LQG/LTR control methodology in active structural control

This paper presents linear-quadratic-Gaussian synthesis with a loop-transfer-recovery (LQG/LTR) control method for civil engineering structures under seismic loads. A combination of collocated velocity feedback and the model-order reduction technique is found to lead to a simplified model of the structure; using a singular-value robustness criterion, the reduced model is proven to be satisfactory for the design of a LQG/LTR controller. The active structural controller design is then obtained through the following four steps: (1) Collocated velocity feedback to damp important structural modes; (2) model reduction of structures with collocated velocity feedback loop closed; (3) considerations of design specifications; and (4) LQG/LTR controller design. The four-step design procedure and the issue associated with the sensitivity of closed-loop stability are also discussed in this paper.