Vibration Isolation Requirements Research Articles

Structure Design and Optimization of MRE Vibration Isolator

As an intelligent component, the high-performance MRE vibration isolator has great advantages, such as a wide vibration isolation frequency range and good performance in semi-active vibration reduction applications. In order to develop high-performance MRE devices, Firstly, this paper makes use of the advantages of real-time tracking/away from external excitation frequency of MRE devices, analyzes the working mode of MRE, and designs a shear MRE vibration isolator based on airborne equipment. Secondly, the material selection and magnetic circuit analysis of the MRE are also completed, and the magnetic field in the MRE region is maximized under the same input energy, thus improving the working efficiency of the MRE isolator. Finally, the relationship between magnetic induction intensity and structural size variables is established by the finite element method and the structural dimensionless method. Based on COMSOL multi-physics simulation software (version 6.0), the global optimization is carried out, the results show that the optimal solution satisfying the comprehensive index of optimal vibration isolation performance of the MRE isolator is obtained, then the structural parameters of the isolator are optimized, and its magnetic control performance is improved. The MRE vibration isolator designed in this paper meets the vibration isolation requirements of airborne optical equipment and has certain engineering application value.

Customized quasi-zero-stiffness metamaterials for ultra-low frequency broadband vibration isolation

Quasi-zero-stiffness (QZS) metamaterials play an important role in ultra-low frequency vibration mitigation. In this study, a customized QZS metamaterial is proposed to isolate ultra-low frequency broadband vibration and its isolation performance is verified. A representative unit cell (RUC) that satisfies both optimal QZS performance and minimum size is designed for the metamaterial and optimized by matching the parameters of positive stiffness heart-shaped beam with the properties of negative stiffness cosine beam. Then, a new composite structure with multiple RUCs is designed by matching the optimal mass block for each RUC to meet the vibration isolation requirements of ultra-low frequency and broadband. The transmissibility test is performed, and the isolator made of the metamaterial is then integrated into an underwater glider to test the vibration isolation performance. The results show that the proposed QZS metamaterial can isolate broadband vibrations of 3.2 to 60 Hz and the isolator can attenuate the vibration signals of gliders to the background noise in air and water. Therefore, the customized metamaterial can be used in the engineering case of ultra-low frequency broadband vibration isolation and the design method of the metamaterial can be used for reference by other equipment.

Active vibration hybrid control strategy based on multi-DOFs piezoelectric platform

With the increasing requirements for vibration isolation in multiple degrees of freedom (multi-DOFs), active control strategy is becoming more meaningful. However, the vibration isolation performance is limited by the time delay of feedback control, and cannot meet higher requirements. Therefore, this paper proposes a multi-DOFs active vibration hybrid control (AVHC) strategy based on a piezoelectric platform. The AVHC integrates the adaptive feedforward control based on the modified recursive least squares (MRLS) algorithm, and the feedback control based on the integral force feedback (IFF) algorithm. To achieve advanced response, the ground-based vibration signal is offset by the MRLS algorithm. To further reduce the coupling of multi-DOFs, the feedback and feedforward coordinates are fused through the matrix transformation, and the signals are linearly superimposed by the AVHC. The experimental results show that the AVHC can further reduce the resonance peaks of the three translational directions ( X/ Y/ Z) compared with the feedback (FB) control. The resonance peaks are reduced from 14.6 dB (FB) to 3.11 dB (AVHC), from 14.56 dB (FB) to 5.14 dB (AVHC), and from 12.44 dB (FB) to 3.78 dB (AVHC) in X/ Y/ Z directions, respectively. The attenuation rates are improved by 73.36%, 66.19%, and 63.10% in X/ Y/ Z directions, respectively.

Modeling of a Ti/NiTi spring-blade gear for space micro–vibration isolation

Space pointing mechanisms are crucial in space scientific experiments and observations. Since the precision of such mechanisms is highly susceptible to micro–vibrations due to environmental disturbances and inherent defects, isolating micro–vibrations is important. A low rotational stiffness spring-blade gear installed on the output shaft of the stepper motor can isolate micro–vibrations due to the motor’s discontinuous rotation. However, a quantitative performance description is still lacking. In this paper, a rotational stiffness model for the spring-blade gear made of titanium and nickel–titanium-based shape memory alloy is established and experimentally validated. A vibration transmissibility model is developed, revealing the relationships among the layout, material properties, structural parameters, external loads, rotational stiffness, and vibration transmissibility of the spring-blade gear. This paper can be used to design and optimize the spring-blade gear, predicting the isolation and suppression capability against micro–vibrations at different frequency ranges. The optimal gear structure can be obtained according to vibration isolation requirements, load, and installation constraints to achieve the predetermined vibration isolation effect. This study can ensure the space pointing mechanisms operate with high precision and stability by attenuating space micro–vibrations effectively, improving the quality of signal acquisition and observation accuracy.

Vibration isolation characteristics of magnetorheological damper for the large wind turbine gearbox

ABSTRACT The gearbox vibration isolation theory in the large wind turbine transmission system is analyzed. The host frame is flexible, and the vibration isolation system is approximately equivalent to a two-degree-of-freedom system. According to large wind turbine gearbox isolation requirement, and a vibration isolation device of magnetorheological damper of the large wind turbine gearbox is designed, the magnetic field characteristics inside the magnetorheological damper are simulated and calculated by using COMSOL, when 0.5, 1, 1.5and 2 A currents are passed through the magnetorheological damper coil, the magnetic induction intensity of the damping gap and the output force of the magnetorheological damper are calculated, it can reach 1300N-5400N, which meets the gearbox vibration isolation requirements. It designed the on-off current control method of the magnetorheological damper. The prototype is tested on a certain type of offshore wind turbine, and the acceleration spectrum signals of the gearbox in the Z direction are collected under the working conditions of 990, 1200 and 2000 r/min. According to the collected data values, the vibration isolation characteristics of the designed magnetorheological damper are analyzed; the data show that the vibration level drop is about 20 dB, and the vibration isolation effect is good. By using the coherence coefficient method to process the measured data, the modified transfer function is obtained, which is consistent with the theoretical transfer function of the vibration model of two-degree-of-freedom system, so it is proved to be reasonable. The vibration isolation characteristics of rubber and the magnetorheological damper are compared at the rated speed, and it shows that the maximum vibration acceleration of the gearbox under the magnetorheological damper reduces from 0.375 m/s2 to 0.175 m/s2, which verify the damping effect of the magnetorheological damper.

Improving the cooldown times for next-generation cryocooled gravitational-wave interferometers

We propose and test an exchange gas technique for improving the cooldown times of cryocooled gravitational-wave interferometers. The technique works by utilizing low-pressure dry nitrogen gas to create a path for heat conduction to test masses while protecting the rest of the in-vacuum equipment from unwanted heat leakage. We show that the technique is capable of shortening the total wait time to reach the operating temperature by a factor of 3.5. Additionally, our tests show that the improvement in the heat transfer rate can be predicted to be within 10% error by using the Sherman-Lees interpolation equation. The technique is compatible with vibration isolation requirements of the cryogenic shielding of 124 K silicon interferometers and has the potential to improve the iteration time for research and development. The scalability of the prototype, the ability to predict the heat conduction, and the simplicity of the engineering make the strategy a good candidate to be included in the cryogenic design of future cryocooled gravitational-wave interferometers. The findings mark a first step in the investigation for a strategy to mitigate ice formation on the interferometer optics during initial cooldown.

Noise requirements of the cryogenic shielding for next generation cryocooled gravitational wave observatories: Newtonian noise

We explore the vibration isolation requirements imposed by Newtonian noise on the cryogenic shielding for next-generation gravitational-wave observatories relying on radiative cooling. Two sources of Newtonian noise from the shield arrays are analyzed: the tidal coupling from the motion of a shield segment to its nearby test mass's displacement, and the effect of density fluctuations due to heterogeneous boiling of cryogenic liquids in the vicinity of the test masses. It was determined that the outer shields require no additional vibration isolation from ground motion to mitigate the Newtonian noise coupling to levels compatible with the LIGO Voyager design. Additionally, it was determined that the use of boiling nitrogen as the heat sink for the cryogenic arrays is unlikely to create enough Newtonian noise to compromise the detector performance for either Voyager or Cosmic Explorer phase 2. However, the inherent periodicity of the nucleation cycle might acoustically excite structural modes of the cryogenic array which could contaminate the signals from the interferometer through other means. This last effect could be circumvented by using a single-phase coolant to absorb the heat from the cryogenic shields.

Review on Vibration Isolation Method for Atomic Interference Gravimeter

The cold atomic interference absolute gravimeter is an ultra-precision instrument for measuring absolute gravity acceleration. At present, the highest measurement accuracy can reach the order of micro gamma. It has important application value and research significance in many disciplines, such as geophysics, resource exploration and assisted navigation. Because of its ultra-high precision, the ultra-low frequency micro-vibration noise on the ground has become one of the important factors affecting its accuracy, and it is also the bottleneck of the further development of gravimeter. Firstly, based on the theoretical and experimental results, this paper analyzes the vibration isolation requirements of atomic interference gravimeter. Secondly, it summarizes the research progress of atomic interference gravimeter isolation system and introduces three main isolation methods: passive vibration isolation, active vibration isolation and vibration compensation. Finally, the future development direction of atomic interference gravimeter isolation technology is analyzed and prospected.

Research on nonlinear vibration isolation device for electro-optic payload

In order to meet the requirements of electro-optic payload on vibration isolation performance, a high static stiffness and low dynamic stiffness nonlinear vibration isolator with rhombus linkage mechanism as negative stiffness component (rhombus HSLDS vibration isolator) was proposed. The mathematical model of vibration isolator was established by statics analysis method, and stiffness parameter setting and nonlinear adjustment methods were studied; the harmonic balance method (HBM) was used to solve the kinetic equation, and influence of parameters on the vibration isolation performance was analyzed; the theoretical model and conclusions were verified by kinetic simulation software ADAMS and prototype. The test results show that the rhombus HSLDS vibration isolator has convenient parameter adjustment capability, and the zero-position stiffness and stiffness nonlinearity can be set and optimized by parameters of tension spring and linkage. And the optimization effect of vibration isolation caused by stiffness nonlinearity is affected by the damping of main vibration isolator and zero-position stiffness parameter. Compared with traditional linear vibration isolator, the rhombus HSLDS vibration isolator has significant advantage of nonlinear vibration isolation and can better meet the needs of electro-optic payload vibration isolation requirements.

Fatigue failure analysis and finite element assessment of the twins torsion spring

To meet the vibration isolation requirements, the twins torsion spring is placed between the pivot and the clutch, which can make the generator and front gear train run more stably, and improve the durability of the system. In this study, the twins torsion spring was winded by SUS 631 stainless steel, and was treated by medium-temperature tempering. The fatigue life of the twins torsion spring was investigated. The morphology of fatigue fracture of the twins torsion spring was examined by scanning electron microscopy (SEM). And the vickers micro-hardness of the spring was tested by micro-hardness tester. Large amount of shrinkage porosity can be found in the fatigue extension area and instantaneous fault zone. And the average micro-hardness was about 565.5 HV on the area near the fracture. In order to analyze the causes of the fracture, the fatigue life was simulated by finite element (FE) numerical analysis. The simulation results are consistent with the experimental test of fatigue.

Vibration Isolation and Alignment of Multiple Platforms on a Non-Rigid Supporting Structure

In many applications comprised of multiple platforms with stringent vibration isolation requirements, several vibration isolators are employed to work in tandem. They usually must accomplish two objectives: (i) reduce the vibration level of each platform; and (ii) maintain the required alignment with respect to each other or with a fixed reference. If the isolators are located on a rigid supporting structure, the problem can be approached as a classical vibration isolation (VI) problem, in which an increase in damping implies a reduction of vibration level experienced by the platforms. However, there are an increasing number of scenarios in which the dynamic interaction between the isolator and the base structure has the potential to alter the system response and consequently degrade VI performance. In this work, a generalized method to analyze the combined VI and alignment problem, for multiple isolators located on a flexible supporting structure, is proposed. The dynamic interaction between the platforms and the isolators is considered in the control design, and it is proved employing two different functional values that the maximum damping solution is not always the best approach when the dynamics of the supporting structure are considered. Numerical simulations are presented to validate the theory developed and robustness of the proposed control approach is demonstrated.

An active hybrid control approach with the Fx-RLS adaptive algorithm for active-passive isolation structures

With improvements in the performance of optical equipment on spacecraft, the requirements for vibration isolation have become increasingly stringent. An efficient and reliable active hybrid control (AHC) approach used for an active-passive isolation single strut (APISS) is proposed in this paper. The APISS adopts an active-passive architecture in series as one single leg of the Stewart platform. To improve performance, the AHC approach includes a modified proportional integration force (PIF) feedback control algorithm and an improved filtered-x recursive least squares (Fx-RLS) adaptive feedforward control algorithm. The PIF is applied to establish a sky-hook damping and variable mass matrix system, and Fx-RLS is employed to compensate the vibration error caused by the base platform to the payload platform. Then, a single-DOF vibration isolation system consisting of a real-time active control system and a spectrum testing and analysis system is adopted to verify the proposed approach. The experimental results indicate that the AHC approach can effectively reduce the natural frequency by 5.02 Hz. Additionally, the resonance amplitude of the natural frequency decreases by 41.84 dB, the vibration attenuation rate reaches 99.2%, and the amplitude of the mid-frequency band is further attenuated. The experimental results highlight the effectiveness of the proposed method.

An Adjustable Low-Frequency Vibration Isolation Stewart Platform Based On Electromagnetic Negative Stiffness

With the continuously increasing requirements for vibration isolation in multiple degrees-of-freedom(DOFs), the negative stiffness(NS) passive Stewart platform with simple, reliable structure and good vibration isolation capability have become a concern. However, it has the disadvantage of unadjustable stiffness, which limits its application prospects. An adjustable electromagnetic negative stiffness (AENS) Stewart platform is proposed in this paper. It can realize good stiffness match conveniently and has high vibration isolation performance in all 6 DOFs. Firstly, this paper introduces the structural composition of the system. Then, the kinematics model is constructed by the vector method, the dynamic model is constructed by the second Lagrange equation, and the multi-DOFs transmissibility rate matrix is given. Finally, the performance of AENS Stewart platform are verified through experiments. The experimental results show that it can reduce the natural frequency from 3.94 Hz to 2.69 Hz, 7.69 Hz to 5.17 Hz, 9.5 Hz to 6.35 Hz, and 9.5 Hz to 6.35 Hz in the X(Y), Z, α(β), and γ DOFs, respectively. Convenient stiffness matching and good low-frequency vibration isolation in multi-DOFs make AENS platform have great application potential.

Analysis of vibration isolation performance of parallel air spring system for precision equipment transportation

Precision equipment is usually accompanied with vibrations during road or railway transportation. Sometimes the vibration exceeds the given limit, leading to the damage of the equipment. It is necessary to control the vibration during the transportation. However, it is still difficult to adjust the parameters of a designed vibration isolation system for the transportation of different precision equipment under various road conditions. Aiming at satisfying the vibration isolation requirements of different precision equipment, this paper proposes a parallel air spring vibration isolation system based on the principle of limiting lateral deflection. According to the measured parameters, a rigid-body dynamics simulation model of parallel air spring vibration isolation system is established. Then its feasibility is verified, and the optimal parameters of the vibration isolation system are obtained by a simulation. Finally, the vibration isolation system is built and installed in the equipment to carry out the real vehicle transportation test. The test results show that the transportation vibration isolation system based on the parallel air spring structure has not only excellent vibration isolation efficiency but also acceptable lateral stability. The research results in this paper can provide a reference for the design of the vibration isolation system for the large precision equipment transportation.

Research on Airborne Active and Passive Composite Vibration Isolation Optoelectronic Stabilization Platform System

According to the vibration isolation requirements of a certain type of optoelectronic stability platform, an active-passive composite vibration isolation system based on the hierarchical vibration isolation idea is designed. The system uses the active and passive hybrid vibration isolator as the outer frame damper, and the two-axis four-frame optoelectronic system. The stable platform has a reasonable layout. The system realizes the three-way stiffness, removes the line vibration coupling in the three directions of the system, establishes the three-dimensional model of the vibration reduction system in UG, and uses the Altair HyperMesh/OptiStruct software for finite element analysis. The results show that the vibration isolation system meets the design requirements.

The optimal design of track magneto-rheological vibration isolator and performance testing

It is very significant that magneto-rheological (MR) vibration isolator with adjustable parameters can be utilized to improve the low frequency vibration of a track system. Since the peak damping force of a prototype MR vibration isolator is too small, an optimum design method for the winding area structure of a new MR isolator is proposed. And the relationship of coil ampere-turns and coil power dissipation is derived. Moreover, the software Maxwell for electromagnetic field analysis is used to optimize the structure design of the new isolator. The MR vibration isolator is designed in squeeze mode and its performance is tested by MTS 858. The experimental results show that when the excitation loading of 2 Hz and 0.6 mm amplitude, and the 0.5 A drive current are applied, the maximum damping force can be increased by 58.3%, and damping dissipation capacity can be increased by 93.5%. When the excitation frequency and amplitude remain contant and the initial position of the piston keep changed, the vibration isolator can show variable characteristics of stiffness and damping, which is feasible to meet different vibration isolation requirements. This study could offer reference value for the optimal design of vibration isolation devices under similar conditions.

Active Hybrid Control Algorithm with Sky-Hook Damping and Lead-Lag Phase Compensation for Multi-DOFs Ultra-Low Frequency Active Vibration Isolation System

With the improvement of performance in the ultra-precision manufacturing engineering, the requirements for vibration isolation have become more stringent. In order to obtain a wider effective bandwidth and a higher performance of a multi-DOFs active vibration isolation system (AVIS), active hybrid control (AHC) technology is applied in this paper. AHC technology comprises a feedback active control (FBAC) technology and a feedforward active control (FFAC) technology. Absolute velocity feedback is employed to establish a sky-hook damping technology in FBAC technology. Velocity feedforward of base platform is adopted to build a lead-lag phase compensation (LLPC) technology in FFAC technology. Further, a coordinate vector conversion from unit level to system level is mentioned to describe the dynamic characteristic of the six DOFs AVIS applied in the ultra-precision field. And with the assistance of the transformed coordinate vector, the dynamic model of system level is built. Based on the establishment of the dynamic model and the research of AHC, an experimental platform which constitutes three vibration isolators and a real-time active control system is set up. The experimental results indicate that the amplitude of the resonant peak is further reduced significantly, compared to the general feedback control. And simultaneously active effective bandwidth is extended. AHC technology with sky-hook damping algorithm and LLPC control algorithm is verified to be more effective.

Description of the traction characteristics of the neodymium compensators of the automatic vibration isolations

In this paper the method of calculation of neodymium magnets was presented. The calculation of the neodymium magnets characteristics and stiffness correctors of the vibration isolator according to the requirements for vibration isolation devices with stiffness compensators was performed. This research has been performed with the support of the President scholarship for young scientists, order No. 184 of Ministry of education and science of the Russian Federation of the 10th of March 2015.

An Ultra-Low Frequency Two DOFs’ Vibration Isolator Using Positive and Negative Stiffness in Parallel

With the improvement of performance in the ultra-precision manufacturing engineering, the requirements for vibration isolation have become increasingly stringent. In order to get wider effective bandwidth and higher performance of vibration isolation in multiple DOFs system, an ultra-low frequency two DOFs’ vibration isolator with positive and negative stiffness in parallel (PNSP) is proposed. The two DOFs’ isolator which combines a positive stiffness (PS) air spring with a negative stiffness (NS) magnetic spring in parallel and combines a PS flat spring with an NS inverted pendulum in parallel is designed to reduce the natural frequency and broaden the effective bandwidth in horizontal and vertical direction. Based on this structure, stiffness models of different components in different directions are established. Compared with a PS isolator, it possesses the characteristic of high-static-low-dynamic stiffness. The simulation curves also provide strong evidence. Last, a real-time active control system and a spectrum testing and analysis system are used for the contrast experiment between the mentioned PNSP structure and PS only. The experimental results demonstrate that the isolator with PNSP can obviously reduce the natural frequency to 1 Hz and simultaneously maintain the stability of the system and consequently verify the validity and superiority of the mentioned structure.

Design of a solenoid valve based active engine mount

This paper describes the design of a versatile and fully controllable active engine mount. The proposed active mount is capable of addressing vibration isolation requirements at various driving conditions. This design addresses a better ride quality that has always been demanded by the automotive industry, as well as satisfying sophisticated vibration isolation requirements for the unconventional engines, i.e. variable displacement, and hybrids. The proposed engine mount replaces the decoupler of the original design with a solenoid actuator. The mathematical model of the active mount is obtained. The dynamic characteristics of the mount are shown to be highly controllable over the operating frequency range of excitation in engines. The effectiveness of the developed active engine mount for various working conditions of engine is also evaluated. Several driving conditions are investigated and proper control strategies are utilized to demonstrate the mount's capability to fulfill the isolation requirements for each condition. The promising results, in addition to compactness, low cost, fail safety, and durability are the main advantages of the proposed active engine mount, which makes it viable for automotive applications.