Academic literature on the topic 'Tire'

Abstract As a result of the 1st International Colloquium on Tire Models for Vehicle Dynamics Analysis in 1991, the international TYDEX Workshop working group was established. This workshop concentrated on the standardization of the exchange of tire measurement data and the interface between tire and vehicle models in order to improve the communications between vehicle manufacturers, suppliers, and research organizations. The development and knowledge of tire behavior is of great importance to both the tire and vehicle industries and will be intensified. Therefore the TYDEX Workshop received great interest from all parties to come to some kind of standardization. In the two expert groups, one of which focused on Tire Measurements — Tire Modeling and the other on Tire Modeling — Vehicle Modeling, the TYDEX-Format and the standard tire interface have been developed, which will be explained in this paper. Furthermore, a short overview of the European TIME project aiming at a standard tire testing procedure will be given, which is reliable and consistent with realistic driving conditions. Standard testing procedures are some of the important consequences of the TYDEX Workshop.

ABSTRACT This paper analyzes the effect of tire/vehicle parameters, specifically of tire/suspension torsional stiffnesses, on the stability of self-excited tire torsional oscillations during locked-wheel braking events. Using a torsionally flexible tire-wheel model and a dynamic tire-ground friction model, two system models for tire oscillations are considered: with suspension torsional compliance included in one but excluded in the other. Bifurcation analysis is conducted on both systems to derive the effect of tire/vehicle parameters on the stability. For the system without suspension torsional compliance, it is highlighted that the primary cause of unstable self-excited oscillations is the “Stribeck” effect in tire-ground friction. Based on the parameters obtained experimentally, the bifurcation surface of vehicle velocity with respect to tire/suspension torsional stiffness is also given. The effect of tire/suspension torsional stiffness to the stability of tire torsional oscillation is qualitatively validated via comparisons between locked-wheel braking simulations and experiments with tires with different torsional stiffnesses.

ABSTRACT Vehicle-based tire testing can potentially make it easier to reparametrize tire models for different road surfaces. A passenger car equipped with external sensors was used to measure all input and output signals of the standard tire interface during a ramp steer maneuver at constant velocity. In these measurements, large lateral force vibrations are observed for slip angles above the lateral peak force with clear peaks in the frequency spectrum of the signal at 50 Hz and at multiples of this frequency. These vibrations can lower the average lateral force generated by the tires, and it is therefore important to understand which external factors influence these vibrations. Hence, when using tire models that do not capture these effects, the operating conditions during the testing are important for the accuracy of the tire model in a given maneuver. An Ftire model parameterization of tires used in vehicle-based tire testing is used to investigate these vibrations. A simple suspension model is used together with the tire model to conceptually model the effects of the suspension on the vibrations. The sensitivity of these vibrations to different operating conditions is also investigated together with the influence of the testing procedure and testing equipment (i.e., vehicle and sensors) on the lateral tire force vibrations. Note that the study does not attempt to explain the root cause of these vibrations. The simulation results show that these vibrations can lower the average lateral force generated by the tire for the same operating conditions. The results imply that it is important to consider the lateral tire force vibrations when parameterizing tire models, which does not model these vibrations. Furthermore, the vehicle suspension and operating conditions will change the amplitude of these vibrations and must therefore also be considered in maneuvers in which these vibrations occur.

ABSTRACT Tire wear performance is very important in terms of safety and economic benefit for customers and environmental conservation. Tire wear performance can be sorted into “global” or “local” wear. Local wear means uneven tire wear, for example, heel/toe wear, one-sided shoulder wear, feather edge wear, etc. This uneven wear decreases tire life locally and has the potential for causing a noise problem, so it is very important to improve uneven wear performance for long life tire. It is difficult to correctly evaluate the uneven tire wear performance of a brand-new tire, because the tire wear performance changes with tire pattern shape transformation as it wears. In order to experimentally evaluate uneven wear performance accurately, we have to do time-consuming tire road tests. Therefore, we need a prediction method for uneven wear. In this paper, we introduce “wear progress simulation” developed in order to evaluate heel/toe wear performance, which occurs in the shoulder blocks. This method involves “wearing out the finite element (FE) tire model” using wear energy calculated from tire rolling simulation. By this method, we can observe the transformation of tire pattern shape and wear energy distribution. As a result, we can estimate the difference of heel/toe wear performance among tires by our developed simulation.

ABSTRACT The idea of intelligent tires is to develop a tire into an active perception component or a force sensor with an embedded microsensor, such as an accelerometer. A tire rolling kinematics model is necessary to link the acceleration measured with the tire body elastic deformation, based on which the tire forces can be identified. Although intelligent tires have attracted wide interest in recent years, a theoretical model for the rolling kinematics of acceleration fields is still lacking. Therefore, this paper focuses on an explicit formulation for the tire rolling kinematics of acceleration, thereby providing a foundation for the force identification algorithms for an accelerometer-based intelligent tire. The Lagrange–Euler method is used to describe the acceleration field and contact deformation of rolling contact structures. Then, the three-axis acceleration vectors can be expressed by coupling rigid body motion and elastic deformation. To obtain an analytical expression of the full tire deformation, a three-dimensional tire ring model is solved with the tire–road deformation as boundary conditions. After parameterizing the ring model for a radial tire, the developed method is applied and validated by comparing the calculated three-axis accelerations with those measured by the accelerometer. Based on the features of acceleration, especially the distinct peak values corresponding to the tire leading and trailing edges, an intelligent tire identification algorithm is established to predict the tire–road contact length and tire vertical load. A simulation and experiments are conducted to verify the accuracy of the estimation algorithm, the results of which demonstrate good agreement. The proposed model provides a solid theoretical foundation for an acceleration-based intelligent tire.

ABSTRACT In the past, handling performance of the tire–vehicle combination has been evaluated using tire models such as the Pacejka Magic Formula. These models usually lack realistic representation of tire–road interaction and are not suitable for combined steering and braking maneuvers that may activate the antilock braking system. The objective of this study is to develop a computationally simple and accurate tire model, which can be used in the development and evaluation of handling performance of the tire on uneven road surfaces. For an emergency obstacle avoidance maneuver at high speeds, transient tire behavior plays a crucial role in the generation of forces between tire and road. Road undulations and steering inputs both induce high-frequency tire belt vibrations, which have detrimental effects on the handling and tractive behavior of the tire. To meet these requirements, a dynamic six degrees of freedom tire model–based rigid ring approach is developed and integrated with a multiple tandem elliptical cam to include enveloping behavior of the tire. The tire model that is developed in this research is partially based on the work of Schmeitz found in the literature. The tire model was parameterized using experimental parameters found in the literature. The tire model is validated using fixed axle high-speed oblique cleat experimental data. The developed tire model is integrated with the vehicle model in CarSim®. From the simulation of successive step steering input, the increasing influence of tire belt vibrations at higher slip angles was observed due to sudden steering wheel inputs. From the simulation of the step steering input on the bad asphalt road surface with an added cleat and on the flat smooth road surface, it was observed that the lateral performance of the tire at higher slip angles is strongly influenced by the vertical load variations. A single lane change maneuver was simulated on the smooth and bad asphalt road surfaces, demonstrating the strong influence of tire lateral and vertical belt vibrations on the lateral performance of the vehicle. Simulation of high-speed emergency obstacle avoidance braking maneuvers on measured rough and smooth roads showed that the influence of high-frequency vibrations due to road undulations and step steering inputs causes large variations of longitudinal and lateral forces at the axle, thus creating large variations in slip and slip angle of the tire with a degraded braking distance on rough roads.

ABSTRACT Tire inflation pressure loss is inevitable during tire service time. The inflation pressure loss rate (IPLR) is widely used to estimate the inflation pressure retention performance of a tire. However, an IPLR test is a time-consuming process that lasts 42 days for a passenger car tire and 105 days for a truck/bus tire. To perform a thorough study of the tire pressure loss process, based on Abaqus software, a finite element model was developed with tire geometry inputs as well as tire material inputs of both mechanical and permeability properties of the various rubber compounds. A new method—the ideal material method—is proposed here to describe the transient tire pressure loss. Different from the previous isotropic models, the cord–rubber system is described using orthotropic diffusivities, which were determined through air-pressure-drop tests then applied in the finite element model in this article. Compared with the standard IPLR test, the difference between the tire IPLR test and the simulation result is within 5%.

ABSTRACT Maintaining proper tire inflation is the number one issue facing commercial fleets today. Common, slow-leaking tread area punctures along with leaking valve stems and osmosis through the tire casing lead to tire underinflation with a subsequent loss in fuel economy, reduction in retreadability, tread wear loss, irregular wear, and increase in tire-related roadside service calls. Commercial truck tires are the highest maintenance cost for fleets second only to fuel. This article will examine tire footprint analysis, rolling resistance data, and the effect on vehicle fuel economy from tires run at a variety of underinflated, overinflated, and recommended tire pressures. This analysis will also include the tire footprint impact by running tires on both fully loaded and unloaded trailers. The footprint analysis addresses both standard dual tires (295/75R22.5) along with the newer increasingly popular wide-base tire size 445/50R22.5.

ABSTRACT Tire marks play a central role in the reconstruction of traffic accidents, since they can provide valuable information about the vehicle's trajectory, initial speed, or the steering and braking input of the driver. The research project described in this paper focuses on the analysis of tire marks under controlled conditions using a monowheel setup to enable a selective variation of different vehicle dynamic parameters without mutual influence. The long-term goal is to find a model for the development of tire marks to predict the influence of specific vehicle dynamic parameters on the generation of tire marks. This model may be applied in accident reconstruction tools. A literature review has been performed to find evidence for the development of tire marks and to identify relevant parameters for their generation. Currently, no explicit physical or mathematical model showing the influence of tire forces or slip on the generation of tire marks is available. In the literature, it is often assumed that tire marks occur at the limit of traction. A physically motivated formula has been developed to calculate the friction force within the contact patch as a function of the tire forces, the longitudinal slip, and the side slip angle. The main hypothesis deduced from this formula is that the intensity of a tire mark depends on the magnitude of this friction force independent of the varying parameter. To verify this hypothesis, experiments have been conducted with variations in longitudinal slip, side slip angle, and tire type. First results agree with the model, showing a correlation between the intensity of tire marks and friction force, depending on the tribological and optical tire and road properties. This correlation is introduced as tire-marking sensitivity.

The proper management of scrap tires is relatively resource-intensive. Two features of waste tires produce internal and external costs. Their donut-like shape occupies vast space on transportation vehicles and in general landfills. It also allows the breeding of disease-carrying mosquitoes in populated areas. Their rubber and steel composition makes them durable and at the same time costly to reduce in size. Tire rubber can also generate air and ground pollutants during fires. Mosquito and fire outbreaks are associated with scrap tire stocks of any size. Faced with increasing flows of scrap tires (and other solid and hazardous waste), local officials consider a policy to decrease the waste tire generation rate, i.e., source-reduction. To implement such a policy, a critical first step is to determine, theoretically and empirically, the factors that influence tire demand. Consequently, this thesis applies basic consumer theory to specify important economic determinants of tire demand. Their empirical counterparts form the basis of the explanatory variables in the econometric demand model. Tire sales quantities are derived from state revenue collections of a per unit tire tax on new tire purchases. Measurement errors in the dependent variable and lack of explanatory data motivate the use of the generalized least-squares fixed effects estimator in a pooled tire demand model comprising 28 states. The qualitative results of the econometric estimation are in conformity with economic theory. Quantitatively, the model produces an income elasticity of 0.4; a ten percent increase in real per capita income increases tire sales per vehicle by four percent, ceteris paribus. This effect is very likely to measure increased gasoline consumption, i.e., vehicle utilization. The calculated own price elasticity of tire demand is about -15, which is too large to reflect a pure price effect. Unless statistical problems generate this estimate, it probably captures a movement of and along the tire demand curve.

A tire is an essential part on a vehicle. Different tires have different properties, and one of them is the longitudinal stiffness of the tire. Tire stiffness can be explained by modelling the tire as small thread compounds. These small thread compounds will have contact with the surface and will contain one adhesion and one sliding region. The slip is the motion of the thread compounds relative to the surface. The forces that act on the thread compounds are divided by slip and this is defined as tire stiffness. This thesis presents a method to estimate the tire stiffness in real-time. By using different algorithms, such as Recursive Least Squares and Least Mean Square, a good approximation of the tire stiffness can be achieved.

La riduzione del rumore generato dagli pneumatici in rotolamento rappresenta una delle principali e più difficili sfide per le case produttrici di pneumatici. Negli ultimi anni, infatti, c’è stato un sempre crescente interesse verso questo argomento a seguito delle richieste provenienti dal mondo automobilistico e delle nuove normative in termini di riduzione dell’inquinamento acustico, che impongono un forte abbattimento del rumore generato dagli pneumatici. Oggigiorno, le case automobilistiche tendono a richiedere pneumatici sempre più silenziosi per garantire livelli di confort sempre più elevati all’interno dell’abitacolo e in quest’ottica gli pneumatici giocano un ruolo fondamentale. Col passare degli anni, è stato fatto un notevole passo avanti in termini di abbattimento del rumore generato dal sistema di propulsione, principalmente attraverso l’isolamento acustico dell’abitacolo e, dal momento che la seconda fonte di rumore dopo il motore è rappresentata proprio dagli pneumatici, si capisce come mai ci sia la richiesta di pneumatici silenziosi. Il rotolamento degli pneumatici sull’asfalto, infatti, genera un rumore piuttosto fastidioso che viene percepito in maniera fortemente sgradevole all’interno del veicolo. Inoltre, questo aspetto sta diventando ancor più importante a seguito della massiccia diffusione delle auto ibride ed elettriche, in cui il rumore del motore è fortemente ridotto o addirittura eliminato. Dall’altro lato ci sono le nuove normative riguardo la riduzione dell’inquinamento acustico delle nostre città che impongono anch’esse un forte abbattimento delle emissioni sonore dello pneumatico, per di più da conseguire anche in tempi molto stretti. La somma di queste due richieste impone quindi uno studio approfondito di questo aspetto a partire dalla necessità di approfondire quali sono i meccanismi di generazione del rumore. Quando si parla di rumore generato dagli pneumatici, occorre fare una distinzione tra “in-vehicle noise” and “exterior noise”: il primo rappresenta il rumore percepito dagli individui all’interno dell’abitacolo, mentre il secondo si riferisce al rumore emesso dallo pneumatico nell’ambiente esterno ed è la componente che viene percepita dalle persone all’esterno della vettura. Esiste poi anche una seconda distinzione basata sul meccanismo di generazione del rumore. Secondo questa classificazione, è possibile distinguere tra “Structureborne noise” e “Airborne noise”: nel primo caso il rumore è legato all’interazione dello pneumatico con altri componenti del veicolo che genera delle forze al mozzo che si traducono in vibrazioni e rumore a bassa frequenza (250 Hz); la seconda componente dipende solamente dallo pneumatico e dalla sua interazione con l’aria. Questo secondo gruppo è responsabile principalmente del rumore esterno, ma ha anche una componente ad alta frequenza (fino a 2000 Hz) che rientra all’interno dell’abitacolo. Da questa breve introduzione si capisce come il fenomeno analizzato sia molto complesso, in quanto comprende diverse componenti che sono molto diverse tra loro, sia in termini di meccanismo che di range di frequenza, e pertanto richiedono studi e contromisure dedicate. Per ottenere una riduzione del rumore così consistente, è necessario un drastico cambiamento del modo in cui viene approcciato il problema, poiché si è capito come sia necessario considerare questo aspetto fin dalle prime fasi dello sviluppo di un nuovo pneumatico, accanto a tutte le performance classiche, quali bassa resistenza al rotolamento, handling o braking. Finora, invece, la silenziosità era vista come una caratteristica secondaria o un optional. Generalmente ci si occupava di questo aspetto solo in caso di reclami da parte di una casa automobilistica o se le emissioni sonore dello pneumatico erano di poco al di sopra dei limiti e non c’era quindi la possibilità di ricevere l’omologazione ed essere immesso sul mercato. Si trattava comunque di problemi di piccola entità che con piccoli cambiamenti a livello di pattern era possibile in qualche modo risolvere. Tuttavia, si capisce come si trattasse di un approccio basato sull’esperienza degli ingegneri, ma non sorretto da una base teorica. Per poter abbattere le emissioni acustiche dello pneumatico è necessario in primo luogo comprendere quali sono i meccanismi di generazione del rumore, in modo da sviluppare uno pneumatico che abbia una struttura e un disegno del battistrada cosiddetti “noise-oriented”. Secondo diversi studi, tra i tanti meccanismi di generazione del rumore, il più importante è rappresentato dalle vibrazioni dello pneumatico in rotolamento, pertanto questo lavoro è incentrato proprio su questo aspetto. Il lavoro è diviso in due sezioni principali; la prima parte è focalizzata sulla caratterizzazione dinamica dello pneumatico, mentre nella seconda parte viene presentata un’innovativa caratterizzazione dinamica di alcuni suoi componenti per valutare la loro influenza sulle emissioni acustiche. In entrambi i casi vengono presentati dei casi studio per esporre i principali risultati conseguiti all’interno di questo progetto. Come detto, la prima parte della presente tesi è dedicata alla misura delle vibrazioni dello pneumatico attraverso lo sviluppo di un set-up innovato basato sulla tecnica 3D Digital Image Correlation (3D-DIC). Questa tecnica ha diversi vantaggi e permette di superare i limiti dello stato dell’arte, rappresentato dalle misure effettuate con il Vibrometro Laser Doppler. Per una misura di questo tipo occorre una tecnica che sia in grado di misurare un oggetto in movimento, quindi deve essere una tecnica senza contatto e deve essere in grado di misurare all’interno di un range molto ampio (0 – 2000 Hz). Finora l’unico strumento in grado di eseguire una tale misura era il Vibrometro Laser Doppler, anche se con diversi limiti, come ad esempio la possibilità di misurare solamente il fianco dello pneumatico o i tempi molto lunghi, in relazione al numero di punti da acquisire, che possono provocare variazioni delle condizioni al contorno. La DIC è una tecnica nata principalmente per misure statiche o quasi statiche di deformazioni o spostamenti, tuttavia le moderne fast cameras possono rappresentare una valida alternativa al vibrometro laser in quanto sono caratterizzate da frame rate molto elevati, ragion per cui è possibile misurare spostamenti estremamente piccoli e, quindi, è possibile usare tale tecnica anche per misure di vibrazioni ad alta frequenza. L’utilizzo di tale set-up ha richiesto un lungo lavoro di ottimizzazione, ampiamente descritto in questa tesi, necessario per valutare l’effetto di tutti i principali parametri che influenzano l’acquisizione e, in particolare, è stato necessario capire come poter sfruttare al meglio la strumentazione disponibile per poter eseguire le misure necessarie. Gli attuali limiti tecnologi, infatti, permettono di avere frame rate estremamente elevati, ma al tempo stesso non è possibile avere risoluzioni troppo spinte, altrimenti la dimensione delle immagini sarebbe troppo grande e le attuali velocità di trasferimento dei dati non sarebbero in grado di seguire la frequenza con cui vengono acquisite le immagini stesse. Per tale motivo è richiesto un adattamento dell’inquadratura a seconda del range di frequenze che si vuole studiare. Le vibrazioni dello pneumatico in rotolamento si dividono in due grandi gruppi: le vibrazioni a bassa frequenza (fino a circa 250 Hz) sono caratterizzate da spostamenti di ampiezza elevata che investono tutta la struttura dello pneumatico e per questo sono detti modi di carcassa; ad alta frequenza, le vibrazioni sono generate dagli impatti dei blocchetti del battistrada sull’asfalto che causano spostamenti molto piccoli dei punti localizzati intorno la zona di contatto e sono vibrazioni che rimangono fortemente localizzate in quella zona e non possono essere misurate lavorando con un’inquadratura sull’intero fianco. Nonostante la DIC sia una tecnica di misura full-field, lavorando con un range in frequenza molto ampio e, considerando le dimensioni dello pneumatico, non è possibile sfruttare del tutto questa proprietà. Infatti, se il focus è la bassa frequenza, si può utilizzare un’inquadratura sull’intero fianco, ma se si vogliono studiare le alte frequenze, è necessario usare un’inquadratura focalizzata sulla zona di contatto, che è stato dimostrato essere la zona più rappresentativa del comportamento vibrazionale dell’intero pneumatico. Nell’ambito della misura delle vibrazioni dello pneumatico in rotolamento, l’utilizzo di tale set-up, ha permesso di raggiungere un importante obiettivo, cioè quello di misurare la corona dello pneumatico, che rappresenta una grande innovazione in quanto non è possibile eseguire questa misura con altre tecniche a causa delle discontinuità introdotte dal pattern che rendono impossibile l’utilizzo del vibrometro laser. In questo modo è possibile avere una caratterizzazione dinamica completa dello pneumatico e, attraverso due casi studio, è stato dimostrato come è possibile usare questa tecnica per fornire nuove utili informazioni agli ingeneri di sviluppo. In particolare, dallo studio di diversi pneumatici è emerso come sia possibile ottenere una forte riduzione del rumore con pneumatici in cui le vibrazioni del fianco sono molto smorzate, anche se questo comporta un incremento della mobilità della corona. Questa affermazione è stata dimostrata presentando due casi studio, in cui quest’effetto viene ottenuto con due differenti soluzioni tecniche. Infine, l’intero set-up di misura è stato validato sia in condizioni statiche che dinamiche attraverso il confronto con il vibrometro laser. Il confronto mostra come ci sia un’ottima corrispondenza tra le due misure e permette di evidenziare come la maggiore sensibilità del vibrometro permetta di misurare l’intero range di frequenza con un’unica misura, ma la risoluzione spaziale è piuttosto bassa. La seconda parte del lavoro, invece, introduce un innovativo approccio allo studio del problema, in quanto considera l’effetto di alcuni componenti della struttura dello pneumatico sull’emissione acustica. Tale metodo vuole far fronte alla difficoltà degli ingegneri di scegliere quale sia il materiale di rinforzo più adatto per la struttura di uno pneumatico silenzioso, dovendo scegliere tra una lista molto ampia di candidati. Finora tale problema veniva risolto producendo un prototipo per ogni soluzione tecnica o materiale da testare, i prototipi venivano testati acusticamente e quello che risultava essere più silenzioso veniva scelto. In questo modo si spendono molto tempo e molto denaro, ma soprattutto non si capisce quali siano i meccanismi di generazione del rumore, non si capisce perché un materiale sia migliori di un altro e per di più non viene fatta la caratterizzazione dei materiali. L’utilizzo di tale procedura è dettato dalla mancanza di una caratterizzazione dinamica dei materiali. Sebbene esista una caratterizzazione dinamica delle gomme utilizzate per produrre le mescole così come una dettagliata caratterizzazione dei materiali in termini di proprietà fisiche e meccaniche, non esiste una caratterizzazione di campioni compositi di gomma e corde di materiali di rinforzo. In realtà una minima caratterizzazione esiste, ma viene fatta su campioni molto piccoli e in condizioni quasi statiche che serve solo a definire i valori di rigidezza “in-plane” and “out-of.plane”. Il problema è che non si tratta di una caratterizzazione noise-oriented perché non tiene conto del comportamento dinamico del provino. L’approccio proposto, invece, considera dei campioni costruiti allo stesso modo in cui si possono trovare nella struttura dello pneumatico, cioè sono piccole travette di gomma calandrate con immerse delle corde di materiale di rinforzo. La nuova procedura si basa sulla caratterizzazione di tali provini utilizzando la tecnica DIC ed è possibile in questo modo definire l’effetto di ogni materiale in termini di mobilità dei campioni analizzati. In questo modo si possono selezionare i materiali che rispettano determinate condizioni e i test su pneumatico servono solo per conferma, quindi il loro numero sarà ridotto drasticamente con notevole risparmio di tempo e soldi. Anche in questo caso l’ottimizzazione del set-up ha richiesto molto tempo, in particolare per la definizione della struttura dei campioni. Il confronto di misure acustiche su pneumatico in rotolamento, caratterizzazione dinamica dello pneumatico e misure vibrazionali sui campioni ha permesso di definire che i materiali di rinforzo da preferire sono quelli che aumentano la mobilità della corona, in quanto si riduce la mobilità del fianco che è la principale sorgente di rumore. Tutto questo ragionamento è supportato da un caso studio presentato nell’ultimo paragrafo. In conclusione, un nuovo sistemata per la misura delle vibrazioni dello pneumatico in condizioni di rotolamento è stato sviluppato, ottimizzato e validato attraverso il confronto con il Vibrometro Laser Doppler, sia in condizioni statiche che dinamiche. Il nuovo set-up permette di eseguire misure anche sulla corona, non realizzabili con nessun’altra tecnica. Lo stesso set-up è stato utilizzato per la caratterizzazione dinamica di componenti dello penumatico.
The reduction of the noise generated by rolling tire is becoming one of the most important and difficult challenges for tire manufactures. The growing interest in tire noise performances is related both to the requirements coming from the car industry and the new regulations regarding the reduction of the acoustic pollution of our cities. Car manufacturers require silent tire in order to guarantee a high comfort level inside the car. During last years, a lot of work has been done in order to make the interior of the cars as comfortable as possible and the current cockpit insulation can significantly reduce the noise coming from the engine, so, in order to further increase the comfort level, they ask for silent tires. According to several studies, in fact, the engine is the first noise source in a moving car followed by the rolling tire noise, so it is easy to understand the reason why there is such a requirement. The noise generated by rolling tires is completely different from the engine noise in terms of frequencies and the cockpit insulation cannot reduce it in the whole frequency range of interest (0 – 2000 Hz). This aspect is even more important with the new electric or hybrid engines, where the noise is completely or partially deleted. When talking about rolling tire noise, two main classifications have been defined. According to the first classification, “in-vehicle” and “exterior noise” can be distinguished: the first one refers to the noise perceived inside the car, while the second one is the noise heard by the people outside the car, i.e. the noise that propagates in the external environment. The second classification is based on the noise generation mechanism. In this case, “Structureborne noise” and “Airborne noise” can be distinguished: the first one refers to that noise component related to the interaction between rolling tire and car components resulting in spindle forces causing low frequency vibrations (up to 250 Hz) that are mainly responsible for the in-vehicle noise, while the “Airborne noise” refers to those mechanisms which depends on the tire only and on its interaction with the air. This second group mainly generates high frequency noise propagating in the surroundings, but it has also a contribution entering inside the car. On the other side, there are new regulations that impose a significant reduction in terms of exterior noise. From this short introduction it is clear how complex the analysed phenomenon is, because, even if the noise source is the same, each noise component is different from the others and requires dedicated studies and countermeasures. Tire manufacturers have understood that, in order to satisfy these requirements in terms of noise reduction, it is necessary to complete change how the tire noise study is approached, because noise performance must be considered from the first stages of the development as well as the other classic performances, such as handling, braking, rolling resistance and so on. In fact, the noise reduction to be achieved is very consistent, so it necessary to deeply understand how noise is generated to define the features of a noise-oriented tire structure. In the past years, a low noise level was considered an optional, mainly because it was quite easy to respect the limits imposed by regulations to obtain the approval for the commercialization. If there were some noise problems, they were solved with some changes in terms of pattern design based on the experience of the engineers, but the reduction obtained was very low. To significantly reduce the noise emission, it is necessary to investigate and understand how noise is generated and evaluate the effect on the noise emission of every tire components and materials used in tire construction. To do this, it is necessary to better understand the noise generation mechanisms, in fact, even if a lot of researchers have studied this phenomenon for decades, it is still not completely clear how noise is generated. According to several studies, among all the mechanisms the most important are the vibrations of the rolling tire. This is the main topic of this work and it is analysed in two different ways: from a global point of view through a complete dynamic characterization of the rolling tire and from a more detailed point of view looking at the dynamic characterization of samples of tire components. The first part of the thesis deals with the measurement of tire vibrations using an innovative set-up based on the 3D - Digital Image Correlation (DIC) technique. It has several advantages if compared with the current techniques, among which the possibility to measure irregular and inhomogeneous surface is one of the most important because it allows to perform significative measurement on tire crown. This is one of the innovations introduced in this work, since this measurement cannot be performed with other techniques. As well as the state of art technique, that is the Laser Doppler Vibrometer (LDV), the DIC is a non-contact technique, but it does not require a smooth and homogenous surface and this feature is exploited to measure the crown of the rolling tire. It is characterized by the so-called tread pattern, that is a sequence of blocks, so the LDV cannot be used because every block causes a spike in the LDV signal, while the DIC does not have this problem, since it compares two images to define the displacement of the measurement points. Even if it is a full-field technique, this feature cannot be completely exploited on a rolling tire, because of the width of the frequency range of interest and the size of the tire compared with the current resolution of the available cameras. The DIC technique was born to perform displacement and deformation measurements in static or quasi-static condition, but the modern fast cameras, characterized by very high frame rates, suggest the possibility to use this technique to perform vibration measurement. Since the DIC measure the displacements, it is necessary to have a high frame rate in order to detect also the very small displacements that characterise the high frequency vibration and the modern fast cameras satisfy this requirement, even if the resolution it is not too high, because the size of the image will be too high and there would not be the possibility to transfer the images with the same rate of the acquisition one. For this reason the frame size must be adequate to the frequency range of interest: if the low frequency carcass modes are investigated, the full-view on the sidewall can be used, but if the high frequency vibrations must be studied, it is necessary to focus the cameras on the contact patch area, in order to measure the small displacement generated by the impact of tread blocks with the road. These displacements are strictly localized in the contact patch area and a full-sidewall view cannot detect them: when the cameras are focused on a smaller area, the resolution of the system is increased because the pixels are focused on a smaller area and smaller displacements can be measured. The new set-up has been validated through the comparison with LDV both in static and dynamic condition in both the framing configurations. This is probably one of the main disadvantages of this technique, but it is a limit of current technologies because it is not possible to produce cameras with high resolution and high frame rate. The correlation between DIC and LDV measurement is very good, the LDV’s accuracy is a little bit higher, but it depends on the measured quantity (velocity VS displacement). The new dynamic characterization of tire crown and its comparison with sidewall provide new information about rolling tire vibrations that suggest some countermeasures for the development of a noise-oriented tire structure. provide new information not available in the past years. Two case studies are described to demonstrate the potentialities of the new set-up and demonstrating how an important noise reduction can be achieved. In the second part of this PhD project, the same set-up has been used to perform an innovative dynamic noise-oriented characterization of cord-rubber composite samples to evaluate the effect of reinforcing materials on the noise emission. It represents a completely new approach to the problem because it is a tentative to correlate the noise emission with tire structure components. A lot of work has been done to characterize rubber and reinforcing cords, but there are some problems: they are characterized separately, the size of the samples is very small and it is not representative of what happens on the real tire, it is a static or quasi-static characterization and if, a composite sample is used, in these conditions the only in-plane and out-of-plane stiffness values can be extracted. This procedure is useful to completely characterize the rubber used for tire compound and the reinforcing materials in terms of their mechanical properties, but it is useless in predicting noise emission, because the frequency response of the samples is unknown. The lack of these information is related to the approach used until now. As previously stated, in the past years tire silence was a secondary requirement and, when the first limitations in terms of noise emission had to be satisfied, a very expensive strategy in terms both of time and money has been used: the choice of the reinforcing material is performed producing a tire prototype for each candidate material, testing all the tires and identifying the tire that score the lowest noise emission. Nowadays, the reduction imposed is so strong, that tire developers are forced to consider the noise target from the first stages of the development in order to produce a noise-oriented tire structure and the absence of such a characterization has emerged. The approach proposed in this thesis considers samples produced in the same way they can be found on the final tire and the analysis of their mobilities suggest which are supposed to produce a reduction of noise emission. The final response comes from the test of a prototype tire, but in this way the selection of the proper materials is faster and, at the same time, the number of tests on tire and the prototypes produced is significantly reduced and the mechanism understanding is improved. In order to obtain good and useful results it important to define the correct structure of the samples, in fact even if the idea is to characterize the cap ply or body ply layers, the sample must contain also the belt package for global stiffness and mass reasons: if the belt is not used, the samples produced are very lightweight and the variation of the cord cause significant variations in terms of mass and stiffness with a shift in terms of resonance frequencies that it is not related to mechanical properties of the cord materials or sample thickness, but it is related to the mass variation only. When the belts are applied, the samples have almost the same mass and stiffness and the effect of the different cap ply layers is a variation in terms of mobility. The results obtained for a group of samples have been compared with those coming from the dynamic characterization of the corresponding final tire and their acoustic measurements, showing a good correlation between the measurement on samples and entire tires. The performed measurements suggest that the new approach produce interesting results and this procedure can be effectively used. For sure other test on other samples must be performed to confirm the first results and to define a database of materials. In conclusion it can be said that an innovative measurement set-up for the dynamic characterization of rolling tire has been developed and validated. Both sidewall and crown can be characterized with the new set-up. At the same time, an innovative approach for noise reduction based on the characterization of tire components has been proposed.

Sensor-embedded tires, known as intelligent tires, have been widely studied because they are believed to provide reliable and crucial information on tire-road contact characteristics e.g., slip, forces and deformation of tires. Vehicle control systems such as ABS and VSP (Vehicle Stability Program) can be enhanced by leveraging this information since control algorithms can be updated based on directly measured parameters from intelligent tire rather than estimated parameters based on complex vehicle dynamics and on-board sensor measurements. Moreover, it is also expected that intelligent tires can be utilized for the purpose of the analysis of tire characteristics, taking into consideration that the measurements from the sensors inside the tire would contain considerable information on tire behavior in the real driving scenarios. In this study, estimation methods for the tire-road contact features by utilizing intelligent tires are investigated. Also, it was discussed how to identify key tire parameters based on the fusion technology of intelligent tire and tire modeling. To achieve goals, extensive literature reviews on the estimation methods using the intelligent tire system was conducted at first. Strain-based intelligent tires were introduced and tested in the laboratory for this research. Based on the literature review and test results, estimation methods for diverse tire-road contact characteristics such as slippages and contact forces have been proposed. These estimation methods can be grouped into two categories: statistical regressions and model based methods. For statistical regressions, synthetic regressors were proposed for the estimation of contact parameters such as contact lengths, rough contact shapes, test loads and slip angles. In the model-based method, the brush type tire model was incorporated into the estimation process to predict lateral forces. Estimated parameters using suggested methods agreed well with measured values in the laboratory environment. By utilizing sensor measurements from intelligent tires, the tire physical characteristics related to in-plane dynamics of the tire, such as stiffness of the belt and sidewall, contact pressure distribution and internal damping, were identified based on the combination of strain measurements and a flexible ring tire model. The radial deformation of the tread band was directly obtained from strain measurements based on the strain-deformation relationship. Tire parameters were identified by fitting the radial deformations from the flexible ring model to those derived from strain measurements. This approach removed the complex and repeated procedure to satisfy the contact3 constraints between the tread and the road surface in the traditional ring model. For tires with different specifications, identification using the suggested method was conducted and their results are compared with results from conventional methods and tests, which shows good agreements. This approach is available for the tire standing still or rolling at low speeds. For tires rolling at high speeds, advanced tire model was implemented and associated with strain measurements to estimate dynamic stiffness, internal damping effects as well as dynamic pressure distributions. Strains were measured for a specific tire under various test conditions to be used in suggested identification methods. After estimating key tire parameters step by step, dynamic pressure distributions was finally estimated and used to update the estimation algorithm for lateral forces. This updated estimation method predicted lateral forces more accurately than the conventional method. Overall, this research will serve as a stepping stone for developing a new generation of intelligent tire capable of monitoring physical tire characteristics as well as providing parameters for enhanced vehicle controls.
PHD

Tire performance over soft soil influences the performance of off-road vehicles on soft soil, as the tire is the only force transmitting element between the off-road vehicles and soil during the vehicle operation. One aspect of the tire performance over soft soil is the tire tractive performance on soft soil, and it attracts the attention of vehicle and geotechnical engineers. The vehicle engineer is interested in the tire tractive performance on soft soil because it is related to vehicle mobility and energy efficiency; the geotechnical engineer is concerned about the soil compaction, brought about by the tire traffic, which accompanies the tire tractive performance on soft soil. In order to improve the vehicle mobility and energy efficiency over soft soil and mitigate the soil compaction, it's essential to develop an in-depth understanding of tire tractive performance on soft soil. This study has enhanced the understanding of tire tractive performance on soft soil and promoted the development of terramechanics and tire model parameterization method through experimental tests. The experimental tests consisted of static tire deflection tests, static tire-soil tests, soil properties tests, and dynamic tire-soil tests. The series of tests (test program) presented herein produced parameterization and validation data that can be used in tire off-road traction dynamics modeling and terramechanics modeling. The 225/60R16 97S Uniroyal (Michelin) Standard Reference Test Tire (SRTT) and loamy sand were chosen to be studied in the test program. The tests included the quantification or/and measurement of soil properties of the test soil, pre-traffic soil condition, the pressure distribution in the tire contact patch, tire off-road tractive performance, and post-traffic soil compaction. The influence of operational parameters, e.g., tire inflation pressure, tire normal load, tire slip ratio, initial soil compaction, or the number of passes, on the measurement data of tire performance parameters or soil response parameters was also analyzed. New methods of the rolling radius estimation for a tire on soft soil and of the 3-D rut reconstruction were developed. A multi-pass effect phenomenon, different from any previously observed phenomenon in the available existing literature, was discovered. The test data was fed into optimization programs for the parameterization of the Bekker's model, a modified Bekker's model, the Magic Formula tire model, and a bulk density estimation model. The modified Bekker's model accounts for the slip sinkage effect which the original Bekker's pressure-sinkage model doesn't. The Magic Formula tire model was adapted to account for the combined influence of tire inflation pressure and initial soil compaction on the tire tractive performance and validated by the test data. The parameterization methods presented herein are new effective terramechanics model parameterization methods, can capture tire-soil interaction which the conventional parameterization methods such as the plate-sinkage test and shear test (not using a tire as the shear tool) cannot sufficiently, and hence can be used to develop tire off-road dynamics models that are heavily based on terramechanics models. This study has been partially supported by the U.S. Army Engineer Research and Development Center (ERDC) and by the Terramechanics, Multibody, and Vehicle (TMVS) Laboratory at Virginia Tech.
Doctor of Philosophy
Big differences exist between a tire moving in on-road conditions, such as asphalt lanes, and a tire moving in off-road conditions, such as soft soil. For example, for passenger cars commonly driven on asphalt lanes, normally, the tire inflation pressure is suggested to be between 30 and 35 psi; very low inflation pressure is also not suggested. By contrast, for off-road vehicles operated on soft soil, low inflation pressure is recommended for their tires; the inflation pressure of a tractor tire can be as low as 12 psi, for the sake of low post-traffic soil compaction and better tire traction. Besides, unlike the research on tire on-road dynamics, the research on off-road dynamics is still immature, while the physics behind the off-road dynamics could be more complex than the on-road dynamics. In this dissertation, experimental tests were completed to study the factors influencing tire tractive performance and soil behavior, and model parameterization methods were developed for a better prediction of tire off-road dynamics models. Tire or vehicle manufacturers can use the research results or methods presented in this dissertation to offer suggestions for the tire or vehicle operation on soft soil in order to maximize the tractive performance and minimize the post-traffic soil compaction.

Ce projet porte sur la production et la caractérisation de composites hybrides basés sur un polymère thermoplastique (polyéthylène linéaire de basse densité, LLDPE) avec des fibres de polyester de pneus recyclés (RTF) mélangées avec le caoutchouc des pneus usés (GTR) avec et sans styrène-éthylène-butylène-styrène greffé d’anhydride maléique (SEBS-g-MA) comme compatibilisant. L'étude vise à améliorer les propriétés du LLDPE avec le RTF, GTR et SEBS-g-MA. La première étape de l'étude est composée de deux parties principales. La première partie porte sur la caractérisation des RTF par spectroscopie infrarouge à transformée de Fourier (FTIR), spectroscopie des photoélectrons X (XPS), analyse thermogravimétrique (TGA), calorimétrie différentielle à balayage (DSC), microscopie électronique (SEM) et densité; tandis que la deuxième partie rapporte la morphologie des composites fabriqués à partir de différentes conditions. En particulier, l'effet de la concentration de RTF (10, 25 et 50% en poids) avec et sans 10% poids de SEBS-g-MA à différentes vitesses de vis (110, 180 et 250 rpm) en-dessous (LT) et au-dessus (HT) de la température de fusion du RTF (253°C) est étudié par extrusion double-vis suivie du moulage par injection. Les résultats montrent une meilleure distribution des particules GTR (intégrées au RTF) dans la matrice (LLDPE) avec l'augmentation du contenu en RTF dans les mélanges compatibilisés. En outre, l’augmentation de la vitesse des vis entraîne une réduction de la longueur des RTF et de la taille des GTR. Cependant, un profil HT mène à la dégradation de la matrice et du GTR. Dans la deuxième étape du travail, une série complète de caractérisation physique (densité et dureté) et mécanique (tension, flexion et impact) des échantillons produits dans la première partie est présentée. Malgré la diminution des modules et des contraintes maximales, la résistance au choc Charpy augmente de 50% avec 50% de FTR compatibilisées et une amélioration supplémentaire de 56% à haute vitesse de rotation des vis (250 rpm). Cependant, le profil HT diminue toutes les propriétés physico-mécaniques des mélanges. Finalement, les propriétés rhéologiques des échantillons produits lors de la première partie ont été rhéologiquement caractérisés à l’état fondu (cisaillement oscillatoire de faible amplitude, SAOS) et solide (analyse mécanique dynamique, DMA) afin de déterminer les relations entre la mise en œuvre, la morphologie et les propriétés macroscopiques. Les résultats montrent une augmentation de l'élasticité des mélanges avec l’augmentation du contenu en RTF en présence de SEBS-g-MA surtout à des vitesses de vis élevées. Néanmoins, le profil HT présente une diminution de l'élasticité à l’état fondu, tandis que la DMA montre une augmentation de l’élasticité pour le profil LT.
This project focuses on the production and characterization of hybrid composites based on a thermoplastic polymer (linear low-density polyethylene, LLDPE) and polyester recycled tire fibers (RTF) mixed with ground tire rubber (GTR) with and without styrene-ethylenebutylene-styrene grafted maleic anhydride (SEBS-g-MA) as a compatibilizer. The study aims at improving the properties of LLDPE using RTF, GTR and SEBS-g-MA. The first step is composed of two main parts. The first part is the characterization of RTF via Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and density; while the second part is to report on the morphology from different processing parameters. In particular, the effect of RTF concentration (10, 25 and 50 wt.%) with and without 10 wt.% SEBS-g-MA at different screw speeds (110, 180 and 250 rpm) processed below (LT) and above (HT) the RTF melting temperature (253°C) are investigated for samples produced via twin-screw extrusion followed by injection molding. The results show better GTR particles distribution (imbedded in RTF) in the matrix (LLDPE) with increasing RTF content in the compatibilized compounds. Also, increasing the screw speed leads to a reduction of RTF length and GTR sizes. However, HT profiles produced degradation of the matrix and GTR particles. In the second step, a complete series of physical (density and hardness) and mechanical (tension, flexion and impact) characterization was performed on the samples produced in the first step. Despite lower moduli and strength, Charpy impact strength increases by 50% for compatibilized 50% RTF compounds with an additional 56% improvement at higher screw speed (250 rpm). However, HT profiles decrease all physico-mechanical properties of the samples. Finally, the rheological properties of the samples produced in the first step are investigated in both the melt (small amplitude oscillatory shear, SAOS) and solid (dynamic mechanical analysis, DMA) states to understand the relations between processing, morphology and macroscopic properties. The results show increased elasticity with increasing RTF content with SEBS-g-MA, especially at higher extrusion screw speeds. HT profiles lead to lower elasticity in the melt state, while DMA results show higher elasticity for LT profiles.

Vehicle pull is an issue that occurs when the driver has to exert a discerniblesteering torque (pull) for the vehicle to run straight, otherwisea lateral drift takes place. This thesis deals with the straight motion ofroad vehicles, with particular focus on the role played by tire characteristics,road cross slope and interactions between tires and vehicle.A thorough theoretical approach has been adopted, adjusting thePacejka’s formulation for effective axle characteristics and extendingthe linear handling diagram theory. This has allowed to obtain innovativeanalytical expressions, describing the straight-driving slip anglesand steering torque offsets.The analytical expressions have been validated, together with asingle-track model, by means of quasi-static and dynamic simulationsof a full-vehicle model. Moreover, a relationship between tire characteristicsand on-center handling has been described, that relates objectivemetrics with subjective feedback.The obtained analytical expressions can be used by vehicle OriginalEquipment Manufacturers (OEMs) or Tire Suppliers for productdevelopment.
Däckinducerad fordonsavdrift är ett problem som medför att förarenmåste utöva ett märkbart-styrmoment för att fordonet ska köra rakt.Detta examensarbete handlar om bilens avdrift vid körning rakt fram,med särskild fokus på inverkan av däckegenskaper, vägens lateralalutning och samverkan mellan däck och fordon.Ett grundligt teoretiskt tillvägagångssätt har valts: Pacejkas formuleringav effektiva axelegenskaper har anpassats, och den linjära handlingdiagram teorin har expanderats. Detta har gjort det möjligt att erhållainnovativa analytiska ekvationer som beskriver de avdriftsvinklaroch styrmoment som krävs för att fordonet ska färdas rakt fram.De analytiska ekvationerna har validerats, med hjälp av en cykelmodellsamt med kvasi-statiska och dynamiska simuleringar av enhelfordonsmodell. Dessutom har ett samband mellan däckegenskaperoch kursstabilitet tagits fram, som relaterar objektiva parametrar medsubjektiv feedback.De erhållna analytiska ekvationerna kan användas av fordonstillverkareoch däckleverantörer för produktutveckling.

In any automotive system, the tires play a very crucial role in defining both the safety and performance of the vehicle. The interaction between the tire and the road surface determines the vehicle's ability to accelerate, decelerate and steer. Having information about this interaction in real-time can be very valuable for the on-board advanced active safety systems to mitigate the risks ahead of time and keep the vehicle stable. The crucial information which can be obtained from the tire includes but are not limited to tire-road friction, tire forces (longitudinal, lateral), normal load, road surface characteristics and tire pressure. This information can be acquired through indirect vehicle dynamics based estimation algorithms or through direct measurements using sensors inside the tire. However, the indirect estimations fail to give an accurate measure of the vehicle state in certain conditions (e.g. side winds, road banking, surface change) and require ABS or VSC activation before the estimation begins. Therefore, to improve the performance of these active stability systems, direct measurement based approaches must be explored. This research expands the applications of Intelligent tire and focuses on using the sensor based measurement approach to develop estimation algorithms relating to tire force measurement. A tri-axial accelerometer is attached to the inner liner of the tire (Intelligent Tire) and two of such tires are placed on an instrumented (MSW, VBox, IMU, Encoders) VW Jetta. Different controlled tests are carried out on the instrumented vehicle and the Intelligent tire signal is analyzed to extract features related to the tire forces and pressure. Due to unavailability of direct force measurements at the wheel, a VW Jetta simulation model is developed in CarSim and the extracted features are validated with a good correlation.
Master of Science

Tire-Pavement Interaction Noise (TPIN) becomes the main noise source contributor for passenger vehicles traveling at speeds above 40 kph. Therefore, it represents one of the main contributors to noise environmental pollution in residential areas nearby highways. TPIN has been subject of exhaustive studies since the 1970s. Still, almost 50 years later, there is still not an accurate way to model it. This is a consequence of a large number of noise generation mechanisms involved in this phenomenon, and their high complexity nature. It is acknowledged that the main noise mechanisms involve tire vibration, and air pumping within the tire tread and pavement surface. Moreover, TPIN represents the only vehicle noise source strongly affected by an external factor such as pavement roughness. For the last decade, new machine learning algorithms to model TPIN have been implemented. However, their development relay on experimental data, and do not provide strong physical insight into the problem. This research studied the correct configuration of such tools. More specifically, Artificial Neural Network (ANN) configurations were studied. Their implementation was based on the problem requirements (acoustic sound pressure prediction). Moreover, a customized neuron configuration showed improvements on the ANN TPIN prediction capabilities. During the second stage of this thesis, tire noise test was undertaken for different tires at different pavements surfaces on the Virginia Tech SMART road. The experimental data was used to develop an approach to account for the pavement profile when predicting TPIN. Finally, the new ANN configuration, along with the approach to account for pavement roughness were complemented using previous work to obtain what is the first reasonable accurate and complete tool to predict tire noise. This tool uses as inputs: 1) tire parameters, 2) pavement parameters, and 3) vehicle speed. Tire noise narrowband spectra for a frequency range of 400-1600 Hz is obtained as a result.
Master of Science
Tire-Pavement Interaction Noise (TPIN) becomes the main noise source contributor for passenger vehicles traveling at speeds above 40 kph. Therefore, it represents one of the main contributors to noise environmental pollution in residential areas nearby highways. TPIN has been subject of exhaustive studies since the 1970s. Still, almost 50 years later, there is still not an accurate way to model it. This is a consequence of a large number of noise generation mechanisms involved in this phenomenon, and their high complexity nature. It is acknowledged that the main noise mechanisms involve tire vibration, and air pumping within the tire tread and pavement surface. Moreover, TPIN represents the only vehicle noise source strongly affected by an external factor such as pavement roughness. For the last decade, machine learning algorithms, based on the human brain structure, have been implemented to model TPIN. However, their development relay on experimental data, and do not provide strong physical insight into the problem. This research focused on the study of the correct configuration of such machine learning algorithms applied to the very specific task of TPIN prediction. Moreover, a customized configuration showed improvements on the TPIN prediction capabilities of these algorithms. During the second stage of this thesis, tire noise test was undertaken for different tires at different pavements surfaces on the Virginia Tech SMART road. The experimental data was used to develop an approach to account for the pavement roughness when predicting TPIN. Finally, the new machine learning algorithm configuration, along with the approach to account for pavement roughness were complemented using previous work to obtain what is the first reasonable accurate and complete computational tool to predict tire noise. This tool uses as inputs: 1) tire parameters, 2) pavement parameters, and 3) vehicle speed.

The growth of the automobile Industry in the past 50 years is radical. The development of chassis control systems have grown drastically due to the demand for safer, faster and more comfortable vehicles. For example, the invention of Anti-lock Braking System (ABS) has resulted in saving more than a million lives since its adaptation while also allowing the vehicles to commute faster. As we move into the autonomous vehicles era, demand for additional information about tire-road interaction to improve the performance of the onboard chassis control systems, is high. This is due to the fact that the interaction between the tire and the road surface determines the stability boundary limits of the vehicles. In this research, a real-time system to classify the road surface into five major categories was developed. The five surfaces include Dry Asphalt, Wet Asphalt, Snow, and Ice and dry Concrete. tri-axial accelerometers were placed on the inner liner of the tires. An advanced signal processing technique was utilized along with a machine learning model to classify the road surfaces. The instrumented Volkswagen Jetta with intelligent tires was retrofitted with new instrumentation for collecting data and evaluating the performance of the developed real-time system. A comprehensive study on road surface classification was performed in order to determine the features of the classification algorithm. Performance of the real-time system is discussed in details and compared with offline results.
Master of Science

Abstract Tires, the only vehicle component in contact with the road, are crucial in determining vehicle dynamics. However, as the tires travel substantially, different wear patterns such as feather, spotty, and camber wear are introduced in different parts of the tire’s tread due to contact with the road surface, improper tire inflation pressure, and tire alignment issues. This tire wear phenomenon affects vehicle performance and is detrimental to vehicle-road safety. This research has developed a framework for tire wear classification based on the “Intelligent Tires” concept. This intelligent tire comprises tri-axis accelerometers mounted on the tire’s inner liner for data corresponding to the tire-road contact interface. A vehicle was instrumented with different proprioceptive and exteroceptive sensors for testing and data collection. Tires with different tread depths have been tested under various test conditions of velocity, tire inflation pressure, road surface, and tire normal load. Multiple signal processing techniques in time, frequency, and spatial domains have been leveraged for feature extraction. These features serve as inputs to machine learning based classification algorithms to distinguish between normal and worn-out tires. Thus, the developed system capitalizes on intelligent tire data to predict the state of the tire as normal or worn-out, with real-time capabilities.

In this paper, we present the development of a tire deformation sensing system that can provide the critical information for estimation of tire/road interaction for mobile robots and vehicles. Polyvinylidene fluoride (PVDF)-based sensor is designed and fabricated to embed on the inner tread surface to measure the rubber tread deformation. Analytical models of the PVDF-based sensing system are presented to capture the tire/road contact information and friction characteristics. The sensed deformation measurements are integrated with the on-board control system through a wireless data transmission module. Experimental results on a skid-steered mobile robot are presented to show the feasibility of the developed sensing system.