Rotor State Evaluation and Structural Health Monitoring Through Strain Sensors

This paper presents an original combined approach to shape-sensing and structural health monitoring of helicopter rotors. It is based on the measurement of strain in a limited number of points over the blade surface. The Shape-Sensing algorithm is modal-based and capable of reconstructing nonlinear, moderate lag, flap and torsion deflections. Two Structural Health Monitoring algorithms are presented, one in the time domain and the other in the frequency domain. Both are based on the analysis of the discrepancies between the strains arising in the damaged and the undamaged blades. Two damage types have been considered: a mass unbalance and a localized stiffness reduction. Both Shape Sensing and Structural Health Monitoring capabilities have been tested by numerical simulation using a multibody dynamic solver for general nonlinear comprehensive aeroelastic analysis.