| Title |
Vibration Control of a Base-Isolation System Subjected to Seismic Excitation with Loop Transfer Recovery Method |
| Keywords |
Optimal Control ; LQG/LTR Control ; Robust Stability ; Earthquake Engineering |
| Abstract |
Control of the vibrations induced from the earthquake can be accomplished for the multiple story buildings using various optimal control methods. Linear Quadratic(LQ) control method may be feasible provided all state variables of the system can be measured, which is not always possible and practical. However, it has attractive features of infinite gain margin and phase margin greater than 60 degrees. The gain margin and phase margin indicate how robustly stable the closed loop system behaves with uncertainties such as system noise and modeling errors. State feedback control system can be implemented with the only measurable states if constructed in Linear Quadratic Gaussian(LQG) algorithm. It requires an observer to estimate the state variables based on the measured one, but loses the entire gain margin due to the Kalman filter adapted in the algorithm. The H-infinity control may overcome the shortcomings of the LQG with emphasized robustness features against perturbations and uncertainties, but it usually ends up with rather complicated control system to implement. LQG with loop transfer recovery(LQG/LTR) method is applied in this study to retain the moderate level of stability robustness while keeping the observer alive for a base-isolation system. The results showed that the LQG/LTR control system reduced the relative displacement in the base isolated floor as effectively as the LQG control system with a moderate level of the gain margin recovered. |