Active damping system with respect to quasi-fixed reference

A vertical quasi-fixed reference system is constructed using a torsion spring, and the vertical normal mode of a single-stage isolator is successively damped with respect to the quasi-fixed reference system. The experimental result shows that the vertical normal mode was damped from 3×10−8/\(\sqrt {Hz} \) down to 2×10−9/\(\sqrt {Hz} \) without reintroducing the high frequency ground vibration. This agrees well with the theoretical analyses.