A new semi‐active control based on nonlinear inhomogeneous optimal control for mixed base isolation

Summary This paper presents a control algorithm for seismic mixed base isolation, combining passive isolators and semi‐active viscous dampers. The objective is to limit base displacement while avoiding undesirable amplification of the response of the non‐isolated modes. To this end, the proposed algorithm takes into account the constraints on the damping coefficient of the semi‐active damper and information on the excitation. It is based on the approximate iterative solution, at each control time step, of a nonlinear inhomogeneous constrained optimal control problem. An autoregressive model is used to obtain, at each control time step, a prediction of the upcoming excitation in a short time interval ahead. Numerical simulation results demonstrate the efficacy of the above method, especially in improving floor response spectra, and its superiority with respect to clipped‐optimal algorithms.