Quasi-zero-stiffness air floatation low-frequency micro-vibration isolation structure and design method

Abstract

The invention discloses a quasi-zero-stiffness air floatation low-frequency micro-vibration isolation structure and a design method, and belongs to the technical field of vibration suppression and isolation. The quasi-zero-rigidity air floatation low-frequency micro-vibration isolation structure comprises a main air chamber, a top plate, a piston, a sleeve and a bottom plate, a micropore gas static pressure bearing is formed between the inner wall of the sleeve and the outer wall of the piston, the micropore gas static pressure bearing is inflated through a micropore throttler arranged on the piston, the bottom plate is arranged below the sleeve, and the bottom plate is arranged below the sleeve. An air static pressure thrust bearing is formed between the upper surface of the bottom plate and the bottom face of the sleeve and inflated through a connecting channel between the main air chamber and the expansion air chamber. According to the vibration isolator, the vibration isolator can bear large weight, meanwhile, approximate zero rigidity is kept so as to achieve efficient isolation of low-frequency vibration, the deflection problem between the piston and the sleeve of the air flotation vibration isolator is effectively solved, the working stability of the vibration isolator is remarkably improved, and a brand new technical path is provided for high-precision low-frequency vibration control.

Description

Technical Field

[0001] The invention relates to a vibration isolation structure and a design method thereof, in particular to a quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure and a design method thereof, and belongs to the technical field of vibration suppression and isolation. Background Art

[0002] As the requirements for vibration control in high-precision manufacturing, precision measurement, aerospace and other fields continue to increase, how to achieve efficient vibration isolation under large loads and low-frequency environments has become an important issue. Traditional vibration isolation methods usually use positive stiffness elements such as springs and rubber pads to provide support, supplemented by viscoelastic damping or other auxiliary structures to reduce the impact of external vibration on precision equipment. However, when the vibration isolation system cannot obtain a sufficiently low equivalent stiffness in this frequency band, the equipment will be significantly disturbed by low-frequency vibrations. If the support stiffness is simply reduced, the overall stability and load-bearing capacity of the system will be insufficient, making it difficult to balance accuracy and reliability.

[0003] In practical applications, mechanical vibration isolation devices often have mechanical contact. When the equipment is running for a long time or facing a large load, the uncertainty caused by friction and wear will inevitably weaken the stability and consistency of the vibration isolation performance. In special environments such as high cleanliness, vacuum or extreme temperature, lubrication and sealing problems will further increase the complexity of the system. Therefore, in order to overcome these problems, researchers have gradually turned to contactless vibration isolation technology to achieve "quasi-zero stiffness" and achieve a more stable and efficient low-frequency vibration isolation effect.

[0004] The concept of "quasi-zero stiffness" provides a feasible idea for reducing vibration transmission in the low-frequency range. Through clever structural design or the coupling of multiple elastic elements, the system can approximately present an extremely low force-displacement slope within a specific working range, thereby significantly improving the low-frequency vibration isolation efficiency. However, if such solutions need to meet higher load conditions or special use environments, they often face challenges such as complex structure, difficult debugging, and large size. In addition, traditional quasi-zero stiffness designs usually still rely on contact elements for support and guidance, which makes it difficult to completely eliminate friction and wear problems, and it is impossible to maintain long-term stable operation in a high-cleanliness environment.

[0005] In order to overcome the friction and wear caused by contact, air floating support technology has gradually attracted attention in the field of high-precision vibration isolation. By forming a stable high-pressure air film between the bearing surfaces, support and guidance can be provided without the need for substantial mechanical contact, and there is almost no friction and wear on the solid surface. This technology helps to maintain high cleanliness, reduce particulate contamination, and significantly improve the service life of the vibration isolator in a vacuum, dust-free or special environment. However, if air floating support is to be combined with the concept of quasi-zero stiffness to achieve a vibration isolation system that can handle large loads and has ultra-low stiffness characteristics, in-depth research is still needed in terms of structural design, mechanical distribution, and air film parameter control. In particular, how to maintain the stability and safety of the air floating bearing surface while reducing the equivalent stiffness of the system is still a key point that is difficult to take into account with existing technologies. Summary of the invention

[0006] The present invention improves upon the above-mentioned problems in the prior art and further proposes a quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure and design method, so that the isolator can maintain approximately zero stiffness while bearing a large weight to achieve efficient isolation of low-frequency vibrations.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure comprises a main air chamber, a top plate, a piston, a sleeve and a bottom plate, wherein the main air chamber is used to provide gas pressure support, the top plate is located above the main air chamber and is connected to the main air chamber, the piston is arranged in the main air chamber and can move up and down in the main air chamber, the sleeve is sleeved on the outside of the piston, a microporous gas static pressure bearing is formed between the inner wall of the sleeve and the outer wall of the piston, the microporous gas static pressure bearing is inflated through a microporous throttle arranged on the piston, the bottom plate is arranged below the sleeve, a gas static pressure thrust bearing is formed between the upper surface of the bottom plate and the bottom surface of the sleeve, and the gas static pressure thrust bearing is inflated through a connecting channel between the main air chamber and the expansion air chamber.

[0009] Furthermore, the vertical stiffness of the main air chamber is much smaller than the vertical stiffness of the gas static pressure thrust bearing, and the horizontal stiffness of the gas static pressure thrust bearing approaches zero.

[0010] Furthermore, the air film thickness of the microporous gas hydrostatic bearing is dynamically adjusted by the gas flow of the microporous throttle.

[0011] Furthermore, a support pin or a flexible hinge is provided between the top of the piston and the lower surface of the top plate.

[0012] Furthermore, the horizontal stiffness of the micro-vibration isolation structure is determined by the tilt force component of the support pin or the flexible hinge, and the horizontal stiffness approaches zero.

[0013] Furthermore, an exhaust hole is provided at the lower portion of the sleeve.

[0014] Furthermore, the volume of the expansion air chamber is 5 to 30 L, and is connected to the main air chamber through the connecting channel.

[0015] A design method for a quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure is implemented by the following steps:

[0016] S1: After determining the load mass of the vibration isolator, determine the stiffness of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure;

[0017] S2: Determine the effective action area of ​​the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure based on the stiffness obtained in S1;

[0018] S3: Design the outer wall size of the piston and the shape and size of the inner wall of the sleeve according to the effective action area determined in S2;

[0019] S4: Determine the aperture and quantity of the micropore restrictor according to the piston size obtained in S3;

[0020] S5: Determine the shape of the outer wall of the piston according to the aperture and number of the microporous restrictors obtained in S4;

[0021] S6: Calculate the stiffness range of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure under different expanded air chamber volumes according to the specific dimensions designed in S3-S5, and then calculate the natural frequency of the system. If it does not meet the use requirements, reduce the effective action area and redesign S2;

[0022] S7: After meeting the use requirements, design other external structures except the piston, sleeve and micro-pore throttle.

[0023] Furthermore, the method for determining the stiffness of the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure described in S1 is as follows:

[0024] k=4π 2 f 2 m (1)

[0025] In formula (1), f is the natural frequency of the vibration isolation structure, m is the load mass, and to achieve quasi-zero stiffness, f is generally set below 0.5 Hz.

[0026] Furthermore, the method for determining the effective action area described in S2 is as follows:

[0027]

[0028] In formula (2), V0 is the volume of the main gas chamber, T is the gas constant, and P atm is atmospheric pressure.

[0029] The beneficial effects of the present invention are:

[0030] 1. In the present invention, when the pressure of the main air chamber remains stable, the main air chamber, the gas static pressure thrust bearing and the microporous gas static pressure bearing cooperate with each other to make the horizontal and vertical stiffness of the micro-vibration isolation structure extremely small. Ideally, the structure has zero stiffness. The vibration isolator can maintain nearly zero stiffness while bearing a large weight to achieve efficient isolation of low-frequency vibration.

[0031] 2. The present invention effectively solves the problem of the deflection of the piston and sleeve of the air-floating vibration isolator, significantly improves the working stability of the vibration isolator, and provides a new technical path for high-precision low-frequency vibration control. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of an implementation mode of the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure of the present invention;

[0033] Figure 2 It is a structural schematic diagram of an implementation mode of the static pressure air bearing of the present invention;

[0034] Figure 3 It is a schematic cross-sectional structure diagram of an implementation mode of the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure of the present invention. DETAILED DESCRIPTION

[0035] In the description of the present invention, it should be noted that all directional indications (such as up, down, etc.) are based on the orientation or position relationship shown in the drawings, and are 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 cannot be understood as a limitation on the present invention.

[0036] Specific implementation method 1: Combination Figure 1-3 To illustrate this embodiment, Figure 1-3As shown, a quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure described in this embodiment includes a main air chamber 1, a top plate 2, a piston 3, a sleeve 4 and a bottom plate 5, wherein the main air chamber 1 is used to provide gas pressure support, the top plate 2 is located above the main air chamber 1 and is connected to the main air chamber 1, the piston 3 is arranged in the main air chamber 1, and can move up and down in the main air chamber 1, the sleeve 4 is sleeved on the outside of the piston 3, and a microporous gas static pressure bearing 6 is formed between the inner wall of the sleeve 4 and the outer wall of the piston 3, and the microporous gas static pressure bearing 6 is inflated through a microporous throttle 8 arranged on the piston 3, the bottom plate 5 is arranged below the sleeve 4, and a gas static pressure thrust bearing 7 is formed between the upper surface of the bottom plate 5 and the bottom surface of the sleeve 4, and the gas static pressure thrust bearing 7 is inflated through the connecting channel 10 between the main air chamber 1 and the expansion air chamber 9. Preferably, a support pin 11 or a flexible hinge is provided between the top of the piston 3 and the lower surface of the top plate 2, which is used to limit the horizontal displacement of the sleeve 4 and provide a horizontal restoring force through the tilting force component when the system deviates from the equilibrium position. The bottom plate 5, the top plate 2 and the sleeve 4 form a stable support structure. An exhaust hole 12 is provided at the lower part of the sleeve 4. The volume of the expansion air chamber 9 is 5 to 30L, and it is connected to the main air chamber 1 through the connecting channel 10 to adjust the dynamic response characteristics of the air pressure of the main air chamber 1. The micro-vibration isolation structure forms two static pressure air bearings, namely the microporous gas static pressure bearing 6 and the gas static pressure thrust bearing 7, between the inner wall of the sleeve 4 and the outer wall of the piston 3 and between the upper surface of the bottom plate 5 and the lower surface of the bottom plate 5 of the sleeve 4. The air film thickness of the microporous gas static pressure bearing 6 is dynamically adjusted by the gas flow of the microporous throttle 8. The microporous throttle 8 increases the stiffness of the microporous gas hydrostatic bearing 6 between the inner wall of the sleeve 4 and the outer wall of the piston 3, effectively solving the problem of deflection between the piston 3 and the sleeve 4. The micro-vibration isolation structure maintains approximately zero stiffness while bearing a large weight to achieve efficient isolation of low-frequency vibrations.

[0037] like Figure 2As shown, the two gas static pressure bearings each act as follows, so that the micro-vibration isolation structure presents extremely low stiffness in both the vertical and horizontal directions, thereby achieving efficient isolation of low-frequency vibrations. On the one hand, the microporous gas static pressure bearing 6 between the inner wall of the sleeve 4 and the outer wall of the piston 3 only exerts force on the piston 3 in the radial direction. Its specific function is to maintain the relative position between the sleeve 4 and the piston 3, so that the piston 3 can be suspended inside the sleeve 4 when the vibration isolator is in the working state, effectively avoiding the friction between the sleeve 4 and the piston 3. Therefore, the vertical stiffness and damping characteristics of the micro-vibration isolation structure will be completely determined by the main air chamber 1 in the piston 3. The working environment of the ultra-low frequency vibration isolator is a micro-vibration environment. When the air replenishment efficiency of the micro-vibration isolation structure is high enough, the gas buoyancy force exerted by the gas in the main air chamber 1 on the piston 3 is balanced with the gravity of the load, and the vertical stiffness of the micro-vibration isolation structure is infinitely close to zero, and the vibration interference of the ground is completely isolated and filtered out from the micro-vibration isolation structure.

[0038] On the other hand, the micro-vibration isolation structure forms the gas static pressure thrust bearing 7 between the upper surface of the base plate 5 and the lower surface of the base plate 5 of the sleeve 4. The gas static pressure thrust bearing 7 allows the sleeve 4 to float above the base plate 5, and the radial stiffness of the air film can be approximately ignored, which makes the radial stiffness of the micro-vibration isolation structure very small. In fact, the radial stiffness of the micro-vibration isolation structure is mainly caused by the tilting force component generated in the horizontal direction by the support pin 11 or the flexible hinge on the piston 3. Therefore, when the sleeve 4 and the piston 3 are near the working position, the horizontal stiffness of the micro-vibration isolation structure is approximately equivalent to zero stiffness, that is, the horizontal stiffness of the micro-vibration isolation structure is determined by the tilting force component of the support pin 11 or the flexible hinge, and the horizontal stiffness approaches zero. The vertical stiffness of the bottom air film is relatively large. Since it is connected in series with the main air chamber 1 in the micro-vibration isolation structure, and the stiffness of the main air chamber 1 is much smaller than that of the bottom air film, the vertical stiffness of the micro-vibration isolation structure can be approximately equivalent to the stiffness of the main air chamber 1. The vertical stiffness of the main air chamber 1 is much smaller than the vertical stiffness of the gas static pressure thrust bearing 7, and the horizontal stiffness of the gas static pressure thrust bearing 7 approaches zero.

[0039] A design method for a quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure is implemented by the following steps:

[0040] S1: After determining the load mass of the vibration isolator, determine the stiffness of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure;

[0041] S2: Determine the effective action area of ​​the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure based on the stiffness obtained in S1;

[0042] S3: Design the outer wall size of the piston 3 and the shape and size of the inner wall of the sleeve 4 according to the effective action area determined in S2;

[0043] S4: Determine the aperture and number of micropore restrictors 8 according to the size of the piston 3 obtained in S3;

[0044] S5: Determine the shape of the outer wall of the piston 3 according to the aperture and number of the microporous restrictor 8 obtained in S4;

[0045] S6: Calculate the stiffness range of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure under different expansion volumes of the air chamber 9 according to the specific dimensions designed in S3-S5, and then calculate the natural frequency of the system. If it does not meet the use requirements, reduce the effective action area and redesign S2;

[0046] S7: After the use requirements are met, other external structures except the piston 3, the sleeve 4 and the microporous throttle 8 are designed.

[0047] Specifically:

[0048] S1: Determine the load mass m of the vibration isolator, and determine the stiffness of the air-floating structure of the quasi-zero stiffness vibration isolator through formula (1).

[0049] k=4π 2 f 2 m (1)

[0050] In formula (1), f is the natural frequency of the vibration isolation system. In order to achieve quasi-zero stiffness, f is generally set below 0.5 Hz.

[0051] S2: According to the stiffness of the air spring and the formula (2), the effective area A of the air floating structure is determined. Figure 1 and Figure 2 Wherein is the outer circular area of ​​the piston 3 (or the inner wall cross-sectional area of ​​the sleeve 4).

[0052]

[0053] In formula (2), V0 is the volume of the air chamber of the air spring, which can be calculated according to the size of the auxiliary air chamber during the initial design. The volume of the auxiliary air chamber is generally between 5-30L, T is the gas constant, and P atm is atmospheric pressure.

[0054] S3: Design the outer wall size of the piston 3 and the shape and size of the inner wall of the sleeve 4 according to the determined air spring area.

[0055] S4: Determine the aperture and quantity of the micropore throttle 8 according to the size of the piston 3 .

[0056] S5: Determine the shape of the outer wall of the piston 3 according to the aperture and number of the micropore throttle 8.

[0057] S6: Calculate the stiffness range of the air spring under different expansion chamber 9 volumes according to the specific designed dimensions, and then calculate the natural frequency of the system to see whether it meets the use requirements. If not, further reduce the effective action area A of the air spring and redesign step 2.

[0058] S7: Finally, design the external structure, such as the bottom plate 5, the top plate 2, the support pin 11 (or the flexible hinge) and other matching structures.

[0059] Based on the quasi-zero stiffness vibration isolation theory, the present invention uses an air floating unit to support and guide the system. The air floating unit is a non-contact support structure, whose main function is to support the load and act as a passive system to isolate the interference of external environmental vibration on the load. A balance between large load capacity and extremely low stiffness is successfully achieved. By integrating core modules such as air chamber structure, thrust bearing structure, and microporous gas hydrostatic bearing 6 into the system, the vibration isolator can maintain near zero stiffness while bearing a large weight to achieve efficient isolation of low-frequency vibrations, effectively solving the problem of deflection between the piston 3 and the sleeve 4 of the air floating vibration isolator, significantly improving the working stability of the vibration isolator, and providing a new technical path for high-precision low-frequency vibration control.

[0060] Working principle:

[0061] When the gas hydrostatic bearing is working, the compressed gas enters the gap between the sleeve and the piston through the throttle, and quickly diffuses to the two ends of the shaft, forming an air film in the gap that can bear a certain load. The hydrostatic gas bearing generates a pressure difference by causing the thickness of the air film in the gap to change through the change of load, thereby obtaining stiffness. The designed vibration isolation structure is connected in series by the air spring and the bottom gas hydrostatic bearing in the vertical direction, so the vertical stiffness is equal to the stiffness of the two in series. Similarly, the horizontal direction is connected in series by the annular air film and the bottom air film, so the horizontal stiffness is equal to the stiffness of the two in series. The advantage of the designed structure is that the vertical stiffness of the air spring is much smaller than the stiffness of the bottom gas hydrostatic bearing, so the vertical stiffness is approximately equal to the stiffness of the air spring; the theoretical stiffness of the bottom air film in the horizontal direction is zero, which is much smaller than the horizontal stiffness of the annular air film, so the horizontal stiffness is theoretically zero.

[0062] Specifically, the microporous gas hydrostatic bearing only applies force to the piston in the radial direction, restricting its horizontal movement. In the vertical direction, the radial gas hydrostatic bearing avoids mechanical contact between the piston and the sleeve, allowing the piston to float inside the sleeve and move freely up and down. Since there is no friction between the piston and the inner wall of the sleeve, the vertical stiffness and damping characteristics of the system will be entirely determined by the main air chamber in the piston of the air spring. Ideally, if it is assumed that the system's air replenishment efficiency is extremely high, the air pressure change in the main air chamber caused by the movement of the piston can be ignored, that is, the air pressure value of the main air chamber remains constant. In this case, the air buoyancy force exerted by the gas in the main air chamber on the piston is balanced with the gravity of the load, the vertical stiffness of the system approaches zero infinitely, and the vibration interference of the ground is completely isolated and filtered out of the system.

[0063] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure, characterized in that: The invention comprises a main air chamber (1), a top plate (2), a piston (3), a sleeve (4) and a bottom plate (5), wherein the main air chamber (1) is used to provide gas pressure support, the top plate (2) is located above the main air chamber (1) and is connected to the main air chamber (1), the piston (3) is arranged in the main air chamber (1) and can move up and down in the main air chamber, the sleeve (4) is sleeved on the outside of the piston (3), a microporous gas static pressure bearing (6) is formed between the inner wall of the sleeve (4) and the outer wall of the piston (3), and the microporous gas static pressure bearing (6) is inflated through a microporous throttle (8) arranged on the piston (3), the bottom plate (5) is arranged below the sleeve (4), a gas static pressure thrust bearing (7) is formed between the upper surface of the bottom plate (5) and the bottom surface of the sleeve (4), and the gas static pressure thrust bearing (7) is inflated through a connecting channel (10) between the main air chamber (1) and the expansion air chamber (9).

2. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 1, characterized in that: The vertical stiffness of the main air chamber (1) is much smaller than the vertical stiffness of the gas static pressure thrust bearing (7), and the horizontal stiffness of the gas static pressure thrust bearing (7) approaches zero.

3. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 2, characterized in that: The gas film thickness of the microporous gas static pressure bearing (6) is dynamically adjusted by the gas flow rate of the microporous throttle (8).

4. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 1, characterized in that: A support pin (11) or a flexible hinge is provided between the top of the piston (3) and the lower surface of the top plate (2).

5. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 4, characterized in that: The horizontal rigidity of the structure is determined by the tilting force component of the support pin (11) or the flexible hinge, and the horizontal rigidity approaches zero.

6. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 1, characterized in that: An exhaust hole (12) is provided at the lower portion of the sleeve (4).

7. The quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 1, characterized in that: The volume of the expansion air chamber (9) is 5 to 30 L, and is connected to the main air chamber (1) through the connecting channel (10).

8. A design method for a quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to any one of claims 1 to 7, characterized in that: The design method is implemented by the following steps: S1: After determining the load mass of the vibration isolator, determine the stiffness of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure; S2: Determine the effective action area of ​​the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure based on the stiffness obtained in S1; S3: Design the outer wall size of the piston and the shape and size of the inner wall of the sleeve according to the effective action area determined in S2; S4: Determine the aperture and quantity of the micropore restrictor according to the piston size obtained in S3; S5: Determine the shape of the outer wall of the piston according to the aperture and number of the microporous restrictors obtained in S4; S6: Calculate the stiffness range of the quasi-zero stiffness air-floating low-frequency micro-vibration isolation structure under different expanded air chamber volumes according to the specific dimensions designed in S3-S5, and then calculate the natural frequency of the system. If it does not meet the use requirements, reduce the effective action area and redesign S2; S7: After meeting the use requirements, design other external structures except the piston, sleeve and micro-pore throttle.

9. The design method of a quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 8, characterized in that: The method for determining the stiffness of the quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure described in S1 is as follows: k=4π 2 F 2 m (1) In formula (1), f is the natural frequency of the vibration isolation structure, m is the load mass, and f is generally set below 0.5 Hz to achieve quasi-zero stiffness.

10. The design method of a quasi-zero stiffness air-floating low-frequency isolation micro-vibration structure according to claim 9, characterized in that: The method for determining the effective area described in S2 is as follows: In formula (2), V0 is the volume of the main gas chamber, T is the gas constant, and P atm is atmospheric pressure.

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