Force transmissibility of a 6-DOF passive quasi-zero stiffness vibration isolation platform

A compression bar-type quasi-zero stiffness (QZS) element is designed on the basis of the parallel principle of positive and negative stiffness by combining disc spring and coil spring. A vibration isolation platform supported by the compression bar type QZS element is constructed. First, the static analyses of the compression bar-type QZS element and QZS vibration isolation platform are investigated, and the force-displacement equations of each degree of freedom (DOF) of the QZS platform are derived. Second, the force transmissibility and dynamic characteristics under harmonic excitation are analyzed in detail and made a comparison with those of the equivalent linear isolation system. Results show that the vibration isolation performance (VIP) of the QZS isolation system is superior to that of the equivalent linear isolation system. The low-frequency VIP of the QZS system can be enhanced by increasing damping, reducing the stiffness ratio, or changing installation angle.