A two-step identification technique for semiactive control systems

Semiactive control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sources. Because semiactive devices are intrinsically nonlinear, developing an analytical model of the structural system that can portray its dynamic behavior is important, especially in the controller design phase. This paper discusses a novel, two-step system identification approach that does not require the semiactive device to be tested apart from the structure, but rather mounted into it, which can save substantial costs. To verify the efficiency of the approach, a base-isolated, two-degrees-of-freedom building model mounted on laminated rubber bearings and supplemented with an MR damper at the base is considered. The MR damper employed has a simple construction: absorbent foam saturated with MR fluid. An analytical model for the MR damper that employs the Bouc-Wen hysteresis model is developed. Optimal system parameters are identified applying a multi-input/multi-output parametric identification method based on the Nelder-Mead simplex algorithm. Comparison with experimental data shows that the identified analytical model is accurate over a wide range of operating conditions, confirming that the proposed approach is adequate for control design and analysis.