Determination Of Rotor Blade Loads Based On Optical Fiber Sensors Measurement

Determination of rotor blade loads is a challenging topic in the field of rotorcraft aerodynamics and dynamics. In this thesis, the rotor blade strain was measured using the fiber grating, then the distributed blade displacements and loads was determined from the fiber optical sensor strain-gauging outputs. The approach was based on the fact that the fiber grating measurement was a more perfect method than else sensing. The technology had tremendous application potential.Both the Bragg effective refractive index and the grating pitch varied with changes in a force field imposed on the fiber. The strain that the optical fiber sensor received would shift the Bragg wave length. And therefore the measured parameters could be determined by the change of the Bragg wave length. Fiber Bragg grating sensors was offering a viable alternative sensing approach with some advantages including immunity to noise, light weight, small size, and corrosion resistance and multiplexing capabilities. These effects provided a means for measuring the distributed rotor blade strain.In this thesis, the method for determining the distributed rotor blade loads from the fiber optical sensor measuring strains of the blade had been developed. The measured section displacement, internal forces and external loads could be determined from the blade strain. And the vibration measurement method of fiber grating was applied to measure the distributed rotor blade strain during helicopter's hovering flight. Based on the above analysis, the displacement, internal forces and external loads distribution along the blade were determined.