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The objective of this paper is to describe the design and implementation of a small semiautonomous fixed-wing unmanned air vehicle. In particular we describe the hardware and software architectures used in the design. We also describe a low weight, low cost autopilot developed at Brigham Young University and the algorithms associated with the autopilot. Novel PDA and voice interfaces to the UAV are described. In addition, we overview our approach to real-time path planning, trajectory generation, and trajectory tracking. The paper is augmented with movie files that demonstrate the functionality of the UAV and its control software.

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A tailsitter UAV has unique advantages over typical fixed wing aircraft or hovercraft. This paper highlights topics of interest in our preliminary research in developing a tailsitter UAV. An aerodynamic model and quaternion-based attitude and position control scheme is presented for controlling a tailsitter through hover maneuvers, with simulation results. Desired trajectories are also developed through feedback linearization of the dynamic equations, intended for quaternion-based attitude control. Finally, a hardware platform is proposed.

Numerical calculations for three-dimensional, unsteady, laminar, bubble-type vortex breakdown within a tube-and-vane-type apparatus at a Reynolds number of 2000 and circulation number Ω=1.41 are presented. This study is unique in that rather than specifying the inlet swirl velocity through a fit to experimental data (or a Burgers profile), the swirl was induced by directing the fluid through an array of 16 turning vanes, the arrangement being similar to that employed in the original experimental works of Sarpkaya [J. Fluid Mech. 45, 545 (1971); AIAA J. 12, 602 (1974)]. The interior of the resulting breakdown bubble consisted of one primary torroidal recirculation cell, which was tilted from, and found to gyrate about, the bubble centerline. The dominant frequency of gyration was identified, and the mechanism of fluid exchange examined. Subsequent calculations were performed using fixed inlet swirl and axial velocity profiles that were obtained from the results computed using the full geometry (including the turning vanes). Results revealed no significant difference in the downstream breakdown location or structure.