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Articles 1 - 4 of 4
Full-Text Articles in Military Vehicles
Active Control Of Coherent Structures In An Axisymmetric Jet, Michael Marques Goncalves
Active Control Of Coherent Structures In An Axisymmetric Jet, Michael Marques Goncalves
Doctoral Dissertations and Master's Theses
The primary objective of this work is to develop high-fidelity simulation model for jet noise control predictions and quantify the sound reduction when an external source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce low-frequency noise in jet engines, such approaches incur a performance penalty since they result in a reduced thrust. To avoid a performance penalty in reducing jet noise, the current work investigates a open-loop active noise control (ANC) system that utilizes a unsteady microjet actuator on the nozzle lip in the downstream …
Nonlinear Least Squares 3-D Geolocation Solutions Using Time Differences Of Arrival, Michael V. Bredemann
Nonlinear Least Squares 3-D Geolocation Solutions Using Time Differences Of Arrival, Michael V. Bredemann
Mathematics & Statistics ETDs
This thesis uses a geometric approach to derive and solve nonlinear least squares minimization problems to geolocate a signal source in three dimensions using time differences of arrival at multiple sensor locations. There is no restriction on the maximum number of sensors used. Residual errors reach the numerical limits of machine precision. Symmetric sensor orientations are found that prevent closed form solutions of source locations lying within the null space. Maximum uncertainties in relative sensor positions and time difference of arrivals, required to locate a source within a maximum specified error, are found from these results. Examples illustrate potential requirements …
Variable Structure Observer For Control Bias On Unmanned Air Vehicles, Nathan Slegers, Mark Costello
Variable Structure Observer For Control Bias On Unmanned Air Vehicles, Nathan Slegers, Mark Costello
Faculty Publications - Biomedical, Mechanical, and Civil Engineering
No abstract provided.
Nonlinear Model Predictive Control Technique For Unmanned Air Vehicles, Nathan Slegers, Jason Kyle, Mark Costello
Nonlinear Model Predictive Control Technique For Unmanned Air Vehicles, Nathan Slegers, Jason Kyle, Mark Costello
Faculty Publications - Biomedical, Mechanical, and Civil Engineering
A nonlinear model predictive control strategy is developed and subsequently specialized to autonomous aircraft that can be adequately modeled with a rigid 6-degrees-of-freedom representation. Whereas the general air vehicle dynamic equations are nonlinear and nonaffine in control, a closed-form solution for the optimal control input is enabled by expanding both the output and control in a truncated Taylor series. The closed-form solution for control is relatively simple to calculate and well suited to the real time embedded computing environment. An interesting feature of this control law is that the number of Taylor series expansion terms can be used to indirectly …