Multi-model robust adaptive control of tall buildings

Model reference adaptive control (MRAC) strategies are gaining an increasing interest by researchers working in the area of structural control mainly for their capacity of compensating for large uncertainties, faults and time varying disturbances in linear and nonlinear plants. In this paper a modification of the standard MRAC algorithm is proposed which adopts multiple reference models (M-MRAC). The motivation of the proposed scheme is that flexible buildings subjected to multiple hazards, like wind and earthquake, require different damping levels to avoid the occurrence of different limit states. A M-MRAC scheme that uses two reference models is adopted. The first reference model, with small structural damping, is active in the presence of low level excitation like moderate wind loading, while the second reference model, with a higher damping, is activated when a suitable response-dependent signal exceeds a defined threshold in the presence of severe seismic loading. Analyses on a tall building subjected to wind and earthquake show the capacity of the M-MRAC in tracking the reference system and in mitigating the structural response. Comparison with traditional MRAC highlights that the main advantage of M-MRAC is the reduction of the control force, at the expense of a slight reduction of control effectiveness.