Robust fault detection in hysteretic base-isolation systems

This paper proposes a fault detection method for hysteretic base-isolation systems. One major difficulty in the context of fault detection is to obtain a scheme that is robust with respect to disturbances (in this case, the seismic excitation) that are not faults. One of the key contribution of this paper is a Lyapunov-based disturbance (seismic) observer that leads to the design of a robust fault detection scheme. The basic idea behind the use of observers for fault detection is to estimate the outputs of the system from the measurements by using some type of observer, and then construct the residual by a properly weighted output estimate error. The residual is then examined for the likelihood of faults by using a threshold. Certain decision rules can then be applied to determine if a fault has occurred. The different fault types considered in this paper are stiffness and damping variations in the system. A design procedure is described, and nonlinear simulation results are presented to demonstrate the applicability of the proposed method. The obtained numerical results suggest that the proposed fault estimation method provides an estimate of the size and severity of the fault, which can be important in many civil engineering applications.