CN115823179A - Low-frequency vibration isolation device based on linear magnetic negative stiffness - Google Patents
Low-frequency vibration isolation device based on linear magnetic negative stiffness Download PDFInfo
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Abstract
The invention discloses a low-frequency vibration isolation device based on linear magnetic negative stiffness, which comprises two spring positive stiffness modules, an electromagnetic negative stiffness module and a central shaft; the two spring positive stiffness modules are respectively and symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module; the upper end of the central shaft is connected with a load, and the lower end of the central shaft sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module. The invention has the beneficial effects that: the invention has high bearing capacity and low-frequency vibration isolation performance, realizes mutual offset of nonlinear parts of softening rigidity characteristic and hardening rigidity characteristic by adopting a coupling mode of the attraction type electromagnetic negative rigidity mechanism and the repulsion type electromagnetic negative rigidity mechanism, and improves the linearity of the negative rigidity in the high-static low-dynamic rigidity vibration isolation device.
Description
Technical Field
The invention relates to the technical field of vibration isolation, in particular to a low-frequency vibration isolation device based on linear magnetic negative stiffness.
Background
The power equipment on the ship generates low-frequency vibration during working, and is always a main factor threatening the concealment of the ship due to high transmissibility and low attenuation; meanwhile, due to the particularity of the working environment of the ship equipment, the vibration isolation system is required to have certain rigidity characteristics of high static and low dynamic. Therefore, constructing a suitable vibration damping system to improve the concealment and survival rate of ships is a main aspect of current underwater vibration damping research.
The passive vibration isolation device still has wide engineering application space due to simple structure, high reliability and no external energy. The traditional linear rigidity vibration isolation device has good isolation effect on medium and high frequency vibration, but has unsatisfactory isolation effect on low frequency vibration. In recent years, in order to break through the performance bottleneck of a linear vibration isolation system, researchers provide a negative stiffness mechanism, and the high static stiffness and low dynamic stiffness vibration isolation system with stiffness changing along with the compression amount is realized. The negative stiffness mechanism and the positive stiffness system are connected in parallel at the balance position, so that the positive stiffness near the balance position of the system can be counteracted, lower dynamic stiffness is achieved, and the bearing static stiffness and the static displacement of a load when the system is in zero compression are not influenced, so that the inherent frequency of the system is reduced while the bearing capacity of the system is not reduced, and the vibration isolation frequency band is expanded.
The negative stiffness device is a key structure for realizing high static stiffness and low dynamic stiffness vibration isolation. To date, researchers have used a variety of approaches to achieve negative stiffness, typical of which are: mechanical springs, magnets, rubber, cams, biomimetic structures, and the like. For example, utility model patents cn202021960720.x, CN201821473137.9, CN201822217954.4, inventive patents CN201610423635.1, CN201510788865.3, etc. However, all of these methods have a problem: non-linear stiffness characteristics, which may lead to possible "jumping" of the motion of the system. According to a dynamic model of the vibration isolation system, the nonlinear stiffness can generate unexpected response under large excitation, the vibration isolation performance is deteriorated, and the application of the high static stiffness and low dynamic stiffness vibration isolation system in large amplitude vibration isolation is limited.
Disclosure of Invention
The invention aims to provide a low-frequency vibration isolation device based on linear magnetic negative stiffness, aiming at the defects of the prior art.
The technical scheme adopted by the invention is as follows: a low-frequency vibration isolation device based on linear magnetic negative stiffness comprises two spring positive stiffness modules, an electromagnetic negative stiffness module and a central shaft; the two spring positive stiffness modules are respectively and symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module; the upper end of the central shaft is connected with a load, and the lower end of the central shaft sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module which are positioned at the upper part;
the electromagnetic negative stiffness module comprises an upper annular permanent magnet, a middle annular permanent magnet and a lower annular permanent magnet which are sequentially arranged along the axial direction of a central shaft, and the upper annular permanent magnet and the lower annular permanent magnet are symmetrically arranged at the upper part and the lower part of the middle annular permanent magnet; coaxial annular coils are correspondingly arranged outside each permanent magnet, and the annular coils are fixed with corresponding annular coil boxes; the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft;
the axial displacement of the central shaft can be adjusted through the two spring positive stiffness modules, so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
According to the scheme, the spring positive stiffness module comprises a spiral spring, a limiting piece and an adjusting piece; the spiral spring is sleeved on the central shaft, one end of the spiral spring is connected with the adjusting piece, and the adjusting piece is matched with the central shaft; the other end of the spiral spring is connected with the upper end face of the limiting piece; the central shaft penetrates through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spiral spring positive stiffness modules; when the adjusting pieces of the two spring positive stiffness modules are adjusted, the compression amounts of the two spiral springs can be changed, and further the axial position of the central shaft is changed, so that the relative positions of the annular permanent magnet and the corresponding coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
According to the scheme, the limiting pieces are linear bearings, and the linear bearings of the two spring positive stiffness modules are symmetrically arranged on the central shaft along the balance position of the vibration isolation device; one end of the spiral spring is connected with the end face of the linear bearing, and the linear bearing is connected with the annular coil box body through a plurality of axially spaced through bolts.
According to the scheme, the three annular lines are vertically and coaxially and symmetrically arranged to form the attraction type electromagnetic negative stiffness mechanism; the upper and lower two annular coils are respectively and symmetrically arranged at two ends of the middle annular coil, and are introduced with currents with the same direction and magnitude.
According to the scheme, the annular coils are water-cooling coils.
According to the scheme, the three annular permanent magnets and the three annular coils are vertically, coaxially and symmetrically arranged to form the repelling electromagnetic negative stiffness mechanism; the annular permanent magnets are fixedly connected with the central shaft through fixing rings, and the three annular coils are coaxial with the corresponding annular permanent magnets in equal height.
According to the scheme, the annular permanent magnets are axially magnetized.
According to the scheme, the vertical distance between the annular coils is 14-15 mm, the vertical distance between the annular permanent magnets is 14-15 mm, and the transverse distance between the annular coils and the corresponding permanent magnets is 4-5 mm.
According to the scheme, the screw pitch of the adjusting nut of the upper spring positive stiffness module is smaller than that of the adjusting nut of the lower spring positive stiffness module.
According to the scheme, the linear bearing adopts a sliding bearing with an aluminum shell and a tetrafluoroethylene resin lining; the annular permanent magnet is made of rare earth permanent magnet material; the central shaft, the bolt and the nut are made of non-magnetic conductive or weak magnetic conductive materials; each box body is made of aluminum alloy materials.
The invention has the beneficial effects that: the invention adopts a coupling mode of the attraction type electromagnetic negative stiffness mechanism and the repulsion type electromagnetic negative stiffness mechanism to realize mutual offset of nonlinear parts of softening stiffness characteristic and hardening stiffness characteristic, improves the linearity of the negative stiffness in the low-frequency vibration isolation device, ensures that the system has high bearing capacity and low-frequency vibration isolation performance, solves the problems of 'jumping' and 'unexpected response under large excitation', and further improves the working stability of the vibration isolation system. The invention adopts the coarse adjusting nut, the fine adjusting nut and the electromagnetic negative stiffness structure, can control the current in the electromagnet in real time according to the change of the load mass, and adjust the negative stiffness in real time, ensures that the vibration isolation frequency of the vibration isolation system at the balance position is in a quasi-zero state, improves the performance stability of the vibration isolation system, and enhances the low-frequency or ultralow-frequency vibration isolation effect of the vibration isolation system. The invention has very low dynamic stiffness near the static equilibrium position; by coupling the attraction type electromagnetic negative stiffness mechanism and the repulsion type electromagnetic negative stiffness mechanism, the stability of the vibration isolation system is improved, the vibration isolation system has good anti-swing performance, is simple in structure and convenient to maintain, and is suitable for low-frequency or 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 front sectional view of the entire structure of the present embodiment.
Fig. 3 is a side sectional view of the internal structure of the present embodiment.
Fig. 4 is a schematic connection diagram of the linear bearing device, the attraction type electromagnetic negative stiffness adjusting device, the repulsion type electromagnetic negative stiffness adjusting device, and the positive stiffness spring adjusting device in this embodiment.
Wherein: 1. a load; 2. a coil spring; 3. an upper loop coil; 4. a middle loop coil; 5. a lower end annular coil; 6. a base; 7. locking the nut; 8. fine adjustment of the nut; 9. an upper linear bearing; 10. a fixing ring; 11. a vibration isolation device case; 12. a lower linear bearing; 13. coarse adjustment of the nut; 14. a central shaft; 15. a through bolt; 16. an upper annular permanent magnet; 17. a lower annular permanent magnet; 18. a middle annular permanent magnet; 19. a middle annular coil box body; 20. an upper linear spring housing; 21. a lower annular coil box body; 22. a lower annular coil box body; 23. and an upper annular coil box body.
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.
As shown in fig. 1 to 4, the low-frequency vibration isolation device based on linear magnetic negative stiffness comprises two spring positive stiffness modules, an electromagnetic negative stiffness module and a central shaft 14; the two spring positive stiffness modules are respectively and symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module; the upper end of the central shaft 14 is connected with the load 1 (the upper end of the central shaft 14 is matched with the locking nut 7, and the locking nut 7 is connected with the bottom of the load 1), and the lower end of the central shaft 14 sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module which are positioned at the upper part;
the electromagnetic negative stiffness module comprises an upper annular permanent magnet 16, a middle annular permanent magnet 18 and a lower annular permanent magnet 17 which are sequentially arranged along the axial direction of a central shaft 14, wherein the upper annular permanent magnet and the lower annular permanent magnet are symmetrically arranged at the upper part and the lower part of the middle annular permanent magnet 18; coaxial annular coils (an upper annular coil 3, a middle annular coil 4 and a lower annular coil 5 are respectively and correspondingly arranged outside each annular permanent magnet), and the annular coils are fixed with corresponding annular coil boxes (each annular coil respectively corresponds to an upper annular coil box 23, a middle annular coil box 19 and a lower annular coil box 21); the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft 14;
the axial displacement of the central shaft 14 can be adjusted through the two spring positive stiffness modules (the load 1 moves synchronously along with the central shaft 14), so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
Preferably, the positive spring stiffness module comprises a coil spring 2, a limiting member and an adjusting member; the spiral spring 2 is sleeved on the central shaft 14, one end of the spiral spring 2 is connected with the adjusting piece, and the adjusting piece is matched with the central shaft 14; the other end of the spiral spring 2 is connected with the upper end face of the limiting piece; the central shaft 14 passes through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spring positive stiffness modules; when adjusting the adjusting parts of the two spring positive stiffness modules, the compression amount of the two spiral springs 2 can be changed, and further the axial position of the central shaft 14 is changed, so that the relative positions of the annular permanent magnet and the corresponding annular coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
In the invention, a load 1 is arranged on a locking nut 7, the upper end of a central shaft 14 is matched with the locking nut 7, and the load 1 can axially move along with the central shaft 14; a notch for axial movement of the central shaft 14 is reserved in the base 6.
Preferably, the adjusting member is an adjusting nut. The spiral spring is a linear spiral spring 2, and the outer peripheral surface of the central shaft 14 is provided with an external thread matched with the adjusting nut. Specifically, the adjusting nut of the upper spring positive stiffness module is a fine adjusting nut 8, the adjusting nut of the lower spring positive stiffness module is a coarse adjusting nut 13, the thread pitches of the two nuts are different, and the thread pitch of the coarse adjusting nut 13 is larger than that of the fine adjusting nut 8. The coarse adjustment nut 13 can be used for large position adjustment, the fine adjustment nut 8 can be used for fine adjustment, the structural design is simple, but both coarse adjustment and fine adjustment are achieved, and the operation is convenient.
Preferably, the limiting member is a linear bearing, and the linear bearings (the upper portion is an upper linear bearing 9, and the lower portion is a lower linear bearing 12) of the two spring positive stiffness modules are symmetrically arranged on the central shaft 14 along the balance position of the vibration isolation device (the central shaft 14 is matched with the inner ring of the linear bearing); one end of the spiral spring 2 is connected with the end face of the linear bearing, and the linear bearing is respectively connected with the annular coil box body through a plurality of through bolts 15 which are axially arranged at intervals. Specifically, an upper linear bearing 9 of the upper spring positive stiffness module is in bolted connection with an upper annular coil box body 23, and a lower linear bearing 11 of the lower spring positive stiffness module is in bolted connection with a lower annular coil box body 21; two linear bearings are arranged on the outer sides of the upper annular coil and the lower annular coil, so that the coaxiality of the box body and the central shaft 14 can be ensured, and the friction during movement is reduced. The upper surfaces of the two linear bearings are provided with spring notches, so that the position of the spiral spring 2 can be effectively limited.
In the present invention, three ring-shaped permanent magnets are mounted on a central shaft 14 through a fixing ring 10. The upper annular permanent magnet 16 is correspondingly provided with an upper annular coil 3 and an upper annular coil box body 23, the middle annular permanent magnet 18 is correspondingly provided with a middle annular coil 4 and a middle annular coil box body 19, and the lower annular permanent magnet 17 is correspondingly provided with a lower annular coil 5 and a lower annular coil box body 21; baffle rings are arranged in the three annular coil boxes 19, 20 and 21 and used for fixing the corresponding annular coils. The vibration isolation box body 11 comprises a spring box body at the top (such as a top spring box body 20 in fig. 1-4), three ring-shaped coil box bodies at the middle (such as an upper ring-shaped coil box body 23, a middle ring-shaped coil box body 19 and a lower ring-shaped coil box body 21 in the drawings) and a spring box body at the bottom (reference numeral 22), and all the box bodies are fixedly connected through external bolts. The spring box body 22 at the bottom is also the base box body of the whole vibration isolation device, and the base 6 is provided with bolt holes which can be used for fixed connection; a coarse adjustment nut 13 of the lower spring positive stiffness module is mounted on the base 6.
In the invention, the linear bearing adopts a sliding bearing with an aluminum shell and a tetrafluoroethylene resin lining so as to avoid the influence of a common steel ball linear bearing on a magnetic field; the annular permanent magnets are all made of rare earth permanent magnet materials; the central shaft 14, the fixing ring 10, the bolt and the nut and other parts and structures are made of non-magnetic conductivity or weak magnetic conductivity materials, such as 304 stainless steel; each box body is made of aluminum alloy materials.
In the invention, the components of the electromagnetic negative stiffness module can respectively form an attraction type electromagnetic negative stiffness mechanism and a repulsion type electromagnetic negative stiffness mechanism.
The three annular coils 3, 4 and 5 are vertically and coaxially and symmetrically arranged to form the attraction type electromagnetic negative stiffness mechanism. As shown in fig. 3 and 4, the attraction type electromagnetic negative stiffness mechanism includes two symmetrically arranged upper and lower annular coils 3 and 5 and a middle annular coil 4, and each annular coil is formed by winding an enameled wire. The two upper and lower identical toroidal coils 3 and 5 are respectively positioned at two ends of the middle toroidal coil 4 along the central axis 14, are symmetrically arranged, and are introduced with currents with the same direction and the same magnitude. The three annular coils are fixed with each other; the annular coils are water-cooling coils, so that the heating problem of the coils can be effectively solved.
The three annular permanent magnets 16, 17 and 18 and the three annular coils 3, 4 and 5 are vertically, coaxially and symmetrically arranged to form the repelling electromagnetic negative stiffness mechanism. As shown in fig. 3 and 4, the repulsive electromagnetic negative stiffness mechanism includes three pairs of paired structures (an upper annular coil 3 and an upper end annular permanent magnet 16, a middle annular coil 4 and a middle annular permanent magnet 18, a lower annular coil 5 and a lower end annular permanent magnet 17) composed of annular coils and permanent magnets, and the paired structures of the three pairs of annular coils and the permanent magnets are symmetrically arranged along a central axis 14. Preferably, the annular permanent magnets in the three pairs of paired structures are fixedly connected with the central shaft 14 through the fixing ring 10, and the three annular coils 3, 4 and 5 are mutually fixed and are coaxial with the corresponding annular permanent magnets 16, 17 and 18 in equal height. The vertical distance of the pairing structure formed by the three pairs of annular coils and the corresponding permanent magnets is 14-15 mm (namely the vertical distance between the annular coils is 14-15 mm, the vertical distance between the annular permanent magnets is 14-15 mm), and the transverse distance between the annular coils and the corresponding annular permanent magnets is 4-5 mm. The annular permanent magnets in the three pairs of paired structures are axially magnetized, and only axial force acts on the annular permanent magnets, namely, only axial negative stiffness is generated, which is known from two-dimensional axial symmetry of the annular permanent magnets and the annular coils.
The two spring positive stiffness adjusting mechanisms respectively adopt linear spiral springs 2. As shown in fig. 3 and 4, the two linear coil springs 2 are sleeved on the central shaft 14 and located outside the two linear bearings 9 and 12. One end of the linear spring 2 is pressed against the notches of the linear bearings 9, 12, and the other end is pressed against the coarse adjustment nut 13 or the fine adjustment nut 8 of the central shaft 14, respectively. The design that the two spiral springs 2 compress the middle electromagnetic negative stiffness module can ensure that the load cannot be separated from the springs when the vibration isolation system generates large displacement due to resonance.
The equilibrium position refers to a position in which the system is at rest. The balance position in the invention is the position of the middle annular permanent magnet at the vertical center of the middle annular coil. According to the electromagnetic negative stiffness generation mechanism of the magnetic element configuration, the attractive electromagnetic negative stiffness mechanism generates softening negative stiffness, because the attractive force between the magnets is inversely proportional to the square of the distance, and the farther away from the equilibrium position, the closer to one end of the magnet, the larger the generated force difference. The repulsive electromagnetic negative stiffness mechanism produces a stiff negative stiffness because the more out of balance the repulsive force between the magnetic elements is smaller. Therefore, the repulsion type electromagnetic negative stiffness mechanism and the attraction type electromagnetic negative stiffness mechanism are coupled, the nonlinear parts of the softening stiffness characteristic and the hardening stiffness characteristic are mutually offset, the linear parts are mutually superposed, and the negative stiffness linearity is improved while the negative stiffness value is improved. The use of permanent magnets or toroidal coils can produce negative stiffness of either softening or hardening characteristics, with the negative stiffness produced between the permanent magnets being greater but not adjustable; the size of the magnetic field can be controlled by controlling the exciting current of the annular coil, but the current carrying capacity is limited, and the negative rigidity generated by the electromagnetic force between the annular coils is too weak; therefore, the electromagnetic negative stiffness module is designed by selecting the combination configuration of the annular coil and the annular permanent magnet, so that the adjustable negative stiffness is realized, and a larger adjustable range is obtained.
In the invention, the repelling electromagnetic negative stiffness mechanism comprises three annular permanent magnets 16, 17 and 18 and three annular coils 3, 4 and 5. When current is introduced into the annular coil, the current-carrying ring excites a constant magnetic field due to the magnetic effect of the current and generates interaction force with the annular permanent magnet. The magnetic field distribution generated by magnetic elements such as permanent magnets and coils in vacuum is relatively regular, and the electromagnetic field generated by the magnetic elements can be calculated so as to calculate the electromagnetic force.
According to the superposition theorem, the axially magnetized annular permanent magnet can be equivalent to a reversely magnetized cylindrical permanent magnet superposed in a cylindrical permanent magnet. The axially magnetized ring magnet can be equivalent to two thin solenoids positioned on the inner and outer annular surfaces, the current in the two solenoids is equal in magnitude and opposite in direction, and the currents are respectively as follows:
in the formula, mu 0 Is magnetic permeability (H/m) in vacuum, inner I in Is the internal equivalent solenoid current value (A), I out Is the external equivalent solenoid current value (A), h is the equivalent solenoid axial height (m), N eq Is the equivalent number of turns (turns) of the equivalent solenoid, and J is the equivalent polarization (C/m) 2 )。
In the invention, the attraction type electromagnetic negative stiffness mechanism adopts three annular coils 3, 4 and 5, wherein two identical annular coils are introduced with currents with the same direction and the same magnitude. When current is applied to the toroidal coil, the two current-carrying rings 1 and 2 will respectively excite a constant magnetic field and generate an interaction force due to the magnetic effect of the current.
The biot-savart law describes the magnetic field excited by the current element at any point in space:
wherein I is a source current (A), dl is a minute line element (m) of the source current, r is a distance (m) from a current element to an excitation magnetic field point, and e r Is a unit vector (A.m) of current element pointing to the excitation magnetic field point, B is magnetic induction intensity (T), mu 0 Is the magnetic permeability (H/m) in vacuum.
The acting force of the current element Idl on the current carrying ring from the other current carrying ring is as follows:
dF＝Idl×B (4)，
the interaction force F between the two current-carrying rings can be obtained by integrating the formula:
F＝∫ l dF (5)，
since the two current-carrying rings are concentric, the electromagnetic force is known to be axial based on symmetry. Because the integral is complex, the analytic solution is difficult to solve, and the elliptic integral is also used for expression, so that:
in the formula I 1 Is the current value (A), I of the current-carrying ring 1 2 Is the current value (A), r of the current-carrying ring 2 1 Is the radius (m), r of the current-carrying ring 1 2 Radius (m) of the current-carrying ring 2, z is the vertical distance (m) between two current-carrying rings, and k is
K (K) and E (K) are full elliptic integrals of the first and second classes, respectively, with K as the modulus. The direction of the interaction force between the two current carrying rings is determined by the direction of the exciting current, and according to the ampere rule, when the current directions in the two current carrying rings are the same, the electromagnetic force is shown as mutual attraction, otherwise, the electromagnetic force is mutually exclusive. To this end, the electromagnetic force between the two current carrying rings has been determined, and the superposition of the forces between the current carrying rings, i.e. the electromagnetic force between the energized coils or solenoids, can be solved. And the electromagnetic force between the annular coil and the annular permanent magnet can be obtained by combining the equivalent relation between the axial magnetizing permanent magnet and the solenoid.
The working principle of the invention is as follows: by adopting a coupling mode of the attraction type electromagnetic negative stiffness mechanism and the repulsion type electromagnetic negative stiffness mechanism, the mutual offset of nonlinear parts of the softening stiffness characteristic and the hardening stiffness characteristic is realized, and the linearity of the negative stiffness in the low-frequency vibration isolation device is improved. The attraction type electromagnetic negative stiffness mechanism comprises three annular coils 3, 4 and 5, wherein currents in the same direction are introduced into the annular coils 3 and 5 at the head end and the tail end, and mutual attraction acting force is generated among the three; the repulsion type electromagnetic negative stiffness mechanism adopts three annular permanent magnets 16, 17 and 18 and three annular coils 3, 4 and 5, wherein the permanent magnets axially move in the annular coils, and mutual repulsion acting force is generated between the permanent magnets and the annular coils. When the system is in a static equilibrium position, the acting forces between the three ring-shaped permanent magnets 16, 17, 18 and the three ring-shaped coils 3, 4, 5 are mutually counteracted, and the system is in a stable state. When the system is subjected to external excitation force, the central shaft vertically moves, so that the annular permanent magnet deviates from a balance position, repulsive electromagnetic force is generated between the annular permanent magnet and the annular coils, and attractive electromagnetic force is also generated between the other three annular coils, so that negative rigidity is provided, and a nonlinear part can be effectively offset. Therefore, the dynamic frequency of the system is low, and vibration caused by exciting force can be effectively isolated. The electromagnetic force is in the same direction as the relative displacement, which causes it to move away from the equilibrium position, i.e. the designed electromagnetic coupling structure generates a negative stiffness. When the load mass changes, the coarse adjusting nut, the fine adjusting nut and the electromagnetic negative stiffness module can be adopted to control the current in the electromagnet in real time according to the change of the load mass and adjust the negative stiffness in real time, so that the vibration isolation frequency of the vibration isolation device at the balance position is guaranteed to be in a quasi-zero state. In addition, the current in the annular coil is reversed to generate positive rigidity, so that the adjustable range of the rigidity can be expanded, and the application range of the linear electromagnetic coupling structure is expanded.
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 low-frequency vibration isolation device based on linear magnetic negative stiffness is characterized by comprising two spring positive stiffness modules, an electromagnetic negative stiffness module and a central shaft; the two spring positive stiffness modules are respectively and symmetrically arranged at the upper part and the lower part of the electromagnetic negative stiffness module; the upper end of the central shaft is connected with a load, and the lower end of the central shaft sequentially penetrates through the spring positive stiffness module, the electromagnetic negative stiffness module and the spring positive stiffness module;
the electromagnetic negative stiffness module comprises an upper annular permanent magnet, a middle annular permanent magnet and a lower annular permanent magnet which are sequentially arranged along the axial direction of a central shaft, and the upper annular permanent magnet and the lower annular permanent magnet are symmetrically arranged at the upper part and the lower part of the middle annular permanent magnet; coaxial annular coils are correspondingly arranged outside each permanent magnet, and the annular coils are fixed with the corresponding annular coil boxes; the three annular permanent magnets can move along the axial direction in the cavity inside the corresponding annular coil along with the central shaft;
the axial displacement of the central shaft can be adjusted through the two spring positive stiffness modules, so that the relative positions of the annular permanent magnet and the corresponding coil are changed, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
2. The low frequency vibration isolation device of claim 1, wherein said spring positive stiffness module comprises a coil spring, a limiter and an adjuster; the spiral spring is sleeved on the central shaft, one end of the spiral spring is connected with the adjusting piece, and the adjusting piece is matched with the central shaft; the other end of the spiral spring is connected with the upper end face of the limiting piece; the central shaft penetrates through the center of the limiting piece; the electromagnetic negative stiffness module is arranged between the limiting parts of the two spiral spring positive stiffness modules; when the adjusting pieces of the two spring positive stiffness modules are adjusted, the compression amounts of the two spiral springs can be changed, and further the axial position of the central shaft is changed, so that the relative positions of the annular permanent magnet and the corresponding annular coil are adjusted, and the negative stiffness of the electromagnetic negative stiffness module is adjusted.
3. The low frequency vibration isolation device according to claim 2, wherein said limiter is a linear bearing, and the linear bearings of the two positive spring rate modules are symmetrically arranged on the central axis along the balance position of the vibration isolation device; one end of the spiral spring is connected with the end face of the linear bearing, and the linear bearing is connected with the annular coil box body.
4. The low frequency vibration isolation device of claim 2, wherein three toroidal lines are arranged vertically and concentrically symmetrically to form an attractive electromagnetic negative stiffness mechanism; the upper and lower two annular coils are respectively and symmetrically arranged at two ends of the middle annular coil, and are introduced with currents with the same direction and magnitude.
5. The low frequency vibration isolation mounting of claim 4, wherein said toroidal coils are all water-cooled coils.
6. The low frequency vibration isolation device according to claim 1, wherein three annular permanent magnets and three annular coils are vertically coaxially and symmetrically arranged to form a repulsive electromagnetic negative stiffness mechanism; the annular permanent magnets are fixedly connected with the central shaft through fixing rings, and the three annular coils are coaxial with the corresponding annular permanent magnets in equal height.
7. The low frequency vibration isolator as claimed in claim 2, wherein the linear bearing is a sliding bearing of an aluminum housing and a tetrafluoroethylene resin lining.
8. The low frequency vibration isolation device according to claim 6, wherein the vertical interval of the toroidal coil is 14 to 15mm, the vertical interval of the toroidal permanent magnet is 14 to 15mm, and the lateral interval of the toroidal coil and the corresponding permanent magnet is 4 to 5mm.
9. The low frequency vibration isolation device of claim 2, wherein the adjustment member is an adjustment nut, and a pitch of the adjustment nut of the upper positive spring rate module is smaller than a pitch of the adjustment nut of the lower positive spring rate module.
10. The low frequency vibration isolator of claim 8, wherein the linear bearing is a sliding bearing with an aluminum housing and a tetrafluoroethylene resin lining; the annular permanent magnet is made of rare earth permanent magnet material; the central shaft, the bolt and the nut are made of non-magnetic conductive or weak magnetic conductive materials; each box body is made of aluminum alloy materials.
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