Adaptive backstepping control of hysteretic base-isolated structures

The paper considers a hybrid seismic control system for building structures, which combines a class of passive nonlinear base isolator with an active control system. The objective of the active component is to keep the base displacement relative to the ground, the interstory drift and the absolute acceleration within appropriate ranges. The base isolator device exhibits a hysteretic nonlinear behavior which is described by the Bouc-Wen model. The adaptive backstepping approach is used for the control design in order to cope with the nonlinearity and the presence of uncertainties. The control problem is formulated with representations of the system dynamics using two alternative coordinate sets: absolute (with respect to an inertial frame) and relative to the ground. A comparison between the two strategies is presented by means of numerical simulations.