6,228 research outputs found
Dev2PQ: Planar Quadrilateral Strip Remeshing of Developable Surfaces
We introduce an algorithm to remesh triangle meshes representing developable
surfaces to planar quad dominant meshes. The output of our algorithm consists
of planar quadrilateral (PQ) strips that are aligned to principal curvature
directions and closely approximate the curved parts of the input developable,
and planar polygons representing the flat parts of the input. Developable
PQ-strip meshes are useful in many areas of shape modeling, thanks to the
simplicity of fabrication from flat sheet material. Unfortunately, they are
difficult to model due to their restrictive combinatorics and locking issues.
Other representations of developable surfaces, such as arbitrary triangle or
quad meshes, are more suitable for interactive freeform modeling, but generally
have non-planar faces or are not aligned to principal curvatures. Our method
leverages the modeling flexibility of non-ruling based representations of
developable surfaces, while still obtaining developable, curvature aligned
PQ-strip meshes. Our algorithm optimizes for a scalar function on the input
mesh, such that its level sets are extrinsically straight and align well to the
locally estimated ruling directions. The condition that guarantees straight
level sets is nonlinear of high order and numerically difficult to enforce in a
straightforward manner. We devise an alternating optimization method that makes
our problem tractable and practical to compute. Our method works automatically
on any developable input, including multiple patches and curved folds, without
explicit domain decomposition. We demonstrate the effectiveness of our approach
on a variety of developable surfaces and show how our remeshing can be used
alongside handle based interactive freeform modeling of developable shapes
Redundant motor drive system
A drive system characterized by a base supporting a pair of pillars arranged in spaced parallelism, a shaft extended between and supported by the pillars for rotation about the longitudinal axis thereof, a worm gear affixed to the shaft and supported in coaxial relation therewith is described. A bearing housing of a sleeve like configuration is concentrically related to the shaft and is supported thereby for free rotation. A first and a second quiescent drive train, alternatively activatable, is provided for imparting rotation into said bearing housing. Each of the drive trains is characterized by a selectively energizable motor connected to a spur gear
Design, manufacture and spin test of high contact ratio helicopter transmission utilizing Self-Aligning Bearingless Planetary (SABP)
A 450 hp high ratio Self-Aligning Bearingless Planetary (SABP) for a helicopter application was designed, manufactured, and spin tested under NASA contract NAS3-24539. The objective of the program was to conduct research and development work on a high contact ratio helical gear SABP to reduce weight and noise and to improve efficiency. The results accomplished include the design, manufacturing, and no-load spin testing of two prototype helicopter transmissions, rated at 450 hp with an input speed of 35,000 rpm and an output speed of 350 rpm. The weight power density ratio of these gear units is 0.33 lb hp. The measured airborne noise at 35,000 rpm input speed and light load is 94 dB at 5 ft. The high speed, high contact ratio SABP transmission appears to be significantly lighter and quieter than comtemporary helicopter transmissions. The concept of the SABP is applicable not only to high ratio helicopter type transmissions but also to other rotorcraft and aircraft propulsion systems
Learning quadrangulated patches for 3D shape parameterization and completion
We propose a novel 3D shape parameterization by surface patches, that are
oriented by 3D mesh quadrangulation of the shape. By encoding 3D surface detail
on local patches, we learn a patch dictionary that identifies principal surface
features of the shape. Unlike previous methods, we are able to encode surface
patches of variable size as determined by the user. We propose novel methods
for dictionary learning and patch reconstruction based on the query of a noisy
input patch with holes. We evaluate the patch dictionary towards various
applications in 3D shape inpainting, denoising and compression. Our method is
able to predict missing vertices and inpaint moderately sized holes. We
demonstrate a complete pipeline for reconstructing the 3D mesh from the patch
encoding. We validate our shape parameterization and reconstruction methods on
both synthetic shapes and real world scans. We show that our patch dictionary
performs successful shape completion of complicated surface textures.Comment: To be presented at International Conference on 3D Vision 2017, 201
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