This thesis describes the initial development of the Texas A&M Autonomous Ground Vehicle test platform and waypoint following software, including the associated controller design. The original goal of the team responsible for the development of the vehicle was to enter the DARPA Grand Challenge in October 2005. A 2004 Ford F150 4x4 pickup was chosen as the vehicle platform and was modified with a 6” suspension lift and 35” tires, as well as a commercial drive-by-wire system. The waypoint following software, the design of which is described in this thesis, is written in C and successfully drives the vehicle on a course defined by GPS waypoints at speeds up to 50 mph. It uses various heuristics to determine desired speeds and headings and uses control feedback to guide the vehicle towards these desired states. A vehicle dynamics simulator was also developed for software testing. Ultimately, this software will accept commands from advanced obstacle avoidance software so that the vehicle can navigate in true off-road terrain.

Autonomous mobile robots - both aerial and terrestrial vehicles - have gained immense importance due to the broad spectrum of their potential military and civilian applications. One of the indispensable requirements for the autonomy of a mobile vehicle is the vehicle's capability of planning and executing its motion, that is, finding appropriate control inputs for the vehicle such that the resulting vehicle motion satisfies the requirements of the vehicular task. The motion planning and control problem is inherently complex because it involves two disparate sub-problems: (1) satisfaction of the vehicular task requirements, which requires tools from combinatorics and/or formal methods, and (2) design of the vehicle control laws, which requires tools from dynamical systems and control theory. Accordingly, this problem is usually decomposed and solved over two levels of hierarchy. The higher level, called the geometric path planning level, finds a geometric path that satisfies the vehicular task requirements, e.g., obstacle avoidance. The lower level, called the trajectory planning level, involves sufficient smoothening of this geometric path followed by a suitable time parametrization to obtain a reference trajectory for the vehicle. Although simple and efficient, such hierarchical separation suffers a serious drawback: the geometric path planner has no information of the kinematic and dynamic constraints of the vehicle. Consequently, the geometric planner may produce paths that the trajectory planner cannot transform into a feasible reference trajectory. Two main ideas appear in the literature to remedy this problem: (a) randomized sampling-based planning, which eliminates altogether the geometric planner by planning in the vehicle state space, and (b) geometric planning supported by feedback control laws. The former class of methods suffer from a lack of optimality of the resultant trajectory, while the latter class of methods makes a restrictive assumption concerning the vehicle kinematic model. In this thesis, we propose a hierarchical motion planning framework based on a novel mode of interaction between these two levels of planning. This interaction rests on the solution of a special shortest-path problem on graphs, namely, one using costs defined on multiple edge transitions in the path instead of the usual single edge transition costs. These costs are provided by a local trajectory generation algorithm, which we implement using model predictive control and the concept of effective target sets for simplifying the non-convex constraints involved in the problem. The proposed motion planner ensures "consistency" between the two levels of planning, i.e., a guarantee that the higher level geometric path is always associated with a kinematically and dynamically feasible trajectory. We show that the proposed motion planning approach offers distinct advantages in comparison with the competing approaches of discretization of the state space, of randomized sampling-based motion planning, and of local feedback-based, decoupled hierarchical motion planning. Finally, we propose a multi-resolution implementation of the proposed motion planner, which requires accurate descriptions of the environment and the vehicle only for short-term, local motion planning in the immediate vicinity of the vehicle.

Recently, mostly due to global warming concerns and high oil prices, electric vehicles have attracted a great deal of interest as an elegant solution to environmental and energy problems. In addition to the fact that electric vehicles have no tailpipe emissions and are more efficient than internal combustion engine vehicles, they represent more versatile platforms on which to apply advanced motion control techniques, since motor torque and speed can be generated and controlled quickly and precisely. The chassis control systems developed today are distinguished by the way the individual subsystems work in order to provide vehicle stability and control. However, the optimum driving dynamics can only be achieved when the tire forces on all wheels and in all three directions can be influenced and controlled precisely. This level of control requires that the vehicle is equipped with various chassis control systems that are integrated and networked together. Drive-by-wire electric vehicles with in-wheel motors provide the ideal platform for developing the required control system in such a situation. The focus of this thesis is to develop effective control strategies to improve driving dynamics and safety based on the philosophy of individually monitoring and controlling the tire forces on each wheel. A two-passenger electric all-wheel-drive urban vehicle (AUTO21EV) with four direct-drive in-wheel motors and an active steering system is designed and developed in this work. Based on this platform, an advanced fuzzy slip control system, a genetic fuzzy yaw moment controller, an advanced torque vectoring controller, and a genetic fuzzy active steering controller are developed, and the performance and effectiveness of each is evaluated using some standard test maneuvers. Finally, these control systems are integrated with each other by taking advantage of the strengths of each chassis control system and by distributing the required control effort between the in-wheel motors and the active steering system. The performance and effectiveness of the integrated control approach is evaluated and compared to the individual stability control systems, again based on some predefined standard test maneuvers.

The aim of electrification of chassis and driveline systems in road vehicles is to reduce the global emissions and their impact on the environment. The electrification of such systems in vehicles is enabling a whole new set of functionalities improving safety, handling and comfort for the user. This trend is leading to an increased number of elements in road vehicles such as additional sensors, actuators and software codes. As a result, the complexity of vehicle components and subsystems is rising and has to be handled during operation. Hence, the probability of potential faults that can lead to component or subsystem failures deteriorating the dynamic behaviour of road vehicles is becoming higher. Mechanical, electric, electronic or software faults can cause these failures independently or by mutually influencing each other, thereby leading to potentially critical traffic situations or even accidents. There is a need to analyse faults regarding their influence on the dynamic behaviour of road vehicles and to investigate their effect on the driver-vehicle interaction and to find new control strategies for fault handling. A structured method for the classification of faults regarding their influence on the longitudinal, lateral and yaw motion of a road vehicle is proposed. To evaluate this method, a broad failure mode and effect analysis was performed to identify and model relevant faults that have an effect on the vehicle dynamic behaviour. This fault classification method identifies the level of controllability, i.e. how easy or difficult it is for the driver and the vehicle control system to correct the disturbance on the vehicle behaviour caused by the fault. Fault-tolerant control strategies are suggested which can handle faults with a critical controllability level in order to maintain the directional stability of the vehicle. Based on the principle of control allocation, three fault-tolerant control strategies are proposed and have been evaluated in an electric vehicle with typical faults. It is shown that the control allocation strategies give a less critical trajectory deviation compared to an uncontrolled vehicle and a regular electronic stability control algorithm. An experimental validation confirmed the potential of this type of fault handling using one of the proposed control allocation strategies. Driver-vehicle interaction has been experimentally analysed during various failure conditions with typical faults of an electric driveline both at urban and motorway speeds. The driver reactions to the failure conditions were analysed and the extent to which the drivers could handle a fault were investigated. The drivers as such proved to be capable controllers by compensating for the occurring failures in time when they were prepared for the eventuality of a failure. Based on the experimental data, a failure-sensitive driver model has been developed and evaluated for different failure conditions. The suggested fault classification method was further verified with the conducted experimental studies. The interaction between drivers and a fault-tolerant control system with the occurrence of a fault that affects the vehicle dynamic stability was investigated further. The control allocation strategy has a positive influence on maintaining the intended path and the vehicle stability, and supports the driver by reducing the necessary corrective steering effort. This fault-tolerant control strategy has shown promising results and its potential for improving traffic safety. / <p>QC 20150520</p>

The thesis outlines a hierarchical modelling methodology for investigation in vehicle dynamics, in particular for combined ride and handling manoeuvres. The methodology involves the use of detailed multi-degrees of freedom models of vehicles with the inclusion of sources of non-linearity, using a multi-body approach, based on Lagrangian dynamics for constrained systems. It also includes the use of simpler and task-specific models, formulated in Newton-Euler approach. These simpler models with lower degrees of freedom, but with appropriate level of detail are more efficient in the study of specific, but non-trivial problems such as transient behaviour of vehicles in combined ride and handling, as encountered in many routine daily manoeuvres. The modelling methodology is supported by careful vehicle testing, both for validation of the proposed approach, and assessment of the extent of applicability of simple, intermediate and multi-degrees of freedom full-vehicle models. Certain important vehicle handling and ride characteristics in pitch plane dynamics, roll behaviour, vehicle body bounce and combination of these have been studied, as well as the effectiveness of restraining action of chassis elements, such as the semileading and trailing arms for passive control of vehicle squat and dive motions, arising from acceleration from coast to drive and deceleration/brake of vehicle from drive to coast. Combined pitch and bounce motions have been studied when negotiating speed traps such as bumps, which also combine with significant body roll when single event obstacles of this kind are introduced. The novelty of the research is in the detailed integrative numerical-experimental approach, and the development of intermediate models that adequately predict vehicle behaviour under steady and non-steady conditions for a wide range of ride and handling manoeuvres. The investigations have culminated in a significant number of findings of practical use, particularly the ineffectiveness of anti-squat and dive features when combined pitch and bounce motions limit the usefulness of these devices. On the contrary, excessive roll dynamic behaviour of the vehicle is effectively palliated by the anti-roll bar, even under complex combined pitch, roll and body bounce such as those experienced in negotiating single event speed bumps. Good agreement is found between the predictions of the intermediate model and those of the multi-body model and the actual vehicle tests, particularly for pitch and bounce dynamics.

Entre as etapas do desenvolvimento de automóveis pode-se apontar a definição das características de suas suspensões. A fase de definição da suspensão pode ser dividida dentro do seguinte cenário: a escolha de um determinado tipo de suspensão, os pontos (geometria) e quais os valores de rigidez/amortecimento para todo o sistema irá resultar em um comportamento dinâmico desejado para o veículo, bem como a viabilidade de produção. Além disso, o entendimento da interação entre os parâmetros de suspensão, é crucial para a otimização do desempenho. Este trabalho pretende propor um método para aperfeiçoar a fase de \"tuning\" da suspensão, com foco principal no conforto. O veículo considerado é um caminhão comercial, e entre os seus parâmetros considerados estão rigidezes de molas da cabine e suspensão, amortecimento da suspensão de cabine e curvas do amortecedor da suspensão primária. O modelo virtual do veículo foi desenvolvido em ambiente ADAMS, o qual, previamente à otimização, foi validado contra dados experimentais. Métricas foram especialmente desenvolvidas levando em consideração aspectos subjetivos de conforto veicular, para dessa forma eliminar a variabilidade entre as avaliações subjetivas e análises das simulações. Os resultados mostraram expressivas melhorias no conforto e através de dados experimentais essas melhorias foram confirmadas. / Among the development phases of an automotive vehicle one can point out the definition of the characteristics of its suspensions. Suspension definition phase can be understood as the following scenario: given a suspension type, which hard points (geometric) and what values of stiffness/damping for the whole system will result in a desired dynamic behavior for the vehicle as well as production feasibility. Moreover, understanding the iteration among the suspension parameters, even considering just the tuning ones, is crucial for performance optimization. This work intends to propose a method for vehicle tuning characteristics optimization, having as a target the ride comfort. The vehicle considered here is a commercial truck, and among its parameters one considers cabin and suspension springs, cabin dampers and suspension damper curves. A vehicle model was developed in ADAMS environment and prior to the optimization the vehicle was validated against experimental data. Metrics were specially developed to take into account subjective aspects of ride, and, in this way, eliminating the gap between subjective evaluations and simulations analysis. Results showed improvements in ride comfort. The resulting setup was measured and the improvements were confirmed with experimental data.

O aumento no número de veículos tem levado a um exagerado aumento das colisões. Para diminuir a quantidade e a gravidade dos acidentes, a segurança veicular passou a ser um ponto determinante na concepção de um automóvel. Dentre as principais frentes de estudo da segurança veicular está a redução da energia cinética transmitida aos ocupantes quando de uma colisão. Neste caso, os projetos de veículos empregam absorvedores de impacto, também conhecidos pelo termo em inglês crash box, para absorver a energia cinética do impacto em energia de deformação da estrutura. Este estudo tem por objetivo avaliar o desempenho dos absorvedores de energia mais comuns na literatura e na indústria. A avaliação ocorre por meio de simulações numéricas usando o método dos elementos finitos e por considerações teóricas de várias medidas de eficiência. Uma vez identificados os absorvedores de melhor desempenho ao impacto, estes são considerados como base para análises paramétricas de forma e material de modo a se aumentar sua eficiência. / The increase in vehicle production has lead to an increase in the number os colisions. To reduce the amount and severity of accident vehicle safety became an important issue in automobile design. Among the main vehicle safety researches is the reduction in the kinectic energy transmitted to the occupants in a colision event. Impact absorbers or crash boxes transform the impact kinectic energy into plastic deformation. This research aims to asses the performance of the most common energy absorbers used in the industry. The assesment is done trough numerical simulations by finite element analysis and trough theoretical approaches using different effciency measures. The most successful absorbers are used as basis for optimizing its shape and material usage.

Este trabalho apresenta um mecanismo alternativo para suspensões veiculares traseiras, com mobilidade igual a três, de arquitetura paralela e assimétrico, com três cadeias cinemáticas ativas distintas. O mecanismo é capaz de variar simultaneamente os ângulos de cambagem e de esterçamento das rodas traseiras do veículo, além de atuar sobre a rolagem da massa suspensa. Aplicando-se métodos de síntese de mecanismos paralelos, obtiveram-se topologias de mecanismos de suspensão com estrutura cinemática paralela e, por meio de um critério sistemático, selecionou-se uma estrutura cinemática que atendeu aos três movimentos independentes no espaço tridimensional, desejados para o mecanismo. Um modelo cinemático e outro cinetoestático foram desenvolvidos para verificar a adequação do mecanismo à aplicação veicular. Três análises são apresentadas para avaliar o potencial do mecanismo paralelo sintetizado em aplicações veiculares: análise de desempenho, análise de viabilidade e análise cinemática. Na análise de desempenho, constatou-se que, a atuação do mecanismo sobre os ângulos de cambagem e de esterçamento das rodas traseiras, bem como a atuação sobre a rolagem da massa suspensa trazem benefícios sobre o comportamento dinâmico do veículo, quando comparado com o desempenho dinâmico de um veículo com suspensão convencional. Por meio da análise de viabilidade, determinou-se o curso, a velocidade, a força e a potência demandada pelo sistema de atuação, onde se observou que a atuação do mecanismo pode ser obtida a partir de atuadores comerciais. Nas análises de desempenho e viabilidade o comportamento dinâmico do veículo foi simulado em três manobras distintas: curva de raio constante em regime permanente, dupla mudança de faixa e manobra do anzol (fishhook), empregando uma cosimulação entre os programas CarSim e MATLAB/SIMULINK. Pela análise cinemática, percebeu-se que não há configurações singulares dentro do espaço de trabalho especificado para o mecanismo. O espaço de trabalho disponível atende ao especificado para a aplicação proposta do mecanismo e os erros que os ângulos de cambagem e de esterçamento possam apresentar, devido à imprecisão no posicionamento dos atuadores ou às tolerâncias inerentes ao processo de fabricação das peças do mecanismo, não comprometem os ganhos no comportamento dinâmico que o veículo com o mecanismo proposto apresentou nas simulações da análise de desempenho. / This work introduces an alternative three-degree-of-freedom mechanism for automotive rear suspensions, capable to adjust simultaneously the camber, toe and roll angles. Topologically, the mechanism is parallel and asymmetric with three distinct active kinematic chains. The mechanism is able to adjust the camber, toe and roll angles simultaneously. After applying the methods to perform synthesis of mechanisms, the architecture candidates were ranked in accordance with some proposed indices. Two mathematical models are developed: the kinematic and kinetostatic ones. In order to evaluate how promising this mechanism is, three analyses are conducted: a performance analysis, a feasibility analysis and a kinematic analysis. The obtained results have shown the capability of the mechanism actuation to improve vehicle handling performance, when compared to a car equipped with a conventional suspension system. Moreover, the mechanism feasibility analysis has shown that the actuators stroke, velocity and force can be obtained by using standard hydraulic or eletromechanical actuators. The evaluation was based on three maneuvers: a steady-state cornering, a fishhook and a double lane change. Regarding to the kinematic analysis, three considerations were made. First, there is not singular configuration inside the workspace. Second, the available workspace can attend the camber and rear steer angles stroke. Third, the vehicle dynamic behavior is not affected by the errors due to the manufacturing tolerance and actuators position inaccuracy.

V této práci je prezentován a popsán FlexRay komunikační protokol se sběrnicí. Je představeno několik matematických modelů vozidel pro simulaci a pro vývoj řídících systémů. Dále je popsána tvorba signálové brány pro testovací vozidlo. Software pro úpravu signálu je implementován a odzkoušen v testovacím vozidle. Matematick0 modely byli parametrizovány aby odpovídali skutečnému vozidlu. Vyvinuté řídící systémy pro ovládání vozidla skrze losí test byli implementovány do automobilu a jejich vlastnosti byli otestovány. Závěrem jsou prezentovány výsledky testů jednotlivých řídících systémů.

This thesis deals with design concept of the electric car. At first, vehicle dynamics was solved in program MathCad. The components were selected from the obtained results. This was followed by a proposal layout design and vehicles main dimensions design. The frame was created in program ProEngineer, and then imported into ANSYS. Simulation of torsional rigidity was made in ANSYS by FEM.