Vibration signal predictions of damaged sensors on rotor blades based on operational modal analysis and virtual sensing

Rotor blade is one of the most significant components of helicopters. But due to its high-speed rotation characteristics, it is difficult to collect the vibration signals during the flight stage. Moreover, sensors are highly susceptible to damage resulting in the failure of the measurement. In order to make signal predictions for the damaged sensors, an operational modal analysis (OMA) together with the virtual sensing (VS) technology is proposed in this paper. This paper discusses two situations, i.e., mode shapes measured by all sensors (both normal and damaged) can be obtained using OMA, and mode shapes measured by some sensors (only including normal) can be obtained using OMA. For the second situation, it is necessary to use finite element (FE) analysis to supplement the missing mode shapes of damaged sensor. In order to improve the correlation between the FE model and the real structure, the FE mode shapes are corrected using the local correspondence (LC) principle and mode shapes measured by some sensors (only including normal). Then, based on the VS technology, the vibration signals of the damaged sensors during the flight stage can be accurately predicted using the identified mode shapes (obtained based on OMA and FE analysis) and the normal sensors signals. Given the high degrees of freedom (DOFs) in the FE mode shapes, this approach can also be used to predict vibration data at locations without sensors. The effectiveness and robustness of the proposed method is verified through finite element simulation, experiment as well as the actual flight test. The present work can be further used in the fault diagnosis and damage identification for rotor blade of helicopters.