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The Rail Vehicle Research group at Kungliga Tekniska Högskolan (KTH) is on the path to design and build a scaled test rig called roller rig for research and educational purposes. A roller rig is a device simulating the track with rollers on which the test subject (a wheelset, bogie or even a full vehicle) canbe placed.This thesis report is part of a bigger project involving several team members and it explores the applicability of track irregularities on a scaled roller rig by means of computer simulations. A scaled roller rig model, capable of simulating track irregularities, is generated using the multibody simulation softwareSIMPACK. Track irregularity data, represented as Power Spectral Densities (PSD), are applied to the model created. The model created and implementation of track irregularities are assessed in order to validate the modelling steps.Comparison with a reference vehicle model is carried out to verify if results obtained on the test rig are representative of a vehicle running on track, taking into account roller rig intrinsic errors. Results obtained aim to support the design of the roller rig’s mechanical components from a dynamical standpoint. / Forskargruppen spårfordon på Kungliga Tekniska Högskolan (KTH) arbetar med att designa och bygga en nedskalerad testrigg, en så kallad rullrigg, iforsknings- och utbildningssyfte. En rullrigg är en apparat avsedd att efterlikna järnvägsspåret med hjälp av cylinderhjul, på vilken testsubjektet (hjulaxel, boggi eller ett helt fordon) kan placeras.Denna rapport är en del av ett större projekt som involverar ett flertal gruppmedlemmar och undersöker tillämpligheten av spårlägesfel på en nedskalerad rullrigg med hjälp av simulationer. En nedskalerad rullrigg, kapabel att återskapa spårlägesfel, genereras med flerkroppsdynamik mjukvaran SIMPACK. Data för spårlägesfel, representerade med spektraltätheter (PSD), appliceras på den skapade modellen. Modellen samt implementering av spårlägesfelen bedöms sedan för att validera modelleringens steg.Jämförelse med en referensfordonsmodell genomförs för att verifiera att erhållna resultat från testriggen är representativ för ett verkligt spårfordon, med hänsyn tagen till rullriggens inneboende fel. Erhållna resultat syftar till att stödja utformningen av rullriggens mekaniska komponenter från ett dynamiskt perspektiv.

Before vehicles can be placed in service it has to complete an authorisation process. At the moment,this process is largely depended on tests. This is, however, an expensive and long process. With new technologies and improved simulations this process can be shortened and the costs can be lowered. The validation of a vehicle model, however, is often limited by the available data. Often the measured rail profiles are not available and thus a new UIC60 profile is used for the simulations. The railway track often has been used and showssigns of wear and damages, therefore research has been done to investigate the influence of the rail profiles on the validation of a railway vehicle model. The current methods of validation in the European norm are used to compare simulated values with forces and accelerations available from vehicle measurements. In the first step,25 track sections with different curve radii have beensimulated with a measured rail profile every 100 meters. In the next step, the same sections have been simulated by using the standard UIC60 rail profile. The results show that the use of measured rail profiles does have a positive influence on the outcome of simulation. In the final step, one single narrow curve has been simulated to show the effect of standard and worn rail profiles. Four different wear stages of the rail profile are simulated and compared to the available vehicle measurements available. These simulations show that the use of a medium worn rail profile gives the most accurate value. / Innan ett fordon kan tas i bruk måste det genomgå en tillståndsprocess. För närvarande är denna process till stor del beroende av provningar. Detta är dock en dyr och lång process. Med hjälp av ny teknik och förbättrade simuleringar kan denna process förkortas och kostnaderna sänkas. Valideringen av en fordonsmodell begränsas dock ofta av de tillgängliga uppgifterna. Ofta finns inte de uppmätta rälsprofilerna tillgängliga och därför används en ny UIC60-profil för simuleringarna. Järnvägsspåret har ofta använts och visarDärför har forskning gjorts för att undersöka hur rälsprofilerna påverkar valideringen av en modell av ett järnvägsfordon. De nuvarande valideringsmetoderna i den europeiska normen används för att jämföra simulerade värden med de krafter och accelerationer som finns tillgängliga från fordonsmätningar. I det första steget har 25 spårsektioner med olika kurvradier använts.simulerats med en uppmätt rälsprofil var 100:e meter. I nästa steg har samma sektioner simulerats med hjälp av standardprofilen UIC60. Resultaten visar att användningen av uppmätta rälsprofiler har en positiv inverkan på simuleringsresultatet. I det sista steget har en enda smal kurva simulerats för att visa effekten av standard- och slitna rälsprofiler. Fyra olika slitningsstadier av rälsprofilen simuleras och jämförs med tillgängliga fordonsmätningar. Simuleringarna visar att användningen av en mediumsliten rälsprofil ger det mest exakta värdet.

The development of autonomous vehicles is progressing rapidly through extensive efforts by the automotive industry and researchers. One of the key factors for the adoption of autonomous driving technology is motion comfort and the ability to engage in non-driving tasks such as reading, socialising, and relaxing without experiencing motion sickness while travelling. Therefore, for the full success of autonomous vehicles, it is necessary to learn how to design and control the vehicles to mitigate motion sickness for the passengers.  This thesis aims to investigate methods for prediction of motion sickness in autonomous vehicles and how to mitigate it using vehicle dynamics based solutions, with an emphasis on trajectory planning. As a first step, a review and evaluation of existing motion sickness prediction methods were performed. The review highlighted the importance of accurate motion sickness assessment in the early phases of autonomous vehicle design. Two chosen methods (ISO 2631-based and sensory conflict theory-based) were evaluated to estimate individual motion sickness feelings using measured data and subjective assessment ratings from field tests. It can be concluded that the methods can be adjusted to predict individual motion sickness feelings, as shown by the comparison with the experimental data. To continue the work, a review of vehicle dynamics based motion sickness mitigation methods for autonomous vehicles was performed. Several chassis control strategies in literature like active suspension, rear-wheel steering and torque distribution have demonstrated the potential help to reduce motion sickness. Another effective approach to mitigate motion sickness in autonomous vehicles is to regulate vehicle speed and path using trajectory planning which was chosen to be further investigated. The trajectory planning was constructed as an optimisation problem where there is a trade-off between motion sickness and manoeuvre time. The impact of the trajectory planning algorithm to reduce motion sickness was analysed by simulating two different vehicle models in specific test manoeuvres. The results indicate that driving style has a significant influence on motion sickness and trajectory planning algorithms should be carefully designed to find a good balance between journey time and motion sickness. The research presented in this thesis contributes to the development of methodologies for predicting and mitigating motion sickness in autonomous vehicles, helping to achieve the goal of ensuring their overall success. / Utvecklingen av autonoma fordon går snabbt framåt tack vare omfattande insatser från fordonsindustrin och forskare. En av de viktigaste faktorerna för införandet av teknik för autonom körning är åkkomfort och möjligheten att ägna sig åt andra saker än körning, som att läsa, umgås och koppla av, utan att drabbas av åksjuka under resan. För att autonoma fordon ska lyckas fullt ut är det därför nödvändigt att förstå hur man utformar och styr fordonen för att minska risken för att passagerarna drabbas av åksjuka.  Denna licentiatuppsats syftar till att undersöka hur åksjuka kan förutsägas i vägfordon och hur den kan reduceras med hjälp av fordonsdynamikbaserade lösningar, med tonvikt på trajektorieplanering. Som ett första steg genomfördes en granskning och utvärdering av befintliga metoder för åksjukeprediktion. Granskningen belyste vikten av en korrekt bedömning av åksjuka i de tidiga faserna av autonom fordonsdesign. Två valda metoder (ISO 2631-baserad och sensorisk konfliktbaserad) utvärderades för att uppskatta individuell åksjuka med hjälp av uppmätta data och subjektiva bedömningar från fälttester. Slutsatsen är att metoderna kan justeras för att förutsäga individuell åksjuka, vilket framgår av jämförelsen med experimentella data. För att fortsätta arbetet gjordes en genomgång av fordonsdynamikbaserade metoder för att minska åksjuka i autonoma fordon. Flera chassireglerstrategier i litteraturen, såsom aktiv fjädring, bakhjulsstyrning och drivmomentfördelning, har visat sig kunna bidra till att minska åksjuka. En annan effektiv metod för att minska åksjuka i autonoma fordon är att reglera fordonets hastighet och bana med hjälp av trajektorieplanering, vilket valdes att undersökas ytterligare. Trajektorieplaneringen konstruerades som ett optimeringsproblem där det finns en avvägning mellan åksjuka och manövertid. Effekten av trajektorieplaneringsalgoritmen för att minska åksjuka analyserades genom att simulera två olika fordonsmodeller i specifika testmanövrar. Resultaten indikerar att körstil har en betydande inverkan på åksjuka och att algoritmer för trajektorieplanering bör utformas noggrant för att hitta en bra balans mellan restid och åksjuka. Forskningen som presenteras i denna uppsats bidrar till utvecklingen av metoder för att förutsäga och mildra åksjuka i autonoma fordon, vilket hjälper till att uppnå målet att säkerställa deras framgång.

Mechanical systems operate under parametric and external excitation uncertainties. The polynomial chaos approach has been shown to be more efficient than Monte Carlo approaches for quantifying the effects of such uncertainties on the system response. This work uses the polynomial chaos framework to develop new methodologies for the simulation, parameter estimation, and control of mechanical systems with uncertainty. This study has led to new computational approaches for parameter estimation in nonlinear mechanical systems. The first approach is a polynomial-chaos based Bayesian approach in which maximum likelihood estimates are obtained by minimizing a cost function derived from the Bayesian theorem. The second approach is based on the Extended Kalman Filter (EKF). The error covariances needed for the EKF approach are computed from polynomial chaos expansions, and the EKF is used to update the polynomial chaos representation of the uncertain states and the uncertain parameters. The advantages and drawbacks of each method have been investigated. This study has demonstrated the effectiveness of the polynomial chaos approach for control systems analysis. For control system design the study has focused on the LQR problem when dealing with parametric uncertainties. The LQR problem was written as an optimality problem using Lagrange multipliers in an extended form associated with the polynomial chaos framework. The solution to the Hâ problem as well as the H2 problem can be seen as extensions of the LQR problem. This method might therefore have the potential of being a first step towards the development of computationally efficient numerical methods for Hâ design with parametric uncertainties. I would like to gratefully acknowledge the support provided for this work under NASA Grant NNL05AA18A. / Ph. D.

This dissertation details the methods and analysis of extensive physical tests and simulation conducted by the Center for Vehicle Systems and Safety (CVeSS) at Virginia Tech on the maneuverability, roll-stability, and brake type performance of 33-ft double trailers. Little literature exists for 33-ft doubles because they are uncommon on the U.S. roads due to current federal restrictions limiting long-combination vehicles to 28-ft doubles. With the continual rise in e-commerce, however, there is a push by package carriers on legislation to permit carriers to introduce 33-ft doubles into their fleets. Three separate studies detailed herein highlight 33-ft double trailers' off-tracking, roll-stability with stability control systems, and brake type influence on braking performance. The first study compares low-speed off-tracking of a 33-ft double to 28-ft double and 53-ft single configurations via simulation and full-scale tests. Novel numerical tractrix models are introduced and compared to existing models commonly used to evaluate low-speed off-tracking of long combination vehicles (LCVs). Unlike pre-existing models, accuracy of one of the proposed models is largely unaffected by input path resolution and regularity—a significant benefit for reducing computational cost and easing implementation for many applications. Full-scale tests are conducted at Virginia Tech and an extensive uncertainty analysis is detailed for the test procedure and measurements. Field tests compare favorably with simulations for all tested maneuvers and trailer configurations and clearly demonstrate the order from least to most off-tracking as 28-ft double, 33-ft double, and 53-ft single. The 33-ft doubles have slightly larger off-tracking than 28-ft doubles, whereas 53-ft singles have substantially larger off-tracking than 28-ft and 33-ft doubles. The second study evaluates 33-ft double straight-rail trailers rollover propensity with different stability control system implementations: stock (none), tractor electronic stability control (ESC), trailer roll-stability control (RSC), and RSC+ESC. Extensive test vehicle instrumentation and structural reinforcement are detailed for the test preparations. Tests are conducted on a test track with either driver or robot steering. On their own, both ESC and RSC clearly reduce the rollover propensity of the trailers for all maneuvers, and the trailers exhibit the highest roll-stability when both RSC and ESC are active. The tested ESC and RSC modules are off-the-shelf products from industry suppliers chosen by the program sponsor. The third study compares trailer drum and disc brake performance in three conditions: straight-line braking distance, brake type influence on RSC performance, and roll dynamics in a combined braking and turning maneuver. A braking robot is designed, fabricated, and implemented to provide precise and repeatable brake pedal application. Test results suggest that disc brakes tend to provide reduced braking distance and are less susceptible to brake fade than drum brakes. Anti-lock braking system (ABS) and suspension dynamics react differently to the two brake types. Small, noticeable differences in RSC performance are evident between the two brake types. Within the test limitations, rollover dynamics were not clearly different between the two brake types for braking-in-turn maneuvers, performed for a large range of entry speeds and brake activation delay relative to the start of steering. / Doctor of Philosophy / Due to their large size, mass, and high center-of-gravity, heavy vehicles, especially long combination vehicles (LCVs) require a substantial amount of space to negotiate turns, long distances to brake from highway speeds to a stop and are susceptible to rollover. Combination vehicles on the U.S. roads are commonly in 53-ft single trailer or 28-ft double trailer configurations. With the continual rise of e-commerce, package carriers are pursuing 33-ft double trailers to increase each vehicle's cargo volume. Before introducing these trailers into a fleet, there is a need to understand (1) if 33-ft doubles can negotiate existing routes traveled by 28-ft double and 53-ft single configurations, (2) if 33-ft doubles can benefit from existing stability control systems, and (3) how trailer brake types perform on 33-ft doubles. Three separate studies are conducted to address these topics. The first study compares off-tracking for the three mentioned trailer configurations through low-speed, real-world maneuvers via physical full-scale tests and simulation. Off-tracking is a metric illustrative of maneuverability and is defined as the relative distance in paths of the rearmost axle to the lead steer axle. New mathematical models are introduced and used to simulate vehicle motion through low-speed maneuvers. The simulation and field tests determine that, for all tested maneuvers, the order from smallest to largest off-tracking is 28-ft double, 33-ft double, and 53-ft single configurations, with the 33-ft doubles having slightly larger off-tracking than 28-ft doubles. This suggests that 33-ft doubles can travel through routes typically traveled by a 53-ft single but need slightly more space on the road than a 28-ft double. The second study tests 33-ft double trailers with and without stability control systems. Tests, conducted at a test track, are designed to replicate real-world maneuvers that induce trailer rollover. It is found that the 33-ft double trailers are clearly less likely to rollover with the tested stability enhancement systems than without. The tests also illustrate that the different tested control systems' effectiveness in reducing rollover propensity is maneuver dependent. The third study tests the braking distance, brake influence on the stability control systems, and rollover dynamics while braking-in-turn for two different types of brakes, drum brakes and disc brakes. Small but evident differences in the performance of the two brake types suggest disc brakes could provide shorter stopping distance and time at highway speeds, compared with drum brakes. The studies detailed in this dissertation provide valuable information on 33-ft doubles dynamics and provide guidance for their safe introduction on the U.S. roadways.

The contact between the tire and the road is the key enabler of vehicle acceleration, deceleration and steering. However, under the circumstances of sudden changes to the road conditions, the driver`s ability to maintain control of the vehicle maybe at risk. In many cases, this requires intervention from the chassis control systems onboard the vehicle. Although these systems perform well in a variety of situations, their performance can be improved if a real-time estimate of the tire-road contact parameters (ranging from kinematic conditions of the tire to its dynamic properties) are available. At the present stage of development, tire-road contact parameters are indirectly estimated using observers based on vehicle dynamics measurements (acceleration, yaw and roll rates, suspension deflections, etc). Although these methods present a relatively accurate solution, they rely heavily on tire and vehicle kinematic formulations and break down in case of abrupt changes in the measured quantities. To address this problem, researchers have been developing certain sensor based advanced tire concepts for direct measurement of the tire-road contact parameters. Thus the new terms "Intelligent Tire" and "Smart Tire", which mean online tire monitoring are thus enjoying increasing popularity among automotive manufacturers and formed the motivation for this thesis to explore the possibility of developing an intelligent tire system. The development of the so called "intelligent tire/ smart tire system" is expected to spur the development of a new generation of vehicle control system with modified control strategies, leveraging information directly coming from the interface between the tire and the road, and in turn significantly reducing the risk of accidents. The specific contributions of this thesis include the following: • Development of an intelligent tire system, with a special attention to development of measurement and sensor feature extraction methodologies of acceleration signals coming from sensors fixed to the tire innerliner • Design of an integrated vehicle state estimator for application to global chassis control • Development of a model-based tire-road friction estimation algorithm • Development of an intelligent tire based adaptive wheel slip controller for anti-lock brake system (ABS) • Development of a piezoelectric vibration energy harvesting system with an adaptive frequency tuning mechanism for intelligent tires / Master of Science

The ride stability of an A-train 28-foot double tractor trailer when outfitted with different Roll Stability Control (RSC) systems with the same payload and suspension configurations is studied experimentally for various dynamic maneuvers. The primary goal of the study is to determine the effect of different commercially-available RSC systems on the extent of improvements they offer for increasing roll stability of commercial vehicles with double trailers, when subjected to limit-steering maneuvers that can rise during highway driving. A semitruck and two 28-foot trailers are modified for enduring the forces and moments that can result during testing. A load structure is used for placing the ballast loads within the trailers at a suitable height for duplicating the CG height of the trailers during their commercial use. Outriggers and jackknifing arresting mechanisms are used to prevent vehicle damage and ensure safety during the tests. The test vehicle is equipped with multiple sensors and cameras for the necessary measurements and observations. The analog and video data are time-synced for correlating the measurements with visual observation of the test vehicle dynamics in post-processing. An extensive number of tests are conducted at the Michelin Laurens Proving Grounds (MLPG) in Laurens, SC. The tests include evaluating each RSC system with different maneuvers and speeds until a rollover occurs or the vehicle is deemed to be unstable. The maneuvers that are used for the tests include: double lane change, sine-with-dwell, J-turn, and ramp steer maneuver. Both a steering robot and subjective driver are used for the tests. The test data are analyzed and the results are used to compare the three RSC systems with each other, and with trailers without RSC. The test results indicate that all three RSC systems are able to improve the speed at which rollover occurs, with a varying degree. For two of the systems, the rollover speed gained, when compared with trailers without RSC, is marginal. For one of the systems, there are more significant speed gains. Since most RSC systems are tuned for a conventional tractor-trailer, additional testing with some of the systems would be necessary to enable the manufacturers to better fine-tune the RSC control scheme to the dynamics of double trailers. / MS

The research presented in this thesis, studies driver gap acceptance behavior for permissive left turn movements at signalized intersections. The thesis attempts to model the gap acceptance behavior using three different approaches, a deterministic statistical approach, a stochastic approach, and a psycho-physical approach. First, the deterministic statistical modeling approach is conducted using logistic regression to characterize the impact of a number of variables on driver gap acceptance behavior. The variables studied are the gap duration, the driver's wait time in search of an acceptable gap, the time required to travel to clear the conflict point, and the rain intensity. Considering stochastic gap acceptance, two stochastic approaches are compared, namely: a Bayesian and a Bootstrap approach. The study develops a procedure to model stochastic gap acceptance behavior while capturing model parameter correlations without the need to store all parameter combinations. The model is then implemented to estimate stochastic opposed saturation flow rates. Finally, the third approach uses a psycho-physical modeling approach. The physical component captures the vehicle constraints on gap acceptance behavior using vehicle dynamics models while the psychological component models the driver deliberation and decision process. In general, the three proposed models capture gap acceptance behavior for different vehicle types, roadway surface conditions, weather effects and types of control which could affect the driver gap acceptance behavior. These findings can be used to develop weather responsive traffic signal timings and can also be integrated into emerging IntelliDrive systems. / Master of Science