Coupled nonlinear vibration characteristics of quasi-zero-stiffness Gough-Stewart isolation platform

The quasi-zero-stiffness (QZS) Gough-Stewart vibration isolation platform is designed for six degrees-of-freedom (DOFs) low-frequency vibration isolation. Lots of studies regarding the amplitude-frequency relationship of the platform are based on the assumption that interference with the platform in one direction only provokes a response in that direction. This assumption artificially decouples a six DOFs coupling model into six single DOF equations, ignoring the coupling relationship between each DOFs, making the analysis results inaccurate. Therefore, without simplifying the nonlinear terms and taking the coupling effect into consideration, the improved Incremental Harmonic Balance Method (IHBM) is employed to discuss the coupling relationship between different DOFs of the QZS Gough-Stewart vibration isolation platform. The results show that the platform has multiple equilibrium positions. When the platform is excited from different directions, it will vibrate at different equilibrium positions, and the closer these positions are to the zero-stiffness position, the more likely the system is to exhibit jump phenomenon and sudden increases in response. The platform exhibits a single-directional response only when excited from the..-direction. Through comparative study, it is found that the cubic configuration can weaken the coupling effect between each DOFs compared with the general configuration.