On the Vibration Isolation of Flexible Structures

2006 ◽  
Vol 74 (3) ◽  
pp. 415-420 ◽  
Author(s):  
Y. Q. Tu ◽  
G. T. Zheng
Keyword(s):  
Vibration Isolation ◽  
Flexible Structures ◽  
Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Isolation Frequency ◽  
Vibration Attenuation ◽  
Vibration Transmissibility ◽  
Structure Vibration ◽  
Modal Space

Although the study of vibration isolation has a very long history, when an isolated structure is so flexible that it cannot be properly approximated with a rigid body or a single-degree-of-freedom model, its vibration isolation brings about some new questions and problems. By transforming the dynamic equation of motion of the coupled structure formed by the isolator and the isolated structure into the modal space and following the tradition of studying features of the vibration transmissibility across the isolator, questions and problems associated with the flexible structure vibration isolation are studied. It is found from the study that a lower isolation frequency and a higher damping level can both increase the isolation effectiveness, the isolated structure is a vibration absorber to the isolator, and a combination of the vibration isolation and the vibration attenuation can be more effective in mitigating the vibration. A numerical example of the whole spacecraft vibration isolation has proved the above conclusions.

Analytical Study of Vibration Isolation Between a Pair of Flexible Structures

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
G. T. Zheng ◽  
Y. Q. Tu
Keyword(s):  
Vibration Isolation ◽  
Coupling Effect ◽  
Flexible Structures ◽  
Flexible Structure ◽  
Vibration Attenuation ◽  
Vibration Transmissibility ◽  
Proper Design ◽  
Structure Vibration ◽  
Flexible Foundation ◽  
Isolation Performance

The problem of flexible structure vibration isolation on a flexible foundation is analytically investigated by simplifying the vibration isolation as single axis isolation, which can be realized by a proper design, and the problem of the whole spacecraft vibration is taken as an example for the application as both the spacecraft (isolated structure) and the launch vehicle (foundation) are flexible structures. A numerical example of the whole spacecraft vibration isolation is also provided for further explaining those conclusions derived from the analytical studies. It is found from the study that the isolator’s damping is important for attenuating the vibration and that weakening the isolator’s stiffness has the same effect as increasing its damping. However, a weaker stiffness means a weaker coupling among the structures and may magnify the vibration at some resonant frequencies, which are close to those of individual structures. The coupling effect of the structure’s flexibility on the isolation may be significant in some cases and a coupling analysis is essential for ensuring the isolation performance. Because of the importance of the isolator’s damping in reducing the vibration transmissibility and the vibration of the coupled structure, it is more appropriate to describe the vibration isolation of the flexible structure as vibration attenuation.

Vibration Reduction and Isolation Using on-Off Control at Spring Support Joint: Application to Multi-Degrees-of-Freedom System

1999 ◽  
Author(s):  
Hideya Yamaguchi ◽  
Masahito Yashima ◽  
Takao Yoshikawa
Keyword(s):  
Degrees Of Freedom ◽  
Vibration Isolation ◽  
Degree Of Freedom ◽  
Mass System ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Joint Application ◽  
Friction Joint ◽  
Modal Space ◽  
Spring Support

Abstract In order to achieve vibration isolation and reduction for a multi-degrees-of-freedom system, this paper develops the on-off control that has been proposed on the single-degree-of-freedom system by the authors. The method introduces an additional spring and mass system, and the additional mass is designed to control the clamping friction force by the friction joint switching mechanism. The non-linear control law for the single-degree-of-freedom system is applied to a multi-degrees-of-freedom system by incorporating the idea of the independent modal space control (IMSC) method. Numerical simulations and experiments demonstrate the effectiveness of the method.

Forced Vibration of Systems With Nonlinear, Nonsymmetrical Characteristics

1957 ◽  
Vol 24 (3) ◽  
pp. 435-439
Author(s):  
S. Mahalingam
Keyword(s):  
Approximate Solution ◽  
Linear System ◽  
Nonlinear Vibration ◽  
Forced Vibration ◽  
Free Vibrations ◽  
Frequency Function ◽  
Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Nonlinear Vibration Absorber ◽  
Single Degree

Abstract A one-term approximate solution is given for the amplitudes of steady forced vibration of a single-degree-of-freedom system with a nonlinear (nonsymmetrical) spring characteristic. The method is similar to that of Martienssen (1), but the construction uses a modified curve (or “frequency function”) in place of the actual spring characteristic, the curve being so chosen that it gives the correct frequency for free vibrations. The method is extended to deal with a nonlinear vibration absorber fitted to a linear system.

Three-Element Vibration Absorber–Inerter for Passive Control of Single-Degree-of-Freedom Structures

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Abdollah Javidialesaadi ◽  
Nicholas E. Wierschem
Keyword(s):  
Passive Control ◽  
Translational Motion ◽  
Tuned Mass Damper ◽  
Degree Of Freedom ◽  
Superior Performance ◽  
Underlying Structure ◽  
Vibration Absorber ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Mass Damper

In this study, a novel passive vibration control device, the three-element vibration absorber–inerter (TEVAI) is proposed. Inerter-based vibration absorbers, which utilize a mass that rotates due to relative translational motion, have recently been developed to take advantage of the potential high inertial mass (inertance) of a relatively small mass in rotation. In this work, a novel configuration of an inerter-based absorber is proposed, and its effectiveness at suppressing the vibration of a single-degree-of-freedom system is investigated. The proposed device is a development of two current passive devices: the tuned-mass-damper–inerter (TMDI), which is an inerter-base tuned mass damper (TMD), and the three-element dynamic vibration absorber (TEVA). Closed-form optimization solutions for this device connected to a single-degree-of-freedom primary structure and loaded with random base excitation are developed and presented. Furthermore, the effectiveness of this novel device, in comparison to the traditional TMD, TEVA, and TMDI, is also investigated. The results of this study demonstrate that the TEVAI possesses superior performance in the reduction of the maximum and root-mean-square (RMS) response of the underlying structure in comparison to the TMD, TEVA, and TMDI.

scholarly journals Active vibration isolation of high precision machines

2010 ◽  
Vol 1 (MEDSI-6) ◽  
Author(s):  
C. Collette ◽  
S. Janssens ◽  
K. Artoos ◽  
C. Hauviller
Keyword(s):  
Active Control ◽  
High Precision ◽  
Vibration Isolation ◽  
Control Strategies ◽  
External Disturbances ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Atomic Force ◽  
Active Vibration ◽  
Precision Machines

This paper provides a review of active control strategies used to isolate high-precisionmachines (e.g. telescopes, particle colliders, interferometers, lithography machines or atomic force microscopes) from external disturbances. The objective of this review is to provide tools to develop the best strategy for a given application. Firstly, the main strategies are presented and compared, using single degree of freedom models. Secondly, the case of huge structures constituted of a large number of elements, like particle colliders or segmented telescopes, is considered.

Extending Den Hartog’s Vibration Absorber Technique to Multi-Degree-of-Freedom Systems

2004 ◽  
Vol 127 (4) ◽  
pp. 341-350 ◽  
Author(s):  
Mehmet Bulent Ozer ◽  
Thomas J. Royston
Keyword(s):  
Matrix Inversion ◽  
Degree Of Freedom ◽  
Vibration Absorber ◽  
Vibration Absorbers ◽  
Single Degree Of Freedom ◽  
Inversion Theorem ◽  
Single Degree ◽  
Main System ◽  
Dynamic Vibration Absorbers ◽  
Invariant Points

The most common method to design tuned dynamic vibration absorbers is still that of Den Hartog, based on the principle of invariant points. However, this method is optimal only when attaching the absorber to a single-degree-of-freedom undamped main system. In the present paper, an extension of the classical Den Hartog approach to a multi-degree-of-freedom undamped main system is presented. The Sherman-Morrison matrix inversion theorem is used to obtain an expression that leads to invariant points for a multi-degree-of-freedom undamped main system. Using this expression, an analytical solution for the optimal damper value of the absorber is derived. Also, the effect of location of the absorber in the multi-degree-of-freedom system and the effect of the absorber on neighboring modes are discussed.

An Optimization Approach to Vibration Isolation of Rigid Bodies

1997 ◽  
Vol 25 (3) ◽  
pp. 165-175
Author(s):  
P. S. Heyns
Keyword(s):  
Design Problem ◽  
Vibration Isolation ◽  
Rigid Bodies ◽  
Degree Of Freedom ◽  
Optimization Approach ◽  
Local Minima ◽  
Single Degree Of Freedom ◽  
Single Degree

The conventional single-degree-of-freedom approach to isolator design dealt with in most undergraduate curricula, is not always adequate for the design of practical isolator systems. In this article, an optimization approach to the design problem is presented and the viability of the approach demonstrated. It is, however, also shown that multiple local minima may exist and that due care should be exercised in the application of the method.

Principle, modeling, and control of a magnetorheological elastomer dynamic vibration absorber for powertrain mount systems of automobiles

2016 ◽  
Vol 28 (16) ◽  
pp. 2239-2254 ◽  
Author(s):  
Fu-Long Xin ◽  
Xian-Xu Bai ◽  
Li-Jun Qian
Keyword(s):  
Frequency Shift ◽  
Vibration Isolation ◽  
Vibration Absorber ◽  
Magnetorheological Elastomer ◽  
Dynamic Vibration Absorber ◽  
Vibration Absorption ◽  
Dynamic Vibration ◽  
Passive Vibration Isolation ◽  
Vibration Attenuation ◽  
Vibration Attenuation Performance

This article proposes and validates the principle of a new magnetorheological elastomer (MRE) dynamic vibration absorber (DVA) for powertrain mount systems of automobiles. The MRE DVA consists of a vibration absorption unit and a passive vibration isolation unit. The vibration absorption unit composed of a magnetic conductor, a shearing sleeve, a bobbin core, an electromagnetic coil, and a circular cylindrical MRE is utilized to absorb the vibration energy, and the passive vibration isolation unit is used to support the powertrain. The finite element method is employed to validate the electromagnetic circuit of the MRE DVA and obtain the electromagnetic characteristics. The theoretical frequency-shift principle is analyzed via the established constitutive equations of the circular cylindrical MRE In order to demonstrate how the parameters of the MRE influence the vibration attenuation performance, the MRE DVA is applied to a powertrain mount system to replace the conventional passive mount. The frequency-shift property of the vibration absorption unit and the vibration attenuation performance of the MRE DVA on the powertrain mount system are experimentally tested. To validate and improve the vibration attenuation performance for the semi-active powertrain mount systems, an optimal variable step algorithm is proposed for the MRE DVA and numerical experiments are carried out.

Improved integral force feedback controllers for lightweight flexible structures

2020 ◽  
pp. 107754632097454
Author(s):  
Florian Lacaze ◽  
Ahmad Paknejad ◽  
Didier Remond ◽  
Simon Chesne
Keyword(s):  
Control System ◽  
Force Feedback ◽  
Flexible Structures ◽  
Feedback Controller ◽  
Degree Of Freedom ◽  
Feedback Controllers ◽  
Single Degree Of Freedom ◽  
Cable Structure ◽  
Optimal Tuning ◽  
Single Degree

This study studies the performance of an integral force feedback controller for increasing the damping of lightweight flexible structures. Both methods of maximum damping and [Formula: see text] optimization are used to tune the parameters of the control system. Two modifications of the integral force feedback are proposed to compensate the effects of a soft stiffness to increase the authority of the actuator. Higher damping values are obtained by adding feedback terms to the integral force feedback. Optimal tuning, required actuator force, and stability are also discussed based on an academic model of a single-degree-of-freedom cable structure.

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