Two-stage Vibration Isolation Research Articles

Optimization design of a two-stage multidirectional vibration isolation system for large airborne equipment

Purpose Improvement and optimization design of a two-stage vibration isolation system proposed in this paper are conducted to ensure the device of electronic work effective.Design/methodology/approach The proposed two-stage vibration isolation system of airborne equipment is optimized and parameterized based on multi-objective genetic algorithm.Findings The results show that compared with initial two-stage vibration isolation system, the angular vibration of the two-stage vibration isolation system becomes 3.55 × 10-4 rad, which decreases by 89%. The linear isolation effect is improved by at least 67.7%.Originality/value The optimized two-stage vibration isolation system effectively improves the vibration reduction effect, the resonance peak is obviously improved and the reliability of the mounting bracket and the shock absorber is highly improved, which provides an analysis method for two-stage airborne equipment isolation design under complex dynamic environment.

Vibration response analysis of a two-stage vibration isolation system for large airborne equipment

PurposeThis paper aims to propose a two-stage vibration isolation system for large airborne equipment to isolate aircraft vibration load.Design/methodology/approachFirst, the vibration isolation law of the discrete model of large airborne equipment under different damping ratios, stiffness ratios and mass ratios is analyzed, which guides the establishment of a three-dimensional solid model of large airborne equipment. Subsequently, the vibration isolation transfer efficiency is analyzed based on the three-dimensional model of the airborne equipment, and the angular and linear vibration responses of the two-stage vibration isolation system under different frequencies are studied.FindingsFinally, studies have shown that the steady-state angular vibration at the non-resonant frequency changes little. In contrast, the maximum angular vibration at the resonance peak reaches 0.0033 rad, at least 20 times the response at the non-resonant frequency. The linear vibration at the resonant frequency is at least 2.14 times the response at the non-resonant frequency. Obviously, the amplification factor of linear vibration is less than that of angular vibration, and angular vibration has the most significant effect on the internal vibration of airborne equipment.Originality/valueThe two-stage vibration isolation equipment designed in this paper has a positive guiding significance for the vibration isolation design of large airborne equipment.

Performance Enhancement by Exploiting Geometrical Nonlinearity of Inerters in a Two-Stage Vibration Isolator

This research proposes a two-stage vibration isolation system (TS-VIS) exploiting geometrical nonlinearity by inerters for performance enhancement. Lateral inerters are added to upper and lower stages creating geometric nonlinearity. The transmissibility and power flow indices are used for the performance evaluation. It is demonstrated that the inerters in both stages of the TS-VIS can enhance substantially the effectiveness of isolation at low frequencies by bending and shifting the resonance peaks in the force and energy transmission curves to the left while reducing the peak heights in these curves. It shows the use of inerters introduces a local minimum in the transmissibility curve which can be exploited for significant reduction in vibration transmission at a desirable frequency. By tailoring the inertance ratios for both stages of the TS-VIS, further improvements on the performance can be achieved by extending the frequency range of effective isolation. This work shows the benefits of using nonlinear inerters in the TS-VIS to obtain superior low-frequency isolation performance, which is potentially applicable in engineering systems such as floating raft structures.

Ultra-stable cryogenic sapphire cavity laser with an instability reaching 2 × 10-16 based on a low vibration level cryostat.

Cryogenic ultra-stable lasers have extremely low thermal noise limits and frequency drifts, but they are more seriously affected by vibration noise from cryostats. Main material candidates for cryogenic ultra-stable cavities include silicon and sapphire. Although sapphire has many excellent properties at low temperature, the development of sapphire-based cavities is less advanced than that of silicon-based. Using a homemade cryogenic sapphire cavity, we develop an ultra-stable laser source with a frequency instability of 2(1) × 10-16. This is the best frequency instability level among similar systems using cryogenic sapphire cavities reported so far. Low vibration performance of the cryostat is demonstrated with a two-stage vibration isolation, and the vibration suppression is optimized by tuning the mixing ratio of the gas-liquid-helium. With this technique, the linear power spectral densities of vibrations at certain frequencies higher than tens of hertz are suppressed by two orders of magnitude in all directions.

Dynamic Analysis of an Autonomous Underwater Glider with Single- and Two-Stage Vibration Isolators

Vibrations from the power system can significantly affect the working performances (ocean observation) of autonomous underwater gliders (AUGs). In order to reduce the vibration transmission from vibration sources to the precision instruments in AUGs, single- and two-stage vibration isolator rings are designed in this paper. The dynamic models of the single- and two-stage vibration isolation of the AUG are presented. The force transmission ratio of the AUG is calculated in MATLAB code. The influences of the isolator and the structure stiffness are analyzed. The dynamic stiffness of the designed isolators, as an important design parameter, is calculated using the finite element method. The influence of the designed parameter on the dynamic stiffness of the rubber ring isolator is discussed. The coupled vibro-acoustic finite element method is used to analyze the vibration and acoustic response of an AUG with the single- and two-stage vibration isolators. The insertion loss is calculated in order to assess the vibration isolation performance of the single- and two-stage vibration isolators. The results from the dynamic models and the finite element models both show that the vibration isolation performance of the two-stage vibration isolator ring performs better than that of the single-stage vibration isolator ring.

Design, analysis, control simulation, and experiment of novel electromagnetic hybrid vibration absorber

This paper presents a novel type of electromagnetic hybrid vibration absorber (EHVA) with a double-ring series permanent magnetic circuit applied to improve the two-stage vibration isolation system of marine power machinery. The EHVA comprises a mover with several groups of coils having a series connection, as well as a stator with internal permanent magnets and external permanent magnets, which form a novel magnetic circuit structure based on an improved Halbach array. In this magnet circuit, two adjacent groups of magnetic induction lines overlap at the coil position, thereby strengthening the magnetic field intensity. When the mover moves axially, the coil cuts the magnetic induction line to produce Lorentz force and magnetic damping force. First, the dynamic parameters of the EHVA were calculated based on multi-rigid-body dynamic theory and fixed-point theory. Second, the mechanical and electromagnetic structures of the EHVA were designed. Finally, a test stand was constructed, the system control channel was identified, and the simulation as well as experiment for vibration control using an [Formula: see text] controller were performed. Results indicated that the hybrid vibration reduction system under control reduced the acceleration amplitude by 12.3 dB at 30.6 Hz and achieved better vibration absorption effects between 27 and 33 Hz compared with the uncontrolled system.

Optimal Control of Semiactive Two-Stage Vibration Isolation Systems for Marine Engines

To improve the vibration reduction performance of two-stage vibration isolation systems for marine engines under wide frequency band and multifrequency excitation, the magnetorheological (MR) damper is introduced into the vibration isolation system and an optimal controller is designed. Taking the test results of MR damper dynamic characteristics as sample data, the forward and inverse models of the MR damper are identified by the least square method and neural network (NN) method respectively, and the identification results are applied to semiactive control of the two-stage isolation system. Based on the analysis of vibration source, a six-degree-of-freedom mechanical model of two-stage system based on the MR damper is established. The optimal controller taking the minimum force transmitted from the engine to base as the control objective is designed. The system model and numerical simulation analysis are established using MATLAB. The results show that the isolation effect of optimal control is better than that of passive vibration isolation in the whole frequency band. In addition, good control effect is achieved in the low-frequency resonance region which is most concerned in engineering, which is of great significance to further improve the vibration reduction performance of marine engines.

An enhanced adaptive notch filtering method for online multi-frequency estimation from contaminated signals of a mechanical control system

Real-time frequency information is extremely important in many fields of mechanical engineering, such as fault diagnosis, noise and vibration control, underwater acoustic detection, vehicle communication, etc. However, sometimes frequencies cannot be directly detected, making it important to quickly and accurately estimate the frequencies from contaminated signals of a mechanical system. An adaptive notch filter (ANF) is one of the most popular methods for online frequency estimation due to its simple structure and low computational complexity. However, ANF is a biased estimation if the signal contains uncorrelated noise. An enhanced adaptive notch filtering (EANF) method, which is able to reduce the frequency estimation bias and improve the estimation speed from contaminated signals, is proposed in this paper. Firstly, the limitations of the traditional ANF method are theoretically and numerically analyzed. Then, the principles of the proposed EANF method are formulated, including key parameter optimization and uncorrelated noise compensation in the update process. Afterwards, a multiple extension of the proposed EANF method is constructed using the adaptive simultaneous structure. The results of the numerical simulation show that the proposed method is superior to traditional ones. Finally, a two-stage vibration isolation system is established for experimental validation. The experimental results also demonstrate the effectiveness of the proposed method.

Research of Vibration Characteristics of Ship Propeller-shaft Longitudinal Two-stage Vibration Isolation System

Aiming at the vibration control problem of ship propeller-shaft system, this paper put forward a design approach of ship propeller-shaft longitudinal two-stage vibration isolation system and its dynamic characteristics are studied. The vibration mathematical model of ship propeller-shaft longitudinal two-stage vibration isolation system is established. The influence of mass ratio, stiffness ratio and damping ratio of two-stage vibration isolation system is studied. The design is optimized taking a ship propeller-shaft system as an example. The results show that the ship propeller-shaft longitudinal two-stage vibration isolation system which is optimized has better isolation effect than the single-stage vibration isolation system. The research results have important reference value for ship propeller-shaft longitudinal vibration isolation design.

The Elliptic Harmonic Balance Method for the Performance Analysis of a Two-Stage Vibration Isolation System with Geometric Nonlinearity

This study develops a modified elliptic harmonic balance method (EHBM) and uses it to solve the force and displacement transmissibility of a two-stage geometrically nonlinear vibration isolation system. Geometric damping and stiffness nonlinearities are incorporated in both the upper and lower stages of the isolator. After using the relative displacement of the nonlinear isolator, we can numerically obtain the steady-state response using the first-order harmonic balance method (HBM1). The steady-state harmonic components of the stiffness and damping force are modified using the Jacobi elliptic functions. The developed EHBM can reduce the truncation error in the HBM1. Compared with the HBM1, the EHBM can improve the accuracy of the resonance regimes of the amplitude-frequency curve and transmissibility. The EHBM is simple and straightforward. It can maintain the same form as the balancing equations of the HBM1 but performs better than it.

A Fourier series method for solving the two-stage vibration isolation system under dual-wave shock input

Shock isolation for on-board devices is one of the most important issues for underwater vehicles to resist underwater non-contact explosions (UNDEX). According to German military specification BV043/85, the shock input spectrum can be transformed into a time domain signal represented as a dual-wave, which is composed of a positive and a negative half-sine. Previous researches have pointed out that two-stage vibration isolation system (TSVIS) shows better isolation performance than the single-stage vibration isolation system (SSVIS). However, there is relatively rare research on the shock isolation performance of a TSVIS subjected to a dual-wave shock input. This issue is addressed in this investigation. The Fourier series method is employed to calculate the response in the time domain. This study will shed some light on the design of TSVIS in a dual-wave environment.

Shock response of a two-stage vibration isolation system

Abstract. Two-degree of freedom system, or two-stage mount are used to improve the high frequency vibration isolation performance with the disadvantage of increasing the mass of the system and adding a second resonance. The vibration isolation property is a well-understood topic for harmonic vibration considering linear and nonlinear elements, but not its shock response. The absolute and relative response of a two-stage mount under shock excitation is investigated in this paper. Analysing the effect of the mass ratio between the two-stage, and its respective viscous damping. The potential advantages and issues behind this system are discussed and compared with the single mount. Experimental validation was performed using two commercial isolator and different masses. Findings suggested that a large secondary mass could reduce the shock response in terms of absolute motion. This effect is only significant for the case of short pulses and when the added mass is at least five times greater than the main mass. Being useful to have light damping only on the secondary stage.

Intelligent vibration detection and control system of agricultural machinery engine

Vibration of agricultural machinery not only affects the quality and effect of the operation, but also reduces the service life of machinery. A vibration detection and control system based on intelligent sensor nodes was developed to detect and control the frame vibration caused by high-power engine in agricultural machinery. Each intelligent detection node can work independently or networking as Internet of Things system. The effect of the vibration isolation system can be assessed by installing the test nodes at the measuring points of the two-stage vibration isolation system. In this paper, intelligent sensor nodes were used to reduce the vibration of an agricultural machinery engine. According to the optimized stiffness of the double-layer vibration isolation system, a test platform system is designed. The intelligent sensor nodes were used to assess the vibration spectrum characteristics of engine under various working conditions, and acceleration values of upper and lower measuring points of stage 1 and stage 2 isolators. The relationship between acceleration transfer rate and engine speed was analyzed before and after double-layer vibration isolation was used, and the vibration isolation effect of double-layer vibration isolation system is verified. The results show that the double-layer vibration isolation system can play a significant role in changing the stiffness of the whole system and avoiding the occurrence of coupling resonance. The transmission rate of vibration acceleration decreases from 0.94 to 0.54 at the engine speed of 2700 r/min, with a decrease of 42.3%. The results show that the proposed intelligent detection node is able to detect the engine vibration in agricultural machinery, and the proposed double-layer vibration isolation system can effectively reduce the engine vibration.

Design and research on impact resistance characteristics of vector hydrophone application platform

On the basis of the analysis of the impact resistance of the application platform of the vector hydrophone is analysed , this paper designed single-stage and two-stage vibration isolation system based on rubber damper by using its characteristics of large viscous damping coefficient, low mass and easy installation and disassembly. By comparing the output signal of vector hydrophones in the state of rigid connection and with single-stage vibration isolation system, it can be seen that under different connection conditions, the signal amplitude of the impact response of the hydrophone are also different. The results of the experiment verified the effect of vibration isolation system on impact signal and the accuracy of theoretical analysis results.

Investigation on a two-stage platform of large stroke for broadband vertical vibration isolation

For the purpose of preventing vibration-sensitive optical switches from malfunction caused by broadband vertical vibration, a novel two-stage vibration isolation platform is proposed. The primary stage is a bellows-type isolator of large stroke and low isolation frequency, and the secondary stage is a small-stroke hybrid isolator composed of bellows and voice-coil actuators. In the primary stage, two pre-compressed horizontal bellows and one vertical bellows are used to counter the weight of the switch and to reduce the total height of the isolator. The static properties of the primary stage are analyzed, and the vibration isolation of the platform is investigated. Numerical results indicate that the two-stage platform is effective in isolating vertical vibration. Experiments are also conducted to verify the performance of the platform. It is exhibited that the transmissibility is less than 0 dB over 2 Hz, and the attenuation rate reaches −35 dB/dec at high frequencies. The frequency range of test is 2–200 Hz, and the maximum displacement is 10 mm at 2 Hz. In the secondary stage, the actuators can substantially suppress the resonance peak, and promote isolation performance at low frequencies.

Use of mechanical models for the analysis of antivibration mounting

The paper considers a two-stage vibration isolation of rotary machines including rotor-frame elastic linkage. It proposes internal elastically inertial vibration protection inbuilt between a rotor and a frame. The method of dynamic compliance is used to define forces influencing the frame. The proposed vibration motor can be used for rotary actuators of compact devices. The main objective of the study is to increase the motor torque and durability.

Versatile variable temperature and magnetic field scanning probe microscope for advanced material research.

We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.

Numerical investigation of a two-stage serial vibration isolation system using frequency response function based substructuring method

The mechanical system applied in industry and manufacturing fields is generally a complex multi-stage isolation system, which contains a lot of connection parts. In order to better analyze the effect of the connection parts, the transfer path model of a two-stage serial system is developed in this article using frequency response function based substructuring method. To verify the proposed transfer path model, a finite element model that simulates a two-stage serial vibration isolation system is built. By comparing the predicted results and exact values, the model proves to be correct. Furthermore, the random noise is introduced into the system-level frequency response functions for error sensitivity analysis and the influence on the substructure frequency response functions is quantified through comparison. Since the possible errors are unknown in the experimental measurement, 5%, 25%, and 50% random errors are introduced into all the input frequency response functions individually to analyze the influence of different noise levels on the prediction accuracy. In order to solve the ill-conditioned inverse problem involved in the model, the truncated singular value decomposition is also applied. The simulation results show that compared with the direct-inverse method, truncated singular value decomposition can decrease the prediction error caused by the introduced noise more effectively.

Two stage vibration isolation of vibratory shake-out conveyor

In this paper the effectiveness of two stage vibration isolation on example of a vibratory conveyor has been shown. Vibratory conveyors are used for separating the casting from the mold in foundries. In the considered case the shake-out conveyor has been supported directly on the foundation. Due to that the high amplitudes of vibrations on the foundation has been observed, which are transmitted to the building structure. To reduce the vibration transmission from the conveyor to the foundation, two-stage vibration isolation has been applied. The mathematical model of two stage vibration isolation has been shown. Based on the results of calculations, simulations and measurements a significant reduction of vibrations at the building structure has been achieved.

Experimental Investigation of a Two-Stage Nonlinear Vibration Isolation System With High-Static-Low-Dynamic Stiffness

A novel design of a two-stage nonlinear vibration isolation system, with each stage having a high-static-low-dynamic stiffness (HSLDS), is studied experimentally in this paper. The positive stiffness in each stage is realized by a metallic plate, and the corresponding negative stiffness is realized by a bistable carbon fiber–metal (CF) composite plate. An analytical model is developed as an aid to design a bistable composite plate with the required negative stiffness, and a static test of the plate is conducted to measure the actual stiffness of the plate. Dynamic tests of the two-stage isolator are carried out to determine the effectiveness of the isolator. Two tests are conducted, one with the bistable composite plates removed so that the isolator behaves as a linear device and one with the bistable composite plates fitted. An improvement in the isolator transmissibility of about 13 dB at frequencies greater than about 100 Hz is achieved when the bistable composite plates are added.