CN106402267A - Extension type quasi-zero stiffness vibration isolator and implementation method thereof - Google Patents

Abstract

The invention relates to a tension type quasi-zero stiffness vibration isolator and its realization method. The vibration isolator is composed of a negative stiffness mechanism connected in parallel with a positive stiffness main spring, wherein the negative stiffness mechanism is composed of a tension spring, a connecting rod, a slide Composed of blocks and guide rails, it can produce negative stiffness in the vertical direction, and can avoid the disadvantage of compression spring instability, and can ensure the left-right symmetry of the structure when fine-tuning in the horizontal direction. According to the principle of positive and negative stiffness cancellation, after the negative stiffness mechanism is connected in parallel with the positive stiffness spring, the stiffness of the vibration isolator at the equilibrium position is close to zero, and the natural frequency is also close to zero, so that the initial vibration isolation frequency is greatly reduced and the vibration isolation range is increased. , has the ability to isolate low-frequency or ultra-low-frequency vibrations. The vibration isolator is simple in structure, compact in structure, easy to assemble and debug, and has certain engineering application value in the fields of automobile, precision instrument, sensitive equipment, precision machining, aerospace engineering and so on.

Description

Tensile quasi-zero stiffness vibration isolator and its realization method

technical field

The invention relates to the field of vibration isolation devices, in particular to a tensile type quasi-zero stiffness vibration isolator and a realization method thereof.

Background technique

Vibration is the most common phenomenon in nature. It can be seen everywhere in daily life and production, such as leaves swaying in the wind, heart beating, cars bumping on the road, etc. From simple pendulums to complex bodies, from microscopic objects to macroscopic objects, vibration phenomena are everywhere. Among them, many vibrations will seriously affect people's life and industrial production, causing a lot of losses. Therefore, vibration isolation is an eternal research topic for human beings.

The continuous development of high-precision technology has made the application field of vibration isolation technology, especially low-frequency vibration isolation technology, wider. Therefore, more and more people are exploring and researching low-frequency vibration isolation technology. Since the linear vibration isolation technology is relatively mature, the isolation of medium and high frequency vibrations can be well realized, but the isolation of low frequency or ultra-low frequency vibrations is still a technical problem. According to the vibration theory, when the vibration frequency of the external excitation is greater than the natural frequency of the system, times, the linear system can start vibration isolation, that is, the transmissibility is less than 1. The premise of isolating low-frequency vibration is that the natural frequency of the vibration isolation system must be very low, which cannot be achieved because ordinary linear vibration isolation systems cannot overcome the trade-off between stiffness and load-bearing mass. A nonlinear vibration isolation system composed of positive and negative stiffness in parallel can solve this problem. It uses the principle of positive and negative stiffness cancellation to make the stiffness of the system close to zero, also known as quasi-zero stiffness vibration isolation system. While ensuring the bearing capacity of the system, the stiffness of the system is effectively reduced, so that the natural frequency of the entire system is greatly reduced, the initial vibration isolation frequency is reduced, the vibration isolation interval is increased, the vibration isolation capacity is improved, and low frequency vibration isolation is realized. Therefore, quasi-zero stiffness vibration isolators have broad application prospects.

Contents of the invention

In view of this, the purpose of the present invention is to provide a tensile quasi-zero stiffness vibration isolator and its realization method, which can not only ensure the bearing quality but also ensure extremely low stiffness, reduce the initial vibration isolation frequency, and increase the vibration isolation interval , to achieve low frequency or ultra-low frequency vibration isolation.

The present invention adopts the following schemes to realize: a tensile quasi-zero stiffness vibration isolator, including a base, a main spring, an adjusting nut, a bolt seat, a sleeve cover, a stage, a tension spring, a connecting rod, a slider, and a guide rail , a cross bar, an upper hinge seat, a side hinge seat and a support seat; the middle part of the base is equipped with the bolt seat and the adjusting nut for adjusting the main spring to move up and down; the main spring is a positive stiffness spring , the upper and lower ends of the main spring are respectively positioned and supported by the cover and the adjusting nut; the cover is installed on the bottom center of the stage for placing the vibration-isolated object; the tension spring, connecting rod , a slider and a guide rail form a negative stiffness mechanism, one end of the connecting rod is connected to the stage through a side hinge seat, and the other end is connected to the slider through an upper hinge seat, and the slider is arranged on the guide rail on, used to slide left and right on the track; the cross bar is fixed on the two sliders, used to make the two sliders move simultaneously.

Further, one end of the tension spring in the negative stiffness mechanism is connected to the crossbar through a fixing seat, and the other end of the tension spring is provided with a micrometer fine-tuning device for adjusting the deformation of the tension spring, so The fine-tuning device of the differential head includes a differential head, the other end of the tension spring is connected with the differential head through a connecting block, and the differential head is fixed on the cross bar.

Further, the guide rail is installed on the support seat, and the support seat is fixed on the base.

In particular, the vibration isolator mainly consists of a negative stiffness mechanism with negative stiffness characteristics and a positive stiffness spring for supporting a weight. When the negative stiffness mechanism and the positive stiffness spring are connected in parallel, the stiffness of the system can be close to zero, which has quasi-zero stiffness characteristics.

The present invention also adopts following method to realize: a kind of realization method of tensile type quasi-zero stiffness vibration isolator comprises the following steps:

Step S1: Place a vibration-isolated object with a weight of mg on the stage, the stage moves downward, the main spring is compressed, and the slider moves outward under the action of the connecting rod , the tension spring is elongated;

Step S2: The adjustment nut supported by the bottom end of the main spring is adjusted to move up and down to adjust the up and down position of the main spring so that the connecting rod is kept at a horizontal position to ensure that the system is in a balanced position. ;

Step S3: Rotate the differential head to fine-tune the tension of the tension spring, which plays a role in fine-tuning, facilitates debugging, and ensures the quasi-zero stiffness characteristics of the system; the weight of the vibration-isolated object is borne by the main spring , the tension spring does not play a supporting role, and the vibration isolator is in a balanced position.

Further, the stiffness of the main spring is k _v , the stiffness of the extension spring is k _h , and its force is as follows:

It is dimensionless to obtain the relationship between dimensionless force and dimensionless displacement:

in:

Deriving the dimensionless force yields the relationship between dimensionless stiffness and dimensionless displacement:

Then when the vibration isolator is in the equilibrium position, Substituting into the above formula, the stiffness at the equilibrium position can be obtained:

When the vibration isolator is at the equilibrium position, the stiffness is zero, so that the above formula is equal to zero, that is:

Further, the The parameter conditions that the vibration isolator needs to meet to ensure the quasi-zero stiffness characteristics, if the conditions are met, the vibration isolator can achieve low-frequency or ultra-low-frequency vibration isolation.

Compared with the prior art, the present invention has the following beneficial effects: Compared with the traditional linear vibration isolator, the tensile quasi-zero stiffness vibration isolator of the present invention can effectively reduce the load capacity of the system while ensuring the bearing capacity of the system. Stiffness, so that the natural frequency of the entire system is close to zero, so that the initial vibration isolation frequency is reduced, the vibration isolation interval is increased, the vibration isolation capability is improved, and low-frequency or ultra-low-frequency vibration isolation is realized. Compared with other vibration isolators of the same type, the negative stiffness mechanism of the present invention is composed of tension springs, connecting rods and sliders, which can avoid the disadvantage of compression spring instability, and has a simple structure, compact space, and easy assembly. The left-right symmetry of the structure can be ensured during fine-tuning. Moreover, the vibration isolator is provided with adjustment mechanisms in the vertical and horizontal directions, which is convenient for debugging after assembly, and is suitable for vibration-isolated objects of different masses.

Description of drawings

Fig. 1 is a schematic diagram of the initial state of the tensile quasi-zero stiffness vibration isolator.

Fig. 2 is the force-displacement characteristic curve of the tensile quasi-zero stiffness system.

Fig. 3 is the stiffness-displacement characteristic curve of the tensile quasi-zero stiffness system.

Fig. 4 is a comparison chart of the displacement transmissibility curves of the tensile quasi-zero stiffness system and the linear system.

Fig. 5 is a three-dimensional schematic diagram of the initial state of the tensile quasi-zero stiffness vibration isolator.

Fig. 6 is a schematic diagram of the initial state structure of the tensile quasi-zero stiffness vibration isolator.

Fig. 7 is a schematic diagram of the structure of the tensile quasi-zero-stiffness vibration isolator after placing heavy objects.

In the figure: 1-base; 2-support seat; 3-guide rail; 4-slider; 5-crossbar; 6-fixed seat; 7-upper hinge seat; -side hinge seat; 11-stage; 12-cover; 13-connecting block; 14-installation seat; 15-differential head; 16-main spring; 17-adjusting nut; 18-bolt seat; vibrating object.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

This embodiment provides a tensile quasi-zero stiffness vibration isolator, as shown in Figures 5 to 7, including a base 1, a main spring 16, an adjusting nut 17, a bolt seat 18, a cover 12, and a stage 11 , tension spring 9, connecting rod 8, slider 4, guide rail 3, cross bar 5, upper hinge seat 7, side hinge seat 10 and support seat 2; the middle part of the base 1 is equipped with the bolt seat 18 and the To adjust the adjustment nut 17 that the main spring 16 moves up and down; The cover 12 is installed on the bottom center of the object table 11 for placing the vibration-isolated object 19; the tension spring 9, the connecting rod 8, the slide block 4 and the guide rail 3 form a negative stiffness mechanism, and the connecting rod 8 One end of one end is connected with the said stage 11 through the side hinge seat 10, and the other end is connected with the said slider 4 through the upper hinge seat 7, and the said slider 4 is arranged on the said guide rail 3, in order to 3 to slide left and right; the cross bar 5 is fixed on the two sliders 4 to make the two sliders move simultaneously.

In this embodiment, one end of the extension spring 9 in the negative stiffness mechanism is connected to the crossbar 5 through the fixing seat 6, and the other end of the extension spring 9 is provided with a The differential head fine-tuning device, said differential head fine-tuning device comprises a differential head 15, the other end of said tension spring 9 is connected with said differential head 15 through connecting block 13, and said differential head 15 is fixed on said cross bar 5 on.

In this embodiment, the guide rail 3 is installed on the support base 2 , and the support base 2 is fixed on the base 1 .

In this embodiment, the vibration isolator mainly consists of a negative stiffness mechanism with negative stiffness characteristics and a positive stiffness spring for supporting a weight. When the negative stiffness mechanism and the positive stiffness spring are connected in parallel, the stiffness of the system can be close to zero, which has quasi-zero stiffness characteristics.

In this embodiment, a method for realizing a tensile quasi-zero stiffness vibration isolator comprises the following steps:

Step S1: Place a vibration-isolated object with a weight of mg on the stage, the stage moves downward, the main spring is compressed, and the slider moves outward under the action of the connecting rod , the tension spring is elongated;

Step S2: The adjusting nut supported by the bottom end of the main spring is adjusted to move up and down to adjust the up and down position of the main spring so that the connecting rod is kept in a horizontal position to ensure that the system is in a balanced position;

Step S3: Rotate the differential head to fine-tune the tension of the tension spring, which plays a role in fine-tuning, facilitates debugging, and ensures the quasi-zero stiffness characteristics of the system. The weight of the vibration-isolated object is borne by the main spring , the tension spring does not play a supporting role, and the vibration isolator is in a balanced position.

In this embodiment, considering manufacturing and assembly errors, and adapting to objects of different qualities, adjustment devices are provided in vertical and horizontal directions. The adjusting nut 17 supported by the bottom end of the main spring 16 can move up and down to adjust the up and down position of the main spring 16 to ensure that objects of different masses can be in a balanced position after being put on. In the horizontal direction, one end of the extension spring 9 is connected to the differential head 15 , and the stretching amount of the extension spring 9 can be fine-tuned by rotating the differential head 15 . The vertical and horizontal adjustment mechanisms facilitate the debugging of the vibration isolator after assembly, and can ensure the quasi-zero stiffness characteristics of the system.

In this embodiment, the static analysis is carried out on the vibration isolator, and the structural diagram and system parameters are shown in Figure 1; the stiffness of the main spring is k _v , the original length is L _v0 , and the stiffness of the extension spring is k _h , the original length is L _h0 , and the length at any time is L _h . The length of the connecting rod is a, and the angle between the connecting rod and the horizontal is β. The displacement of point A from the equilibrium position is u. The distance between point C and point F is D. In the initial state, the distance from point A to the equilibrium position is h ₀ . Its force is as follows:

It is dimensionless to obtain the relationship between dimensionless force and dimensionless displacement:

in:

Deriving the dimensionless force yields the relationship between dimensionless stiffness and dimensionless displacement:

Then when the vibration isolator is in the equilibrium position, Substituting into the above formula, the stiffness at the equilibrium position can be obtained:

In order to ensure that the stiffness of the vibration isolator at the equilibrium position is zero, the above formula is set to be zero, and:

The above formula is the prerequisite for realizing zero stiffness, only when α, and When the parameters meet the above conditions, the vibration isolator can achieve quasi-zero stiffness at the equilibrium position, ensuring that the natural frequency of the system is extremely low.

according to conditions , a set of parameters can be obtained , , the vibration isolator has quasi-zero stiffness characteristics at the equilibrium position, and has low-frequency vibration isolation performance.

by parameter , , the force-displacement characteristic curve and stiffness-displacement characteristic curve can be obtained, as shown in Figure 2 and Figure 3. It can be seen from the figure that the system is in the equilibrium position ( ) around the small range, the system stiffness is close to zero. It shows that when the system is near the equilibrium position, the natural frequency is very low, which is suitable for isolating low-frequency and small-amplitude vibrations. At the equilibrium position, the weight of the vibration-isolated object is supported by the main spring, and the negative stiffness mechanism does not play a load-bearing role. In order to ensure that the vibration-isolated objects of different masses can be in a balanced position, an adjustment mechanism is provided at the lower end of the main spring to adjust according to the weight of the vibration-isolated objects, so that the system is in a balanced position.

In this embodiment, the dynamic analysis of the vibration isolator is carried out. When the foundation is subjected to displacement harmonic excitation y=Y sinωt, the object to be isolated will move up and down at the equilibrium position. Let the displacement of the object be x to establish kinematics The equation is as follows:

let u=xy, Substitute into the above formula to get:

Dimensionless the above formula, we get:

in,

The harmonic balance method is used to solve the above formula, and the periodic solution of the system is assumed to be Substituting into the motion equation, the amplitude-frequency characteristic equation and phase-frequency characteristic equation of the system can be obtained, as follows:

Therefore, the displacement transmissibility of the system is as follows:

When the parameters of the system are selected, they are substituted into the transmissibility formula to obtain the transmissibility curve of the system, as shown in Figure 4. It can be seen from the figure that under the excitation of different amplitudes, compared with the linear system, the tensile quasi-zero stiffness system has a lower initial vibration isolation frequency, a larger vibration isolation interval, and a better low-frequency vibration isolation effect.

In this embodiment, the working principle of the vibration isolator obtained from the above analysis is as follows: As shown in Figure 7, after determining the quality of the vibration-isolated object, select certain system parameters, and the vibration-isolated object is placed on the stage Make sure the system is in a balanced position after getting on. The main spring with positive stiffness supports the weight of the object, and the negative stiffness mechanism produces negative stiffness in the vertical direction. According to the principle of positive and negative stiffness cancellation, the system is in a state of zero stiffness at the equilibrium position, and the system stiffness near the equilibrium position is also very low , close to zero. Therefore, the natural frequency of the system is extremely low within a certain range near the equilibrium position. When the basic vibration is transmitted to the object to be isolated, due to the extremely low natural frequency of the system, the frequency of vibration isolation is very low, which can isolate low-frequency or ultra-low-frequency vibration.

To sum up, the tensile quasi-zero-stiffness vibration isolator in this embodiment has a good effect in low-frequency or ultra-low-frequency vibration isolation, which is incomparable to the traditional linear vibration isolation system (that is, removing the negative stiffness mechanism). And the structure is simple, compact, easy to assemble and debug, and has certain engineering application value in the fields of automobile, precision instrument, sensitive equipment, precision machining, aerospace engineering and so on.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (6)

1. A tensile type quasi-zero stiffness vibration isolator is characterized in that: comprising a base, a main spring, an adjusting nut, a bolt seat, a cover, a stage, an extension spring, a connecting rod, a slide block, a guide rail, cross bar, upper hinge seat, side hinge seat and support seat; the middle part of the base is equipped with the bolt seat and the adjusting nut for adjusting the main spring to move up and down; the main spring is a positive stiffness spring, The upper and lower ends of the main spring are respectively positioned and supported by the cover and the adjusting nut; the cover is installed on the bottom center of the stage for placing the vibration-isolated object; the tension spring, connecting rod, The slider and the guide rail form a negative stiffness mechanism. One end of the connecting rod is connected to the stage through a side hinge seat, and the other end is connected to the slider through an upper hinge seat. The slider is arranged on the guide rail , used to slide left and right on the track; the cross bar is fixed on the two sliders and used to move the two sliders simultaneously. 2. A kind of tensile quasi-zero stiffness vibration isolator according to claim 1, characterized in that: one end of the tension spring in the negative stiffness mechanism is connected with the cross bar through a fixing seat, and the tension spring The other end of the extension spring is provided with a differential head fine-tuning device for adjusting the amount of deformation of the tension spring, and the differential head fine-tuning device includes a differential head, and the other end of the extension spring is connected with the differential head through a connecting block, The differential head is fixed on the cross bar. 3. A tensile quasi-zero-stiffness vibration isolator according to claim 1, characterized in that: the guide rail is installed on the support seat, and the support seat is fixed on the base. 4. a method for realizing based on the tensile type quasi-zero stiffness vibration isolator claimed in claim 1, is characterized in that: comprises the following steps: Step S1: Place a vibration-isolated object with a weight of mg on the stage, the stage moves downward, the main spring is compressed, and the slider moves outward under the action of the connecting rod , the tension spring is elongated; Step S2: The adjusting nut supported by the bottom end of the main spring is adjusted to move up and down to adjust the up and down position of the main spring so that the connecting rod is kept in a horizontal position to ensure that the system is in a balanced position; Step S3: Rotate the differential head to fine-tune the stretching amount of the stretching spring, which acts as a fine-tuning function to ensure the quasi-zero stiffness characteristics of the system; the weight of the vibration-isolated object is borne by the main spring, and the stretching The spring does not act as a support, and the vibration isolator is in a balanced position. 5. the realization method of a kind of tensile quasi-zero stiffness vibration isolator according to claim 4, is characterized in that: The stiffness of the main spring is k _v , the stiffness of the extension spring is k _h , and its force is as follows: It is dimensionless to obtain the relationship between dimensionless force and dimensionless displacement: in: Deriving the dimensionless force yields the relationship between dimensionless stiffness and dimensionless displacement: Then when the vibration isolator is in the equilibrium position, Substituting into the above formula, the stiffness at the equilibrium position can be obtained: When the vibration isolator is at the equilibrium position, the stiffness is zero, so that the above formula is equal to zero, that is: 6. the realization method of a kind of tensile type quasi-zero stiffness vibration isolator according to claim 4, is characterized in that: said The parameter conditions that the vibration isolator needs to meet to ensure the quasi-zero stiffness characteristics, if the conditions are met, the vibration isolator can achieve low-frequency or ultra-low-frequency vibration isolation.