Semiactive vibration suppression by variable-damping members

A semiactive vibration suppression approach Is proposed and investigated. It is to control the damping of viscous dampers installed in structures. By using a single-degree-of-freedom (SDOF) example first, vibration damping is shown to be much enhanced by a suitable variation of the damping of the damper according to the phase of vibration. Next, several types of control logic for this approach are proposed, which are applicable to multiple-degree-of-freedom (MDOF) structures with multiple variable dampers. The performance of these types of control logic are investigated by using an SDOF example and an MDOF truss structure example with three variable damping truss members excited by impulsive and random forces. Numerical investigations demonstrate that the vibration suppression capabilities of most of them are much higher than that of the optimally tuned passive system, keeping the robustness of passive systems.