Early Crack Localization in Flexible Structures Subjected to Unknown Disturbances Using Sensor-Measurements Only

This paper uses output-only measurements to localize faults within flexible structures. These measurements are used to construct transmissibility operators, which are mathematical models that are independent of the excitation acting on the structure. Faults considered in this paper are formulated as unknown disturbances acting on the underlying structure. The proposed approach is illustrated on a class of flexible cantilever beams, which can be modeled as a connection of finite lumped segments. The output (e.g. deflection of the beam) at one location on the beam can be predicted using a transmissibility operator and the output at a different location on the beam. The discrepancy between the measured and predicted outputs at a specific location on the beam can be used as a fault indicator. If this discrepancy is small, the beam is considered healthy. Any deviation from the healthy conditions of the beam will cause an increase in the transmissibility discrepancy, which indicates a fault. This allows early fault and crack detection even if the fault is not clearly visible to the human eye. The proposed approach can be used online during system operation and is illustrated using a numerical example.