Analysis and optimization of a quasi-zero-stiffness vibration isolator based on partially rigidized compliant mechanisms

Vibration isolators with quasi-zero-stiffness (QZS) are effective for broadband vibration isolations. To meet engineering requirements, a large-stroke QZS should be exhibited at a specific absolute displacement range for a pre-determined payload, and thus a strong design flexibility is necessary. To address the issue, a vibration isolator based on partially rigidized compliant mechanisms is proposed. The compliant beams provide the structural nonlinearity, the storage/release of the energy and the adjustment ability of the nonlinear stiffness, while the rigid beams guarantee the load capacity. The nonlinear restoring force of the isolator is modeled based on a chained beam constraint model, characterizing the coupling effect between the rigid and compliant beams. The dynamic responses are analyzed using the harmonic balance method. An optimization method is proposed to obtain the desired QZS at targeted force/displacement region. Numerical simulations reveal that the nonlinear stiffness characteristics of the proposed structure can be adjusted by both topological dimensions and the ratio between rigid and compliant beams. The optimization method applies to different payload masses to achieve the optimal QZS at the specific absolute displacement range. The proposed isolator exhibits better design flexibility than the isolator with hinges and springs and a stronger load capacity than the isolator with compliant mechanisms. Static and dynamic experiments are conducted to validate the accuracies of the theoretical methods and the isolation performance of the proposed isolator.