Smart Passive Vibration Isolation: Requirements and Unsolved Problems

Abstract

Vibration isolators are needed to control the relative displacement, acceleration, or most importantly the transmitted force to the base or to the isolated device. As a general rule, a good vibration isolator should be as soft as possible to reduce the transmitted force, and it should be hard to limit the relative displacement. Soft suspension provides large relative displacement in resonance zone. To limit the relative displacement while having a soft suspension, a limiting displacement design is needed. There are two practical designs, Hydraulic Engine Mount (HEM) and Piecewise Linear Suspension (PLS) which are being used in industry since 80s. Hydraulic engine mounts were invented to passively produce a low damping at low amplitude and a high damping at high amplitude. Similarly, piecewise linear suspension were introduced to provide a soft suspension at low amplitude and a hard suspension at high amplitude. Having dual behavior puts both HEM and PLS in the domain of nonlinear system which in turn brings many new phenomena never appeared in linear analysis. This article will review the necessity of having a dual behavior suspension and the design of the two practical designs. However, both of these designs have some challenging and unsolved problems. Introducing the problems opens avenue for supervisors, researchers, and students to direct their research practice and hopefully solve them.