Bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator

Abstract

The application discloses a bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator, and belongs to the technical field of vibration isolation. The bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator is characterized by comprising a stiffness bidirectional control positive stiffness unit, a negative stiffness unit and a base. The stiffness bidirectional control positive stiffness unit is composed of a sleeve, an iron core, a laminated steel sheet, a bidirectional control laminated magnetic sensitive unit, a support table, a bidirectional control shear magnetic sensitive unit and an excitation coil. The negative stiffness unit is composed of a plurality of bending elastic beams. The stiffness bidirectional control positive stiffness unit and the negative stiffness unit are connected by a load table and the base. The bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator can be bidirectionally adjusted in stiffness to adapt to the problem that the stiffness is only close to zero due to the mismatch of loads or the mismatch of stiffnesses of the positive and negative stiffness units. The bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator solves the problems that the positive and negative stiffness units of a passive quasi-zero stiffness vibration isolator are difficult to accurately match, the working interval of quasi-zero stiffness is narrow, the load quality is very sensitive, and the jumping phenomenon caused by strong nonlinearity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vibration reduction, in particular to a bidirectional magnetic control variable stiffness self-adaptive quasi-zero stiffness vibration isolator. BACKGROUND

[0002] In the process of ultra-precision machining, the vibration transmitted to the platform by the foundation is low frequency, wide band, micro amplitude and multi-source, and a vibration isolation system is usually used to isolate such vibration. According to the principle of vibration isolation, the effective isolation bandwidth of the vibration isolation system is higher than times the natural frequency. If a wider vibration isolation bandwidth is to be obtained, the stiffness of the vibration isolator must be reduced, which will inevitably reduce the carrying capacity of the system. In order to overcome the contradiction between high carrying capacity and low natural frequency of the traditional vibration isolation system, a kind of vibration isolation device with high static and low dynamic stiffness is invented. This kind of vibration isolator is generally composed of positive stiffness elements and negative stiffness elements in parallel, in the static state, the negative stiffness unit does not output force, the positive stiffness unit bears the load pressure, the system stiffness is provided by the positive stiffness, and the system shows high static stiffness; under dynamic load, the negative stiffness unit outputs a negative stiffness force in the same direction as the relative displacement of the system, and the positive stiffness unit outputs a positive stiffness force in the opposite direction of the relative displacement of the system, the positive and negative stiffness forces offset each other, and the quasi-zero stiffness vibration isolator shows low dynamic stiffness.

[0003] However, the errors in the manufacturing and assembly processes of the traditional vibration isolator will lead to the mismatch of the positive and negative stiffness units, and when the composite stiffness is less than zero, the system is unstable, and when the composite stiffness is greater than zero, the natural frequency of the system is greatly increased, and the low frequency vibration isolation effect is poor; in addition, the current quasi-zero stiffness vibration isolator generally uses passive elements with fixed parameters and characteristics, and once the design and manufacturing are completed, the working characteristics cannot be adjusted, and it cannot adapt to the changes of its own characteristic parameters, load mass and vibration excitation. Therefore, it is necessary to invent a quasi-zero stiffness vibration isolator with bidirectional stiffness regulation to solve the problem of structure stiffness matching.

[0004] Through retrieval, the quasi-zero stiffness vibration isolators based on magneto-rheological elastomers with application numbers 201811367717.4, 201811048587.8 and 202010170122.0 are designed. The features of these inventions are quasi-zero stiffness vibration isolators with positive and negative stiffness in parallel, which can increase the composite stiffness of the system by manually or electromagnetically adjusting the positive stiffness unit, but they do not have the function of negative stiffness regulation. They can only solve the problem of quasi-zero stiffness structure stiffness matching when the composite stiffness is less than zero, but cannot solve the problem when the composite stiffness is greater than zero.

[0005] In addition, for the traditional quasi-zero stiffness vibration isolator, the system stiffness is zero at the equilibrium position, and when the system deviates from the equilibrium position, the system stiffness increases rapidly, which has a nonlinear relationship proportional to the square of the displacement (such as Figure 2). The nonlinearity causes the following problems: 1. The quasi-zero stiffness working range is narrow, and a slight change in amplitude will cause the composite stiffness to rise sharply (such as Figure 2 ); 2. The amplitude-frequency response curve of the system jumps, causing the system to be unstable (such as Figure 3 ). The nonlinearity problem limits the further reduction of the vibration isolation frequency band. It is necessary to invent a quasi-zero stiffness vibration isolator with negative regulation of the stiffness that can track the nonlinear stiffness change in real time, so as to realize the real-time quasi-zero stiffness of the quasi-zero stiffness vibration isolation system and solve the nonlinear problem of the quasi-zero stiffness vibration isolator. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a quasi-zero stiffness vibration isolator based on a bidirectional variable stiffness structure that can adjust the system stiffness in real time, so that the system stiffness is quasi-zero in real time; to solve the stiffness matching and weaken the nonlinearity of the system stiffness of the traditional quasi-zero stiffness vibration isolator. Unlike the existing invention of a quasi-zero stiffness vibration isolator based on a magneto-rheological elastomer, the positive stiffness unit of the present application can be negatively regulated.

[0007] The technical scheme adopted by the present application is a bidirectional magnetic control variable stiffness adaptive quasi-zero stiffness vibration isolator. The adaptive quasi-zero stiffness vibration isolator with a bidirectional variable stiffness structure designs a stiffness bidirectional regulation positive stiffness unit based on a modulus bidirectional regulation magnetic sensitive unit, and is connected in parallel with a negative stiffness unit composed of a bending elastic beam. The stiffness bidirectional regulation positive stiffness unit is composed of a sleeve 1, an iron core 3, a laminated steel sheet 4, a bidirectional regulation laminated magnetic sensitive unit 5, a support table 6, a bidirectional regulation shear magnetic sensitive unit 9 and an excitation coil 10. The negative stiffness unit is composed of a plurality of bending elastic beams 8. The stiffness bidirectional regulation positive stiffness unit and the negative stiffness unit are connected by a worktable 7 and a base 2.

[0008] Further, the iron core 3 is tightly arranged in the center of the sleeve 1, the circular plate-shaped bidirectional regulation laminated magnetic sensitive unit 5 and the circular plate-shaped laminated steel sheet 4 are alternately bonded on the iron core 3, forming a laminated elastic unit, the T-shaped circular table-shaped support table 6 is bonded on the laminated elastic unit, a piece of annular bidirectional regulation shear magnetic sensitive unit 9 is bonded on the outer circular surface of the support table 6 and the inner circular surface of the sleeve 1, and the excitation coil 10 is wound around the iron core 3 by enameled copper wire.

[0009] Further, the bidirectional regulation laminated magnetic sensitive unit 5 is made by blending and solidifying non-magnetized permanent magnetic powder with an elastic matrix, and then magnetizing it in a strong magnetic field. The bidirectional regulation laminated magnetic sensitive unit 5 has residual magnetic flux density inside. When a magnetic field in the same direction is applied, the internal magnetic field of the bidirectional regulation laminated magnetic sensitive unit 5 increases, the modulus rises, and the structural stiffness increases; when a magnetic field in the opposite direction is applied, the internal magnetic field of the bidirectional regulation laminated magnetic sensitive unit 5 decreases, the modulus decreases, and the structural stiffness decreases.

[0010] Further, the curved elastic beams 8 are made of steel material with good elasticity, and are curved after being pre-pressed in structure, and a plurality of curved elastic beams 8 are arranged around the vertical center of the object table 7 in a symmetrical manner, and connect the object table 7 and the base 2.

[0011] Further, in the rigidity bidirectional regulation positive rigidity unit rigidity, inputting the current into the excitation coil 10 will generate a closed magnetic circuit along the sleeve 1-iron core 3-bidirectional regulation laminated magnetic sensitive unit 5-laminated steel sheet 4-bidirectional regulation laminated magnetic sensitive unit 5-supporting table 6-bidirectional regulation shear magnetic sensitive unit 9-sleeve 1, and in different direction magnetic fields, the bidirectional regulation laminated magnetic sensitive unit 5 and the bidirectional regulation shear magnetic sensitive unit 9 will generate reversible bidirectional modulus change, and then generate bidirectional rigidity change, so as to realize real-time quasi-zero of the quasi-zero rigidity vibration isolation system.

[0012] Compared with the prior art, the present application has the following beneficial effects:

[0013] The rigidity bidirectional regulation positive rigidity unit in the present application is a rigidity bidirectional regulation structure. On the one hand, the structure can be bidirectional regulated in rigidity to adapt to the problem that the rigidity is only quasi-zero due to load mismatch or rigidity mismatch of positive and negative rigidity units; on the other hand, the rigidity of the system can be real-time negatively regulated through a control algorithm in the vibration process, so as to greatly improve the vibration isolation frequency band of the quasi-zero rigidity system, and solve the problems of the passive quasi-zero rigidity vibration isolator, such as great difficulty in accurate matching of positive and negative rigidity units, narrow quasi-zero rigidity working interval, great sensitivity to load mass, and jumping phenomenon caused by strong nonlinearity. The structure has the advantages of low energy consumption, simple structure, good stability, and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0014] The present application will be further described below in combination with the drawings and examples.

[0015] Figure 1 It is a structural schematic diagram of the adaptive quasi-zero rigidity vibration isolator based on the bidirectional variable rigidity structure.

[0016] Figure 2 It is a rigidity matching schematic diagram of the conventional quasi-zero rigidity vibration isolator and the magnetic sensitive unit rigidity negatively regulated quasi-zero rigidity vibration isolator.

[0017] Figure 3 It is an amplitude-frequency curve schematic diagram of the conventional quasi-zero rigidity vibration isolator and the magnetic sensitive unit rigidity negatively regulated quasi-zero rigidity vibration isolator.

[0018] In the figure: 1, sleeve, 2, base, 3, iron core, 4, laminated steel sheet, 5, bidirectional regulation laminated magnetic sensitive unit, 6, supporting table, 7, object table, 8, curved elastic beam, 9, bidirectional regulation shear magnetic sensitive unit, 10, excitation coil. DETAILED DESCRIPTION

[0019] This embodiment provides a bidirectional magnetically controlled variable stiffness adaptive quasi-zero stiffness vibration isolator, comprising a sleeve 1, a base 2, an iron core 3, laminated steel sheets 4, a bidirectional adjustable laminated magnetic sensitive unit 5, a support platform 6, a loading platform 7, a bending elastic beam 8, a bidirectional adjustable shear magnetic sensitive unit 9, and an excitation coil 10. Figure 1 The structure shown is composed of...

[0020] Among them, multiple sets of bending elastic beams (8 in total) form a negative stiffness element, in such a case... Figure 1 In the equilibrium position shown, its force F neg The displacement x formula is expressed as

[0021] F neg =2nF beam sinθ

[0022] sinθ=x / L beam

[0023] Where F beam It is the output force of the bending beam, L beam θ is the distance between the endpoints of the bending beams, θ is the angle between the platform and the horizontal plane, and n is the number of bending beams; differentiating both sides of the force-displacement relationship with respect to the displacement yields the negative stiffness k. neg The curve relating to displacement x is as follows

[0024] k neg =-k cons +γ0x 2 +o(x)

[0025] Where, k cons γ0 is a negative stiffness constant, γ0 is a nonlinear coefficient, and o(x) is an infinitesimal. The bidirectional stiffness-adjustable positive stiffness unit, capable of negative stiffness adjustment, consists of a sleeve 1, an iron core 3, laminated steel sheets 4, a bidirectional adjustable laminated magnetic sensitive unit 5, a support platform 6, a bidirectional adjustable shear magnetic sensitive unit 9, and an excitation coil 10. The stiffness of this positive stiffness unit is k. MSE .

[0026] In such Figure 1 In the structure shown, the positive and negative stiffnesses are connected by the base 2 and the platform 7, forming a parallel structure of positive and negative stiffnesses. Its total stiffness is as follows:

[0027] k qzs =-k cons +k MSE +γ0x 2 +o(x)

[0028] When -k cons +k MSEWhen k cons +k MSE ≠0, the characteristics of the system are like a traditional quasi-zero stiffness vibration isolator. In the manufacturing process of the traditional passive quasi-zero stiffness vibration isolator, due to the limitation of process error, it is difficult to match the positive stiffness and the negative stiffness, which may cause the system stiffness not to be exactly zero-k

[0029] By k qzs It can be seen from the expression that the quasi-zero stiffness system has a nonlinear stiffness proportional to the square of displacement. In this case, only by adjusting the system stiffness to be negatively variable with the square term of displacement, the system nonlinearity can be reduced.

[0030] Therefore, the stiffness of the positive stiffness unit can be negatively adjusted in two directions, and the current is input into the excitation coil 10 to form a closed magnetic circuit along the sleeve 1-iron core 3-bidirectional adjustment laminated magnetic sensitive unit 5-laminated steel sheet-4-bidirectional adjustment laminated magnetic sensitive unit 5-supporting table 6-bidirectional adjustment shear type magnetic sensitive unit 9-sleeve 1. When the positive current is input into the excitation coil 10 to excite a magnetic field in the same direction as the residual magnetic flux density of the laminated magnetic sensitive unit 5 and the bidirectional adjustment shear type magnetic sensitive unit 9, the modulus of the bidirectional adjustment laminated magnetic sensitive unit 5 and the bidirectional adjustment shear type magnetic sensitive unit 9 increases, and k MSE increases; when the reverse current is input into the excitation coil 10 to excite a magnetic field in the opposite direction of the residual magnetic flux density of the laminated magnetic sensitive unit 5 and the bidirectional adjustment shear type magnetic sensitive unit 9, the modulus of the bidirectional adjustment laminated magnetic sensitive unit 5 and the bidirectional adjustment shear type magnetic sensitive unit 9 decreases, and k MSE decreases. The above means can realize the function of bidirectional adjustment of stiffness.

[0031] For the traditional quasi-zero stiffness vibration isolator, the quasi-zero stiffness interval is narrow. By using the adaptive quasi-zero stiffness vibration isolator based on the bidirectional variable stiffness structure provided by the present application, the stiffness of the positive stiffness unit can be negatively adjusted in real time, and the quasi-zero stiffness displacement working interval of the system can be greatly improved (such as Figure 2 ).

[0032] At the same time, by negatively adjusting the stiffness of the system in real time through the structure of the present application, the nonlinearity of the system stiffness can be reduced, and the jump phenomenon in the amplitude-frequency curve of the system can be avoided, so as to improve the vibration isolation bandwidth of the system (such as Figure 3 ).

[0033] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A bidirectional magnetically controlled variable-stiffness self-adaptive quasi-zero stiffness vibration isolator, characterized in that: The adaptive quasi-zero stiffness vibration isolator is based on a modulus bidirectional regulation magnetic sensitive unit, a stiffness bidirectional regulation positive stiffness unit, and a negative stiffness unit composed of a bending elastic beam in parallel connection; The stiffness bidirectional regulation positive stiffness unit is composed of a sleeve (1), an iron core (3), a laminated steel sheet (4), a bidirectional regulation laminated magnetic sensitive unit (5), a support table (6), a bidirectional regulation shear magnetic sensitive unit (9), and an excitation coil (10); the negative stiffness unit is composed of a plurality of bending elastic beams (8); the stiffness bidirectional regulation positive stiffness unit and the negative stiffness unit are connected by a material loading table (7) and a base (2); The iron core (3) is arranged at the center of the sleeve (1), and the circular plate-shaped bidirectional regulation laminated magnetic sensitive unit (5) and the circular plate-shaped laminated steel sheet (4) are alternately bonded on the iron core (3) to form a laminated elastic unit; the T-shaped circular table-shaped support table (6) is bonded on the laminated elastic unit; a piece of annular bidirectional regulation shear magnetic sensitive unit (9) is bonded on the outer circular surface of the support table (6) and the inner circular surface of the sleeve (1); and the excitation coil (10) is wound around the iron core (3) by enameled copper wire; The bidirectional regulation laminated magnetic sensitive unit (5) is made by blending non-magnetized permanent magnetic powder with an elastic matrix and solidifying and molding, and then magnetizing in a strong magnetic field; the bidirectional regulation laminated magnetic sensitive unit (5) has residual magnetic flux density inside; when a magnetic field in the same direction is applied, the internal magnetic field of the bidirectional regulation laminated magnetic sensitive unit (5) increases the modulus, resulting in an increase in structural stiffness; when a magnetic field in the opposite direction is applied, the internal magnetic field of the bidirectional regulation laminated magnetic sensitive unit (5) decreases, the modulus decreases, and the structural stiffness decreases; In the stiffness bidirectional regulation positive stiffness unit, inputting current into the excitation coil (10) will generate a closed magnetic circuit along the sleeve (1)-iron core (3)-bidirectional regulation laminated magnetic sensitive unit (5)-laminated steel sheet (4)-bidirectional regulation laminated magnetic sensitive unit (5)-support table (6)-bidirectional regulation shear magnetic sensitive unit (9)-sleeve (1); in different directions of the magnetic field, the bidirectional regulation laminated magnetic sensitive unit (5) and the bidirectional regulation shear magnetic sensitive unit (9) will produce reversible bidirectional modulus changes, and then produce bidirectional stiffness changes, realizing real-time quasi-zero of the quasi-zero stiffness vibration isolation system; The negative stiffness unit is composed of multiple sets of curved elastic beams (8), and in the equilibrium position state, the force F neg The displacement x is expressed by the formula F neg = 2nF beam sinθ sin θ = x / L beam where F beam is the bending beam output force, L beam is the distance between the bending beam endpoints, θ is the angle produced by the object table relative to the horizontal plane, and n is the number of bending beams. The force displacement is derived on both sides for displacement, and the negative stiffness k is obtained neg The relationship curve with displacement x is as shown k neg = -k cons + γ0x 2 + o(x) Wherein, k cons is a negative stiffness constant, gamma0 is a nonlinear coefficient, o(x) is an infinitesimal; wherein, the stiffness bidirectional regulation positive stiffness unit can be negatively regulated, which is composed of a sleeve (1), an iron core (3), a laminated steel sheet (4), a bidirectional regulation laminated magnetic sensitive unit (5), a support table (6), a bidirectional regulation shear type magnetic sensitive unit (9), and an excitation coil (10); the stiffness of the positive stiffness unit is k MSE . The positive and negative stiffnesses are connected by the base (2) and the material loading table (7) to form a positive and negative stiffness parallel structure; the total stiffness is represented as k qzs = -k cons + k MSE + γ0x 2 + o(x) When -k cons +k MSE = 0, the system is a quasi-zero stiffness isolator. By k qzs It is known that the quasi-zero stiffness system has a nonlinear stiffness proportional to the square of displacement. By adjusting the negative stiffness of the quadratic term of displacement, the system nonlinearity is reduced.

2. The bidirectional magnetic controlled variable stiffness self-adaptive quasi-zero stiffness vibration isolator according to claim 1, wherein: The bending elastic beam (8) is made of a steel material with good elasticity, and bends under a pre-pressure in the structure; a plurality of bending elastic beams (8) are symmetrically arranged around the vertical center of the material loading table (7) and connect the material loading table (7) and the base (2).

3. The bidirectional magnetic controlled variable stiffness self-adaptive quasi-zero stiffness vibration isolator according to claim 1, wherein: The positive stiffness unit with bidirectional stiffness regulation can be negatively regulated. When inputting current into the excitation coil (10), a closed magnetic circuit along the sleeve (1)-core (3)-bidirectional regulation laminated magnetic sensitive unit (5)-laminated steel sheet (4)-bidirectional regulation laminated magnetic sensitive unit (5)-supporting table (6)-bidirectional regulation shearing type magnetic sensitive unit (9)-sleeve (1) is generated. When inputting positive current into the excitation coil (10), a magnetic field in the same direction as the residual magnetic flux density of the bidirectional regulation laminated magnetic sensitive unit (5) and the bidirectional regulation shearing type magnetic sensitive unit (9) is excited, the modulus of the bidirectional regulation laminated magnetic sensitive unit (5) and the bidirectional regulation shearing type magnetic sensitive unit (9) increases, k MSE increases; when inputting reverse current into the excitation coil (10), a magnetic field in the opposite direction of the residual magnetic flux density of the bidirectional regulation laminated magnetic sensitive unit (5) and the bidirectional regulation shearing type magnetic sensitive unit (9) is excited, the modulus of the bidirectional regulation laminated magnetic sensitive unit (5) and the bidirectional regulation shearing type magnetic sensitive unit (9) decreases, k MSE decreases, realizing the function of bidirectional stiffness regulation.

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