An innovative lever-based isolator with quasi-zero stiffness properties for applications in mechanical control systems

The use of lever-type stiffness mechanism (LSM) in vibration isolation practice is minimal. Accordingly, the quasi-zero lever-type stiffness isolator (QZLSI) is proposed in this paper. The novelty of the proposed LSM is designed by connecting two identical stiffness springs by a pivoting lever to change the negative stiffness properties of the QZLSI. Thus, the quasi-zero lever-type stiffness condition is established, and the results analysis showed that increasing the lever ratio can reduce the stiffness of the QZLSI and expand the negative stiffness range, which increase the bearing capacity of the QZLSI. To illustrate this advantage, the QZLSI is used as vibrations isolation system of typical simply supported beam structure. The dynamic equation is established, and the analytical displacement response of the isolated beam is determined using the harmonic balance method. Then, the force transmissibility response is deduced. The response analysis showed that a smaller lever ratio is beneficial to reduce the peak force transmissibility in the resonant region and extend the isolation frequencies band. Therefore, the isolation performance comparison of the proposed QZLSI with respect to its classical counterpart QZSI when the excitation force amplitude ratio varies between 0.001 and 0.1 demonstrates that the QZLSI can reduce the peak force transmissibility from 66.22 to 17.94% and expand the isolated frequency band from 73.31 to 49.9%. These results are relevant to show the interest of the proposed isolation system in engineering practice.