7,680 research outputs found
A general formulation of Bead Models applied to flexible fibers and active filaments at low Reynolds number
This contribution provides a general framework to use Lagrange multipliers
for the simulation of low Reynolds number fiber dynamics based on Bead Models
(BM). This formalism provides an efficient method to account for kinematic
constraints. We illustrate, with several examples, to which extent the proposed
formulation offers a flexible and versatile framework for the quantitative
modeling of flexible fibers deformation and rotation in shear flow, the
dynamics of actuated filaments and the propulsion of active swimmers.
Furthermore, a new contact model called Gears Model is proposed and
successfully tested. It avoids the use of numerical artifices such as repulsive
forces between adjacent beads, a source of numerical difficulties in the
temporal integration of previous Bead Models.Comment: 41 pages, 15 figure
Shape Animation with Combined Captured and Simulated Dynamics
We present a novel volumetric animation generation framework to create new
types of animations from raw 3D surface or point cloud sequence of captured
real performances. The framework considers as input time incoherent 3D
observations of a moving shape, and is thus particularly suitable for the
output of performance capture platforms. In our system, a suitable virtual
representation of the actor is built from real captures that allows seamless
combination and simulation with virtual external forces and objects, in which
the original captured actor can be reshaped, disassembled or reassembled from
user-specified virtual physics. Instead of using the dominant surface-based
geometric representation of the capture, which is less suitable for volumetric
effects, our pipeline exploits Centroidal Voronoi tessellation decompositions
as unified volumetric representation of the real captured actor, which we show
can be used seamlessly as a building block for all processing stages, from
capture and tracking to virtual physic simulation. The representation makes no
human specific assumption and can be used to capture and re-simulate the actor
with props or other moving scenery elements. We demonstrate the potential of
this pipeline for virtual reanimation of a real captured event with various
unprecedented volumetric visual effects, such as volumetric distortion,
erosion, morphing, gravity pull, or collisions
Real Time Animation of Virtual Humans: A Trade-off Between Naturalness and Control
Virtual humans are employed in many interactive applications using 3D virtual environments, including (serious) games. The motion of such virtual humans should look realistic (or ‘natural’) and allow interaction with the surroundings and other (virtual) humans. Current animation techniques differ in the trade-off they offer between motion naturalness and the control that can be exerted over the motion. We show mechanisms to parametrize, combine (on different body parts) and concatenate motions generated by different animation techniques. We discuss several aspects of motion naturalness and show how it can be evaluated. We conclude by showing the promise of combinations of different animation paradigms to enhance both naturalness and control
Computational methods and software systems for dynamics and control of large space structures
Two key areas of crucial importance to the computer-based simulation of large space structures are discussed. The first area involves multibody dynamics (MBD) of flexible space structures, with applications directed to deployment, construction, and maneuvering. The second area deals with advanced software systems, with emphasis on parallel processing. The latest research thrust in the second area involves massively parallel computers
Dynamic analysis of flexible mechanical systems using LATDYN
A 3-D, finite element based simulation tool for flexible multibody systems is presented. Hinge degrees-of-freedom is built into equations of motion to reduce geometric constraints. The approach avoids the difficulty in selecting deformation modes for flexible components by using assumed mode method. The tool is applied to simulate a practical space structure deployment problem. Results of examples demonstrate the capability of the code and approach
Model-based Aeroservoelastic Design and Load Alleviation of Large Wind Turbine Blades
This paper presents an aeroservoelastic modeling approach for dynamic load alleviation
in large wind turbines with trailing-edge aerodynamic surfaces. The tower, potentially on a
moving base, and the rotating blades are modeled using geometrically non-linear composite
beams, which are linearized around reference conditions with arbitrarily-large structural
displacements. Time-domain aerodynamics are given by a linearized 3-D unsteady vortexlattice
method and the resulting dynamic aeroelastic model is written in a state-space
formulation suitable for model reductions and control synthesis. A linear model of a single
blade is used to design a Linear-Quadratic-Gaussian regulator on its root-bending moments,
which is finally shown to provide load reductions of about 20% in closed-loop on the full
wind turbine non-linear aeroelastic model
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