Vertical vibration isolator having piecewise‐constant restoring force

Abstract

SUMMARYWe present a vertical vibration isolator having a piecewise-constant restoring force, which belongs to a class of passive and nonlinear vibration isolators. In vertical vibration isolation, direct use of low-stiffness elements leads to unacceptably large deformations due to self-weight. To overcome the difficulty, we apply a combination of constant-force springs, each of which sustains a constant load regardless of its stretch. By arranging the constant-force springs, so that the isolator has a piecewise-constant restoring force, we alleviate the problem of the excessive deformation caused by self-weight, provide stability at the static equilibrium state along with the self-centering capability, and realize a large stroke while keeping the mechanism simple and compact. Further, we attempt to limit the response acceleration within a tolerance regardless of the frequency spectrum and the magnitude of earthquake ground motions. We demonstrate the effectiveness of the present isolator through shaking table tests and numerical simulations.

Adjustable vertical vibration isolator with a variable ellipse curve mechanism

“…Therefore, the horizontal mechanism has a lower risk of lack of stroke and realize a more compact isolator. These are advantages over other vertical isolators proposed in the literature including the authors' previous work . However, regardless of long stroke, an impact absorption mechanism should be installed for practical use.…”

“…Quasi‐zero‐stiffness vibration isolators are designed so that their restoring forces satisfy the following two conditions: (i) initial stiffness, which resists self‐weight and is large, and (ii) the tangent stiffness, which resists dynamic load and is close to zero around the static equilibrium position. So far, the authors proposed simple QZS mechanisms satisfying these two conditions by using constant‐force springs, which sustain constant load regardless of their elongation . Also, the authors developed a horizontal isolator with constant‐force springs, and by combining the vertical and horizontal isolators, a 2‐D (vertical and horizontal) isolator was proposed.…”

Self-locking degree-4 vertex origami structures

“…Lockinginduced stiffness jump can also be used as an embedded safety mechanism to prevent excessive deformations, which has many applications in robotic systems. Furthermore, structures with discrete stiffness jump display very rich nonlinear dynamic responses from harmonic excitations, so that self-locking origami can be developed into a foldable system with embedded vibration isolation or control functions [36,37]. Other than programmable deformation range and discrete stiffness jump, self-locking can enable other functionalities.…”

Integrated mechanical and material design of quasi-zero-stiffness vibration isolator with superelastic Cu–Al–Mn shape memory alloy bars

“…Araki et al [6,7] proposed simple QZS mechanisms having a large stroke length by applying constant-force springs, which sustain constant load regardless of their elongation. The loading capacity of a single constant-force spring is, however, limited to Submitted for possible publication in Journal of Sound and Vibration Araki Y, Kimura K, Asai T, Masui T, Omori T, Kainuma R: QZS vibration isolator with superelastic Cu-Al-Mn SMA bar the order of tens to hundreds newton while the size of a constant-force spring is relatively large.…”

“…It appears difficult to increase both the stroke length and the loading capacity because SMAs are used in the form of tube springs. Furthermore, the hysteresis of Ni-Ti superelastic SMAs is relatively large while such large hysteresis degrades the vibration isolation capability in vertical vibration isolation [6,7].…”