Design and Dynamic Analysis of a Variable-Sweep, Variable-Span Morphing UAV

Morphing wings have the potential to optimize UAV performance for a variety of flight conditions and maneuvers. The ability to vary both the wing sweep and span can enable maximum performance for a diverse range of flight regimes. For example, low-speed missions can be optimized using a wing with high aspect ratio and no wing sweep whereas high-speed missions are optimized with low aspect ratio wings and large wing sweep. Different static morphing wing configurations clearly result in varying aerodynamics and, as a result, varying dynamic modes. Another important consideration, however, is the transient dynamics that occur when transitioning between morphing configurations, which is clearly a function of the rate of transition. For smaller-scale morphing UAVs, morphing transitions can take place on a time scale comparable to the dynamics of the vehicle, which implies that the transient dynamics must be taken into account when modeling the dynamics of such a vehicle. This thesis considers the dynamic effects of morphing for a variable-sweep, variable-span UAV. A scale model of such a morphing wing has been fabricated and tested in the low-speed wind tunnel at Embry-Riddle Aeronautical University. The focus of this thesis is the development of a dynamic model for this morphing wing UAV that accounts for not only the varying dynamics resulting from different static morphing configurations, but also the transient dynamics associated with morphing. A Vortex Lattice Method (VLM) solver is used to model the aerodynamics of the morphing wing UAV over a two-dimensional array of static configurations corresponding to varying span and sweep. In this analysis, only symmetric morphing configurations are considered (i.e., in every configuration, both wings have the same span and sweep); therefore, the analysis focuses on the longitudinal dynamic modes (i.e., the long period and short period modes). The dynamic model of the morphing wing UAV is used to develop a simulation in which it is possible to specify different morphing configurations as well as varying rates of morphing transition. As such, the simulation provides an invaluable tool for analyzing the effects of wing morphing on the longitudinal flight dynamics of a morphing UAV

Direct Adaptive Control for a Trajectory Tracking UAV

This research focuses on the theoretical development and analysis of a direct adaptive control algorithm to enable a fixed-wing UAV to track reference trajectories while in the presence of persistent external disturbances. A typical application of this work is autonomous flight through urban environments, where reference trajectories would be provided by a path planning algorithm and the vehicle would be subjected to significant wind gust disturbances. Full 6-DOF nonlinear and linear UAV simulation models are developed and used to study the performance of the direct adaptive control system for various scenarios. A stability proof is developed to prove convergence of the direct adaptive control system under certain conditions. Specific adaptive controller implementation details are provided, including the use of a sensor blending algorithm to address the non-minimum phase properties of the UAV models. The robustness of the adaptive system pertaining to the amount of modeling error that can be accommodated by the controller is studied, and the disturbance rejection capabilities and limitations of the controllers are also analyzed. The overall results of this research demonstrate that the direct adaptive control algorithm can enable trajectory tracking in cases where there are both significant uncertainties in the external disturbances and considerable error in the UAV model