Constant quasi-zero stiffness vibration isolation structure and method based on negative stiffness mechanism of two pairs of oblique rods

Abstract

The present invention discloses a constant-value quasi-zero stiffness vibration isolation structure and method based on the negative stiffness mechanism of two pairs of oblique rods, wherein brackets are symmetrically installed on both sides of a fixed plate, a vertical guide rod is installed in the middle of the fixed plate, a support connecting block is installed on the upper part of the vertical guide rod, and a vertical guide rod linear bearing connected to the vertical guide rod is installed on the support connecting block; a vertical spring is installed on the vertical guide rod between the bottom of the support connecting block and the fixed plate; the left and right ends of the support connecting block are connected to an oblique rod hinge support; linear bearings are installed at equal intervals on each bracket, each linear bearing is equipped with a transverse guide rod, and a transverse spring is installed on each transverse guide rod between the spring clamping plate and the bracket; two pairs of oblique rods are provided, one end of the oblique rod is hinged to the U-shaped groove through a shaft rod, and the other end is hinged to the oblique rod hinge support; a bolt is passed through the hollow tube and connected to the connecting hole to fix the load plate.

Description

Technical Field

[0001] The present invention relates to the field of vibration control, and in particular to a constant-value quasi-zero stiffness vibration isolation structure and method based on a negative stiffness mechanism of two pairs of oblique rods. Background Art

[0002] Reference [1] studies a single pair of diagonal rods with a quasi-zero stiffness model, which has a cubic nonlinear stiffness factor. Under large excitation, the transmissibility bends to the right, reducing the vibration isolation frequency band. Furthermore, the parameter design method given in this reference is complex (including several inequalities), making it difficult to design and apply. The technical solution in the above reference cannot achieve a straight zero stiffness characteristic near the static equilibrium point, cannot reduce the resonant frequency of the linear oscillator, and is affected by nonlinear factors. Under large excitation conditions, the vibration isolation frequency band will be reduced due to the nonlinear rightward bending.

[0003] Reference [2] proposes a method for debugging a constant quasi-zero stiffness based on a vibration isolator constructed with a single pair of diagonal rods and a negative stiffness mechanism. This application proposes another constant quasi-zero stiffness structure in the form of a different structure and a different debugging method, which is completely different from that of reference [2] in terms of structure and debugging method. The horizontal spring of reference [2] requires a larger stiffness, while the horizontal spring of this patent application requires a smaller stiffness, which is more suitable for smaller spaces in terms of structure. Although both are constant quasi-zero stiffness structures, there are some obvious differences in the use effects. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a constant-value quasi-zero stiffness vibration isolation structure and method based on a negative stiffness mechanism of two pairs of oblique rods.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A constant-value quasi-zero stiffness vibration isolation structure based on a negative stiffness mechanism of two pairs of diagonal rods, comprising a fixed plate, a bracket, a transverse guide rod, a diagonal rod, a diagonal rod hinge support, a support connection block, a vertical guide rod, a vertical spring, a hollow tube, a load plate and a transverse spring; brackets are symmetrically mounted on both sides of the fixed plate, a vertical guide rod is mounted in the middle of the fixed plate, a support connection block is mounted on the upper part of the vertical guide rod, a vertical guide rod linear bearing connected to the vertical guide rod is mounted on the support connection block; a vertical spring is mounted on the vertical guide rod between the bottom of the support connection block and the fixed plate;

[0007] The left and right ends of the support connecting block are connected to the oblique rod hinge support, and the oblique rod hinge support is a U-shaped structure; each of the brackets is provided with two circular through holes at equal intervals, a linear bearing is installed in each through hole through a retaining spring, a transverse guide rod is installed in each linear bearing, and each transverse guide rod is provided with a U-shaped groove at one end facing the vertical guide rod, a spring clamping plate is provided on the transverse guide rod next to the U-shaped groove, and a transverse spring is installed on each transverse guide rod between the spring clamping plate and the bracket;

[0008] Two oblique rods are symmetrically arranged on both sides of the vertical guide rod, one end of the oblique rod is hinged to the U-shaped groove through the shaft rod, and the other end is hinged to the oblique rod hinge support;

[0009] Connecting holes are respectively provided on both sides of the support connecting block, a hollow tube is provided on the connecting hole, a load plate is provided on the top of the hollow tube, and the load plate is fixed to the connecting hole by bolts passing through the hollow tube.

[0010] The present invention also provides a method for debugging a constant-value quasi-zero stiffness vibration isolation structure based on the two pairs of diagonal rod negative stiffness mechanisms, comprising:

[0011] S1. Based on the parameters of the quasi-zero stiffness characteristic, determine the initial precompression δ2 of the upper and lower transverse springs, the horizontal projection length a of the distance between the hinge points of the two diagonal rods, and the length of the vertical spring, so that δ2 = a in the initial state. The initial state refers to the state where the intersection of the two pairs of diagonal rods contacts the top of the free-length vertical spring.

[0012] S2. Set the stiffness of the two pairs of lateral springs from top to bottom in the constant quasi-zero stiffness isolation structure to be k1, and the stiffness of the vertical spring to be k2. By determining the stiffness k1 of the lateral spring and the stiffness k2 of the vertical spring, the dimensionless parameter is constructed. Make the parameter α satisfy 0<α<0.25;

[0013] S3. After determining the above parameters, draw the force-displacement curve fx, where f is the applied force, i.e., the force applied to the load plate, and x is the displacement from the initial position. At this point, the force-displacement curve is an inclined straight line with a constant quasi-zero stiffness characteristic. Calculate the stiffness value K. Calculate the starting vibration isolation frequency based on the relationship between the vibration isolation mass m on the load plate. If the initial vibration isolation frequency does not meet the design requirements, repeat steps S1 to S3.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0015] 1. The present invention proposes a constant quasi-zero stiffness vibration isolator constructed with two pairs of inclined rods and a horizontal spring negative stiffness mechanism. This structure is the first to be proposed in the research on constant quasi-zero stiffness.

[0016] 2. The present invention proposes a constant quasi-zero stiffness vibration isolation structure constructed with a negative stiffness mechanism of two pairs of diagonal rods, and performs parameter design to obtain force and stiffness expressions that are completely different from the prior art; at the static equilibrium point, the stiffness is set to zero and the second-order derivative of the stiffness is set to zero, obtaining two zero stiffness parameter conditions. Adjusting the constant quasi-zero stiffness on demand according to the parameter conditions is a new debugging method with simple debugging and excellent accuracy. During parameter design (theoretical and technical analysis), the so-called static equilibrium point position refers to the state in which the two pairs of diagonal rods are centrally symmetrical (or the state in which the middle pair of diagonal rods are horizontal). The two pairs of horizontal springs have the same free length.

[0017] 3. Through the constant quasi-zero stiffness debugging method of the present invention, a zero stiffness characteristic with a straight line near the static equilibrium point can be obtained, and a constant quasi-zero stiffness characteristic with a wider range can be obtained, which can reduce the resonant frequency of the linear oscillator without any nonlinear factors. Compared with the traditional quasi-zero stiffness isolator with weak cubic nonlinear characteristics (non-constant quasi-zero stiffness), under large excitation conditions, the vibration isolation frequency band will not be reduced due to nonlinear right bending.

[0018] 4. This invention solves the cubic nonlinearity problem of traditional quasi-zero stiffness isolators and can be used for low-frequency vibration isolation in conditions with large excitation amplitudes and variable loads. This constant-value quasi-zero stiffness isolation structure achieves an infinite number of static equilibrium positions.

[0019] 5. The present invention uses a large number of transverse springs, which allows for the use of smaller, lower-rigidity transverse springs (such springs are cheaper), reducing manufacturing, application, and maintenance costs. This allows for a smaller, constant-value, quasi-zero-rigidity vibration isolation structure.

[0020] 6. The present invention adopts two pairs of transverse springs, which has more design parameters, more optional parameters and a wider range of applications.

[0021] 7. The present invention can be applied to engineering applications of low-frequency vibration isolation, solving the contradictory problem that traditional linear stiffness vibration isolation systems require small dynamic stiffness but produce large static deformation during low-frequency vibration isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the constant-value quasi-zero stiffness vibration isolation structure of the present invention.

[0023] Figure 2a and Figure 2b They are respectively the front view and the left view of the bracket in the embodiment.

[0024] Figure 3 This is the main view of the diagonal rod.

[0025] Figure 4a and Figure 4b They are the main view and top view of the diagonal rod hinge support respectively.

[0026] Figure 5a and Figure 5b They are the front view and top view of the transverse guide rod respectively.

[0027] Figure 6a and Figure 6b They are the main view and top view of the support connection block respectively.

[0028] Figure 7 and Figure 8 They are respectively simplified mechanical schematic diagrams of the constant quasi-zero stiffness vibration isolation structure of the present invention.

[0029] Figure 9a and Figure 9b They are schematic diagrams of stiffness-displacement curve and force-displacement curve respectively.

[0030] Figure markings: 1-fixed plate, 2-bracket, 3-linear bearing, 4-lateral guide rod, 5-spring clamp, 6-radial bearing, 7-diagonal rod, 8-diagonal rod hinge support, 9-support connecting block, 10-vertical guide rod, 11-vertical spring, 12-hollow tube, 13-load plate, 14-vertical guide rod linear bearing, 15-lateral spring, 16-thick vertical through hole, 17-thin vertical through hole. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] like Figure 1 As shown, this embodiment provides a constant-value quasi-zero stiffness vibration isolation structure based on a negative stiffness mechanism of two pairs of diagonal rods, including a fixed plate 1, a bracket 2, a transverse guide rod 4, a diagonal rod 7, a diagonal rod hinge support 8, a support connection block 9, a vertical guide rod 10, a vertical spring 11, a hollow tube 12, a load plate 13 and a transverse spring 15;

[0033] Brackets 2 are symmetrically mounted on either side of the fixed plate 1. The bottom of the brackets 2 is fixed to the fixed plate 1 via standard bolts. A vertical guide rod 10 is mounted in the middle of the fixed plate 1. A support connecting block 9 is mounted above the vertical guide rod 10. A vertical guide rod linear bearing 14 is mounted on the support connecting block 9 and connected to the vertical guide rod 10. A vertical spring 11 is mounted on the vertical guide rod 10 between the bottom of the support connecting block 9 and the fixed plate 1.

[0034] The left and right ends of the support connecting block 9 are connected to the inclined rod hinge support 8, and the inclined rod hinge support 9 is a U-shaped structure; two circular through holes are provided on each bracket 2 at equal intervals, and a linear bearing 3 is installed in each through hole through a retaining spring, and a transverse guide rod 4 is installed in each linear bearing. Figure 2a and Figure 2b In this embodiment, two circular through holes are set at equal intervals on the bracket 2. The linear bearing 3 of the standard part has a retaining spring groove. The linear bearing 3 and the bracket 2 are connected through the standard retaining spring to constrain the lateral displacement of the lateral guide rod linear bearing 3.

[0035] Each transverse guide rod 4 is provided with a U-shaped groove at one end thereof facing the vertical guide rod 10, a spring clamp 5 is provided on the transverse guide rod next to the U-shaped groove, and a transverse spring 15 is installed on each transverse guide rod 4 between the spring clamp 5 and the fixing member;

[0036] Two oblique rods 7 are symmetrically arranged on both sides of the vertical guide rod 10. The structure of the oblique rod 7 is shown in Figure 4. The two ends of each oblique rod 7 are respectively hinged to the oblique rod hinge support 8 and the U-shaped groove on the horizontal guide rod 4 through the radial bearing 6 and the pin. Specifically, the oblique rod 7 ( Figure 3 ) There is a round hole at the end, which fits with the outer ring of the radial bearing (the radial bearing is relatively small, with an outer diameter of 5mm, an inner diameter of 2mm, and a thickness of about 2mm. Most sales platforms call it a miniature bearing). Insert one end of the inclined rod 7 with the radial bearing into the transverse guide rod 4 ( Figure 5b Then insert the pin into Figure 5a The aperture on the right-hand side also passes the endoporus of radial bearing.At this moment, oblique rod 7 and transverse guide rod 4 were hinged together by radial bearing.

[0037] There are connecting holes on both sides of the support connecting block 9. A hollow tube 12 is provided on the connecting hole. A load plate 13 is provided on the top of the hollow tube 12 and the load plate 13 is fixed to the connecting hole by bolts passing through the hollow tube 12.

[0038] See Figure 4a and 4b In this embodiment, the diagonal rod hinge support 8 is a U-shaped structure, consisting of a bottom plate and two side plates. The bottom plate is provided with bolt holes for connecting with the support connecting block 9, and two axial holes are symmetrically provided on the two side plates for hinged connection with the diagonal rod.

[0039] See Figure 5a and 5b One end of the transverse guide rod is provided with a U-shaped groove, and the side plates on both sides of the U-shaped groove are symmetrically provided with axis holes for hinged connection of the oblique rod. The transverse guide rod next to the U-shaped groove is provided with a groove for installing the spring clamp 5.

[0040] See Figure 6a and 6b, bolt holes for connecting the hinge support 8 are provided at both ends of the support connecting block, a bearing hole is provided in the middle, and connection holes for fixing the load plate are provided on both sides.

[0041] In this embodiment, the diagonal rod hinge support 8 is connected to the support connection block 9 by a stud, and the support connection block 9, the hollow tube 12, the load plate 13, and the vertical guide rod linear bearing 14 are fastened together by standard long bolts. The vibration isolation mass force exerted on the load plate 13 can be transmitted to the two pairs of diagonal rods 7. The transverse guide rod 4 is constrained by the transverse guide rod linear bearing 3 and can move horizontally with low friction. The transverse spring 15 is axially constrained by the spring clamp 5 and the transverse guide rod linear bearing 3. The elastic force of the transverse spring can be transmitted to the load plate 13 through the diagonal rod 7 to obtain vertical force support, especially to obtain negative stiffness characteristics in the vertical direction. The vertical spring 11 is constrained by the vertical guide rod 10, and the vertical displacement is limited by the vertical guide rod linear bearing 14 and the fixed plate 1, so that the load plate 13 obtains load-bearing capacity.

[0042] The constant quasi-zero stiffness vibration isolation structure constructed by two pairs of diagonal rods with negative stiffness mechanism, the mechanical diagram of the initial state is shown in Figure 7 and Figure 8 k2 is the vertical spring stiffness, f h is the inward elastic force generated by the transverse spring (or horizontal tension spring), f h_u is the elastic force generated by the upper lateral spring, f h_l is the elastic force generated by the lower pair of lateral springs, h is the vertical distance from the initial state to the static equilibrium position, x is the displacement from the initial position, and y is the displacement from the static equilibrium position. a is the horizontal projection of the distance between the hinge points at both ends of the diagonal rod in the initial state; α is the ratio of the lateral spring stiffness to the vertical spring stiffness; δ is the pre-compression length of the upper pair of lateral springs in the initial state; and δ2 is the pre-compression length of the lower pair of lateral springs in the initial state. The vertical distance between the horizontal position of the upper pair of diagonal springs and the horizontal position of the lower pair of diagonal springs is 2d, and the midpoint of 2d is the static equilibrium position.

[0043] First, the expression of the applied force f is obtained. In order to analyze a wider range of structural parameter characteristics, the applied force f and its expression are subjected to dimensionless stiffening formula (1), and the dimensionless applied force f can be obtained. expression, find expression right The first-order derivative of can be obtained as dimensionless stiffness Formula (2); Formula (3) is a parameter expression; at the static equilibrium position, for the dimensionless stiffness By calculating the first-order derivative and the second-order derivative respectively, we can obtain the parameter conditions of the zero stiffness characteristic, (4). Taking the static equilibrium position as the zero point displacement, the static equilibrium point is Figure 7 At the middle position of 2D, the quasi-zero stiffness characteristics near the static equilibrium point are as follows Figure 7 As shown, it has the characteristics of constant quasi-zero stiffness (the dynamic stiffness of the vertical spring can be reduced to a constant quasi-zero stiffness state through the negative stiffness mechanism of the double pairs of diagonal rods, while maintaining a high static stiffness to withstand the load). In particular, the constant quasi-zero stiffness can be adjusted as needed. Figure 9a and Figure 9b The dot-dash line in shows that the proposed isolator has the ability to have a constant quasi-zero stiffness.

[0044]

[0045]

[0046]

[0047]

[0048] The diagonal rod 7 and the transverse spring 15 generate vertical negative stiffness, which is called the double-pair diagonal rod negative stiffness mechanism. In parallel with the positive stiffness of the vertical spring 11, near the static equilibrium point (the static equilibrium point is where the upper and lower diagonal rods are in vertically symmetrical positions), according to the debugging method of formula (5), a constant quasi-zero stiffness characteristic can be obtained vertically.

[0049] Constant quasi-zero stiffness ( Figure 8 The debugging method (shown in the figure) is used to select a ratio α between the stiffness of the transverse spring 15 and the stiffness of the vertical spring 11, satisfying 0 < α < 0.25. Furthermore, the pre-compressed length δ2 of the lower pair of transverse springs in transverse spring 15 is equal to the horizontal length a between the two hinge points of the lower pair of diagonal rods 7 in the initial state. If these two conditions are met, a constant quasi-zero stiffness characteristic can be achieved.

[0050] The specific debugging methods are as follows:

[0051] S1. Based on the parameters of the quasi-zero stiffness characteristic, determine the initial precompression δ2 of the upper and lower transverse springs, the horizontal projection length a of the distance between the hinge points of the two diagonal rods, and the length of the vertical spring, so that δ2 = a in the initial state. The initial state refers to the state where the intersection of the two pairs of diagonal rods contacts the top of the free-length vertical spring.

[0052] S2. Set the stiffness of the two pairs of lateral springs from top to bottom in the constant quasi-zero stiffness vibration isolation structure to be k1 and k1 respectively, and the stiffness of the vertical spring to be k2. By determining the stiffness k1 of the lateral spring and the stiffness k2 of the vertical spring, the dimensionless parameter is constructed. Make the parameter α satisfy 0<α<0.25;

[0053] S3. After determining the above parameters, draw the force-displacement curve fx, where f is the applied force, i.e., the force applied to the load plate, and x is the displacement from the initial position. At this point, the force-displacement curve is an inclined straight line with a constant quasi-zero stiffness characteristic. Calculate the stiffness value K. Calculate the starting vibration isolation frequency based on the relationship between the vibration isolation mass m on the load plate. If the initial vibration isolation frequency does not meet the design requirements, repeat steps S1 to S3.

[0054] This invention ultimately demonstrates a vibration isolator with constant, quasi-zero stiffness characteristics, resolving the cubic nonlinearity inherent in conventional quasi-zero stiffness isolators. This design can be used for low-frequency vibration isolation under conditions of large excitation amplitudes and variable loads. While conventional cubic nonlinear stiffness isolators have only a single static equilibrium position, the constant, quasi-zero stiffness isolator of this invention possesses an infinite number of static equilibrium positions.

[0055] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, those skilled in the art may make various specific modifications based on the teachings of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A debugging method for a constant-value quasi-zero stiffness vibration isolation structure based on a negative stiffness mechanism of two pairs of oblique rods, characterized in that: The steps include: S1 sets a constant quasi-zero stiffness vibration isolation structure with two pairs of diagonal rod negative stiffness mechanisms, including a fixed plate, a bracket, a transverse guide rod, a diagonal rod, a diagonal rod hinge support, a support connection block, a vertical guide rod, a vertical spring, a hollow tube, a load plate and a transverse spring; brackets are symmetrically installed on both sides of the fixed plate, a vertical guide rod is installed in the middle of the fixed plate, a support connection block is installed on the upper part of the vertical guide rod, a vertical guide rod linear bearing connected to the vertical guide rod is installed on the support connection block; a vertical spring is installed on the vertical guide rod between the bottom of the support connection block and the fixed plate; The left and right ends of the support connecting block are connected to the oblique rod hinge support, and the oblique rod hinge support is a U-shaped structure; each of the brackets is provided with two circular through holes at equal intervals, a linear bearing is installed in each through hole through a retaining spring, a transverse guide rod is installed in each linear bearing, and each transverse guide rod is provided with a U-shaped groove at one end facing the vertical guide rod, a spring clamping plate is provided on the transverse guide rod next to the U-shaped groove, and a transverse spring is installed on each transverse guide rod between the spring clamping plate and the bracket; Two oblique rods are symmetrically arranged on both sides of the vertical guide rod, one end of the oblique rod is hinged to the U-shaped groove through the shaft rod, and the other end is hinged to the oblique rod hinge support; The support connection block is provided with connection holes on both sides, a hollow tube is provided on the connection hole, a load plate is provided on the top of the hollow tube, and the load plate is fixed to the connection hole by bolts passing through the hollow tube; S2. Based on the parameters of the quasi-zero stiffness characteristic, determine the initial precompression δ2 of the upper and lower transverse springs, the horizontal projection length a of the distance between the hinge points of the two diagonal rods, and the length of the vertical spring, so that δ2 = a in the initial state. The initial state refers to the state where the intersection of the two pairs of diagonal rods contacts the top of the free-length vertical spring. S3. Set the stiffness of the two pairs of lateral springs from top to bottom in the constant quasi-zero stiffness vibration isolation structure to be k1, and the stiffness of the vertical spring to be k2. By determining the stiffness k1 of the lateral spring and the stiffness k2 of the vertical spring, the dimensionless parameter is constructed. Make the parameter α satisfy 0<α<0.25; S4. After determining the above parameters, draw the force-displacement curve fx, where f is the applied force, i.e., the force applied to the load plate, and x is the displacement from the initial position. At this point, the force-displacement curve is an inclined straight line with a constant quasi-zero stiffness characteristic. Calculate the stiffness value K. Calculate the starting vibration isolation frequency based on the relationship between the vibration isolation mass m on the load plate. If the initial vibration isolation frequency does not meet the design requirements, repeat steps S1 to S3; Specifically: To analyze the structural parameter characteristics, the applied force f and its expression are subjected to dimensionless stiffening formula (1), and the dimensionless applied force is obtained. expression, find expression right The first derivative of , we get the dimensionless stiffness See formula (2); formula (3) is a parameter expression; at the static equilibrium position, for the dimensionless stiffness Calculate the first-order derivative and the second-order derivative respectively to obtain the parameter conditions of the zero stiffness characteristic, see formula (4); according to the debugging method of formula (5), obtain the constant value quasi-zero stiffness characteristic vertically; 。

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