The necessity to reduce climate related emissions is driving the electrication of transportation. As well as reducing emissions Electric Vehicles (EV) have the capability of improving traction and vehicle stability. Unlike a conventional vehicle that uses a single Internal Combustion Engine (ICE) to drive one or both axles, an EV can have an electric machine driving each of the wheels independently. This opens up the possibility of using the electric machines as an actuator for traction control. In conventional vehicles the hydraulic brakes together with the ICE are used to actuate traction control. The advantages of electric machines over hydraulic brakes are precise measurable torque, higher bandwidth, bidirectional torque and kinetic energy recovery. A review of the literature shows that a wide range of control methods is used for traction control of EVs. These are mainly focused on control of an individual wheel, with only a minority being advanced to the experimental stage of verication. Integrated approaches to the control of multiple wheels are generally lacking, as well as verication that tests the vehicle's directional stability. A large body of the literature uses the slip ratio of the wheel as the key control variable. A signicant challenge for slip-based traction control is the detection of vehicle velocity together with the calculation of slip around zero vehicle velocity. A traction control method that does not depend upon vehicle velocity detection or slip ratio is Maximum Transmissible Torque Estimation (MTTE), after Yin et al. (2009). In this thesis an MTTE based method is developed for a full size electric vehicle with independently driven rear wheels. The original MTTE method for a single wheel is analysed using a simple quarter vehicle model. The simulation results of Yin et al. (2009) are in general reproducible although a lack of data in the original research prevents a quantitative comparison. A modication is proposed to the rate compensation term. Simulation results show that the proposed modication ensures that the torque demand is delivered to the wheel under normal driving conditions, this includes negative torque demand which is not possible for MTTE, Yin et al. (2009). Enabling negative torque demands means that the proposed traction control is compatible with higher level stability control such as torque vectoring. The performance of the controller is veried through a combination of simulation and vehicle based experiments. Compared with experiments, simulations are fast and inexpensive and can provide greater insight as all of the variables are observable. To simulate the controller a high delity vehicle model is required. To achieve this it is necessary to initially validate the model against experimental data. Simulation verication using a validated vehicle model is lacking in the literature. A full vehicle model is developed for this thesis using Dymola, a multi-body system software tool. The model includes the full suspension geometry of the vehicle. Pacejka's "Magic Formula" is used for the tyre model. The model is validated using Delta Motorsport's E4 coupe. The two Wheel Independent Drive (2WID) MTTE-based traction controller is derived from the equations of motion for the vehicle. This shows that the maximum transmissible torque for one driven wheel is dependent on the friction force of both driven wheels, which has not been shown before. An equal torque strategy is proposed to maintain vehicle directional stability on mixed-μ roads. For verication the 2WID-MTTE controller is simulated on the validated vehicle model described above. The proposed 2WID-MTTE controller is benchmarked against a similar method without the equal torque strategy, termed Independent MTTE, as well as a method combining Direct Yaw Control (DYC) and Independent MTTE. The three controllers are simulated for a vehicle accelerating onto a split-μ road. The results show that the proposed 2WID-MTTE controller prevents the vehicle spinning o the road when compared to Independent MTTE. 2WID-MTTE is found to be as eective as DYC+Independent MTTE but is simpler in design and requires fewer sensors. The proposed 2WID-MTTE controller is also simulated for a vehicle accelerating from a low- to high-μ road. This is done to assess the controller's ability to return to normal operation after a traction event, and because there are no simulations of this type for MTTE control on a high delity vehicle model in the literature. The results show that oscillations in the tyre-road friction force as the wheel transitions across the change in μ somewhat impede the return of the controller's output torque to the torque demand. The 2WID-MTTE controller is implemented on Delta Motorsport's E4 coupe by integrating it into the vehicle's Powertrain Control Module (PCM). This is experimentally tested for the vehicle accelerating across a range of surfaces at the MIRA proving ground. The experimental tests include high- to low-μ, low- to high-μ and split-μ roads. The results for the high- to low-μ road tests show that 2WID-MTTE control prevents the vehicle spinning when compared to no control. Similar to the simulation, the results of the low- to high-μ road experiment show that the controller output torque is also impeded from returning to the demand torque. Observation of the estimated friction force together with the on-board accelerometers conrm that this is due to tyre friction oscillating after the transition. This justies the use of a tyre model with transient dynamics. The proposed 2WID-MTTE controller uses wheel velocity and torque feedback to estimate friction torque. These signals are obtained from the vehicle's motor controllers via a Controlled Area Network (CAN) bus. The 2WID-MTTE controller is benchmarked against Independent MTTE that uses wheel velocity measured directly from the wheel hub sensors and the torque demand to estimate friction torque. The results show that the delays introduced by the CAN bus increase wheel slip for the 2WID-MTTE controller. However, the equal torque strategy means that 2WID-MTTE controller maintains greater vehicle directional stability, which is more important than the pursuit of greater acceleration.

No description available.

Le monde des Véhicules à Deux Roues Motorisés (VDRM) a changé considérablement,en matière de qualité et de performances. Ces véhicules ont pris une place importante dans notre vie quotidienne, que ce soit pour les déplacements ou les loisirs, ce qui a contribué à l’augmentation et à la diversité du parc. Néanmoins, la sécurité des usagers est devenue une des préoccupations des institutions routières et des organismes de recherche, vu le nombre croissant des accidents et la vulnérabilité à laquelle sont confrontés. Nos travaux de recherche s’inscrivent dans la thématique d’étude (modélisation et observation) et d’analyse de la dynamique limite des VDRM. L’objectif étant la conception des outils nécessaires à l’établissement de systèmes d’aide à la conduite, de type préventif, dédiés à renforcer la sécurité du conducteur et à améliorer sa conduite. Le principal outil est un bon dispositif de simulation, vu les contraintesrencontrées pour la réalisation en pratique des tests, tel que la sécurité du pilote, le coût, etc. C’est ainsi, qu’une synthèse de trois modèles dynamiques non linéaires, àun corps, à deux corps et à cinq corps, est proposée. Une fonction de risque, relativeà l’angle de roulis du véhicule maximal, est établie. Sa variation en fonction desparamètres inertiels et géométriques de l’ensemble véhicule et conducteur, de leursdynamiques et de l’infrastructure, a fait l’objet d’une étude approfondie. La difficultéd’implémentation de nombreux capteurs, nous a conduit à concevoir des méthodesd’observation des dynamiques importantes pour la mise en pratique des systèmesde sécurité. Pour ce faire, nous avons reconstruit les grandeurs, contribuant à la dynamique latérale, par l’application de l’observateur Proportionnel Double Intégral(P2I) sur deux cas de modèles (3DDL et 4 DDL). La dernière partie du mémoire, est consacrée aux travaux réalisés sur l’instrumentation du prototype Scooter dont dispose le laboratoire. L’analyse des données enregistrées sur piste et la validation des techniques d’observation développées y sont détaillées. / The world of Powered Two Wheeled (PTW) vehicles has changed considerably in quality and performance. These vehicles have taken an important place in our live, whether for transportation or leisure, which contributed to the increasing and diversity of their park. However, the safety of users has become a concern of road institutions and research organizations, given the increasing number of accidents and vulnerability at which they are faced. Our research fall within the thematic study of modeling, observation and dynamic limit analysis of the PTW vehicles. The main objective is to design tools needed to establish safety systems, of preventive kind, dedicated to enhance driver safety and improve his conduct. The main tool is a good device simulation, given the constraints encountered in the practical realization of tests, such as driver safety, cost, etc. For this, a synthesis of three non-linear dynamic models of one body, two bodies and five bodies, is proposed. A risk function relative to the maximum roll angle of the vehicle is established. Its variation according to the inertial and geometric parameters of the whole vehicle and driver, their dynamics and infrastructure, has been subject of extensive study. The difficulty of implementing many sensors has led us to develop methods to reconstruct the important dynamics for the implementation of safety systems. To do this, we reconstructed quantities contributing to the lateral dynamics by applying the Proportional Two Integral (P2I) observer. The last part of the manuscript is devoted to the work carried out about the instrumentationof the Scooter prototype, available at our laboratory. The analysis of the recorded data on the test track and the validation of the observers developed are detailed.

This Master of Science Thesis focuses on the modeling of an automotive system. Several of the main automotive systems are combined to represent a full vehicle model. One system is a road plane model with degrees of freedom in yaw and lateral acceleration. The model at first includes a two dimensional representation of a steering system and then later expands the steering model to three dimensions. Also included is a five degree of freedom, two-dimensional multibody model in order to model the response of the chassis/suspension system due to an applied step steer input. The tire system incorporates the Magic Formula tire model. Furthermore, a graphic user interface is developed to facilitate setting up the initial conditions and inputs to the full vehicle model, and to ease the use of the simulation.

The research project 'Controllability of Road Vehicles at the Limits of Tyre Adhesion' (CROVLA) was established to investigate how tyre and chassis properties contribute to the handling characteristics and stability of vehicles operating at or near to the limit condition. The project involved the Department of Transport, SP Tyres UK Limited, Jaguar Cars and Cranfield University. An extensive proving ground test program of typical limit handling tests provided characteristic driver input and vehicle response data for a variety of vehicle configurations. The test data analysis was based on the concept of correlation. Cross- correlation coefficients and average response time delays were obtained for various pairs of quantities, namely steering angle and torque for the input and yaw rate and lateral acceleration for the response. The predictability of the vehicle response was evaluated by the rate by which the correlation coefficients change with severity. Analogous to the proving ground work, vehicle dynamics simulations were carried out. Two programs were employed to study the steady state performance and the transient limit handling behaviour. The 'Steady State Cornering Model' was used to confirm some basic suspension design rules established for optimising the lateral adhesion of a suspension design. The importance of controlling camber and vehicle jacking by an appropriate suspension design was identified. A detailed vehicle model was built-up using the simulation code AUTOSIM. After validating the model against proving ground data, some parametric studies were conducted to quantify the effects of suspension and tyre properties on the transient limit response behaviour. Proving ground and simulation results suggest that response time lags and cross- correlation coefficients in combination with other handling parameters can be used as objective quality measures. The results quantified to what extent tyre and chassis modifications change the limit handling behaviour.

No description available.

A future limitation of autonomous ground vehicle technology is the inability of current algorithmic techniques to successfully predict the allowable dynamic operating ranges of unmanned ground vehicles. A further difficulty presented by real vehicles is that the payloads may and probably will change with unpredictably time as will the terrain on which it is expected to operate. To address this limitation, a methodology has been developed to generate real-time estimations of a vehicle's instantaneous Maneuvering Manifold. This approach uses force-moment method techniques to create an adaptive, parameterized vehicle model. A technique is developed for estimation of vehicle load state using internal sensors combined with low-magnitude maneuvers. An unscented Kalman filter based estimator is then used to estimate tire forces for use in determining the ground/tire coefficient of friction. Probabilistic techniques are then combined with a combined-slip pneumatic trail based estimator to estimate the coefficient of friction in real-time. This data is then combined to map out the instantaneous maneuvering manifold while applying techniques to account for dynamic rollover and stability limitations. The algorithms are implemented in MATLAB, simulated against TruckSim models, and results are shown to demonstrate the validity of the techniques. The developed methodology is shown to be a novel approach that is capable of addressing the problem of successfully estimating the available maneuvering manifold for autonomous ground vehicles. / Ph. D.

The tire is one of the most important components of the vehicle. It has many functions, such as supporting the load of the vehicle, transmitting the forces which drive, brake and guide the vehicle, and acting as the secondary suspension to absorb the effect of road irregularities before transmitting the forces to the vehicle suspension. A tire is a complex reinforced rubber composite air container. The structure of the tire is very complex. It consists of several layers of synthetic polymer, many flexible filaments of high modulus cord, and glass fiber, which are bonded to a matrix of low modulus polymeric material. As the tire is the only component of the vehicle which makes contact with the road surface, almost all forces and moments acting on the vehicle must be transferred by the tire. To predict the dynamics of the vehicle, we need to know these forces and moments generated at the tire contact patch. Therefore, tire models that accurately describe this dynamic behavior are needed for vehicle dynamic simulation. Many researchers developed tire models for vehicle dynamic simulations; however, most of the development in tire modeling has been limited to deterministic steady-state on-road tire models. The research conducted in this study is concerned with the development of semi-empirical transient tire models for on-road and off-road vehicle simulations. The semi-empirical transient tire model is developed based on existed tire models, analytical tire structure mechanics analysis, and experimental data collected by various researchers. The tire models were developed for vehicle traction, handling and ride analysis. The theoretical mechanics analysis of the tire model focused on the determination of tire and terrain deformation. Then, the results are used together with empirical data to calculate the force response and the moment response. Moreover, the influence of parametric uncertainties in tire parameters on the tire-terrain interaction is investigated. The parametric uncertainties are quantified and propagated through the tire models using a polynomial chaos theory with a collocation approach. To illustrate the capabilities of the tire models developed, both deterministic and stochastic tire models are simulated for various scenarios and maneuvers. Numerically simulated results are analyzed from the perspective of vehicle dynamics. Such an analysis can be used in tire and vehicle development and design. / Ph. D.

The objective of this study was to develop a new Steer Tilt Control (STC) algorithm inspired by real driver behaviour and to test it in simulation with an experimentally validated non-linear vehicle model. In order to develop an exhaustive simulation model of the vehicle and to process experimental data correctly, a large number of modelling aspects were taken into consideration. The objective of the study was to identify the unique kinematics of a three-wheeled tilting vehicle and determine the importance of the kinematic effects on the vehicle system. In order to fully understand this unique class of vehicle, the effect of the driver’s mass on the vehicle inertia’s and the effect of the tilting on the vehicle’s yaw inertia were considered. A wide-ranging expression for the driver’s perceived acceleration was derived and the roll dynamics of the non-tilting part of the three-wheeled tilting vehicle assembly were modelled. The steering torque of the vehicle as fully analysed and, using the simulation model, methods to model the effect of a crosswind on the vehicle, to test the effect of driving up or downhill, and to determine the effect of road camber on the vehicle dynamics were considered. To create a better understanding of the control task, road experiments were carried out using an instrumented tilting three-wheeler to investigate the driver steer inputs necessary to both balance the vehicle and follow a fixed trajectory. The experimental results demonstrated that the drivers’ steering inputs varied even though they had to complete identical tasks. This result confirmed that there are multiple ways to control the roll of the vehicle. The results also showed that the tilt angle always led the steering angle and for a transient manoeuvre, the tilt angle was larger than the balanced tilt angle at the start of the manoeuvre and smaller than the balanced angle at the end of the manoeuvre. The next step in the investigation was the development of a comprehensive non-linear dynamics model of a tilting three-wheeler including a tyre model and a driver model. A new method was developed to estimate the parameters of a Magic Formula Tyre model using the road testing data. The vehicle and tyre model were validated using data from a range of test runs. The importance of a driver in the loop was recognised and the elements of a driver trajectory-tracking model were studied. The aim was to develop a driver model that demonstrated good i tracking and some similarity to real driver behaviour. The final model used the yaw rate demand to determine an anticipatory control steer angle and the current heading error and the vehicle’s lateral position error measured in the vehicle’s local axis system to make small steering adjustments. The STC method based on Proportional Integral Derivative (PID) control was tested with the vehicle model to determine its performance with the non-linear dynamics and the driver in the loop. It was shown that the driver model had the tendency to act against the STC and that the two could only act simultaneously for a very limited range of demand trajectory and velocity combinations. The crosswind, hill driving, and road camber models were combined with the vehicle simulation without a driver but with the PID based STC. The simulations showed that these environmental factors made the control task significantly more difficult. More importantly, it showed that these factors demanded an increased number of vehicle states to be fed back to the controller. A new algorithm for STC was developed using the full vehicle and driver model. One of the criteria was that the control algorithm had to be realizable in practice. The resulting controller was a logic algorithm that would choose an action based on the steering angle and velocity and the vehicle speed with online gain adjustment based on direction and order of magnitude of the perceived acceleration. The basis of the control was adjustment of the driver's steering input and it was shown that the vehicle's deviation from the driver's intended path was minimal.

The work undertaken in this research aims to develop a mathematical model which can replicate the behaviour of a racing driver controlling a vehicle at its handling limit. Most of the models proposed in the literature assume a perfect driver. A formulation taking human limitations into account would serve as a design and simulation tool for the automotive sector. A nonlinear vehicle model with five degrees of freedom under the action of external disturbances controlled by a Linear Quadratic Regulator (LQR) is first proposed to assess the validity of state variances as stability metrics. Comparison to existing stability and controllability criteria indicates that this novel metric can provide meaningful insights into vehicle performance. The LQR however, fails to stabilise the vehicle as tyres saturate. The formulation is extended to improve its robustness. Full nonlinear optimisation with direct transcription is used to derive a controller that can stabilise a vehicle at the handling limit under the action of disturbances. The careful choice of discretisation method and track description allow for reduced computing times. The performance of the controller is assessed using two vehicle configurations, Understeered and Oversteered, in scenarios characterised by increasing levels of non- linearity and geometrical complexity. All tests confirm that vehicles can be stabilised at the handling limit. Parameter studies are also carried out to reveal key aspects of the driving strategy. The driver model is validated against Driver In The Loop simulations for simple and complex manoeuvres. The analysis of experimental data led to the proposal of a novel driving strategy. Driver randomness is modelled as an external disturbance in the driver Neuromuscular System. The statistics of states and controls are found to be in good agreement. The prediction capabilities of the controller can be considered satisfactory.