In this paper, a roll stability controller (RSC) is presented based on an eight degree of freedom dynamic vehicle model. The controller is designed for and tested on a scaled vehicle performing obstacle avoidance maneuvers on a populated test track. A rapidly-exploring random tree (RRT) algorithm is used for the vehicle to execute a trajectory around an obstacle, and examines the geographic, non-homonymic, and dynamic constraints to maneuver around the obstacle. A model predictive controller (MPC) uses information about the vehicle state and, based on a weighted performance measure, generates an optimal trajectory around the obstacle. The RSC uses the standard vehicle state sensors: four wheel mounted encoders, a steering angle sensor, and a six degree of freedom inertial measurement unit (IMU). An emphasis is placed on the mitigation of rollover and spin-out, however if a safe maneuver is not found and a collision is inevitable, the program will run a brake command to reduce the vehicle speed before impact. The trajectory is updated at a rate of 20 Hz, providing improved stability and maneuverability for speeds up to 10 ft/s and turn angles of up to 20°.

MAGnetic LEVitation Guidance System (MAGLEV) technology was commercially introduced relatively recently in the guided transport field. It is based on removing the wheels and rails of classic railway systems and supporting and guiding the train with magnets and magnetic forces instead. But, as for conventional railways, those trains need to fulfil dynamic requirements in order to make trains safe and comfortable. The dynamics of a train being mainly influenced by its suspensions characteristics, the magnetic forces generated in MAGLEV systems are of prime importance. Having a model of those systems allows to check the requirements of a certain design, and to consider the influence of different parameters on their fulfilment. This thesis leans on research work on MAGLEV vehicle modelling to model and implement magnetic levitation components in a quarter-car model in order to study the fulfilment of vehicle dynamics requirements. Specifically, the modelled vehicles are based on Electro- Magnetic Suspension (EMS) and Electro-Dynamic Suspension (EDS) (Inductrack) technologies, for which the modelling equations are analysed to study the magnetic force dependencies with physical and operational parameters. Finally, the dynamic requirements are checked in response to a set of track irregularities amplitudes, anda parametric study is carried out to verify the fulfilment of those requirements for other design cases. The results show that it is possible to model and implement simple MAGLEV MBS models for dynamic studies, although it is challenging to model and simulate specific MAGLEV components because of the lack of component specifications or experimental data on track irregularities. / MAGLEV-tekniken introducerades kommersiellt relativt nyligen inom området för marktransporter. Denbygger på att man tar bort hjul och räls från klassiska järnvägssystem och istället stöder och styr tåget med magneter och magnetiska krafter. Men precis som för konventionella järnvägar måste dessa tåg uppfylla dynamiska krav för att tågen ska vara säkra och bekväma. Eftersom ett tågs dynamik huvudsakligen påverkas av dess upphängningsegenskaper, är de magnetiska krafter som genereras i MAGLEVsystem av största betydelse. Genom att ha en modell av dessa system kan man kontrollera kraven för en viss konstruktion och överväga hur olika parametrar påverkar deras uppfyllande. Detta mastersarbete behandlar MAGLEV-fordonsmodellering för att implementera magnetiska levitationskomponenter i en kvartsfordonsmodell för att studera uppfyllandet av fordonsdynamiska krav. De modellerade fordonen är baserade på EMS- och EDS-teknik, för vilka modelleringsekvationerna analyseras för att studera den magnetiska kraftens beroende av fysiska och operativa parametrar. Slutligen kontrolleras de dynamiska kraven som svar på en uppsättning amplituder för ojämnheter i banan, och en parametrisk studie utförs för att verifiera uppfyllandet av dessa krav för andra konstruktionsfall. Resultaten visar att det är möjligt att modellera och implementera enkla MAGLEV MBS-modeller för dynamiska studier, även om det är en utmaning att göra det med specifika MAGLEV-komponenter på grund av bristen på komponentspecifikationer eller experimentella data om banojämnheter.

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This thesis presents a new nonlinear automobile dynamical model and investigates the possibility of automobile dynamic control with wheel torque utilizing this model. The model has been developed from first principles by applying classical mechanics. Inputs to the model are the four independent wheel torques, while the steer angles at each wheel are specified as independent time-varying signals. In this way, consideration of a variety of steering system architectures, including rear-wheel steer, is possible, and steering introduces time-varying structure into the vehicle model. The frictional contact at the wheel-road interface is modeled by use of the LuGre dynamic friction model. Extensions to the existing two-dimensional LuGre friction model are derived and the steady-state of the friction model is compared to existing static friction models. Simulation results are presented to validate the model mathematics and to explore automobile behavior in a variety of scenarios. Vehicle control with wheel torque is explored using the theory of input-output linearization for multi-input multi-output systems. System relative degree is analyzed and use of steady-state LuGre friction in a control design model is shown to give rise to relative degree singularities when no wheel slip occurs. Dynamic LuGre friction does not cause such singularities, but instead has an ill-defined nature under the same no-slip condition. A method for treating this ill-defined condition is developed, leading to the potential for the system to have relative degree. Longitudinal velocity control and combined longitudinal and angular vehicle velocity control are demonstrated in simulation using input-output linearization, and are shown to produce improved vehicle response as compared to the open-loop behavior of the automobile. Robustness of the longitudinal velocity control to friction model parameter variation is explored and little impact to the controller's ability to track the desired trajectory is observed.

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