A wheeled mobile robot (WMR) will move on uneven terrain without slip if the length of the axle connecting two wheels can change or for a fixed length axle the wheels are allowed to tilt in a lateral direction. In this work, we consider a three-wheeled mobile robot with torus shaped wheels capable of lateral tilting. Due to the requirement of lateral tilting a two degree of freedom (DOF) suspension, one for maintaining contact with terrain and one for lateral tilting, is assumed to connect the wheels to the WMR body. Six concepts of two DOF suspension mechanisms are proposed. A WMR with these suspension mechanisms are modeled and two kinds of simulations, namely, direct kinematic analysis and inverse kinematic analysis are performed on several uneven terrains with and without suspension. Slip velocity, the path followed and the lateral tilt angle are estimated as a function of time. The force-angle stability measure is used to check the tip-over instability of the WMR on uneven terrain. It is shown that without the two DOF suspensions and with the wheels not allowed to tilt laterally, the WMR is not capable of traversing uneven terrains without large slip. When the wheels are allowed to tilt laterally with a two DOF suspension, the wheeled mobile robot slips very little. Based on least slip and less deviation from desired path, it is shown that the two best possible suspension mechanisms are the SFTA suspension and D4Bar suspension. Two prototype of three-wheeled mobile robot with these suspensions are fabricated using some components from a readily available commercial kit and with especially designed and manufactured wheels with the two degrees of freedom suspension. Simulations on an uneven terrain verify that the three-wheeled mobile robot can traverse uneven terrains with very little slip for three representative paths, namely a straight line, a circular arc and a path representing a lane change. Experiments with the two prototypes on physically constructed uneven terrain, very similar to the one used for simulation, confirm that the slip is significantly reduced with the two degree of freedom suspensions. The path of the centre of mass of the WMRs, projected on uneven surface, and the error from the desired path is presented for all the three representative paths. The simulation and experimental results clearly show that the three wheeled mobile robot with the novel two DOF suspension mechanisms can traverse uneven terrain with low slip.

Dans la plupart des applications concernant un fluide s'écoulant sur une surface solide, la condition de non-glissement est largement utilisée car elle est simple et produit des résultats en accord avec les expériences. Toutefois, cette condition de limite n'est plus appropriée lorsque l'écoulement considéré est à l'échelle micro ou nano-métrique. Pour modéliser cet effet à l'échelle macroscopique, les conditions aux limites de Navier ont été introduites, avec la longueur de glissement comme paramètre. Lorsque le fluide est un gaz, cette longueur est liée au coefficient d'accommodation tangentiel (TMAC) et au libre parcours moyen, selon le modèle de Maxwell. Le but de ce travail est de traiter systématiquement ce modèle par une approche multi échelle et de l'étendre en incorporant la morphologie et l'anisotropie de la surface. La thèse est composée de cinq chapitres. Après l'Introduction, les notions de base de la théorie cinétique des gaz, l'équation de Boltzmann et les solutions associées (Navier-Stokes-Fourier, Burnett, Grad, Direct Simulation Monte Carlo…) sont rappelées dans le chapitre 1. Les modèles d'interaction gaz-paroi ainsi que les modèles de glissement introduits dans le cadre le la mécanique des fluides sont aussi rappelés. Le chapitre se termine par la description de la méthode de calcul par dynamique moléculaire (MD) utilisée dans ce travail. Le chapitre 2 est dédié au développement d'une technique simple afin de simuler les écoulements induits par la pression. Le principe est de se baser sur les formules atomistiques du tenseur des contraintes (Irving Kirkwood, Méthode de Plan, Contraintes Virielles) et de modifier les conditions périodiques, tout en maintenant la différence entre l'énergie cinétique des atomes à l'entrée et à sortie du domaine de calcul. Plusieurs types de conduite sont étudiés avec cette technique. Les résultats (température, vitesses, …) sont discutés et comparés. Le chapitre 3 concerne l'étude du potentiel d'interaction gaz-paroi par la méthode ab-initio. Le code CRYSTAL 09 est utilisé pour obtenir le potentiel entre un atome d'argon (Ar) et une surface de platine (Pt) <111> en fonction de la distance. Ensuite, le potentiel atome/surface est décomposé en potentiel binaire et approché par une fonction analytique. Cette fonction est ensuite implémentée dans un code MD pour simuler les collisions gaz-paroi et déterminer le coefficient TMAC.Dans le chapitre 4, l'effet de morphologie est étudié. Le potentiel multi-corps Quantum Sutton Chen(QSC) est utilisé pour le solide Pt <100> et un des potentiels binaires étudié dans le chapitre précédent pour le couple Ar-Pt. Le potentiel QSC est nécessaire pour reproduire l'effet de surface qui affecte le résultat final. Différentes surfaces sont traitées : surface lisse, surface nanostructurée, surface aléatoire obtenue par déposition de vapeur (CVD). Le coefficient TMAC est déterminé de façon généralisée, c.à.d en fonction de l'angle du flux d'atomes incidents sur la surface. Les anisotropies de surface et le noyau de collision sont également examinés. Dans le chapitre 5, on propose un modèle de glissement anisotrope pour les fluides en fonction du tenseur d'accommodation. Le modèle est obtenu par les calculs analytiques approchés développés dans le cadre de la théorie cinétique. On a ainsi généralisé l'équation de Maxwell en montrant que le tenseur de longueur de glissement est directement lié au tenseur d'accommodation. Le modèle est en bon accord avec les résultats de la méthode MD. Concernant la simulation MD, on a développé une technique pour reproduire l'anisotropie du tenseur d'accommodation. Le mémoire de thèse se termine par une synthèse des résultats obtenus. Des perspectives pour de futures études sont proposées / In most applications concerning a fluid flowing over a solid surface, the no-slip velocity condition was widely used because it is simple and produces the results in agreement with experiments. However, this dynamical boundary condition is not appropriate when the flow under consideration is at a micro or nano length scale.In order to model this effect at the macroscopic scale, the Navier boundary conditions have been introduced, with the slip length as a parameter. When the fluid is a gas, this length is related to the tangential momentum accommodation coefficient (TMAC) and the mean free path, according to the Maxwell model. The aim of this work is to systematically address this model using a multi-scale approach and to extend it by incorporating both the morphology and the anisotropy of a surface. The thesis consists of five chapters. In Chapter 1, the basics of the kinetic theory of gases, the Boltzmann equation and related solutions (Navier-Stokes-Fourier, Burnett, Grad, Direct Simulation Monte Carlo ...) are briefly presented. The models of gas-wall interaction and slip models introduced in the fluid mechanics are also recalled. The chapter ends with a description of the computational method used for the molecular dynamics simulations performed in this work. Chapter 2 is dedicated to the development of a simple technique to simulate the pressure driven flows. The principle is to rely on the atomistic formulas of the stress tensor (Irving Kirkwood, Method of Plane, Virial Stress) and to modify the periodic conditions by maintaining the difference between the kinetic energy of the ingoing and outgoing particles of the simulation domain. Several types of channels are studied with this technique. The results (temperature, velocity ...) are discussed and compared. Chapter 3 deals with the study of the gas-wall interaction potential by the ab-initio method. The code CRYSTAL 09 is used to obtain the potential between an atom of argon (Ar) and a surface of platinum (Pt) <111> as a function of distance. Then the gas-wall potential is decomposed into binary potential and approached by an analytic function. This function is then implemented in a MD code to simulate the gas-wall collisions and determine the TMAC coefficient. In Chapter 4, the effect of morphology is studied. The multi-body Quantum Sutton Chen (QSC) potential is used for Pt <100> solid and the binary potential proposed in the previous chapter for the Ar-Pt couple is employed. The QSC potential is needed to reproduce the surface effects that affect the final results. Different surfaces are treated : smooth, nanostructured surface and, random surface obtained by Chemical vapor deposition (CVD). The TMAC is determined using a generalized approach, i.e. depending on the angle of incident flux of gas atoms on the surface. The surface anisotropy and the scattering kernel are also examined. In Chapter 5, we propose a model of anisotropic slip for fluids based on accommodation tensor. The model is obtained by the analytical approximate calculations developed in the framework of the kinetic theory. We thus generalize Maxwell's equation by showing that the slip length tensor is directly related to the accommodation tensor. The model is in good agreement with the MD results. Thanks to our MD simulations, we develop a suitable technique for reproducing the anisotropy of the accommodation tensor. The thesis ends with a conclusion section in which we suggest some perspectives for a continuation of this work

Road vehicle tyres, railway wheels and ball bearings all generate rolling contact forces which are transferred within a finite area of contact between the rolling element and the substrate. Either it is visible or not for the human eye, a certain degree of roughness is always present on the contacting surfaces and it influences the generation of both vertical and lateral contactforces. The purpose of this investigation is to enhance the understanding and modelling of the influence from small-scale surface roughness on the generation of rolling contact forces. To this end, a computationally efficient method to include roughness-induced contact nonlinearities in the dynamic modelling of rolling contacts is proposed. The method is implemented in a time domain model for vertical wheel–track interaction to model rolling-induced rail vibrations, showing good agreement with measurements. Furthermore, a test rig is developed and used for the investigation of tyre–road rolling contact forces. Detailed studies are performed on the influence of substrate roughness on the resulting contact forces for a tyre tread block which is rolling at different operating conditions. The choice of substrate as well as the rolling velocity and the slip ratio is observed to have significant influence on the resulting friction coefficient. For high slip ratios, stick–slip oscillations appear, exhibiting frequency content which is largely dependent on the choice of substrate. The outcomes of this study can potentially be used to improve future tyre–road contacts with respect to wear, traction and noise generation. / <p>QC 20161013</p> / Centre for Eco2 Vehicle Design

The master thesis describes the methodology of laboratory and field measurements of tractors and tractor kits. It also contains graphical and tabular processing of measurement data and subsequent evaluation of the results obtained. It deals with the influence of power in the upper rod of three point hinge on wheel slip, work efficiency and fuel consumption.

Target of this diploma thesis is to propose connection of receiving yard of classification yard railway station Maloměřice including essential joint crossover into the line tracks in front junction Hády and junction station Královo Pole and also propose connection of line tracks n. 1A and 2A in the front junction Židenice. Part of the thesis is renewal of stations substructure and technological workflow proposal.

The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.

This master thesis covers conceptual design of haptic feedback system and safety and reliability assessment. System is developed for aircraft categories UL2, EASA CS-LSA, EASA CS-VLA and EASA-CS-23. Conceptual design is divided into three parts. First is aimed on haptic system test with simulator. Second is conceptual design of haptic system for in-flight test. Third part contains safety and reliability assessment and summarizes problems of haptic system installation in real aircraft.

Diploma thesis concerns in the first part about current knowledge in the field of electromagnetic waves, the history, development and distribution of radar, radar antenna types and distribution of structure radars. The second part deals with the problem formulation and analysis. The third part defines the specific goals of diplomas thesis and the fourth part proposes a solution methode. Design and design selection is included in fifth part. The sixth section analyze selected variant and describes its components. Final seventh part contains design assessment of structural, technological and economic aspect.

The thesis concentrates on the design of limited slip differential of the racing car. It describes the method of designing the model of space for differential, using the 3D ATOS scanner and Pro/ENGINEER software environment. The next part of the thesis illustrates the process of designing the model of mass-produced open differential. The main attention is paid to the design of both versions of clutch limited slip differential and also to the analysis of problematic issues of each analyzed component. Further on, there is a stress analysis of some selected parts: pressure ring, differential case and their comparison before and after their optimization.

This thesis describes the design of devices that will measure the directional characteristics of the tires. The first step is to analyze the directional characteristics and methods of measurement. The following equipment design, which should be designed to function while it was cheapest. The device is designed as a trailer towing vehicle. It also includes analysis of individual plant components important to measure those variables.