A novel quasi-zero-stiffness strut and its applications in six-degree-of-freedom vibration isolation platform

Design and experiment of a high-static-low-dynamic stiffness isolator using a negative stiffness magnetic spring

A torsion quasi-zero stiffness vibration isolator

Analytical study of a quasi-zero stiffness coupling using a torsion magnetic spring with negative stiffness

A quasi-zero stiffness (QZS) vibration isolator outperforms other passive control strategies in vibration attenuation especially in a low-frequency band, but it also has an intrinsic limitation of low roll-off rate in the effective frequency range of vibration isolation. To overcome this limitation, a two-stage QZS vibration isolation system (VIS) is proposed, in which the QZS feature is realized by combining a vertical liner spring with two parallel cam–roller–spring mechanisms. Considering a possible disengagement between the cam and the roller under large amplitude vibration, a piecewise nonlinear dynamical model is developed and approximately solved by the averaging method. The analytical solutions for amplitude–frequency relationship and force transmissibility are derived. The results reveal that the two-stage QZS VIS has both advantages of low-frequency vibration isolation and high roll-off rate. It is also found that the second resonance can be eliminated when heavy damping is present in the upper stage, and hence, a broader effective frequency range of isolation can be achieved. High intermediate mass and soft vertical springs in the lower stage are also found to result in high-quality isolation performance.

Force transmissibility of a two-stage vibration isolation system with quasi-zero stiffness

Design and experiment of a compact quasi-zero-stiffness isolator capable of a wide range of loads

A machine with an internal variable-stiffness mechanism can adapt its output force to the working environment. In the literature, linear variable-stiffness mechanisms (LVSMs) are rarer than those producing rotary motion. This paper presents the design of a class of novel LVSMs. The idea is to parallel connect two lateral curved beams with an axial spring. Through preload adjustment of the curved beams, the output force-todisplacement curves can exhibit different stiffness. The merit of the proposed LVSMs is that very large-stiffness variation can be achieved in a compact space. The stiffness can even be tuned to zero by assigning the appropriate stiffness to the axial spring. LVSMs with pinned curved beams and fixed curved beams are investigated. To achieve the largest stiffness variation with sufficient linearity, the effects of various parameters on the force curves are discussed. Techniques to scale an LVSM and change the equilibrium position are introduced to increase the usefulness of the proposed design. Finally, the LVSMs are experimentally verified through prototypes. [DOI: 10.1115/1.4028705]

Linear Variable-Stiffness Mechanisms Based on Preloaded Curved Beams

A machine with variable internal stiffness can meet the performance requirement in different working environments. Linear variable-stiffness mechanisms (LVSM) are rarely found compared with those producing rotary motion. This paper presents an approach to design a linear variable-stiffness mechanism. The idea is to parallel connect two lateral bistable beams with a vertical spring. Through the preload adjustment of the bistable beams, the output force to displacement curve can exhibit different stiffnesses. The merit of the proposed LVSM is that very large stiffness variation can be achieved in a compact space. The stiffness may even be tuned to zero by assigning a proper stiffness to the vertical spring. An optimization formulation is presented to design a LVSM with the largest stiffness variation. The effects of various parameters on the stiffness variation and linearity are discussed. The results are numerically verified with a prototype illustrated.

Yi Syuan Wu

Papers

Design and experiment of a compact quasi-zero-stiffness isolator capable of a wide range of loads

Linear Variable-Stiffness Mechanisms Based on Preloaded Curved Beams

Design of a linear variable-stiffness mechanism using preloaded bistable beams