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Full-Text Articles in Applied Mechanics
Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles
Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles
Mechanical & Aerospace Engineering Theses & Dissertations
The aim of this thesis is to explore methods to reduce the noise impact of unmanned aerial vehicles operating within acoustically sensitive environments by flight control system augmentation. Two methods are investigated and include: (i) reduction of sound generated by vehicle speed control while flying along a nominal path and (ii) reduction of acoustic exposure by vehicle path control while flying at a nominal speed. Both methods require incorporation of an acoustic model into the flight control system as an additional control objective and an acoustic metric to characterize primary noise sources dependent on vehicle state. An acoustic model was …
Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos
Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos
Mechanical & Aerospace Engineering Theses & Dissertations
A numerical integration technique, a modified version of the Newmark method, is applied to transient motion problems of systems with mass, stiffness, and small nonlinear damping. The nonlinearity is cast as a pseudo-force to avoid repeated recalculation and decomposition of the effective stiffness matrix; thus, the solution technique is dubbed the "pseudo-force Newmark method." Comparisons with exact and perturbation solutions in single-degree-of-freedom problems and with a Gear-method numerical solution in a cantilevered Timoshenko beam finite element problem show the solution technique to be efficient, accurate, and, thus, feasible provided the nonlinear damping is small. As a preliminary step into the …