Nonlinear vibration isolator with adjustable restoring force

Abstract This paper presents a vertical quasi-zero stiffness (QZS) vibration isolator with a mechanism for adjusting restoring force. QZS vibration isolators have high initial stiffness and QZS around the static equilibrium position. This way, excessive deformation due to self-weight can be avoided while having enough vibration reduction capability to dynamic excitations. One of the main issues left for QZS vibration isolators is the difficulty in keeping the vibration reduction capability when the vibration isolated object is replaced. In such a case, adjustment of its restoring force becomes necessary in accordance with the self-weight of the newly placed vibration isolated object. This paper attempts to address this issue by proposing a mechanism that enables quick and easy adjustment of the restoring force of a QZS vibration isolator. The proposed mechanism consists of cranks and a screw jack. With the present mechanism, the restoring force provided by horizontally placed springs can be converted into the vertical restoring force of the vibration isolator. In the conversion, the vertical resisting force can be adjusted simply by applying and removing torque to the screw jack to change and hold the angle of inclined bars placed in the cranks. In this study, a prototype of a class of QZS vibration isolator having the proposed mechanism is produced. Shaking table tests are performed to demonstrate the efficacy of the present mechanism, where the produced prototype is subjected to various sinusoidal and earthquake ground motions. It is demonstrated through the shaking table tests that the produced prototype can reduce the response acceleration within the same tolerance even when the mass of the vibration isolated object is changed.

[1]  Ivana Kovacic,et al.  Effect of a static force on the dynamic behaviour of a harmonically excited quasi-zero stiffness system , 2009 .

[2]  P. M. Alabuzhev,et al.  Vibration protecting and measuring systems with quasi-zero stiffness , 1989 .

[3]  Timothy P. Waters,et al.  Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness , 2012 .

[4]  David L. Platus,et al.  Negative-stiffness-mechanism vibration isolation systems , 1999, Optics + Photonics.

[5]  D. Blair,et al.  High performance vibration isolation using springs in Euler column buckling mode , 2002 .

[6]  W. G. Molyneux,et al.  The Support of an Aircraft for Ground Resonance Tests , 1958 .

[7]  Raouf A. Ibrahim,et al.  Recent advances in nonlinear passive vibration isolators , 2008 .

[8]  Ben S. Cazzolato,et al.  Theoretical design parameters for a quasi-zero stiffness magnetic spring for vibration isolation , 2009 .

[9]  Takeshi Masui,et al.  Response of vibration-isolated object to ground motions with intense vertical accelerations , 2011 .

[10]  Donatello Cardone,et al.  Re-centring capability of flag-shaped seismic isolation systems , 2012, Bulletin of Earthquake Engineering.

[11]  Michael J. Brennan,et al.  Static analysis of a passive vibration isolator with quasi-zero-stiffness characteristic , 2007 .

[12]  Michael J. Brennan,et al.  On the design of a high-static-low-dynamic stiffness isolator using linear mechanical springs and magnets , 2008 .

[13]  R. B. Davis,et al.  Vibration isolation using buckled struts , 2003 .

[14]  Hyeong-Joon Ahn.  Performance limit of a passive vertical isolator using a negative stiffness mechanism , 2008 .

[15]  C.-M. Lee,et al.  Design of springs with “negative” stiffness to improve vehicle driver vibration isolation , 2007 .

[16]  Dimitris C. Lagoudas,et al.  Pseudoelastic SMA Spring Elements for Passive Vibration Isolation: Part I – Modeling , 2004 .

[17]  Jagmohan Humar,et al.  Dynamic of structures , 1989 .

[18]  R. Plaut,et al.  Analysis of buckled and pre-bent fixed-end columns used as vibration isolators , 2005 .

[19]  Yeping Xiong,et al.  Dynamics and power flow behaviour of a nonlinear vibration isolation system with a negative stiffness mechanism , 2013 .

[20]  Takeshi Masui,et al.  Vertical vibration isolator having piecewise‐constant restoring force , 2009 .

[21]  Stanley E. Woodard,et al.  Nonlinear behavior of a passive zero-spring-rate suspension system , 1991 .

[22]  J. Oden,et al.  Contact Problems in Elasticity: A Study of Variational Inequalities and Finite Element Methods , 1987 .

[23]  R. Plaut,et al.  Vibration isolation using extreme geometric nonlinearity , 2008 .

[24]  I. Kovacic,et al.  A study of a nonlinear vibration isolator with a quasi-zero stiffness characteristic , 2008 .

[25]  Ivana Kovacic,et al.  On the force transmissibility of a vibration isolator with quasi-zero stiffness , 2009 .

[26]  David J. Wagg,et al.  Dynamic Analysis of High Static Low Dynamic Stiffness Vibration Isolation Mounts , 2013 .

[27]  Gianluca Gatti,et al.  On the response of a harmonically excited two degree-of-freedom system consisting of a linear and a nonlinear quasi-zero stiffness oscillator , 2010 .

[28]  Kyoung Kwan Ahn,et al.  A vibration isolation system in low frequency excitation region using negative stiffness structure for vehicle seat , 2011 .

[29]  R. Plaut,et al.  Vibration isolation using buckled or pre-bent columns—Part 1: Two-dimensional motions of horizontal rigid bar , 2008 .