Research and Publications - Department of Aerospace Engineering and Mechanics

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    LPV modeling of a flexible wing aircraft using modal alignment and adaptive gridding methods
    (Elsevier, 2017) Al-Jiboory, Ali Khudhair; Zhu, Guoming; Swei, Sean Shan-Min; Su, Weihua; Nguyen, Nhan T.; Michigan State University; University of Diyala; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; University of Alabama Tuscaloosa
    One of the earliest approaches in gain-scheduling control is the gridding based approach, in which a set of local linear time-invariant models are obtained at various gridded points corresponding to the varying parameters within the flight envelop. In order to ensure smooth and effective Linear Parameter Varying control, aligning all the flexible modes within each local model and maintaining small number of representative local models over the gridded parameter space are crucial. In addition, since the flexible structural models tend to have large dimensions, a tractable model reduction process is necessary. In this paper, the notion of sigma-shifted H-2- and H-infinity-norm are introduced and used as a metric to measure the model mismatch. A new modal alignment algorithm is developed which utilizes the defined metric for aligning all the local models over the entire gridded parameter space. Furthermore, an Adaptive Grid Step Size Determination algorithm is developed to minimize the number of local models required to represent the gridded parameter space. For model reduction, we propose to utilize the concept of Composite Modal Cost Analysis, through which the collective contribution of each flexible mode is computed and ranked. Therefore, a reduced-order model is constructed by retaining only those modes with significant contribution. The NASA Generic Transport Model operating at various flight speeds is studied for verification purpose, and the analysis and simulation results demonstrate the effectiveness of the proposed modeling approach. (C) 2017 Elsevier Masson SAS. All rights reserved.
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    Optimum Wing Shape of Highly Flexible Morphing Aircraft for Improved Flight Performance
    (American Institute of Aeronautics and Astronautics, 2016) Su, Weihua; Swei, Sean Shan-Min; Zhu, Guoming G.; University of Alabama Tuscaloosa; National Aeronautics & Space Administration (NASA); NASA Ames Research Center; Michigan State University
    In this paper, optimum wing bending and torsion deformations are explored for a mission adaptive, highly flexible morphing aircraft. The complete highly flexible aircraft is modeled using a strain-based geometrically nonlinear beam formulation, coupled with unsteady aerodynamics and six-degree-of-freedom rigid-body motions. Since there are no conventional discrete control surfaces for trimming the flexible aircraft, the design space for searching the optimum wing geometries is enlarged. To achieve high-performance flight, the wing geometry is best tailored according to the specific flight mission needs. In this study, the steady level flight and the coordinated turn flight are considered, and the optimum wing deformations with the minimum drag at these flight conditions are searched by using a modal-based optimization procedure, subject to the trim and other constraints. The numerical study verifies the feasibility of the modal-based optimization approach, and it shows the resulting optimum wing configuration and its sensitivity under different flight profiles.
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    Benefits of Tracking Aids on a 1U CubeSat
    (2017) Simpson, Christopher R.; O'Neill, Charles R.; University of Alabama Tuscaloosa
    Incoporating active/passive tracking aids into the design of a university/high school CubeSat mission promotes good space stewardship. Tracking aids are necessary for improved tracking covariance of CubeSats. Tracking aid support and design-space cost are covered. Reflectarrays, patch array(s), and deployable antennas show the potential benefit of transmitting data over S-band frequencies and tracking aids that enhance the mission capabilities. Passive and active tracking aids with low impact on the mission provide reduced covariance of CubeSats orbit tracks shown through use of modeling tools.
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    A CubeSat Train for Radar Sounding and Imaging of Antarctic Ice Sheet
    Gogineni, Prasad; Simpson, Christopher R.; Yan, Jie-Bang; O'Neill, Charles R.; Sood, Rohan; Gurbuz, Sevgi Z.; Gurbuz, Ali C.; University of Alabama Tuscaloosa