An ultra-low frequency parallel connection nonlinear isolator for precision instruments

In order to improve the working performance of precision instruments, it is desirable to isolate ambience wideband vibrations. Nonlinear isolator is superior to linear isolator. In this paper, a novel combined positive and negative stiffness isolator is developed based on the analysis of the mechanism of negative stiffness, whose negative stiffness cancels much of the positive stiffness of the elastic element in the vicinity of the balance point. The stiffness at the balance point has a nonlinear characteristic and the net stiffness tends to be zero. This type of isolator has high support stiffness as well as low vibration stiffness. Its inherent frequency can be adjusted to zero by adjusting the initial deformation of the elastic elements of the negative stiffness mechanism. Experimental results show that the inherent frequency of the isolator can be adjusted from 10 Hz to 1 Hz. The isolation bandwidth of the isolator is widened and the performance of isolation is distinctly enhanced.