Dissertations / Theses: 'Multi Body Dynamic'

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Taghipour, Reza. "Efficient Prediction of Dynamic Response for Flexible and Multi- Body Marine Structures." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2321.

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Sundling, Emma. "Validation toolbox for a Physics Engine." Thesis, Umeå universitet, Institutionen för fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-121972.

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Physics engines become more and more common due to the rapid development and increasing demand of simulations. With this comes a need of testing the engine, a way to measure its performance, not only its speed but also its accuracy and stability. The purpose of this thesis has been to create a set of benchmark tests. They aim to check the physical aspects, especially mechanics, of the engine. A strategy and export functions for the test results in order to automate the testing have also been developed. The resulting tests became a beam on piles which analyses constraint stability, an overdetermined system consisting of a static door on multiple hinges, a falling object investigating the accuracy of the integrator, a box on an inclined plane for testing the friction model, a single pendulum as well as a multibody pendulum checking constraint accuracy and energy conservation, the Earth orbiting around the Sun which tests the stability of the integrator and finally a cantilever beam that is a static test of a real scenario. After the tests are performed the results are presented on an HTML-page. A prototype of a Web application is also established as well as a set of scalar tests that can be performed continuously, in order to follow trends or compare the engine's performance from time to time. This thesis was initialized by Algoryx Simulation AB which also provided the engine, AgX Dynamics, with the numerical method called SPOOK. It mainly performed well on all tests. In order to build a fully general toolbox more tests need to be added such as material interactions, scalable test with thousands of bodies, torque tests as well as more complex scenarios, for example a scissor lift and robots. The work can also be extended with more developed export functions, both to the Web and to documents. Hopefully this thesis can be seen as a complement to the earlier efforts done in creating a general set of benchmarks and automation framework for continuous integration and testing.
Fysikmotorer blir mer och mer vanliga på grund av den snabba utvecklingen och efterfrågan på simuleringar. I och med detta ökar också behovet av att testa motorerna och ett sätt att mäta prestandan, inte bara snabbheten utan också noggrannheten och stabiliteten. Syftet med detta examensarbete har varit att skapa ett set av prestandatester. De syftar till att testa de fysikaliska aspekterna av fysikmotorn, särskilt inom mekanik. En strategi och exportfunktioner för testresultaten för att automatisera testningen har också utvecklats. De resulterande testerna blev en balk på pålar som analyserar stabiliteten hos villkoren, ett överbestämt system bestående av en statisk dörr på flera gångjärn, ett fallande objekt som granskar precisionen hos integratorn, en låda på ett lutande plan som testar friktionsmodellen, en enkel pendel samt en flerkropppspendel som kontrollerar villkorsprecisionen och energikonservering, jordens bana runt solen som testar integratorns stabilitet och slutligen en utskjutande balk som är ett statiskt test av ett verkligt fall. När testerna är genomförda presenteras resultaten på en HTML-sida. En prototyp av en webb-applikation har också utvecklats samt ett set med skalära tester som kan utföras kontinuerligt för att följa upp trender och jämföra motorns prestanda över tid. Det här examensarbetet initierades av Algoryx Simulation AB som även tillhandahållit fysikmotorn, AgX Dynamics, med den numeriska metoden SPOOK. Motorn presterade överlag bra på testerna. För att bygga en allmän verktygslåda behövs fler tester så som interaktion mellan material, skalbara tester med tusentals kroppar samt mer komplexa simuleringar, t.ex. en saxlyft och robotar. Arbetet kan också utökas med mer utvecklade exportfunktioner, både mot webben och som dokument. Förhoppningsvis kan detta ses som ett komplement till de tidigare ansträgningar som gjorts för att skapa ett generellt set av prestandatester och ett automatiskt ramverk för kontinuerlig testning.

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Quadrelli, Bruno Marco. "Dynamic analysis of multi-flexible body systems with spatial beams and finite rotations." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12052.

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Gonzalez, Hernán. "Complex dynamic scene analysis through multi-body motion segmentation : application to intelligent vehicles." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS519.

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Dans le contexte applicatif des Systèmes d'Aide à la Conduite et des Véhicules Autonomes (anglais ADAS), l'analyse de scène est un processus fondamental d'inférence duquel dépendent multiples fonctions d'asservissement et de prise de décision. Le résultat issu de l'analyse de scène permet une description fiable de l'environnement aux alentours du véhicule composée des objets statiques et dynamiques ainsi que des éléments de structure de la scène (e.g. route, espace navigable, marquage routier) et de la localisation du véhicule observateur (e.g. odométrie). Ces informations supportent les décisions et l'engagement d'actions des systèmes automatiques dans la navigation autonome et les manœuvres d'assistance à la conduite. Pour ce faire, les systèmes de perception sont conçus afin de fournir des observations de la scène redondantes et fiables. Dans le cadre de cette thèse nous nous intéressons à la segmentation d'une scène dynamique en utilisant des images issues d'un système de vision monoculaire. Dans un premier temps, une étude bibliographique des approches de l'état de l'art est présentée en contrastant les avantages et les limites des méthodes suivant des indicateurs de performance et de temps de calcul. Cela a permis la sélection d'une méthodologie récente basée vision servant de référence pour la segmentation de mouvement. Parallèlement, une étude approfondie des pré-traitements nécessaires à l'estimation du flot optique a aussi été menée. Cette première étape est clore par une implantation algorithmique pour la l'identification et la formalisation des contributions adressant les limites de l'état de l'art. Dans la deuxième étape de ce travail, nous proposons un algorithme de segmentation de mouvement basée image. Les notions et les méthodes introduites font appel à la technique du Suivi-avant-Detection (anglais Track-before-Detect) en couplage serré aux méthodes de calcul de la structure et du mouvement (anglais Structure from Motion). La méthode dénommée TbD-SfM a pour objectif la réduction de la complexité dans l'analyse de la scène intégrant un modèle de mouvement générique à 6 dégrées de liberté. Et cela en préservant la densité de caractéristiques suivies sur les mouvements observés. Plus tard, nous proposons une variante accélérée de l'algorithme TbD-SfM dénommée ETbD-SfM qui limite efficacement la complexité de la segmentation par rapport au nombre de mouvements observés dans la scène. L'ensemble des contributions a été évalué en utilisant différentes bases de données publiques reconnues dans le domaine des Transports Intelligents. Nous avons étudié les algorithmes TbD-SfM et ETbD-SfM avec le dataset Hopkins dans de conditions idéales : sans erreurs de suivi de caractéristiques et faible vitesse. Le dataset KITTI permit de vérifier la robustesse de l'approche et d'évaluer leur performance dans des scénarios incluant multiples objets en mouvement. Pour conclure, les résultats expérimentaux démontrent que les méthodes TbD-SfM et ETbD-SfM effectuent la segmentation d'une scène dynamique en utilisant un modèle à 6 dégrés de liberté obtenant une faible erreur de ré-projection tout en préservant la densité de caractéristiques essentiel au suivi de mouvement. La géométrie de la scène 3D calculée en estimant le facteur d'échelle est comparée et analysée aux trajectoires 3D des objets référencés dans la scène
In the context of Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, scene understanding is a fundamental inference process in which several servoing and decision making functions depends on. Such a process is intended to retrieve reliable information about the vehicle's surroundings including static and dynamic objects (e.g. obstacles, pedestrians, vehicles), the scene structure (e.g. road, navigable space, lane markings) and ego-localization (e.g. odometry). All this information is essential to make crucial decisions in autonomous navigation and assistance maneuvers. To this end, single or multiple perception systems are designed to provide redundant and reliable observations of the scene. This thesis is devoted and focused on image-based multi-body motion segmentation of dynamic scenes using monocular vision systems. The conducted research starts by surveying methods of the state-of-the-art and contrasting their advantages and drawbacks in terms of performance indicators and computation time. After identifying a recent vision-based methodology, sparse optical flow required pre-processes are studied. As a concept-proof, an algorithm implementation shows, in practice, limits of the addressed approach leading to envision and formalize our contributions. Detecting and tracking objects in a classic processing chain may lead to low-performance and time-consuming solutions. Instead of segmenting moving objects and tracking them independently, a Track-before-Detect framework for a multi-body motion segmentation (namely TbD-SfM) was proposed. This method relies detection and tracking on a tightly coupled strategy intended to reduce the complexity of an existing Multi-body Structure from Motion approach. Efforts were also devoted for reducing the computational cost without introducing any kinematic model constraints and for preserving features density on observed motions. Further, an accelerated implementation variant of TbD (namely ETbD-SfM) was also proposed in order to limit the complexity increasing with respect to the number of observed motions. The proposed methods were extensively tested with different publicly available datasets such as Hopkins155 and KITTI. Hopkins dataset allows a comparison under feature-tracking ideal conditions since the dataset includes referenced optical flow. KITTI provides image sequences under real conditions in order to evaluate robustness of the method. Results on scenarios including the presence of multiple and simultaneous moving objects observed from a moving camera are analyzed and discussed. In conclusion, the obtained results show that TbD-SfM and ETbD-SfM methods can segment dynamic objects using a 6DoF motion model, achieving a low image segmentation error without increasing of computational cost and preserving the density of the feature points. Additionally, the 3D scene geometry and trajectories are provided by estimating scale on the monocular system and comparing these results to referenced object trajectories

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Peng, Tao. "Coupled Multi-body Dynamic and Vibration Analysis of Hypoid and Bevel Geared Rotor System." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282931782.

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Dye, John. "Development and application of computational dynamic and kinematic constrained multi-body system simulations in MATLAB." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3951.

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Historically machine and mechanism design relied heavily upon analytical and graphical means to evaluate the performance a system. With increasing complexity, these methods have been modified for use with computational tools. General purpose solvers have been created such as Adams, DADS and Dap3d to analyze different machines and mechanisms. Although these tools are available, they allow limited access to source code or utilize a language that is not readily taught in academics. This thesis will focus on the creation of a general-purpose simulation enviroment using the currently used programming language Matlab. Four simulation programs have been created allowing simulation of kinematics and dynamics for planar and spatial mechanical systems. Discussed along with the program operation is the mathematics behind normal computational dynamics. A section is dedicated to the solution and its implementation of purely kinematic methods allowing the solution of planar and spatial systems. Constraints are heavily utilized in the formation of multi-body systems and their equations and formulations are detailed. For spatial kinematic simulations, Euler parameters are discussed in detail, and the related equations needed for multibody system simulations have been provided. The mathematics of the dynamic simulations is also discussed, along with addition of non-rigid elements such as springs and dampers. Example simulations of specific systems have also been included, showing the results of interest utilizing the graphical user interfaces that have been created. Along with these examples is a simulation that includes two dimensional beam elements injected into the dynamic solver, which illustrates how multiple fields of engineering can be included in the simulations
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.

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Sagal, Ellen Jean 1954. "An object oriented approach to finite element analysis and multi-body dynamic analysis program designs." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278289.

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Procedurally-oriented computer programs used to perform finite element and multibody dynamics analyses are difficult to understand, use, and modify. A new approach, object-oriented programming, was used to develop a finite element code that is easier to apply, understand, and modify. Object-oriented code is easier to understand, as the characteristics and operations associated with a physical phenomena are grouped in a class whose structure closely parallels the modeled entity. Elements, bodies, joints, and mechanisms are modeled as classes. Program application is facilitated by a hierarchy of class structure. Manipulation of higher level body and mechanism class types direct the complicated, lower level code of element calculations. Lower level code is hidden in an object library resulting in a shorter, simpler driver program for an analysis. Modification and expansion of programs is easily accomplished through object-oriented language features such as modularization of code into classes and overloaded functions. Body and element abstract base classes provide "templates" for creation of new type classes used to develop additional analyses.

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Lantoine, Gregory. "A methodology for robust optimization of low-thrust trajectories in multi-body environments." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37081.

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Future ambitious solar system exploration missions are likely to require ever larger propulsion capabilities and involve innovative interplanetary trajectories in order to accommodate the increasingly complex mission scenarios. Two recent advances in trajectory design can be exploited to meet those new requirements: the use of low-thrust propulsion which enables larger cumulative momentum exchange relative to chemical propulsion; and the consideration of low-energy transfers relying on full multi-body dynamics. Yet the resulting optimal control problems are hypersensitive, time-consuming and extremely difficult to tackle with current optimization tools. Therefore, the goal of the thesis is to develop a methodology that facilitates and simplifies the solution finding process of low-thrust optimization problems in multi-body environments. Emphasis is placed on robust techniques to produce good solutions for a wide range of cases despite the strong nonlinearities of the problems. The complete trajectory is broken down into different component phases, which facilitates the modeling of the effects of multiple bodies and makes the process less sensitive to the initial guess. A unified optimization framework is created to solve the resulting multi-phase optimal control problems. Interfaces to state-of-the-art solvers SNOPT and IPOPT are included. In addition, a new, robust Hybrid Differential Dynamic Programming (HDDP) algorithm is developed. HDDP is based on differential dynamic programming, a proven robust second-order technique that relies on Bellman's Principle of Optimality and successive minimization of quadratic approximations. HDDP also incorporates nonlinear mathematical programming techniques to increase efficiency, and decouples the optimization from the dynamics using first- and second-order state transition matrices. Crucial to this optimization procedure is the generation of the sensitivities with respect to the variables of the system. In the context of trajectory optimization, these derivatives are often tedious and cumbersome to estimate analytically, especially when complex multi-body dynamics are considered. To produce a solution with minimal effort, an new approach is derived that computes automatically first- and high-order derivatives via multicomplex numbers. Another important aspect of the methodology is the representation of low-thrust trajectories by different dynamical models with varying degrees of fidelity. Emphasis is given on analytical expressions to speed up the optimization process. In particular, one novelty of the framework is the derivation and implementation of analytic expressions for motion subjected to Newtonian gravitation plus an additional constant inertial force. Example applications include low-thrust asteroid tour design, multiple flyby trajectories, and planetary inter-moon transfers. In the latter case, we generate good initial guesses using dynamical systems theory to exploit the chaotic nature of these multi-body systems. The developed optimization framework is then used to generate low-energy, inter-moon trajectories with multiple resonant gravity assists.

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Khudher, Dhayaa Raissan. "Synthesis of continuous whole-body motion in hexapod robot for humanitarian demining." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16508.

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In the context of control, the motion of a legged robot is very challenging compared with traditional fixed manipulator. Recently, many researches have been conducted to control the motion of legged robot with different techniques. On the other hand, manipulation tasks have been addressed in many applications. These researches solved either the mobility or the manipulation problems, but integrating both properties in one system is still not available. In this thesis, a control algorithm is presented to control both locomotion and manipulation in a six legged robot. Landmines detection process is considered as a case study of this project to accelerate the mine detection operation by performing both walking and scanning simultaneously. In order to qualify the robot to perform more tasks in addition to the walking task, the joint redundancy of the robot is exploited optimally. The tasks are arranged according to their importance to high level of priority and low level of priority. A new task priority redundancy resolution technique is developed to overcome the effect of the algorithmic singularities and the kinematic singularity. The computational aspects of the solution are also considered in view of a real-time implementation. Due to the dynamic changes in the size of the robot motion space, the algorithm has the ability to make a trade-off between the number of achieved tasks and the imposed constraints. Furthermore, an appropriate hierarchy is imposed in order to ensure an accurate decoupling between the executed tasks. The dynamic effect of the arm on the overall performance of the robot is attenuated by reducing the optimisation variables. The effectiveness of the method is evaluated on a Computer Aided Design (CAD) model and the simulations of the whole operation are conducted using MATLAB and SimMechanics.

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Esat, Volkan. "Biomechanical modelling of the whole human spine for dynamic analysis." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7839.

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Developing computational models of the human spine has been a hot topic in biornechanical research for a couple of decades in order to have an understanding of the behaviour of the whole spine and the individual spinal parts under various loading conditions. The objectives of this thesis are to develop a biofidefic multi-body model of the whole human spine especially for dynamic analysis of impact situations, such as frontal impact in a car crash, and to generate finite element (FE) models of the specific spinal parts to investigate causes of injury of the spinal components. As a proposed approach, the predictions of the multi-body model under dynamic impact loading conditions, such as reaction forces at lumbar motion segments, were utilised not only to have a better understanding of the gross kinetics and kinematics of the human spine, but also to constitute the boundary conditions for the finite element models of the selected spinal components. This novel approach provides a versatile, cost effective and powerful tool to analyse the behaviour of the spine under various loading conditions which in turn helps to develop a better understanding of injury mechanisms.

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Lopik, David van. "A computational model of the human head and cervical spine for dynamic impact simulation." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/7643.

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Injury to the human neck is a frequent consequence of automobile accidents and has been a significant public health problem for many years. The term `whiplash' has been used to describe these injuries in which the sudden differential movement between the head and torso leads to abnormal motions within the neck causing damage to its soft tissue components. Although many different theories have been proposed, no definitive answer on the cause of `whiplash' injury has yet been established and the exact mechanisms of injury remain unclear. Biomechanical research is ongoing in the field of impact analysis with many different experimental and computational methods being used to try and determine the mechanisms of injury. Experimental research and mathematically based computer modelling are continually used to study the behaviour of the head and neck, particularly its response to trauma during automobile impacts. The rationale behind the research described in this thesis is that a computational model of the human head and neck, capable of simulating the dynamic response to automobile impacts, could help explain neck injury mechanisms. The objective of the research has been to develop a model that_,, can accurately predict the resulting head-neck motion in response to acceleration impacts of various directions and severities. This thesis presents the development and validation of a three-dimensional computational model of the human head and cervical spine. The novelty of the work is in the detailed representation of the various components of the neck. The model comprises nine rigid bodies with detailed geometry representing the head, seven vertebrae of the neck and the first thoracic vertebra. The rigid bodies are interconnected by spring and damper constraints representing the soft-tissues of the neck. 19 muscle groups are included in the model with the ability to curve around the cervical vertebrae during neck bending. Muscle mechanics are handled by an external application providing both passive and active muscle behaviour. The major findings of the research are: From the analysis of frontal and lateral impacts it is shown that the inclusion of active muscle behaviour is essential in predicting the head-neck response to impact. With passive properties the response of the head-neck model is analogous to the response of cadaveric specimens where the influence of active musculature is absent. Analysis of the local loads in the soft-tissue components of the model during the frontal impact with active musculature revealed a clear peak in force in the majority of ligaments and in the intervertebral discs very early in the impact before any forward rotation of the head had occurred. For the case of rear-end impact simulations it has been shown for the first time that the inclusion of active musculature has little effect on the rotation of the head and neck but significantly alters the internal loading of the soft-tissue components of the neck.

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Okitsu, Yoshitaka. "FABRICATION OF ULTRAFINE GRAINED STEELS WITHOUT SEVERE PLASTIC DEFORMATION AND THEIR APPLICATION TO AUTOMOBILE BODY STRUCTURES." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157630.

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Bartram, Matthew. "Transient tyre modelling for the simulation of drivetrain dynamic response under low-to-zero speed traction manoeuvres." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8489.

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The work presented in this thesis is dedicated to the study of transient tyre dynamics and how these influence the dynamic behaviour of the vehicle and its driveline, with the main focus being on low-to-zero speed manoeuvres such as pull-away events. The bulk of the work focuses on the amalgamation of the hitherto disparate fields of driveline modelling and detailed tyre modelling. Several tyre models are employed and their relative advantages and disadvantages analysed. The observed dynamic behaviour is correlated to the inherent structure of each tyre model in order for the most appropriate for driveline studies to be identified. The main simulation studies are split into two parts: the first comprises a study into isolated driveline dynamics; where the yaw, pitch and roll behaviours of the vehicle body are neglected. A relatively detailed driveline model with an open differential is used with tyre models of increasing complexity with the aim of determining when increased model detail fails to increase the accuracy of the results. The second part is concerned with the study of how the dynamics of the vehicle body and suspension affect tyre model performance and associated effects on the driveline behaviour. For this, the driveline and tyre models are incorporated into a full six degree-of-freedom vehicle model with full suspension effects. Frequency migration on low-μ surfaces is successfully explained via the decoupling of the vehicle and driveline inertias. Frequencies observed in FFT analyses of the simulation results correspond to those obtained through eigen-analysis of appropriately modified state-space models with varying degrees of coupling that reflect the vehicle travelling on uniform low- or split-μ surfaces. The main finding of the thesis is that this decoupling theory can also be applied to high-speed take-off manoeuvres, as it is the position along the tyre slip-force curve that dictates decoupling; i.e. if the curve has saturated. This leads to the effective traction stiffness being zero, which modifies the equations of motion and subsequently the system eigenvalues. A series of measurements are taken in order to verify the findings from the simulation work. Manoeuvres analogous to those simulated are carried out. It is found that only the simulation of split-μ conditions is necessary, as the results from the low-μ test show a similar pattern to those seen on the split-μ surface.

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Strobel, Jens, Jens Sumpf, and Hagen Bankwitz. "Dynamic Studies on a Slide Chain Conveyor System." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-231745.

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In slide chain conveyors vibrations often appear. These cause detrimental effects in conveying process and decrease the durability of chains. To study the vibrations, a multi-body simulation model has been developed, in which rheological elements are used to represent the dynamic effects. A focus was determining material values required for the model. These were identified by hysteresis experiments. Finally, the model was verified by comparing simulation results with measurements in the conveyor system
In Gleitkettenfördersystemen werden häufig Schwingungen der Kette beobachtet, die einen zuverlässigen Förderprozess auf diesen Anlagen beeinträchtigen können. Ziel dieser Arbeit ist die Erforschung dieser Schwingungen mit Hilfe von einem Mehrkörpersimulationsmodell. Zur Abbildung der dynamischen Effekte wurden rheologische Elemente verwendet. Ein Schwerpunkt lag bei der Ermittlung der für das Modell notwendigen Materialkennwerte. Diese wurden mit Hilfe von Hystereseversuchen herausgefunden. Zum Schluss wurde das Modell über einen Abgleich zwischen Simulation und Messung im Fördersystem verifiziert

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Kosaraju, Nikhil Maharshi. "Dynamic Analysis of an Automotive Power Transfer unit : Towards prediction of TE and housing vibrations." Thesis, KTH, Maskinkonstruktion (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259683.

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This work describes the use of Multi-Body Simulation (MBS) to create a virtual prototype of a geared drive called Power transfer unit (PTU). PTU is a subsystem of the all-wheel drive driveline responsible for transfer of power between front and rear axles in an Automobile. The objective of the developing the prototype is to simulate the dynamic behavior of the PTU. Focus is on predicting the gear transmission error(TE) and gearbox housing vibration level. A Hypoid gear set, bearings, tubular shaft and housing are the major components in the PTU. This work is carried out at GKN Automotive which specializes in development of Automotive All wheel drive systems. When developing such geared systems one important characteristic analyzed is the noise and vibration it generates. And for companies like GKN it is desirable to predict these characteristics as early as possible for two reasons, to avoid late design changes and to speed up the product development cycle. To achieve this, a validated virtual model which is computationally efficient is desired. The methodology followed contains of two facets, development of the MBS model and validation of the developed model with physical testing. An integrated MBS-FEM approach is used, an FE modal reduction technique is used to create flexible components with which a virtual prototype is built and simulated in an MBS tool MSC ADAMS c . Gear contact and bearings are defined using an analytical approach which considers the nonlinear stiffness and damping. A dynamic analysis and system level modal analysis is performed to predict the TE, housing vibrations and PTU modal parameters. Experimental modal analysis and physical testing on test rig are performed to measure the actual values of the above predicted outputs. Parameters like damping, contact stiffness of the model are then tuned to achieve correlation. When comparing test and prediction, close correlation is seen in the TE and for housing vibration a similar trend is observed with some deviations. Predicted TE is heavily dependent on gear contact parameters. On the modal parameter comparison, a correlation of five modes and mode shapes below 2500Hz is seen which shows the validity of the MBS model. Parameter studies are performed to study the effect of bearing damping and preload on housing vibrations and TE. It is observed that an optimum value of preload and damping is essential to avoid unnecessary vibrations. In conclusion, the model with some fine tuning of damping parameters can be used for virtual noise and vibration analysis of the PTU.
Detta arbete beskriver anv¨andningen av beräkningsmetoden Multi-Body Simulation (MBS) för att skapa en virtuell prototyp av en vinkelväxel (Power Transfer Unit, PTU ). PTU är ett delsystem för fyrhjulsdrift som har funktionen att överföra kraft mellan fram- och bakaxlar i en bil. Målet med att utveckla modellen är att simulera PTUns dynamiska beteende. Fokus ligger på att beräkna vinkelväxelns transmissionsfel och vibrationsnivåer på växellådans hus. De vikitgaste komponenterna i PTUn är hypoidväxeln med kronhjul och pinjong, röraxel, lager och hus. Detta arbete har utförts på GKN Automotive som är specialiserade på utveckling av drivsystem för fyhjulsdrivna bilar. Ljud och vibrationer är viktiga egenskaper att ta hänsyn till under utvecklingen. För företag som GKN är det önskvärt att kunna beräkna dessa egenskaper så tidigt i projektet av två skäl: dels för att undvika sena konstruktionsförändringar och dels att påskynda produktutvecklingscykeln. För att uppnå detta behövs en validerad virtuell modell som är beräkningseffektiv. Den metod som använts innehåller två delar: utveckling av MBS-modellen och validering av den utvecklade modellen med fysisk testning. En integrerad MBS-FEM -mettod har använts. Det innebär att en FE-modal reduktionsteknik andvänds för att skapa flexibla komponenter med vilka en virtuell prototyp byggs och simuleras i ett MBS-verktyg (MSC ADAMS (c) ). Lager och kuggkontakt i växeln definieras med hjälp av en analytisk metod som beaktar den olinjära styvheten och dämpningen. En dynamisk analys och modalanalys på systemnivå har utförts för att beräkna TE, husvibrationer och PTUns modala parametrar. Experimentell modalanalys och testning i rigg gjorts för att mäta motsvarande värden som har beräknats. Parametrar som dämpning och kontaktstyvhet har sedan justerats för att uppnå korrelation. Vid jämförelse av test och förutsägelse ses en god korrelation i TE och för husvibrationer observeras en liknande trend, med vissa avvikelser. Beräknat TE är starkt beroende på parametrar för kuggkontakten i växeln. Vid jämförelse av modala parametrar ses en god korrelation under 2500 Hz mellan fem moder i mätning och beräkning vad gäller frekvens och modform, vilket visar MBS-modellens giltighet. Parameterstudier har utförts för att studera effekten av lagerdämpning och förbelastning på TE och husvibrationer. Ett optimalt värde på förbelastning och dämpning är viktigt för att undvika onödiga vibrationer. Sammanfattningsvis kan modellen med viss finjustering av dämpningsparametrar användas i virtuell ljud- och vibrationsanalys av PTU.

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Rampersadh, Gevashkar. "Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29352.

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A new class of unmanned marine research vessels makes use of wave propulsion to minimise energy requirements during voyages. Existing models of these hybrid sea-surface and underwater craft have not considered if the platform’s interaction with the immediate surrounding sea could be incorporated to allow for more accurate navigation and path planning. To this end a detailed three-dimensional model of one such vessel, the Liquid Robotics’ Wave Glider, has been developed in this study. The multi-body system is described using DenavitHartenberg parametrisation and a Lagrangian approach is used to generate the equations of motion for the body. Physical dimensions are derived from platform measurements and from the product specification sheet, hydrodynamic factors are derived from a SolidWorks model of the system, and added mass components are determined from empirical data. Finally, the dynamic model is verified for a given sea state and multiple sea states are tested to investigate the effect on the model’s performance. The developed Wave Glider model is shown to have a realistic response when hydrodynamic factors, added mass and hydrodynamic damping forces, are included and to sea states in terms of the hydrostatic restorative response. The wave-driven propulsion provided by the hydrofoils is shown to have dependence on the sea state by running the model in an open-loop simulation. Following the model validation, a control system is developed for the Wave Glider model to allow yaw attitude control of the glider using the controllable glider rudder input. The control system is generated making use of quantitative feedback theory (QFT) methods to provide robust control for the under-actuated system. The control scheme is shown to provide suitable performance for sea states that result in variable glider velocities. The model’s performance, in terms of the average velocity, is shown to have dependence on the direction of the sea state by running the model in an open-loop simulation for multiple sea states with sinusoidal waves approaching the Wave Glider model from different directions.

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Ramachandran, Praveen. "Modelling and Dynamic Simulation of Tracked Forwarder in Adams ATV Module." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-182803.

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Swedish forest industry is relying on the cut-to-length method for logging and there has always been a constant quest to make it more efficient and sustainable. Reduction of forest soil damage and operator vibration dosages are crucial steps that could facilitate meeting the above stated targets. In this context Skogforsk- The Swedish Forest Research Institute has decided to explore the potential usage of caterpillar tracks on conventional wheeled forwarders. An efficient way to perform this study is to use multi body simulations to evaluate the performance of the tracked forwarder concept over different terrains. This thesis work aims to model and simulate a tracked forwarder in Adams ATV module. As part of the thesis a conventional wheeled forwarder was selected and a track unit was conceptualised to fit it. The concept was modelled and simulate with Adams ATV for various ground conditions. An effort was also made to identify the performance parameters required to improve traction, handling, and ride performance. Based on this some results were selected and studied and inferences were made. The results from the thesis work could provide a guideline on the methodology to be followed and a a deliverable is also a multi-body dynamics model for future design research.
Svensk skogsindustri jobbar efter kortvirkesmetoden för trädavverkning. Det finns en strävan efter att göra denna metod mer effektiv och samtidigt mer ekologiskt hållbar, exempelvis en minskad markpåverkan reduktion av de helkroppsvibrationer som operatören utsätts för. Motivet till detta examensarbete är att utforska möjligheten att ersätta dagens hjulbaserade skogsmaskiner med banddrivna. Det överordnade syftet för examensarbetet är att utveckla en modelleringsmetodik för dynamiska systemsimuleringar. Metoden för detta är att modellera och simulera en banddriven skotare med Adams ATV-modul och att beskriva ett rekommenderat tillvägagångssätt och möjliga resultat. Som en del av arbetet har en traditionell skotare valts och en konceptuell bandenhet har skapats och anpassats för att passa till skogsmaskinen. Konceptet modellerades och simulerades med Adams ATV för olika markunderlag. Ytterligare arbete lades på att identifiera de parametrar som är viktiga för grepp, fordonskontroll och framkomlighet. Baserat på några av resultaten valdes några för en fördjupad studie. Resultatet från examensarbetet kan ge riktlinjer för val av lämplig metodik för denna typ av prestandastudier. En konkret leverabel från projektet är också en dynamisk flerkroppsmodell, som kan utgöra en bas för fortsatta konstruktions- och prestandastudier.

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18

Meymand, Sajjad Zeinoddini. "State of the Art Roller Rig for Precise Evaluation of Wheel-Rail Contact Mechanics and Dynamics." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/64920.

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The focus of this study is on the development of a state-of-the-art single-wheel roller rig for studying contact mechanics and dynamics in railroad applications. The use of indoor-based simulation tools has become a mainstay in vehicle testing for the automotive and railroad industries. In contrast to field-testing, roller rigs offer a controlled laboratory environment that can provide a successful path for obtaining data on the mechanics and dynamics of railway systems for a variety of operating conditions. The idea to develop a laboratory test rig started from the observation that there is a need for better-developed testing fixtures capable of accurately explaining the complex physics of wheel-rail contact toward designing faster, safer, and more efficient railway systems. A review of current roller rigs indicated that many desired functional requirements for studying contact mechanics currently are not available. Thus, the Virginia Tech Railway Technologies Laboratory (RTL) has embarked on a mission to develop a state-of-the-art testing facility that will allow experimental testing of contact mechanics in a dynamic, controlled, and consistent manner. VT roller rig will allow for closely replicating the boundary conditions of railroad wheel-rail contact via actively controlling all the wheel-rail interface degrees of freedom: cant angle, angle of attack, and lateral displacement. Two sophisticated independent drivelines are configured to precisely control the rotational speed of the wheels, and therefore their relative slip or creepage. A novel force measurement system, suitable for steel on steel contact, is configured to precisely measure the contact forces and moments at the contact patch. The control architecture is developed based on the SynqNet data acquisition system offered by Kollmorgen, the motors supplier. SynqNet provides a unified communication protocol between actuators, drives, and data acquisition system, hence eliminating data conversion among them. Various design analysis indicates that the rig successfully meets the set requirements: additional accuracy in measurements, and better control on the design of experiments. The test results show that the rig is capable of conducting various contact mechanics studies aimed for advancing the existing art. Beyond developing the experimental testing fixture for studying contact mechanics, this study provides a comprehensive review of the contact models. It discusses the simplifying assumptions for developing the models, compares the models functionality, and highlights the open areas that require further experimental and theoretical research. In addition, a multi-body dynamic model of the entire rig, using software package SIMPACK, is developed for conducting modal analysis of the rig and evaluating the performance of the rig's components. A MATLAB routine is also developed that provides a benchmark for developing creep curves from measurements of the rig and comparing them with existing creep curves.
Ph. D.

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19

Aravindababu, Sumanth Ram. "Investigation of sources of wheel-rail impact force deviation through dynamic simulations." Thesis, KTH, Fordonsdynamik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302783.

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Due to the increase in demand on freight transportation it becomes necessary to avoid delays to ensure that the goods reach its destination on time. The main factors causing disturbances in the traffic on the mainline is the breakdown of vehicles mainly due to damaged wheels. The damaged wheels are identified through the wheel-rail impact force measurements provided by the wheel impact load detectors (WILD). This calls for the optimal schedule of maintenance of wheelsets and wagons in general. During the maintenance, the officials manually check for defective wheels and the exchange of wheelsets is performed based on the type of damage. The classification of wheel damages plays a vital role in providing ease of damage identification and insights to deduce a strategy for wheelset exchange. In this study, an attempt to classify the damaged wheelsets is done by analysing the wheel-rail impact force data from the wayside detectors. The data from the detectors are acquired from PredgeAB, a Luleå based startup pioneering in providing decision support on optimal maintenance schedules and predictive maintenance of rail wheels. Through their detection and prediction solutions it was observed that of all the wheels marked as damaged by the detectors 10% were undamaged. The source of the deviation in the impact force readings could help Predge make better estimations in damage detection and prediction. In this study, the sources contributing to the deviation is studied using multi-body simulations in GENSYS. A new method for modelling wheel damage is developed to overcome the shortcomings of the software. The findings of this study can then be used appropriately to make classifications of wheel damages.
På grund av den ökade efterfrågan på godstransporter är det nödvändigt attundvika förseningar för att säkerställa att varorna når sin destination i tid. Deviktigaste faktorerna som orsakar störningar i trafiken på huvudlinjen är stopp ispår av fordon, främst på grund av skadade hjul. De skadade hjulen identifierasmed hjälp av mätningar av slagkraft mellan hjul och spår som tillhandahållsav hjulbelastningsdetektorer (WILD). Detta kräver ett optimerat schema förunderhåll av hjulsatser och vagnar i allmänhet. Under underhållet kontrollerartjänstemännen manuellt för defekta hjul och utbytet av hjulsatser utförs baserat på typen av skada. Klassificeringen av hjulskador spelar en viktig roll närdet gäller att underlätta identifiering av skador och ge insikt för att bedöma enstrategi för hjulbyte. I den här studien görs ett försök att klassificera de skadade hjulsatserna genom att analysera data från slagkraften mellan spår ochhjul från detektorer. Uppgifterna från detektorerna hämtas från PredgeAB, enLuleå-baserad uppstartsbolag som är pionjärer för att ge beslutsstöd om optimala underhållsscheman och prediktivt underhåll av järnvägshjul. Genom sinadetekterings- och prediktiva lösningar observerades att 10% av alla hjul märktasom skadade av detektorerna var oskadade. Källan till avvikelsen i slagkraftavläsningarna kan hjälpa Predge att göra bättre uppskattningar när det gällerupptäckning och förutsägelse av skador. I den här studien studeras de källorsom bidrar till avvikelsen med simuleringar av flera kroppar i GENSYS. En nymetod för modellering av hjulskador har utvecklats för att övervinna programvarans brister. Resultaten av denna studie skulle kunna användas på lämpligtsätt för att göra klassificeringar av hjulskador.

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Karis, Tomas. "Correlation between Track Irregularities and Vehicle Dynamic Response Based on Measurements and Simulations." Licentiate thesis, KTH, Farkost och flyg, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-228056.

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Deviations from the design track geometry are called track irregularities, which are a main excitation mechanism in the track–vehicle dynamic system, and very important to monitor and maintain to have trac on a line run safely and comfortably. Especially during vehicle acceptance testing, it is important that a new vehicle behaves close to design predictions and within limit values, thus it is important to be able to describe track irregularities in a consistent way. There are several methods which quantify the eects track irregularities have on a vehicle while running along the track. Most common is analyse standard deviations and percentiles and maximum values over sections with pre-defined length. However, these quantities do not correlate well with the vehicle dynamic response, e.g. two track sections with similar maxima and standard deviations can result in very dierent response of the vehicle. To improve the correlation between track irregularities and vehicle re- sponse measures, it is recommended by past research to use multiple regres- sion analysis to take e.g. vehicle speed and track curvature into account as well. Other methods range from derivatives of track irregularities, via trans- fer functions and vehicle filters to neural networks. Common for all these methods are that there is either still slight inconsistencies in the results or that they are tailored for certain vehicle types on specific lines. As a result, the preferred method to evaluate track irregularities is still to use standard deviations. In this thesis, data from three vehicles in two measurement campaigns is evaluated using a single degree of freedom model as inspiration to break down the path from track to vehicle into several steps. A weak link in these steps is identified, which shows significantly lower correlation coecients than the other steps. The weak link is the step from vertical track irregularity second spatial derivative to vertical axle box acceleration divided by the squared vehicle speed. A variable wavelength range Dx is introduced, as an alternative to the common D1 (3–25 m), D2 (25–70 m) and D3 (70–150 m) wavelength ranges. Its wavelength range corresponds to the vehicle response band-pass filter frequencies and is thus speed dependent. Simulations are also carried out to investigate the weak link and for the possibility to vary parameters that cannot be changed during on-track mea- surements. A multi-body system model of the passenger coach Bim 547.5 is used, together with recorded track data and vehicle speed from the on-track measurements. The varied parameters have rather low sensitivity and aect results to a small extent. Most impact has the randomly varying vertical track stiness which aects the vertical wheel–rail forces and axle box accelerations. In future work, it should be explored if it is possible – and in such case how – to separate the eects of varying track stiness from the track irreg- ularities. This to better understand when a vehicle response is linked more to the track irregularities or to the track flexibility. The weak link identified in the steps from track to vehicle should also be further explored, perhaps by extending the underlying model or evaluate a dierent set of measurements.
Spårlägesfel är avvikelser från den nominella spårgeometrin. De är en vik- tig excitationsmekanism i det dynamiska system som bana och fordon utgör och är viktiga att övervaka och åtgärda för att trafiken ska kunna flyta sä- kert och komfortabelt. Eftersom det vid mätningar för typgodkännande av fordon är viktigt att fordonet beter sig som förväntat och inom gränsvärden, är det viktigt att kunna beskriva spårlägesfel på ett sätt som är konsekvent och motsvarar hur fordonet ”känner av” dem. Det finns ett flertal olika metoder som kvantifierar de eekter spårläges- fel har på ett fordon som rör sig längs ett spår. Vanligast är att använda standardavvikelser, percentiler och maxvärden från spårsektioner med för- definierad längd. Dessa storheter korrelerar dock inte väl med den dynamiska fordonsresponsen, till exempel kan två spårsektioner med liknande maxvärden och standardavvikelse resultera i väldigt olika fordonsrespons. För att förbättra korrelationen mellan storheter för spårlägesfel och for- donsrespons rekommenderar tidigare forskning att använda multipel regres- sionsanalys för att även ta hänsyn till till exempel fordonets hastighet eller spårets kurvatur. Det finns flera alternativa metoder, till exempel derivator av spårlägesfel, överföringsfunktioner och fordonsfilter eller neurala nätverk. Generellt ger dock dessa metoder antingen fortfarande en viss osäkerhet i resultaten, eller så är de anpassade för vissa fordonstyper på enstaka järn- vägslinjer. Sammantaget är resultatet att den metod som föredras för att utvärdera spårlägesfel, fortfarande baseras på standardavvikelser. I den här avhandlingen används en enfrihetsgradsmodell som inspiration för att bryta ner excitationsvägen från spår till fordon i ett antal steg, som sedan undersöks genom att utvärdera mätdata från tre fordon i två forsk- ningsprojekt. En svag länk bland stegen identifieras, vilken visar signifikant lägre korrelationsvärde än övriga steg. Den svaga länken är steget från spatial andraderivata av spårlägesfel till axelboxacceleration dividerat med fordons- hastigheten i kvadrat. Ett variabelt våglängdsområde Dx introduceras som ett alternativ till de vanligt förekommande D1 (3–25 m), D2 (25–70 m) och D3 (70–150 m). Det variabla våglängdsområdet motsvarar de frekvenser som används för utvärdering av fordonsrespons och är därmed hastighetsberoende. Vidare används simuleringar för att undersöka den svaga länken och för möjligheten till parametervariationer. En flerkroppsmodell (MBS-modell) av passagerarvagnen Bim 547.5 används tillsammans med uppmätta data för spår och fordonshastighet. De parametrar som varieras visar sig ha låg käns- lighet och påverkar resultaten i liten utsträckning. Störst inverkan har den slumpmässigt varierande vertikala spårstyvheten, vilken påverkar de vertikala hjul–rälkrafterna och axelboxaccelerationerna. Fortsatt forskning bör undersöka om det är möjligt att – och i så fall hur – separera eekten av varierande spårstyvhet och spårlägesfel. Detta kan ge bättre förståelse för om fordonsrespons kopplar mer till spårlägesfelen eller till spårflexibiliteten. Den svaga länken som identifierats bör också undersö- kas ytterligare, förslagsvis genom att utöka den bakomliggande modellen eller analysera annan mätdata.

QC 20180517

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21

Feng, Chih-Liang. "Heavy truck dynamics modeling using multi-body dynamics." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1295551522.

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22

Miri, Amin. "Mitigating severity of longitudinal interaction of rail-track-bridge system in transition zones for safer trains." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/236242/1/Amin%2BMiri%2BThesis%282%29.pdf.

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Extreme heat and temperature fluctuation in Queensland result in buckling of railway tracks which jeopardize the safety of train operation and cost huge sums to repair. This thesis carried out an elaborate investigation on the issue of track buckling and provided several approaches to mitigate the risks of track buckling to enable safer trains and lower maintenance costs for railway operators in Australia.

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23

Denni, Martin. "Dynamic behaviour of cylindrical roller bearing working in a centrifugal field for planetary gearbox applications." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI096.

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Dans un objectif permanent de réduction de consommation des turboréacteurs, les constructeurs aéronautiques souhaitent atteindre de meilleurs rendements en augmentant la vitesse de l'ensemble compresseur-turbine. Afin de limiter la vitesse de la soufflante, un étage de réduction épicycloïdal doit être inséré entre la soufflante et le compresseur. Du fait de leur bonne tenue en cas de défaillance du circuit de lubrification, les roulements sont souvent privilégiés aux paliers hydrodynamiques pour les applications aéronautiques. Cependant, dans le cas des trains épicycloïdal, les roulements sont soumis à des forces centrifuges importantes qui sont la cause de pertes de puissances significatives ainsi que de la fatigue prématurée des cages ce qui peut provoquer la destruction du roulement. Ce travail de thèse consiste en le développement d'un modèle numérique permettant de comprendre le comportement dynamique d'un roulement à rouleaux cylindriques fonctionnant en champ centrifuge. Pour cela, la méthode de dynamique multi-corps est utilisée, couplée à des modèles de contact semi-analytiques tenant compte des différents régimes de lubrification rencontrés dans le roulement. De plus, un modèle élément finis est développé pour prendre en compte la flexibilité de la bague extérieure qui peut affecter la dynamique du roulement. Les résultats sont présentés pour une application classique de train épicycloïdal en termes de force, vitesse et perte de puissance. De forts impacts entre les rouleaux et la cage sont observés et les mécanismes responsables des importantes pertes de puissances et de la fatigue de cage sont expliqués. L'influence des hypothèses principales de modélisation est présentée. Enfin, une étude de l'influence des différents paramètres sur l'amplitude des forces et sur la taille et la position de la zone de chargement du roulement est réalisée
With the constant aim of reducing the turbofan consumption, aircraft manufacturers try to reach higher efficiency by increasing the compressor-turbine speed. In order to limit the fan speed, a planetary gearbox is introduced between the fan and the compressor. Because of their good oil-off performance, roller bearings are often preferred over hydrodynamic bearings for aircraft applications. However, in the case of planetary gearboxes, the roller bearings are submitted to severe centrifugal forces which cause significant power losses and premature cage fatigue that may lead to overall bearing failure. The present work consists in the development of a numerical model for the understanding of the dynamic behaviour of a cylindrical roller bearing working in a centrifugal field. Multi-body dynamics is used, coupled with semi-analytical contact models accounting for the different lubrication regimes encountered in the bearing. In addition, a finite element model is developed to account for the outer ring flexibility that may affect the bearing dynamics. Results are presented for a typical planetary gearbox application in terms of force, speed and power losses. Severe roller/cage impacts are observed and the mechanisms that cause the high power losses and the cage fatigue are explained. The influence of the main model hypothesis is presented. Finally, a study of the influence of the different parameters on the force amplitude and the bearing loaded zone shape and position is performed

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Kepler, Jr Michael Eugene. "Dynamics of a Small Autonomous Underwater Vehicle That Tows a Large Payload." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84915.

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This thesis presents the derivation of the dynamic model of an autonomous underwater vehicle that tows a large payload. Our analysis is motivated by the fact that the payload is so large that it cannot be modeled by simply appending its dynamics to the dynamics of the autonomous underwater vehicle. Hence, the coupling between the vehicle and payload must be fully modeled. Furthermore, several approximation techniques based on analytic and empirical formulations are investigated for computing the hydrodynamic coefficients of the vehicle. Efficacy and limitations of the approximation techniques are assessed by comparison with hydrodynamic coefficients that are estimated using high-fidelity computational fluid dynamics simulations.
Master of Science

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Keshmiri, Mehdi. "Dynamics and control of multi-body tethered satellite systems." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28796.

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In this thesis, dynamics and control of multi-body tethered satellite systems are investigated. First a dynamical model is developed that takes into account the three dimensional librational motion of the system as well as the nonlinear vibrations of the tethers, both in longitudinal and transverse directions. The assumed modes method is used to discretize the continuous tethers. Using Lagrange's equations, splitting the vector of generalized coordinates to a set of subvectors, where each subvector corresponds to a specific tether, a set of nonlinear ordinary differential equations governing the motion of the system is obtained in the explicit analytical form. A fourth order strain energy expression is used in the formulation to allow the possibility of moderately large deformation of the tethers. The equations are applicable whether the length of the tethers are constant (station-keeping phase) or changing with time (deployment and retrieval phases). They are transformed into vector form for simulation purposes.
Among the external forces, the aerodynamic forces and their effects on the dynamics and stability of the system are given more attention. The free molecular flow model is used to calculate the aerodynamic forces resulting from the material damping of the tethers are considered in this investigation. These forces, which are very difficult to model accurately, are modelled using a viscous damping model.
Equilibrium configurations of the system, as special solutions of the equations of motion, in the absence or presence of the aerodynamic forces, are studied in more detail. A closed form solution to the static equilibrium equations is obtained when there is no external force acting on the system other than the gravitational force. The set of nonlinear equations of motion is then linearized analytically about a particular equilibrium configuration for stability and eigenvalue analysis. The natural frequencies of some single-tether as well as multi-tether systems are calculated using these linearized equations.
Stability of a single-tether system in low orbit missions is investigated, ignoring the aerodynamic forces on the main-satellite as well as on the tether. Assuming a particular geometrical configuration for the subsatellite and using the linearized equations, the effect of the aerodynamic forces, particularly aerodynamic lift, on the stability of the system as well as the equilibrium configuration of the system is examined through the eigenvalue analysis. This analysis is then extended to multi-body systems.
Finally the problem of controlling the nonlinear system through the application of Lyapunov's stability theory is examined for multi-body tethered systems, ignoring the transverse oscillations of the tethers. Initially, based on the Hamiltonian of the system, a Lyapunov function is introduced for a system with massless and rigid tethers. It leads to a linear tension control law. When the mass of the tethers is taken into account the Lyapunov function is modified and a new tension control law is developed which is no longer linear. With the assumption that the longitudinal oscillations of the tethers are small compared to the length of the tethers, a Lyapunov functions is constructed for systems with elastic tethers. At the end, a hybrid control law is examined to improve the performance of the controlled system.

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Laperle, Christopher Michael. "Experimental studies of multi-body dissociative charge exchange dynamics /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3153693.

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Fratello, John David. "Multi-body Dynamics Simulation and Analysis of Wave-adaptive Modular Vessels." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76787.

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Catamarans provide vast deck space, high thrust efficiency, and excellent transverse stability, however, in rough conditions they can be susceptible to deck slamming from head seas or bow diving in following seas and a pitch-roll coupling effect that can lead to uncomfortable corkscrew motion under bow-quartering seas. A new class of catamaran called Wave-Adaptive Modular Vessels (WAM-V™) aims to help mitigate oceanic input from the cabin by allowing for the relative motion of components not common to classic catamaran design. This thesis presents a set of multi-body dynamics simulation models created for two active WAM-Vs™ along with analysis on their suspension characteristics. Both models provide conclusive and realistic results, with the final model being validated against on-water testing data from a 12-ft unmanned prototype WAM-V. The first of these simulations serves primarily as a tool to evaluate WAM-V™ response characteristics with respect to a variety of parametric variations. The modeling environment is highlighted along with details of the parametric simulation and how it was created. The results fall in line with our expectations and are presented along with analysis of the sensitivity of each parameter at three longitudinal locations. The final simulation attempts to model the response of a 12-ft unmanned surface vessel (USV) prototype of the WAM-V™ configuration. Testing data is collected, processed, and applied to the model for validation of its prediction accuracy. The results of the sea tests indicate that the simulation model performs well in predicting USV motions at sea. Future considerations for testing WAM-Vs™ can include changes in suspension and mass parameters as well as limiting particular degrees-of-freedom by making their joints rigid.
Master of Science

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28

Metzger, Melodie F. "Evaluation of spinal reconstructive surgeries using multi-body system dynamics." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3390062.

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Thesis (Ph.D.)--University of California, San Francisco with the University of California, Berkeley, 2009.
Source: Dissertation Abstracts International, Volume: 71-02, Section: B, page: . Adviser: Jeffrey C. Lotz.

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29

Kim, Sun-Wook. "Contact dynamics and force control of flexible multi-body systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0035/NQ64588.pdf.

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Kim, Sun-Wook 1966. "Contact dynamics and force control of flexible multi-body systems." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36622.

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A detailed modelling of contact dynamics involving general flexible multi-body systems of arbitrary kinematic architecture is considered. The components undergoing direct contact (e.g., the end-effector of a manipulator and a satellite) are modelled using the finite element method and the Lagrange multiplier technique. Special attention is paid to dynamic fidelity of contact dynamics. Contact geometric constraints and corresponding contact forces are analysed and incorporated into the dynamical equations. This model takes into account structural deformations and oscillations, friction, time-varying contact area, and repeated contact/impact. Multi-body systems, on the other hand, are handled by a modified Euler-Lagrange method based on the Natural Orthogonal Complement (NOC). Thus, the system dynamics is composed of a set of differential equations (either multi-body formulations or finite element nodal displacement formulations) subjected to sets of algebraic equations expressing kinematic or contact constraints. A systematic procedure for solving this system of equations is formulated with special emphasis on computational efficiency.
This dynamic model is then used to design a composite controller which must simultaneously achieve three goals: (1) trajectory tracking, (2) force control, and (3) stabilization of the flexible degrees of freedom of the multibody system. The singular perturbation method is used to obtain two reduced order models. Subsequently, the slow subsystem is used to design a simultaneous position/force controller based on impedance control, where an optimization method is incorporated to accommodate manipulator redundancy. The fast subsystem is used to design a Linear Quadratic Regulator (LQR) to suppress structural vibrations.
A simulation environment is developed based on the above procedures and formulations for the planar case. It is used to perform dynamic and control simulations of a variety of contact scenarios involving multi-body systems. A comparative study of the results indicates that a detailed contact dynamics model may be essential for a realistic simulation of contact/impact, capture, and force control operations.

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31

Pagnozzi, Daniele. "On the dynamics of rigid multi-body systems in orbit." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26002.

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A critical factor for the success of space missions is the implementation of an appropriate spacecraft attitude control system. For multi-body space systems, the mechanical couplings have significant effects on the attitude dynamics. These effects, added to the high performance requirements and the number of strict constraints that, in general, space systems have to satisfy, make mission design very challenging. This calls for research to address these challenges. Dynamical systems analysis benefits system and control design by providing a quantity of information on the systems' natural behaviour. This thesis investigates the natural attitude dynamics of multi-rigid-body space systems and gains an insight into the nonlinear dynamics in order to develop efficient control techniques that exploit them. In addition this thesis aims to investigate the usefulness of dynamical systems tools in this area of application. To this end, the dynamics of the free single asymmetric rigid spacecraft, the two-body spacecraft in orbit, the threebody spacecraft in orbit and the generic N-body spacecraft are studied. Integrability of the single rigid body problem is used to derive a form of the well-known solution different from the classical and more suitable for aerospace applications. Hamiltonian and Lagrangian formalisms are used in the few-body problems where equilibria are identified and their nonlinear stability is addressed. Furthermore, the behaviour both in the neighborhood and far from the equilibria is examined, gaining an insight into the global nonlinear dynamics. Finally, the Newton-Euler formulation is employed to describe an N-body system and the problem of the dynamical coupling reduction, relevant for space manipulators, is addressed and a feedback controller is designed.

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Aghaei, Shayan. "Acoustic Radiation Of An Automotive Component Using Multi-Body Dynamics." Thesis, KTH, Fordonsdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-288710.

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An important facet of creating high-quality vehicles is to create components that are quiet and smooth under operation. In reality, however, it is challenging to measure the sound that some automotive components make under load because it requires specialist facilities and equipment which are expensive to acquire. Furthermore, the motors used in testbeds drown out the noise emitted from much quieter components, such as a Power Transfer Unit (PTU). This thesis aims to solve these issues by outlining the steps required to virtually estimate the acoustic radiation of a PTU using the Transmission Error (TE) as the input excitation via multi-body dynamics (MBD). MBD is used to estimate the housing vibrations, which can then be coupled with an acoustic tool to create a radiation analysis. Thus, creating a viable method to measure the acoustic performance without incurring significant expenses. Furthermore, it enables noise and vibration analyses to be incorporated more easily into the design stage. This thesis analysed the sound radiated due to gear whine which arises due to the TE and occurs at the gear mesh frequency and its multiples. The simulations highlighted that the TE can be accurately predicted using the methods outlined in this thesis. Similarly, the method can reliably obtain the vibrations of the housing. The results from this analysis show that at 2000 rpm the PTU was sensitive to vibrations at 500, 1000 and 1500 Hz, the largest amplitude being at 1000 Hz. Furthermore, the Sound Power Level (SWL) was proportional to the vibration amplitudes in the system. Analytical calculations were conducted to verify the methods and showed a strong correlation. However, it was concluded that experiments are required to further verify the findings in this thesis.
En viktig aspekt i att skapa fordon av hög kvalitet är att skapa komponenter som är tysta och smidiga under drift. I verkligheten är det dock svårt att mäta ljudet som vissa fordonskompo- nenter ger under belastning eftersom det kräver specialanläggningar och utrustning, vilket är dyrt att skaffa. Dessutom maskerar motorerna som används i testbäddar ut bullret från mycket tystare komponenter, till exempel en kraftöverföringsenhet (PTU). Detta examensar- bete syftar till att lösa dessa problem genom att beskriva de steg som krävs för att virtuellt uppskatta den akustiska strålningen av en PTU med hjälp av transmissionsfelet (TE) som ingångsexcitation via flerkroppsdynamik (multi-body dynamics, MBD). MBD används för att uppskatta kåpans vibrationer, som sedan kan kopplas till ett akustiskt verktyg för att skapa en ljudutstrålningsanalys. Således skapas en genomförbar metod för att mäta den akustiska pre- standan utan att medföra betydande kostnader. Dessutom möjliggör det att lättare integrera ljud- och vibrationsanalyser i designfasen. Detta examensarbete analyserade ljudet som utstrålats på grund av kugghjulsljud, som uppstår på grund av TE och uppträder vid kuggingreppsfrekvensen och dess multiplar. Simuleringarna belyste att TE kan förutsägas exakt med de metoder som beskrivs i detta examensarbete. På samma sätt kan metoden på ett tillförlitligt sätt uppnå kåpans vibrationer. Resultaten från denna analys visar att vid 2000 rpm var PTU känslig för vibrationer vid 500, 1000 och 1500 Hz, den största amplituden var vid 1000 Hz. Dessutom var ljudeffektsnivån (SWL) proportionell mot vibrationsamplituderna i systemet. Analytiska beräkningar genomfördes för att verifiera metoderna och visade en stark korrelation. Dock drogs slutsatsen att experiment krävs för att ytterligare verifiera resultaten i detta arbete.

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Nordberg, Anders. "Simulation of a complete truck and trailer assembly : Multi body dynamics." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67401.

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Quadrelli, Bruno Marco. "Modelling, dynamics analysis and control of a multi-body space platform." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/39603.

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Clements, Todd Glenn. "Multi-body dissociative photodetachment dynamics of small molecular and cluster anions /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3061625.

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Vinayak, Harsh. "Multi-body Dynamics and Modal Analysis Approaches for Multi-mesh Transmissions with Compliant Gear Bodies." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392059093.

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Budhiraja, Rohan. "Multi-body Locomotion : Problem Structure and Efficient Resolution." Thesis, Toulouse, INSA, 2019. http://www.theses.fr/2019ISAT0036.

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Le problème de locomotion en robotique s'écrit généralement comme un problème d'optimisation de grande taille. Ce problème présente de nombreuses propriétés indésirables, telles qu'une grande dimensionnalité, des fonctions de coûts non-linéaires et non-convexes, des contraintes non-linéaires, etc. Ces caractéristiques diverses rendent larésolution directe difficile. Une approche classique consiste à simplifier l'optimisation numérique en résolvant desmodèles réduits, construits de manière heuristiques. En conséquence, ces modèles ont un domaine de validité réduit et sont difficiles à étendre. Notre travail explore une approche qui tente de résoudre ce problème de locomotion général, tout en exploitant pleinement sa structure pour obtention d'une solution efficace et réalisable. Notre objectif est de fournir une résolution efficace grâce à l'utilisation appropriée de la structure du problème. Pour cela, nous avons généralisé l'utilisation des modèles réduits classiques en locomotion dans une formulation qui permet de résoudre exactement leproblème initial. Notre contribution consiste en une méthode pour la génération de mouvements dynamiques pour le corps complet de l'humanoïde, par l'utilisation de méthode de descente alternée. Le problème complet est séparé en (i) sa partie centroidale, fortement contrainte et instable et résolue par un SQP à tir multiple, et (ii) sa partie lagrangienne, plusstable mais de grande dimension, résolue par Programmation Dynamique Différentielle (DDP) afin d'exploiter la parcimonie du problème. Une implémentation efficace du DDP 1 permet d'obtenir des performances permettant la mise en oeuvres! ur le robot réel, et une utilisation des contraintes de faisabilité ("proxy") permet d'assurer la faisabilité des modèlesréduits. Nos concepts ont été validés empiriquement en calculant et appliquants différents mouvements dynamiques pour le robot humanoïde HRP-2
The locomotion problem in robotics is usually written as a large optimization problem. This problem has many undesirable properties, such as large dimensionality, non-linear and non-convex cos! functions, nonlinear constraints, and so on. These diverse features make direct resolution difficult. A classic approach is to simplify numerical optimization by solving reduced models, built heuristically. As a result, these models have a reduced area of validity and are difficult to extend. Our work explores an approach thal attempts to solve this problem of general locomotion, while fully exploiting itsstructure to obtain an effective and feasible solution. Our goal is to provide effective resolution through the proper use of the problem structure. For this, we have generalized the use of traditional models in locomotion in a formulation th at can solve exactly the initial problem. Our contribution consists of a method for the generation of dynamic movements forthe whole body of the humanoid, by the use of alternating direction method of multipliers. The complete problem is separated into (i) its centroidal part, which is highly constrained and unstable, and is solved by a multiple-shooting SQP, and (ii) its Lagrangian part, which is more stable but larger, and is solved by Differentiai Dynamic Programming (DDP). An efficient implementation of the DDP makes it possible to obtain performances allowing the implementation on the real robot, and a use of the feasibility const! raints ("proxy") makes it possible to en sure the feasibility of the reduced models.Our concepts have been validated empirically by calculating and applying different dynamic motions for the humanoid robot HRP-2, and to the robot Pyrene in simulation

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Monshi, Nasrollah. "Three-dimensional librational dynamics and control of multi-body tethered satellite systems." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61311.

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The first analytical method that is used for the development of reel rate laws is the Liapunov's second method. In this work it is shown that the Hamiltonian can be used as a Liapunov function. A reel rate law is devised that stabilizes the in-plane and out-of-plane librations at the same time, for two-body systems. However, since the resulting motion has some deficiencies, this reel rate law is not extended to multi-body systems.
For overcoming these deficiencies, two new reel rate laws are proposed and their performances are examined through the energy dissipation approach together with the averaging method. The resulting motions with all the reel rate laws, including the one from Liapunov approach, are limit cycle oscillations. The reel rate laws obtained from the energy dissipation approach perform efficient retrievals with sufficiently small out-of-plane limit cycle amplitudes. These reel rate laws are extended to multi-body systems. For multi-body systems a station-keeping stage is added that brings the system to a final desired configuration. An analysis on the effects of different parameters and gains on the resulting motion has also been performed. (Abstract shortened by UMI.)

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Brown, Sean M. "Determination of Human Powered Helicopter Stability Characteristics using Multi-Body System Simulation Techniques." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/874.

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Multi-Body System Simulation combined with System Identification was developed as a method for determining the stability characteristics of a human powered helicopter(HPH) configurations. HPH stability remains a key component for meeting competition requirements, but has not been properly treated. Traditional helicopter dynamic analysis is not suited to the HPH due to its low rotation speeds and light weight. Multi-Body System Simulation is able to generate dynamic response data for any HPH configuration. System identification and linear stability theory are used to determine the stability characteristics from the dynamic response. This thesis focuses on the method development and doesn't present any HPH analysis results.

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LI, FANG. "CONSTRAINED MULTI-BODY DYNAMICS METHOD TO STUDY MUSCULOSKELETAL DISORDERS DUE TO HUMAN VIBRATION." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1180644848.

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Tobiáš, Martin. "Analýza měřených dynamických stavů motocyklů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400514.

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This thesis, within a long-term project at the Institute of automotive engineering at FME BUT, aspires to prepare a motorcycle for analysis of its dynamic riding behavior. A multi-body model of a motorcycle is created based on the measured parameters and a system for measuring driving conditions is designed. The necessary motorcycle parameters were measured using a 3D scanner and through experiments aided by computer technology and CAD software. This laid the foundation for the follow-up research and development work.

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Rajgor, Dipen. "Characterisation of the multi-isomeric protein nesprin-1 in p-body and mRNA dynamics." Thesis, King's College London (University of London), 2013. https://kclpure.kcl.ac.uk/portal/en/theses/characterisation-of-the-multiisomeric-protein-nesprin1-in-pbody-and-mrna-dynamics(aa49c0e2-15fb-4a02-aa88-8fca5575b892).html.

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Nuclear envelope spectrin repeat proteins, or Nesprins, are a novel family of nuclear and cytoskeletal proteins with rapidly expanding roles as intracellular scaffolds and linkers. Nesprins are characterized by a central spectrin repeat (SR) rod domain and a C-terminal KASH domain, which acts as a nuclear envelope (NE) targeting motif. At the NE, via interactions with the Sun domain family of proteins and the nuclear lamina, nesprins on both the inner and outer nuclear membranes form the linker of the nucleoskeleton and cytoskeleton (LING) complex. This complex requires the giant nesprin-1 and nesprin-2 isoforms, which possess a pair of N-terminal calponin homology domains that bind directly to Filamentous-actin. However, via alternative promoter usage and alternative 3’ end processing, the nesprins are able to generate multiple mRNA transcripts, leading to the production of diverse tissue specific isoforms with potential roles beyond the NE. To explore further the capacity of nesprin-1 to generate alternative transcripts, 5’ and 3’ RACE was performed to identify cDNA ends which represent novel 5’ and 3’ untranslated regions (UTRs) respectively. By alternatively combining the differential 5’ and 3’ UTRs, multiple tissue specific nesprin-1 variants could be generated. Transfection of tagged constructs showed localizations to multiple sub-cellular compartments such as the nucleolus, focal adhesions, actin stress fibres and cytoplasmic particles, supporting the notion that nesprins are more than NE-cytoskeletal couplers. One of these novel nesprin-1 variants, p50Nesp1, was found to localize to cytoplasmic RNA granules called mRNA processing bodies (P-bodies). Using GST pull-downs and co-immunoprecipitations (co-IPs), p50Nesp1 was found to complex with mRNA decapping factors and translational repressers. More importantly, p50Nesp1 associated strongly with microtubules, both in vitro and in vivo, and was required for scaffolding P-body complexes to microtubules. By disrupting P-body-microtubule association with a dominant negative p50Nesp1 construct, time-lapse microscopy demonstrated impairment of fluorescently-labelled P-body proteins. Furthermore, this disruption resulted in P-bodies failing to associate with RNA stress granules and transferring p-globin mRNA reporter transcripts between compartments during the stress response. Further co-IP experiments identified a host of mRNA processing proteins that also associated with nesprin-1, including Matrin-3; an abundant nuclear matrix protein involved in a number of key nuclear processes. A novel isoform of matrin-3 localized to P-bodies and was required for miRNA-mediated translational repression. By identifying and tethering matrin-3 P-body localizing domains to a luciferase reporter construct, it was also found that matrin-3 could induce translational repression, which was significantly hampered when a single point mutation (S85C), previously described in a form of autosomal dominant distal myopathy, was introduced.

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Guo, Yi. "Multi-body and Nonlinear dynamics of Planetary Gear Drivetrains Considering Bearing Clearance and Acoustics." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1312817240.

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Gupta, Suresh. "Elasto-multi-body dynamics of internal combustion engines with thin-shell elastohydrodynamic journal bearings." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/34322.

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This thesis describes problems associated with noise and vibration concern in internal combustion engines as the result of a growing trend in the development of modern vehicular engines with high power to light weight ratios. There are a plethora of vibration concerns. These are owed to the increasing combustion forces in lean burn engines and the progressive use of materials of durable, but light-weight construction. The latter has come about as a result of a need to reduce the inertial imbalances. These features have resulted in achieving fuel efficiency. Although the primary aims in high output power and structural integrity have been largely achieved, these have culminated in an assortment of sources of noise and vibration, chiefly among them those associated with signature output of the combustion process. For the common four stroke engines, the contributory sources are at half-engine order multiples, referred to as engine "roughness". A holistic approach is to incorporate reduced engine roughness contributions as an integral part of engine design and development. The aim of this thesis is to create a methodology for fundamental design evaluation and analysis of engine dynamics, which comprises rigid body inertial dynamics of engine assembly, the elasto-dynamics of flexible and compliant components and applied and reactive forces in such a complex assembly.

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Kraft, Sönke. "Parameter identification for a TGV model." Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00731143.

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This work investigates the applicability of identification methods to the suspension parameters of a TGV multi-body model. The aim is to adjust the model to the real system by estimating the suspension parameters from measured vehicle response data. Due to the nonlinear behavior of the system the time-domain based model updating has been chosen. It requires the definition and minimization of a misfit function in the time domain describing the distance between model and measurement. The fastest convergence is obtained by the use of gradient methods requiring the calculation of the derivatives of the misfit function relative to every parameter. Since the calculation from finite differences is time consuming and less accurate the gradients are calculated from the adjoint method. The application to a simplified bogie model with known mathematical description allows the identification of its suspension parameters. The presence of local minima in the misfit function of the TGV model requires the use of global optimization methods. The simulated annealing and the genetic algorithm method give important reductions of the misfit function and improved parameter estimations. In following work this information could be used for further applications like the condition monitoring.

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Ostiguy, Matthew James. "Experiment and Simulation of the Acoustic Signature of Fatigued-Cracked Gears in a Two-Stage Gearbox." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1328.

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This thesis focuses on the development of a health monitoring system for gearbox transmissions. This was accomplished by developing and understanding a two-stage gearbox computer model that emulates an actual gearbox test rig. The computer model contains actual gearbox geometry, flexible shafts, bearings, gear contact forces, input motor torque, output brake torque, and realistic gearbox imbalance. The gear contact force of each gear stage and the input bearing translational acceleration were the main outputs compared between a healthy gearbox and damaged gearbox computer model. The damage of focus was a fatigue crack on the input pinion gear. A sideband energy ratio comparison yielded the computer simulation accurately modeled the difference between a healthy and damaged gearbox. The next step in this study involved the development of a repeatable procedure to initiate and propagate a fatigue crack at the tooth root in an actual spur gear. A damaged spur gear allows for a future comparison of an actual healthy and damaged gearbox system in the lab. A custom fatigue fixture was designed and manufactured for a Martin S1224BS 1 spur gear. The fatigue crack was initiated by position control fatigue testing which deflects the gear tooth a set amplitude for a number of cycles. Over the length of the test, the load that the tooth can withstand in bending decreases as damage begins to occur. Once the max load on the gear has dropped by a significant percentage (5-15%) a crack has initiated and begun to propagate across the tooth face. The use of a scanning electron microscope confirmed the presence a fatigue crack.

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Mello, Frank James. "Weak formulations in analytical dynamics, with applications to multi-rigid-body systems, using time finite elements." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/32854.

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Choi, Jun Hyeak. "Multibody dynamics of mechanism with secondary system." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/2841.

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Recent advances in predictive dynamics allow the user to not only predict physics based human motion simulations but also determine the actuation torques required to achieve those motions. The predictive dynamics approach uses optimization to predict motion while using many task based, physics based, and environment based constraints including the equations of motion. Many tasks have been simulated using this new method of predicting and simulating digital human motion, e.g. walking, running, stair climbing, and box lifting. In this research, we develop a method to predict the motion as well as effect of external equipment hanging on the digital human. The proposed method is tested on a simple case of a two degree of freedom serial chain mechanism with a simple passive system to behave as external equipment. In particular, the passive mass is assumed to be attached to the two links system with a spring and damper. The results of the proposed method are compared with the results obtained by integrating the equations of motion of the full three degree of freedom system.

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Collette, Christophe. "Usure ondulatoire en transport ferroviaire: mécanismes et réduction." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210701.

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L'usure ondulatoire des rails associée aux vibrations de torsion des essieux de métro a été mise en évidence il y a près d'un demi siècle. L'utilisation d'absorbeurs dynamiques comme solution potentielle à ce problème a été suggérée pour la première fois dans le projet américain du TCRP "Rail Corrugation Mitigation in Transit" en 1998. Cette thèse, réalisée dans le cadre du projet européén "Wheel-rail CORRUGATION in Urban transport", a pour objectif de concevoir un absorbeur dynamique et d'étudier son influence sur la réduction de l'usure ondulatoire liée aux vibrations de torsion. Dans le cadre de ce travail, d'autres types d'usure ondulatoire ont également été traités par des absorbeurs dynamiques.

Les trois premiers chapitres de cette thèse sont dédiés à la description des différents types d'usure ondulatoire et à la présentation des méthodes de prédiction. La méthode de dimensionnement des absorbeurs dynamiques est présentée au chapitre 4, ainsi que quelques perspectives de leur efficacité à réduire l'usure ondulatoire. Dans le chapitre 5, un tronçon réel du RER parisien a été étudié. D'une part les prédictions obtenues par différentes méthodes ont été comparées aux mesures sur site. D'autre part, le bénéfice résultant de l'utilisation d'un absorbeur dynamique a été étudié numériquement. Dans le chapitre 6, le cas de l'usure ondulatoire liée aux vibrations de torsion a été étudié spécifiquement. Un absorbeur dynamique a été développé pour réduire ce type d'usure ondulatoire. Son efficacité a été évaluée théoriquement et numériquement, avec un modèle multi-corps flexible du véhicule et de la voie. Dans le chapitre 7, un absorbeur dynamique visant à réduire les vibrations de torsion d'un essieu de métro à échelle réduite a été construit au laboratoire. Son efficacité a été validée expérimentalement en reproduisant les conditions d'apparition des vibrations de torsion de l'essieu sur le banc d'essais du Laboratoire des Technologies Nouvelles de l'INRETS. La correspondance entre les prédictions d'usure à échelle réduite et à échelle réelle a été établie. Une demande de brevet a été déposée par le Laboratoire des Structures Actives pour ce système (N° 06120344.4).
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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Perera, M. S. Malika. "Multi-physics for integrated analysis of flexible body dynamics with tribological conjunction in IC engines." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/33601.

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Since the inception of internal combustion engine, there has been a continual strive to improve its efficiency and refinement. Until very recently, the developments in this regard have been largely based on an experiential basis, or backed by analytical investigations, confined to particular features of the engines. This has been due to lack of computational power, and analysis tools of an integrative nature. In recent years enhanced computing power has meant that complex models, chiefly based on multi-body dynamics could be developed, and further enhanced by the inclusion of component flexibility in the form of structural modes, obtained through finite element analysis. This approach has enabled study of dynamics/vibration response of engines in a more quantitative manner than hitherto possible. Structural integrity issues, as well as noise and vibration (refinement) can then be studied in an integrated manner. However, earlier models still lack sufficient detail to include, within the same analysis, issues related to efficiency, chiefly prediction of parasitic losses due to mechanical imbalance and friction.

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Dissertations / Theses on the topic 'Multi Body Dynamic'

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