of the device, giving it a basic passive vibration isolation capability in a wide frequency range. When the passive vibration isolation effect of the device is not good, the electromagnetic force generated by energizing the electromagnetic coil provides additional variable stiffness to adjust the overall stiffness of the device and improve the vibration isolation effect.

[0036] The formula for the force between permanent magnets is:

[0037] To achieve quasi-zero stiffness, this invention uses a helical spring as a positive stiffness structural component and permanent magnets as a negative stiffness structural component, connected in parallel. The total passive stiffness of the vibration isolation device is the sum of the stiffnesses of the two components. Quasi-zero stiffness is essentially a nonlinear stiffness, and the magnetic force between permanent magnets is also nonlinear. The helical spring is usually simplified as linear stiffness. Therefore, the nonlinear force between permanent magnets can be used to achieve the nonlinear characteristic of quasi-zero stiffness. Since the force between permanent magnets is inversely proportional to the square of the relative distance between their magnetic poles, the distance between the magnetic poles of permanent magnets should be within a small range to provide sufficient negative stiffness. The reliable deformation of the helical spring should be greater than or equal to the limit distance between the magnetic poles of permanent magnets.

[0038] In order to achieve variable stiffness characteristics, this invention uses an electromagnetic coil as an additional negative stiffness structural component. The magnitude of the generated electromagnetic force is controlled by controlling the current in the coil, and the attraction of the electromagnetic force on the permanent magnet is used as an additional source of negative stiffness. The passive stiffness is connected in parallel with this additional negative stiffness to obtain the total stiffness of the vibration isolation device.

[0039] To ensure that both ends of the vibration isolation device have the same vibration isolation performance, the permanent magnet, helical spring and coil are arranged in opposite directions and coaxially to ensure that the movement of the permanent magnet to both sides is symmetrical, and one end of the coil is coplanar with the extreme position of the permanent magnet pole.

[0040] This invention utilizes the magnetic force generated by the electromagnetic coil and permanent magnet as negative stiffness, and uses a helical spring to provide positive stiffness to achieve the quasi-zero stiffness characteristic of the vibration isolation device. When the vibration isolation device is subjected to different excitations, the stiffness characteristics of the vibration isolation device can be changed by simply adjusting the current in the electromagnetic coil to adapt to the excitation, always maintaining the quasi-zero stiffness characteristic, realizing real-time adjustment, achieving better low-frequency vibration isolation effect, solving the problem that existing vibration isolation devices can only isolate vibrations within a specific frequency range, realizing wide-frequency domain vibration isolation, and at the same time, the control of the vibration isolation device is also very simple.

Claims

1. A stiffness-adjustable electromagnetic quasi-zero stiffness vibration isolation device, characterized in that: The application relates to a vibration isolation device, which comprises a support lower outer shell (1), a lower end cover (2), a lower coil (3), a lower permanent magnet (4), a top block (5), an upper coil (6), a support upper outer shell (7), an upper end cover (8), a shaft (9), an upper outer spring (10), a permanent magnet upper shell (11), an upper inner spring (12), an upper permanent magnet (13), an intermediate permanent magnet (14), a permanent magnet lower shell (15), a lower inner spring (16) and a lower outer spring (17). The support lower outer shell (1), the support upper outer shell (7), the upper end cover (8), the lower end cover (2), the upper coil (6) and the lower coil (3) form a basic assembly of the vibration isolation device, wherein the support upper outer shell (7) is connected with the support lower outer shell (1), the upper end cover (8) and the lower end cover (2) are respectively connected with the corresponding upper and lower outer shells, the upper coil (6) and the lower coil (3) are coaxially and rigidly connected in the support upper outer shell (7) and the support lower outer shell (1) by using metal glue, and the basic assembly is rigidly connected with a mounting base through the holes on the flanges of the support lower outer shell (1) by using bolts. The shaft (9), the intermediate permanent magnet (14) and the top block (5) form a linear motion structure assembly, the axial positioning of the intermediate permanent magnet (14) is realized by a step on the shaft, the circumferential positioning is realized by the cooperation between the inner space of the permanent magnet and the shaft (9), and one end of the shaft (9) is connected with external loads through threads. The upper permanent magnet (13), the lower permanent magnet (4), the permanent magnet upper shell (11) and the permanent magnet lower shell (15) form a negative stiffness assembly, wherein the permanent magnet upper shell (11) and the permanent magnet lower shell (15) are connected by being matched with threads, the upper permanent magnet (13) and the lower permanent magnet (4) are coaxially and rigidly connected in the permanent magnet upper shell (11) and the permanent magnet lower shell (15) by using metal glue, one end of the upper inner spring (12) is abutted against the step of the shaft (9), the other end is abutted against the upper end cover (8), one end of the lower inner spring (16) is abutted against the top block (5), the other end is abutted against the lower end cover (2), the linear motion structure assembly and the basic assembly are elastically connected through the upper inner spring (12) and the lower inner spring (16), one end of the upper outer spring (10) is abutted against the recess of the permanent magnet upper shell (11), the other end is abutted against the support upper outer shell (7), one end of the lower outer spring (17) is abutted against the recess of the permanent magnet lower shell (15), the other end is abutted against the support lower outer shell (1), the recess is used for the axial positioning of the two outer springs, and the negative stiffness assembly and the basic assembly are elastically connected through the upper outer spring (10) and the lower outer spring (17).

2. The stiffness-adjustable electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The basic assembly, the linear motion structure assembly and the negative stiffness assembly are all made of low-permeability materials, and the relative magnetic permeability of the materials is higher than 2.

3. The stiffness-adjustable electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The intermediate permanent magnet (14) has a 6mm interval with the upper permanent magnet (13) and the lower permanent magnet (4), the working stroke of the upper inner spring (12) and the lower inner spring (16) after pre-tightening should be greater than 6mm, the working stroke of the outer spring is set to 5mm, that is, the working stroke of the upper outer spring (10) and the lower outer spring (17) after pre-tightening is 5mm, the upper inner spring (12), the lower inner spring (16), the upper outer spring (10) and the lower outer spring (17) are all selected as helical compression springs, based on this, the movement stroke of the permanent magnet is 22mm, and the quasi-zero stiffness working stroke is 12mm.

4. The stiffness-adjustable electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that, The support upper shell (7) and the support lower shell (1) are connected through threads.

5. The stiffness-adjustable electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that, The upper end cover (8) and the lower end cover (2) are respectively connected with the corresponding upper shell and lower shell through threads.

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