Fabrication methods for mesoscopic flying vehicle.

摘要

Small-scale flying vehicles are attractive tools for atmospheric science research. A centimeter-size mesoscopic electric helicopter, the mesicopter, has been developed at Stanford University for these applications. The mesoscopic scale implies a design with critical features between tens of microns and several millimeters. Three major parts in the mesicopter are challenging to manufacture. Rotors require smooth 3D surfaces and a blade thickness of less than 100 μm. Components in the DC micro-motor must be made of engineering materials, which is difficult on the mesoscopic scale. Airframe fabrication has to integrate complex 3D geometry into one single structure at this scale. In this research, material selection and manufacturing approaches have been investigated and implemented.; In rotor fabrication, high-strength polymers manufactured by the Shape Deposition Manufacturing (SDM) technique were the top choice. Aluminum alloys were only considered as the second choice because the fabrication process is more involved. Lift tests showed that the 4-blade polymer and aluminum rotors could deliver about 90% of the expected lift (4g).; To explain the rotor performance, structural analyses of spinning rotors were performed and the fabricated geometry was investigated. The bending deflections and the torsional twists were found to be too small to degrade aerodynamic performance. The rotor geometry was verified by laser scanning and by cross-section observations.; Commercially available motors are used in the prototypes but a smaller DC micro-motor was designed for future use. Components of the DC micro-motors were fabricated by the Mesoscopic Additive/Subtractive Material Processing technique, which is capable of shaping engineering materials on the mesoscopic scale. The approaches are described in this thesis.; The airframe was manufactured using the SDM process, which is capable of building complex parts without assembly. Castable polymers were chosen and mixed with glass microspheres to reduce their density. The finished airframe (65.5 mm x 65.5 mm) weighed only 1.5g.; Two mesicopter prototypes, weighing 3g and 17g, have illustrated that powered flight at this scale is feasible. This research provides solutions to manufacture the challenging parts for the mesicopter. The manufacturing approaches discussed here are applicable to other small flying vehicles in similar and even smaller size regimes.