Development of a Variable Stiffness and Damping Tunable Vibration Isolator

In this paper we report on the development of a variable stiffness and damping Liquid Inertia Vibration Eliminator (LIVE) vibration isolator. The result is the ability to shift the isolation frequency of the isolator and also to change the amplification at resonance. A practical variable stiffness spring was developed by using a compound leaf spring with circular spring elements. A wax actuator, controlled by a hot-air gun with a closed-loop displacement and velocity feedback control system, was used to separate the springs at the center. An experimental isolator was constructed and tested. The isolation frequency was shifted from 22.8 to 36.2 Hz by changing the stiffness of the spring by 270%. A transmissibility of less than 10% was achieved over the whole range. The viscous damping ratio was changed from 0.001 to 0.033 by increasing the flow losses in the system.