Myles L. Baker

Generation of Aeroservoelastic Reduced Order Models Using Time Scaling

Design of modern control laws motivates the creation of state-space models from aeroservoelastic models. Balanced truncation is often used to create reduced-order models. In the present work, a reduced order model that employs time scaling in computing the balancing transformation is developed. The transformation matrix necessary to transform the original (unscaled) aeroservoelastic model is found from that corresponding to the time scaled model. Results from an aeroservoelastic wing and a supersonic transport model are shown and it is demonstrated that with an appropriate choice of time scaling, the methodology results in greatly improved conditioning for the Lyapunov equations used to find the Gramians employed in the balancing transformation.

SpaRibs Geometry Parameterization for Wings with Multiple Sections using Single Design

The SpaRibs topology of an aircraft wing has a significant effect on its structural behavior and stability as well as the flutter performance. The development of additive manufacturing techniques like Electron Beam Free Form Fabrication (EBF3) has made it feasible to manufacture aircraft wings with curvilinear spars, ribs (SpaRibs) and stiffeners. In this article a new global-local optimization framework for wing with multiple sections using curvilinear SpaRibs is described. A single design space is used to parameterize the SpaRibs geometry. This method has been implemented using MSC-PATRAN to create a broad range of SpaRibs topologies using limited number of parameters. It ensures C0 and C1 continuities in SpaRibs geometry at the junction of two wing sections with airfoil thickness gradient discontinuity as well as mesh continuity between all structural components. This method is advantageous in complex multi-disciplinary optimization due to its potential to reduce the number of design variables. For the global-local optimization the local panels are generated by an algorithm which is totally based on a set algebra on the connectivity matrix data. The great advantage of this method is that it is completely independent of the coordinates of the nodes of the finite element model. It is also independent of the order in which the elements are distributed in the FEM. The code is verified by optimizing of the CRM Baseline model at trim condition at Mach number equal to 0.85 for five different angle of attack (-2deg, 0deg,2deg,4deg and 6deg). The final weight of the wing is 19,090.61 lb. This value is comparable to that obtained by Qiang et al. 6 (19,269 lb).

Optimization of High Altitude Long Endurance (HALE) Vehicle Subject to Flutter Speed Constraint

A class of air vehicles known as high altitude long endurance (HALE) has gained interest for a broad range of applications. Endurance requirements generally lead to vehicles with low mass and high aspect ratio wings. Such configurations are generally susceptible to aeroelastic effects including flutter. This work considers the aeroelastic behavior of a generic flying wing HALE vehicle configuration using generic stiffness and mass properties. An optimization study is presented that seeks to minimize penalties on trim drag and structural mass while satisfying a constraint on flutter speed. Optimization techniques employed include gradient based and a genetic algorithm. A Pareto Frontier is characterized that presents the set of designs that optimally satisfy the flutter constraint for a range of mass and drag penalties. This paper illustrates techniques that can be applied for optimization subject to aeroelastic constraints for general aircraft.