Semi-active vibration control of multiple degree-of-freedom systems using magneto-rheological fluid

Abstract

As the need for reduced noise and vibration increases, the suspension systems of machines and structures are becoming even more complex and more important than ever. Many researches on the suspensions, especially mounts, are actively conducted to improve the vibration isolation performance. Mounts support the static weight of a mechanical structure and isolate the vibration from the structure in order to minimize the force transmitted to the support. But in order to execute such two roles all together, stiffness of the mount must satisfy conflicting design conditions: Theoretically, to support the static weight of an structure, the dynamics stiffness of the structure must be hard. On the other hand, to minimize a force transmitted from the structure to the support, the dynamic stiffness must be soft. So, it is clear that passive mounts, which are still in wide usage, often fail in meeting such stringent requirement. Although passive mounts, especially hydraulic mounts, have been developed for many years to meet such conflicting requirements, they cannot fundamentally change their stiffness freely according to situations and have complex mechanisms that cause difficulties in design and manufacture. To overcome such fundamental restrictions of passive mounts, fully active mounts, which measure the force or vibration transmitted from a structure to a support and suppress it utilizing forces from actuators, are introduced. They are more effective than passive ones, because they can fundamentally change their stiffness freely according to situations. However the active mount is often costly because of sensors and actuators. It is susceptible to the so-called spillover problem, which causes damage to stability of the suspension system. Thus, as an alternative to fully active mounts, vibration control with semi-active actions has been of popular interest in recent years, because semi-active mounts can change their stiffness properly according to situations. Among othe...