An excitation frequency adaptive vibration isolator

Abstract

The application relates to a kind of excitation frequency adaptive vibration isolators, belonging to the technical field of vibration isolation.The two steel spiral springs of the vibration isolator are connected in parallel to form a positive stiffness mechanism, the coil winding and the annular permanent magnet form an electromagnetic negative stiffness mechanism in repulsion configuration, and are connected in parallel with the two steel spiral springs, and negative stiffness is introduced by energizing the coil;The upper substrate and the lower substrate are each provided with a linear bearing at the center shaft for ensuring the coaxiality of the frame and the center shaft.The application can measure and record the displacement response signal of the system in real time, calculate the external excitation frequency acting on the system online through a frequency discriminator, adjust the current in the electromagnetic device according to the result, and then adjust the equivalent stiffness of the system, realize the flexible switching of linear system and high static low dynamic system, solve the problem of limited vibration isolation frequency band of traditional linear vibration isolator and the problem of low-frequency vibration amplification of existing high static low dynamic vibration isolation system, realize efficient isolation of medium and high frequency domain vibration and effective improvement of low-frequency vibration amplification problem.

Description

Technical Field

[0001] This invention belongs to the field of vibration isolation technology, specifically relating to an excitation frequency adaptive vibration isolator that adjusts system parameters online according to different excitation frequencies. Background Technology

[0002] Mechanical vibration is a significant cause of system performance issues and even structural damage, and it is widespread in industries such as automotive, military, shipbuilding, aerospace, and ultra-precision machinery. Therefore, vibration isolation equipment is crucial for industrial systems, and extensive research has been conducted on vibration isolation in engineering structures over the past few decades. For traditional passive linear vibration isolators composed of linear springs and viscous dampers, a trade-off must be struck between load capacity and vibration isolation performance. For linear systems, vibration isolation occurs when the load exceeds a certain threshold. The frequency range is multiples of the system's natural frequency. Therefore, to improve vibration isolation performance by broadening the isolation range and improving transmission characteristics near the resonant region, one of the most direct ways is to reduce the natural frequency, i.e., reduce the equivalent / overall stiffness of the isolator. However, for passive systems, stiffness cannot be reduced indefinitely, as this may cause significant static deformation. Therefore, a new type of isolator, called a high static-low dynamic isolator, is obtained by introducing negative stiffness in parallel with positive stiffness. The high static-low dynamic isolator combines high static stiffness and low dynamic stiffness, which can reduce the system's natural frequency while ensuring good load capacity, thereby improving the system's vibration isolation performance.

[0003] Several methods can be used to achieve negative stiffness. A common approach is to connect a vertical spring with two horizontal / tilted springs, where the tilted springs provide negative stiffness once the isolating mass deviates from its equilibrium position. Other methods include utilizing the magnetic force between permanent magnets or employing four tilted buckling Euler beams to provide negative stiffness. However, while tilted springs and buckling beams can achieve high static and low dynamic vibration isolation, their layout results in relatively large structures. This can limit their application if available system installation space is limited. Furthermore, for traditional mechanical (e.g., tilted springs, buckling beams) and magnetic (e.g., permanent magnets) high static and low dynamic vibration isolation systems, once the structural dimensions are fixed, it is difficult to adjust the characteristics (e.g., frequency) for external excitations, which may weaken their adaptability to different vibration characteristics. Additionally, the introduction of negative stiffness significantly reduces the natural frequency of the high static and low dynamic vibration isolation system, but simultaneously leads to low-frequency vibration amplification. Therefore, it is necessary to design a system that can identify vibration characteristics (frequency) online in real time and intelligently adjust the negative stiffness of the system based on the identification results to achieve efficient isolation of mid-to-high frequency vibrations and effectively improve the low-frequency vibration amplification problem. Summary of the Invention

[0004] This invention provides an excitation frequency adaptive vibration isolator that effectively combines a high static, low dynamic system with a linear system. It utilizes an electromagnetic device to provide adjustable negative stiffness and identifies the excitation frequency online based on the system's displacement response signal. During operation, the excitation frequency is identified online in real time, and the current in the electromagnetic device is intelligently adjusted according to the identification result to achieve intelligent switching between the linear system and the high static, low dynamic system. Compared to traditional linear and high static, low dynamic systems, this invention extracts the best features and discards the worst, effectively solving the problem of limited isolation bandwidth in traditional linear vibration isolators and the low-frequency vibration amplification problem in existing high static, low dynamic vibration isolation systems. It achieves efficient isolation of mid-to-high frequency vibrations and effectively improves the low-frequency vibration amplification problem.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An excitation frequency adaptive vibration isolator includes an effective load, a fine-tuning nut, two steel helical springs, an upper base plate, a coarse-tuning retaining ring, a frame, a central shaft, a coil winding, a ring-shaped permanent magnet, a permanent magnet support, and a lower base plate.

[0007] The two steel helical springs are connected in parallel to form a positive stiffness mechanism, and the coil winding and the ring permanent magnet form a repulsive electromagnetic negative stiffness mechanism, which is connected in parallel with the two steel helical springs. Negative stiffness is introduced by energizing the coil.

[0008] The annular permanent magnet is fixed on the lower base plate by a permanent magnet support, and the coil winding is fixed on the central shaft by an aluminum winding cylinder;

[0009] Each of the upper and lower base plates is equipped with a linear bearing at its central axis to ensure the coaxiality of the frame and the central axis, thus ensuring the coaxiality of the coil winding and the toroidal permanent magnet. This also ensures the system is a single-degree-of-freedom system in the vertical direction. The linear bearings also reduce friction during movement, thereby reducing damping in the vibration isolation system. Two steel helical springs are fitted onto the central axis, located on either side of the upper base plate. One end of the spring is pressed against the linear bearing, and the other end is pressed against the coarse adjustment ring and the fine adjustment nut of the shaft system, respectively. This design, using two steel helical springs pressing in the middle, ensures that the load will not detach from the springs when the vibration isolation system experiences large displacement due to resonance. By adjusting the positions of the coarse adjustment ring and the fine adjustment nut on the shaft, the compression of the two steel helical springs can be adjusted, thereby adjusting the relative position of the toroidal permanent magnet and the coil winding. The coarse adjustment ring can be used for larger position adjustments, while the fine adjustment nut can be used for fine adjustments.

[0010] After the load is installed, the position of the coarse adjustment ring and the fine adjustment nut need to be adjusted to ensure that the vertical relative displacement x between the outer ring permanent magnet and the inner coil winding is 0 in the initial state (static balance state). This ensures that the vibration isolator has its maximum working stroke and is in an ideal working state. During operation, the excitation frequency acting on the system is identified in real time. When the excitation frequency is in the mid-to-high frequency range, power is supplied to the coil winding, and the system exhibits high static and low dynamic characteristics, achieving efficient vibration isolation. When the excitation frequency is in the low frequency range, the coil winding is de-energized, and the system returns to a linear system, greatly improving the low-frequency vibration amplification problem of the high static and low dynamic system.

[0011] Furthermore, the principle of the excitation frequency adaptive vibration isolator is as follows:

[0012] Based on the theory of single-degree-of-freedom mass-spring-damped systems in structural dynamics, the dynamic model of the above-mentioned vibration isolator mechanical device can be expressed by a single ordinary differential equation.

[0013]

[0014] In the formula, m is the mass of the vibration-isolated load, d is the differential symbol, t is time, x is the relative displacement of the vibration-isolated load, c is the damping of the vibration isolator, and k1 = 2k s -p1 is the equivalent linear stiffness coefficient of the vibration isolator, k s Let p1 be the stiffness of the helical spring, p3 be the first-order coefficient of the polynomial fitting of the electromagnetic force of the electromagnetic device, k3 = -p3 be the third-order nonlinear stiffness coefficient of the vibration isolator, and p3 be the third-order coefficient of the polynomial fitting of the electromagnetic force of the electromagnetic device. b The basic displacement excitation amplitude, ω b The excitation frequency to be measured;

[0015] Differentiate both sides of the above equation with respect to time t twice, and multiply by both sides of the above equation. The equations obtained are added together to get

[0016]

[0017] Multiply both sides of the above equation Then, integrate both sides of the obtained equation four times with respect to time t to get...

[0018]

[0019] The above equation yields the explicit expression for the online excitation frequency identifier.

[0020]

[0021] In the formula, Let ξ4 represent the frequency calculated by the frequency identifier, γ represent the filter gain, t0≥0 represent the frequency identification start time, and the expressions for ξ4 and η4 are given.

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] Among them, ξ1, ξ2, ξ3, η1, η2 and η3 are all intermediate parameters.

[0028] Furthermore, in the online vibration frequency identifier based on displacement response signals, the start time of frequency estimation can be adaptively readjusted according to changes in the external excitation frequency. t0 is an important parameter in the identifier, and its adjustment strategy is detailed in the appendix. Figure 3 This strategy can effectively address situations involving changes in the frequency of external excitation. Figure 3 As can be seen, the frequency identification process can be divided into two parts: a transient phase and a steady-state phase. Here, t1 is a user-defined transient phase duration, and the difference value d is the difference between the current frequency estimate and the previous frequency estimate divided by the step size. The identifier parameter D1 is a user-defined value. As the frequency estimate gradually converges, the difference value d gradually approaches 0. When d < D1, the identification transitions from the transient phase to the steady-state phase. Similarly, the identifier parameter D2 is also a user-defined value. When the excitation frequency changes, the frequency estimate will change, and the difference value d will undergo a significant abrupt change from 0 or a value close to 0 to greater than D2. At this point, t0 is reselected as the current time, and the identification transitions from the steady-state phase to the transient phase. The identifier parameters t1, D1, and D2 can be selected based on experience and the characteristics of the vibration isolation system. The above is the explicit expression of the vibration frequency identifier based on the displacement response signal.

[0029] Furthermore, the displacement of the system is measured in real time during operation to calculate the excitation frequency. Based on the results, the current in the electromagnetic device is intelligently adjusted to achieve the switching between linear system and high static low dynamic system. This enables efficient isolation of vibration in the mid-to-high frequency domain and effectively improves the problem of vibration amplification in the low frequency band, solving the problem of limited isolation frequency band of traditional linear vibration isolators and the problem of low frequency vibration amplification in existing high static low dynamic vibration isolation systems.

[0030] The advantages of this invention compared to existing technologies are as follows: the device is simple and its negative stiffness is flexibly adjustable; the frequency identification algorithm is accurate and effective, making it suitable for industrial fields such as automobiles, ships, aerospace, and high-precision machinery. The proposed excitation frequency adaptive vibration isolator and vibration isolation method comprises two parts: a single-degree-of-freedom vibration isolator mechanical device with adjustable negative stiffness based on an electromagnetic spring, and an online vibration frequency identifier based on displacement response signals (the identifier is deployed in the controller). In operation, the system's displacement response signal is measured and recorded in real time. The external excitation frequency acting on the system is calculated online through the frequency identifier. Based on the identified results, the current in the electromagnetic device is intelligently adjusted, thereby adjusting the system's equivalent stiffness. This enables flexible switching between linear systems and high static / low dynamic systems, effectively solving the problem of limited isolation bandwidth in traditional linear vibration isolators and the low-frequency vibration amplification problem in existing high static / low dynamic vibration isolation systems. It achieves efficient isolation of mid-to-high frequency domain vibrations and effectively improves the low-frequency vibration amplification problem. This invention has rich application prospects and practical significance. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the principle of the present invention;

[0032] Figure 2 This is a schematic diagram of the mechanical device of the present invention;

[0033] Figure 3 Here is a flowchart illustrating the principle of frequency identification.

[0034] Figure 4 This is a flowchart of the experimental apparatus in Specific Implementation Method 1;

[0035] Figure 5 Transit rate curves for linear systems, high static low dynamic systems, and adaptive systems;

[0036] Figure 6 The diagram shows the frequency identification results of the vibration isolator under foundation displacement excitation.

[0037] Figure 7 This is a comparison diagram of the displacement response of the vibration isolator under foundation displacement excitation. Detailed Implementation

[0038] The following will refer to the appendix. Figure 1 To be continued Figure 7 Specific embodiments of the invention will be described in more detail below. However, it should be noted that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey its scope to those skilled in the art.

[0039] Specific Implementation Method 1: The experimental setup for this embodiment is shown in the attached diagram. Figure 4As shown, the device includes a laser displacement sensor, a data acquisition and analysis instrument, a controller, a power amplifier, and the invented vibration isolator. The mechanical device of this excitation frequency adaptive vibration isolator is as follows: Figure 2 As shown, it includes: a payload (1), a fine-tuning nut (2), a steel helical spring (3), an upper base plate (4), a coarse-tuning retaining ring (5), a frame (6), a central shaft (7), a coil winding consisting of six coils (8), six ring-shaped permanent magnets (9), a permanent magnet support (10), and a lower base plate (11). Two steel helical springs are connected in parallel to form a positive stiffness mechanism, and the coil winding and the ring-shaped permanent magnets form a repulsive configuration electromagnetic negative stiffness mechanism. The vibration isolator is in a vibration environment. A laser displacement sensor is used to measure the displacement response of the payload. The collected displacement signal is transmitted to a data acquisition and analysis instrument for analysis, and the controller calculates to identify the frequency of the external excitation in real time and generates a voltage signal based on the identified frequency. The above demonstrates the principle and process of vibration isolation using the excitation frequency adaptive vibration isolator proposed in this invention through experimental methods.

[0040] This embodiment combines hardware and software to achieve adaptive vibration isolation functionality using the excitation frequency adaptive vibration isolator and method of the present invention.

[0041] Specific Implementation Method Two: Utilizing the frequency sensor proposed in this invention, the excitation frequency is identified based on the displacement signal through numerical simulation. In this embodiment, the frequency sensor has an effective mass of 3.5 kg, a spring stiffness of 10800 N / m, and a damping of 13 N / m. 2 The gain is 0.01.

[0042] The polynomial fitting coefficients for the electromagnetic force of the electromagnetic device are p1 = 9654.5083 and p2 = -148927873.3821. The excitation amplitude of the foundation displacement is X. b =0.5mm. The transfer rate curves of the linear system, the high static low dynamic system, and the excitation frequency adaptive system proposed in this invention are as follows: Figure 5 As shown, it can be clearly seen that the excitation frequency adaptive vibration isolation system eliminates the resonance peaks of linear systems and high static low dynamic systems, greatly improving vibration isolation performance. Under the external excitation of simple harmonic displacement of the base, the external excitation frequency, the result calculated by the frequency identifier, and the system current value are as follows: Figure 6 As shown, the frequency identification effect is good. The displacement responses of the linear isolator, the high static low dynamic isolator, and the excitation frequency adaptive isolator of this invention under external excitation are as follows: Figure 7 As shown, under the same excitation, the invented excitation frequency adaptive vibration isolator has the smallest vibration amplitude.

[0043] Simulation results demonstrate that, for complex variable-frequency harmonic excitation, the excitation frequency adaptive vibration isolator and method of this invention can achieve effective and excellent vibration isolation.

[0044] The above two implementation methods provide a more thorough understanding of the present invention and its implementation, and more intuitively demonstrate the excellent vibration isolation performance and great engineering application potential of the present invention.

Claims

1. An excitation frequency adaptive vibration isolator, characterized in that: The vibration isolator includes an effective load (1), a fine-tuning nut (2), two steel helical springs (3), an upper base plate (4), a coarse-tuning retaining ring (5), a frame (6), a central shaft (7), a coil winding (8), an annular permanent magnet (9), a permanent magnet support (10), and a lower base plate (11). The two steel helical springs (3) are connected in parallel to form a positive stiffness mechanism, and the coil winding (8) and the ring permanent magnet (9) form a repulsive configuration electromagnetic negative stiffness mechanism, which is connected in parallel with the two steel helical springs (3) and introduces negative stiffness by energizing the coil. The annular permanent magnet (9) is fixed on the lower base plate (11) by a permanent magnet support (10), and the coil winding (8) is fixed on the central shaft (7) by an aluminum winding cylinder; The upper substrate (4) and the lower substrate (11) each have a linear bearing installed at the central shaft (7) to ensure the coaxiality of the frame (6) and the central shaft (7); the two steel helical springs (3) are sleeved on the central shaft (7) and located on both sides of the upper substrate (4). One end of the spring is pressed against the linear bearing, and the other end is pressed against the coarse adjustment retaining ring (5) and the fine adjustment nut (2) of the shaft system, respectively. The principle of the excitation frequency adaptive vibration isolator is as follows: Based on the theory of single-degree-of-freedom mass-spring-damped systems in structural dynamics, the dynamic model of the above-mentioned vibration isolator can be expressed by a single ordinary differential equation. In the formula, The mass of the vibration-isolated load. It is the differential symbol. It is time. The relative displacement of the vibration isolation load. For the damping of the vibration isolator, This is the equivalent linear stiffness coefficient of the vibration isolator. Let be the stiffness of the helical spring. These are the first-order coefficients of the polynomial fitting of the electromagnetic force of the electromagnetic device. It is the third nonlinear stiffness coefficient of the vibration isolator. These are the cubic coefficients of the polynomial fitting of the electromagnetic force of the electromagnetic device. Based on the basic displacement excitation amplitude, The excitation frequency to be measured; Relating both sides of the above equation to time Differentiate twice and multiply by both sides of the above expression. The equations obtained are added together to get Multiply both sides of the above equation Then, divide both sides of the obtained equation with respect to time. After four integrations, we obtain The above equation yields the explicit expression for the online excitation frequency identifier. In the formula, This represents the frequency calculated by the frequency identifier. Indicates the filter gain; Indicates the start time of frequency identification. and The expression is, in, All of these are intermediate parameters.

2. The excitation frequency adaptive vibration isolator according to claim 1, characterized in that: In the vibration frequency online identifier based on displacement response signal, the start time of frequency estimation can be adaptively readjusted according to the change of external excitation frequency. This principle can be used to effectively deal with the situation of external excitation frequency change. The frequency identification process is divided into two parts: the transient phase and the steady-state phase. The frequency difference is defined as the difference between the frequency estimate of the current step and the frequency estimate of the previous step, divided by the step size. The initial process of frequency identification is the transient process. In this phase, when the frequency difference converges, the frequency estimate also approaches the true value, and the identification process enters the steady-state phase. In this phase, if the frequency difference changes abruptly, it indicates that the excitation frequency has changed. At this time, the frequency estimation start time is updated to the current moment. The above is the adjustment strategy for the frequency estimation start time in response to changes in external excitation frequency.

3. The excitation frequency adaptive vibration isolator according to claim 1, characterized in that: During operation, the displacement of the system is measured in real time to calculate the excitation frequency, and then the current in the electromagnetic device is intelligently adjusted according to the results to achieve the switching between a linear system and a high static and low dynamic system.

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