A spatially mechanical-decoupled three-DOF quasi-zero-stiffness isolator integrating flexible curved beams

The low-frequency vibration problem in land, maritime, and aerial transportation may affect the performance of precision instruments. Existing studies lack solutions for multidirectionally coupled vibrations. This research proposes a spatially decoupled three-DOF quasi-zero-stiffness vibration isolator (3DQVI), which integrates displacement-constraint double-sine flexible beams (DSFB) to achieve quasi-zero stiffness (QZS) in all three directions. The isolator further decouples displacement by incorporating linear rails, offering a compact structure with strong decoupling capabilities and excellent performance in multi-directional isolation. In this work, a dynamic equation considering Coulomb damping is established, and an analytical solution is derived using the harmonic balance method (HBM). The phase trajectory under spatially coupled vibrations is analyzed, showing that the 3DQVI exhibits differential periodic or chaotic motion in each direction. A series of experiments with single-direction and multi-direction excitations reveal the displacement transmissibility (T_d), as well as the root mean square (RMS) amplitude of the non-primary direction response. Results indicate the 3DQVI isolates vibrations above 6 Hz in any direction, with 90% isolation at 15 Hz, and the non-primary responses generated do not exceed 8% per millimeter. The 3DQVI demonstrates excellent low-frequency isolation performance and displacement decoupling capabilities. To simulate actual conditions, the 3DQVI is mounted on an electric vehicle for road isolation experiments. The results show a significant isolation effect, which demonstrates the practical value of 3DQVI in multi-directional isolation applications. 3DQVI provides a reference for the integrated design of multi-directional isolators and spatial vibration analysis, and great potential in engineering applications.