Electromagnetic quasi-zero stiffness vibration isolator and control method

Abstract

The invention 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 and 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 distributed on the base in an annular array and a rotor suspended in the center of a magnetic field of the stator units, and is used for generating nonlinear negative stiffness; the top end of the hydraulic spring supports a load through the bearing table and keeps a preset gap with the inner wall of the rotor; the positive and negative stiffness connecting mechanism realizes displacement transmission and cooperative adjustment; the dynamic control module comprises a displacement sensor and a controller, the sensor collects displacement signals, and the controller adjusts excitation currents of the stator units according to the signals and dynamically adjusts electromagnetic force, so that the vibration isolator is kept in a quasi-zero stiffness state. The quasi-zero stiffness state can be still kept when the load changes, load self-adaption low-frequency vibration isolation is achieved, and the system stability and the vibration isolation performance are improved.

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] The present application provides an electromagnetic quasi-zero stiffness vibration isolator, which can maintain quasi-zero stiffness operating state under different loads through parallel arrangement of positive stiffness mechanism and adjustable electromagnetic negative stiffness mechanism combined with displacement feedback-based current closed-loop control, thereby improving the effectiveness and stability of low-frequency vibration isolation, and having the advantages of compact structure and wide application range.

[0032] The positive stiffness mechanism with hydraulic spring and mover gap cooperation has simple structure and strong bearing capacity, can stably provide basic positive stiffness, and ensures that the motion of the negative stiffness mechanism does not interfere with each other through the preset gap with the inner wall of the mover, thereby laying a reliable foundation for subsequent stiffness adjustment.

[0033] The negative stiffness mechanism composed of annular array arrangement of stator units and suspended mover uses electromagnetic force to form non-contact nonlinear negative stiffness. Since there is no mechanical contact, friction loss and operating energy consumption can be reduced, and service life can be prolonged; the nonlinear characteristics of electromagnetic force can expand the quasi-zero stiffness interval within a certain displacement range, thereby improving the suppression ability of low-frequency vibration.

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

[0035] The dynamic control module composed of the displacement sensor arranged on the receiving table and the controller can detect the load displacement in real time and adjust the excitation current of the stator unit accordingly, thereby accurately controlling the electromagnetic force. This closed-loop control method enables the vibration isolator to continuously and quickly correct the negative stiffness value according to the actual load condition, thereby realizing load-adaptive stiffness matching and avoiding vibration failure caused by load variation.

[0036] The combination scheme in which the positive stiffness is provided by the hydraulic spring and the negative stiffness is formed by the adjustable electromagnetic force enables the vibration isolator to cope with different load conditions without replacing or disassembling the structure, thereby being convenient to operate and widely applicable; while taking into account the high bearing capacity, the vibration isolator solves the contradiction between the low-frequency vibration performance and the bearing capacity in the traditional vibration isolator. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0038] Figure 1 FIG. 1 is a front view of an electromagnetic quasi-zero stiffness vibration isolator according to the present application;

[0039] Figure 2 Fig. 1 is a perspective view of an electromagnetic quasi-zero stiffness vibration isolator according to the present application;

[0040] Figure 3 Fig. 2 is a C-C sectional view of the electromagnetic quasi-zero stiffness vibration isolator according to the present application; Figure 2

[0041] Figure 4 Fig. 3 is a perspective view of a mover suspended in the center of a magnetic field of each stator unit according to the present application;

[0042] Figure 5 Fig. 4 is a perspective view of a hydraulic spring, a mover and each pneumatic spring connected according to the present application;

[0043] Figure 6 Fig. 5 is a perspective view of a hydraulic spring and each pneumatic spring connected according to the present application;

[0044] Figure 7 Fig. 6 is a perspective view of a stator unit according to the present application;

[0045] Figure 8 Fig. 7 is a sectional view of a stator support according to the present application;

[0046] Figure 9 Fig. 8 is a perspective view of a coil winding according to the present application;

[0047] Figure 10 Fig. 9 is a perspective view of a pneumatic spring according to the present application;

[0048] Figure 11 Fig. 10 is a flowchart of a control method of an electromagnetic quasi-zero stiffness vibration isolator according to the present application.

[0049] Reference numerals:

[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 mounting space; 36, second mounting space; 4, mover; 41, annular plate; 42, connecting pipe; 5, displacement sensor; 6, pneumatic spring; 7, receiving table; 8, upper connecting seat; 9, lower connecting seat.

[0051] The purposes, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0052] ​The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort should fall within the protection scope of the present application.

[0053] It should be noted that all directional indications, such as up, down, etc., in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0054] In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features.

[0055] In addition, the technical solutions of the various embodiments of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0056] Example 1

[0057] Referring to Figures 1-10 The present application provides an electromagnetic quasi-zero stiffness vibration isolator, which comprises a base 1, a positive stiffness mechanism, a negative stiffness mechanism, a positive-negative stiffness connecting mechanism and a dynamic control module. Each component is arranged and matched as follows to realize the quasi-zero stiffness maintenance and low-frequency vibration isolation function under load change.

[0058] The base 1 is a support base body with an integral structure.

[0059] The positive stiffness mechanism comprises a hydraulic spring 2, the bottom end of which is fixed to the middle part of the base 1 through a lower connecting seat 9, the top end of which extends upward and penetrates a moving part 4, and the moving part 4 is connected with a receiving table 7 through an upper connecting seat 8. The hydraulic spring 2 generates linear positive stiffness when bearing external load, thereby providing stable basic support force for the vibration isolator. Placing the hydraulic spring 2 in the middle part of the base 1 is conducive to uniform load distribution and improves the bearing capacity. A preset gap is provided between the hydraulic spring 2 and the inner wall of the moving part 4, which not only avoids friction loss caused by direct contact between the two, but also ensures the free movement of the moving part 4 within the controlled displacement range. This gap design, combined with the bearing characteristics of the hydraulic spring 2, enables the positive stiffness mechanism to remain stable during operation and provides space for the non-contact arrangement of the negative stiffness mechanism; the receiving table 7 is used to set the load.

[0060] The negative stiffness mechanism is arranged in parallel with the positive stiffness mechanism and includes a plurality of stator units 3 and a mover 4. The plurality of stator units 3 are arranged in a ring array along the circumference of the base 1, and the mover 4 is located at the center of the magnetic field of the stator units 3 and suspended in the magnetic field without relying on mechanical support. By passing exciting current to the stator units 3, a controllable electromagnetic force can be generated on the mover 4, which changes nonlinearly with displacement, thereby forming nonlinear negative stiffness to offset the positive stiffness of the hydraulic spring 2. The advantage of using electromagnetic force to achieve negative stiffness is that electromagnetic non-contact action can reduce mechanical wear and energy loss, improve reliability and service life.

[0061] The positive and negative stiffness connecting mechanism is arranged between the hydraulic spring 2 and the mover 4, which functions to transmit the displacement change 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 the mover 4 and the top end of the hydraulic spring 2 respond synchronously when the displacement changes due to load or external excitation, so that the positive and negative stiffness always match in 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 on the receiving table 7 and directly senses the load displacement signal, which can timely reflect the changes in the working state of the isolator. The controller is electrically connected with the displacement sensor 5, receives the displacement signal, and adjusts the exciting current of each stator unit 3 according to the preset control strategy, thereby changing the electromagnetic force, matching the negative stiffness and the positive stiffness in real time, and ensuring that the isolator operates in the quasi-zero stiffness range under different load conditions. This closed-loop control mode overcomes the defect that the passive quasi-zero stiffness isolator easily deviates from the optimal isolation state under load changes, realizes load-adaptive stiffness adjustment, and has the advantages of fast response speed and high adjustment precision.

[0063] With such an arrangement, the isolator can continuously adjust the electromagnetic force according to the displacement feedback by the dynamic control module when subjected to different loads, so that the negative stiffness offsets the positive stiffness within a certain displacement range, thereby maintaining the quasi-zero stiffness operating state under varying loads. This not only solves the problem of isolation failure of traditional passive isolators due to load variation, but also reduces friction and energy consumption due to the use of non-contact electromagnetic negative stiffness mechanism, and widens the quasi-zero stiffness range by using the nonlinearity of electromagnetic force, taking into account the low-frequency isolation performance and load capacity, with compact structure and convenient adjustment, suitable for various occasions requiring low-frequency isolation and variable load.

[0064] As a preferred embodiment, the stator unit 3 in the negative stiffness mechanism comprises a stator support 31, and an upper coil winding 32 and a lower coil winding 33 arranged in sequence from top to bottom on the stator support 31, wherein the upper coil winding 32 and the lower coil winding 33 have a preset spatial interval therebetween for arranging the mover 4 and ensuring its free suspension and displacement in the magnetic field.

[0065] Specifically, the stator support 31 is usually made of a metal material (such as high-permeability steel sheet) with good magnetic conductivity to enhance the magnetic field conduction efficiency. The upper coil winding 32 and the lower coil winding 33 are wound on the stator support 31 respectively, and the current directions of the two are opposite, i.e., the end of the upper coil winding 32 facing the mover 4 forms a north pole, and the end of the lower coil winding 33 facing the mover 4 forms a south pole, or vice versa, so as to form an upper and lower symmetrically distributed magnetic field array in the area where the mover 4 is located.

[0066] By passing opposite currents through the upper coil and the lower coil, an upper and lower symmetric and controllable magnetic field distribution can be formed around the mover 4. This magnetic field interacts with the high-permeability mover 4 (such as the mover 4 made of ferromagnetic material), so that the mover 4 is subjected to a magnetic attraction force related to displacement. When the mover 4 vertically displaces due to external excitation or load change, the air gap between the mover 4 and the magnetic pole changes, thereby causing the magnetic force gradient to change, forming a "displacement increases, restoring force decreases" nonlinear negative stiffness characteristic. This negative stiffness characteristic is the key to offsetting the positive stiffness and achieving the quasi-zero stiffness state, which helps to improve the low-frequency vibration isolation performance.

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

[0068] The stator unit 3 thus arranged provides a structural basis for subsequent adjustment of the current size of the upper coil winding 32 and the lower coil winding 33 by 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 coil and the lower coil in real time according to the deviation, thereby changing the magnetic field strength and the magnetic force gradient, dynamically adjusting the negative stiffness size, making the system quickly return to the quasi-zero stiffness equilibrium position, and effectively dealing with the vibration isolation performance fluctuation caused by load change or external excitation.

[0069] The embodiment sets the stator unit 3 to contain the upper and lower coil windings 33 with a preset interval, and makes the two coil current directions opposite, to construct a symmetrical and controllable magnetic field environment, to provide the mover 4 with displacement-related nonlinear negative stiffness, which is an important structural basis for realizing load-adaptive quasi-zero stiffness vibration isolation. This design not only has a reasonable structure and is easy to control, but also cooperates with other components in the system (such as the mover 4, the hydraulic spring 2, the pneumatic spring 6, and the controller) to improve the stability and low-frequency vibration isolation capability of the vibration isolator under variable load conditions.

[0070] As a preferred embodiment, the plurality of stator units 3 are uniformly arranged circumferentially around the mover 4 to cooperatively 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, with a preset space 34 between the upper coil winding 32 and the lower coil winding 33, and the two coil current directions are opposite, thereby forming an up-down symmetrical magnetic field in the area where the mover 4 is located. A plurality of such stator units 3 are uniformly arranged circumferentially around the mover 4, for example but not limited to in a ring array, and in a typical embodiment there can be 12 stator units 3, which cooperatively form a multi-pole symmetrical magnetic field array.

[0072] The present application uniformly arranges a plurality of stator units 3 circumferentially around the mover 4, and the magnetic fields generated by each stator unit 3 are superimposed and coordinated in space to form a multi-pole magnetic field environment that is symmetrical and uniformly distributed as a whole. In this magnetic field, the mover 4 is located in the central region of the magnetic field and is subjected to the magnetic force from each stator unit 3, which is integrated to exhibit a stable and continuous electromagnetic force gradient in the axial direction. The electromagnetic force gradient is the basis for realizing the nonlinear negative stiffness characteristic of "increasing displacement and reducing restoring force", which helps the mover 4 to receive a displacement-related restoring force when subjected to vertical disturbance, thereby offsetting the positive stiffness and maintaining the quasi-zero stiffness state.

[0073] The circumferentially uniform arrangement of the stator units 3 ensures the consistency and symmetry of the magnetic field around the mover 4, avoids the problem of uneven force caused by local magnetic field being too strong or too weak, and improves the uniformity of the electromagnetic force distribution. This uniform magnetic field environment makes the electromagnetic force change more stable and predictable during the axial displacement of the mover 4, which 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, to realize precise control of the negative stiffness and improve the reliability and stability of the overall vibration isolation effect.

[0074] As a preferred embodiment, the mover 4 comprises a ring-shaped plate 41 and a connecting pipe 42 arranged on the upper surface of the ring-shaped plate 41, wherein the outer edge of the ring-shaped plate 41 extends into the preset space 34 of each stator unit 3, so as to be within the magnetic field generated by the plurality of stator units 3, so that when the mover 4 is displaced, the air gap between the outer edge of the mover 4 and the stator unit 3 changes, causing the electromagnetic force acting on the mover 4 to change accordingly, forming a nonlinear negative stiffness characteristic.

[0075] Specifically, the ring-shaped plate 41 of the mover 4 is usually made of high magnetic permeability material (such as high magnetic permeability steel sheet) to ensure good magnetic response characteristics. The ring-shaped plate 41 is arranged opposite to the stator unit 3 as the main magnetic component of the mover 4, wherein the outer edge of the ring-shaped plate 41 extends into the internal space (i.e. the preset space 34) formed by the plurality of stator units 3, which provides the mover 4 with a movable area allowing it to float up and down, while ensuring that the mover 4 and the stator maintain a reasonable initial air gap.

[0076] The connecting pipe 42 arranged on the upper surface of the mover 4 is used to realize the mechanical connection of the mover 4 with 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 through a fixing bolt, so as to form a mechanical-magnetic system in which the mover 4, the hydraulic spring 2 and the pneumatic spring 6 are integrally linked.

[0077] When external excitation (such as load change or low-frequency vibration) causes the mover 4 to produce axial displacement, the air gap between the ring-shaped plate 41 and the stator unit 3 changes. Since the coil winding 32 of the stator unit 3 is connected to a reverse current, an upper and lower symmetrical magnetic field is formed, and the mover 4 is subjected to a magnetic force in this magnetic field, the size of which is closely related to the size of the air gap. As the air gap decreases, the magnetic attraction force acting on the mover 4 increases, but since the change rate of the magnetic force with displacement (i.e. the magnetic force gradient) is negative, the overall performance shows a nonlinear characteristic of "increasing displacement and decreasing restoring force", i.e. negative stiffness. The negative stiffness offsets the positive stiffness provided by the hydraulic spring 2, which helps to maintain the quasi-zero stiffness state of the system, thereby improving the low-frequency vibration isolation performance.

[0078] The outer edge of the ring-shaped plate 41 of the mover 4 extends into the preset space 34 of the stator unit 3, which not only ensures that the mover 4 can be fully within the magnetic field to obtain stable and uniform electromagnetic force, but also avoids mechanical contact between the mover 4 and the stator, ensuring the stability and reliability of the system. At the same time, this structural design provides a certain displacement adjustment space for the mover 4, so that it can be moderately displaced under load change or external excitation, thereby triggering the negative stiffness adjustment mechanism and realizing dynamic balance.

[0079] The mover 4 structure thus arranged is connected with the pneumatic spring 6, the hydraulic spring 2 and other components through the connecting pipe 42, and constitutes a closed loop system for displacement transmission and force feedback. When the mover 4 is displaced due to external excitation, not only the electromagnetic force change related to the air gap is generated, but also the pneumatic spring 6 and the hydraulic spring 2 are driven synchronously through the connecting pipe 42 to make the positive stiffness and the negative stiffness match in real time. At the same time, the displacement sensor 5 in the system collects the displacement signals of the mover 4 or the load in real time, and feeds back to the controller. The controller adjusts the current of the stator unit 3 according to the deviation, further accurately controls the magnetic field strength and the magnetic force gradient, maintains the mover 4 in the quasi-zero stiffness balance interval, and effectively responds to the load change and the frequency fluctuation.

[0080] As a preferred embodiment, the positive and negative stiffness connecting mechanism includes a plurality of pneumatic springs 6, which are uniformly distributed around the hydraulic spring 2, for realizing displacement transmission and coordinated control between the positive stiffness mechanism and the negative stiffness mechanism, and also play the roles of buffering and auxiliary adjustment, which helps to widen the frequency band of low-frequency vibration isolation of the system and improve the stability and adaptability of the overall vibration isolation performance.

[0081] Specifically, one end of each pneumatic spring 6 is connected with the upper connecting seat 8 of the hydraulic spring 2, and the other end is connected with the top of the connecting pipe 42 of the mover 4. In this embodiment, the pneumatic spring 6 is preferably arranged as six, and is uniformly distributed in a ring shape around the hydraulic spring 2, so as to ensure that the forces of the pneumatic springs 6 on the mover 4 and the hydraulic spring 2 are balanced, and the stability and force uniformity of the overall structure are improved.

[0082] Further, the pneumatic spring 6 in this embodiment is of a nitrogen pressurized structure, which separates the gas chamber into different pressure areas by a piston guide rod pushing a pneumatic piston, so as to realize the adjustment of spring force. Specifically, the pneumatic spring 6 includes a piston guide rod, a pneumatic piston, a gas chamber and a corresponding airtight structure, wherein the airtight material is used to ensure the airtightness of the gas chamber to prevent gas leakage from affecting the performance of the spring. By adjusting the gas pressure in the gas chamber, different load working conditions can be adapted, and nitrogen as the working medium has good stability and durability, which helps to prolong the service life of the pneumatic spring 6.

[0083] The pneumatic spring 6 in the positive and negative stiffness connecting 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 change between the two, so that the positive stiffness and the negative stiffness remain coordinated and balanced in the dynamic process. When the load or external excitation causes the displacement of the mover 4 or the hydraulic spring 2, the pneumatic spring 6 responds synchronously to ensure that the relative movement between the mover 4 and the hydraulic spring 2 is within a controllable range, avoiding the negative stiffness adjustment failure caused by displacement mismatch, so as to maintain the quasi-zero stiffness state of the whole system.

[0084] The six pneumatic springs 6 are evenly distributed around the hydraulic spring 2, which makes the force of each pneumatic spring 6 evenly distributed on the mover 4 and the hydraulic spring 2, avoiding local stress concentration or uneven force leading to structural deformation or performance degradation. This layout helps to improve the mechanical stability of the overall system, ensuring that each pneumatic spring 6 can work in coordination to achieve displacement transmission and buffering function under load changes or external excitation, enhancing the adaptability of the isolator under complex working conditions.

[0085] The pneumatic spring 6 adopts nitrogen pressurization, which can control the spring stiffness by adjusting the internal gas pressure, making it not only have the basic displacement transmission function, but also can adjust its buffering characteristics according to the actual working condition requirements, thereby assisting the hydraulic spring 2 and the electromagnetic negative stiffness mechanism to further suppress low-frequency vibration energy. In addition, the pneumatic spring 6 forms a compressible buffer layer between the mover 4 and the hydraulic spring 2, avoiding rigid constraints between them, which helps to ensure the stability and reliability during the negative stiffness adjustment process, especially in the case of large displacement or high-frequency disturbance, it can effectively absorb impact and vibration energy, improving the overall isolation effect.

[0086] The pneumatic spring 6 structure and the displacement sensor 5, controller and other control modules in the system together constitute 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 current of the stator coil to control the size of the electromagnetic negative stiffness, at the same time, the pneumatic spring 6 through its adjustable characteristics and uniform distribution of mechanical transmission path, assists the system to quickly restore to the quasi-zero stiffness balance position, improves the response speed and control accuracy of the system to load changes and frequency fluctuations.

[0087] As a preferred embodiment, the hydraulic spring 2 includes an elastomer chamber and a liquid flow channel, which provides the isolator with basic positive stiffness through the synergistic effect of mechanical compression and fluid damping, and generates damping effect during displacement to assist in dissipating vibration energy, is the key functional component to realize load support and low-frequency isolation stability.

[0088] Specifically, the hydraulic spring 2 is the core component of the positive stiffness mechanism of the isolator, and its main structure includes an elastomer chamber and an internal liquid flow channel. The elastomer chamber is a sealed cavity that contains hydraulic oil or other working liquid. When the isolator is loaded, the elastomer chamber is compressed and elastically deformed, the chamber volume decreases, and the internal liquid pressure rises, thereby generating a positive restoring force that increases with displacement. The positive restoring force is the "positive stiffness" of the isolator, which is used to directly support the external load, and forms a mechanical balance with the negative stiffness mechanism (such as the negative stiffness generated by the electromagnetic force), to maintain the dynamic stability of the system in the quasi-zero stiffness range.

[0089] At the same time, the hydraulic spring 2 is internally provided with a liquid flow channel, when the elastic body chamber is deformed under pressure, the internal liquid needs to flow through the flow channel between different areas of the chamber. Due to the small cross-sectional area of the flow channel, the liquid flow is significantly resisted, thereby generating a displacement speed related damping effect. This damping effect can convert vibration energy into heat energy and dissipate it, effectively inhibiting the accumulation and transmission of vibration energy, especially when the load suddenly changes or the external excitation frequency fluctuates, it can help to reduce the vibration amplitude of the system and improve the stability of the vibration isolation effect.

[0090] As a preferred embodiment, the material of the mover 4 is selected to be high permeability silicon steel sheet, and the stress 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 realizing the precise magnetic response and negative stiffness control of the mover 4.

[0091] Specifically, the mover 4 is a moving part in the vibration isolator that directly interacts with the magnetic field of the stator unit 3. Its main structure is a ring-shaped plate 41, and it is provided with a connecting pipe 42 for connecting with the pneumatic spring 6, the hydraulic spring 2 and other components. In this embodiment, high permeability silicon steel sheet is selected as the manufacturing material of the mover 4, which takes advantage of its high magnetic permeability characteristics to enable the mover 4 to quickly and sensitively respond to the magnetic force in the magnetic field generated by the stator unit 3, thereby ensuring a stable and predictable correspondence between the electromagnetic force acting on the mover 4 and the air gap change.

[0092] The stress mechanism of the mover 4 is based on the basic principle of electromagnetic field: the stator unit 3 forms a symmetrical magnetic field array by passing in a reverse current, and the mover 4 is located within the range of the magnetic field. The magnetic attraction force acting on the mover 4 is mainly determined by two factors: one is the magnetic field strength generated by the stator unit 3 (directly related to the coil current and magnetic field distribution), and the other is 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 pole). When the mover 4 is axially displaced due to external excitation, the air gap distance changes: the smaller the air gap, the greater the magnetic attraction force, and the greater the air gap, the smaller the magnetic attraction force; at the same time, due to the negative characteristics of the magnetic field gradient, the final performance is a nonlinear negative stiffness behavior of "increasing displacement, reducing restoring force".

[0093] As a preferred embodiment, the stator support 31 adopts a layered structure design, which specifically includes a vertical plate 311 and four horizontal plates 312 fixed on the vertical plate 311 from top to bottom. The four horizontal plates 312 and the vertical plate 311 together form a specific installation space for layering the coil winding of the stator unit 3 and providing a stable magnetic field action 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 basis for ensuring the precise control of negative stiffness and stable operation of the system.

[0094] Specifically, the four horizontal plates 312 form three functional spaces from top to bottom: the first installation space 35, the preset space 34, and the second installation space 36. Among them, the first installation space 35 is located between the uppermost horizontal plate 312 and the second upper horizontal plate 312, used for installing the upper coil winding 32 of the stator; the preset space 34 is located between the middle horizontal plate 312 and the second lower horizontal plate 312, providing a magnetic action area for the suspension and movement of the mover 4, and the preset space 34 is directly related to the magnetic field distribution of the stator unit 3, which is the key area for the mover 4 to be affected by the magnetic force and form negative stiffness; the second installation space 36 is located between the second lower horizontal plate 312 and the lowermost horizontal plate 312, used for installing the lower coil winding 33 of the stator.

[0095] The upper coil winding 32 of the stator and the lower coil winding 33 of the stator are wound in the corresponding first installation space 35 and second installation space 36 respectively, and the current directions of the two are opposite, for example, the north pole is formed at one end of the upper coil towards the mover 4, and the south pole is formed at one end of the lower coil towards the mover 4, or the reverse configuration, so as to form a symmetrical magnetic field array in the preset space 34 where the mover 4 is located. This symmetrical magnetic field interacts with the mover 4, so that the magnetic attraction force acting on the mover 4 presents a nonlinear characteristic with the change of the air gap between the mover 4 and the magnetic pole, thereby forming negative stiffness, which is used to offset the positive stiffness provided by the hydraulic spring 2, and realize the dynamic maintenance of the system in the quasi-zero stiffness state.

[0096] Embodiment 2

[0097] Referring to Figure 11 , the application also provides a control method of the electromagnetic quasi-zero stiffness vibration isolator as described in Embodiment 1, which precisely controls the synergistic effect of electromagnetic negative stiffness and positive stiffness by monitoring the displacement of the mover 4 in real time and dynamically adjusting the coil current of the stator unit 3, so that the system is always maintained in the quasi-zero stiffness interval, thereby realizing low-frequency vibration isolation adaptive to the load. The method specifically includes the following steps:

[0098] S1, construct an initial quasi-zero stiffness magnetic field environment:

[0099] After the system is started, the initial current is first passed to the coil winding of each stator unit 3, so that the current directions of the upper coil and the lower coil are opposite, for example, the north pole is formed at one end of the upper coil towards the mover 4, and the south pole is formed at one end of the lower coil towards the mover 4, or the reverse configuration. The polarity and size of the initial current are calibrated, so that the 12 stator units 3 (cooperatively forming a symmetrical magnetic field array of 24 magnetic poles) generate a stable magnetic field symmetrical above and below in the area where the mover 4 is located. At this time, the mover 4 made of high permeability material is suspended in the magnetic field with a preset initial air gap under the action of the magnetic field force, and maintains a safe and controllable relative position with the stator unit 3, providing a reference state for subsequent dynamic adjustment.

[0100] S2, real-time acquisition of mover 4 displacement signal:

[0101] During the operation of the vibration isolator, changes in external load (such as changes in load weight) or vibration excitation (such as low-frequency mechanical vibration) can cause the mover 4 to produce axial displacement (for example, compression or stretching relative to the initial air gap). The system collects the displacement signal of the mover 4 (including the displacement size and direction) in real time through the displacement sensor 5 fixed to the bearing platform or the connection part of the mover 4, and transmits the displacement signal to the controller (such as an H∞ controller). This step realizes the rapid perception of the state change of the system, and provides the basis for the subsequent dynamic adjustment.

[0102] S3, calculate the target current value:

[0103] After the controller receives the displacement signal collected by the displacement sensor 5, it calculates the degree of deviation of the mover 4 from the equilibrium position based on the preset control algorithm (H∞ control algorithm), and further calculates the target current value required to restore the mover 4 to the equilibrium position (i.e. the initial air gap position corresponding to the quasi-zero stiffness state). The target current value corresponds to the current size that the stator unit 3 coil winding needs to adjust to, and its calculation logic comprehensively considers the change of the air gap 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 "increasing displacement and decreasing restoring force", and the balance relationship between the positive stiffness provided by the hydraulic spring 2 and the load support demand.

[0104] S4, dynamically adjust the coil current to maintain the quasi-zero stiffness state:

[0105] The driving circuit adjusts the current size 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, and changes the magnetic field strength and the magnetic force gradient by adjusting the current intensity input to the coil winding. This adjustment process specifically shows that if the displacement sensor 5 detects that the displacement of the mover 4 is too large (for example, the air gap is reduced due to the increase of the load), the controller outputs the "increase the stator current" instruction, and the driving circuit increases the coil current to increase the magnetic field attraction force to balance the load change; if the displacement is too small (for example, the air gap is increased), the "decrease the current" instruction is output, and the magnetic field strength is reduced to avoid excessive restoring force. Through the dynamic adjustment of the electromagnetic negative stiffness (related to the mover 4-stator air gap) and the positive stiffness (provided by the hydraulic spring 2), the system can compensate for the stiffness deviation caused by the load change or excitation fluctuation in real time, and finally make the mover 4 stably maintain in the quasi-zero stiffness balance interval, ensuring that the low-frequency vibration energy is effectively suppressed.

[0106] The displacement sensor 5 collects the displacement signal of the mover 4 in real time, and the controller can quickly identify the system state deviation caused by load changes or external excitation, such as the displacement of the mover 4 from the initial air gap, and accurately calculate the target current value based on the control algorithm. The fast adjustment capability of the drive circuit enables real-time adjustment of the stator coil current, 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 the isolation performance of traditional passive vibration isolators when the load changes.

[0107] By fine control of the stator unit 3 coil current, the method can accurately adjust the magnetic field strength and magnetic force gradient between the mover 4 and the stator, thereby changing the negative stiffness. When the load increases, causing the positive stiffness to rise, the controller increases the current to enhance the negative stiffness to offset its impact; conversely, it reduces the current to reduce the negative stiffness. This dynamic compensation mechanism enables the positive and negative stiffness to always work together, and the overall stiffness of the system tends to zero (quasi-zero stiffness state), which has a significant inhibitory effect on low-frequency vibrations, improving the adaptability of the vibration isolator under complex working conditions.

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

[0109] As a preferred embodiment, the controller uses the H∞ control algorithm to calculate the target current value required to restore the mover 4 to the equilibrium position, and adjusts the current size in the stator unit 3 coil winding to change the magnetic field strength and magnetic force gradient, thereby achieving dynamic regulation 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 caused by load changes or external excitation, and to ensure stable low-frequency vibration isolation performance.

[0110] Specifically, when the vibration isolator is in operation, external load changes or low-frequency vibration excitation will cause the mover 4 to produce axial displacement, resulting in changes in the air gap between the mover 4 and the stator unit 3. The air gap change directly affects the size and characteristics of the electromagnetic force experienced by the mover 4: due to the opposite currents flowing through the upper and lower coil windings 33 of the stator unit 3 forming a symmetrical magnetic field, the magnetic attraction force experienced by the mover 4 in this magnetic field increases as the air gap decreases, but the magnetic force gradient is negative, exhibiting a "displacement increases, restoring force decreases" nonlinear characteristic, i.e., forming a nonlinear negative stiffness.

[0111] The traditional control method is difficult to realize accurate stiffness compensation when facing such nonlinear characteristics and dynamic changes of load, and is easy to cause the system to deviate from the quasi-zero stiffness interval. The embodiment effectively solves the above problems by adopting the H∞ control algorithm.

[0112] H∞ control is a robust control method, and the core goal is to optimize the control law to control the key output (such as the displacement of the mover 4) within the allowed range when facing the worst interference, while minimizing the control error and system sensitivity.

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

[0114] State perception and signal input: the displacement sensor 5 collects the displacement signal of the 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 calculate.

[0115] Target current calculation: the controller analyzes and processes the displacement signal based on the H∞ control algorithm. The H∞ control algorithm takes the displacement of the mover 4 as the input variable, and takes 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, the target current value required for the mover 4 to return to the equilibrium position (i.e. the initial air gap position corresponding to the quasi-zero stiffness) is calculated. 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 force gradient, and the interference factors introduced by the load change or external excitation.

[0116] Dynamic current regulation and magnetic field control: the driving circuit adjusts the current size of the upper coil winding 32 and the lower coil winding 33 in the stator unit 3 according to the target current value output by the controller. The change of the current directly changes the magnetic field strength and the magnetic force gradient generated by the stator unit 3, and then adjusts the size and characteristics of the electromagnetic force acting on the mover 4. When the displacement of the mover 4 is too large, the controller outputs an instruction to increase the current to increase the magnetic field attraction to balance the load change; when the displacement is too small, the output instruction reduces the current to reduce the magnetic field strength to avoid excessive restoring force.

[0117] By calculating the target current value using the H∞ control algorithm and adjusting the coil current of the stator unit 3 to change the magnetic field strength and the magnetic force gradient, dynamic regulation and control of nonlinear negative stiffness are realized. This control method can effectively solve the problem of deviation of quasi-zero stiffness caused by load change or external excitation, and improve the vibration suppression performance of the vibration isolator in the low frequency band and the robustness under complex working conditions. It is the key technical support for realizing the core function of "adapting to load changes and maintaining stable isolation" of the present application.

[0118] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural changes made according to the content of the present application specification and drawings, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. An electromagnetic quasi-zero stiffness vibration isolator, characterized by, The application relates to a vibration isolator, comprising: a base; a positive stiffness mechanism for supporting external load and providing basic positive stiffness, comprising a hydraulic spring with a bottom end arranged in the middle of the base; a negative stiffness mechanism in parallel with the positive stiffness mechanism for generating nonlinear negative stiffness to offset the positive stiffness, comprising a plurality of stator units distributed in an annular 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 penetrates 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; a positive and negative stiffness connecting mechanism arranged between the hydraulic spring and the mover for realizing displacement transmission and cooperative adjustment; 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 being used for collecting load displacement signals, and the controller being used for adjusting the excitation current of the stator units according to the displacement signals to adjust the electromagnetic force so that the vibration isolator is maintained in a quasi-zero stiffness interval.

2. The electromagnetic quasi-zero stiffness vibration isolator according to claim 1, characterized in that, The stator unit comprises a stator support, an upper coil winding and a lower coil winding arranged on the stator support from top to bottom, and a preset space is formed between the upper and lower coil windings; opposite currents are input into the upper and lower coil windings of the stator unit to form a magnetic field which is symmetrically distributed upwards and downwards in the area of the mover.

3. The electromagnetic quasi-zero stiffness vibration isolator according to claim 2, wherein, The plurality of 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.

4. An electromagnetic quasi-zero stiffness vibration isolator according to claim 2 or 3, wherein The mover comprises a ring-shaped plate and a connecting pipe arranged on the upper surface of the ring-shaped plate, the outer edge of the ring-shaped plate extends into the preset space of the stator unit, and the electromagnetic force borne by the ring-shaped plate changes with the change of the air gap between the stator unit and the mover, thereby forming a negative stiffness characteristic.

5. The electromagnetic quasi-zero stiffness vibration isolator according to claim 4, wherein, 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; one end of each pneumatic spring is connected with the hydraulic spring, and the other end is connected with the top of the connecting pipe of the mover.

6. The electromagnetic quasi-zero stiffness vibration isolator according to claim 5, wherein, 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.

7. The electromagnetic quasi-zero stiffness vibration isolator according to any one of claims 1-3, wherein The hydraulic spring comprises an elastomer chamber and a liquid flow channel, when the vibration isolator is subjected to load and displacement, the elastomer chamber provides a positive restoring force which increases with displacement, and the liquid flows through the flow channel to generate damping effect.

8. The electromagnetic quasi-zero stiffness vibration isolator according to claim 2 or 3, characterized in that 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.

9. A method of controlling an electromagnetic quasi-zero stiffness vibration isolator according to any one of claims 1 to 8, characterized in that, The application further discloses a vibration isolation method, comprising the following steps: initial currents are input into the coil windings of the stator units to construct an upward and downward symmetric magnetic field array, so that the mover is suspended with an initial air gap under the action of the magnetic field force; the displacement sensor is used for collecting mover displacement signals caused by external load change or vibration excitation in real time; the controller calculates a target current value required for the mover to return to the equilibrium position based on the displacement signals; and the target current value is input into the coil windings of the stator units to adjust the electromagnetic force of the mover. The driving circuit adjusts the current size in each coil winding in the stator unit, changes the electromagnetic negative stiffness and positive stiffness synergy, compensates the stiffness deviation caused by load change, and makes the system keep in the quasi-zero stiffness state.

10. The control method according to claim 9, characterized by, The controller calculates the required target current value by using H∞ control algorithm, changes the magnetic field intensity and magnetic force gradient by adjusting the current, and realizes the dynamic regulation and control of the nonlinear negative stiffness.

Images