Structural Damage Detection Using Virtual Passive Controllers

Novel approaches are presented for structural damagedetection that use virtual passive controllers attached to structures, where passive controllers are energy dissipative devices and, thus, guarantee closed-loop stability. The use of the identiŽ ed parameters of various closed-loop systems can solve the problem that the reliable identiŽ ed parameters, such as natural frequencies, of the open-loop systemmay not provide enough information for damage detection. Only a small number of sensors are required for the proposed approaches. The identiŽ ed natural frequencies, which are generally much less sensitive to noise and more reliable than the identiŽ ed mode shapes, are used for damage detection. Two damagedetection techniques are presented. One technique is based on structures with direct output feedback controllers, whereas the other technique uses second-order dynamic feedback controllers. A least-squares technique, which is based on the sensitivity of natural frequencies to damage variables, is used for accurately identifying the damage variables.