Moderne Kraftfahrzeuge werden mit einer Vielzahl von Fahrerassistenzsystemen ausgestattet um die Sicherheit, die Traktion, die Energieeffzienz, die Agilität und den Komfort noch weiter zu verbessern. Diese Ziele können zu einem Großteil mit einer aktiven Drehmomentverteilung, auch Torque Vectoring genannt, erreicht werden. Dafür sind jedoch Getriebesysteme erforderlich, welche unabhängig vom Fahrzustand und vom Antriebsmoment eine nahezu beliebige Drehmomentverteilung ermöglichen. In der vorliegenden Arbeit werden zunächst Grundlagen zu Getriebesystemen, insbesondere zu Planetengetrieben, und zur Fahrzeugdynamik erläutert. Anschließend wird der Stand der Technik anhand einer Systematik zur Einteilung von aktiven Differenzialgetrieben dargelegt sowie einige Vor- und Nachteile aufgezeigt. Das folgende Kapitel stellt ein Verfahren zur Ermittlung der mechanischen Belastung des aktiven Differenzialgetriebes für beliebige Fahrzeuge und Strecken vor. Damit erfolgt eine Bewertung der bisher bekannten Systeme hinsichtlich Gesamtwirkungsgrad, konstruktiver Aufwand und regelungstechnische Eigenschaften. Im Anschluss wird ein Verfahren zur rechnergestützten Synthese neuer Getriebesysteme beschrieben. Abschließend werden die positiven Auswirkungen der aktiven Drehmomentverteilung auf die Fahrdynamik herausgestellt. Das Ergebnis der Arbeit zeigt drei neue Getriebestrukturen, welche anhand der deffinierten Vergleichskriterien besser sind als alle bekannten Systeme. / Actual passenger cars are equipped with a lot of driver assistant systems to increase safety, traction, efficiency, agility and comfort. These aims can be achieved by a controlled transmission of the engine torque to each driven wheel (active torque distribution, Torque Vectoring). Therefore special gear systems are necessary. In this document firstly the basics on gear systems (planetary gears) and vehicle dynamics are explained. Furthermore the state of the art is shown based on a classification of active differentials and the advantages and disadvantages are envinced. The next chapter describes a method for determining the mechanic load of the active differential for any car and road track. This is used for an evaluation of every differential gear system in view of efficiency, mechanic effort and control properties. The result reveals significant differences between the gear structures. Subsequent a method for a computer synthesis of new gear systems is developped and applied to the demands of a front driven vehicle application. The last chapter points out the positive effects of an active torque distribution on the driving dynamics. As a result of this work three new gear structures are shown which are much better than all existing gear systems in terms of the evaluation properties.

Two vehicular optimal control problems are visited. The first relates to the minimum lap time problem, which is of interest in racing and the second the minimum fuel problem, which is of great importance in commercial road vehicles. Historically, minimum lap time problems were considered impractical due to their slow solution times compared with the quasi-steady static (QSS) simulations. However, with increasing computational power and advancement of numerical algorithms, such problems have become an invaluable tool for the racing teams. To keep the solution times reasonable, much attention still has to be paid to the problem formulation. The suspension of a Formula One car is modelled using classical mechanics and a meta-model is proposed to enable its incorporation in the optimal control problem. The interactions between the aerodynamics and the suspension are thereby studied and various related parameters are optimised. Aerodynamics plays a crucial role in the performance of Formula One cars. The influence of a locally applied perturbation to the aerodynamic balance is investigated to determine if a compromise made in design can actually lead to lap time improvements. Various issues related to minimum lap time calculations are then discussed. With the danger of climate change and the pressing need to reduce emissions, improvements in fuel consumption are presently needed more than ever. A methodology is developed for fuel performance optimisation of a hybrid vehicle equipped with an undersized engine, battery and a flywheel. Rather than using the widely used driving cycles, a three-dimensional route is chosen and the optimal driving and power management strategy is found with respect to a time of arrival constraint. The benefits of a multi-storage configuration are thereby demonstrated. Finally, the nonlinear stability of a vehicle model described by rational vector fields is investigated using region of attraction (RoA) analysis. With the aid of sum-of-squares programming techniques, Lyapunov functions are found whose level sets act as an under-approximation to the RoA. The influence of different vehicle parameters and driving conditions on the RoA is studied.

La stabilité en roulis des véhicules est un problème de sécurité très critique, en particulier pour les poids lourds. Actuellement, la plupart des poids lourds sont équipés de systèmes de barres anti-roulis passifs. Malheureusement ceux-ci ne sont pas capables, en général, de surmonter les situations critiques. Cette thèse se concentre sur les systèmes de barres anti-roulis actifs, qui constituent l'approche la plus communément utilisée pour améliorer la stabilité en roulis des poids lourds. Le travail de recherche de cette thèse est divisé en trois parties principales. Dans la première partie, un modèle intégré est développé, comprenant quatre actionneurs hydrauliques commandés par des servo-valves, associés à un modèle linéaire lacet-roulis de poids lourd. Dans la deuxième partie, le système anti-roulis actif est développé suivant deux méthodologies de contrôle dans le cadre LTI: LQR et Hinfty. Dans la troisième partie, une approche LPV, basée sur le maillage, est utilisée pour synthétiser le contrôleur Hinfty/LPV de barre anti-roulis actif avec des fonctions de pondération dépendant de paramètres variants, à l'aide du progiciel LPVTools. Les résultats de simulation dans les domaines fréquentiel et temporel, ainsi que la validation avec le logiciel de simulation TruckSim, montrent que les systèmes de barres anti-roulis actifs sont une solution réaliste et efficace qui améliore considérablement la stabilité en roulis des poids lourds par rapport aux systèmes de barres anti-roulis passifs. / Vehicle rollover is a very serious problem for the safety of heavy vehicles. Most modern heavy vehicles are equipped with passive anti-roll bars, however they may be not sufficient to overcome critical situations. This thesis focuses on the active anti-roll bar system, which is the most common method used to improve roll stability of heavy vehicles.The thesis research work is divided into three main parts. In the first part, an integrated model is proposed with four electronic servo-valve hydraulic actuators mounted in a linear yaw-roll model of a single unit heavy vehicle. In the second part, the active anti-roll bar system uses two control approaches in the LTI framework: LQR, Hinfty. In the third part, the grid-based LPV approach is used to synthesize the Hinfty/LPV active anti-roll bar controller with parameter dependant weighting functions, by using LPVTools.The simulation results, in the frequency and time domains, as well as the validation by using the TruckSim simulation software, show that the active anti-roll bar control is a realistic and efficient solution which drastically improves roll stability of a single unit heavy vehicle, compared to the passive anti-roll bar.

O tema do conforto na automobilística é bastante extenso e possuidor de muitas interpretações. A ideia central deste trabalho é definir e direcionar alguns métricos para que, durante as fases de conceituação e desenvolvimento de um veículo, seja possível ter um direcional de definição de componentes e atributos veiculares de modo a facilitar o direcionamento dos atributos no programa veicular, e assim atingir suas necessidades. Como exemplo empregado, é empregado um veículo de plataforma tipo B em desenvolvimento por uma montadora, o qual teve as molas de suspensão definidas e rigidezes laterais de eixos com base em material técnico interno equivalente aos estudos apresentados neste trabalho. É adotada uma abordagem inicialmente empírica conforme os primeiros estudos de suspensões independentes realizados neste continente, depois o trabalho é complementado com exigências de normas especificas para vibrações (ISO2361, ISO5008, BS6055) de modo a caracterizar energia vibracional e a interpretação pelo ser humano. Porém como hoje em dia as suspensões automotivas são muito mais complexas, existem componentes específicos para as várias condições de solicitação, deste modo a análise é limitada a situações de ride (conforto) primário e handling (dirigibilidade) em situações de sublimite na faixa linear (cerca de 0,5 g). Como conclusão dos estudos, é possível ter em um veículo atributos de estabilidade sem necessariamente prejudicar o conforto, pois sendo definidos corretamente os componentes elásticos da dinâmica vertical para situações estacionárias e de ride primário, é definido seu equilíbrio estacionário e assim não é necessário comprometimento dos atributos de outros componentes para compensar alguma deficiência existente. / The range of assumptions for ride comfort is considered very wide in the automotive world and they can assume lots of possible interpretations. The central idea in this work is define and manage some metrics that, during the concept and development phases of a vehicular program, be possible to follow a better direction for the attributes development and so reach the program targets. As the example in this work, a B platform typical vehicle is used and it is under development in a carmaker, its suspension springs and axle roll stiffness were setup with technical information similar to the ones presented in this work. The initial approach is empiric as occurred with the first independent suspension system studies in this continent and in the sequence, the work is complemented with standards for vibrational issues (ISO2361, ISO5008, BS6055), after this, finally how the vibrational energy is defined and perceived by human beings. The automotive suspensions of current days are very complex and there are lots of specific components to do a specific work, so the analysis are limited to primary ride and sub limit handling (up to 0,5 g). As conclusion, its possible setup a car that is comfortable and stable in the same time, since the elastic components for the vertical dynamics and steady state conditions are correctly set, so its correct balance is reached and no other components attributes are compromised to compensate any deficiency.

Für die Entwicklung von Gesamtfahrzeugeigenschaften ist die objektive Beschreibung von Reifencharakteristika unter der Anwendung entsprechenden Bedingungen von wesentlicher Bedeutung. Der hierzu beschriebene, neuartige Prozess zur Reifencharakterisierung gründet sich auf einem definierten Satz objektiver Gesamtfahrzeugkenngrößen, welche mithilfe dedizierter Fahrmanöver identifiziert werden. Der Kern der hybriden Methode besteht in der zweckmäßigen Klassifizierung von Reifencharakteristika nach Struktur- und Reibgrößen. Auf Basis der kinematischen Deformationsmechanismen in der Reifenkontaktfläche und -konstruktion werden analytische Formulierungen für wesentliche Reifencharakteristika hergeleitet. Die Kombination neuer Prüfmethoden auf Flachbahn- und Anhängerprüfständen erlaubt anschließend deren präzise Identifikation. Zur Zusammenführung der autark gemessenen Eigenschaften wird ein analytisches Synthesemodell beschrieben, welches die Parameteridentifikation von empirischen Reifenmodellen erlaubt. Die Validierung der so identifizierten Reifeneigenschaften erfolgt auf der Gesamtfahrzeugebene. Hier bestätigt sich die maßgebliche Verbesserung der Fahrdynamikrechnung im Linear- und Grenzbereich gegenüber dem bisherigen Stand der Technik.

Dans ce travail, l’optimisation de la propulsion et de la commande des AUV (Autonomous Underwater Vehicles en anglais) est développée. Le modèle hydrodynamique de l’AUV est examiné. Egalement, son système de propulsion est étudié et des modèles pour des solutions de propulsion différentes (fixe et vectorielle) sont développés dans le cadre de la mobilité autonome.Le modèle et l’identification de la technologie de propulsion dite fixe sont basés sur un propulseur disponible commercialement. Le système de propulsion vectoriel est basé sur un prototype de propulseur magneto-couplé reconfigurable (PMCR) développé à l’IRDL-ENIB.Une méthode de commande non linéaire utilisant le modèle hydrodynamique de l’AUV est développée et son adaptation à deux systèmes de propulsion est présentée. Des analyses portant sur la commandabilité du robot et l’application de cette commande à différents systèmes sont proposées. L’optimisation globale est utilisée pour trouver des topologies propulsives et des paramètres de commande adaptés à la réalisation de tâches robotiques spécifiques. L’optimisation réalisée permet de trouver des solutions capables d’assurer le suivi de trajectoire et de minimiser la consommation énergétique du robot. L’optimisation utilise un algorithme génétique (algorithme évolutionnaire), une méthode d’optimisation stochastique appliquée ici à la conception orientée tâche de l’AUV. Les résultats de cette optimisation peuvent être utilisés comme une étape préliminaire dans la conception des AUVs, afin de donner des pistes pour améliorer les capacités de la propulsion.La technique d’optimisation est également appliquée au robot RSM (fabriqué au sein de l’IRDL-ENIB) en modifiant seulement quelques paramètres de sa topologie propulsive. Cela afin d’obtenir des configurations de propulsion adaptées au cours d’une seule et même mission aux spécificités locomotrices des tâches rencontrées : reconfiguration dynamique de la propulsion de l’AUV. / In this PhD thesis, the optimization of the propulsion and control of AUVs is developed. The hydrodynamic model of the AUVs is examined. Additionally, AUV propulsion topologies are studied and models for fixed and vectorial technology are developed. The fixed technology model is based on an off the shelf device, while the modeled vectorial propulsive system is based on a magnetic coupling thruster prototype developed in IRDL (Institut de Recherche Dupuy de Lôme) at ENI Brest. A control method using the hydrodynamic model is studied, its adaptation to two AUV topologies is presented and considerations about its applicability will be discussed. The optimization is used to find suitable propulsive topologies and control parameters in order to execute given robotic tasks, speeding up the convergence and minimizing the energy consumption. This is done using a genetic algorithm, which is a stochastic optimization method used for task-based design.The results of the optimization can be used as a preliminary stage in the design process of an AUV, giving ideas for enhanced propulsive configurations. The optimization technique is also applied to an IRDL existing robot, modifying only some of the propulsive topology parameters in order to readily adapt it to different tasks, making the AUV dynamically reconfigurable.

Concevoir un composant automobile et s’assurer que celui-ci atteindra un niveau de fiabilité cible requière une connaissance précise de la variabilité des chargements que ce composant est susceptible de rencontrer dans son environnement d’utilisation. La grande diversité des chargements appliqués à différents véhicules par différents clients, ou à un même véhicule tout au long de son historique d’utilisation, représente un défi statistique majeur. Généralement, l’acquisition d’information relative à la variabilité des chargements imposés aux composants des véhicules, repose sur la réalisation de campagnes de mesures. La complexité, la durée et le coût de telles campagnes limite naturellement la taille des échantillons statistiques constitués et les chargements enregistrés sont inévitablement dépendants du véhicule utilisé pour la mesure.Le travail présenté dans ce manuscrit explore la possibilité de changer fondamentalement d’approche, en se basant sur la simulation plutôt que sur la mesure et en concentrant l’effort d’analyse statistique non pas directement sur la variabilité des chargements mais sur la variabilité des facteurs qui les déterminent. Dans ce but, des modèles stochastiques sont proposés pour décrire l’évolution de la géométrie des surfaces de routes rencontrées par les véhicules ainsi que l’évolution de la vitesse à laquelle les conducteurs les parcourent. La caractérisation de la variabilité de ces facteurs est couplée à la notion de situations de vie. Ces dernières permettent de segmenter l’historique d’utilisation des véhicules, afin de faciliter l’analyse statistique de leur évolution au sein d’une population de clients. Pour finir, la réponse dynamique du véhicule à l’excitation générée par la route est déduite par la simulation.Des données statistiques relatives à la variabilité des facteurs de route et de vitesse sont évidemment nécessaires. L’information sur les routes parcourues peut par exemple être acquise à moindre coût au moyen d’une méthode d’estimation des profils de route proposée dans ce manuscrit. Cette information peut ensuite être exploitée afin de constituer, par la simulation, à un coût très faible et pour n’importe quel véhicule dont les caractéristiques sont connues, un échantillon d’historiques de chargements aussi important que souhaité. Cette méthodologie basée sur la simulation offre la possibilité d’analyser plus largement la variabilité des chargements de fatigue provenant de la route, l’influence des différents facteurs qui les déterminent ainsi que l’effet sur la fiabilité des composants du véhicule étudié. / In order to design vehicle components that will achieve a prescribed reliability target, it is imperative to possess a precise description of the variability of the loads to which such components may be subjected within the environment in which they are used. The strong diversity of the loads imposed on different vehicles by different customers, or on a particular vehicle throughout its life, constitutes a formidable statistical challenge. Generally, the acquisition of information about the load variability experienced by vehicle components is based on the use of load measurement campaigns. The complexity, duration and cost of such campaigns naturally limit the size of the statistical samples that may be collected. Moreover, the recorded load histories are inevitably dependent on the vehicle used for the measurements.The work presented within this manuscript explores the possibility of a fundamental change in the approach to load characterisation. The objective is to make use of simulation rather than measurements and focus statistical analysis efforts not directly on load variability itself but on the variability of the factors that determine such loads. Stochastic models are proposed to describe the evolution of the geometry of road surfaces covered by vehicles, as well as the evolution of vehicles’ speed on those road surfaces. The characterisation of the variability of such factors is performed in combination with the use of life situations. The latter may be employed to divide the load histories associated to different vehicles, within a population of customers, and analyse their variation more easily. Eventually, the dynamic response of the vehicle to the excitation imposed by the road can bederived through simulation.Statistical data on the variation of the road and speed factors obviously have to be acquired in order to apply the methodology. For example, road-related information may be obtained through the use of a road profile estimation algorithm proposed within the framework of this manuscript. Such information may then be exploited to constitute, through simulation, an arbitrarily large set of load histories at a very low cost and for any vehicle whose mechanical characteristics are known.The proposed methodology based on simulation enables us to study more extensively the variability of road-induced fatigue loads, the influence of the different factors that determine such loads, as well as the effect they have on the reliability of any considered vehicle component.

Stability is an important criterion in the design and performance of launch vehicles. Present day launch vehicles have become more and more flexible due to the constraints of weight reduction, necessarily imposed for enhanced performance of the vehicle. Due to higher flexibility, the launch vehicle stability becomes a concern. Instability in the launch vehicles has been noticed due to three major sources: thrust, aerodynamic forces and combustion induced instabilities. Instability in the launch vehicles may pose problem to the structural integrity leading to structural failure or it may lead to the deviation in the trajectory of the vehicle. Several structural failures of launch vehicles due to instabilities have been reported in the literature. The prediction of the structural response due to various excitations such as thrust and aerodynamic loading is essential to identify any failure scenarios and to limit the vibrations transmitted to the payload. Therefore, determination of dynamic and stability characteristics of a launch vehicle under the influence of different parameters, is of vital importance. Disciplines such as, flight mechanics (dynamics), structural dynamics, aerodynamics, propulsion, guidance and control are closely related in the design and analysis of launch vehicles. Typically, flight mechanics, guidance and control problems consider a rigid vehicle for modeling and simulation purposes. The disciplines of structural dynamics and aeroelasticity consider a flexible vehicle. In order to bring in the effect of flexibility on the flight dynamics of the launch vehicle, structural dynamics and aeroelasticity aspects need to be effected. The preliminary design of a new launch vehicle requires inputs from different disciplines and parametric studies are required to finalise the vehicle configuration. The study of the effect of different parameters on the dynamics and stability of launch vehicles is required. In this context, there is a need to develop an integrated approach that provides tools for the design and analysis of a launch vehicle. The availability of integrated modeling and simulation tools will reduce the requirement of costly prototype development and testing. In the present thesis, an attempt has been made to develop a numerical tool to conduct parametric studies for launch vehicle dynamics and stability. The developed tool is suitable for prediction of onset of instabilities under the influence of different parameters. The approach developed in this thesis is also well suited for specialized analysis of problems involving vertical launch, stage separation, engine shutdown and internal stress wave propagation related to structural integrity. Stability problems due to thrust and the aerodynamic forces (aeroelastic stability) in the launch vehicles/ missiles have been reported in the literature. Most of these works have modeled the vehicle as a beam or by using discrete degrees of freedom. In these works, the effect of thrust or aerodynamic forces on the flexible body modes is investigated and it is shown that the instability may occur in one of the bending modes due to change in the parameters such as thrust or aerodynamic forces. Traditionally, the dynamic characteristics are obtained in a body-fixed coordinate system, whereas the prediction of trajectory (rigid body dynamics) is carried out in an inertial frame of reference. Only few works have addressed the coupling of the rigid body motion and the flexible body dynamics of a vehicle. But these works also, do not consider the total derivative of displacements with respect to an inertial frame of reference. When the integrated equations of motion are derived in an inertial frame of reference, the rigid body motion and the elastic displacements are highly coupled. In this thesis, the rigid body motion and the flexible body dynamics is studied in an inertial frame of reference. The flexible body dynamics of the moving vehicle is studied in an inertial frame of reference, including velocity induced curvature effects, which have not been considered so far in the published literature. A detailed mechanics based model is developed to analyze the problem of structural instabilities in launch vehicles. Coupling among the rigid-body modes, the longitudinal vibrational modes and the transverse vibrational modes due to asymmetric lifting-body cross-section are considered. The model also incorporates the effects of aerodynamic forces and the propulsive thrust of the vehicle. The propulsive thrust is considered as a follower force. The model is one-dimensional, and it can be employed to idealized slender vehicles with complex shapes. The governing differential equations along with the boundary conditions are derived using Extended Hamilton’s principle. Subsequently, the modeling of the propulsive thrust and the aerodynamic forces are included in the formulation. In the literature, the propulsive thrust has generally been modeled as a follower force applied at the nozzle end. Few of the works in the literature have modeled the combustion process in the solid rocket motor and the liquid propellant engine in detail. This is required to understand the combustion induced instabilities. In the present thesis, the propulsive thrust is considered as a follower force and few of the combustion parameters affecting the thrust are considered. In the literature, the modeling of the aerodynamic forces acting on a launch vehicle has been carried out using general purpose computational fluid dynamics (CFD) codes or by using empirical methods. CFD codes are used to obtain the pressure and the shear stress distribution on the vehicle surface by the solution of Navier Stokes/ Euler equations. The empirical methods have been used to obtain the distributed aerodynamic forces acting on the vehicle. The aerodynamic forces are expressed in terms of distributed aerodynamic coefficients. In the present work, the modeling of the aerodynamic forces has been carried out in two different ways: using a CFD package and by using empirical methods. The stability of a system can be studied by determining the system response with time. Eigenvalue analysis is another tool to investigate the stability of a linear system. To study the stability characteristics of the system using eigenvalue analysis, a computational framework has been developed. For this purpose, the finite element discretization of the system is carried out. Further to that, two different methods are utilized for finite element discretization of the vehicle structure: Fourier Transform based Spectral Finite Element method (SFEM) and an hp Finite Element method (FEM). The conventional FEM is a versatile tool for modeling complicated structures and to obtain the solution of the system of equations for a variety of forcing functions. The SFEM is more suitable for obtaining the solution for simple 1D and 2D structures subjected to shock and transient loads, having high frequency content. In this thesis, the spectral finite element model is developed for a vehicle subjected to the propulsive thrust and the aerodynamic forces. Prediction of instability using SFEM, means solving a nonlinear eigenvalue problem. Standard computer codes or routines are not available for solving a nonlinear eigenvalue problem. A computer code has been written to solve the nonlinear eigenvalue problem using one of the algorithms available in the literature. An hp finite element model is also developed for launch vehicle. The finite element stiffness and damping matrices due to the thrust, the aerodynamic forces and the rigid body velocity and acceleration are derived using Lagrange’s equations of motion. A standard linear eigenvalue problem and a polynomial eigenvalue problem is formulated for determination of instability regimes of the vehicle. It is important to understand the influence of different parameters such as thrust, velocity, angle of attack etc. on the stability of a launch vehicle. Parametric studies are important during the preliminary design phase of a vehicle to identify the instability regimes. The design parameters can be changed to reduce the possibility of instabilities. Numerical simulations are carried out to determine the unstable regimes of a slender launch vehicle for propulsive thrust and velocity as the parameters, neglecting the aerodynamic forces. Comparison between the results based on a Fourier spectral finite element model and a hp finite element model are carried out. Phenomenon of static instability (divergence) and dynamic instability (flutter) are observed. Determination of mode shapes of the vehicle is important for deciding the placement of sensors and actuators on the vehicle. In this context, eigenvectors (mode shapes) for different end thrust and speed are analyzed. Further, numerical simulations are also carried out to determine the instabilities in a slender launch vehicle considering the combined effects of propulsive thrust, aerodynamic forces and mass variation. The finite element model simulation results for aeroelastic effects are compared with the published literature. Stability of a vehicle is analysed for velocity (free stream Mach number) as a parameter, at maximum propulsive thrust, including the effect of aerodynamic forces and mass variation. Phenomenon of static instability (divergence) and dynamic instability (flutter) are observed. With the increase in the Mach number, branching (splitting) and merging of the modes is observed. At higher Mach numbers, divergence and flutter are observed in different modes simultaneously. Numerical simulations are carried out for a typical nosecone launch vehicle configuration to analyse the aeroelastic stability at two different Mach numbers using empirical aerodynamic data. The phenomenon of flow separation and reattachment is observed at the cone-cylinder junction. The stability of a typical vehicle under propulsive thrust and aerodynamic forces is investigated using CFD derived aerodynamic data. The aerodynamic pressure and shear stress distribution for a launch vehicle are obtained from the CFD analysis. The effect of different parameters such as combustion chamber pressure, tip mass and slenderness ratio on the stability of a vehicle is studied. In the later part of the thesis, solution methodology for the time domain response for a coupled axial and transverse motion of a vehicle is developed. The axial responses (displacements and velocities) of a typical vehicle subjected to axial thrust are determined using direct integration of the equations of motion. The axial displacements due to two different thrust histories are compared. The axial velocities with time at different locations are determined. The time domain and the frequency domain responses for a representative vehicle subjected to a transverse shock force are determined using Spectral Finite Element method (SFEM). The system of equations for a coupled axial and transverse motion of a vehicle is developed. Numerical simulations are carried out to determine the coupled axial and transverse response of a vehicle subjected to axial and transverse forces. The coupling of rigid body motion with the elastic displacements is illustrated. The thesis is comprised of seven chapters. The first chapter gives a detailed introduction to launch vehicles and covers literature survey of launch vehicle dynamics and stability. The dynamics and stability related aspects of flexible structures are also discussed. In chapter 2, a detailed mathematical model of a slender launch vehicle is developed to analyze the problem of structural instabilities. Chapter 3 deals with the finite element discretization of the vehicle structure using two different methods: Fourier spectral finite element method and an hp finite element method. In chapters 4 and 5, numerical simulations are carried out to determine the instabilities in a slender launch vehicle considering the effects of propulsive thrust, aerodynamic forces and mass variation. In chapter 6, solution methodology for the time domain response for a coupled axial and transverse motion of a vehicle is developed. The last chapter gives the conclusions and the future scope of work. To summarize, this thesis is a comprehensive document, that not only describes some detailed mathematical models for launch vehicle stability studies, but also presents the effect of aerodynamic, propulsion and structural loads on the launch vehicle stability. Linear stability analysis of a representative vehicle is carried out for prediction of onset of the instabilities under the influence of different parameters such as velocity, thrust, combustion factors etc. The correlation between the stability analysis and the time domain response is established. In short, the matter presented in this thesis can serve as a useful design aide for those working in the launch vehicle design.

Moderne Kraftfahrzeuge werden mit einer Vielzahl von Fahrerassistenzsystemen ausgestattet um die Sicherheit, die Traktion, die Energieeffzienz, die Agilität und den Komfort noch weiter zu verbessern. Diese Ziele können zu einem Großteil mit einer aktiven Drehmomentverteilung, auch Torque Vectoring genannt, erreicht werden. Dafür sind jedoch Getriebesysteme erforderlich, welche unabhängig vom Fahrzustand und vom Antriebsmoment eine nahezu beliebige Drehmomentverteilung ermöglichen. In der vorliegenden Arbeit werden zunächst Grundlagen zu Getriebesystemen, insbesondere zu Planetengetrieben, und zur Fahrzeugdynamik erläutert. Anschließend wird der Stand der Technik anhand einer Systematik zur Einteilung von aktiven Differenzialgetrieben dargelegt sowie einige Vor- und Nachteile aufgezeigt. Das folgende Kapitel stellt ein Verfahren zur Ermittlung der mechanischen Belastung des aktiven Differenzialgetriebes für beliebige Fahrzeuge und Strecken vor. Damit erfolgt eine Bewertung der bisher bekannten Systeme hinsichtlich Gesamtwirkungsgrad, konstruktiver Aufwand und regelungstechnische Eigenschaften. Im Anschluss wird ein Verfahren zur rechnergestützten Synthese neuer Getriebesysteme beschrieben. Abschließend werden die positiven Auswirkungen der aktiven Drehmomentverteilung auf die Fahrdynamik herausgestellt. Das Ergebnis der Arbeit zeigt drei neue Getriebestrukturen, welche anhand der deffinierten Vergleichskriterien besser sind als alle bekannten Systeme.:1 Einleitung 2 Grundlagen 2.1 Getriebesysteme 2.2 Fahrdynamik 3 Stand der Technik 3.1 Getriebesysteme 3.2 Fahrdynamikregelung 4 Analyse bekannter Getriebesysteme 4.1 Zeitlicher Verlauf fahrdynamischer Größen 4.2 Systematische Analyse von Planetengetrieben 4.3 Deffinition der Vergleichskriterien 4.4 Differenziallose Systeme 4.5 Differenzialsysteme 4.6 Elektromotorische Systeme 4.7 Sonderbauformen 4.8 Vergleich bekannter Systeme 5 Synthese neuer Getriebestrukturen 5.1 Anforderungen an aktive Differenzialgetriebe 5.2 Manuelle Struktursynthese 5.3 Rechnergestützte Struktursynthese 5.4 Ergebnisse der Struktursynthese 6 Auswirkung von aktiver Drehmomentverteilung auf die Fahrdynamik 6.1 Komplexe Fahrdynamiksimulation 6.2 Steigerung der Traktion 6.3 Steigerung der Agilität 6.4 Steigerung der Fahrstabilität 6.5 Steigerung des Fahrkomforts 6.6 Verringerung des Kraftstoffverbrauches Zusammenfassung und Ausblick Literaturverzeichnis / Actual passenger cars are equipped with a lot of driver assistant systems to increase safety, traction, efficiency, agility and comfort. These aims can be achieved by a controlled transmission of the engine torque to each driven wheel (active torque distribution, Torque Vectoring). Therefore special gear systems are necessary. In this document firstly the basics on gear systems (planetary gears) and vehicle dynamics are explained. Furthermore the state of the art is shown based on a classification of active differentials and the advantages and disadvantages are envinced. The next chapter describes a method for determining the mechanic load of the active differential for any car and road track. This is used for an evaluation of every differential gear system in view of efficiency, mechanic effort and control properties. The result reveals significant differences between the gear structures. Subsequent a method for a computer synthesis of new gear systems is developped and applied to the demands of a front driven vehicle application. The last chapter points out the positive effects of an active torque distribution on the driving dynamics. As a result of this work three new gear structures are shown which are much better than all existing gear systems in terms of the evaluation properties.:1 Einleitung 2 Grundlagen 2.1 Getriebesysteme 2.2 Fahrdynamik 3 Stand der Technik 3.1 Getriebesysteme 3.2 Fahrdynamikregelung 4 Analyse bekannter Getriebesysteme 4.1 Zeitlicher Verlauf fahrdynamischer Größen 4.2 Systematische Analyse von Planetengetrieben 4.3 Deffinition der Vergleichskriterien 4.4 Differenziallose Systeme 4.5 Differenzialsysteme 4.6 Elektromotorische Systeme 4.7 Sonderbauformen 4.8 Vergleich bekannter Systeme 5 Synthese neuer Getriebestrukturen 5.1 Anforderungen an aktive Differenzialgetriebe 5.2 Manuelle Struktursynthese 5.3 Rechnergestützte Struktursynthese 5.4 Ergebnisse der Struktursynthese 6 Auswirkung von aktiver Drehmomentverteilung auf die Fahrdynamik 6.1 Komplexe Fahrdynamiksimulation 6.2 Steigerung der Traktion 6.3 Steigerung der Agilität 6.4 Steigerung der Fahrstabilität 6.5 Steigerung des Fahrkomforts 6.6 Verringerung des Kraftstoffverbrauches Zusammenfassung und Ausblick Literaturverzeichnis

Für die Entwicklung von Gesamtfahrzeugeigenschaften ist die objektive Beschreibung von Reifencharakteristika unter der Anwendung entsprechenden Bedingungen von wesentlicher Bedeutung. Der hierzu beschriebene, neuartige Prozess zur Reifencharakterisierung gründet sich auf einem definierten Satz objektiver Gesamtfahrzeugkenngrößen, welche mithilfe dedizierter Fahrmanöver identifiziert werden. Der Kern der hybriden Methode besteht in der zweckmäßigen Klassifizierung von Reifencharakteristika nach Struktur- und Reibgrößen. Auf Basis der kinematischen Deformationsmechanismen in der Reifenkontaktfläche und -konstruktion werden analytische Formulierungen für wesentliche Reifencharakteristika hergeleitet. Die Kombination neuer Prüfmethoden auf Flachbahn- und Anhängerprüfständen erlaubt anschließend deren präzise Identifikation. Zur Zusammenführung der autark gemessenen Eigenschaften wird ein analytisches Synthesemodell beschrieben, welches die Parameteridentifikation von empirischen Reifenmodellen erlaubt. Die Validierung der so identifizierten Reifeneigenschaften erfolgt auf der Gesamtfahrzeugebene. Hier bestätigt sich die maßgebliche Verbesserung der Fahrdynamikrechnung im Linear- und Grenzbereich gegenüber dem bisherigen Stand der Technik.