A novel quasi-zero stiffness isolation platform for enhancing the effective operating range via a quasi-linear stiffness compensation mechanism

Quasi-zero stiffness (QZS) isolators have been widely applied in various engineering fields for low-frequency vibration suppression due to their characteristic combination of high-static and low-dynamic stiffness (HSLDS). However, most QZS isolators exhibit these properties only in the vicinity of the equilibrium position, which significantly limits their effective operating range. This study proposes a QZS isolation platform based on a quasi-linear stiffness compensation mechanism to extend its effective operating range. The negative stiffness produced by the two types of rhombic structures exhibits different variation trends. With suitable parameter combinations, effective quasi-linear negative stiffness can be realized and combined with linear positive stiffness to construct an isolator featuring a wide QZS range. The modified incremental harmonic balance method is employed to conduct a detailed and accurate analysis of the dynamic characteristics under varying base excitation amplitudes and damping parameters. The transmissibility characteristics under different mass loads indicate that effective vibration isolation can still be maintained even when the load is not located at the zero-stiffness position. Comparison with a linear isolator and a typical X-shaped isolator demonstrates that the proposed isolation structure exhibits a wider QZS range and superior vibration isolation performance. Static and dynamic tests are conducted based on the fabricated prototype, and the accuracy and effectiveness of the theoretical model are validated through experimental testing. The quasi-linear stiffness compensation mechanism provides an effective approach to broaden the working range of isolators. The proposed isolator exhibits QZS characteristics over most of its total stroke, enabling practical realization of low-frequency vibration isolation requirements in engineering applications.