Electromagnetic quasi-zero stiffness vibration isolator and control method

Abstract

The application provides an electromagnetic quasi-zero stiffness vibration isolator and a control method, and belongs to the technical field of vibration isolation. The vibration isolator comprises a base, a positive stiffness mechanism, a negative stiffness mechanism, a positive-negative stiffness connecting mechanism and a dynamic control module. The positive stiffness mechanism adopts a hydraulic spring to provide basic positive stiffness. The negative stiffness mechanism comprises a plurality of stator units arranged in an annular array on the base and a mover suspended in the magnetic field center thereof, and is used for generating nonlinear negative stiffness. The top end of the hydraulic spring supports the load through a receiving table and keeps a preset gap with the inner wall of the mover. The positive-negative stiffness connecting mechanism realizes displacement transmission and collaborative adjustment of the two. The dynamic control module comprises a displacement sensor and a controller. The sensor collects displacement signals, the controller adjusts the excitation current of the stator unit according to the signals, and dynamically adjusts the electromagnetic force, so that the vibration isolator maintains a quasi-zero stiffness state. The application can maintain the quasi-zero stiffness state when the load changes, realize adaptive low-frequency vibration isolation of the load, and improve the stability and vibration isolation performance of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-frequency isolation, in particular to an electromagnetic quasi-zero stiffness vibration isolator and a control method. BACKGROUND

[0002] In various engineering applications, vibration is an important factor affecting the safety of structures and the stable operation of equipment. Vibration generally refers to the reciprocating motion of an object around a balance position. Depending on the application scenario, vibration may need to be utilized or must be suppressed. In practical engineering, most cases have negative effects of vibration, such as reducing the working accuracy of instruments and equipment, inducing noise, and even damaging structures. Therefore, vibration reduction and isolation have always been the focus of research in the field of vibration control.

[0003] In civil engineering and mechanical systems, in addition to general mechanical vibration, low-frequency and large-amplitude vibration caused by earthquakes is particularly harmful to building structures and internal equipment. The energy of an earthquake is mostly distributed in the 0.1-10Hz frequency band, and traditional linear vibration isolation bearings only have effective isolation performance when the excitation frequency is higher than the natural frequency of the system times, so they cannot function in the low-frequency band. To alleviate the contradiction between high static stiffness and low dynamic stiffness in linear vibration isolation, the industry proposes to use quasi-zero stiffness (QZS) design, which connects positive stiffness elements and negative stiffness elements in parallel to make the overall dynamic stiffness approach zero, thereby achieving better vibration isolation in the low-frequency domain.

[0004] Existing QZS vibration isolation devices are mostly passive structures that rely on fixed geometric and mechanical parameters to achieve quasi-zero stiffness characteristics. However, when external loads change significantly, the system operating point is easily deviated from the preset quasi-zero stiffness interval, resulting in a decrease in vibration isolation performance or even failure. This defect limits the reliability and adaptability of passive QZS bearings under actual variable load conditions.

[0005] Therefore, there is an urgent need for an electromagnetic quasi-zero stiffness vibration isolator and a control method that can maintain a quasi-zero stiffness state when the load changes to achieve load-adaptive low-frequency vibration isolation. SUMMARY

[0006] The purpose of the present application is to provide an electromagnetic quasi-zero stiffness vibration isolator and a control method, which aims to solve the technical problem of passive quasi-zero stiffness vibration isolation failure when the load changes.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides an electromagnetic quasi-zero stiffness vibration isolator, comprising:

[0008] a base;

[0009] a positive stiffness mechanism for supporting external loads and providing a basic positive stiffness, comprising a hydraulic spring arranged at the middle of the base;

[0010] a negative stiffness mechanism, connected in parallel with the positive stiffness mechanism, for generating a nonlinear negative stiffness to offset the positive stiffness, comprising a plurality of stator units distributed in a ring array on the base, and a mover suspended in the center of the magnetic field of the stator units; the top end of the hydraulic spring passes through the mover and is connected with a receiving platform, and a preset gap is maintained between the hydraulic spring and the inner wall of the mover;

[0011] a positive and negative stiffness connecting mechanism, arranged between the hydraulic spring and the mover, for realizing displacement transmission and cooperative adjustment;

[0012] a dynamic control module, comprising a displacement sensor arranged on the receiving platform and a controller electrically connected with the displacement sensor, the displacement sensor is used for collecting a load displacement signal, and the controller adjusts the excitation current of the stator unit according to the displacement signal to adjust the electromagnetic force so that the isolator is maintained in a quasi-zero stiffness interval.

[0013] As a further improvement of the above scheme, the stator unit comprises a stator support and an upper coil winding and a lower coil winding arranged from top to bottom on the stator support, and the upper and lower coil windings have a preset space therebetween;

[0014] opposite currents are passed through the upper coil winding and the lower coil winding of the stator unit, so as to form a magnetic field symmetrically distributed upward and downward in the area where the mover is located.

[0015] As a further improvement of the above scheme, a plurality of the stator units are uniformly arranged along the circumference of the mover to cooperatively form a multi-pole symmetric magnetic field array, so that the mover obtains a stable electromagnetic force gradient in the axial direction.

[0016] As a further improvement of the above scheme, the mover comprises a ring plate and a connecting pipe arranged on the upper surface of the ring plate, the outer edge of the ring plate extends into the preset space of the stator unit, and the electromagnetic force acting on the ring plate changes with the change of the air gap between the stator unit and the mover, thereby forming a negative stiffness characteristic.

[0017] As a further improvement of the above scheme, the positive and negative stiffness connecting mechanism comprises a plurality of pneumatic springs; the plurality of pneumatic springs are uniformly distributed around the hydraulic spring;

[0018] One end of each of the pneumatic springs is connected with the hydraulic spring, and the other end is connected with the top of the connecting pipe of the mover.

[0019] As a further improvement of the above scheme, the pneumatic spring is a nitrogen pressurized type, which forms an air chamber by pushing a pneumatic piston through a piston guide rod, and the pneumatic spring is provided with six and is distributed around the hydraulic spring.

[0020] As a further improvement of the above-mentioned scheme, the hydraulic spring comprises an elastic body chamber and a liquid flow channel, the elastic body chamber provides a positive restoring force increasing with displacement when the vibration isolator is subjected to load and displaced, and the liquid flows through the flow channel to generate damping effect.

[0021] As a further improvement of the above-mentioned scheme, the material of the mover is high-permeability silicon steel sheet, and the stress is determined by the magnetic field intensity of the stator unit and the air gap distance between the mover and the stator unit.

[0022] As a further improvement of the above-mentioned scheme, the stator support comprises a vertical plate and four horizontal plates arranged on the vertical plate from top to bottom, and the four horizontal plates form a first mounting space, the preset space and a second mounting space from top to bottom, the upper coil winding is arranged in the first mounting space, and the lower coil winding is arranged in the second mounting space.

[0023] In the second aspect, the application further provides a control method of the electromagnetic quasi-zero stiffness vibration isolator according to the first aspect, comprising the following steps:

[0024] An initial current is passed through the coil winding of each stator unit to build an upper and lower symmetrical magnetic field array, so that the mover is suspended at an initial air gap under the action of the magnetic field force;

[0025] The displacement sensor is used to collect the mover displacement signal caused by external load change or vibration excitation in real time;

[0026] The controller calculates the target current value required for the mover to return to the equilibrium position based on the displacement signal;

[0027] The driving circuit adjusts the current in each coil winding of the stator unit, changes the electromagnetic negative stiffness and positive stiffness in cooperation to compensate for the stiffness deviation caused by load change, and keeps the system in a quasi-zero stiffness state.

[0028] As a further improvement of the above-mentioned scheme, the controller uses H∞ control algorithm to calculate the required target current value, changes the magnetic field intensity and magnetic force gradient by adjusting the current, and realizes dynamic regulation and control of the nonlinear negative stiffness.

[0029] As a further improvement of the above-mentioned scheme, if the mover displacement is too large, the output increases the stator current instruction, and if the displacement is too small, the output reduces the current instruction, so as to dynamically adapt to different external loads.

[0030] Due to the above technical scheme, the application has the following beneficial effects:

[0031] This invention provides an electromagnetic quasi-zero stiffness vibration isolator. Through the parallel arrangement of a positive stiffness mechanism and an adjustable electromagnetic negative stiffness mechanism, combined with current closed-loop control based on displacement feedback, it can maintain a quasi-zero stiffness operating state under different loads. This not only improves the effectiveness and stability of low-frequency vibration isolation but also has the advantages of compact structure and wide applicability. Specifically, it is reflected in the following aspects:

[0032] The positive stiffness mechanism with the clearance between the hydraulic spring and the mover has a simple structure and strong load-bearing capacity. It can stably provide basic positive stiffness and ensure that the movement of the negative stiffness mechanism does not interfere with each other through the preset clearance with the inner wall of the mover, thus laying a reliable foundation for subsequent stiffness adjustment.

[0033] The negative stiffness mechanism, consisting of stator units arranged in a ring array and a suspended mover, utilizes electromagnetic force to generate non-contact, nonlinear negative stiffness. Because there is no mechanical contact, friction loss and operating energy consumption are reduced, extending service life. The nonlinear characteristics of the electromagnetic force can extend the quasi-zero stiffness range within a certain displacement range, improving the ability to suppress low-frequency vibrations.

[0034] The positive and negative stiffness connection mechanism realizes the synchronous coordination of the positive and negative stiffness mechanisms in displacement, ensuring that the two can work effectively in coupling when the load or external excitation causes displacement changes, maintaining the ideal state of overall stiffness close to zero.

[0035] A dynamic control module, consisting of a displacement sensor and a controller located on the receiving platform, can detect the load displacement in real time and adjust the excitation current of the stator unit accordingly, thereby precisely controlling the magnitude of the electromagnetic force. This closed-loop control method allows the vibration isolator to continuously and quickly correct its negative stiffness value according to the actual load conditions, achieving load-adaptive stiffness matching and avoiding vibration isolation failure caused by load changes.

[0036] The combination of positive stiffness provided by hydraulic springs and negative stiffness adjustable by electromagnetic force allows the vibration isolator to cope with different load conditions without the need to replace or disassemble the structure. It is easy to operate and has a wide range of applications. While taking into account high load-bearing capacity, it solves the contradiction between low-frequency vibration isolation performance and load-bearing capacity in traditional vibration isolators. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0038] Figure 1 This is a front view schematic diagram of an electromagnetic quasi-zero stiffness vibration isolator disclosed in this invention;

[0039] Figure 2 This is a three-dimensional schematic diagram of an electromagnetic quasi-zero stiffness vibration isolator disclosed in this invention;

[0040] Figure 3 for Figure 2 CC cross-sectional view;

[0041] Figure 4 This is a three-dimensional schematic diagram of the mover suspending at the center of the magnetic field of each stator unit, as disclosed in this invention.

[0042] Figure 5 This is a three-dimensional schematic diagram of the hydraulic spring, the mover, and the connection of each pneumatic spring disclosed in this invention.

[0043] Figure 6 This is a three-dimensional schematic diagram of the connection between the hydraulic spring and each pneumatic spring disclosed in this invention.

[0044] Figure 7 This is a three-dimensional schematic diagram of the stator unit disclosed in this invention;

[0045] Figure 8 This is a cross-sectional schematic diagram of the stator support disclosed in this invention;

[0046] Figure 9 This is a three-dimensional schematic diagram of the coil winding disclosed in this invention;

[0047] Figure 10 This is a perspective three-dimensional schematic diagram of the pneumatic spring disclosed in this invention;

[0048] Figure 11 This is a flowchart illustrating a control method for an electromagnetic quasi-zero stiffness vibration isolator disclosed in this invention.

[0049] Figure label:

[0050] 1. Base; 2. Hydraulic spring; 3. Stator unit; 31. Stator support; 311. Vertical plate; 312. Horizontal plate; 32. Upper coil winding; 33. Lower coil winding; 34. Preset space; 35. First installation space; 36. Second installation space; 4. Mover; 41. Annular plate; 42. Connecting pipe; 5. Displacement sensor; 6. Pneumatic spring; 7. Support platform; 8. Upper connecting seat; 9. Lower connecting seat.

[0051] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0054] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0055] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0056] Example 1

[0057] See Figures 1-10 The present invention provides an electromagnetic quasi-zero stiffness vibration isolator, including a base 1, a positive stiffness mechanism, a negative stiffness mechanism, a positive and negative stiffness connection mechanism, and a dynamic control module. The components are arranged and cooperated in the following manner to achieve quasi-zero stiffness maintenance and low-frequency vibration isolation under load changes.

[0058] Base 1 serves as the supporting base for the overall structure.

[0059] The positive stiffness mechanism includes a hydraulic spring 2, the bottom of which is fixed to the middle of the base 1 via a lower connecting seat 9, and the top extends upward and passes through the mover 4, connected to a receiving platform 7 via an upper connecting seat 8. The hydraulic spring 2 generates linear positive stiffness when subjected to external loads, providing stable foundation support for the vibration isolator. Placing the hydraulic spring 2 in the middle of the base 1 facilitates uniform load distribution and improves load-bearing capacity. A preset gap is provided between the hydraulic spring 2 and the inner wall of the mover 4, avoiding direct contact and frictional loss while ensuring free movement of the mover 4 within a controlled displacement range. This gap design, combined with the load-bearing characteristics of the hydraulic spring 2, ensures the stability of the positive stiffness mechanism during operation and provides space for the non-contact arrangement of the negative stiffness mechanism; the receiving platform 7 is used to mount the load.

[0060] The negative stiffness mechanism, arranged in parallel with the positive stiffness mechanism, includes multiple stator units 3 and a mover 4. The stator units 3 are arranged in a ring array along the circumference of the base 1. The mover 4 is located at the center of the magnetic field of the stator units 3 and is suspended in the magnetic field, independent of mechanical support. By applying an excitation current to the stator units 3, a controllable electromagnetic force can be generated on the mover 4. This electromagnetic force changes non-linearly with displacement, thus forming a non-linear negative stiffness to counteract the positive stiffness of the hydraulic spring 2. The advantage of using electromagnetic force to achieve negative stiffness is that the non-contact electromagnetic action reduces mechanical wear and energy loss, improving reliability and lifespan.

[0061] The positive and negative stiffness connection mechanism is located between the hydraulic spring 2 and the mover 4. Its function is to transmit the displacement changes generated by the positive stiffness mechanism to the negative stiffness mechanism and realize the coordinated action and adjustment of the two. This mechanism ensures that when the load or external excitation causes displacement changes, the mover 4 and the top of the hydraulic spring 2 respond synchronously, so that the positive and negative stiffness are always coordinated and matched during the dynamic process, and together maintain the overall stiffness close to zero.

[0062] The dynamic control module includes a displacement sensor 5 and a controller. The displacement sensor 5 is fixed to the support platform 7 and directly senses the load displacement signal, enabling timely reflection of changes in the isolator's operating state. The controller is electrically connected to the displacement sensor 5. After receiving the displacement signal, it adjusts the excitation current of each stator unit 3 according to a preset control strategy, thereby changing the magnitude of the electromagnetic force and ensuring real-time matching of negative and positive stiffness. This ensures the isolator operates within the quasi-zero stiffness range under different load conditions. This closed-loop control method overcomes the defect of passive quasi-zero stiffness isolators that easily deviate from the optimal vibration isolation state under load changes, achieving load-adaptive stiffness adjustment and possessing the advantages of fast response speed and high adjustment accuracy.

[0063] With this configuration, the vibration isolator can continuously adjust the electromagnetic force based on displacement feedback through a dynamic control module when subjected to different loads. This allows the negative stiffness to offset the positive stiffness within a certain displacement range, thus maintaining a quasi-zero stiffness operating state even under load variations. This not only solves the problem of vibration isolation failure caused by load changes in traditional passive vibration isolators, but also reduces friction and energy consumption by adopting a non-contact electromagnetic negative stiffness mechanism. Furthermore, it utilizes the nonlinearity of electromagnetic force to broaden the quasi-zero stiffness range, balancing low-frequency vibration isolation performance with load-bearing capacity. The structure is compact, easy to adjust, and suitable for various applications requiring low-frequency vibration isolation and subject to varying loads.

[0064] In a preferred embodiment, the stator unit 3 in the negative stiffness mechanism includes a stator support 31, and an upper coil winding 32 and a lower coil winding 33 arranged sequentially from top to bottom on the stator support 31. There is a preset spatial interval between the upper coil winding 32 and the lower coil winding 33. The spatial interval is used to arrange the mover 4 and ensure that it can levitate and displace freely in the magnetic field.

[0065] Specifically, the stator support 31 is typically made of a metallic material with good magnetic permeability (e.g., high-permeability steel sheet) to enhance magnetic field conduction efficiency. The upper coil winding 32 and the lower coil winding 33 are wound on the stator support 31 respectively, with opposite energizing directions. That is, the end of the upper coil winding 32 facing the mover 4 forms the north pole, and the end of the lower coil winding 33 facing the mover 4 forms the south pole, or vice versa, thereby forming a symmetrically distributed magnetic field array in the region where the mover 4 is located.

[0066] By passing currents in opposite directions through the upper and lower coils, a symmetrical and controllable magnetic field distribution can be formed around the mover 4. This magnetic field interacts with the high-permeability mover 4 (such as a mover 4 made of ferromagnetic material), subjecting it to a displacement-related magnetic attraction. When the mover 4 undergoes vertical displacement due to external excitation or load changes, the air gap between it and the magnetic poles changes, causing a change in the magnetic gradient and resulting in a nonlinear negative stiffness characteristic of "increased displacement and decreased restoring force." This negative stiffness characteristic is key to counteracting positive stiffness and achieving a quasi-zero stiffness state, thus contributing to improved low-frequency vibration isolation performance.

[0067] The reserved space 34 between the upper coil winding 32 and the lower coil winding 33 provides sufficient space for the levitation and movement of the mover 4, avoiding structural interference, and also leaving room for design optimization of magnetic field distribution and adjustment of control strategy.

[0068] This stator unit 3 structure provides a structural basis for subsequent adjustment of the current magnitude of the upper coil winding 32 and the lower coil winding 33 via a dynamic control module (such as an H∞ controller). When the displacement sensor 5 detects a change in load or displacement of the mover 4, the controller can adjust the input current of the upper and lower coils in real time according to the deviation, thereby changing the magnetic field strength and magnetic gradient, dynamically adjusting the magnitude of the negative stiffness, and enabling the system to quickly return to the quasi-zero stiffness equilibrium position, effectively coping with vibration isolation performance fluctuations caused by load changes or external excitation.

[0069] This embodiment constructs a symmetrical and controllable magnetic field environment by configuring the stator unit 3 to include upper and lower coil windings 33 with a preset interval and passing currents in opposite directions through the two coils. This provides the mover 4 with nonlinear negative stiffness related to displacement, which is an important structural basis for realizing load-adaptive quasi-zero stiffness vibration isolation. This design is not only structurally reasonable and easy to control, but also works in conjunction with other components in the system (such as the mover 4, hydraulic spring 2, pneumatic spring 6, and controller) to jointly improve the stability and low-frequency vibration isolation capability of the vibration isolator under varying load conditions.

[0070] In a preferred embodiment, multiple stator units 3 are uniformly arranged around the mover 4 to form a multi-pole symmetrical magnetic field array, so that the mover 4 obtains a stable electromagnetic force gradient in the axial direction.

[0071] Specifically, each stator unit 3 includes a stator support 31 and an upper coil winding 32 and a lower coil winding 33 arranged from top to bottom on the stator support 31. A predetermined space 34 exists between the upper coil winding 32 and the lower coil winding 33, and currents in opposite directions are passed through them, thereby forming a symmetrical magnetic field in the region where the mover 4 is located. Multiple such stator units 3 are evenly arranged around the mover 4 in a circumferential pattern, for example, but not limited to, a ring array. In a typical embodiment, there can be 12 stator units 3, collectively forming a multi-pole symmetrical magnetic field array.

[0072] This invention arranges multiple stator units 3 uniformly around the mover 4, with the magnetic fields generated by each stator unit 3 superimposed and coordinated in space to form a symmetrical and uniformly distributed multi-pole magnetic field environment. In this magnetic field, the mover 4 is located in the central region and is subjected to the magnetic forces from each stator unit 3, resulting in a stable and continuous electromagnetic force gradient in the axial direction. This electromagnetic force gradient is the basis for achieving the nonlinear negative stiffness characteristic of "increased displacement, decreased restoring force," helping the mover 4 to receive a displacement-related restoring force when subjected to vertical disturbances, thereby canceling out the positive stiffness and maintaining a quasi-zero stiffness state.

[0073] The uniformly arranged stator units 3 ensure the consistency and symmetry of the magnetic field around the mover 4, avoiding uneven force distribution caused by excessively strong or weak local magnetic fields and improving the uniformity of electromagnetic force distribution. This uniform magnetic field environment makes the electromagnetic force change of the mover 4 during axial displacement more stable and predictable. This helps the controller (such as the H∞ controller) to accurately adjust the current of each stator unit 3 based on the feedback signal of the displacement sensor 5, achieve precise control of negative stiffness, and improve the reliability and stability of the overall vibration isolation effect.

[0074] In a preferred embodiment, the mover 4 includes an annular plate 41 and a connecting pipe 42 disposed on the upper surface of the annular plate 41. The outer edge of the annular plate 41 extends into the preset space 34 of each stator unit 3, so that it is within the range of the magnetic field generated by the multiple stator units 3. Thus, when the mover 4 is displaced, the air gap between its outer edge and the stator unit 3 changes, causing the electromagnetic force it receives to change accordingly, forming a nonlinear negative stiffness characteristic.

[0075] Specifically, the annular plate 41 of the mover 4 is typically made of a high-permeability material (e.g., high-permeability steel sheet) to ensure good magnetic response characteristics. The annular plate 41, as the main magnetized component of the mover 4, is spatially arranged opposite to the stator unit 3. The outer edge of the annular plate 41 extends into the internal space (i.e., the preset space 34) formed by multiple stator units 3. The preset space 34 provides the mover 4 with an area allowing it to float up and down, while ensuring a reasonable initial air gap between the mover 4 and the stator.

[0076] The connecting pipe 42 provided on the upper surface of the mover 4 is used to realize the mechanical connection between the mover 4 and other functional components such as the pneumatic spring 6 and the hydraulic spring 2. For example, the connecting pipe 42 is connected to the upper connecting seat 8 of the pneumatic spring 6 by fixing bolts, so that the mover 4, the hydraulic spring 2 and the pneumatic spring 6 form an integrated mechanical-electromagnetic system.

[0077] When external excitation (such as load changes or low-frequency vibrations) causes axial displacement of the mover 4, the air gap between the annular plate 41 and the stator unit 3 changes accordingly. Since a reverse current flows through the coil winding 32 on the stator unit 3, a symmetrical magnetic field is formed. The mover 4 is subjected to magnetic force within this magnetic field, and the magnitude of this force is closely related to the size of the air gap. As the air gap decreases, the magnetic attraction force on the mover 4 increases. However, because the rate of change of magnetic force with displacement (i.e., the magnetic gradient) is negative, the overall system exhibits a nonlinear characteristic of "increased displacement, decreased restoring force," resulting in negative stiffness. This negative stiffness cancels out the positive stiffness provided by the hydraulic spring 2, helping the system maintain a quasi-zero stiffness state, thereby improving low-frequency vibration isolation performance.

[0078] The outer edge of the annular plate 41 of the mover 4 extends into the preset space 34 of the stator unit 3. This arrangement ensures that the mover 4 is fully within the range of the magnetic field to obtain a stable and uniform electromagnetic force, while avoiding mechanical contact between the mover 4 and the stator, thus ensuring the smoothness and reliability of the system operation. At the same time, this structural design provides the mover 4 with a certain displacement adjustment space, allowing it to undergo appropriate displacement under load changes or external excitation, thereby triggering the negative stiffness adjustment mechanism and achieving dynamic balance.

[0079] The mover 4 structure, configured in this way, is connected to components such as the pneumatic spring 6 and hydraulic spring 2 via the connecting pipe 42, forming a closed-loop system for displacement transmission and force feedback. When the mover 4 is displaced due to external excitation, it not only generates electromagnetic force changes related to the air gap, but also drives the pneumatic spring 6 and hydraulic spring 2 to move synchronously through the connecting pipe 42, ensuring real-time matching of positive and negative stiffness. Simultaneously, the displacement sensor 5 in the system collects the displacement signal of the mover 4 or the load in real time and feeds it back to the controller. The controller adjusts the current of the stator unit 3 according to the deviation, further precisely controlling the magnetic field strength and magnetic force gradient, maintaining the mover 4 in the quasi-zero stiffness balance range, and effectively coping with load changes and frequency fluctuations.

[0080] In a preferred embodiment, the positive and negative stiffness connection mechanism includes several pneumatic springs 6, which are evenly distributed around the hydraulic spring 2 to realize displacement transmission and coordinated control between the positive stiffness mechanism and the negative stiffness mechanism. At the same time, it plays a role in buffering and auxiliary adjustment, which helps to broaden the frequency band of the system's low-frequency vibration isolation and improve the stability and adaptability of the overall vibration isolation performance.

[0081] Specifically, one end of each pneumatic spring 6 is connected to the upper connecting seat 8 of the hydraulic spring 2, and the other end is connected to the top of the connecting pipe 42 of the mover 4. In this embodiment, six pneumatic springs 6 are preferably arranged in a ring around the hydraulic spring 2, thereby ensuring that the force exerted by each pneumatic spring 6 on the mover 4 and the hydraulic spring 2 is balanced, and improving the stability and uniformity of the overall structure.

[0082] Furthermore, the pneumatic spring 6 in this embodiment is a nitrogen-pressurized structure. Internally, a piston guide rod pushes a pneumatic piston, thereby dividing the air chamber into different pressure zones to adjust the spring force. Structurally, the pneumatic spring 6 includes a piston guide rod, a pneumatic piston, an air chamber, and a corresponding airtight structure. The airtight material ensures the airtightness of the air chamber, preventing gas leakage from affecting spring performance. By adjusting the gas pressure within the air chamber, it can adapt to different load conditions. Simultaneously, nitrogen, as the working medium, has good stability and durability, helping to extend the service life of the pneumatic spring 6.

[0083] The pneumatic spring 6 in the positive and negative stiffness connection mechanism, as an intermediate component connecting the hydraulic spring 2 (providing positive stiffness) and the mover 4 (participating in the formation of negative stiffness), can effectively transmit the displacement changes between the two, ensuring that the positive and negative stiffness remain coordinated and balanced during dynamic processes. When the load or external excitation causes displacement of the mover 4 or the hydraulic spring 2, the pneumatic spring 6 responds synchronously, ensuring that the relative movement between the mover 4 and the hydraulic spring 2 is within a controllable range, avoiding the failure of negative stiffness adjustment due to displacement mismatch, thereby maintaining the quasi-zero stiffness state of the entire system.

[0084] The structural design of six pneumatic springs 6 evenly distributed around the hydraulic spring 2 ensures a uniform force distribution between the pneumatic springs 6 and the mover 4 and hydraulic spring 2, avoiding structural deformation or performance degradation caused by localized stress concentration or uneven force distribution. This layout helps improve the overall mechanical stability of the system, ensuring that the pneumatic springs 6 can coordinate their movements under load changes or external excitations to jointly achieve displacement transmission and buffering functions, thereby enhancing the vibration isolator's adaptability under complex working conditions.

[0085] The pneumatic spring 6, pressurized with nitrogen, allows for control of its stiffness by adjusting the internal air pressure. This enables it not only to perform basic displacement transmission but also to adjust its buffering characteristics according to actual working conditions. This, in turn, assists the hydraulic spring 2 and the electromagnetic negative stiffness mechanism in further suppressing low-frequency vibration energy. Furthermore, the pneumatic spring 6 forms a compressible buffer layer between the mover 4 and the hydraulic spring 2, avoiding rigid constraints between them. This helps ensure stability and reliability during negative stiffness adjustment, especially under conditions of large displacement or high-frequency disturbances, effectively absorbing impact and vibration energy and improving the overall vibration isolation effect.

[0086] The pneumatic spring 6, together with the displacement sensor 5, controller, and other control modules in the system, forms a closed-loop control system. When the displacement sensor 5 detects a change in the displacement of the mover 4 or the load, the controller adjusts the stator coil current to control the magnitude of the electromagnetic negative stiffness. At the same time, the pneumatic spring 6, through its own adjustable characteristics and uniformly distributed mechanical transmission path, assists the system in quickly restoring to the quasi-zero stiffness equilibrium position, improving the system's response speed and control accuracy to load changes and frequency fluctuations.

[0087] In a preferred embodiment, the hydraulic spring 2 includes an elastic body chamber and a liquid flow channel. Through the synergistic effect of mechanical compression and fluid damping, it provides basic positive stiffness for the vibration isolator and generates a damping effect during displacement to help dissipate vibration energy. It is a key functional component for achieving load support and low-frequency vibration isolation stability.

[0088] Specifically, the hydraulic spring 2 is the core component of the positive stiffness mechanism of the vibration isolator. Its main structure includes an elastic body chamber and an internal liquid flow channel. The elastic body chamber is a closed cavity that contains hydraulic oil or other working fluids. When the vibration isolator is under load, the elastic body chamber undergoes elastic deformation under pressure, the chamber volume decreases, and the internal liquid pressure increases, thereby generating a positive restoring force that increases with the increase of displacement. The positive restoring force is the "positive stiffness" of the vibration isolator, which is used to directly support the external load and form a mechanical balance with the negative stiffness mechanism (such as the negative stiffness generated by electromagnetic force) to jointly maintain the dynamic stability of the system in the quasi-zero stiffness range.

[0089] Meanwhile, the hydraulic spring 2 has a liquid flow channel inside. When the elastic body chamber is deformed by pressure, the internal liquid needs to flow through this channel between different areas of the chamber. Due to the small cross-sectional area of ​​the flow channel, the liquid flow encounters significant resistance, thus generating a damping effect related to the displacement velocity. This damping effect can convert vibration energy into heat energy and dissipate it, effectively suppressing the accumulation and transmission of vibration energy. Especially when there are sudden load changes or fluctuations in the external excitation frequency, it can help reduce the vibration amplitude of the system and improve the stability of the vibration isolation effect.

[0090] As a preferred embodiment, the mover 4 is made of high permeability silicon steel sheet. The magnitude of the force it experiences is determined by the magnetic field strength generated by the stator unit 3 and the air gap distance between the mover 4 and the stator unit 3. This design is the key technical basis for achieving precise magnetic response and negative stiffness control of the mover 4.

[0091] Specifically, the mover 4 is the moving component in the vibration isolator that directly interacts with the magnetic field of the stator unit 3. Its main structure is an annular plate 41, and it is equipped with a connecting pipe 42 for connecting with components such as the pneumatic spring 6 and the hydraulic spring 2. In this embodiment, high-permeability silicon steel sheets are selected as the manufacturing material for the mover 4. By utilizing its high permeability characteristics, the mover 4 can quickly and sensitively sense the magnetic force in the magnetic field generated by the stator unit 3, thereby ensuring a stable and predictable correspondence between the electromagnetic force received by the mover 4 and the air gap change.

[0092] The force mechanism of the mover 4 is based on the fundamental principles of electromagnetic fields: the stator unit 3 forms a symmetrical magnetic field array by passing a reverse current through it. The mover 4 is located within the range of this magnetic field, and the magnitude of the magnetic attraction it experiences is mainly determined by two factors: first, the magnetic field strength generated by the stator unit 3 (directly related to the coil current and magnetic field distribution); and second, the air gap distance between the mover 4 and the stator unit 3 (i.e., the vertical distance between the mover 4 and the magnetic poles). When the mover 4 undergoes axial displacement due to external excitation, the air gap distance changes accordingly: a smaller air gap increases the magnetic attraction, and a larger air gap decreases the magnetic attraction. Simultaneously, due to the negative characteristic of the magnetic field gradient, it ultimately exhibits a nonlinear negative stiffness behavior of "increased displacement and decreased restoring force."

[0093] In a preferred embodiment, the stator support 31 adopts a layered structural design, specifically including a vertical plate 311 and four horizontal plates 312 fixed sequentially from top to bottom on the vertical plate 311. The four horizontal plates 312 and the vertical plate 311 together enclose a specific installation space for arranging the coil windings of the stator unit 3 in layers and providing a stable magnetic field area for the mover 4. This structural design realizes the modular assembly of the stator unit 3 and the optimization of the magnetic field environment, which is an important foundation for ensuring precise control of negative stiffness and stable system operation.

[0094] Specifically, the four horizontal plates 312 form three functional spaces from top to bottom: a first installation space 35, a preset space 34, and a second installation space 36. The first installation space 35 is located between the uppermost horizontal plate 312 and the second-uppermost horizontal plate 312, and is used to install the upper stator coil winding 32. The preset space 34 is located between the middle horizontal plate 312 and the second-lower horizontal plate 312, providing a magnetic field area for the mover 4 to levitate and move. The preset space 34 is directly related to the magnetic field distribution of the stator unit 3 and is a key area where the mover 4 is subjected to magnetic force and forms negative stiffness. The second installation space 36 is located between the second-lower horizontal plate 312 and the lowermost horizontal plate 312, and is used to install the lower stator coil winding 33.

[0095] The upper coil winding 32 and the lower coil winding 33 of the stator are wound in the corresponding first mounting space 35 and second mounting space 36, respectively, and their energizing directions are opposite. For example, the end of the upper coil facing the mover 4 forms the north pole, and the end of the lower coil facing the mover 4 forms the south pole, or they are configured in opposite directions, thereby forming a symmetrically distributed magnetic field array in the preset space 34 where the mover 4 is located. This symmetrical magnetic field interacts with the mover 4, causing the magnetic attraction force on the mover 4 to exhibit nonlinear characteristics with the change of the air gap between it and the magnetic pole, thus forming negative stiffness to counteract the positive stiffness provided by the hydraulic spring 2 and achieve dynamic maintenance of the quasi-zero stiffness state of the system.

[0096] Example 2

[0097] See Figure 11 The present invention also provides a control method for the electromagnetic quasi-zero stiffness vibration isolator as described in Embodiment 1. By real-time monitoring of the displacement of the mover 4 and dynamic adjustment of the stator unit 3 coil current, the synergistic effect of electromagnetic negative stiffness and positive stiffness is precisely controlled, so that the system is always maintained in the quasi-zero stiffness range, thereby achieving load-adaptive low-frequency vibration isolation. The method specifically includes the following steps:

[0098] S1. Constructing an initial quasi-zero stiffness magnetic field environment:

[0099] After the system starts, an initial current is first supplied to the coil windings of each stator unit 3, so that the upper and lower coils are supplied with currents in opposite directions. For example, the end of the upper coil facing the mover 4 forms the north pole, and the end of the lower coil facing the mover 4 forms the south pole, or they can be configured in reverse. The polarity and magnitude of the initial current are calibrated so that the 12 stator units 3 (which work together to form a symmetrical magnetic field array of 24 magnetic poles) generate a stable magnetic field with vertical symmetry in the region where the mover 4 is located. At this time, the mover 4, made of a high-permeability material, is suspended in the magnetic field with a preset initial air gap under the action of the magnetic field force, maintaining a safe and controllable relative position with the stator units 3, providing a reference state for subsequent dynamic adjustment.

[0100] S2. Real-time acquisition of displacement signal of mover 4:

[0101] During the operation of the vibration isolator, changes in external load (such as increases or decreases in load weight) or vibration excitation (such as low-frequency mechanical vibration) will cause the mover 4 to generate axial displacement (e.g., compression or tension relative to the initial air gap). The system uses displacement sensors 5 fixed to the support or the connection point of the mover 4 to collect the displacement signal (including displacement magnitude and direction) of the mover 4 in real time and transmit the displacement signal to the controller (such as the H∞ controller). This step enables rapid perception of changes in the system state and provides input basis for subsequent dynamic adjustment.

[0102] S3. Calculate the target current value:

[0103] After receiving the displacement signal collected by displacement sensor 5, the controller calculates the degree to which the mover 4 deviates from its equilibrium position based on a preset control algorithm (H∞ control algorithm), and further calculates the target current value required to restore the mover 4 to its equilibrium position (i.e., the initial air gap position corresponding to the quasi-zero stiffness state). The target current value corresponds to the current that the stator unit 3 coil winding needs to be adjusted to. Its calculation logic comprehensively considers the air gap change between the mover 4 and the stator, the nonlinear relationship between the magnetic field strength and the magnetic force gradient, i.e., the negative stiffness characteristic of "displacement increases, restoring force decreases", and the balance between the positive stiffness provided by the hydraulic spring 2 and the load support requirements.

[0104] S4. Dynamically adjust the coil current to maintain a near-zero stiffness state:

[0105] The drive circuit adjusts the current magnitude of the upper coil winding 32 and the lower coil winding 33 in each stator unit 3 in real time according to the target current value output by the controller. By adjusting the current intensity input to the coil windings, the magnetic field strength and magnetic gradient are changed. This adjustment process is specifically manifested as follows: if the displacement sensor 5 detects that the displacement of the mover 4 is too large (for example, due to the air gap decreasing due to increased load), the controller outputs a "increase stator current" command, and the drive circuit increases the coil current to enhance the magnetic field attraction to balance the load change; if the displacement is too small (for example, due to the air gap increasing), it outputs a "decrease current" command to reduce the magnetic field strength to avoid excessive restoring force. By dynamically adjusting the synergistic effect of electromagnetic negative stiffness (related to the mover 4-stator air gap) and positive stiffness (provided by the hydraulic spring 2), the system can compensate for the stiffness deviation caused by load changes or excitation fluctuations in real time, ultimately keeping the mover 4 stably maintained in the quasi-zero stiffness balance range, ensuring that low-frequency vibration energy is effectively suppressed.

[0106] By acquiring the displacement signal of the mover 4 in real time through displacement sensor 5, the controller can quickly identify system state deviations caused by load changes or external excitations, such as the mover 4 deviating from the initial air gap, and accurately calculate the target current value based on the control algorithm. The rapid adjustment capability of the drive circuit allows the stator coil current to be adjusted in real time, ensuring that the electromagnetic negative stiffness and positive stiffness are always in a dynamic balance state, effectively solving the technical problem of the sharp decline in vibration isolation performance of traditional passive vibration isolators when the load changes.

[0107] By precisely controlling the current of stator unit 3 coil, this method can accurately adjust the magnetic field strength and magnetic gradient between the mover 4 and the stator, thereby changing the magnitude of the negative stiffness. When the load increases, causing the positive stiffness to rise, the controller increases the current to enhance the negative stiffness and offset its effect; conversely, it decreases the current to reduce the negative stiffness. This dynamic compensation mechanism ensures that the positive and negative stiffness always work synergistically, and the overall system stiffness approaches zero (quasi-zero stiffness state), which has a significant suppression effect on low-frequency vibrations and improves the adaptability of the vibration isolator under complex working conditions.

[0108] This control method is deeply coupled with the hardware structure of the vibration isolator, forming a closed-loop control process of "sensing-computation-adjustment". Displacement sensor 5 provides real-time status feedback, the controller generates adjustment commands based on the physical model and control strategy, the drive circuit executes current adjustment, and finally achieves precise control of the displacement of the mover 4 through magnetic field changes. This collaborative mechanism ensures that the system can stably maintain a near-zero stiffness state under load changes, frequency fluctuations, or external impacts, significantly expanding the application scenarios and reliability of the vibration isolator.

[0109] In a preferred embodiment, the controller uses the H∞ control algorithm to calculate the target current value required to restore the mover 4 to its equilibrium position, and adjusts the current in the stator unit 3 coil windings to change the magnetic field strength and magnetic gradient, thereby achieving dynamic control of the nonlinear negative stiffness. This control strategy is a key technical means to solve the problem of the system deviating from the quasi-zero stiffness state due to load changes or external excitations, and to ensure the stability of low-frequency vibration isolation performance.

[0110] Specifically, when the vibration isolator is in operation, changes in external load or low-frequency vibration excitation will cause axial displacement of the mover 4, resulting in a change in the air gap between the mover 4 and the stator unit 3. The change in air gap directly affects the magnitude and characteristics of the electromagnetic force on the mover 4: since the upper and lower coil windings 33 of the stator unit 3 are supplied with reverse current to form a symmetrical magnetic field, the magnetic attraction force on the mover 4 in this magnetic field increases as the air gap decreases, but the magnetic force gradient is negative, exhibiting a nonlinear characteristic of "displacement increases and restoring force decreases", that is, forming nonlinear negative stiffness.

[0111] Traditional control methods struggle to achieve accurate stiffness compensation when dealing with such nonlinear characteristics and dynamic load changes, easily causing the system to deviate from the quasi-zero stiffness range. This embodiment effectively solves the above problems by employing the H∞ control algorithm.

[0112] H∞ control is a robust control method whose core objective is to optimize the control law so that the system can keep key outputs (such as mover displacement) within the allowable range when facing the worst disturbances, while minimizing control error and system sensitivity.

[0113] Specifically, the technical implementation logic of the H∞ control algorithm is as follows:

[0114] State perception and signal input: Displacement sensor 5 collects the displacement signal of mover 4 in real time and transmits the signal to the controller. The displacement signal reflects the current actual state of the system and is the basic input for the controller to perform calculations.

[0115] Target current calculation: The controller, based on the H∞ control algorithm, analyzes and processes the displacement signal. The H∞ control algorithm uses the displacement of the mover 4 as the input variable and the target current value of the stator unit 3 coil winding as the output variable. Through mathematical optimization, such as solving the optimal control problem under the H∞ performance index, it calculates the target current value required to restore the mover 4 to its equilibrium position (i.e., the initial air gap position corresponding to quasi-zero stiffness). This calculation process comprehensively considers the air gap change between the mover 4 and the stator, the nonlinear characteristics of the magnetic field strength, the negative change law of the magnetic gradient, and interference factors introduced by load changes or external excitation.

[0116] Dynamic current regulation and magnetic field control: The drive circuit adjusts the current in the upper coil winding 32 and the lower coil winding 33 of the stator unit 3 in real time according to the target current value output by the controller. The change in current directly changes the magnetic field strength and magnetic gradient generated by the stator unit 3, thereby adjusting the magnitude and characteristics of the electromagnetic force on the mover 4. When the displacement of the mover 4 is too large, the controller outputs a command to increase the current to enhance the magnetic field attraction to balance the load change; when the displacement is too small, it outputs a command to decrease the current to reduce the magnetic field strength to avoid excessive restoring force.

[0117] By employing the H∞ control algorithm to calculate the target current value and adjusting the magnetic field strength and magnetic gradient by regulating the current in stator unit 3 coil, dynamic control of the nonlinear negative stiffness is achieved. This control method effectively solves the problem of quasi-zero stiffness deviation caused by load changes or external excitation, improving the vibration suppression performance of the vibration isolator in the low-frequency range and its robustness under complex working conditions. It is the key technical support for this invention to achieve the core function of "adapting to load changes and maintaining stable vibration isolation".

[0118] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An electromagnetic quasi-zero stiffness vibration isolator, characterized in that, include: Base; A positive stiffness mechanism for supporting external loads and providing basic positive stiffness includes a hydraulic spring with its bottom end located in the middle of the base; A negative stiffness mechanism, connected in parallel with the positive stiffness mechanism, is used to generate nonlinear negative stiffness to counteract the positive stiffness. It includes multiple stator units arranged in a ring array on the base, and a mover suspended at the center of the magnetic field of the stator units. The top end of a hydraulic spring passes through the mover and is connected to a support platform, with a preset gap maintained between the hydraulic spring and the inner wall of the mover. Each stator unit includes a stator support and upper and lower coil windings arranged from top to bottom on the stator support, with a preset space between the upper and lower coil windings. Currents in opposite directions are passed through the upper and lower coil windings of the stator unit to form a symmetrically distributed magnetic field in the region where the mover is located. The mover includes an annular plate and a connecting tube disposed on the upper surface of the annular plate. The outer edge of the annular plate extends into the preset space of the stator unit, and the electromagnetic force it experiences varies with the air gap between the stator unit and the mover, thereby forming a negative stiffness characteristic. A positive and negative stiffness connection mechanism is provided between the hydraulic spring and the moving part to realize displacement transmission and coordinated adjustment. It includes several pneumatic springs; the several pneumatic springs are evenly distributed around the hydraulic spring; one end of each pneumatic spring is connected to the hydraulic spring, and the other end is connected to the top of the connecting tube of the moving part. The dynamic control module includes a displacement sensor mounted on the receiving platform and a controller electrically connected to the displacement sensor. The displacement sensor is used to collect load displacement signals, and the controller adjusts the excitation current of the stator unit according to the displacement signals to adjust the electromagnetic force so that the vibration isolator is maintained in the quasi-zero stiffness range.

2. The electromagnetic quasi-zero stiffness vibration isolator according to claim 1, characterized in that, Multiple stator units are uniformly arranged along the circumference of the mover to form a multi-pole symmetrical magnetic field array, enabling the mover to obtain a stable electromagnetic force gradient in the axial direction.

3. The electromagnetic quasi-zero stiffness vibration isolator according to claim 1, characterized in that, The pneumatic spring is a nitrogen-pressurized type, which pushes the pneumatic piston to form an air chamber through the piston guide rod, and there are six pneumatic springs distributed around the hydraulic spring.

4. An electromagnetic quasi-zero stiffness vibration isolator according to any one of claims 1-3, characterized in that, The hydraulic spring includes an elastic body chamber and a liquid flow channel. When the vibration isolator is loaded and displaced, the elastic body chamber provides a positive restoring force that increases with the displacement, and the liquid flows through the flow channel to generate a damping effect.

5. An electromagnetic quasi-zero stiffness vibration isolator according to any one of claims 1-3, characterized in that, The stator support includes a vertical plate and four horizontal plates arranged from top to bottom on the vertical plate. The four horizontal plates form a first installation space, a preset space, and a second installation space from top to bottom. The upper coil winding is arranged in the first installation space, and the lower coil winding is arranged in the second installation space.

6. A control method for an electromagnetic quasi-zero stiffness vibration isolator as described in any one of claims 1-5, characterized in that, Includes the following steps: An initial current is passed through the coil windings of each stator unit to construct an upper and lower symmetrical magnetic field array, so that the mover is suspended in the initial air gap under the action of magnetic force. The displacement signal of the mover caused by changes in external load or vibration excitation is collected in real time by a displacement sensor. Based on the displacement signal, the controller calculates the target current value required to restore the mover to the equilibrium position; The drive circuit adjusts the current in each coil winding of the stator unit, and by changing the synergistic effect of electromagnetic negative stiffness and positive stiffness, it compensates for the stiffness deviation caused by load changes, so that the system remains in a quasi-zero stiffness state.

7. The control method according to claim 6, characterized in that, The controller uses the H∞ control algorithm to calculate the required target current value, and adjusts the current to change the magnetic field strength and magnetic gradient, thereby achieving dynamic control of the nonlinear negative stiffness.

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