Iterative refinement algorithm for efficient velocities and accelerations solutions in closed-loop multibody dynamics

2021 ◽  
Vol 152 ◽  
pp. 107463
Author(s):  
Yongjun Pan ◽  
Wei Dai ◽  
Liming Huang ◽  
Zhixiong Li ◽  
Aki Mikkola
Keyword(s):  
Multibody Dynamics ◽  
Closed Loop ◽  
Iterative Refinement ◽  
Refinement Algorithm

Double shear layer evolution on the non-uniform computational mesh

2021 ◽  
Author(s):  
Yu M. Kulikov ◽  
E. E. Son
Keyword(s):  
Shear Layer ◽  
Iterative Refinement ◽  
The Novel ◽  
Original Sequence ◽  
Double Shear ◽  
Computational Mesh ◽  
Mesh Resolution ◽  
Initial Vorticity ◽  
High Resolution Technique ◽  
Refinement Algorithm

Abstract This paper considers the canonical problem of a thin shear layer evolution at Reynolds number Re = 400000 using the novel Compact Accurately Boundary Adjusting high-Resolution Technique (CABARET). The study is focused on the effect of the specific mesh refinement in the high shear rate areas on the flow properties under the influence of the developing instability. The original sequence of computational meshes (256^2, 512^2, 1024^2, 2048^2 cells) is modified using an iterative refinement algorithm based on the hyperbolic tangent. The properties of the solutions obtained are discussed in terms of the initial momentum thickness and the initial vorticity thickness, viscous and dilatational dissipation rates and also integral enstrophy. The growth rate for the most unstable mode depending on the mesh resolution is considered. In conclusion the accuracy of calculated mesh functions is estimated via L1, L2, L∞ norms.

An Iterative Refinement Algorithm for the Minimum Branch Vertices Problem

2011 ◽  
pp. 421-433 ◽  
Author(s):  
Diego M. Silva ◽  
Ricardo M. A. Silva ◽  
Geraldo R. Mateus ◽  
José F. Gonçalves ◽  
Mauricio G. C. Resende ◽  
...  
Keyword(s):  
Iterative Refinement ◽  
Refinement Algorithm

Research on the Repeater Optimization Based on Voronoi Model

2012 ◽  
Vol 588-589 ◽  
pp. 802-805
Author(s):  
Ban Teng Liu ◽  
Xi Lin Hu ◽  
Zheng Yu Xu ◽  
Yao Lin Liu ◽  
You Rong Chen
Keyword(s):  
Cellular Networks ◽  
Voronoi Diagram ◽  
Iterative Refinement ◽  
Local Optimum ◽  
Limited Capacity ◽  
Circular Area ◽  
Absolute Minimum ◽  
Voronoi Regions ◽  
Refinement Algorithm ◽  
Better Than

This paper propose a two-tiered network in which lower-power users communicate with one another through repeaters, which amplify signals and retransmit them, have limited capacity, and may interfere with one another if their transmitter frequencies are close and they share the same private-line tone. Motivated by cellular networks, this paper gives a naive solution where the number of repeaters and their positions can be obtained analytically. In a circular area with radius 40 miles, 12 repeaters can accommodate 1,000 simultaneous users. This paper further propose an iterative refinement algorithm consisting of three fundamental modules that draw the Voronoi diagram, determine the centers of the circumscribed circles of the Voronoi regions, and escape the local optimum by using external optimization. The algorithm obtains a solution with 11 repeaters, which we prove to be the absolute minimum. For 10,000 users, it uses 104 repeaters, better than the naive solution's 108.

scholarly journals ACCURATE OPTICAL TARGET POSE DETERMINATION FOR APPLICATIONS IN AERIAL PHOTOGRAMMETRY

2016 ◽  
Vol III-3 ◽  
pp. 257-262 ◽  
Author(s):  
D. A. Cucci
Keyword(s):  
Target Position ◽  
Iterative Refinement ◽  
Target Size ◽  
Geometric Invariant ◽  
Pose Determination ◽  
Aerial Photogrammetry ◽  
Circle Center ◽  
Position And Orientation ◽  
Orientation Determination ◽  
Refinement Algorithm

We propose a new design for an optical coded target based on concentric circles and a position and orientation determination algorithm optimized for high distances compared to the target size. If two ellipses are fitted on the edge pixels corresponding to the outer and inner circles, quasi-analytical methods are known to obtain the coordinates of the projection of the circles center. We show the limits of these methods for quasi-frontal target orientations and in presence of noise and we propose an iterative refinement algorithm based on a geometric invariant. Next, we introduce a closed form, computationally inexpensive, solution to obtain the target position and orientation given the projected circle center and the parameters of the outer circle projection. The viability of the approach is demonstrated based on aerial pictures taken by an UAV from elevations between 10 to 100 m. We obtain a distance RMS below 0.25 % under 50 m and below 1 % under 100 m with a target size of 90 cm, part of which is a deterministic bias introduced by image exposure.

scholarly journals ACCURATE OPTICAL TARGET POSE DETERMINATION FOR APPLICATIONS IN AERIAL PHOTOGRAMMETRY

2016 ◽  
Vol III-3 ◽  
pp. 257-262 ◽  
Author(s):  
D. A. Cucci
Keyword(s):  
Target Position ◽  
Iterative Refinement ◽  
Target Size ◽  
Geometric Invariant ◽  
Pose Determination ◽  
Aerial Photogrammetry ◽  
Circle Center ◽  
Position And Orientation ◽  
Orientation Determination ◽  
Refinement Algorithm

We propose a new design for an optical coded target based on concentric circles and a position and orientation determination algorithm optimized for high distances compared to the target size. If two ellipses are fitted on the edge pixels corresponding to the outer and inner circles, quasi-analytical methods are known to obtain the coordinates of the projection of the circles center. We show the limits of these methods for quasi-frontal target orientations and in presence of noise and we propose an iterative refinement algorithm based on a geometric invariant. Next, we introduce a closed form, computationally inexpensive, solution to obtain the target position and orientation given the projected circle center and the parameters of the outer circle projection. The viability of the approach is demonstrated based on aerial pictures taken by an UAV from elevations between 10 to 100 m. We obtain a distance RMS below 0.25 % under 50 m and below 1 % under 100 m with a target size of 90 cm, part of which is a deterministic bias introduced by image exposure.

Solution of Multibody Dynamics Using Natural Factors and Iterative Refinement: Part II — Closed Kinematic Loops

1989 ◽  
Author(s):  
R. A. Wehage
Keyword(s):  
Computer Architecture ◽  
Closed Loop ◽  
Equations Of Motion ◽  
Open Loop ◽  
Force Balance ◽  
Iterative Refinement ◽  
Dynamic Force ◽  
Computational Overhead ◽  
Natural Factors ◽  
Kinematic Loops

Abstract A symbolic algorithm exploiting natural factors of generalized inertia matrices and iterative refinement to compute the dynamics of open kinematic-loop systems was developed in Part I of this paper. The general equations of motion for open and closed loop systems were derived in an earlier paper (Wehage, 1988) and it was shown that algorithms for open loop dynamics could be used to solve closed loop problems by cutting the secondary joints. In this paper it is shown that secondary joint forces can be obtained either from a dynamic force balance or from constraint surface deformations. Closed kinematic loops create additional numerical problems and require substantially more computational overhead. Therefore the iterative refinement algorithm developed in Part I is extended to address some of these problems. Exploitation of iterative refinement and computer architecture can substantially improve overall algorithm performance.

Application of Multibody Dynamics to On-Orbit Manipulator Simulations

2005 ◽  
Author(s):  
Leslie J. Quiocho ◽  
An Huynh ◽  
Edwin Z. Crues
Keyword(s):  
Multibody Dynamics ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Multibody System ◽  
Mass Matrix ◽  
Parent Body ◽  
System Level ◽  
Engineering Analysis ◽  
Tree Topologies ◽  
Important Notion

This paper discuses a generic multibody dynamics formulation and associated computer algorithm that addresses the variety of manipulator simulation requirements for engineering analysis, procedures development, and crew familiarization/training at the NASA Johnson Space Center (JSC). The formulation is based on body to body relationships with no concept of branched tree topologies. This important notion results in a single recursion pass to construct a system level mass matrix as opposed to the traditional inbound/outbound passes required by the other recursive methods. Moreover, the formulation can be augmented to account for closed loop topologies. The base body of the structure can be fixed or free; each subsequent body, if any, is attached to its parent body via any combination of rotational or translational degrees of freedom (DOFs). Furthermore, each body in the multibody system can be defined as rigid or flexible. The algorithm is designed to partition the data variables and associated computations for multi-frequency or multi-process computation. The resulting algorithm requires approximately one third the computations (in terms of additions and multiplications) of techniques previously used at the NASA JSC.

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