Design of a new quasi-zero-stiffness isolator system with nonlinear positive stiffness configuration and its novel features

A quasi-zero-stiffness (QZS) isolator with the new design of positive stiffness configuration is proposed in this paper. The positive stiffness configuration, composed of a pair of torsion springs, oblique bars and linear bearings, exhibits beneficial nonlinearity. In parallel with the negative stiffness provided by the oblique bars connected to linear springs in the direction perpendicular to motion, it can expand the effective displacement range of QZS. In the static analysis, the force and stiffness of the system are derived. A nonlinear optimization is also conducted to determine the structural parameters. The dynamic characteristics are then analyzed through the Lagrange’s equation and averaging method. The displacement transmissibility is investigated through a numerical simulation. The results indicate a much better vibration isolation performance of the present design than that of the previous QZS isolator with the linear positive stiffness element.