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Dissertation Defense
Estimation of Helicopter Rotor Loads from Blade Structural Response
Daiju Uehara
PhD Candidate
Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin
Friday, November 8, 2019, 2:30 pm
ASE 2.202

Measuring helicopter rotor loads has been one of the most challenging tasks in experimental rotorcraft research. Conventional loads measurements with on-blade instrumentation, such as pressure transducers and strain gages, require the experimentalist to overcome a large number of technical barriers; for example, sensor integration, sensor failure due to centrifugal forces, and influence of sensor installation on rotor blade dynamics. The goal of this dissertation is to develop a new experimental and theoretical methodology to obtain helicopter rotor loads without using conventional on-blade sensors.

The rotor load estimation methodology begins with the blade structural deformation measurements using non-contact, optical, time-resolved Digital Image Correlation (DIC). The rotating-frame modal properties (natural frequencies, mode shapes, and damping ratios) of the blade are then extracted from the deformation time history using Natural Excitation Technique - Eigensystem Realization Algorithm (NExT-ERA) and Complexity Pursuit (CP), which are operational modal analysis (OMA) algorithms. Rotor loads are finally estimated based on the measured deformations and blade modal characteristics. Having validated the present approach incrementally with measurements performed on rotors at different scales, configurations, and operating conditions, this study estimated the spanwise lift distribution and integrated thrust at the hub for a 2 m-diameter, two-bladed single rotor in hover. The estimated thrust at the rotor hub correlated within 5% of the measured value for all the operating conditions.

Contact  Dr. Jayant Sirohi (512) 471-4186 or jayant.sirohi@mail.utexas.edu

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