Design and characterization of a compact tripod quasi-zero-stiffness device for isolating low-frequency vibrations

This paper presents a compact tripod quasi-zero stiffness (QZS) device for low-frequency vibration isolation with an envelope of 240 × 240 × 130 mm³ based on a compliant constant-force mechanism (CCFM). Theoretical analyses and experiments have been performed to show that the QZS device can effectively suppress vibration above 9 Hz with a 6 kg load. Specifically, the CCFM is achieved by combining a positive-stiffness diamond-shape mechanism and a bi-stable beam of negative-stiffness characteristics. A static parametric model of the CCFM was derived based on the pseudo-rigid body method and virtual work principle to identify the optimal design parameters. We next developed the dynamic model based on Lagrange equations and the harmonic balance method. The dynamic responses with respect to excitation amplitude is investigated, and the effect of excitation amplitude and damping on displacement transmissibility is discussed with numerical simulation. Finally, static, and dynamic experiments were performed to verify the accuracy of parametric model. The compact tripod QZS isolator presents a new and effective solution for isolating low-frequency vibrations in precision apparatus.