RESPONSE CONTROL PERFORMANCE OF SEMI-ACTIVE ISOLATION SYSTEM USING THE GS CONTROLE FOR A TWO-DEGREE-OF-FREEDOM STRUCTURE WITH MAGNETO-RHEOLOGICAL FLUID DAMPER

Many studies to apply a magneto-rheological fluid (MR) damper as a variable damping device are carried out actively, In this paper we verify availability of semi-active vibration isolation using a large-size MR damper for a two-degree-of-freedom structure. Since the passive system is tuned to have specified dynamic property, there are some uncertainties about response under future large earthquakes. To avoid this problem, we take semi-active control and use an MR damper, which can produce appropriate damping forces by controlling magnetic field via input current. We apply the gain-scheduled (GS) control method to meet multiple objectives, i) suppressing responses of isolation layer, ii) without deterioration of acceleration of upper structure and iii) with only one damper. To apply the GS control method, based on Linear Matrix Inequalities (LMI), the system with the semi-active MR damper should be transformed to a linear parameter-varying model. For verification of the control performance we carry out simulations and experiments for some kind of earthquakes using the 40 kN-class MR damper. Finally, in comparison with the skyhook damping control or a passive damper it is verified that the proposed method has good performance.