A Comparison of Various Methods of Redundant Constraints Handling in Multibody System Simulations

2011 ◽  
Author(s):  
Marek Wojtyra ◽  
Janusz Fra˛czek
Keyword(s):  
Numerical Methods ◽  
Rigid Body ◽  
Input Data ◽  
Augmented Lagrangian ◽  
Multibody System ◽  
Augmented Lagrangian Method ◽  
Point Of View ◽  
The Other ◽  
Redundant Constraints ◽  
Constraints Handling

When redundant constraints are present in a rigid body mechanism, only selected joint reactions can be determined uniquely, whereas the other cannot. Analytic criteria and numerical methods of finding joints with uniquely solvable reactions are available. In this paper the problem of joint reactions solvability is examined from the point of view of numerical methods frequently used for redundant constrains handling in practical simulations. Three methods are discussed: elimination of redundant constraints, pseudoinverse-based calculations and the augmented Lagrangian method. In each method the redundant constraints are treated differently which — in case of joints with non-unique reactions — leads to different reaction solutions. Moreover, it is shown that one and the same method may lead to different solutions, provided that input data are prepared differently. Finally, it is illustrated that — in case of joints with solvable reactions — the obtained solutions are unique, regardless of the method used for redundant constraints handling.

Comparison of Selected Methods of Handling Redundant Constraints in Multibody Systems Simulations

2012 ◽  
Vol 8 (2) ◽  
Author(s):  
Marek Wojtyra ◽  
Janusz Frączek
Keyword(s):  
Numerical Methods ◽  
Rigid Body ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Point Of View ◽  
Redundant Constraints ◽  
Reaction Solution ◽  
Constraints Handling ◽  
Mathematical Operations ◽  
Augmented Lagrangian Formulation

When redundant constraints are present in a rigid body mechanism, only selected (if any at all) joint reactions can be determined uniquely, whereas others cannot. Analytic criteria and numerical methods of finding joints with uniquely solvable reactions are available. In this paper, the problem of joint reactions solvability is examined from the point of view of selected numerical methods frequently used for handling redundant constraints in practical simulations. Three different approaches are investigated in the paper: elimination of redundant constraints; pseudoinverse-based calculations; and the augmented Lagrangian formulation. Each method is briefly summarized; the discussion is focused on techniques of handling redundant constraints and on joint reactions calculation. In the case of multibody systems with redundant constraints, the rigid body equations of motion are insufficient to calculate some or all joint reactions. Thus, purely mathematical operations are performed in order to find the reaction solution. In each investigated method, the redundant constraints are treated differently, which—in the case of joints with nonunique reactions—leads to different reaction solutions. As a consequence, reactions reflecting the redundancy handling method rather than physics of the system are calculated. A simple example of each method usage is presented, and calculated joint reactions are examined. The paper points out the origins of nonuniqueness of constraint reactions in each examined approach. Moreover, it is shown that one and the same method may lead to different reaction solutions, provided that input data are prepared differently. Finally, it is demonstrated that—in case of joints with solvable reactions—the obtained solutions are unique, regardless of the method used for redundant constraints handling.

scholarly journals An augmented Lagrangian method for solving total variation (TV)-based image registration model

2020 ◽  
Vol 14 ◽  
pp. 174830262097353
Author(s):  
Noppadol Chumchob ◽  
Ke Chen
Keyword(s):  
Image Registration ◽  
Augmented Lagrangian ◽  
Numerical Solutions ◽  
Augmented Lagrangian Method ◽  
Closed Form Solution ◽  
Numerical Algorithms ◽  
Lagrangian Method ◽  
Form Solution ◽  
The Other ◽  
Other Hand

Variational methods for image registration basically involve a regularizer to ensure that the resulting well-posed problem admits a solution. Different choices of regularizers lead to different deformations. On one hand, the conventional regularizers, such as the elastic, diffusion and curvature regularizers, are able to generate globally smooth deformations and generally useful for many applications. On the other hand, these regularizers become poor in some applications where discontinuities or steep gradients in the deformations are required. As is well-known, the total (TV) variation regularizer is more appropriate to preserve discontinuities of the deformations. However, it is difficult in developing an efficient numerical method to ensure that numerical solutions satisfy this requirement because of the non-differentiability and non-linearity of the TV regularizer. In this work we focus on computational challenges arising in approximately solving TV-based image registration model. Motivated by many efficient numerical algorithms in image restoration, we propose to use augmented Lagrangian method (ALM). At each iteration, the computation of our ALM requires to solve two subproblems. On one hand for the first subproblem, it is impossible to obtain exact solution. On the other hand for the second subproblem, it has a closed-form solution. To this end, we propose an efficient nonlinear multigrid (NMG) method to obtain an approximate solution to the first subproblem. Numerical results on real medical images not only confirm that our proposed ALM is more computationally efficient than some existing methods, but also that the proposed ALM delivers the accurate registration results with the desired property of the constructed deformations in a reasonable number of iterations.

scholarly journals Assessment of OpenMP Master–Slave Implementations for Selected Irregular Parallel Applications

Electronics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1188
Author(s):  
Paweł Czarnul
Keyword(s):  
Numerical Integration ◽  
Input Data ◽  
Region Of Interest ◽  
Point Of View ◽  
The Other ◽  
Parallel Applications ◽  
Data Generation ◽  
Adaptive Quadrature ◽  
Application Point ◽  
Computing Accuracy

The paper investigates various implementations of a master–slave paradigm using the popular OpenMP API and relative performance of the former using modern multi-core workstation CPUs. It is assumed that a master partitions available input into a batch of predefined number of data chunks which are then processed in parallel by a set of slaves and the procedure is repeated until all input data has been processed. The paper experimentally assesses performance of six implementations using OpenMP locks, the tasking construct, dynamically partitioned for loop, without and with overlapping merging results and data generation, using the gcc compiler. Two distinct parallel applications are tested, each using the six aforementioned implementations, on two systems representing desktop and worstation environments: one with Intel i7-7700 3.60GHz Kaby Lake CPU and eight logical processors and the other with two Intel Xeon E5-2620 v4 2.10GHz Broadwell CPUs and 32 logical processors. From the application point of view, irregular adaptive quadrature numerical integration, as well as finding a region of interest within an irregular image is tested. Various compute intensities are investigated through setting various computing accuracy per subrange and number of image passes, respectively. Results allow programmers to assess which solution and configuration settings such as the numbers of threads and thread affinities shall be preferred.

scholarly journals Comparison of Selected Formulations for Multibody System Dynamics with Redundant Constraints

2016 ◽  
Vol 63 (1) ◽  
pp. 93-112 ◽  
Author(s):  
Marcin Pękal ◽  
Janusz Fraczek
Keyword(s):  
System Dynamics ◽  
Multibody Systems ◽  
Solution Method ◽  
Integration Method ◽  
Multibody System ◽  
The Other ◽  
Direct Integration ◽  
Redundant Constraints ◽  
Direct Integration Method ◽  
Integration Errors

Abstract This paper compares selected optimization-based methods for the analysis of multibody systems with redundant constraints. The following numerical schemes are examined: direct integration method, Udwadia-Kalaba formulation, two types of least-squares block solution method and Udwadia-Phohomsiri formulation. In order to compare efficiency of the algorithms, a series of simulations is performed on two exemplary McPherson struts. In the first variant, the mechanism has no redundant constraints whereas the other is overconstrained. Three constraint stabilization schemes are also compared in terms of integration errors.

scholarly journals Numerical Modeling Methods for Large Open Loop Multibody System

2020 ◽  
Vol 8 (6) ◽  
pp. 5385-5388
Keyword(s):  
Differential Equations ◽  
Augmented Lagrangian ◽  
Multibody System ◽  
Numerical Models ◽  
Augmented Lagrangian Method ◽  
Open Loop ◽  
Large System ◽  
Lagrangian Formulation ◽  
Recursive Method ◽  
Augmented Lagrangian Formulation

A pendulum’s motion was stated to be as a way to illustrate the movement of human body in the studies of multibody system. Therefore, a comparison between the two numerical models in multibody systems were implemented on the articulated pendulums of different sizes. The two numerical models were known as the augmented Lagrangian formulation and fully recursive method. In order to identify the difference performance of the numerical models, various size of articulated pendulums has been tested which are 2, 4, 8, 16, 20 and 40 pendulums. Differential equations developed from both models were solved by using Runge-Kutta 4 and 5. Both models were coded in Matlab and have been optimized in order to ensure only related routine were considered. The performance was evaluated based on the computing time with constant relative and absolute tolerance in Runge-Kutta solver which is 0.01 s. All pendulums were assumed to have the same weight, angle and length. As for the results, the augmented Lagrangian formulation solved the differential equations faster than the fully recursive method when tested up to 20 pendulums. However, fully recursive method started to solve the differential equations faster than the augmented Lagrangian method when it need to deal with a very large system such as 40 pendulums and above. Thus, it can be concluded that the suitable method to solve the small, open loop system such as articulated pendulums is augmented Lagrangian method while for a very large system, the fully recursive method will be more efficient.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

RHYNCHOLITES AND THE PROBLEM OF NARROW AND BROAD CONCEPTION OF TAXONS

2018 ◽  
pp. 12-17 ◽  
Author(s):  
I. R. Khuzina ◽  
V. N. Komarov
Keyword(s):  
Sexual Dimorphism ◽  
Morphological Characteristics ◽  
Mass Scale ◽  
Individual Variability ◽  
Point Of View ◽  
The Other ◽  
New Taxon ◽  
Artificial System ◽  
Broad Understanding

The paper considers a point of view, based on the conception of the broad understanding of taxons. According to this point of view, rhyncholites of the subgenus Dentatobeccus and Microbeccus are accepted to be synonymous with the genus Rhynchoteuthis, and subgenus Romanovichella is considered to be synonymous with the genus Palaeoteuthis. The criteria, exercising influence on the different approaches to the classification of rhyncholites, have been analyzed (such as age and individual variability, sexual dimorphism, pathological and teratological features, degree of disintegration of material), underestimation of which can lead to inaccuracy. Divestment of the subgenuses Dentatobeccus, Microbeccus and Romanovichella, possessing very bright morphological characteristics, to have an independent status and denomination to their synonyms, has been noted to be unjustified. An artificial system (any suggested variant) with all its minuses is a single probable system for rhyncholites. The main criteria, minimizing its negative sides and proving the separation of the new taxon, is an available mass-scale material. The narrow understanding of the genus, used in sensible limits, has been underlined to simplify the problem of the passing the view about the genus to the other investigators and recognition of rhyncholites for the practical tasks.

Birlikte Yaşama Kültürü Çerçevesinde Avrupa Birliği ve Türkiye Politikaları: Suriyelilere Yönelik Tutumun Sultanbeyli Örneği Üzerinden Değerlendirilmesi

2017 ◽  
Vol 4 (1) ◽  
pp. 41-61
Author(s):  
Pelin Sönmez ◽  
Abulfaz Süleymanov
Keyword(s):  
Civil Wars ◽  
Large Scale ◽  
Social Acceptance ◽  
Point Of View ◽  
The Other ◽  
Syrian Refugees ◽  
The European Union ◽  
International Protection ◽  
Legal Structure ◽  
Turkish People

Türkiye, Cumhuriyet tarihinin en yoğun zorunlu göç dalgasını 2011 yılından bu yana süren Suriye Savaşı ile yaşamaktadır. Suriye vatandaşlarının geçici koruma statüsü altında Türkiye toplumuna her açıdan entegrasyonları günümüzün ve geleceğin politika öncelikleri arasında düşünülmelidir. Öte yandan ülkeye kabul edilen sığınmacıların kendi kültürel kimliğini kaybetmeden içinde yaşadığı ev sahibi topluma uyumu, ortak yaşam kültürünün gelişmesi açısından önem arz etmektedir. Bu makalede, "misafir" olarak kabul edilen Suriyeli vatandaşların Türk toplumunca kabul edilmeleri ve dışlanma risklerinin azaltılmasına yönelik devlet politikaları ortaya konularak, üye ve aday ülkelere göçmenlerin dışlanmasını önlemek için Avrupa Birliği (AB) tarafından sunulan hukuki yapı ve kamu hizmeti inisiyatifleri incelenmekte, birlikte yaşam kültürü çerçevesinde Suriyeli vatandaşlara yönelik  toplumsal kabul düzeyleri ele alınmaktadır. Çalışma iki ana bölümden oluşmaktadır: göçmen ve sığınmacılara karşı toplumsal dışlanmayı engellemek için benimsenen yasa ve uygulamaların etkisi ve İstanbul-Sultanbeyli bölgesinde Suriyeli sığınmacılarla ilgili toplumsal algı çalışmasının sonuçları. Bölgede ikamet eden Suriyelilere yönelik toplumsal kabul düzeyinin yüksek olduğu görülürken, halkın Suriyelileri kendilerine  kültürel ve dini olarak yakın hissetmesi toplumsal kabul düzeyini olumlu etkilemektedir. ABSTRACT IN ENGLISHAn evaluation of the European Union and Turkish policies regarding the culture of living togetherThis article aims to determine the level of social acceptance towards Syrians within the context of cohabitation culture by evaluating EU’s legal structure and public service initiatives in order to prevent Syrian refugees from being excluded in member and candidate countries and by revealing government policies on acceptance of Syrians as “guest” by Turkish society and minimizing the exclusion risks of them. This article consists of two main parts, one of which is based on the effects of law and practices preventing refugees and asylum seekers from social exclusion, and the other is on the results of social perception on Syrians in Sultanbeyli district of Istanbul. At the end of 5-years taking in Syrian War, it is obvious that most of more than 3 million Syrian with unregistered ones in Turkey are “here to stay”. From this point of view, the primary scope of policies should be specified in order to remove side effects of refugee phenomenon seen as weighty matter by bottoming out the exclusion towards those people. To avoid possible large-scale conflicts or civil wars in the future, the struggle with exclusion phenomenon plays a crucial role regarding Turkey’s sociological situation and developing policies. In the meaning of forming a model for Turkey, a subtitle in this article is about public services for European-wide legal acquis and practices carried out since 1970s in order to prevent any exclusion from the society. On the other hand, other subtitles are about legal infrastructure and practices like Common European Asylum and Immigration Policies presented in 2005, and Law on Foreigners and International Protection introduced in 2013. In the last part of the article, the results of a field survey carried out in a district of Istanbul were used to analyze the exclusion towards refugees in Turkey. A face-to-face survey was randomly conducted with 200 settled refugees in Sultanbeyli district of Istanbul, and their perceptions towards Syrian people under temporary protection were evaluated. According to the results, the level of acceptance for Syrians living in this district seems relatively high. The fact that Turkish people living in the same district feel close to Syrian refugees culturally and religiously affect their perception in a positive way: however, it is strikingly seen and understood that local residents cop an attitude on the refugees’ becoming Turkish citizens.

Sign in / Sign up

Export Citation Format

Share Document