CN114151507A - Quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping - Google Patents

Quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping Download PDF

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CN114151507A
CN114151507A CN202111505433.9A CN202111505433A CN114151507A CN 114151507 A CN114151507 A CN 114151507A CN 202111505433 A CN202111505433 A CN 202111505433A CN 114151507 A CN114151507 A CN 114151507A
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stiffness
vertical
worm
quasi
negative stiffness
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CN114151507B (en
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杨庆超
楼京俊
柴凯
刘树勇
段金生
李广灵
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Naval University of Engineering PLA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
    • F16F15/03—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using magnetic or electromagnetic means
    • F16F15/035—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using magnetic or electromagnetic means by use of eddy or induced-current damping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
    • F16F15/04—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means
    • F16F15/06—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using elastic means with metal springs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2222/00—Special physical effects, e.g. nature of damping effects
    • F16F2222/06—Magnetic or electromagnetic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2228/00—Functional characteristics, e.g. variability, frequency-dependence
    • F16F2228/06—Stiffness
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

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  • Vibration Prevention Devices (AREA)

Abstract

The invention discloses a quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping, which comprises a vibration isolation box body, and an anti-overturning device, a negative stiffness electromagnetic adjusting device, a positive stiffness spring adjusting device and a vertical eddy current damping device which are arranged in the vibration isolation box body; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive stiffness spring adjusting device is arranged in the central area; the vertical eddy current damping device comprises two vertical eddy current damping modules which are oppositely arranged and are positioned outside a central area between the two negative stiffness generating modules, and the vertical eddy current damping modules are connected with the negative stiffness generating modules. The invention has the beneficial effects that: the invention has very low dynamic stiffness near the static equilibrium position; the vertical damping is increased, so that the system resonance can be effectively inhibited, and the stability of the vibration isolation system is improved.

Description

Quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping
Technical Field
The invention relates to the technical field of vibration isolation, in particular to a quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping.
Background
In the engineering field, vibration is one of important factors causing faults, and the traditional linear stiffness vibration isolator has good isolation effect on medium-frequency and high-frequency vibration, but has unsatisfactory isolation effect on low-frequency vibration. And the linear vibration isolation system is only used when the excitation frequency is greater than the natural frequency of the system
Figure BDA0003404128540000011
The vibration isolation effect is achieved at double times. Therefore, the vibration isolation system has low-frequency vibration isolation performance only by reducing the natural frequency of the vibration isolation system, the common method is to reduce the system stiffness, but too low stiffness reduces the bearing capacity, so that the static displacement is too large, the system stability is insufficient, and the linear vibration isolation system cannot give consideration to both high bearing capacity and low-frequency vibration isolation performance. In order to improve the low-frequency vibration isolation effect of the vibration isolator, researchers have proposed a large number of novel vibration isolation devices.
The utility model discloses a patent of "a quasi-zero rigidity damping platform that can adjust in a flexible way" with publication number CN 204852123U, this utility model is formed by fixed platform, movable platform, damping subassembly and thrust subassembly, the damping subassembly is connected with movable platform and fixed platform, the thrust subassembly is set up on the fixed platform, is used for exerting thrust to the movable platform, the thrust subassembly sets up a plurality ofly around the movable platform; the invention discloses a quasi-zero stiffness vibration isolator with negative stiffness generated by a ring-shaped permanent magnet, and the isolator is CN 104455181B, and provides a quasi-zero stiffness vibration isolator with negative stiffness generated by a ring-shaped permanent magnet. The utility model discloses a utility model patent of "cut formula quasi-zero rigidity isolator" for publication number CN 205824020U, discloses a cut formula quasi-zero rigidity isolator, and this isolator has the low dynamic stiffness characteristic of high quiet rigidity based on the parallelly connected principle of positive and negative rigidity structure. The invention discloses a quasi-zero stiffness vibration isolator with horizontal damping, which is a patent of 'a quasi-zero stiffness vibration isolator with horizontal damping', and discloses a quasi-zero stiffness vibration isolator with horizontal damping, wherein two groups of cam-roller-spring mechanisms are horizontally and symmetrically arranged to serve as negative stiffness structures, and are additionally provided with horizontal dampers, and then are connected in parallel with vertically arranged positive stiffness spring structures to jointly form a quasi-zero stiffness vibration isolation mechanism. However, the existing vibration isolation device generally has the problems of unadjustable negative stiffness or inconvenient adjustment, so that the bearing range is limited, and the vibration isolation device cannot be well applied to engineering practice; secondly, the existing vibration isolation devices have relatively obvious formants at low-frequency resonance points, and the vibration isolation effect at the resonance points is poor; in addition, the existing vibration isolation device is not compact enough in structure and limited in bearing capacity, is generally only suitable for specific vibration isolation objects, and is poor in universality.
The bearing capacity of the quasi-zero stiffness vibration isolator with the positive stiffness element and the negative stiffness element connected in parallel depends on the positive stiffness element, the negative stiffness element can reduce the dynamic stiffness of the system, the characteristics of high static stiffness for supporting isolated equipment and low dynamic stiffness for reducing the vibration transfer rate can be obtained, the low-frequency vibration isolation performance near a working point can be ensured, the stability of the system can be improved, and the quasi-zero stiffness vibration isolator has a wide application prospect. However, the installation space on the ship is limited, the engineering vibration isolator must be designed compactly, and the existing negative stiffness mechanism is often an inclined spiral spring, an inclined connecting rod or a buckling beam and occupies a large space. In addition, the quasi-zero stiffness vibration isolator is a combined type vibration isolator which has smaller combined stiffness within a certain interval of a static balance position. If the weight of the object to be subjected to vibration isolation is not the designed ideal weight, namely the object to be subjected to vibration isolation is placed on the quasi-zero stiffness vibration isolator and cannot be stabilized at the ideal static balance position, the performance of the quasi-zero stiffness vibration isolator is seriously influenced. Meanwhile, a relatively obvious resonance peak generally exists at a resonance point, and the vibration isolation effect is poor, so that the vibration isolation system vibrates violently, and the instability of the vibration isolation system is increased.
Disclosure of Invention
The invention aims to provide a quasi-zero stiffness vibration isolator capable of inhibiting system resonance and adjusting electromagnetic negative stiffness and vertical eddy current damping, aiming at the defects of the prior art.
The technical scheme adopted by the invention is as follows: a quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping comprises a vibration isolation box body, and an anti-overturning device, a negative stiffness electromagnetic adjusting device and a positive stiffness spring adjusting device which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform, an upper supporting platform and four side plates enclosed between the upper and lower supporting platforms; the anti-overturning device comprises four anti-overturning mechanisms which are sequentially arranged end to end, and the top and the bottom of each anti-overturning mechanism are respectively connected and fixed with the upper supporting platform and the lower supporting platform; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive stiffness spring adjusting device is arranged in the central area and comprises a worm and gear mechanism and a spiral spring, the worm and gear mechanism is arranged on the lower supporting platform, the input end of the worm and gear mechanism penetrates through the side plate to extend out of the vibration isolation box body, the output end of the worm and gear mechanism is connected with the spiral spring, the spiral spring is vertically arranged, and the worm and gear mechanism can drive the spiral spring to move along the vertical direction; the vertical eddy current damping device comprises two vertical eddy current damping modules which are oppositely arranged and are positioned outside a central area between the two negative stiffness generating modules, and the vertical eddy current damping modules are connected with the negative stiffness generating modules.
According to the scheme, each negative stiffness generating module comprises a C-shaped yoke and a permanent magnet, and the bottom and the top of the C-shaped yoke are respectively connected with the upper supporting platform and the lower supporting platform; the open sides of the C-shaped yokes of the two negative stiffness generating modules are opposite; an upper middle yoke and a lower middle yoke are arranged in the opening of the C-shaped yoke, and a coil A is wound outside the two middle yokes to form an electromagnet A; the permanent magnet and the two electromagnets A are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet is positioned between the two electromagnets A, and the three electromagnets form a closed magnetic loop in the C-shaped yoke; the permanent magnet is connected with the upper supporting platform through the supporting plate.
According to the scheme, the supporting plates of the two negative stiffness generating modules are connected through a connecting plate, a height indicating needle is arranged on the connecting plate, and the height indicating needle and the permanent magnet are located at the same height; one end of the height indicating needle extends out of the side plate.
According to the scheme, the supporting plate is an L-shaped supporting plate, the top of the vertical section of the supporting plate is connected with the upper supporting platform, and the horizontal section of the supporting plate is provided with the permanent magnet; the connecting plate is connected with the vertical section of the supporting plate.
According to the scheme, the negative stiffness generation module is also provided with limiting rubbers which are arranged at the upper end and the lower end of the support structure of the anti-overturning mechanism.
According to the scheme, the vertical eddy current damping module comprises an electromagnet B and a copper plate which are arranged in parallel at intervals, wherein the electromagnet B is composed of an outer yoke wound with a coil B; the copper plate is fixed on the connecting plate and can move up and down along with the connecting plate to cut the magnetic induction line of the electromagnet B.
According to the scheme, each anti-overturning mechanism is provided with a supporting structure, and the supporting structure comprises a first fixed block, a second fixed block, a third fixed block, a fourth fixed block, a plurality of transverse reeds and a plurality of vertical reeds, wherein the first fixed block, the second fixed block and the third fixed block are connected with a lower supporting platform; the second fixed block is arranged at the upper part of the first fixed block and is connected with the third fixed block through at least one transverse reed; the third fixed block is connected with the fourth fixed block through at least one vertical reed.
According to the scheme, the worm and gear mechanism comprises a plurality of supports, a worm and a worm gear, wherein the supports are arranged on the lower supporting platform at intervals; the worm sequentially penetrates through the supports and then extends out of the operation hole in the side plate; the worm is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt, and the bottom of the vertical bolt is connected with the lower supporting platform; the spiral spring is coaxially matched with the turbine, the upper end of the spiral spring is in contact with the inner top of the upper supporting platform, the lower end of the spiral spring is fixed on the turbine, and when the worm is rotated, the turbine rotates along with the spiral spring and drives the spiral spring to lift along the axis direction of the vertical bolt.
According to the scheme, the positive stiffness spring adjusting device is further provided with two groups of limiting mechanisms which are symmetrically distributed on the outer sides of the spiral springs, each limiting mechanism comprises a limiting rod and a limiting block, the limiting rods are vertically arranged, and the lower ends of the limiting rods are connected with the lower supporting platform; the limiting block is fixed on the limiting rod.
According to the scheme, the C-shaped yoke and the middle yoke are made of DT4C materials, and the permanent magnet is made of rare earth permanent magnet materials.
The invention has the beneficial effects that:
the quasi-zero stiffness vibration isolator has the characteristics of low natural frequency and high static bearing capacity, and can ensure that the resonance frequency is very low on the premise of ensuring the bearing capacity, thereby widening the vibration isolation frequency band and improving the vibration isolation effect; and the positive stiffness and the negative stiffness can be adjusted according to actual requirements. The invention has very low dynamic stiffness near the static balance position, the increase of vertical damping can effectively inhibit system resonance, the stability of the vibration isolation system is improved, the structure is simple, the maintenance is convenient, and the invention is suitable for low-frequency and even ultra-low frequency vibration isolation.
Drawings
Fig. 1 is a schematic overall structure diagram of an embodiment of the present invention.
Fig. 2 is a top view of the present embodiment without the upper support platform.
Fig. 3 is a schematic connection diagram of the anti-overturning device, the negative stiffness electromagnetic adjusting device, the positive stiffness spring adjusting device and the vertical eddy current damping device in this embodiment.
Fig. 4 is an assembly view of the overturn preventing device in this embodiment.
Fig. 5 is an assembly diagram of the negative stiffness electromagnetic adjustment device in the present embodiment.
Fig. 6 is an assembly diagram of the positive rate spring adjusting device in the present embodiment.
Fig. 7 is an assembly diagram of the vertical eddy current damping device according to the present embodiment.
Fig. 8 is a graph showing the damping force of the vertical eddy current damping module according to the present embodiment as a function of the moving speed of the copper plate and the coil current.
Fig. 9 is a schematic diagram of unit vector, velocity and magnetic flux density components of the vertical eddy current damping module in this embodiment.
Wherein: 1. a lower support platform; 2. a machine leg; 3. a bolt A; 4. a side plate; 5. an upper support platform; 6. a bolt B; 7. an operation hole; 8. a wire hole; 9. a display aperture; 10. a negative stiffness electromagnetic adjustment device; 11. a positive stiffness spring adjustment device; 12. an anti-toppling device; 13. a bolt C; 14. a bolt D; 15. a transverse spring leaf; 16. a vertical reed; 17. a bolt E; 18. a support structure; 18.1, a first fixed block; 18.2, a second fixed block; 18.3, a third fixed block; 18.4, a fourth fixed block; 19. a C-shaped yoke; 20. a permanent magnet; 21. a coil A; 22. limiting rubber; 23. a height indicating needle; 24. a vertical bolt; 25. a worm and gear mechanism; 26. a worm; 27. a coil spring; 28. a support; 29. a limiting rod; 30. a limiting block; 31. a support plate; 31.1, a vertical section; 31.2, a horizontal section; 32. a connecting plate; 33. an intermediate yoke; 34. a copper plate; 35. an electromagnet B; 36. vertical eddy current damping device.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
The quasi-zero stiffness vibration isolator with adjustable electromagnetic negative stiffness and vertical eddy current damping shown in fig. 1-3 comprises a vibration isolation box body, and an overturn preventing device 12, a negative stiffness electromagnetic adjusting device 10, a positive stiffness spring adjusting device 11 and a vertical eddy current damping device 36 which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform 1, an upper supporting platform 5 and four side plates 4 enclosed between the upper and lower supporting platforms 1; the overturn preventing device 12 comprises four overturn preventing mechanisms which are sequentially arranged end to end, and the top and the bottom of each overturn preventing mechanism are respectively connected and fixed with the upper supporting platform 1 and the lower supporting platform 1; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device 10 comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face to the central area; the positive stiffness spring adjusting device 11 is installed in the central area, the positive stiffness spring adjusting device 11 comprises a worm and gear mechanism 25 and a spiral spring 27, the worm and gear mechanism 25 is installed on the lower supporting platform 1, the input end of the worm and gear mechanism 25 penetrates through the side plate 4 and extends out of the vibration isolation box body, the output end of the worm and gear mechanism 25 is connected with the spiral spring 27, the spiral spring 27 is vertically arranged, and the worm and gear mechanism 25 can drive the spiral spring 27 to move along the vertical direction; the vertical eddy current damping device 36 includes two vertical eddy current damping modules, the two vertical eddy current damping modules are arranged oppositely and located outside the central region between the two negative stiffness generating modules, and the vertical eddy current damping modules are connected with the negative stiffness generating modules.
In the invention, as shown in the vibration isolation box body shown in fig. 1, the lower support platform 1 is connected with the side plate 4 through a plurality of bolts B6, and the bottom of the lower support platform 1 is connected with the machine leg 2 through a bolt A3; the upper supporting platform 5 is connected with the side plate 4 in an embedded mode. The side plate 4 is provided with an operation hole 7 for operating the worm 26, a wire hole 8 for accessing a power wire and a display hole 9 for displaying a balance position.
The anti-overturning device 12 provides torsional rigidity for the whole device, and can effectively prevent the vibration isolator from generating larger torsional amplitude. In the overturn preventing device 12 shown in fig. 4, each overturn preventing mechanism is provided with a supporting structure 18, and the supporting structure 18 comprises a first fixed block 18.1 (which can be connected by bolts) connected with the lower supporting platform 1, a second fixed block 18.2, a third fixed block 18.3, a fourth fixed block 18.4 (which is connected by bolts D14) connected with the upper supporting platform 5, and a plurality of transverse reeds 15 and a plurality of vertical reeds 16; the second fixed block 18.2 is arranged at the upper part of the first fixed block 18.1, and the second fixed block 18.2 is connected with the third fixed block 18.3 through at least one transverse spring 15; the third holding block 18.3 is connected to the fourth holding block 18.4 by at least one vertical spring 16.
In this embodiment, the second fixing block 18.2 is connected to the third fixing block 18.3 through two parallel transverse reeds 15, and the third fixing block 18.3 is connected to the fourth fixing block 18.4 through one vertical reed 16; each reed is respectively connected with the corresponding fixed block through a bolt E17.
The negative stiffness electromagnetic adjusting device 10 adopts a vertical homopolar arrangement form of three magnets as a negative stiffness generating module, and is used for realizing self-adaptive control of the negative stiffness of the quasi-zero stiffness vibration isolator. As shown in fig. 5, the negative stiffness electromagnetic adjusting device 10 includes two negative stiffness generating modules arranged oppositely, each negative stiffness generating module includes a C-shaped yoke 19, a permanent magnet 20, and two intermediate yokes 33 wound with coils a21, the C-shaped yokes 19 are respectively connected (bolted) to the lower support platform 1; the open sides of the C-shaped yokes 19 of the two negative rigidity generation modules are opposite and are positioned below the transverse reeds 16; an upper middle yoke 33 and a lower middle yoke 33 are arranged in an opening of the C-shaped yoke 19, and a coil A21 is wound outside the two middle yokes 33 to form an electromagnet A; the permanent magnet 20 and the electromagnet A are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet 20 is positioned between the two electromagnets A, a closed magnetic loop is formed in the C-shaped yoke 19 by the permanent magnet 20 and the electromagnets A, and a repulsive force is generated between the permanent magnet 20 and the electromagnets A; the permanent magnet 20 is connected to the upper support platform 5 by a support plate 31. In this embodiment, a coil a21 is wound around the middle of the intermediate yoke 33, and the upper end of the intermediate yoke 33 is connected to the upper support platform 5 by a bolt.
In the invention, the support plate 31 is positioned in the central area, the permanent magnet 20 is connected with the upper support platform 5 through the support plate 31 and moves together with the upper support platform 5, and in the moving process, a magnetic field is induced by the permanent magnet and the electromagnets A at the upper end and the lower end, and magnetic force in the same direction as the displacement direction is generated, so that negative rigidity is realized. Coil a21 was connected to the wire leading from wire hole 8 and the negative stiffness of the isolator was controlled by varying the current input to coil a 21. In the closed magnetic loop of the C-shaped yoke 19, the coil A21 of the electromagnet A is not electrified, the middle yoke 33 can induce a magnetic field by the permanent magnet 20 to generate corresponding negative rigidity, and the excitation current in the same direction as the original magnetic field can be input to the coil A21 to enhance the negative rigidity.
Preferably, the support plates 31 of the two negative stiffness generating modules are connected through a connecting plate 32, the connecting plate 32 is provided with a height indicating pin 23, and the height indicating pin 23 and the permanent magnet 20 are located at the same height; one end of the height indicating needle 23 extends out of the side plate 4 from the display hole 9 and is used for displaying the real-time position of the permanent magnet 20, so that the position of the balance point of the quasi-zero stiffness vibration isolator can be conveniently adjusted.
In this embodiment, the support plate 31 is an L-shaped support plate, the top of the vertical section 31.1 of the support plate 31 is connected with the upper support platform 5 (which can be connected by a bolt C13), and the horizontal section of the support plate 31 is provided with the permanent magnet 20; the connecting plate 32 is connected to the vertical section of the support plate 31.
Preferably, the negative stiffness generating module is further provided with limiting rubbers 25, and the limiting rubbers 25 are arranged at the upper and lower ends of the support structure 18 of the anti-overturning mechanism (particularly, at the upper and lower portions of the first fixing block 18.1) to prevent the permanent magnet 20 from colliding with the C-shaped yoke 19 during the movement. In this embodiment, the connecting plate 32, the support plate 31 and the height indicating needle 23 are all reciprocated up and down along with the permanent magnet 20, and the connecting plate 32 is moved between the upper and lower portions of the first fixing block 18.1.
Preferably, the coil A21 is a water-cooling coil, which can effectively solve the problem of heat generation of the coil A21.
And the positive stiffness spring adjusting device 11 is used for realizing the control of the positive stiffness of the zero-stiffness vibration isolator. As shown in fig. 6, the worm gear and worm mechanism 25 includes a plurality of supports 28, a worm 26 and a worm wheel, wherein the plurality of supports 28 are arranged on the lower supporting platform 1 at intervals (can be connected by bolts); the worm 26 sequentially passes through each support 28 and then extends out of an operation hole on the side plate 4; the worm 26 is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt 24, and the bottom of the vertical bolt 24 is connected with the lower supporting platform 1; coil spring 27 and the coaxial cooperation of turbine, and the upper end of coil spring 27 and the interior top contact of last supporting platform 5, the lower extreme of coil spring 27 is fixed on the turbine, and when rotating worm 26, the turbine rotates thereupon to drive coil spring 27 and go up and down along the axis direction of vertical bolt 24, change coil spring 27's positive rigidity value, thereby be convenient for adjust the balance point position of accurate zero rigidity isolator. In this embodiment, there are 3 supports 28, which can fix the position of the worm 26 to effectively control the vertical movement of the coil spring 27.
Preferably, the positive stiffness spring adjusting device 11 is further provided with two sets of limiting mechanisms symmetrically distributed on the outer side of the coil spring 27 to limit the coil spring 27 to shift left and right and move only in the vertical direction; the limiting mechanism comprises a limiting rod 29 and a limiting block 30, the limiting rod 29 is vertically arranged, and the lower end of the limiting rod is connected with the lower supporting platform 1; the limiting block 30 is fixed on the limiting rod 29.
Preferably, as shown in fig. 7, the vertical eddy current damping module comprises an electromagnet B35 and a copper plate 34 which are arranged in parallel and at intervals, wherein the electromagnet B35 is composed of an outer yoke wound with a coil B, and the outer yoke is fixed on the lower support platform 1; the copper plate 34 is fixed on the connecting plate 32 and can move up and down along with the connecting plate 32 to cut the magnetic induction line of the electromagnet B35, so that eddy current damping is generated, and input current can be controlled to change the eddy current damping. In the embodiment, the electromagnet B35 is arranged in parallel with the copper plate 34, and the gap between the electromagnet B35 and the copper plate is 1 mm; and the coil B is a water-cooling coil.
In the invention, the C-shaped yoke 19, the middle yoke 33 and the outer yoke are all made of DT4C material with low coercive force and high magnetic permeability, and the permanent magnet 20 is made of rare earth permanent magnet material; other parts and structures are made of non-magnetic or weak magnetic materials, such as 304 stainless steel.
The working principle of the negative stiffness electromagnetic adjusting device 10 is as follows: the middle permanent magnet 20 magnetizes the upper and lower intermediate yokes 33, thereby generating an attractive force. The magnitude and direction of the current of the coil A21 are changed, so that the magnitude and direction of the magnetic field inside the intermediate yoke 33 are changed, and the magnitude of the electromagnetic negative stiffness is changed. The force applied to the intermediate yoke 33 can be divided into the acting force between the permanent magnet 20 and the permanent magnet 33 (permanent magnetic acting force) and the acting force between the magnetic field caused by the current of the coil a21 and the permanent magnet 20 (electromagnetic acting force), wherein the permanent magnetic acting force is:
Figure BDA0003404128540000071
in the formula, FpcRepresents the permanent magnet force, N; a is1Denotes constant coefficient, Nm4；q1Representing a displacement parameter (q)1＝zc+a2)，m；zcRepresents the distance, mm, of the permanent magnet 20 from the intermediate yoke 33 when the permanent magnet 20 is in the intermediate equilibrium position; a is2Represents the constant coefficient of displacement, m; z represents the vertical displacement, mm, of the permanent magnet 20 from the equilibrium position.
The electromagnetic force is:
Figure BDA0003404128540000072
in the formula, FpeRepresents the electromagnetic force, N; a is3Denotes the current parameter, A-1(ii) a sign represents a sign function; i represents coil a21 current, a; b3Denotes the current parameter, A-1；b1Denotes constant coefficient, Nm4；q2Representing a displacement parameter (q)2＝zc+b2)，m；b2Representing the constant coefficient of displacement, m.
The magnetization directions of the permanent magnet 20 and the electromagnet a are the same, and the structure is similar to a three-magnet negative-stiffness structure. When no current is applied to coil a21, the magnetic flux density is low, and is mainly generated by permanent magnet 20. As the magnitude of the current increases, the magnetic flux density also increases. When no current is supplied to the coil a21, a three-magnet negative stiffness structure can be formed due to the magnetic field induced by the permanent magnet 20 in the electromagnet a, so that a negative stiffness phenomenon exists, and the negative stiffness phenomenon is more obvious along with the increase of the current.
The working principle of the vertical eddy current damping device 36 is as follows: when current is input into the coil B, the electromagnet B35 composed of the outside yoke and the coil B generates a corresponding electromagnetic field around the copper plate 34, and the copper plate 34 can cut the magnetic induction line of the electromagnet B35 to generate eddy current damping in the up-and-down motion process along with the upper supporting platform, and the eddy current damping can be controlled by the input current.
Assuming a negligible surface charge of copper plate 34, the induced current density J on copper plate 34 can be expressed as:
J＝σ(v×B) (3)，
wherein σ is the electrical conductivity of the copper plate 34, Siemens/mm (S)In mm); v is the moving speed of the copper plate 34, mm/s; b represents the magnetic flux density generated by the electromagnet near the copper plate 34, Wb/mm2. Further, v and B may be written in the form of coordinate components:
v＝vxi+vyj+vzk (4)，
B＝Bxi+Byj+Bzk (5)，
in the formula, vx、vyAnd vzRespectively represents the components of the speed of the copper plate 34 on three coordinate axes, mm/s; b isx、ByAnd BzRespectively representing the components of the magnetic flux density on three coordinate axes, Wb/mm2(ii) a i. j and k represent unit vectors of three coordinate axes (x, y, and z), respectively, as shown in fig. 9. Depending on the actual operation, the copper plate 34 of the eddy current unit has only a velocity in the z-direction, so the induced current density can be further simplified as:
J＝σvz(-Byi+Bxj) (6)。
the Lorentz force F experienced by the eddy currents generated by the movement of the copper plate 34 in the magnetic flux density generated by the electromagnet can be expressed as:
F＝∫VJ×BdV (7)，
wherein V represents the volume of the copper plate 34 mm3Write component form:
Figure BDA0003404128540000081
therefore, the damping force F in the z directionzCan be expressed as:
Figure BDA0003404128540000082
the working principle of the invention is as follows: the invention provides negative rigidity by utilizing a vertical homopolar arrangement structure of three magnets, wherein a permanent magnet 20 is arranged in the middle, an electromagnet A is arranged at the upper part and the lower part, and a C-shaped yoke 19 is used for closing a magnetic loop; with the parallel connection of the coil springs 27, the overall stiffness of the system in the equilibrium position is small. When the vibration isolator is used, a vibration-isolated object is fixed at the center of the upper part of the upper supporting platform 5, and when the mass of the vibration-isolated object changes, the current of the coil A21 and the worm 26 are adjusted to enable the negative stiffness to be matched with the positive stiffness, so that the vibration isolator can be in a balanced position. Therefore, the whole device has small dynamic stiffness and low natural frequency during vibration. When the system is in a moving state, the copper plate 34 reciprocates together with the permanent magnet 10, the copper plate 34 cuts magnetic induction lines around the electromagnet B35, induced current is generated in the copper plate 34, and lorentz force is generated in the magnetic field of the electromagnet B35, so that eddy current damping (shown as a damping force curve of a vertical eddy current damping module in fig. 8) is formed, and the system is inhibited from resonating. When the whole device is in a static state, the permanent magnet 20 is positioned between the two middle yokes 33, and due to symmetry, the axial force generated by the electromagnet A on the permanent magnet 20 is zero, so that the static bearing capacity of the vibration isolator cannot be influenced.
Details not described in this specification are within the skill of the art that are well known to those skilled in the art. The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. A quasi-zero stiffness vibration isolator capable of adjusting electromagnetic negative stiffness and vertical eddy current damping is characterized by comprising a vibration isolation box body, and an anti-overturning device, a negative stiffness electromagnetic adjusting device, a positive stiffness spring adjusting device and a vertical eddy current damping device which are arranged in the vibration isolation box body; the vibration isolation box body comprises a lower supporting platform, an upper supporting platform and four side plates enclosed between the upper and lower supporting platforms; the anti-overturning device comprises four anti-overturning mechanisms which are sequentially arranged end to end, and the top and the bottom of each anti-overturning mechanism are respectively connected and fixed with the upper supporting platform and the lower supporting platform; the four anti-overturning mechanisms are symmetrically arranged along a diagonal line, and the middle parts of the four anti-overturning mechanisms surround to form a central area; the negative stiffness electromagnetic adjusting device comprises two negative stiffness generating modules which are oppositely arranged, and the negative stiffness generating modules face the central area; the positive stiffness spring adjusting device is arranged in the central area and comprises a worm and gear mechanism and a spiral spring, the worm and gear mechanism is arranged on the lower supporting platform, the input end of the worm and gear mechanism penetrates through the side plate to extend out of the vibration isolation box body, the output end of the worm and gear mechanism is connected with the spiral spring, the spiral spring is vertically arranged, and the worm and gear mechanism can drive the spiral spring to move along the vertical direction; the vertical eddy current damping device comprises two vertical eddy current damping modules which are oppositely arranged and are positioned outside a central area between the two negative stiffness generating modules, and the vertical eddy current damping modules are connected with the negative stiffness generating modules.
2. The quasi-zero stiffness vibration isolator of claim 1 wherein each negative stiffness generating module comprises a C-yoke and a permanent magnet, the bottom and top of the C-yoke being connected to the upper and lower support platforms, respectively; the open sides of the C-shaped yokes of the two negative stiffness generating modules are opposite; an upper middle yoke and a lower middle yoke are arranged in the opening of the C-shaped yoke, and a coil A is wound outside the two middle yokes to form an electromagnet A; the permanent magnet and the two electromagnets A are vertically arranged in the opening of the C-shaped yoke in the same polar direction, the permanent magnet is positioned between the two electromagnets A, and the three electromagnets form a closed magnetic loop in the C-shaped yoke; the permanent magnet is connected with the upper supporting platform through the supporting plate.
3. The quasi-zero stiffness vibration isolator according to claim 2, wherein the support plates of the two negative stiffness generating modules are connected through a connecting plate, and a height indicator pin is arranged on the connecting plate and is positioned at the same height as the permanent magnet; one end of the height indicating needle extends out of the side plate.
4. The quasi-zero stiffness vibration isolator of claim 3 wherein the support plate is an L-shaped support plate, the top of the vertical section of the support plate is connected with the upper support platform, and the horizontal section of the support plate is provided with permanent magnets; the connecting plate is connected with the vertical section of the supporting plate.
5. The quasi-zero stiffness vibration isolator according to claim 2, wherein the negative stiffness generating module is further provided with limiting rubbers disposed at upper and lower ends of the support structure of the anti-overturning mechanism.
6. The quasi-zero stiffness vibration isolator of claim 3 wherein the vertical eddy current damping module comprises an electromagnet B and a copper plate arranged in parallel and spaced apart, the electromagnet B being formed by an outer yoke wound with a coil B; the copper plate is fixed on the connecting plate and can move up and down along with the connecting plate to cut the magnetic induction line of the electromagnet B.
7. The quasi-zero stiffness vibration isolator of claim 1 wherein each anti-overturning mechanism is provided with a support structure comprising a first fixed block, a second fixed block, a third fixed block connected with a lower support platform, a fourth fixed block connected with an upper support platform, and a plurality of transverse springs and a plurality of vertical springs; the second fixed block is arranged at the upper part of the first fixed block and is connected with the third fixed block through at least one transverse reed; the third fixed block is connected with the fourth fixed block through at least one vertical reed.
8. The quasi-zero stiffness vibration isolator of claim 1 wherein the worm gear and worm mechanism includes a plurality of standoffs, a worm, and a worm gear, the plurality of standoffs being spaced apart on the lower support platform; the worm sequentially penetrates through the supports and then extends out of the operation hole in the side plate; the worm is matched with the worm wheel, the middle part of the worm wheel is in threaded fit with the vertical bolt, and the bottom of the vertical bolt is connected with the lower supporting platform; the spiral spring is coaxially matched with the turbine, the upper end of the spiral spring is in contact with the inner top of the upper supporting platform, the lower end of the spiral spring is fixed on the turbine, and when the worm is rotated, the turbine rotates along with the spiral spring and drives the spiral spring to lift along the axis direction of the vertical bolt.
9. The quasi-zero stiffness vibration isolator according to claim 8, wherein the positive stiffness spring adjusting device is further provided with two sets of limiting mechanisms symmetrically distributed on the outer sides of the spiral springs, each limiting mechanism comprises a limiting rod and a limiting block, the limiting rods are vertically arranged, and the lower ends of the limiting rods are connected with the lower supporting platform; the limiting block is fixed on the limiting rod.
10. The quasi-zero stiffness vibration isolator of claim 3 wherein the C-shaped yoke and the intermediate yoke are made of DT4C material and the permanent magnets are made of rare earth permanent magnet material.
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