Vibration Isolation Module Research Articles

The ONR three octave research array at Penn State

A new, large diameter towed research array has been built to support the experimental efforts of the Office of Naval Research (ONR) Ocean Acoustics Program. Array development was a collaborative effort between the Centre for Maritime Research and Experimentation (CMRE) in La Spezia, Italy, and the Penn State Applied Research Laboratory (PSU). PSU chose the array specifications based on discussions within the underwater acoustics community, prior measurement experience, cost efficiency, and flexibility in scientific measurements, while CMRE designed and assembled the array. The design includes three, forward-nested acoustic apertures cut for 1, 2, and 4 kHz, and hence, has been dubbed the Three Octave Research Array (THORA) in deference to its predecessor, the Five Octave Research Array (FORA). However, this system has a modular design to allow addition of acoustic apertures if scientific interest and sponsor support warrant. The array currently consists of a 50 m acoustic module and a 25 m vibration isolation module to help isolate the acoustic module from cable strum. This ship towed system has nearly 1 km of tow cable and a maximum measurement depth of 500 m. The array’s design, its use in the ONR NESMA23 Pilot experiment, and data quality will be discussed.

Development of an innovative three-dimensional vibration isolation bearing

This paper presented an innovative three-dimensional vibration isolation bearing (3D-VIB) to mitigate horizontal seismic action and rail-induced vertical vibration. The 3D-VIB was composed of a thick laminated rubber bearing acting as the vertical vibration isolation module and a friction pendulum acting as the horizontal seismic isolation module. The thick laminated rubber bearing was used as a part of the slider in the friction pendulum. The compression performance of 3D-VIB was decoupled from its shear performance by concentrating the compressive deformation into the thick rubber bearing while shear deformation occurred independently in the friction pendulum module. The bearing capacity, vertical and horizontal properties of a full-scale 3D-VIB specimen were tested. In the test, the ultimate bearing capacity of 3D-VIB was 7 times that of the design compressive load of normal service condition. The vertical stiffness of the specimen under seismic vibration and vertical rail-induced vibration were tested separately. It was found that the vertical stiffness of the specimen under rail-induced vibration was 1.55 times higher than the vertical stiffness under seismic vibration. The horizontal performance of the 3D-VIB was characterized by stable parallelogram-shaped hysteretic curves similar to that of the traditional friction pendulum system. A user-defined element was developed and incorporated into ABAQUS to simulate the mechanical behavior of the 3D-VIB under different loading conditions, and simulation results agreed with the test results. The responses of a steel structure equipped with the 3D-VIB, while subjected to earthquake ground motions and rail-induced vibrations, respectively, were analyzed and compared with the non-isolated one. The analysis results suggested that with the installation of the 3D-VIB, the maximum inter-story drift ratio of the structure under maximum considered earthquake was reduced by about 88%. The average maximum transient vibration value of the rail-induced vertical vibration at the typical points of the conventional model was 86.2 dB, while that in the 3D-isolated model was 78.6 dB, the vibration reduction was 7.6 dB.

Modeling analysis of a novel hybrid 6-DOF vibration isolation platform for sensitive instruments

The inevitable vibration caused by normal operation of the spacecraft in orbit will interfere sensitive instruments, such as space telescope, reconnaissance camera, space interferometer. Serious vibrations affect the accuracy and reliability of the sensitive instruments, even cause flight mission failed. This paper presents a hybrid 6-DOF vibration isolation platform (HVIP) with six degree-of-freedom for active vibration isolation of the space sensitive instruments. The HVIP is composed of three orthogonal vibration isolation module, which composed of the active piezoelectric actuator and passive rubber isolator. The dynamic model of the HVIP is established based Lagrange equation approach. Finally, the numerical simulations are performed to verify the vibration isolation effect of the HVIP.

Development of Active Microvibration Isolation System for Precision Space Payload

In this study, an active microvibration isolation system is developed for precision space payload. Vibrational environment affects the performance and reliability of measuring instruments. To improve the measurement accuracy of the precision space payload, an active vibration isolation system based on eight vibration isolation modules, which are applied for microvibration isolation on the satellite, is designed. A vibration suppression control strategy for multiple degrees of freedom is studied. A hybrid control method involving a feedback and a feedforward controller based on a nonlinear tracking differentiator and an nth-order weak integrator, respectively, was adopted to optimize the suppression effect of microvibration. As a result, the microvibration of the order of mg can be reduced to the order of μg through the active control of modules. Research experiment results show that the root cumulative power spectral density of the systemic sensitive frequency band in the range of 0.5–200 Hz, i.e., microvibration frequency band in the optical reference cavity, has been reduced to in the order of μg in three directions, which satisfied the requirements of aerospace engineering.

Theoretical Design of a Novel Vibration Energy Absorbing Mechanism for Cables

A novel design of a vibration energy absorbing mechanism (VEAM) that is based on multi-physics (magnetic spring, hydraulic system, structural dynamics, etc.) for cable vibration is proposed. The minimum working force of the hydraulic cylinder has been exploited in this design in order to combine a non-linear stiffness vibration isolation module that is composed of permanent magnetic springs with hydraulic viscous vibration damping modules. In response to different environmental vibration impacts, VEAM can automatically switch the vibration control modes without an electronic mechanism. Additionally, the non-contact design effectively reduces the wear that is induced by the reciprocating motion of the small amplitude of the hydraulic viscous dampers. The proposed mechanism is explained and a theoretical model is established. The transmissibility of the two modules at a single degree of freedom is derived using the harmonic balance method. After that, a series of variable control numerical simulations were performed for each important parameter. Empirical rules for designing the system were created by comparing the influence of each parameter on the vibration isolation performance of the entire system.

Identification and Removal of Non-acoustic Noise in Towed Array Sonar Using F-Κ Transform for Enhanced Torpedo Detection

Low frequency passive towed array sonar is an essential component in a torpedo detection system for surface ships. Compact towed arrays are used for torpedo detection and they will be towed at higher towing speeds compared to conventional towed array sonars used for surveillance. Presence of non-acoustic noise in towed array sensors at higher towing speeds degrades torpedo detection capability at lower frequencies. High wavenumber mechanical vibrations are induced in the array by vortex shedding associated with hydrodynamic flow over the array body and cable scope. These vibrations are known to couple into the hydrophone array as nonacoustic noise sources and can impair acoustic detection performance, particularly in the forward end fire direction. Lengthy mechanical vibration isolation modules can isolate vibration induced noise in towed arrays, but this is not recommended in a towed array which is towed at high speeds as it will increase the drag and system complexity. An algorithm for decomposing acoustic and non-acoustic components of signals received at sensor level using well known frequency-wavenumber transform (F-K transform) is presented here. Frequency-wavenumber diagrams can be used for differentiating between acoustic and non-acoustic signals. An area of V shape is identified within the F-K spectrum where acoustic energy is confined. Energy outside this V will highlight non-acoustic energy. Enhanced simultaneous spatio-temporal and spatio-amplitude detection is possible with this algorithm. Performance of this algorithm is validated through simulation and experimental data.

Optimization and finite-frequency H∞ control of active suspensions in in-wheel motor driven electric ground vehicles

In this paper, the parameter optimization and H∞ control problem of active suspensions equipped in in-wheel motor driven electric ground vehicles are investigated. In order to better isolate the force transmitted to motor bearing, dynamic vibration absorber (DVA) is installed in the active suspension. Parameters of the vibration isolation modules are also optimized in order to achieve better suspension performances. As the human body is much sensitive to vibrations between 4 and 8Hz, a finite-frequency state-feedback H∞ controller is designed to achieve the targeted disturbance attenuation in the concerned frequency range while other performances such as road holding capability and small suspension deflection are also maintained. The performance of the proposed finite-frequency H∞ controller is compared with that of an entire frequency one, simulation results prove the effectiveness of the proposed control method.

Longitudinal Vibration Response of a Vibration Isolation Module with Kevlar-29 Fabric Strength Member

The longitudinal vibration response of a simplified model of a vibration isolation module used in an underwater towed acoustic sensor array is estimated by finite element method and validated by impact resonance tests using a lumped mass system. The viscoelastic properties of the Kevlar-29 fabric strength member of the vibration isolation module are determined from transient tensile tests at different preloads and strain rates based on a five-parameter discrete viscoelastic model. Close agreement between finite element estimates and experimental results are obtained when strain rates of the strength member during viscoelastic parameter estimation tests and impact tests are matched.

Retrofitting A Passive Vibration Isolation System with Zero-Compliance Modules

A vibration isolation module with zero-power magnetic suspension is developed to retrofit a passive vibration isolation system to improve the performance against direct disturbance. In the module, the zero-power magnetic suspension mechanism is connected in series with a normal spring through a middle mass. This structure can generate zero compliance to direct disturbance while the transmitted vibration is still reduced. Such zero- compliance module was actually designed and fabricated. The characteristics of the fabricated module were studied experimentally. A passive vibration isolation system using air springs were retrofitted with four modules. It was demonstrated that the performance against direct disturbance was improved significantly.

Tests on a New Vibration Isolation Module

This paper proposes a new isolation module, which is composed of double-layer tubular structures and the middle filling material. The hoop vibration isolation module is set somewhere out of pier footings of the footbridge, which presents some advantages such as good reliability, convenient construction, limited occupation areas, little damage to the environment and low cost. The energy of the vibration wave is confined at the most degree outside of the bridge pier, which reduces the vibration of beams and piers of footbridge. The present work gives an account of the experimental investigation on mitigation effects of the new vibration isolation module. The horizontal and vertical accelerations at test points under various working conditions were presented in this paper. Vibration levels were calculated to analyze the regularity of vibration attenuation, compared with no measures of vibration isolation. The results can provide some basic data for the mitigation of environment vibration arising from traffic loads.

Investigation on Vibration Reduction Effects of a New Vibration Isolation Module for Pier Foundation

This paper presents a new vibration isolation module which is set somewhere out of pier footings of footbridges. The isolation vibration effect of the vibration isolation module was analysed by means of experiment and FEM analysis. The attenuation decibels of the vibration strength were measured and researched under various working conditions. Making use of the finite element program, the new vibration isolation module was simulated and calculated. That the calculated results were in good agreement with the measured ones indicated the reliability of the numerical model. The simulation and measured results suggest that vibration reduction effects are satisfactory. The results can provide reference for vibration attenuation and vibration isolation of footbridges.

Numerical Analysis and Tests on Vibration Reduction Effects of a New Vibration Isolation Module

The vibration reduction effects of a new vibration module which was composed of double-layer tubular structures and the middle filling material were investigated with the methods of numerical simulation and experiment. The attenuation decibels of the vibration levels were measured and analyzed under various working conditions. It is testified that results of numerical simulation of the soil vibration which are in good agreement with the measured data are credible. It is indicated by the analysis results that the vibration isolation module has good effect on damping vibration in each frequency band. The results can provide references for the design of vibration isolation modules for pier foundation.

A three-axis vibration isolation system using modified zero-power controller with parallel mechanism technique

This paper proposes a module-type three-degree-of-freedom vibration isolation system using modified zero-power control. Three vibration isolation modules are connected together using parallel mechanism to control 3-DOF motions. Each module consists of a common base, an individual middle mass and a common isolation table. The base to the middle mass is suspended by positive springs generated by active and passive system, and the middle mass and the isolation table is connected by negative spring realized by active-type modified zero-power control. The developed system could realize zero-compliance to direct disturbances as well as good ground vibration isolation. Furthermore, the isolation table is supported by a weight support mechanism for supporting heavy payloads. In the previous research, a concentrated middle mass with redundant actuators, in the vertical and horizontal directions, were used. Therefore, a vibration isolation system is proposed in this work using modular concept to overcome those drawbacks. Each module is controlled separately by decentralized control technique, and three modules can be used for three-degree-of-freedom of motion control. Therefore, no redundancy of actuator is occurred. Moreover, an improved zero-power controller is presented that can adjust negative stiffness instead of conventional zero-power controller. The results obtained from analytical and experimental studies show that the modular technique is reliable and efficient approach to vibration control, and represents a suitable alternative to the conventional active vibration isolation systems.

Exploratory materials development for towed array sensor systems

Extended towed array sensor systems are used for geophysical sensing and exploration in the petroleum industry, and for detection of submersible objects in naval applications. Many of the polymeric materials considered for use in towed array hoses either did not possess the necessary aging and weathering resistance; provided satisfactory self‐noise performance at higher temperatures but were unacceptable in cold water; or experienced changes in self‐noise through fill‐fluid permeation and chemical reaction. There has been a need to develop and evaluate new classes of elastomers for use as hose wall materials. Array self‐noise performance can also be improved through proper selection of polymers for use in vibration isolation modules for low‐frequency towline excitation. Thermoplastic elastomers offer significant advantages over other types of elastomers in cost and ease of processing. Results are presented for both conventional elastomers and thermoplastics to show how these materials can be selected for ...

Vibration isolation module for sonar towed arrays

First Page

Vibration isolation module

First Page