The purpose of this study is to evaluate potential travel time impacts of the implementation of exclusive heavy-vehicle lanes on the Interstate Highway 35 (IH 35) corridor, in the Austin metropolitan area. The analysis considers heavy vehicles (trucks) and non-heavy vehicles (cars) as separate system elements and as an integrated system. The study modeled traffic operations on IH 35, during the AM and PM peak hours, under two traffic scenarios, Existing and Inside Truck-Only Lanes using the software VISSIM 5.4. The limits of the study are FM 1431 in Round Rock, on the north, and SH 45 near Buda, on the south. The Existing scenario modeled traffic operations under current IH 35 geometric conditions and traffic control rules, in which trucks are prohibited from the inside lane and cars are allowed in all lanes. The Inside Truck-Only Lanes scenario modeled traffic operations under the assumption that trucks are restricted to the inside lane only and cars are prohibited from the inside lane. Travel times across the study area corridor were measured in the models to compare the performance of the Inside Truck-Only Lanes scenario relative to the Existing scenario. / text

With the new advancements in the vibration control strategies and controllable actuator manufacturing, the semi-active actuators (dampers) are finding their way as an essential part of vibration isolators, particularly in vehicle suspension systems. This is attributed to the fact that in a semi-active system, the damping coefficients can be adjusted to improve ride comfort and road handling performances. The currently available semi-active damper technologies can be divided into two main groups. The first uses controllable electromagnetic valves. The second uses magnetorheological (MR) fluid to control the damping characteristics of the system. Leading automotive companies such as General Motors and Volvo have started to use semi-active actuators in the suspension systems of high-end automobiles, such as the Cadillac Seville and Corvette, to improve the handling and ride performance in the vehicle. But much more research and development is needed in design, fabrication, and control of semi-active suspension systems and many challenges must be overcome in this area. Particularly in the area of heavy vehicle systems, such as light armored vehicles, little related research has been done, and there exists no commercially available controllable damper suitable for the relatively high force and large displacement requirements of such application. As the first response to these requirements, this thesis describes the design and modeling of an in-house semi-active twin-tube shock absorber with an internal variable solenoid-actuated valve. A full-scale semi-active damper prototype is developed and the shock absorber is tested to produce the required forcing range. The test results are compared with results of the developed mathematical model. To gain a better understanding of the semi-active suspension controlled systems and evaluate the performance of those systems, using perturbation techniques this thesis provides a detailed nonlinear analysis of the semi-active systems and establishes the issue of nonlinearity in on-off semi-active controlled systems. Despite different semi-active control methods and the type of actuators used in a semi-active controlled system, one important practical aspect of all hydro-mechanical computer controlled systems is the response-time. The longest response-time is usually introduced by the actuator –in this case, controllable actuator – in the system. This study investigates the effect of response-time in a semi-active controlled suspension system using semi-active dampers. Numerical simulations and analytical techniques are deployed to investigate the issue. The performance of the system due to the response-time is then analyzed and discussed. Since the introduction of the semi-active control strategy, the challenge was to develop methods to effectively use the capabilities of semi-active devices. In this thesis, two semi-active control strategies are proposed. The first controller to be proposed is a new hybrid semi-active control strategy based on the conventional Rakheja-Sankar (R-S) semi-active control to provide better ride-handling quality for vehicle suspension systems as well as industrial vibration isolators. To demonstrate the effectiveness of this new strategy, the analytical method of averaging and the numerical analysis method are deployed. In addition, a one-degree-of-freedom test bed equipped with a semi-active magnetorheological (MR) damper is developed. The tests are performed using the MATLAB XPC-target to guarantee the real-time implementation of the control algorithm. The second controller is an intelligent fuzzy logic controller system to optimize the suspension performance. The results from this intelligent system are compared with those of several renowned suspension control methods such as Skyhook. It is shown that the proposed controller can enhance concurrently the vehicle handling and ride comfort, while consuming less energy than existing control methodologies. The key goal of this thesis is to employ the existing knowledge of the semi-active systems together with the new ideas to develop a semi-active suspension system. At the same time, development of an experimental simulation system for real-time control of an experimental test bed is considered. To achieve its goals and objectives, this research study combines and utilizes the numerical simulations and analytical methods, as well as lab-based experimental works. The challenge in this research study is to identify practical and industrial problems and develop proper solutions to those problems using viable scientific approaches.

With the new advancements in the vibration control strategies and controllable actuator manufacturing, the semi-active actuators (dampers) are finding their way as an essential part of vibration isolators, particularly in vehicle suspension systems. This is attributed to the fact that in a semi-active system, the damping coefficients can be adjusted to improve ride comfort and road handling performances. The currently available semi-active damper technologies can be divided into two main groups. The first uses controllable electromagnetic valves. The second uses magnetorheological (MR) fluid to control the damping characteristics of the system. Leading automotive companies such as General Motors and Volvo have started to use semi-active actuators in the suspension systems of high-end automobiles, such as the Cadillac Seville and Corvette, to improve the handling and ride performance in the vehicle. But much more research and development is needed in design, fabrication, and control of semi-active suspension systems and many challenges must be overcome in this area. Particularly in the area of heavy vehicle systems, such as light armored vehicles, little related research has been done, and there exists no commercially available controllable damper suitable for the relatively high force and large displacement requirements of such application. As the first response to these requirements, this thesis describes the design and modeling of an in-house semi-active twin-tube shock absorber with an internal variable solenoid-actuated valve. A full-scale semi-active damper prototype is developed and the shock absorber is tested to produce the required forcing range. The test results are compared with results of the developed mathematical model. To gain a better understanding of the semi-active suspension controlled systems and evaluate the performance of those systems, using perturbation techniques this thesis provides a detailed nonlinear analysis of the semi-active systems and establishes the issue of nonlinearity in on-off semi-active controlled systems. Despite different semi-active control methods and the type of actuators used in a semi-active controlled system, one important practical aspect of all hydro-mechanical computer controlled systems is the response-time. The longest response-time is usually introduced by the actuator –in this case, controllable actuator – in the system. This study investigates the effect of response-time in a semi-active controlled suspension system using semi-active dampers. Numerical simulations and analytical techniques are deployed to investigate the issue. The performance of the system due to the response-time is then analyzed and discussed. Since the introduction of the semi-active control strategy, the challenge was to develop methods to effectively use the capabilities of semi-active devices. In this thesis, two semi-active control strategies are proposed. The first controller to be proposed is a new hybrid semi-active control strategy based on the conventional Rakheja-Sankar (R-S) semi-active control to provide better ride-handling quality for vehicle suspension systems as well as industrial vibration isolators. To demonstrate the effectiveness of this new strategy, the analytical method of averaging and the numerical analysis method are deployed. In addition, a one-degree-of-freedom test bed equipped with a semi-active magnetorheological (MR) damper is developed. The tests are performed using the MATLAB XPC-target to guarantee the real-time implementation of the control algorithm. The second controller is an intelligent fuzzy logic controller system to optimize the suspension performance. The results from this intelligent system are compared with those of several renowned suspension control methods such as Skyhook. It is shown that the proposed controller can enhance concurrently the vehicle handling and ride comfort, while consuming less energy than existing control methodologies. The key goal of this thesis is to employ the existing knowledge of the semi-active systems together with the new ideas to develop a semi-active suspension system. At the same time, development of an experimental simulation system for real-time control of an experimental test bed is considered. To achieve its goals and objectives, this research study combines and utilizes the numerical simulations and analytical methods, as well as lab-based experimental works. The challenge in this research study is to identify practical and industrial problems and develop proper solutions to those problems using viable scientific approaches.

Esse trabalho visa a estudar os efeitos dinâmicos provocados por um veículo classe 3C em uma ponte de concreto de seção unicelular, com curvatura em planta, por meio da modelagem do veículo, do pavimento, das forças de interação veículo-pavimento e da estrutura. Partiu-se do modelo do veículo com nove graus de liberdade, considerando o desacoplamento dos esforços longitudinais de interação dos esforços transversais (força de inércia centrífuga). Foram calculados os carregamentos provenientes do veículo modelado, primeiramente sobre tabuleiro rígido indeslocável, considerando as irregularidades geométricas apresentadas no pavimento, com perfis iguais ou distintos sobre cada linha de pneus. Estes carregamentos foram condensados estaticamente e aplicados em um modelo estrutural simplificado (\'unifilar\') de uma ponte em seção unicelular. Utilizou-se um método iterativo para a obtenção dos esforços de interação, até se alcançar a convergência. Ainda foram confrontados resultados para duas situações de tráfego, sendo a primeira para veículo isolado trafegando sobre a estrutura e a segunda para um comboio de veículos. Por fim, as respostas dinâmicas obtidas da interação veículo-estrutura do modelo foram comparadas com uma resposta quase-estática, para a obtenção dos coeficientes de amplificação dinâmica. / This dissertation aims at studying the dynamic effects produced by a 3C class vehicle on a curved concrete bridge with box girder section, by modelling the vehicle, the roughness profile, the bridge-vehicle interaction forces and the structure. It started from a model with nine degrees-of-freedom, considering the uncoupling of the longitudinal interaction forces of the transversal forces (centrifugal force of inertia). The loads are evaluated for the vehicle model travelling, firstly on a rigid uneven pavement, considering equal and different roughness profiles under the tires. These loads are statically condensed at the centre of gravity of the car and applied to a simplified (\'unifilar\') structural model of a concrete bridge with box girder section. An iterative method has been used to obtain the interaction forces until the convergence could be achieved. Furthermore, the results for two traffic situations were compared, the first being when a single vehicle is traveling along the structure, whereas the second refers to a train of vehicles. Finally, the dynamic response obtained from the bridge-vehicle interaction was compared with a quasi-static response, allowing for the evaluation of the dynamic amplification coefficients.

Os ensaios acelerados de pavimentos em escala real consistem na aplicação controlada de uma carga de roda igual ou acima da carga máxima legal permitida, em uma estrutura de pavimento, seja este um pavimento-teste ou uma via existente, para se determinar a resposta do sistema e o seu desempenho sob condições controladas e aceleradas de acúmulo de danos num espaço limitado de tempo (METCALF, 1996). Esses ensaios podem ser realizados hoje, tanto por simuladores instalados em campos de prova destinados a este único fim, quanto por simuladores móveis, cuja composição é rebocável ou autopropelida e pode ser posicionada no local a ser pesquisado, o que se mostra especialmente vantajoso no estudo de materiais e técnicas de restauração de pavimentos por preservar as condições de contorno. Apresentam-se os resultados dos primeiros testes acelerados em pavimentos com simulador de tráfego linear móvel no Brasil e suas contribuições para o desenvolvimento das técnicas, processos de projeto e planejamento rodoviários. Apresenta-se também uma síntese dos ensaios acelerados de pavimentos em escala real com simuladores de tráfego lineares móveis, com o objetivo de mostrar o estágio atual do conhecimento nessa área, a partir de uma revisão bibliográfica e associando esses conhecimentos a casos práticos. Como contribuição para futuros trabalhos, com base na análise das pesquisas já finalizadas e dos resultados já obtidos, foi elaborada uma proposta de método para a realização de simulação em pista e de ensaios a serem conduzidos antes, durante e após o término da simulação, dependendo do objetivo específico dos ensaios acelerados. / Full-scale accelerated pavement testing is defined as the controlled application of a wheel load in a pavement structure to determine the pavement system response and its performance under accelerated conditions of accumulated damage in a compressed time period (METCALF, 1996). Loads at or above the legal maximum allowed by highway agencies can be applied at test tracks, using simulators designed solely for this purpose, or at existent roads using mobile simulators positioned right at the road pavement structure. This layout provides an interesting advantage in the study of materials and pavement rehabilitation techniques by preserving field conditions, specially structural and environmental characteristics. This research describes the results from the first accelerated pavement tests with mobile linear traffic simulator in Brazil and their contribution for the development of design procedures, distress monitoring methods, and road planning. As part of this research, a wide literature review was done associated with practical case studies, the current stage of knowledge in this area, and a real scale synthesis of accelerated pavement experiments with linear mobile traffic simulators. This research proposes a simulation method for testing pavement sections and the evaluation tests to be performed according to the objective of the accelerated pavement test study. This research is a contribution to the state of practice of this type of accelerated pavement testing in Brazil and outlines the path for future applications of this technology in the country.

This thesis investigates passive damping system performance in heavy vehicles through analytical expressions, simulations with different vehicle models as well as through experimental evaluation in a tractor semi trailer combination. The objective is to study what levels of chassis suspension damping that are desirable for different vehicle modes and how this may be achieved with passive damping systems. To investigate the influence on performance from damper positioning, analytical expressions for a 2D - suspension model are derived. Geometric key parameters controlling roll and bounce damping are found to be damper vertical aligning and perpendicular distance between damper and suspension roll centre respectively. These parameters are often not easily altered within an already existing vehicle. To investigate performance possibilities from damping not restricted by packaging requirements, the concept with distributed damping is furthermore studied. Theoretical expressions for modally distributed damping are first derived from an analytical tractor model with 7 DOF. Considered motions for which damping is prescribed are bounce, pitch and roll of sprung mass, and axle crossing. These equations are evaluated through various simulations with a 4x2-tractor semi trailer model. Results from simulations show that the conflict in damping demands with passive independent dampers for a single lane change and a one-sided pot hole may be significantly reduced with amplitude dependent modal damping. Vehicle damping performance is not only affected by the dampers positioning and their individual setting, but also by the damper attachment structure. The influence from compliance in e.g. brackets and mounting bushings at damper attachment points is therefore studied. Linear analysis with a simple spring mass damper model shows that damper attachment compliance reduces the damper efficiency. Finite element analyses of both the chassis frame and the tractor are furthermore performed to obtain numerical values of front-axle damper-attachment stiffness. The effect from damper-attachment stiffness is quantified though simulations with a tractor semi trailer model. Simulation results show that it is important to consider the attachment stiffness during vehicle manoeuvres containing high frequency inputs such as the passage over a plank. A methodology and equations for prescribing chassis suspension damping as function of general vehicle modes by using electronically controlled variable dampers is presented. A critical input for such implemented modal damping systems are the real time estimation of modal motions necessary for force calculation. From performed simulations it is shown that geometric calculations of modal velocities based solely on relative damper displacements contain significant discrepancies to actual motion for transient road inputs. To overcome this, a time-domain system identification approach is presented, where models that estimate modal coordinate velocities with considerably higher accuracy are identified. The proposed modal damping approach is implemented on a 4x2 tractor and experimentally evaluated through various road tests. It is shown that the system has the desired ability to control sprung mass bounce and pitch modes separately and that it improves vehicle performance on all tested load cases. / QC 20100830

This research presents an investigation to actively improve the rollover stability of articulated heavy vehicles (AHVs) during high speed manoeuvres using anti-roll control systems. A 3-dimensional (3-D) linear yaw/roll model with 5 degrees of freedom is developed. Based on this model a linear quadratic regulator (LQR) controller is designed to improve the rollover stability of a tractor/semi-trailer combination. A design optimization method for AHVs using genetic algorithms (GAs) and multibody vehicle system models is also presented. AHVs have poor manoeuvrability when travelling at low speeds on local roads and city streets. On the other hand, these vehicles exhibit unstable motion modes at high speeds, including jack-knifing, trailer sway and rollover. From the design point of view, the low-speed manoeuvrability and high-speed stability have conflicting requirements on some design variables. The design method based on a GA and a multibody vehicle dynamic package, TruckSim, is proposed to coordinate this trade-off relationship. To test the effectiveness of the design method, a tractor/semi-trailer combination is optimized using the proposed method. It is demonstrated that the proposed design method can be used for identifying desired design variables and predict performance envelopes in the early design stages of AHVs. / UOIT

A new design synthesis method for articulated heavy vehicles (AHVs) with an active trailer steering (ATS) system is examined and evaluated. Due to their heavy weights, large sizes, and complex configurations, AHVs have poor maneuverability at low speeds, and low lateral stability at high speeds. Various passive trailer steering and ATS systems have been developed for improving the low-speed maneuverability. However, they often have detrimental effects on the high-speed stability. To date, no systematic design synthesis method has been developed to coordinate the opposing design goals of AHVs. In this thesis, a new automated design synthesis approach, called a Single Design Loop (SDL) method, is proposed and investigated. The SDL method has the following distinguished features: 1) the optimal active design variables of ATS systems and the optimal passive vehicle design variables are searched in a single design loop; 2) in the design process, to evaluate the vehicle performance measures, a driver model is developed and it „drives‟ the vehicle model based on the well-defined testing specifications; and 3) the ATS controller derived from this method has two operational modes: one for improving the lateral stability at high speeds and the other for enhancing path-following at low speeds. To demonstrate the effectiveness of the new SDL method, it is applied to the design of an ATS system for an AHV with a tractor/full-trailer. In comparison to a conventional design approach, the SDL method can search through solutions in a much larger design space, and consequently it provides a more comprehensive set of optimal designs.. / UOIT

Multi-body system dynamics is one of the most important theoretical achievementsin mechanics. With the development of the theory, corresponding commercialsoftware packages have been developed and are used for modellingand simulation of complicated large systems, such as air planes and vehicles.This kind of virtual prototypes can be used for studies and assessments ofreal systems even before the real systems are built. As a result, the high costprototype building and prototype testing can be saved, so as the time can bereduced. This is just the demand of modern industry. This theory can beapplied on the vehicle-virtual road interaction study which has been used inthis thesis.This thesis suggests a target velocity prole for a heavy vehicle which driveson tough road. Having uneven and hilly road, actual driving conditions arechanged as the driver runs the vehicle. Drivers can perceive the road conditionwith their visual organ and sense of balance and then they control theirvehicles more safely by re ecting various conditions of this target velocityprole. Without this process, the driving-stabilization on slope and twistingroads would fall considerably, and the problem could be directly connected tooverturning. This thesis, moreover, will show how to acquire the road data,extract the velocity prole, and verify the performance of the suggested velocityprole through virtual road test.In vehicle-virtual road interaction simulation, multi body system (MBS) dynamicswith software Adams has been employed to model an articulatedhauler. The simulation has been validated by velocity prole test data andcompared to the former velocity prole. This method can be used for estimatingthe eects of dynamic forces on the frame so that the load design canbe assessed in vehicle design process.This project is in collaboration with Volvo Construction Equipment AB,Braas, Sweden.

Increasing demand for road freight has lead to a widespread adoption of more-productive large freight vehicles (LFVs), such as B-Doubles, by Australia's road freight industry. Individual LFVs have a greater potential to impact traffic efficiency through their greater length and poorer longitudinal performance. However, this is offset to an extent as fewer vehicles are required to perform a given freight task on a tonne-km basis. This research has developed a means of characterising the effects that large freight vehicles have on the performance of an urban arterial corridor managed by signalised intersections. A corridor-level microsimulation model was developed from first principles, which modelled the longitudinal performance of individual vehicles to a greater accuracy than most existing traffic simulation software does. The model was calibrated from traffic counts and GPS-equipped chase car surveys conducted on an urban arterial corridor in Brisbane's southern suburbs. The model was applied to various freight policy and traffic management scenarios, including freight vehicle mode choice, lane utilisation and traffic signal settings; as well as the effectiveness of green time extension for approaching heavy vehicles. Benefits were able to be quantified in terms of reduced travel times and stop rates for both heavy and light vehicles in urban arterial corridors.