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Abstract: A robust feature extraction scheme for the rolling element bearing (REB) fault diagnosis is proposed by combining the envelope extraction and the independent component analysis (ICA). In the present approach, the envelope extraction is not only utilized to obtain the impulsive component corresponding to the faults from the REB, but also to reduce the dimension of vibration sources included in the sensor-picked signals. Consequently, the difficulty for applying the ICA algorithm under the conditions that the sensor number is limited and the source number is unknown can be successfully eliminated. Then, the ICA algorithm is employed to separate the envelopes according to the independence of vibration sources. Finally, the vibration features related to the REB faults can be separated from disturbances and clearly exposed by the envelope spectrum. Simulations and experimental tests are conducted to validate the proposed method. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]