A dielectric elastomer-based active-passive integrated vibration isolator

Abstract

The application relates to a dielectric elastomer-based active-passive integrated vibration isolator, mainly comprising a quasi-zero stiffness vibration isolation part (1), a vibration active control part (2), a guide shaft (3) and a spring supporting base (4), wherein the quasi-zero stiffness vibration isolation part (1) comprises a nonlinear stiffness element supporting spring (10), a nonlinear stiffness element (11) and a stop piece (12); the vibration active control part (2) comprises a dielectric elastomer supporting spring (20) and a dielectric elastomer (23) fixed between a dielectric elastomer fixed inner frame (21) and a dielectric elastomer fixed outer frame (22). Compared with the prior art, the application has the advantages that a lower inherent frequency can be obtained through the combination of positive and negative stiffness, meanwhile, a larger bearing capacity is achieved; the dielectric elastomer (23) is combined with a linear spring, so that the stress and strain are larger; a larger bandwidth of disturbance can be isolated through active-passive integration, and different external excitations can be adapted.

Description

Technical Field

[0001] This invention relates to a vibration isolator, and more particularly to an integrated active and passive vibration isolator based on a dielectric elastomer. Background Technology

[0002] In engineering, vibration of mechanical equipment is a prevalent and highly concerning issue. These vibrations can cause significant deformation and stress, far exceeding the static working load, which can adversely affect the normal operation of the equipment. For example, during spacecraft operation in orbit, the stepping motion of onboard actuators and controllable components (flywheels, control moment gyroscopes), as well as the flutter of large flexible attachments, can generate disturbances. These vibrations can affect the normal operation of precision instruments on spacecraft, causing inaccurate measurement results and performance failures, or even fatigue damage to the instrument structure. To mitigate this impact, vibration isolators are typically added between the vibration source and the vibrating object to isolate and suppress the vibration. Traditional linear vibration isolation systems can effectively isolate and suppress mid-to-high frequency vibrations above 10Hz, but their isolation capability for low-frequency and ultra-low-frequency vibrations below 10Hz is poor, failing to meet the requirements of ultra-high precision instruments for isolating low-frequency vibrations. Although existing nonlinear vibration isolators can achieve high static stiffness and low dynamic stiffness at the equilibrium position, research on integrated nonlinear vibration isolation and active vibration isolators is limited.

[0003] A search revealed that patent announcement number CN107654551B discloses a multi-degree-of-freedom low-frequency vibration isolator based on the coupling of vibration modes and pendulum modes. Specifically, it comprises two identical, symmetrically arranged high static-low dynamic stiffness isolators. The support rods of the two isolators are connected to a spatial pendulum mechanism via two ball joints. Each isolator is composed of a helical spring and a magnetic negative stiffness mechanism. The helical spring provides positive stiffness support along the axial direction. The magnetic negative stiffness spring consists of three attractive ring permanent magnets, providing nonlinear restoring force and negative stiffness characteristics in the vertical direction. The high static-low dynamic stiffness isolators are kinematically coupled to the spatial pendulum mechanism via two ball joints, resulting in quasi-zero stiffness characteristics and geometric nonlinear damping in the horizontal direction, effectively isolating the low-frequency vibrations of the isolated object in three translational directions. However, the design and manufacture of this vibration isolator system are relatively complex, requiring the use of various components and mechanisms, and assembly is difficult. Authorization announcement number CN108708927B discloses a variable stiffness vibration isolator based on a multilayer dielectric elastomer film. Specifically, the isolator includes a multilayer dielectric elastomer film spring and multiple ring magnets. The multilayer dielectric elastomer film spring employs a method of stacking multiple layers of dielectric elastomer film and multiple layers of conductive electrodes, with adjacent conductive electrodes having opposite polarities. The isolator utilizes the nonlinear restoring force generated by the mutually attracting ring magnets to achieve nonlinear negative stiffness. By changing the driving voltage applied to the conductive electrodes of the multilayer dielectric elastomer film spring, a matching positive stiffness is achieved. The combination of positive and negative stiffness realizes quasi-zero stiffness near the operating position, effectively reducing the natural frequency of the vibration isolation system. However, its vibration isolation bandwidth is limited by the stiffness adjustment range. In vibration environments with large frequency variations or wide bandwidths, the performance of the vibration isolation system may be unstable. Authorization announcement number CN213808606U discloses a quasi-zero stiffness vibration isolator with a parallel mechanism of positive and negative stiffness. Specifically, it discloses an isolating mass mounting frame, with a mass block fixed to the top of the frame, and a positive stiffness spring mounting frame connected to the bottom via a positive stiffness spring. It mainly achieves zero stiffness by vertically setting the positive stiffness spring and horizontally setting the negative stiffness spring, ensuring that the springs do not bend or deform. However, when the vibration amplitude is large, this device cannot provide a stable vibration isolation effect.Authorization announcement number CN105673769B discloses an integrated active and passive vibration isolator and vibration isolation method using composite dielectric elastic material. Specifically, the isolator includes upper and lower end caps, with upper and lower connectors fixed to the end caps by screws. A pre-stretched composite dielectric elastic film is composed of a fiber-core dielectric elastic material film and a single-layer dielectric elastic material film. Conductive carbon paste is applied to the upper and lower surfaces of the fiber-core film's driving area. The composite dielectric elastic film in the non-driving area is wound between the upper and lower end caps, with its conductive leads led out through double-sided conductive copper foil. A linear flange bearing is fitted into the center of the upper end cap, and an intermediate shaft is fitted into the linear flange bearing with a clearance fit and connected to the lower end cap by threads. The upper and lower ends of a built-in compression spring are fixed to the upper and lower end caps. Utilizing the principle of composite dielectric elastic material and built-in compression springs, large deformation, high damping, and integrated active and passive vibration isolation control are achieved. However, the stress generated by the pre-stretched single-layer dielectric elastic body is relatively small, resulting in a generally limited active vibration suppression effect and the inability to achieve large stress driving.

[0004] In summary, existing vibration isolators suffer from one or more problems, such as complex structure, unstable performance, and low load-bearing capacity. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide an integrated active and passive vibration isolator based on a dielectric elastomer.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, an integrated active and passive vibration isolator based on a dielectric elastomer is provided. The isolator is placed above a vibration source and includes a quasi-zero stiffness isolation section, an active vibration control section, a guide shaft, a spring support base, an upper end cover, a lower end cover, an isolator cover plate, and an isolator bottom shell. The object being isolated is in contact with the upper end cover. The quasi-zero stiffness isolation section includes a nonlinear stiffness element support spring sleeved on the guide shaft, a nonlinear stiffness element passing through the small end of the guide shaft, and a stop plate. One end of the nonlinear stiffness element support spring is in contact with the nonlinear stiffness element. The other end is fixed in the groove of the spring support base; the vibration active control part includes a dielectric elastomer support spring and a dielectric elastomer assembly sleeved on the guide shaft. The dielectric elastomer assembly includes a dielectric elastomer fixing inner frame, a dielectric elastomer fixing outer frame, and a dielectric elastomer fixed between the dielectric elastomer fixing inner frame and the dielectric elastomer fixing outer frame. The upper end of the dielectric elastomer support spring is fixed in the groove of the upper end cover, and the lower end is fixed in the groove of the spring support base. The dielectric elastomer fixing inner frame is fixed in the grooves on the outside of the upper end cover and the lower end cover.

[0008] As a preferred technical solution, the nonlinear stiffness element is composed of more than one nonlinear stiffness unit stacked together.

[0009] As a preferred technical solution, the nonlinear stiffness element is a cross-shaped rigid sheet with a thickness of 0.4 mm.

[0010] As a preferred technical solution, the nonlinear stiffness element is fixed in the groove of the upper end cover by a first nut and a stop plate.

[0011] As a preferred technical solution, the large end of the guide shaft passes through the spring support base and the bottom shell of the vibration isolator in sequence and is fixed to the bottom shell of the vibration isolator through the second nut. The nonlinear stiffness element support spring sleeved on the guide shaft is located inside the dielectric elastomer support spring.

[0012] As a preferred technical solution, the dielectric elastomer is a stacked structure of more than one dielectric elastomer film, wherein the dielectric elastomer film is a mixed silicone film, with a first electrode layer coated on top and a second electrode layer coated on the bottom.

[0013] As a preferred technical solution, the first electrode layer and the second electrode layer are made of single-walled carbon nanotubes. The first electrode layer and the second electrode layer have opposite polarities, and the adjacent dielectric elastomer film electrodes have the same polarity and are distributed in a cross pattern.

[0014] As a preferred technical solution, the dielectric elastomer is stretched into a conical shape during installation due to the prestress generated by the dielectric elastomer support spring.

[0015] As a preferred technical solution, a cavity is formed between the vibration isolator cover plate and the vibration isolator bottom shell, and the quasi-zero stiffness vibration isolation part and the vibration active control part are placed in the cavity.

[0016] As a preferred technical solution, the dielectric elastomer fixing outer frame, the vibration isolator cover plate and the vibration isolator bottom shell are fixed by the second bolt and the third nut.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1) This invention utilizes the nonlinear restoring force generated by a special-shaped nonlinear stiffness element under a certain load to achieve negative stiffness, and a linear spring provides positive stiffness. The combination of positive and negative stiffness enables the passive vibration isolation part to reach quasi-zero stiffness near the working position, achieving high static stiffness and low dynamic stiffness near the equilibrium position. When the static equilibrium position is reached, the dynamic stiffness is zero or quasi-zero, thereby obtaining a lower natural frequency while having a larger load-bearing capacity.

[0019] 2) This invention combines a multilayer stacked dielectric elastomer with a linear spring. By changing the driving voltage applied to the conductive electrode, the dielectric elastomer is deformed, generating a force in the vertical direction. The driving voltage is controlled to achieve the output of force. The response speed of the dielectric elastomer is in the millisecond range. Its large stress-strain characteristics are suitable for vibration suppression under various complex excitations. At the same time, the inherent damping of the dielectric elastomer itself can also have a good suppression effect on vibration.

[0020] 3) The active vibration control part of this invention has a good effect on suppressing low-frequency and high-frequency disturbances. Nonlinear passive vibration isolation can effectively suppress ultra-low frequency disturbances, and passive vibration isolation can still play a role when active vibration isolation fails. The integration of active and passive vibration can not only isolate disturbances with a large bandwidth, but also adapt to different external excitations.

[0021] 4) The dielectric elastomer of this invention is made of silicone, which has lower viscoelasticity and weaker nonlinearity than traditional acrylic-based dielectric elastomers, and can generate greater stress and strain, is not prone to fatigue, and can be used for high-frequency driving.

[0022] 5) This invention uses a dielectric elastomer with a stacked dielectric elastomer film structure in parallel with a linear spring, which achieves a greater force output compared to a single-layer dielectric elastomer actuator.

[0023] 6) This invention utilizes single-walled carbon nanotubes as flexible electrodes for stacked dielectric elastomers. Single-walled carbon nanotubes have high flexibility and will not adversely affect the deformation of the dielectric elastomer. In addition, when the dielectric elastomer film is punctured, the single-walled carbon nanotubes can automatically degrade into electrical insulators, preventing the problem of the driver failing to continue working due to electrode short circuit. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the active and passive integrated vibration isolator based on dielectric elastomer of the present invention.

[0025] Figure 2 This is a three-dimensional sectional view of the active and passive integrated vibration isolator based on dielectric elastomer of the present invention.

[0026] Figure 3 This is a schematic diagram of the coating of the first electrode layer of the dielectric elastomer film of the present invention;

[0027] Figure 4 This is a schematic diagram of the coating of the second electrode layer of the dielectric elastomer film of the present invention;

[0028] Figure 5 This is a front view of the nonlinear stiffness element of the present invention;

[0029] Figure 1 As indicated by the standard number:

[0030] 1. Quasi-zero stiffness vibration isolation section; 10. Nonlinear stiffness element support spring; 11. Nonlinear stiffness element; 12. Stop plate; 2. Vibration active control section; 20. Dielectric elastomer support spring; 21. Dielectric elastomer fixing inner frame; 22. Dielectric elastomer fixing outer frame; 23. Dielectric elastomer; 3. Guide shaft; 4. Spring support base; 5. Upper end cover; 6. Lower end cover; 7. Vibration isolator cover plate; 8. Vibration isolator bottom shell; 90. First nut; 91. Second nut; 92. Third nut; 93. First bolt; 94. Second bolt;

[0031] Figure 3 As indicated by the standard number:

[0032] 230. Dielectric elastomer film; 231. First electrode layer;

[0033] Figure 4 As indicated by the standard number:

[0034] 232. Second electrode layer. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] This invention proposes an integrated active and passive vibration isolator based on dielectric elastomer 23. This vibration isolator can not only effectively isolate low-frequency and ultra-low-frequency disturbances, but also actively control vibrations. It has advantages such as wide vibration isolation bandwidth and large load-bearing capacity.

[0037] like Figure 1 , Figure 2 As shown, an integrated active and passive vibration isolator based on a dielectric elastomer 23 mainly includes a quasi-zero stiffness vibration isolation part 1 and a vibration active control part 2. The quasi-zero stiffness vibration isolation part 1 includes a nonlinear stiffness element support spring 10, a nonlinear stiffness element 11, and a stop plate 12. The nonlinear stiffness element 11 is a cross-shaped rigid sheet with a thickness of 0.4 mm, such as... Figure 4The diagram shows one shape configuration of the nonlinear stiffness element 11, which is composed of multiple (more than one) nonlinear stiffness units stacked together. The vibration active control part 2 includes a dielectric elastomer support spring 20, a dielectric elastomer fixing inner frame 21, a dielectric elastomer fixing outer frame 22, and a dielectric elastomer 23. The quasi-zero stiffness isolation part 1, the vibration active control part 2, the guide shaft 3, the spring support base 4, the upper end cover 5, the lower end cover 6, the vibration isolator cover plate 7, the vibration isolator bottom shell 8, the first nut 90, the second nut 91, the third nut 92, the first bolt 93, and the second bolt 94 constitute the complete vibration isolator of this invention. In use, the object being isolated is in contact with the upper part of the upper end cover 5, and the vibration isolator is placed on the vibration source.

[0038] like Figure 3 As shown, the dielectric elastomer 23 is a multilayer dielectric elastomer film 230 stacked structure. The stacked multilayer dielectric elastomer films 230 are pressed and fixed by the dielectric elastomer fixing inner frame 21 and the dielectric elastomer fixing outer frame 22. The dielectric elastomer fixing inner frame 21 and the dielectric elastomer fixing outer frame 22 are both made of fiber-reinforced composite materials. The dielectric elastomer film 230 is a mixed silicone film. Compared with traditional acrylic-based dielectric elastomers, the mixed silicone film has lower viscoelasticity and weaker nonlinearity, and can generate greater stress and strain, is less prone to fatigue, and can be used for high-frequency driving. Each dielectric elastomer film 230 has two annular electrodes on each of its two sides. The two annular electrodes coated on the upper surface are the first electrode layer 231, with positive polarity; the two annular electrodes coated on the lower surface are the second electrode layer 232, with negative polarity. The first electrode layer 231 and the second electrode layer 232... The electrode layer 232 is made of single-walled carbon nanotubes. Single-walled carbon nanotubes have high flexibility and will not adversely affect the deformation of the dielectric elastomer 23. When the dielectric elastomer film 230 is punctured, the single-walled carbon nanotubes can automatically degrade into electrical insulators, preventing the actuator from malfunctioning due to electrode short circuits. A single dielectric elastomer actuator is obtained by folding along the centerline of the single-layer dielectric elastomer film 230. After folding, the first electrode layer 231 is on the outer surface, and the second electrode layer 232 is on the inner surface. The electrodes of adjacent dielectric elastomer films 230 in the multilayer dielectric elastomer film 230 have the same polarity and are distributed in a cross pattern. During installation, the dielectric elastomer 23 is stretched into a conical shape due to the prestress generated by the dielectric elastomer support spring 20.

[0039] Both ends of the guide shaft 3 are threaded. The small end of the guide shaft 3 passes through the nonlinear stiffness element 11 and the stop plate 12 in sequence. The large end of the guide shaft 3 passes through the spring support base 4 and the vibration isolator bottom shell 8 in sequence and is fixed to the vibration isolator bottom shell 8 through the second nut 91. The nonlinear stiffness element support spring 10 and the dielectric elastomer support spring 20 are sleeved on the guide shaft 3. The nonlinear stiffness element support spring 10 is located inside the dielectric elastomer support spring 20.

[0040] The spring support base 4 is located on the groove of the bottom shell 8 of the vibration isolator. The spring support base 4 has two grooves. One end of the nonlinear stiffness element supporting spring 10 is in contact with the nonlinear stiffness element 11; the other end is fixed in the groove inside the spring support base 4. The other end of the dielectric elastomer supporting spring 20 is fixed in the groove outside the spring support base 4.

[0041] The upper end cover 5 and the lower end cover 6 are connected by the first bolt 93, forming a cavity structure in the middle. The guide shaft 3 and the nonlinear stiffness element support spring 10 and dielectric elastomer support spring 20, which are sleeved on it, are all located in the cavity. The upper end cover 5 has a groove on its upper part, and the nonlinear stiffness element 11 is placed in the groove on the upper part of the upper end cover 5. The stop plate 12 is placed on the nonlinear stiffness element 11, and the nonlinear stiffness element 11 is fixed by the stop plate 12 and the first nut 90. The upper end cover 5 and the lower end cover 6 have grooves on their outer sides, and the dielectric elastomer fixing inner frame 21 is fixed in the grooves on the outer sides of the upper end cover 5 and the lower end cover 6.

[0042] The dielectric elastomer fixing outer frame 22 is located between the vibration isolator cover plate 7 and the vibration isolator bottom shell 8. The dielectric elastomer fixing outer frame 22, the vibration isolator cover plate 7 and the vibration isolator bottom shell 8 are fixed by the second bolt 94 and the third nut 92. A cavity is formed between the vibration isolator cover plate 7 and the vibration isolator bottom shell 8. The quasi-zero stiffness vibration isolation part 1 and the vibration active control part 2 are placed in the cavity.

[0043] The working principle of an integrated active and passive vibration isolator based on a dielectric elastomer 23 according to the present invention is explained below:

[0044] When the vibration isolator is in an unexcited state, the nonlinear stiffness element 11 is adjusted to the negative stiffness equilibrium position by the first nut 90. At this time, the nonlinear stiffness element 11, the nonlinear stiffness element support spring 10, the voltage-undriven dielectric elastomer 23, and the dielectric elastomer support spring 20 are all in a balanced state. When the vibration isolator bottom shell 8 is subjected to external excitation, the nonlinear stiffness element 11 will move slightly along the vertical direction near the equilibrium position and generate negative stiffness, forming a quasi-zero stiffness system with the positive stiffness nonlinear stiffness element support spring 10. At the same time, the vibration active control part 2 starts to work, and the driving voltage is applied to the dielectric elastomer 2. On the electrodes on both sides, the electrodes are connected in series with the conductive paste through wires and an external power supply. Current flows from the positive electrode to the negative electrode on the surface of the dielectric elastomer film 230 through the external wires, causing the electrodes on both sides to carry charges of opposite polarity. The dielectric elastomer 23 deforms under the action of Maxwell stress. Since the dielectric elastomer 23 is incompressible, it contracts in the direction perpendicular to the surface of the dielectric elastomer film 230, while stretching in the horizontal direction along the film surface. The dielectric elastomer support spring 20 releases the prestress, which drives the cavity formed by the upper end cover 5 and the lower end cover 6 to move and generate force and displacement. The input electrical energy is converted into mechanical energy.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dielectric elastomer based active-passive integrated vibration isolator, which is placed on a vibration source, characterized in that, The invention relates to a vibration isolator, comprising a quasi-zero stiffness vibration isolation part (1), an active vibration control part (2), a guide shaft (3), a spring support base (4), an upper end cover (5), a lower end cover (6), a vibration isolator cover plate (7) and a vibration isolator bottom shell (8), wherein the object to be isolated is in contact with the upper end cover (5), the quasi-zero stiffness vibration isolation part (1) comprises a nonlinear stiffness element supporting spring (10) sleeved on the guide shaft (3), a nonlinear stiffness element (11) passing through the small end of the guide shaft (3) and a stop piece (12), one end of the nonlinear stiffness element supporting spring (10) is in contact with the nonlinear stiffness element (11), and the other end is fixed in the groove of the spring support base (4); the active vibration control part (2) comprises a dielectric elastomer supporting spring (20) sleeved on the guide shaft (3) and a dielectric elastomer assembly, the dielectric elastomer assembly comprises a dielectric elastomer fixed inner frame (21), a dielectric elastomer fixed outer frame (22) and a dielectric elastomer (23) fixed between the dielectric elastomer fixed inner frame (21) and the dielectric elastomer fixed outer frame (22), the upper end of the dielectric elastomer supporting spring (20) is fixed in the groove of the upper end cover (5), and the lower end is fixed in the groove of the spring support base (4), the dielectric elastomer fixed inner frame (21) is fixed in the groove outside the upper end cover (5) and the lower end cover (6); the large end of the guide shaft (3) passes through the spring support base (4) and the vibration isolator bottom shell (8) in sequence and is fixed with the vibration isolator bottom shell (8) by a second nut (91); a cavity is formed between the vibration isolator cover plate (7) and the vibration isolator bottom shell (8), and the quasi-zero stiffness vibration isolation part (1) and the active vibration control part (2) are placed in the cavity; the spring support base (4) is located on the groove of the vibration isolator bottom shell (8); the dielectric elastomer fixed outer frame (22), the vibration isolator cover plate (7) and the vibration isolator bottom shell (8) are fixed by a second bolt (94) and a third nut (92).

2. The dielectric elastomer based active-passive integrated vibration isolator according to claim 1, wherein, the nonlinear stiffness element (11) is stacked by more than one nonlinear stiffness unit.

3. The dielectric elastomer based active-passive integrated vibration isolator according to claim 1, wherein, the nonlinear stiffness element (11) is a cross-shaped rigid sheet with a thickness of 0.4 mm.

4. The dielectric elastomer based active-passive integrated vibration isolator according to claim 1, wherein, the nonlinear stiffness element (11) is fixed in the groove of the upper end cover (5) by a first nut (90) and a stop piece (12).

5. The dielectric elastomer based active-passive integrated vibration isolator according to claim 1, wherein, the nonlinear stiffness element supporting spring (10) sleeved on the guide shaft (3) is located inside the dielectric elastomer supporting spring (20).

6. The dielectric elastomer based active-passive integrated vibration isolator according to claim 1, wherein, the dielectric elastomer (23) is a stacked structure of more than one dielectric elastomer film (230), the dielectric elastomer film (230) is a mixed silica gel film, the upper surface of which is coated with a first electrode layer (231) and the lower surface of which is coated with a second electrode layer (232).

7. The dielectric elastomer based active-passive integrated vibration isolator according to claim 6, wherein, the materials of the first electrode layer (231) and the second electrode layer (232) are single-walled carbon nanotubes, the polarities of the first electrode layer (231) and the second electrode layer (232) are opposite, the polarities of the electrodes of adjacent dielectric elastomer films (230) are the same and are distributed in a cross pattern.

8. The dielectric elastomer based active-passive integrated vibration isolator according to claim 6, wherein, The dielectric elastomer (23) is stretched in a conical shape due to the prestress of the dielectric elastomer support spring (20) at the time of installation.

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