Control of base-isolated systems using force feedback

The combination of passive and active schemes has been increasingly considered in the structural control community as a promising way to design efficient smart hybrid base isolation systems for seismic protection. This paper considers a hybrid system in which an active feedback control law is derived to be applied in parallel with a passive isolation device. The active control uses the restoring force supplied by the passive isolator as the main feedback signal. This paper can be divided in two main parts: in the first one, the paper presents the theoretical formulation and stability analysis in the active control strategy; in the second part, a set of numerical simulations is performed when the force is supplied in a semi active way to validate and discuss the efficiency of the approach in a more realistic scenario. Moreover, the performance of the proposed semi-active control algorithm is compared with passive-off, passive-on and clipped-optimal controllers. The proposed control scheme reduces the base displacement without increasing the floor accelerations.