Design, analysis and semi-active control of a quasi-zero stiffness vibration isolation system with six oblique springs

Vibration isolation systems with quasi-zero stiffness (QZS) performance have been widely studied because of their characteristics: high static stiffness and low dynamic stiffness. However, the effective displacement range of QZS is usually so small that strongly limits its application existing in real engineering. Thus, this study' main innovation is to attempt to expand the effective displacement range of the QZS system via a semi-active control strategy. We first present a novel quasi-zero stiffness (QZS) vibration isolation system. The QZS characteristic is achieved by combining a mechanism with six oblique springs and a coil spring, which provide negative stiffness and positive stiffness, respectively. The effects of inclination angles of oblique springs on the negative stiffness of the system are first discussed via the static analysis method. The dynamic characteristics under simple harmonic excitation are then analyzed using the harmonic balance method, including the jumping phenomena and force-displacement transmissibility. To further enlarge the effective displacement range of QZS, a feedback displacement strategy is utilized to actively adjust the inclination angles of oblique springs and realize the alteration of the stiffness of the QZS system. Results obtained from theoretical analysis show that, in the aspect of low-frequency vibration isolation performance, different from linear systems, the proposed QZS system has obvious advantages, and the displacement range of quasi-zero stiffness property is significantly expanded from a single equilibrium point to a relatively lager range when the semi-active control strategy is implemented. Furthermore, the virtual prototype simulation results reveal that the proposed QZS system can maintain excellent vibration isolation performance under significant amplitude vibration after adding control.

Automated summary

This study aims to expand the effective displacement range of quasi-zero stiffness systems through a semi-active control strategy. A novel vibration isolation system based on oblique springs and a coil spring is proposed, along with a feedback displacement strategy for stiffness adjustment. Theoretical analysis and virtual prototype simulation results show significant advantages in low-frequency vibration isolation performance for the proposed system.