Horizontal quasi-zero-stiffness vibration isolator

Abstract

The present invention discloses a horizontal quasi-zero stiffness vibration isolator, comprising: an inverted pendulum, including a swinging end and a fixed end, the swinging end is connected to a bearing platform by a spherical hinge, and the fixed end is connected to a fixed platform by a spherical hinge; the bearing platform is used to carry an instrument, and the fixed platform is connected to the ground or the fuselage of an aircraft or a submersible. Support rods, fixedly connected to the fixed platform, at least three of the support rods are centrally symmetrically distributed with the inverted pendulum as the axis, a first connecting beam is provided between two circumferentially adjacent support rods, and a second connecting beam is provided between the middle of each first connecting beam and the inverted pendulum. The inverted pendulum provides negative stiffness, and a beam group composed of at least three groups of first connecting beams and second connecting beams provides positive stiffness. The beam group composed of the first connecting beam and the second connecting beam realizes zero-frequency vibration isolation in the horizontal full-circle direction of the load, with relatively small additional damping, meeting the horizontal vibration isolation requirements of high-precision equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration damping devices, and particularly to a horizontal quasi-zero stiffness isolator. Background Art

[0002] Quasi-zero stiffness isolators usually achieve zero stiffness at the equilibrium position by using a negative stiffness structure in parallel with a positive stiffness structure. Therefore, the natural frequency of the overall structure approaches zero frequency, thereby achieving low-frequency and ultra-low-frequency vibration isolation. Equipment such as high-precision spacecraft and precision instruments all need to isolate vibrations of different frequencies from the outside world in the horizontal direction. In addition, the damping of the vibration isolation equipment should be low and should not affect the damping characteristics of the structure to be measured.

[0003] It is difficult to achieve zero-frequency vibration isolation in the horizontal full circumference direction of existing isolators, the load-bearing range is difficult to adjust, and the additional damping is large, which cannot meet the requirements of horizontal vibration isolation for high-precision equipment.

[0004] For example, Chinese Patent Document CN 111237372 A discloses an inverted pendulum type quasi-zero stiffness isolator that can isolate large-amplitude low-frequency vibrations. It realizes vibration isolation through an inverted pendulum that swings back and forth relative to the bottom plate and a reset mechanism installed on the bottom plate in front of and behind the inverted pendulum. The inverted pendulum installed upside down in this document has its vertical position as the equilibrium position. When excited, the inverted pendulum deviates from the equilibrium position and generates negative stiffness due to the action of its gravity; reset mechanisms are installed on both sides of the front and back of the inverted pendulum, and the torsion springs in the reset mechanisms provide a positive stiffness acting force for the inverted pendulum to return to the equilibrium position through the reset plate. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention discloses a horizontal quasi-zero stiffness isolator, which can achieve zero-frequency vibration isolation in the horizontal full circumference direction of the load, the load-bearing range can be adjusted, and the additional damping is small, meeting the requirements of horizontal vibration isolation for high-precision equipment.

[0006] The present invention achieves the invention purpose through the following technical solutions. A horizontal quasi-zero stiffness isolator, where the horizontal direction is the direction perpendicular to the gravity direction of the load, and includes:

[0007] An inverted pendulum, including a swinging end and a fixed end, the swinging end is connected to the bearing platform by a spherical hinge, and the fixed end is connected to the fixed platform by a spherical hinge;

[0008] Support rods, fixedly connected to the fixed platform, at least three of the support rods are centrally symmetrically distributed with the inverted pendulum as the axis, a first connecting beam is provided between two circumferentially adjacent support rods, and a second connecting beam is provided between the middle of each first connecting beam and the inverted pendulum;

[0009] Wherein, the connection point of the second connecting beam and the inverted pendulum divides the inverted pendulum into lengths of and The two sections are adjusted according to the magnitude of the load. and ratio.

[0010] In one embodiment, the axial direction of the support rod is parallel to the axial direction of the inverted pendulum; and the first connecting beam and the second connecting beam are perpendicular to the axial direction of the support rod.

[0011] In one embodiment, the second connecting beam is perpendicular to the first connecting beam.

[0012] In a preferred embodiment, the inverted pendulum includes a first section and a second section with coincident axes and connected end to end, where:

[0013] The first section includes a first head end and a first tail end. The first head end serves as the swinging end of the inverted pendulum and is connected to the bearing platform by a spherical hinge, and the first tail end is connected to the second section of the inverted pendulum;

[0014] The second section includes a second head end and a second tail end. The first head end is connected to the first section of the inverted pendulum, and the second tail end serves as the fixed end of the inverted pendulum and is connected to the first fixed platform by a spherical hinge.

[0015] In a preferred embodiment, the first section and the second section of the inverted pendulum are connected by a connecting member. The second section is fixedly connected to the connecting member, and the first section is threadedly connected to the connecting member. By changing the connection length of the threaded connection, the distance between the head end of the second section and the head end of the first section is changed;

[0016] wherein, the length of the second section is the , and the distance between the head end of the second section and the head end of the first section is the .

[0017] In a preferred embodiment, the second connecting beam is connected to the inverted pendulum through the connecting member.

[0018] In a preferred embodiment, the connecting member includes a plurality of fins. The plurality of fins are symmetrically arranged with respect to the axis center of the second section. Through holes with a horizontal axis are provided on the fins, and the through holes are used to connect with the second connecting beam.

[0019] In one embodiment, there are 4 support rods.

[0020] In one embodiment, the length of the first connecting beam is twice the length of the second connecting beam, and the second connecting beam is connected to the midpoint of the first connecting beam.

[0021] In one embodiment, according to , determine the The ratio with ;

[0022] wherein, is the Young's modulus of the first connecting beam, is the moment of inertia of the first connecting beam about the vertical direction, is the length of the second connecting beam, is the mass of the load, .

[0023] The horizontally quasi-zero stiffness isolator disclosed by the present invention, the horizontal direction is the direction perpendicular to the gravity direction of the load, and the horizontally quasi-zero stiffness isolator includes: an inverted pendulum, including a swing end and a fixed end, the swing end is connected to the bearing platform by a spherical hinge, and the fixed end is connected to the fixed platform by a spherical hinge; the bearing platform is used to carry the instrument, and the fixed platform is connected to the foundation or the fuselage of the aircraft or submersible. Support rods, fixedly connected to the fixed platform, at least three of the support rods are centrosymmetrically distributed with the inverted pendulum as the axis, and a first connecting beam is arranged between two circumferentially adjacent support rods, and a second connecting beam is arranged between the middle of each first connecting beam and the inverted pendulum. The inverted pendulum provides negative stiffness, and the beam group composed of at least three groups of first connecting beams and second connecting beams provides positive stiffness. When satisfying , a horizontally quasi-zero stiffness isolator is obtained, wherein, is the Young's modulus of the first connecting beam, is the moment of inertia of the first connecting beam about the vertical direction, is the length of the second connecting beam, is the mass of the load, is the length of the inverted pendulum. The beam group composed of the first connecting beam and the second connecting beam realizes zero-frequency vibration isolation in the horizontal full circumferential direction of the load, and the additional damping is small, meeting the horizontal vibration isolation requirements of high-precision equipment.

[0024] Further, the connection point of the second connecting beam and the inverted pendulum divides the inverted pendulum into two segments with lengths of and , and the ratio of to is adjusted according to the magnitude of the load, so as to realize the adjustable load range. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the overall structural schematic diagram of the horizontally quasi-zero stiffness isolator provided by the present invention;

[0026] Figure 2 is the overall structural schematic diagram of the horizontally quasi-zero stiffness isolator from another perspective provided by the present invention;

[0027] Figure 3 is the partial structural schematic diagram of the horizontally quasi-zero stiffness isolator provided by the present invention;

[0028] Figure 4 Another structural schematic diagram of the horizontal quasi-zero stiffness isolator provided by the present invention;

[0029] Figure 5 、 Figure 6 and Figure 7 Mechanical analysis diagrams of the horizontal quasi-zero stiffness isolator provided by the present invention. Specific embodiments

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. The principles and features of the present invention will be described below with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0031] Embodiment 1

[0032] Equipment such as high-precision spacecraft and precision instruments need to isolate vibrations of different frequencies from the outside in the horizontal direction. The horizontal quasi-zero stiffness isolator provided in this embodiment can isolate vibrations in a direction perpendicular to the gravity direction of the load, ensuring a stable working environment for important instruments or structures such as high-precision spacecraft, precision instruments, or submersibles.

[0033] Wherein the horizontal direction refers to the direction perpendicular to the gravity direction of the load.

[0034] Specifically, referring to Figure 1 and Figure 2 , the horizontal quasi-zero stiffness isolator includes:

[0035] An inverted pendulum 1, including a swinging end and a fixed end, the swinging end is connected to the bearing platform 2 by a spherical hinge, and the fixed end is connected to the fixed platform 3 by a spherical hinge;

[0036] A support rod 4, fixedly connected to the fixed platform 3 through an angle piece, at least three support rods 4 are symmetrically distributed around the inverted pendulum 1 as the axis, and a first connecting beam 5 is provided between two circumferentially adjacent support rods 4, and a second connecting beam 6 is provided between the middle of each first connecting beam 5 and the inverted pendulum 1;

[0037] Among them, the connection point of the second connecting beam 6 and the inverted pendulum 1 divides the inverted pendulum 1 into two segments with lengths of and , and the ratio of to is adjusted according to the size of the load.

[0038] The bearing platform 2 of the horizontal quasi-zero stiffness isolator provided in this embodiment is used to carry the instrument, and the fixed platform 3 is connected to the foundation or the body of the aircraft or submersible. Specifically, in combination with Figure 2, a plurality of load connection holes 201 are provided on the bearing platform 2 for connecting with instruments or structures that need vibration isolation; anchor bolt holes for connecting with the foundation or the airframe of an aircraft or a submersible are provided on the fixed platform 3.

[0039] In this embodiment, the swing end is connected to the bearing platform 2 by a spherical hinge, and the fixed end is connected to the fixed platform 3 by a spherical hinge; the spherical hinge connection is preferably realized by a rod-end spherical bearing. Combining with Figure 4 , specifically, an upper groove 202 is provided on the lower surface of the bearing platform 2, and a spherical socket structure 701 for connecting and arranging a rod-end spherical bearing is connected in the upper groove 202, and the rod body 702 of the rod-end spherical bearing is connected to the swing end of the inverted pendulum 1; similarly, a lower groove 301 is provided on the upper surface of the fixed platform 3, and a spherical socket structure 701 for connecting and arranging a rod-end spherical bearing is connected in the lower groove 301, and the rod body 702 of the rod-end spherical bearing is connected to the fixed end of the inverted pendulum 1.

[0040] In the horizontal quasi-zero stiffness isolator provided in this embodiment, the inverted pendulum 1 provides negative stiffness, and a beam group composed of at least three groups of first connecting beams 5 and second connecting beams 6 provides positive stiffness. When is satisfied, a horizontal quasi-zero stiffness isolator is obtained, where, is the Young's modulus of the first connecting beam, is the moment of inertia of the first connecting beam about the vertical direction, is the length of the second connecting beam, is the mass of the load, is the length of the inverted pendulum.

[0041] The beam group composed of the first connecting beam and the second connecting beam realizes zero-frequency vibration isolation in the horizontal full-circle direction of the load, with relatively small additional damping, meeting the horizontal vibration isolation requirements of high-precision equipment.

[0042] Further, in this embodiment, the connection point of the second connecting beam and the inverted pendulum divides the inverted pendulum 1 into two segments with lengths of and , and the ratio of to can be adjusted according to the magnitude of the load, so as to realize the adjustable load-bearing range.

[0043] The following gives a structural implementation manner of the inverted pendulum 1 to realize the adjustment of the ratio of to according to the magnitude of the load. On the basis of Figure 1 and Figure 2 , combining with Figure 3 , the inverted pendulum 1 includes a first segment 101 and a second segment 102 that are coaxially aligned and connected end to end. Among them,

[0044] The first section 101 includes a first head end and a first tail end. The first head end serves as the swinging end of the inverted pendulum 1 and is connected to the carrier 2 by a spherical hinge. The first tail end is connected to the second section 102 of the inverted pendulum 1.

[0045] The second section 102 includes a second head end and a second tail end. The first head end is connected to the first section of the inverted pendulum 1, and the second tail end serves as the fixed end of the inverted pendulum 1 and is connected to the fixed platform 3 by a spherical hinge.

[0046] This embodiment also provides a specific implementation manner of the connection structure between the first section 101 and the second section 102 connected end to end: The first section 101 and the second section 102 of the inverted pendulum 1 are connected by a connecting member 103. The second section 102 is fixedly connected to the connecting member 103, and the first section 101 is threadedly connected to the connecting member 103. By changing the connection length of the threaded connection, the distance between the head end of the second section 102 and the head end of the first section 101 is changed. In this embodiment, the length of the second section 102 is the , and the distance between the head end of the second section 102 and the head end of the first section 101 is the , then by adjusting the purpose of adjusting the ratio of to can be achieved, so as to adapt to instruments or structures of different weights and achieve quasi-zero stiffness vibration isolation for them.

[0047] The above specific implementation manner is only a preferred structural form of the inverted pendulum that can adjust the ratio of to provided by this application. In other embodiments, the ratio of to can be changed by adjusting the length of the second section 102, or the ratio of to can be changed by adjusting the lengths of the first section 101 and the second section 102.

[0048] In the preferred structural form, the second connecting beam 6 is connected to the inverted pendulum 1 through the connecting member 103, thereby simplifying the overall structure of the horizontal quasi-zero stiffness vibration isolator. Under such an inventive concept, this application provides a specific implementation manner of the connecting member 103:

[0049] The connecting member 103 includes a plurality of fins 1031. The plurality of fins 1031 are symmetrically arranged with respect to the axis center of the second section 102. Through holes 1033 with a horizontal axis are provided on the fins 1031, and the through holes 1033 are used to connect with the second connecting beam 6.

[0050] In a more simplified implementation, an internal threaded hole 1032 is provided at the upper end of the connecting member 103, and the internal threaded hole 1032 and the external thread on the first tail end of the first section 101 form a threaded connection.

[0051] In the attached drawings of the specification of this application, a structural form of a horizontal quasi-zero stiffness vibration isolator with 4 groups of beam groups composed of the first connecting beam 5 and the second connecting beam 6 is given. In fact, setting 3 groups of the beam groups can achieve a full circumferential enclosure of the inverted pendulum 1, thereby achieving full circumferential vibration isolation in the horizontal direction. If 5 groups, 6 groups or more groups of the beam groups are set, the vibration isolation effect in each horizontal direction can also be achieved.

[0052] In one implementation, the axial direction of the support rod 4 is parallel to the axial direction of the inverted pendulum 1; and the first connecting beam 5 and the second connecting beam 6 are perpendicular to the axis of the support rod 4. The second connecting beam 6 is perpendicular to the first connecting beam 5. There are 4 support rods. The length of the first connecting beam 5 is twice the length of the second connecting beam 6, and the second connecting beam 6 is connected to the midpoint of the first connecting beam 5. Under the above structural parameters, analyze the mechanical equation of the horizontal vibration isolator provided in this embodiment as follows:

[0053] Refer to Figure 5 The mechanical analysis diagram of the horizontal quasi-zero stiffness vibration isolator shown.

[0054] The horizontal quasi-zero stiffness structure, the principle of which is as Figure 5 shown: The rigid inverted pendulum 1 composed of the first section 101 and the second section 102 provides negative stiffness, and 4 groups of the beam groups provide positive stiffness. The total length of the first section 101 and the second section 102 is , there is a spherical hinge at each of the swinging end and the fixed end of the inverted pendulum 1, which can make the inverted pendulum 1 rotate freely in the horizontal direction to form an inverted pendulum. The beam length of the second connecting beam 6 is , the beam length of the first connecting beam 5 is . The mass of the instrument or structure to be vibration isolated is , that is, the inverted pendulum 1 is subjected to the vertical gravity mg, and the horizontal external force causing vibration is .

[0055] Perform a force analysis on the 4 groups of the beam groups:

[0056] Due to symmetry, as Figure 6 shown, take two adjacent groups of the beam groups for analysis. When subjected to a disturbance displacement in the X direction, the force of the structure can be analyzed in 2 parts:

[0057] Part1 can be regarded as a simply supported beam with both ends fixed and axially disturbed at the mid-span. Considering the bending strain and axial strain of part1, its force is

[0058]

[0059] Part 2 can be regarded as half of an H-beam. According to the Rayleigh-Ritz method, the mid-span force-displacement curve of the H-beam containing cubic terms under lateral perturbations can be derived:

[0060]

[0061] In the formula,

[0062] ,

[0063] .

[0064] Among them, is the Young's modulus of the first connecting beam, is the moment of inertia of the first connecting beam about the vertical direction (i.e., the Z-axis in Figure 5 and Figure 6 ), is the mass of the load, is the cross-sectional area of the first connecting beam, is the thickness of the first connecting beam.

[0065] Therefore, the force on part 2 is

[0066]

[0067] Among them, , that is, . After substituting, the forces on two adjacent beam groups under perturbations can be obtained, and the expression is

[0068]

[0069] The complete beam group is fixed at position B in Figure 6 and Figure 7 . Considering the displacement relationship of different points on the inverted pendulum as shown in Figure 7 , let the total length of the inverted pendulum be , , then there is , . Therefore, the force -displacement curve of the four beam groups on the top point A can be obtained:

[0070]

[0071] The inverted pendulum system composed of the first rod and the second rod is a typical horizontally negatively stiff system. Assuming that the mass of the vibration-isolated object carried is , the relational expression between the force and the disturbance displacement is as follows:

[0072]

[0073] For the overall combined structure of the inverted pendulum and the beam group, the relational expression between the force and the disturbance displacement is as follows:

[0074]

[0075] When the coefficient of the first-order term satisfies:

[0076]

[0077] a horizontal quasi-zero stiffness isolator can be obtained. According to this formula, it can be obtained that when changing the lengths of the first and second segments of the inverted pendulum to change the proportionality coefficient horizontal quasi-zero stiffness isolation can be achieved for objects with different load masses, and the isolator thus has a certain adjustable load range.

[0078] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0079] In the present invention, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0080] In the present invention, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Further, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the horizontal height of the first feature is less than that of the second feature.

[0081] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0082] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A horizontal quasi-zero stiffness vibration isolator, where the horizontal direction is perpendicular to the gravity direction of the load, and is characterized in that, Comprising: An inverted pendulum, including a swinging end and a fixed end, the swinging end is connected to the carrier table by a spherical hinge, and the fixed end is connected to the fixed table by a spherical hinge; Support rods, fixedly connected to the fixed table, at least three of the support rods are centrally symmetrically distributed with the inverted pendulum as the axis, and a first connecting beam is provided between two circumferentially adjacent support rods, and a second connecting beam is provided between the middle of each first connecting beam and the inverted pendulum; Among them, the connection point between the second connecting beam and the inverted pendulum divides the inverted pendulum into two segments with lengths of and , and adjusts the ratio of to according to the magnitude of the load; Wherein, the first connecting beam is fixedly connected between the support rod and the fixed table; The axial direction of the support rod is parallel to the axial direction of the inverted pendulum; and the first connecting beam and the second connecting beam are perpendicular to the axis of the support rod; The second connecting beam is perpendicular to the first connecting beam; The length of the first connecting beam is twice the length of the second connecting beam, and the second connecting beam is connected to the midpoint of the first connecting beam; According to , determine the ratio of the to ; Among them, is the Young's modulus of the first connecting beam, is the moment of inertia of the first connecting beam about the vertical direction, is the length of the second connecting beam, is the mass of the load, , , where g is the acceleration due to gravity; The inverted pendulum includes a first section and a second section with coincident axes and connected end to end, wherein: The first section includes a first head end and a first tail end, the first head end serves as the swinging end of the inverted pendulum and is connected to the carrier table by a spherical hinge, and the first tail end is connected to the second section of the inverted pendulum; The second section includes a second head end and a second tail end, the first head end is connected to the first section of the inverted pendulum, and the second tail end serves as the fixed end of the inverted pendulum and is connected to the fixed table by a spherical hinge; Among them, the length of the second section is the , and the distance between the leading end of the second section and the leading end of the first section is the .

2. The horizontal quasi-zero stiffness vibration isolator according to claim 1, wherein The first section and the second section of the inverted pendulum are connected by a connecting member, the second section is fixedly connected to the connecting member, and the first section is threadedly connected to the connecting member. By changing the connection length of the threaded connection, the distance between the head end of the second section and the head end of the first section is changed.

3. The horizontal quasi-zero stiffness vibration isolator according to claim 2, characterized in that, The second connecting beam is connected to the inverted pendulum through the connecting member.

4. The horizontal quasi-zero stiffness vibration isolator according to claim 3, wherein The connecting member includes a plurality of fins, the plurality of fins are symmetrically arranged with respect to the axis center of the second section, and through holes with a horizontal axis are provided on the fins, and the through holes are used to connect with the second connecting beam.

5. The horizontal quasi-zero stiffness vibration isolator according to claim 1, wherein There are 4 support rods.

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