Rigidity-adaptive three-degree-of-freedom low-frequency electromagnetic vibration isolator

Abstract

The invention discloses a rigidity-adaptive three-degree-of-freedom low-frequency electromagnetic vibration isolator, and belongs to the technical field of precise vibration isolation. The rigidity-adaptive three-degree-of-freedom low-frequency electromagnetic vibration isolator comprises three sets of low-frequency electromagnetic vibration isolators formed by connecting rigidity-adaptive electromagnetic arrays and spiral springs in parallel. The spiral spring stably supports the load in a passive mode and effectively isolates vibration of middle and high frequency bands; the rigidity self-adaptive electromagnetic array generates high negative rigidity through a moving magnetic array and a fixed magnetic array which are composed of four columns of vertically magnetized equal-cross-section cubic permanent magnets, coil current is adjusted in real time through acceleration feedback, external excitation and load mass changes are responded, the negative rigidity is dynamically adjusted, and the requirement for three-degree-of-freedom near-full-band vibration isolation is met. The vibration isolator has adjustable low dynamic rigidity in the vertical and horizontal rotation freedom degrees, the vibration isolation frequency is low, the frequency band is wide, a super-quiet environment is provided for tip equipment, and the instrument precision is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of precision vibration isolation, in particular to a three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness. Background Art

[0002] Low-frequency micro-vibration in the environment has become one of the key factors restricting the assembly, debugging, testing and experimental accuracy improvement of precision instruments and equipment. In response to this problem, configuring low-frequency vibration isolators for precision equipment has become the dominant technical solution in the field of ultra-precision engineering to suppress external micro-vibration interference. Due to its inherent "low-pass filtering" characteristics, the vibration isolator can only effectively attenuate vibrations greater than 1.414 times the natural frequency. For vibrations with frequencies below this threshold, the vibration isolator not only fails to play an attenuation role, but also has an amplification effect. In order to expand the vibration isolation bandwidth, reducing the natural frequency is the key. Reducing stiffness is one way to reduce the natural frequency. The low-frequency vibration originally in the amplification zone can be included in the attenuation zone, thereby significantly improving the attenuation effect of the vibration isolator on the low-frequency vibration.

[0003] Electromagnetic negative stiffness devices are used to build low-frequency vibration isolation systems in parallel with vibration isolators due to their advantages of no mechanical friction, compact structure, adjustable stiffness, and dynamic matching of load and excitation frequency changes. However, due to the limitation of parallel magnetization (same or opposite direction) of the magnetic array structure, the utilization rate of the magnetic field is not high, resulting in limited negative stiffness values, making it difficult to completely offset the bearing stiffness of the vibration isolator, hindering a significant reduction in the natural frequency, and limiting the expansion of the vibration isolation bandwidth. Therefore, when the frequency of the micro-vibration disturbance is lower than 1.414 times the natural frequency, the system is in or close to a resonant state, the response to the vibration disturbance is significantly enhanced, and the amplitude increases sharply, which may cause a series of problems including impaired system stability, structural fatigue, damage, and overall performance degradation. These problems may have serious consequences in many fields such as ultra-precision machining, measurement, and precision experiments.

[0004] In addition, current research focuses on single-degree-of-freedom low-frequency vibration isolation problems. Single-degree-of-freedom systems are relatively simple and easy to analyze and verify theoretically. However, in the field of multi-degree-of-freedom vibration isolation, especially three-degree-of-freedom vibration isolation, which is closer to practical applications, related research is still insufficient. The three-degree-of-freedom system can more realistically reflect the complex vibration conditions in actual engineering, including vibration coupling in different directions, nonlinear effects, etc. Therefore, in-depth research on the stiffness control mechanism in the three-degree-of-freedom vibration isolation system and exploring innovative variable stiffness technology to meet the needs of three-degree-of-freedom vibration isolation are of vital importance to improving the high standards of vibration isolation performance of precision instruments and equipment.

[0005] Patent No. 201811101215.7 discloses an electromagnetic six-degree-of-freedom variable stiffness vibration isolation system consisting of an upper plate, a base plate and six electromagnetic vibration isolation units. The electromagnetic vibration isolation unit includes a permanent magnet and an electromagnetic coil arranged outside the permanent magnet. By changing the number of layers of the permanent magnet and the coil and adjusting the size of the power supply current, the magnetic field strength and the distribution of magnetic induction lines generated by the electromagnetic coil are changed, thereby generating an adjustable negative stiffness characteristic, adjusting the stiffness of the coil spring, reducing the natural frequency, and expanding the vibration isolation bandwidth. The technical solution is characterized by: 1) the adjustable negative stiffness characteristic is realized by combining a permanent magnet and a coil. During the working process, energy needs to be continuously input into the coil to generate an electromagnetic force in the same direction as the motion displacement, and the system has high energy consumption; 2) the permanent magnet is uniformly magnetized, resulting in the excitation magnetic field generated by it being used only on one side close to the electromagnetic coil, and the other side is idle, the magnetic field utilization rate is low, and the negative stiffness value generated is limited, which is not effective in reducing the natural frequency of heavy load or high-frequency vibration isolation systems.

[0006] Patent No. 202011189262.9 discloses a three-degree-of-freedom micro-vibration isolation device based on an active electromagnetic negative stiffness structure. The active electromagnetic negative stiffness structure uses a coaxially nested double magnetic ring structure to produce a negative stiffness characteristic with unadjustable stiffness in the vertical direction, and uses a powered coil coaxially nested with the double magnetic ring negative stiffness structure to generate a precisely controllable excitation flux, changing the bias magnetic field around the moving magnetic ring, thereby achieving the adjustment of the negative stiffness value to adapt to changes in the mass of the vibration isolation load and the excitation frequency. The technical solution is characterized in that: 1) The bias magnetic field is provided by the fixed magnetic ring, and only a small current is required in the coil to generate the excitation flux to adjust the bias magnetic field without the need for continuous high energy input, and the system energy consumption is low. 2) The coaxially nested double magnetic rings use axial unidirectional magnetization to form a symmetrical excitation magnetic field on the inner and outer sides of the magnetic ring. However, only the magnetic field on the outside of the inner magnetic ring is utilized, while the magnetic field on the inside is idle. This design has low magnetic field utilization and generates limited negative stiffness. When it comes to vibration isolation systems with large loads and high natural frequencies, its stiffness control effect is minimal, and it is impossible or difficult to achieve low-frequency, ultra-low-frequency, or even near-zero-frequency vibration isolation effects.

[0007] In summary, the innovative vibration isolation structure and principle, the development of a three-degree-of-freedom micro-vibration isolator with adaptive vibration isolation stiffness, can instantly sense the change of load mass and the fluctuation of external excitation frequency, and dynamically adjust the negative stiffness value accordingly, so as to accurately match the needs of three-degree-of-freedom near-full-band vibration isolation, thereby incorporating external low-frequency micro-vibration excitation from the amplification zone into the attenuation zone, which is crucial for effectively shielding the negative impact of environmental micro-vibration on precision instruments and equipment. This innovation will create a more stable and reliable environment for high-precision assembly debugging, testing and experimental work, and significantly improve the accuracy level of precision instruments and equipment. Summary of the invention

[0008] The present invention aims to solve the problem that the existing electromagnetic negative stiffness structure is limited by the parallel magnetization design of the magnetic array, the negative stiffness generated is limited, and it is difficult to match the stiffness parameters of the three-degree-of-freedom near-full-band vibration isolation. A three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness is proposed, which is composed of an adaptive stiffness electromagnetic array and a coil spring in parallel. The coil spring stably supports the load in a passive manner and effectively isolates the vibration in the medium and high frequency bands; while the dynamic magnetic array and the fixed magnetic array of the adaptive stiffness electromagnetic array generate high negative stiffness characteristics through four rows of vertically magnetized cubic permanent magnets of equal cross-section, and respond instantly to changes in the external excitation frequency, and adjust the negative stiffness value by regulating the coil current through acceleration feedback to match the stiffness parameters of the three-degree-of-freedom near-full-band vibration isolation, thereby incorporating the external low-frequency micro-vibration excitation from the amplification zone into the attenuation zone. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness has adjustable low dynamic stiffness characteristics in the vertical translation and horizontal rotation degrees of freedom, and has a low vibration isolation frequency and a wide vibration isolation frequency band.

[0009] The technical solution of the present invention is:

[0010] The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness can accurately adapt to the changes in the excitation frequency and the load mass, generate adjustable high negative stiffness characteristics in real time, effectively adjust the vibration isolation frequency, and realize three-degree-of-freedom low-frequency vibration isolation; it is characterized in that it includes a load platform, a substrate and three sets of low-frequency electromagnetic vibration isolators connecting the two, the load platform has the degree of freedom of translation along the vertical z-axis and the degree of freedom of rotation around the horizontal x and y axes relative to the substrate, the top of each set of low-frequency electromagnetic vibration isolators is connected to the fixing part at the bottom of the load platform through an upper flexible hinge, and the connection points are evenly distributed on the load platform at intervals of 120° along the circumference; the bottom of each set of low-frequency electromagnetic vibration isolators is connected to the fixing part at the top of the substrate through a lower flexible hinge, and the connection points are evenly distributed on the substrate at intervals of 120° along the circumference; it is characterized in that the low-frequency electromagnetic vibration isolator is composed of a stiffness adaptive electromagnetic array and a coil spring in parallel, and the stiffness adaptive electromagnetic array includes a dynamic magnetic array, a dynamic magnetic array mounting part, a fixed magnetic array, a fixed magnetic array fixing part, a coil, an upper working The moving part, the lower moving part, the sensor, the signal conditioner, the collector, the controller and the driver have an overall structure that is not only symmetrical about the center, but also axially symmetrical in the front-back and left-right directions; the moving magnetic array mounting part is a cubic structure, the top of which is fixedly connected to the upper moving part, and a square boss is arranged at the bottom, and an annular groove is arranged in the boss; the top of the spiral spring is coaxially fixedly installed in the annular groove at the bottom of the moving magnetic array mounting part, and the bottom is coaxially fixedly installed in the annular groove on the bottom surface of the fixed magnetic array fixing part; the moving magnetic array mounting part is nested in the fixed magnetic array fixing part in such a way that the center line coincides with the axis of symmetry, and the four sides of the two are parallel to each other; the fixed magnetic array fixing part is a square sleeve, and the four inner sides thereof are arranged with cubic deep grooves of the same size, and an annular groove is arranged on the bottom surface; the top of the fixed magnetic array fixing part maintains a certain gap with the upper flexible hinge in the vertical direction, and the bottom is fixedly connected with the lower moving part; the moving magnetic array and the fixed magnetic array both include four rows of permanent magnets, and each row of permanent magnets consists of 2n+1(n≥1, n∈N +) layers of array arrangement, adjacent layers of perpendicular magnetization of equal cross-section cubic permanent magnets, and the odd number of layers of permanent magnets are of equal height, and the even number of layers of permanent magnets are of equal height; the four rows of permanent magnets of the moving magnetic array are respectively fixedly mounted on the four side surfaces of the moving magnetic array mounting piece, and keep the same gap with the four inner side surfaces of the fixed magnetic array mounting piece; the four rows of permanent magnets of the fixed magnetic array are respectively fixedly mounted in the deep grooves of the four inner side surfaces of the fixed magnetic array mounting piece, and keep the same gap with the four outer side surfaces of the moving magnetic array mounting piece; the four rows of permanent magnets of the moving magnetic array and the fixed magnetic array are provided with the same gap along the horizontal direction; the first layer of permanent magnets of the moving magnetic array and the fixed magnetic array are arranged in the horizontal direction. The coils are wound into a rectangle and fixedly mounted on the outer side of the fixed magnetic array fixture in an equidistant array. The coils are connected to the output end of the driver, and the input end of the driver is connected to the output end of the controller through a serial port or a network. The controller integrates a control algorithm based on acceleration feedback, and its input end reads the information of the collector through a serial port or a network. The input end of the collector is connected to the output end of the signal conditioner, and the input end of the signal conditioner is connected to the sensor.

[0011] Preferably, the bottom surface of the first layer of permanent magnets in the moving magnetic array overlaps with the bottom surface of the first layer of permanent magnets in the fixed magnetic array.

[0012] Preferably, the height of the coil is equal to the height of the fixed magnetic array, and is symmetrical about the vertical height center of the fixed magnetic array.

[0013] Preferably, the fixed magnetic array fixing part, the dynamic magnetic array mounting part, the upper actuator, the lower actuator, the upper flexible hinge, the lower flexible hinge and the coil spring are made of non-magnetic or weakly magnetic aluminum alloy, titanium alloy or austenitic stainless steel.

[0014] Preferably, the driver is a linear regulator, a linear driver, a switching regulator or a switching driver.

[0015] Preferably, the signal conditioner includes an amplifier and a filter, the gain and bandwidth of the amplifier are adjustable, the filter can realize a high-pass filtering function, and its cut-off frequency is adjustable.

[0016] The technical innovation and good effects of the present invention are:

[0017] (1) The present invention innovatively proposes a stiffness adaptive electromagnetic array with zero magnetic force and adjustable high negative stiffness characteristics. The present invention uses four-column multi-layer array arrangement and equal-cross-section cubic permanent magnets to form a dynamic magnetic array and a fixed magnetic array, respectively. Through the design of vertical magnetization between adjacent layers, a unilateral high-density excitation magnetic field with high negative stiffness characteristics is constructed; and by finely controlling the current size and direction of the coil installed on the outer side of the fixed magnetic array fixture, the precise controllability of the excitation flux, the dynamic adjustability of the bias magnetic field and the negative stiffness value are ensured, and the dual optimization of zero magnetic force and adjustable high negative stiffness characteristics is achieved; not only the magnetic field strength on the non-working side is weakened, and unnecessary magnetic field interference is reduced; at the same time, an adjustable high excitation magnetic field is generated on the working side, which is one of the innovative points that distinguish the present invention from the prior art.

[0018] (2) The present invention can operate stably in complex and changeable working environments, and can adapt to changes in the mass of the micro-vibration isolation load and the excitation frequency. By using acceleration feedback to regulate the driving current in the coil and accurately controlling the negative stiffness value, the dynamic characteristics adjustment of the vibration isolation system caused by load changes can be effectively responded to, thereby preventing potential instability and performance degradation. At the same time, when the external excitation frequency changes, the vibration isolation frequency can be actively adjusted to effectively transfer the external low-frequency micro-vibration excitation from the amplification area to the attenuation area, thereby avoiding the resonance area; this feature ensures that the vibration isolation system is free from interference from the resonance phenomenon, and consolidates the long-term stable operation and high reliability of the vibration isolation system. This is the second innovation that distinguishes the present invention from the prior art.

[0019] (3) The present invention can achieve stiffness control of precision micro-vibration isolation in multiple degrees of freedom, expand the vibration isolation bandwidth, and provide a "super-quiet" working environment for cutting-edge instruments and equipment, thereby effectively promoting a leap-forward improvement in the accuracy of precision instruments and equipment. The coil spring ensures stable support of the load in a passive manner and effectively isolates vibrations in the medium and high frequency bands; the stiffness adaptive electromagnetic array adopts a composite active and passive magnetic levitation method to produce an adjustable high negative stiffness characteristic, which can effectively reduce the natural frequency of vibration isolation without changing the bearing capacity of the coil spring, and further broaden the vibration isolation bandwidth; in addition, through a carefully designed layout, three sets of low-frequency electromagnetic vibration isolators consisting of a stiffness adaptive electromagnetic array and a coil spring in parallel are cleverly connected in parallel and deployed, achieving high-performance micro-vibration isolation in the three degrees of freedom of the vertical direction and around the horizontal x and y axes. This is the third innovation of the present invention that distinguishes it from the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The three-dimensional model of the three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness;

[0021] Figure 2 It is a schematic diagram of the arrangement of three sets of low-frequency electromagnetic vibration isolators;

[0022] Figure 3The top view of the three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness;

[0023] Figure 4 AA section view of the three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness;

[0024] Figure 5 It is a front cross-sectional view of a low-frequency electromagnetic vibration isolator;

[0025] Figure 6 It is a three-dimensional cross-sectional schematic diagram of a low-frequency electromagnetic vibration isolator.

[0026] Explanation of the part numbers in the figure: 1 moving magnetic array, 2 moving magnetic array mounting part, 3 fixed magnetic array, 4 fixed magnetic array fixing part, 5 coil, 61 upper actuator, 62 lower actuator, 7 spiral spring, 81 upper flexible hinge, 82 lower flexible hinge, 9 load platform, 10 substrate, 11 stiffness adaptive electromagnetic array, 12 fixing part, 13 low frequency electromagnetic vibration isolator, 14 sensor, 15 signal conditioner, 16 collector, 17 controller, 18 driver. DETAILED DESCRIPTION

[0027] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0028] The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness can accurately adapt to the changes in the excitation frequency and the load mass, generate adjustable high negative stiffness characteristics in real time, effectively adjust the vibration isolation frequency, and realize three-degree-of-freedom low-frequency vibration isolation; it is characterized by: comprising a load platform 9, a substrate 10 and three sets of low-frequency electromagnetic vibration isolators 13 connecting the two, the load platform 9 has the degree of freedom of translation along the vertical z-axis and the degree of freedom of rotation around the horizontal x and y axes relative to the substrate 10, the top of each set of low-frequency electromagnetic vibration isolators 13 is connected to the solid at the bottom of the load platform 9 through the upper flexible hinge 81 The fixed part 12 is connected, and the connection points are evenly distributed at intervals of 120° along the circumference on the load platform 9; the bottom of each set of low-frequency electromagnetic vibration isolators 13 is connected to the fixed part 12 on the top of the substrate 10 through the lower flexible hinge 82, and the connection points are evenly distributed at intervals of 120° along the circumference on the substrate 10; it is characterized in that: the low-frequency electromagnetic vibration isolator 13 is composed of a stiffness adaptive electromagnetic array 11 and a coil spring 7 in parallel, and the stiffness adaptive electromagnetic array 11 includes a dynamic magnetic array 1, a dynamic magnetic array mounting part 2, a fixed magnetic array 3, a fixed magnetic array fixing part 4, a coil 5, the upper actuator 61, the lower actuator 62, the sensor 14, the signal conditioner 15, the collector 16, the controller 17 and the driver 18, the overall structure is not only symmetrical about the center, but also axially symmetrical in the front-back and left-right directions; the moving magnetic array mounting member 2 is a cubic structure, the top of which is fixedly connected to the upper actuator 61, and the bottom is provided with a square boss, and an annular groove is provided in the boss; the top of the coil spring 7 is coaxially fixedly installed in the annular groove at the bottom of the moving magnetic array mounting member 2, and the bottom is coaxially fixedly installed in the fixed magnetic array mounting member 4 The bottom surface is annularly grooved; the dynamic magnetic array mounting member 2 is nested in the fixed magnetic array fixing member 4 in such a way that the center line coincides with the axis of symmetry, and the four sides of the two are parallel to each other; the fixed magnetic array fixing member 4 is a square sleeve, and the four inner sides thereof are provided with cubic deep grooves of the same size, and the bottom surface is provided with an annular groove; the top of the fixed magnetic array fixing member 4 maintains a certain gap with the upper flexible hinge 81 in the vertical direction, and the bottom is fixedly connected with the lower actuator 62; the dynamic magnetic array 1 and the fixed magnetic array 3 both include four rows of permanent magnets, and each row of permanent magnets consists of 2n+1 (n≥1, n∈N +) layers of array arrangement, adjacent layers of cubic permanent magnets with equal cross-sections and perpendicular magnetization, and the heights of the odd-numbered layers of permanent magnets are equal, and the heights of the even-numbered layers of permanent magnets are equal; the four rows of permanent magnets of the moving magnetic array 1 are respectively fixedly mounted on the four side surfaces of the moving magnetic array mounting member 2, and maintain the same gap with the four inner side surfaces of the fixed magnetic array mounting member 4; the four rows of permanent magnets of the fixed magnetic array 3 are respectively fixedly mounted in the deep grooves of the four inner side surfaces of the fixed magnetic array mounting member 4, and the deep grooves of the four inner side surfaces maintain the same gap with the four outer side surfaces of the moving magnetic array mounting member 2; the four rows of permanent magnets of the moving magnetic array 1 and the fixed magnetic array 3 are provided with the same gap in the horizontal direction; the first layer of permanent magnets of the moving magnetic array 1 and the fixed magnetic array 3 are arranged in the horizontal direction. Reverse magnetization, on the right half of the front section view, with each additional layer, the magnetization direction of the moving permanent magnet rotates 90° clockwise, and the magnetization direction of the fixed permanent magnet rotates 90° counterclockwise; the coil 5 is wound into a rectangle and fixedly mounted on the outer side of the fixed magnetic array fixture 4 in an equidistant array, the coil 5 is connected to the output end of the driver 18, the input end of the driver 18 is connected to the output end of the controller 17 through a serial port or a network, the controller 17 integrates a control algorithm based on acceleration feedback, and its input end reads the information of the collector 16 through a serial port or a network, the input end of the collector 16 is connected to the output end of the signal conditioner 15, and the input end of the signal conditioner 15 is connected to the sensor 14.

[0029] As a specific implementation, the bottom surface of the first layer of permanent magnets in the moving magnetic array 1 coincides with the bottom surface of the first layer of permanent magnets in the fixed magnetic array 3 .

[0030] As a specific implementation manner, the height of the coil 5 is equal to the height of the fixed magnetic array 3 , and is symmetrical about the vertical height center of the fixed magnetic array 3 .

[0031] As a specific implementation, the fixed magnetic array fixing part 4, the dynamic magnetic array mounting part 2, the upper actuator 61, the lower actuator 62, the upper flexible hinge 81, the lower flexible hinge 82 and the coil spring 7 are made of non-magnetic or weakly magnetic aluminum alloy, titanium alloy or austenitic stainless steel.

[0032] As a specific implementation, the driver 18 is a linear regulator, a linear driver, a switching regulator or a switching driver.

[0033] As a specific implementation, the signal conditioner 15 includes an amplifier and a filter. The gain and bandwidth of the amplifier are adjustable. The filter can realize a high-pass filtering function, and its cut-off frequency is adjustable.

[0034] Combine the following Figure 1 to Figure 6 An embodiment of the present invention is given.

[0035] The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness includes a load platform 9, a base plate 10, and three sets of low-frequency electromagnetic vibration isolators 13 connecting the two. The load platform 9 has the degree of freedom of translation along the vertical z axis and the degree of freedom of rotation around the horizontal x and y axes relative to the base plate 10. The top of each set of low-frequency electromagnetic vibration isolators 13 is connected to the fixing member 12 at the bottom of the load platform 9 through four threaded holes evenly distributed on the upper flexible hinge 81, and the connection points are evenly distributed on the load platform 9 at intervals of 120° along the circumference; the bottom of each set of low-frequency electromagnetic vibration isolators 13 is connected to the fixing member 12 at the top of the base plate 10 through four threaded holes evenly distributed on the lower flexible hinge 82, and the connection points are evenly distributed on the base plate 10 at intervals of 120° along the circumference.

[0036] Each set of low-frequency electromagnetic vibration isolators 13 is composed of a stiffness adaptive electromagnetic array 11 and a coil spring 7 in parallel. The stiffness adaptive electromagnetic array 11 includes a dynamic magnetic array 1, a dynamic magnetic array mounting 2, a fixed magnetic array 3, a fixed magnetic array fixing 4, a coil 5, an upper actuator 61, a lower actuator 62, a sensor 14, a signal conditioner 15, a collector 16, a controller 17 and a driver 18. The overall structure is not only symmetrical about the center, but also axially symmetrical in the front and back and left and right directions. The dynamic magnetic array mounting 2 is a cubic structure made of 7075 aluminum alloy. Its top is fixedly connected to the upper actuator 61, and a square boss is set at the bottom, and an annular groove is set in the boss. The positive stiffness characteristics of the coil spring 7 are used to stably support the vibration isolation load. Its top is coaxially fixedly installed in the annular groove at the bottom of the dynamic magnetic array mounting 2, and the bottom is coaxially fixedly installed in the annular groove on the bottom surface of the fixed magnetic array fixing 4. The dynamic magnetic array mounting part 2 is nested in the fixed magnetic array fixing part 4 in such a way that the center line coincides with the axis of symmetry, and the four sides of the two are parallel to each other; the fixed magnetic array fixing part 4 is a square sleeve made of high electrical conductivity and high magnetic permeability metal materials such as copper, aluminum, iron, and nickel, and its four inner sides are provided with cubic deep grooves of the same size, and the bottom is provided with an annular groove; the top of the fixed magnetic array fixing part 4 maintains a certain gap with the upper flexible hinge 81 in the vertical direction, and the bottom is fixedly connected to the lower actuator 62.

[0037] The moving magnetic array 1 and the fixed magnetic array 3 both include four rows of permanent magnets, each row of permanent magnets consists of 2n+1 (n≥1, n∈N + ) layers are arranged in an array and the adjacent layers are perpendicularly magnetized. The permanent magnets are all N44H brand Ru-Fe-B, with a remanence of 13.54 kGs, an intrinsic coercive force of 12.66 kOe, and a relative magnetic permeability of μ r=1.23. The length and width of the moving magnetic array 1 are 30mm and 55mm respectively, and the heights of the odd-numbered and even-numbered layers of moving magnets are 20mm and 34mm respectively. The horizontal gap between the moving magnetic array 1 and the fixed magnetic array 3 is 6mm, the length and width of the fixed magnetic array 3 are 35mm and 65mm respectively, and the heights of the odd-numbered and even-numbered layers of fixed magnets are 20mm and 34mm respectively. The four columns of permanent magnets of the moving magnetic array 1 are fixedly mounted on the four side surfaces of the moving magnetic array mounting part 2, respectively, and maintain the same gap with the four inner side surfaces of the fixed magnetic array fixing part 4; the four columns of permanent magnets of the fixed magnetic array 3 are fixedly mounted in the deep grooves of the four inner side surfaces of the fixed magnetic array fixing part 4, respectively, and maintain the same gap with the four outer side surfaces of the moving magnetic array mounting part 2.

[0038] The first layer of permanent magnets of the moving magnetic array 1 and the fixed magnetic array 3 are magnetized in the opposite direction in the horizontal direction. On the right half of the front cross-sectional view, with each additional layer, the magnetization direction of the moving permanent magnet rotates 90° clockwise, and the magnetization direction of the fixed permanent magnet rotates 90° counterclockwise. The coil 5 is wound into a rectangle and fixedly mounted on the outer side of the fixed magnetic array fixture 4 in an equidistant array, and its height is equal to the height of the moving magnetic array 1. A precisely controllable driving current generated by a linear regulator, a linear driver, a switching regulator or a switching driver is passed into the coil 5. The magnitude and direction of the current are adaptively adjusted by the controller 17 that integrates the control algorithm based on acceleration feedback according to the load mass and the frequency of external micro-vibration interference. Specifically, when the load mass increases, the controller 17 will increase the current in the coil 5 to enhance the repulsive force of the stiffness adaptive electromagnetic array 11, thereby providing a greater negative stiffness to balance the increased load mass, thereby ensuring that the vibration isolation system can still achieve high vibration isolation performance and nearly full-band vibration isolation bandwidth under a larger load mass. In addition, when the excitation frequency is reduced to a level close to or lower than the natural frequency of the precision micro-vibration isolation, the controller 17 will adjust the magnitude and direction of the current flowing through the coil 5 to enhance the negative stiffness value of the stiffness adaptive electromagnetic array 11, effectively reduce the natural frequency of the precision micro-vibration isolation, avoid the resonance area, ensure that the vibration isolation system is free from resonance interference, and ensure its long-term stable operation and high reliability.

[0039] Since the number of layers of the moving magnetic array 1 and the fixed magnetic array 3 satisfies 2n+1 (n≥1, n∈N +), the overall structure is symmetrical about the n+1th layer of permanent magnets. Therefore, the magnetic force on the moving magnetic array 1 is zero and is in a state of equilibrium. When the load platform 9 vibrates up and down due to vibration interference, it will drive the moving magnetic array 1 to produce relative movement relative to the unilateral high magnetic density excitation magnetic field generated by the fixed magnetic array 3. At this time, the axial equilibrium state of the fixed magnetic array 3 is broken, while the radial equilibrium is still balanced. The vertical magnetic force of the moving magnetic array 1 on the fixed magnetic array 3 is in the same direction as the vibration, causing it to continue to move away from the equilibrium position. Without external force, the balance cannot be restored. That is, the vertical magnetic force of the stiffness adaptive electromagnetic array 11 presents a negative stiffness characteristic. When it is connected in parallel with the coil spring 7 to support the load platform 9, the stiffness adaptive electromagnetic array 11 does not affect the load-bearing capacity of the coil spring 7. It only regulates its vibration isolation bandwidth by generating a negative stiffness characteristic, thereby improving the vibration isolation performance.

Claims

1. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness can accurately adapt to the changes in excitation frequency and load mass, generate adjustable high negative stiffness characteristics in real time, effectively adjust the vibration isolation frequency, and realize three-degree-of-freedom low-frequency vibration isolation; its characteristics are: The invention comprises a load platform (9), a base plate (10) and three sets of low-frequency electromagnetic vibration isolators (13) connecting the two. The load platform (9) has the degree of freedom of translation along the vertical z axis and the degree of freedom of rotation around the horizontal x and y axes relative to the base plate (10). The top of each set of low-frequency electromagnetic vibration isolators (13) is connected to a fixing member (12) at the bottom of the load platform (9) via an upper flexible hinge (81), and the connection points are evenly distributed on the load platform (9) at intervals of 120 degrees along the circumference. The bottom of each set of low-frequency electromagnetic vibration isolators (13) is connected to the base plate via a lower flexible hinge (82). (10) is connected to a fixing member (12) at the top, and the connection points are evenly distributed on the substrate (10) at intervals of 120° along the circumference; it is characterized in that: the low-frequency electromagnetic vibration isolator (13) is composed of a stiffness adaptive electromagnetic array (11) and a coil spring (7) in parallel, and the stiffness adaptive electromagnetic array (11) includes a dynamic magnetic array (1), a dynamic magnetic array mounting member (2), a fixed magnetic array (3), a fixed magnetic array fixing member (4), a coil (5), an upper actuator (61), a lower actuator (62), a sensor (14), a signal conditioner (15), The overall structure of the collector (16), controller (17) and driver (18) is not only symmetrical about the center, but also axially symmetrical in the front-back and left-right directions; the moving magnetic array mounting member (2) is a cubic structure, the top of which is fixedly connected to the upper actuator (61), and the bottom is provided with a square boss, and an annular groove is provided in the boss; the top of the coil spring (7) is coaxially fixedly installed in the annular groove at the bottom of the moving magnetic array mounting member (2), and the bottom is coaxially fixedly installed in the annular groove on the bottom surface of the fixed magnetic array mounting member (4); the moving magnetic array mounting member (2) The fixed magnetic array fixing member (4) is nested in a manner that the center line and the axis of symmetry coincide with each other, and the four side surfaces of the two are parallel to each other and maintain the same gap; the fixed magnetic array fixing member (4) is a square sleeve, and the four inner side surfaces thereof are provided with cubic deep grooves of the same size, and the bottom surface is provided with an annular groove; the top of the fixed magnetic array fixing member (4) and the upper flexible hinge (81) maintain a certain gap in the vertical direction, and the bottom is fixedly connected to the lower actuator (62); the dynamic magnetic array (1) and the fixed magnetic array (3) both include four rows of permanent magnets, and each row of permanent magnets consists of 2n+1 (n≥1, n∈N + ) layers of array arrangement, adjacent layers of cubic permanent magnets of equal cross-section and perpendicular magnetization, the odd-numbered layers of permanent magnets have the same height, and the even-numbered layers of permanent magnets have the same height; the four rows of permanent magnets of the moving magnetic array (1) are respectively fixedly mounted on the four side surfaces of the moving magnetic array mounting member (2), and maintain the same gap with the four inner side surfaces of the fixed magnetic array mounting member (4); the four rows of permanent magnets of the fixed magnetic array (3) are respectively fixedly mounted in the deep grooves of the four inner side surfaces of the fixed magnetic array mounting member (4), and maintain the same gap with the four outer side surfaces of the moving magnetic array mounting member (2); the four rows of permanent magnets of the moving magnetic array (1) and the fixed magnetic array (3) are provided with the same gap in the horizontal direction; the first layer of permanent magnets of the moving magnetic array (1) and the fixed magnetic array (3) are magnetized in opposite directions in the horizontal direction, On the right half of the front cross-sectional view, with each additional layer, the magnetization direction of the moving permanent magnet rotates 90° clockwise, and the magnetization direction of the fixed permanent magnet rotates 90° counterclockwise; the coil (5) is wound into a rectangle and fixedly mounted on the outer side of the fixed magnetic array fixing member (4) in an equidistant array manner; the coil (5) is connected to the output end of the driver (18); the input end of the driver (18) is connected to the output end of the controller (17) via a serial port or a network; the controller (17) integrates a control algorithm based on acceleration feedback; its input end reads information from the collector (16) via a serial port or a network; the input end of the collector (16) is connected to the output end of the signal conditioner (15); and the input end of the signal conditioner (15) is connected to the sensor (14).

2. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness according to claim 1, characterized in that: The bottom surface of the first layer of permanent magnets in the moving magnetic array (1) overlaps with the bottom surface of the first layer of permanent magnets in the fixed magnetic array (3).

3. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness according to claim 1, characterized in that: The height of the coil (5) is equal to the height of the fixed magnetic array (3), and is symmetrical about the vertical height center of the fixed magnetic array (3).

4. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness according to claim 1, characterized in that: The fixed magnetic array fixing member (4), the dynamic magnetic array mounting member (2), the upper actuator (61), the lower actuator (62), the upper flexible hinge (81), the lower flexible hinge (82) and the coil spring (7) are made of non-magnetic or weakly magnetic aluminum alloy, titanium alloy or austenitic stainless steel.

5. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness according to claim 1, characterized in that: The driver (18) is a linear regulator, a linear driver, a switching regulator or a switching driver.

6. The three-degree-of-freedom low-frequency electromagnetic vibration isolator with adaptive stiffness according to claim 1, characterized in that: The signal conditioner (15) comprises an amplifier and a filter. The gain and bandwidth of the amplifier are adjustable. The filter can realize a high-pass filtering function and its cut-off frequency is adjustable.

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