Orientador: Alberto Luiz Serpa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-25T19:19:54Z (GMT). No. of bitstreams: 1 DalPoggetto_ViniciusFonseca_M.pdf: 3071480 bytes, checksum: 896f4f9551e83a320f201a09e0bf73e3 (MD5) Previous issue date: 2014 / Resumo: Muitos trabalhos foram desenvolvidos na área de controle aplicados à dinâmica veicular, visando reduzir a possibilidade de ocorrência do tipo de acidente classificado como tombamento. Nesse trabalho, a partir de um modelo não-linear comumente utilizado, estudou-se a aplicação de uma estratégia de controle LQR utilizando estados estimados. Assim, desenvolvendo as equações dinâmicas e modelagem de controladores e observadores, pode-se comparar a eficácia dessa estratégia de controle utilizando simulações lineares e não-lineares. Foram obtidos resultados significativos na redução do coeficiente de tombamento para manobras em diferentes velocidades, indicando vantagens no uso desse tipo de controle nos casos simulados / Abstract: Many researches have been developed in the area of control applied to vehicle dynamics, aiming at reducing the possibility of the ocurrence of the type of accident known as rollover. In this research, based on a commonly used nonlinear model, the objective is to study the application of a LQR control strategy using estimated states. By developing the dynamic equations and modeling of controllers and observers, one may compare the efficacy of this control strategy using both linear and nonlinear simulations. Significative results were obtained regarding the reduction of the rollover coefficient for maneuvers at different speeds, thus indicating advantages in using this controller in the simulated cases / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Abstract Over recent years the progress in actuator and microelectronics technology has made intelligent suspension systems feasible. These systems are designed to reduce the drivers' exposure to harmful vibration, as well as to improve the handling properties of the vehicle. Due to widespread use of vehicles as an example of a true MIMO-system, a myriad of different control schemes and algorithms can be found in the literature for these systems. Linearized models are commonly used when the control algorithms are derived. This thesis describes the development of a new analytical full vehicle model, which takes the essential kinematics of the suspension system into account, as well as a new approach to controlling the full vehicle vibration problem. The method of calculating the desired damping forces for each of the semi-active actuators is based on the skyhook theory and this new model is introduced. The performance of the control schemes is evaluated with simulations in a virtual environment. For the excitation to the vehicle, standardized ISO-tracks, washboard tracks and single bump tracks were used. The performance between the two different semi-active control systems and the passive system are compared in terms of damping the vibration, variation of the dynamic tire load and demand for rattlespace. The damping of vibration evaluates both the ability to suppress the vibration on heave, pitch and roll degrees of freedom and ability to reduce the drivers' exposure to harmful whole body vibration. The frequency distribution of the vibration was also reviewed. Variation of dynamic tire contact force is evaluated as an RMS-value and the demand for rattlespace is evaluated as a percentage value of the used rattlespace compared to the maximum free stroke provided by the suspension hardware. As a result from this work, the theory and simulation results are presented. Also a new vehicle model, which takes the essential non-linearity caused by suspension kinematics into account, is presented including all the mathematics needed. The comparison between the passive and the semi-active concepts has been performed on the basis of simulation results. These results show that the novel semi-active concept reduces the driver's exposure to vibration induced by terrain undulations better than any earlier proposed version. Also variation of dynamic tire load is reduced with a novel concept, while it suffers a drawback in the demand for the rattlespace.

This study is focused on modifying an existing solenoid valve based semi-active hydropneumatic spring-damper system using Magneto-Rheological (MR) fluid. The MR fluid's effective viscosity can be altered by application of a magnetic field. Therefore, using a magnetic/ MR valve makes it possible to change the state of the system by simply changing the applied magnetic field. A prototype MR valve was developed to determine whether a unit small enough for installation was possible. This prototype valve was designed from first principles and properties such as pressure drop over the valve (damping) and flow blocking (for switching between spring characteristics) were measured. The measured pressure drop over the valve was higher than what was design for which was due to an incorrect assumption for the viscosity of the thixotropic MR Fluid. The flow blocking ability of the valve was determined by constant force tests. Results showed that the valve could virtually block the flow of fluid for approximately a quarter of the vehicles weight. With the second prototype, the valve design and magnetic circuit design were improved. Two valves were constructed and implemented on a prototype suspension system. The damping characteristics of the system were lower than expected, however they can be improved by changing the valve geometry. The base spring characteristics are acceptable, however the higher spring characteristics fail when a high force is exerted on the strut that exceeds the valves flow blocking capability. The response time of the valve is not yet sufficient to make the system viable for real world implementation, especially under extreme conditions that can change more rapidly than the current valves. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

In an effort to reduce physical testing during the development process of a new vehicle, the automotive industries develop methods that can facilitate the recreation of the physical testing scenarios in virtual environments using simulation software. This thesis aims to develop a method which would help evaluate the vehicle’s dynamic properties without it being subjected to physical testing. The goal is to develop a tool that can be used in an early development phase by the industry and that would allow for modifications and calibration to take place. A vehicle model as well as an electronic stability control implementation is built, and the model’s performance to an ISO3888 part-2 double lane change test is evaluated. Since the handling potentials of the vehicle are rated by its entry speed in that test, the model was subjected to an optimization process where its steering action was controlled in order to achieve the highest possible entry speed to the test in an effort to isolate the vehicle’s dynamic potential from the influence of a human driver when conducting this test. The vehicle modelling procedure is done in steps, from a simple implementation of a linear bicycle model to a more complex implementation of a four-wheel vehicle including roll, tire relaxation and suspension compliance properties as well as a simplified ESC implementation. The results of the steering input optimization process were physically tested on a test track, where the correspondence of the model to the real vehicle was evaluated. By further promoting the vehicle dynamics modelling, this tool can facilitate study more testing scenarios and options and it can serve as a step toward the reduction of the physical testing when the vehicle’s dynamic and handling performance need to be studied and evaluated. / Under utvecklingsprocessen av nya fordon sker en strävan mot att reducera fysiska tester, bilindustrier utvecklar därför metoder för att återskapa fysiska testscenarier i virtuella miljöer med hjälp av simuleringsmjukvara. Denna studie har som målsättning att utveckla en metod, med vilken fordonets dynamiska egenskaper kan utvärderas utan att utföra fysiska tester. Målet är att utveckla ett simuleringsverktyg som, i en tidig utvecklingsfas, kan användas av fordonsindustrin och som skulle införa både modifikations- och kalibreringsmöjligheter i detta skede. Såväl en fordonsmodell som ett anti-sladd system är konstruerat och modellens prestanda i ett dubbelt filbyte, specificerat i ISO3888 del 2, är utvärderad. Då bilens dynamiska prestanda klassificeras utifrån ingångshastigheten i detta test utfördes en optimeringsprocess där hjulens styrvinklar reglerades för att uppnå högsta möjliga hastighet vid testets startposition, detta för att separera fordonets dynamiska klassificering från mänsklig inverkan. Processen att konstruera fordonsmodellen utfördes med succesivt ökande antal av fordonsegenskaper, från en enkel implementering av en linjär cykel-modell till en tvåspårs-modell med krängning, transienta däckegenskaper, hjulupphängningsegenskaper samt ett anti-sladd system. Resultatet av den optimerade styrregleringen testades i motsvarande fordon på en testbana varefter modellen kunde utvärderas med det verkliga testet som referens. Genom en utökad möjlighet till simulering kan detta verktyg ge möjligheten att studera fler scenarier såväl som alternativa modelleringskonfigurationer; det kan reducera fysiska tester då fordons dynamiska prestanda ska klassificeras, studeras samt utvärderas.

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The state-of-the-art traffic simulation packages model traffic on a microscopic level. This includes the use of several sets of models that dictate how traffic moves within a transportation network. These models include car-following, gap acceptance, lane-changing and route choice models. The aim of this thesis is to improve the treatment of vehicle dynamics in traffic simulation and, as a result, special attention was paid to car-following models. These models were highlighted because they are largely responsible for capturing a vehicle’s motion and its relevant dynamics in traffic simulation. In order to improve the treatment of vehicle dynamics in traffic simulation, a Dynamic-Interactive-Vehicle (DIV) model was developed. This vehicle model is calibrated with the use of essential vehicle performance specifications that are responsible for the movement of a vehicle in a transportation network. After the calibration process the model is able to accept three inputs from a driver – gas pedal, brake pedal and steering wheel positions. The model then outputs the corresponding longitudinal and latitudinal values which represent the movement of a vehicle along a roadway. The vehicle model will also account for most of the dominant external forces that affect an automobile’s performance along a roadway. This thesis will validate the proposed model by comparing its output from a few performance tests with the performance test results of three passenger cars. The DIV model was validated by comparing the acceleration, braking and steering performance test results of three passenger cars with the output from the DIV model upon performing similar tests. It was found that the DIV model was successful at replicating the two-dimensional vehicle motion.

This research effort first characterizes the trucks traveling along US highways by analyzing data from Interstate 81. It is hypothesized that I-81 is typical of US highways and thus can provide some insight into typical truck characteristics. These truck characteristics are important for the development of an exhaustive vehicle performance procedure. Analysis was done based on data collected at the Troutville weigh station. The characterization involves an analysis of vehicle class distribution, GVW (Gross Vehicle Weight) distribution, vehicle volume distribution, Average Weight on Tractive Axle (AWTA), and typical weight-to-power ratios. The thesis then assembles a database of systematic field data that can be utilized for the validation of vehicle performance models. This database is unique because it was conducted in a controlled field environment where the vehicle is only constrained by its dynamics. Using the assembled field database, a simple constant power vehicle dynamics model for estimating maximum vehicle acceleration levels based on a vehicle's tractive effort and aerodynamic, rolling, and grade resistance forces was tested and validated. In addition, typical model input parameters for different vehicle, pavement, and tire characteristics are included in the thesis. The model was found to predict vehicle speeds at the conclusion of the travel along the section to within 5 km/h (3.1 mi/h) of field measurements, thus demonstrating the validity and applicability of the model. Finally, the research effort introduces the concept of variable power in order to enhance current state-of-the-art vehicle dynamics models and capture the build-up of power as a vehicle engages in gearshifts at low travel speeds. The proposed enhancement to the current state-of-practice vehicle dynamics model allows the model to reflect typical vehicle acceleration behavior more accurately. Subsequently, the model parameters are calibrated using field measurements along a test roadway facility. / Master of Science

Rolling resistance is a considerable factor in energy consumption for all rolling vehicles. A proper understanding of the phenomenon is an important aspect in order to design energy efficient vehicles. The literature study focus on three main aspects to describe the phenomenon; tire material and its properties, tire components and their effect on tire behavior concerning rolling resistance, and finally the effect of operating conditions on tire behaviour is considered. 58 resources have been studied and summarised in order to make a comprehensive literature study of the rolling resistance phenomenon.

Automated driving systems (ADS) are projected to bring a plethora of benefits to society, such as enhanced road safety and heightened quality of life. However, placing one's trust in the hands of an automated system is still a large concern to society. To facilitate the large-scale adoption of ADSs, they must be stringently tested and evaluated prior to their deployment on public roadways due to their direct impact on the safety of other motorists and vulnerable road users. Currently, no standardized method of quantifying ADS performance exists, so this research project contributes to the evaluation of ADSs by developing and demonstrating a test method that solely characterizes the motion control subsystem of an ADS. The developed test method involved generating representative driving scenarios that exercised both the longitudinal and lateral control elements of an ADS. This method was then demonstrated using two test vehicles with different control system architectures by (1) defining and injecting a ground truth trajectory into the ADS, (2) characterizing the motion control subsystem by quantifying its ability to follow the ground truth path under both nominal conditions and conditions where disturbances were introduced, and (3) analyzing the response of each vehicle to characterize their respective control systems as well as identify differences between the two control architectures. First, a set of representative driving scenarios was created to test the longitudinal and lateral control elements both in isolation and in tandem. Multiple unique design variations of each scenario were created by implementing various target speeds, accelerations, and turning radii that map to both standard and emergency maneuvers. The parameters were set to match naturalistic driving or regulatory requirements identified as part of a literature review. Next, a reference trajectory—the ground truth set of waypoints that define the position and speed of the ADS—was generated for each driving scenario. This reference trajectory was implemented using three methods: recording the waypoint trail of a human driver and creating a synthetic waypoint list mathematically or with CarMaker, a simulation platform for automobile testing (IPG Automotive 2021). Once this step was completed, the reference trajectory was inserted into the ADS to isolate the motion control system and facilitate a repeatable test input. When the test vehicle was under ADS control, the experimenter served as the designated fallback user so they could take control of the vehicle if necessary. Finally, a set of test metrics related to the operation of the ADS (lateral offset, heading error, speed error, longitudinal stop position error, and test completion percentage) were calculated using kinematic data to characterize each motion control system architecture. The analysis of the kinematic metrics for each test scenario demonstrated that the method could effectively evaluate the performance of ADS in various scenarios and highlight the strengths and weaknesses of each system. The control system of Vehicle A consistently lagged in throttle and brake actuation and rounded corners by turning early and with a larger cornering radius. This control system also could not exceed a lateral acceleration of 3.5 m/s2 when under ADS control and limited its yaw rate to keep the lateral acceleration below this level. Consequently, this limitation caused the vehicle to turn wide for radius and speed combinations with a lateral acceleration greater than 3.5 m/s2. On the other hand, the control system of Vehicle B consistently exhibited a small delay before turning and tended to overshoot lane changes at higher lateral accelerations. Regarding disturbances, only the road grade significantly affected the response of both vehicles. / Master of Science / Automated driving systems (ADS) are projected to improve road safety and quality of life, but they must be comprehensively tested and evaluated before their deployment on public roadways. Currently, no standardized method of quantifying ADS performance exists, so this research project contributes to the evaluation of ADSs by developing and demonstrating a test method that identifies limitations of two dissimilar ADS motion controllers. First, real-world driving scenarios were used to test the longitudinal (throttle/brake) and lateral (steering) control elements both in isolation and in tandem. Multiple levels of maneuver harshness were tested to simulate both standard and emergency maneuvers, and these levels were determined by conducting a literature review of human driving behavior. Roadway and vehicle disturbances were also implemented to investigate if the control systems could adjust for external factors. Next, a reference path was generated for each driving scenario using three separate methods, and once this was done, the vehicle attempted to follow the reference path. Finally, a set of test metrics related to the path-following ability of the ADS were calculated, and this data was used to characterize each motion control system architecture. The analysis of metrics demonstrated that the method could effectively evaluate the performance of each control system by highlighting their weaknesses. The control system of Vehicle A consistently accelerated and braked late as well as rounded corners by turning early and with a larger radius. This control system also could not complete harsh cornering maneuvers. On the other hand, the control system of Vehicle B consistently turned late and tended to overshoot lane changes, especially those with a higher speed or harsher steering maneuver. Regarding disturbances, only the road grade significantly affected the response of both vehicles.

Artificial satellites play a vital role throughout the world today. They providea broad range of services ranging from navigation to communication and reconnaissance. As antenna technology is evolving and ground based antennas are getting smaller and smaller, the demand for on-the-move solutions is growing.These antennas can be used whilst mounted on for example, a moving vehicle,where the mechanical performance of the antenna must be sufficient for thecurrent conditions. During this project, a computer based tool that can helpengineers when iterating and optimizing a two-axis gimbal type antenna designwas created. The tool uses simulated and recorded data from road vehicles andboats to calculate the required torque on the two axes necessary to sustain communication with a geostationary satellite. When completed, the tool was easy to use and configure whilst not requiring much computational power. / Artificiella satelliter har en viktig roll i dagens samhälle. De gör att en radtjänster så som navigation, kommunikation och spaning är tillgängliga på ettsätt som annars ej vore möjligt. Samtidigt som antenner blir mindre och lättareså ökar efterfrågan på så kallade on-the-move-lösningar. Dessa antenner kananvändas under färd och ofta på fordon av olika slag. För sådana antenner är detviktigt att den mekaniska prestandan är tillräcklig för de rådande förhållandena.I detta projekt har ett datorbaserat verktyg som kan hjälpa ingenjörer att itereraoch optimera en tvåaxlig inpekare utvecklats. Verktyget använder simulerad ochinsamlad data från markfordon och båtar för att beräkna de vridmoment sombehövs på vardera axel for att bibehålla kommunikation med en geostationärsatellit. Det färdiga verktyget är enkelt att använda och konfigurera utan attkräva stor beräkningskraft.