On the isolation properties of semiactive dampers

The primary purpose of this study is to evaluate and better understand the isolation properties of semiactive suspensions. Specifically, this study wi ll answer the question regarding why semiactive dampers are able to isolate at frequencies well below; those for passive dampers, even though they do not add any energy to the system. A single suspension model is used to deri ve and analytically evaluate the transmissibility properties of passive and semiactive dampers. The results show that for semiactive dampers, the freq uency range of isolation and the transmissibility amplitude are functions o f xi, the damping ratio. In contrast, the isolation frequency range for pas sive dampers is completely independent of xi. Furthermore, the results show that for sufficiently large xi, semiactive dampers are able to provide iso lation at all frequencies. This feature is useful for many applications, pa rticularly for sensitive machinery that cannot tolerate any overshoot in po wer-up or power-down, and yet must have good isolation during normal operat ion. Passive suspensions offer only one of the two aspects, whereas semiact ive suspensions offer both.