This paper presents a study of a quasi-zero-stiffness (QZS) isolator. A unique relationship between the geometry configuration and the stiffness of the spring elements is obtained in order to design the property of high-static-low-dynamic stiffness. Analytical solutions of the nonlinear QZS system are derived with the harmonic balance method for the characteristic analysis of the force transmissibility and critical conditions for occurring jump-down and jump-up phenomena. The effects of damping and excitation force on the system behaviors are discussed. A series of experimental tests demonstrate that the QZS system greatly outperforms a corresponding linear isolation system. The former enables vibration to be attenuated at 0.5 Hz, while the latter can only execute attenuation after 4.2 Hz. The QZS system is especially effective for vibration isolation in the low-frequency range.

A platform supported by a hexapod of quasi-zero-stiffness (QZS) struts is proposed to provide a solution for low-frequency vibration isolation in six degrees-of-freedom (6DOFs). The QZS strut is developed by combining a pair of mutually repelling permanent magnets in parallel connection with a coil spring. Dynamic analysis of the 6DOFs QZS platform is carried out to obtain dynamic responses by using the harmonic balance method, and the vibration isolation performance in each DOF is evaluated in terms of force/moment transmissibility, which indicates that the QZS platform perform a good function of low-frequency vibration isolation within broad bandwidth, and has notable advantages over its linear counterpart in all 6DOFs.

This paper presents a study on a cost-effective engineering model that integrates an array of floating wave energy converters with a vast platform, a viable option for multi-functional performance in renewable energy capture and ocean space utilization. The wave energy converters are floating buoyance columns flexibly connected with the elastic platform. Hydrodynamic interactions among the columns are analyzed using an exact matrix transform method based on linear wave theory in the frequency domain. A parametric governing equation of compounded wave energy converter referred to as a wave farm is formulated by using Hamilton’s principle which can be discretized using the Galerkin method. The effects of wave conditions and the parameters of hydraulic power take-off (PTO) on the wave energy absorption and dynamic characteristics of the energy harvesting system are investigated. Furthermore, the wave energy capture on irregular waves is also discussed. This research work aims at providing a theoretical guidance for wave energy harvesting system design.