An Ultra-Low Frequency Parallel Connection Nonlinear Isolator for Precision Instruments

Abstract

In order to improve the working performance of precision instruments, it is desirable to isolate ambience wideband vibrations. Nonlinear isolator is superior to linear isolator. In this paper, a novel combined positive and negative stiffness isolator is developed based on the analysis of the mechanism of negative stiffness, whose negative stiffness cancels much of the positive stiffness of the elastic element in the vicinity of the balance point. The stiffness at the balance point has a nonlinear characteristic and the net stiffness tends to be zero. This type of isolator has high support stiffness as well as low vibration stiffness. Its inherent frequency can be adjusted to zero by adjusting the initial deformation of the elastic elements of the negative stiffness mechanism. Experimental results show that the inherent frequency of the isolator can be adjusted from 10 Hz to 1 Hz. The isolation bandwidth of the isolator is widened and the performance of isolation is distinctly enhanced.

Energy Flow Theory of Nonlinear Dynamical Systems with Applications

“…For ground vibration tests of aircrafts, a nonlinear supporting system was proposed and used (Molyneux 1958;Xing 1975) to obtain a very low supporting frequency. The detailed investigations on designs, practical techniques and performance of nonlinear suspension systems were reported quite late, see, for example, Alabuzhev et al (1989), Platus (1992), Zhang et al (2004), Carrela, Brennan & Waters (2007), Carrela et al (2008), Kovaic, Brennan & Waters (2008), Ahn (2008), Cao et al (2008ab), Liu, Chen & Cao (2010). More recently, Araki et al (2013) presented the effective designs of quasizero-stiffness vibration isolators for their restoring forces to satisfy the conditions resisting large self-weight and to have the tangent stiffness close to zero around the static equilibrium position.…”

Design and Characteristics Analysis of a Nonlinear Isolator Using a Curved-Mount-Spring-Roller Mechanism as Negative Stiffness Element

“…For example, Virgin and Davis created a nonlinear vibration isolator with curved beam structures [6]. Zhang et al [7] used a beam under axial force at its two ends to get the same kind of stiffness. Molyneux [8] developed a structure composed of two inclined springs to get very low stiffness.…”

Theoretical Design and Characteristics Analysis of a Quasi-Zero Stiffness Isolator Using a Disk Spring as Negative Stiffness Element

“…Platus [9] utilized two compressed bars hinged at the center to be the negative element. Zhang et al [10] added a beam under axial force to a positive stiffness spring. Carrella et al [11] proposed a high-static-low-dynamic stiffness (HSLDS) isolator with a vertical linear spring in parallel with two oblique linear springs.…”