Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.

The carbody plays an important role in rail vehicle dynamics.This thesis aims atdeveloping validated modelling methods tostudy its dynamics, how it is excited on trackand how itinteracts with the passengers. The primary interest is ridecomfort,considering vibrations up to 20 Hz. In this frequencyrange, the structural flexibility ofthe carbody is of majorconcern. The models are intended for use intime-domainsimulation, calling for small-sized models to reducecomputational time and costs. Keyparameters are proposed toselect carbody eigenmodes for inclusion in a flexiblemultibodymodel, and to quantify the interaction between passengers andcarbody. Extensive comparisons between measurements and correspondingsimulations arecarried out in a case study. On-track measurementsare performed to obtain operatingdeflection shapes and powerspectral densities of the accelerations in the carbody.Thecomplete vehicle is modelled using the pieces of softwareGENSYS (flexible multibodymodel) and ANSYS (finite element modelof the carbody). Actual, measured trackirregularities are used asinput. In order to investigate the influence of passengerload,experimental modal analysis of the carbody is performed withand without passengers.Also, amplitude dependence is examined.Simple models, based on human-body modelsfrom literature, of thepassenger-carbody system are proposed and validated.Verticalseating dynamics is considered. The models areimplemented and tested in the casestudy. Finally, ideas on modelreduction and approximation are presented and applied. The main conclusions drawn from the study are that     the structural flexibility of the carbody must be takeninto account when predictingvertical vibration comfort. It ispossible to predict which carbody modes that willcontributemost to the vibrations.     the carbody dynamical properties depend on the excitationamplitude.     passengers and carbody interact significantly.- theproposed models describe the interaction quite well. Theproposed passenger-carbodymodel gives an upper boundary on theinteraction.     the proposed passenger-seat-carbody model can be used tostudy the influence of theseat parameters on the interaction.This merits to be investigated further, however. <b>Keywords</b>: Carbody, Experimental modal analysis, Human-bodydynamics, Modelreduction, Multibody dynamics, Operatingdeflection shapes, Rail-vehicle dynamics,Ride comfort, Seatingdynamics, Structural dynamics.

Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.

<p>The carbody plays an important role in rail vehicle dynamics.This thesis aims atdeveloping validated modelling methods tostudy its dynamics, how it is excited on trackand how itinteracts with the passengers. The primary interest is ridecomfort,considering vibrations up to 20 Hz. In this frequencyrange, the structural flexibility ofthe carbody is of majorconcern. The models are intended for use intime-domainsimulation, calling for small-sized models to reducecomputational time and costs. Keyparameters are proposed toselect carbody eigenmodes for inclusion in a flexiblemultibodymodel, and to quantify the interaction between passengers andcarbody.</p><p>Extensive comparisons between measurements and correspondingsimulations arecarried out in a case study. On-track measurementsare performed to obtain operatingdeflection shapes and powerspectral densities of the accelerations in the carbody.Thecomplete vehicle is modelled using the pieces of softwareGENSYS (flexible multibodymodel) and ANSYS (finite element modelof the carbody). Actual, measured trackirregularities are used asinput. In order to investigate the influence of passengerload,experimental modal analysis of the carbody is performed withand without passengers.Also, amplitude dependence is examined.Simple models, based on human-body modelsfrom literature, of thepassenger-carbody system are proposed and validated.Verticalseating dynamics is considered. The models areimplemented and tested in the casestudy. Finally, ideas on modelreduction and approximation are presented and applied.</p><p>The main conclusions drawn from the study are that</p><p>    the structural flexibility of the carbody must be takeninto account when predictingvertical vibration comfort. It ispossible to predict which carbody modes that willcontributemost to the vibrations.</p><p>    the carbody dynamical properties depend on the excitationamplitude.</p><p>    passengers and carbody interact significantly.- theproposed models describe the interaction quite well. Theproposed passenger-carbodymodel gives an upper boundary on theinteraction.</p><p>    the proposed passenger-seat-carbody model can be used tostudy the influence of theseat parameters on the interaction.This merits to be investigated further, however.</p><p><b>Keywords</b>: Carbody, Experimental modal analysis, Human-bodydynamics, Modelreduction, Multibody dynamics, Operatingdeflection shapes, Rail-vehicle dynamics,Ride comfort, Seatingdynamics, Structural dynamics.</p>

<p>An essential tool in the truck development process is the ability to quantify and grade vehicle dynamic behavior. Today this is performed either through subjective or objective tests. Subjective tests have the disadvantage that numerous factors influence test drivers’ opinions while objective measures have the advantage of repeatability. However, objective methods of today are often only able to provide a rough grading of vehicles. The main objective with this thesis is to develop more sensitive objective methods for ride comfort evaluation.</p><p>An effective test procedure to measure driver perception sensitivity to small differences in vehicle ride is suggested and utilized. The driver sensitivity is tested on dynamic behavior that is typically graded in vehicle development. Cab motions from a truck are first measured and then recreated in a simulator where a test driver is seated. The perception threshold for small changes in typical vehicle motion is established in this way for each test person.</p><p>The perception sensitivity tests indicate that humans are quite sensitive to transients in vehicle motion. One problem with many common vehicle ride measures is that the impact of transient behavior is small due to the averaging used to condense the measurement data into scalar measures. A new evaluation method for ride comfort, with influences from the well known handling diagram, is suggested. This method has four main advantages: it is fairly simple to interpret, it shows the absolute vibration level, it considers transient events separately and it shows changes in vehicle character with increasing excitation. Promising results from both measurements and simulations are derived.</p><p>New technology has made it possible to vary vehicle suspension parameters during vehicle ride. In order to prescribe different damping for different vehicle modes, modal motion estimates are needed. A system identification approach is suggested. It yields improved estimates of vehicle modal motion compared to previous work.</p>

To control the speed of an overactuated vehicle there may be many possible ways to use the actuators of the car achieving the same outcome. The actuators in an ordinary car is a combustion engine and a friction brake. In some cases it is trivial how to coordinate actuators for the optimal result, but in many cases it is not. The goal with the thesis is to investigate if it is possible to achieve the same or improved performance with a more sophisticated control structure than today's, using a model predictive controller. A model predictive controller combines the possibility to predict the outcome through an open-loop controller with the stability of a closed loop controller and gives the optimal solution for a finite horizon optimization problem. A simple model of the longitudinal dynamics of a car is developed and used in the model predictive controller framework. This is then used in simulations and in a real car. It is shown that it is possible to replace the current controller structure with a model predictive controller, but there are advantages and disadvantages with the new control structure.

Vehicle behaviour near the limit of adhesion is studied using linear optimal . control techniques and relatively simple vehicle models. Both time-invariant and time-varying approaches are used. Controllability is applied as a post-processing tool to analyse the resultant vehicle behaviour. First, a 4WS controller is developed using a linear time-invariant method, with a reference model control structure. Two handling objectives are defined, which are thought to provide predictable dynamics. Advantages of using a reference model control are clearly shown. With a developed control structure, it is shown that the prescribed target dynamics is achieved, provided tyre forces are available. It is also found that the controller is robust to small changes in the various vehicle parameter values. As a next step, time-varying modelling approach was used in order to better represent the vehicle operating conditions through the various dynamic range, including the limit of adhesion. An iterative vehicle path optimisation problem is formulated using a linear time-varying control approach. The validity of the optimisation method is studied against the steady-state simulation result at the limit of adhesion. It is shown that the method is capable of finding a trajectory in the vicinity of the friction limit, where the front tyres are used fully whilst retaining some margin at the rears. However, a couple of Issues are discovered. First, due to the quadratic nature of the road geometry cost function, the trajectory could get locked if the vehicle runs very close to the edge of the road. Hence, the . optimisation needs to be formulated such that the level of "optimality" on the trajectory remains consistent throughout the manoeuvre at each iteration. Secondly, it is found that inappropriate control demands are produced if the system matrix becomes poorly conditioned near the limit. This results in optimisation failure. In order to understand the mechanism of this failure, controllability of linear timevarying system was analysed and its properties were discussed in detail. First, the calculation methods of the controllability gramian matrix are investigated and some practical limitations are found. The gramian matrix is then used to define an open loop control sequence. It is found that the damping of the system has a significant influence on the control strategy. Subsequently, "the moving controllability window of a fixed time period" is found to provide the most relevant information of changing dynamics through the time. The study showed that the failure of the optimisation in the vicinity of the friction limit was indeed due to lack of controllability and the optimisation method itself was functioning correctly. The vehicle path optimisation problem is then extended to include longitudinal dynamics, enabling simulation of more general manoeuvres. The single corner simulation showed that the optimisation converges to an "out-in-out" path, with iterative solution improving continuously in a first order manner. Simulations with various controller settings showed that the strategy is reasonably robust provided that the changes in parameter settings are kept within a reasonable magnitude. It is also confirmed that the optimisation is able to drive a vehicle close to the limit under different types of operations required, i.e. braking, cornering and acceleration. The study was then performed with slightly more complex road geometry in order to investigate if the· optimisation is capable of prioritising certain· part of the manoeuvre in order to achieve better overall result. Unfortunately, this problem could not be solved successfully. The optimisation concentrated on the latter part of the manoeuvre as it had higher sensitivity to the final cost. This resulted in clearly sub-optimal overall performance. Finally, relatively simple study is conducted to investigate the correlation between various vehicle settings and optimisation results. Using the path optimisation problem formulation, iris found that the more oversteer vehicles are able to achieve better· result with more margin left in rear tyre force capacity. The handling objective functions used for the 4 WS controller is also calculated for the resultant trajectories. It is found that the neutral steer cost had a strong correlation, whereas the linearity cost showed no noticeable correlation. The controllability analysis was applied on the various vehicle settings using step steer simulation. It showed that more understeering vehicle retains higher controllability throughout the dynamics range. It is also found that higher inertia gives better controllability near the limit, however, it gives less controllability at more moderate operating conditions.

As vehicle dynamics research delves deeper into better insights in performance, modeling, and vehicle controls, one area remains of utmost importance: tire and road friction forces. The vehicle???s interaction with the road remains the dominant mean of vehicle control. Ultimately, the tire-road interaction will determine the majority of the vehicle???s capabilities and as the understanding of the interface improves, so too can the performance. With more computationally intensive systems being instrumented into modern vehicle systems, one is able to observe a great deal of important vehicle states directly for the remaining vehicle information; excellent estimation techniques are providing the rest of the insights. This study looks at the possible improvements that can be observed by implementing an adaptive dynamic tire model that is physical and flexible enough to permit time varying tire performance. The tire model selected is the Average Lumped LuGre Friction Tire Model, which was originally developed from physical properties of friction and tire systems. The material presented here examines the possibility of an adaptive tire model, which can be implemented on a real-time vehicle platform. The adaptive tire model is just one section of an entire control strategy that is being developed by General Motors in partnership with the University of Waterloo. The approach allows for estimated and measured vehicle information to provide input excitation for the tire model when driven with real-world conditions that enabling tire estimations. The tire model would then provide the controller information indicating the expected tire capacity and compares it with the instantaneous loading. The adaptive tire model has been tested with flat road experimental cases and the results provided reasonable estimates. The experimentation was performed with a fully instrumented research vehicle that used in-wheel force transducers, and later repeated with a completely different non-instrumented fully electric vehicle. The concepts and investigation presented here has initiated the ground work for a real-time implementation of a full adaptive tire model. Further work is still required to evaluate the influence of a range of operating conditions, tire pressure, and of different tire types. However, the findings indicate that this approach can produce reasonable results for the specified conditions examined.

Vehicle yaw stabilization and rollover prevention are two key factors in safety of vehicles. Designing a controller that can address both of the above safety concerns is of interest. In addition, it is essential that the performance of such a controller is evaluated properly. This can be done using a proper stability analysis. The above research problem is challenging for two reasons. First, maintaining both of the objectives, yaw stabilization and rollover mitigation, is contradictory at some instances, specifically when the vehicle is close to the verge of wheel lift-off. Second, the complexity of the dynamics of vehicle systems, which mostly arises from tire dynamics, makes the problems of controller design and stability analysis more challenging. In this Ph.D. thesis, a novel method for stability analysis of dynamical systems using the concept of Lyapunov exponents is proposed. The proposed method for stability analysis does not have the limitations of the current methods, and more specifically, can identify boundaries of the whole stability regions of attractors in a dynamical system. Furthermore, this method is computationally efficient and can be applied to general forms of nonlinear systems. The proposed stability analysis scheme is applied to the closed loop systems of ground vehicles with T-S fuzzy controllers for the purpose of evaluating and comparing the performance of the systems. The T-S fuzzy controllers integrate yaw stabilization and rollover avoidance. The ground vehicles that are studied in this research consist of torsionally flexible and torsionally rigid vehicles, which have differences in their dynamics because of the torsional compliance in their frames. The torsional compliance plays an important role in the dynamics, specifically for long vehicles, leading to different rollover indexes in the front and rear axles of the vehicles. The T-S fuzzy controllers are capable of prioritizing the contradictory objectives, and capturing all the essential complexities of dynamics of the systems. / February 2016

A capacidade de simulação nos atributos de dinâmica veicular tem crescido nos últimos anos, especialmente para os atributos de handling (manobrabilidade e estabilidade) e steering (dirigibilidade). Entretanto, as simulações de ride (em especial dos fenômenos de ride secundário) continuam muito dependentes de modelos sofisticados de pneus. Tais modelos devem ser capazes de simular fenômenos de freqüência mais alta tais como impacto e transmissibilidade de aspereza em três direções. Este trabalho apresenta uma abordagem semi-analítica para o problema de simulação de fenômenos de ride, através do uso de dados de medição em pista gerados através de transdutores de força (wheel force transducers, WFTs). Tais transdutores são tipicamente usados para fins de cascateamento de cargas e durabilidade. Através do uso de tais carregamentos, é possível simular fenômenos de ride em toda a faixa de frequência de estudo (até 8 Hz para ride primário e até 100 Hz para ride secundário) sem a necessidade de um modelo específico de pneu. Usando um modelo de veículo completo construído no software ADAMS, são apresentados dados de correlação com o veículo real e um estudo de caso através da alteração de propriedades de elementos tais como amortecedores, coxins e buchas de suspensão. / Vehicle dynamics CAE capabilities has increased in the past few years, specially, for handling and steering attributes. However, secondary ride simulations are still highly depended on the tire model. Such tire model must be capable to simulate high order phenomenon such as impact and harshness transmissibility in three directions. This dissertation presents a semi-analytical approach to the ride phenomena simulation problem, using data gathered via wheel force transducers (WFTs) that are typically used for load cascading and durability purposes. Using such load histories, it becomes possible to simulate ride phenomena through the whole typical ride frequency range (up to 8 Hz for primary ride and up to 100 Hz for secondary ride) without the necessity of using a special tire model. The results obtained from this approach using a complete car model developed using ADAMS software showed a very good correlation between measured data and simulations. Then on this work a case study using different properties for components such as shock abosrbers, engine mounts and suspension bushings is conducted in order to show the method\'s potential for ride optimization.