19 research outputs found

    A multisensing setup for the intelligent tire monitoring

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    The present paper offers the chance to experimentally measure, for the first time, the internal tire strain by optical fiber sensors during the tire rolling in real operating conditions. The phenomena that take place during the tire rolling are in fact far from being completely understood. Despite several models available in the technical literature, there is not a correspondently large set of experimental observations. The paper includes the detailed description of the new multi-sensing technology for an ongoing vehicle measurement, which the research group has developed in the context of the project OPTYRE. The experimental apparatus is mainly based on the use of optical fibers with embedded Fiber Bragg Gratings sensors for the acquisition of the circumferential tire strain. Other sensors are also installed on the tire, such as a phonic wheel, a uniaxial accelerometer, and a dynamic temperature sensor. The acquired information is used as input variables in dedicated algorithms that allow the identification of key parameters, such as the dynamic contact patch, instantaneous dissipation and instantaneous grip. The OPTYRE project brings a contribution into the field of experimental grip monitoring of wheeled vehicles, with implications both on passive and active safety characteristics of cars and motorbikes

    In-plane Tire Deformation Measurement Using a Multi-Laser Sensor System

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    The interactions between tires and roads are basic mechanisms that alter the dynamic states of vehicles. A fundamental understanding of tire-road interactions is clearly demanded in tire design to achieve performance improvements. The emergence of various tire sensors provides an opportunity to make accurate measurement of the physical quantities that are involved in tire-road interactions.  This thesis aims to measure and analyze the in-plane deformation of rolling tires through its direct correlations with the steady-state in-plane tire forces. To date, there is no existing tire sensor that can measure both the tread and carcass deformations. A multi-laser sensor system has therefor been developed in the thesis to measure the in-plane deformation of different tire parts, including the tread, carcass, and inner liner.  Measurements on tread deformation were conducted on both passenger car and truck tires. A non-uniform tread deformation was observed in the measurement and was interpreted as follows: the asymmetric deformation in the longitudinal direction is a direct indicator of the rolling resistance and the non-uniform deformation in the lateral direction reflects the contribution of separate parts to the rolling resistance. The evolution and variation of tread deformations were investigated with different tire types, operational conditions, and tire states. The deformation of the carcass was first analyzed with the flexible ring tire model and then validated through tire sensor measurements. Coupled deformations of the tire carcass in the tangential and radial directions were observed. Indicators based on measured radial carcass deformations are proposed for the estimation of the in-plane tire forces. In addition, the partial inner contours were also measured for truck tires under static conditions for various inflation pressures and loads. The measurements can help tire designers to obtain optimum inner tire contours.  In summary, this thesis shows that the tire sensor can act as a powerful tool for tire research and development. The relations between the in-plane deformation and in-plane tire forces that have been obtained are useful in gaining an understanding of the physical mechanism of observed phenomena, e.g., the rolling resistance, and in the design of basic estimation algorithms, e.g., for the estimation of in-plane tire forces, which are important factors in the development of green and intelligent tires

    Bituplaning a low dry friction phenomenon of new bituminous road surfaces

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    The potential for binder rich bituminous road surfaces to deliver low levels of dry friction was first noted in 1944. Using established test methods exploiting basic principles of physics first tested in criminal court in the 1940s (and still in use today) it has been possible to show statistically that modern negative textured road surfaces (NTS) deliver levels of dry friction significantly below those considered typical by collision investigators for the more traditional positive textured surfaces (PTS). NTS surfaces are shown to perform relatively worse in the absence of ABS (Anti-Blockier System, Anti-lock braking) than PTS equivalents such as Hot Rolled Asphalt (HRA). Skid tests undertaken on DRY NTS surfaces with ABS braking have been shown to manifest momentary low levels of deceleration similar to those experienced during NOABS tests on the same surfaces and to generate dash like skid marks atypical of ABS tests on DRY PTS surfaces. The ratio of peak to sliding friction also appears lower for dry NTS surfaces than for Dry PTS surfaces documented in the literature.Using high-speed video and false colour infrared imaging it has been possible to see the low friction phenomenon termed “bituplaning”. Vehicles equipped with ABS have also been shown to suffer momentary “bituplanes” resulting in less than optimum performance. Tyre deformation during dry skidding on NTS appears reduced in relation to a PTS equivalent.<br/

    Tien kulutuksen raja-arvot nastarenkaiden tyyppihyväksynnässä

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    Studded tires are the most commonly used winter tire type on Finnish passenger vehicles. Studded tires are also widely used in other Nordic countries and e.g. Russia. They are used to increase the safety properties of the tires, especially on icy road conditions during the winter months. However, studded tires cause road wear, which leads to grooving of the roads and results in more frequent resurfacing of the pavement. Furthermore, they also generate road dust and particle emissions, which may increase respiratory diseases in urban areas during springtime. Studded tires also cause wear on road markings, that has both economical and traffic safety related issues. The use and technical properties of studded tires is regulated in order to reduce their effect on road wear. The use of studded tires in traffic is limited to the winter months. Traditionally the technical regulations have been concerning about the stud dimensions, their location on the tire thread and the stud amount. The studded tire properties can be more freely designed, if their effect on road wear is measured in a so-called over-run test. The over-run test method including the road wear limits are defined by Traficom. The road wear limits in the over-run test were tightened in 2013. Several improvements on the ac-curacy and reliability of the test have been implemented since then. Traficom is preparing a new decree on the type approval of studded tires. This thesis is ordered by Traficom to provide research as a background in the preparation of the new decree. The objective of the thesis was to investigate if it is purposeful to change the cur-rent road wear limits and to analyse the consequence of those possible changes. Suggestions on designating the road wear limits in the over-run test were given based on the observations and results achieved in the thesis. The results presented in this thesis may be utilized in the preparation of the new decree on studded tires. One long-term issue with the over-run test has been the relatively low mass loss compared to the test specimen’s weight. This potentially increases the errors in the test method. One result in the thesis was that the limit values in the over-run test can not be further tightened without increasing the absolute wear during the test.Nastarenkaat ovat yleisimmin käytetty talvirengastyyppi suomalaisissa henkilöautoissa, ja ne ovat laajalti käytössä myös muissa Pohjoismaissa sekä esimerkiksi Venäjällä. Nastarenkaita käytetään talvikuukausina parantamaan renkaiden pito-ominaisuuksia liukkaissa olosuhteissa, erityisellä jäisellä tienpinnalla. Nastarenkaat aiheuttavat kuitenkin tien päällysteen kulumista, mikä johtaa teiden urautumiseen ja tiheämpään uusintapäällystystarpeeseen. Teiden urautuminen lisää myös vesiliirtoriskiä. Nastarenkaista johtuva tienkuluminen lisää myös katupölyn ja pienhiukkasten muodostumista, jotka saattavat aiheuttaa hengitystieongelmia kaupunkialueilla erityisesti keväisin. Tämän lisäksi nastarenkaat kuluttavat myös tiemerkintöjä, millä on sekä taloudellisia että liikenneturvallisuutta vaarantavia vaikutuksia. Nastarenkaista johtuvaa tien kulumista pyritään rajoittamaan määrittelemällä niiden sal-littu vuosittainen käyttöaika, sekä asettamalla vaatimuksia niiden tietyille teknisille ominaisuuksille. Perinteisesti rajoitukset ovat koskeneet nastojen mittoja, nastamäärää ja niiden asettelua renkaan pintakuviossa. Nastarenkaiden tien kuluttavuutta mittaavalla yliajokokeella voidaan kuitenkin hyväksyä vapaammin suunniteltu nastarengas, kunhan sen tien kuluttavuus on viranomaisen määrittelemällä tasolla. Yliajokokeen kulumisrajoja tiukennettiin viimeksi vuonna 2013, jonka jälkeen myös koemenetelmän luotettavuuden parantamiseksi on tehty useita muutoksia. Traficomissa on valmisteilla määräyshanke nastarenkaiden tyyppihyväksynnän osalta. Tämä diplomityö on tilattu kyseisen määräyshankkeen valmistelun tueksi. Diplomityön tavoitteena oli tutkia, onko yliajokokeen kulumisrajoja tarpeen muuttaa ja mitkä olisivat muutoksen mahdolliset vaikutukset. Diplomityössä tehtyjen havaintojen ja tulosten perusteella annettiin ehdotukset tien kulutuksen raja-arvojen asettamiseksi. Tässä tekstissä esitettyjä ehdotuksia voidaan hyödyntää nastarenkaisiin liittyvän määräyshankkeen suunnittelussa. Eräänä pitkäaikaisena haasteena yliajokokeessa on ollut vähäinen kuluma suhteessa testikivien painoon, mikä voi lisätä virheiden mahdollisuutta. Työssä tultiin siihen tulokseen, että yliajokokeen raja-arvoja ei voida laskea lisäämättä kokeen aikana tapahtuvaa absoluuttista kulumaa

    Tien ja renkaan välisen kitkapotentiaalin arviointi inertia-anturin mittausten perusteella alhaisen kitkan olosuhteissa

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    Electronic driver aids have become commonplace in passenger cars in the last two decades. These systems improve safety by attempting to prevent the vehicle from exceeding the limits of its handling and becoming unstable. Those limits are largely defined by the tire-road friction potential. Consequently, the friction potential is one of the variables used in the control logics of these systems. Thus, by estimating the potential, the effectiveness of electronic driver aids can be significantly improved. The purpose of this thesis is to develop and test the accuracy of a novel friction estimation algorithm that uses the accelerations and yaw, pitch, and roll rates of the vehicle measured with an inertial sensor as its basis. The algorithm was designed to account for the effects of inclination and banking, as they influence the acceleration capabilities of the vehicle and the acceleration measurements. Three different versions of the algorithm were created so that the effects of compensating for inclination and bank angle could be assessed. Additionally, the algorithm was designed in such a way that it should be able to estimate the friction potential accurately in start maneuvers where the steering angle is high. The single-track model was incorporated into the algorithm for this purpose. The algorithm must also detect when the vehicle is on the limits of its handling, as it is only then that the measured friction coefficient is equal to the friction potential. The algorithm accomplishes this by monitoring the states of the driver aids. The algorithm was tested with simulations and experimental tests. The research vehicle was modelled in simulation software, including the most significant electronic driver aids. A variety of acceleration, braking, and cornering maneuvers were performed in order to test the capabilities of the algorithm on roads with varying inclinations and bank angles. The tests focused on low-friction conditions, as friction estimation is at its most beneficial in such circumstances. The results show that this novel algorithm is capable of estimating the friction potential accurately in most acceleration, braking, and cornering situations on inclined, banked, and level roads. However, the results also indicate that accounting for the inclination and the bank angle makes little difference in the friction estimation. The algorithm calculates the tire-road forces largely based on the longitudinal and lateral acceleration measurements of the inertial sensor, which contain a component of gravitational acceleration if the road is not level. Thus, the effects of inclination and bank angle get mostly compensated even in the versions that were not specifically designed to account for them. The results also show that the friction potential estimation produced by the single-track model in high steering angle start maneuvers contains significant error due to the two front tires producing forces in different directions in such situations.Elektronisista ajoavuista on tullut yleisiä henkilöautoissa viimeisten kahden vuosikymmenen aikana. Nämä järjestelmät parantavat turvallisuutta yrittämällä estää autoa ylittämästä suorituskykyrajojaan, jolloin auto muuttuu epästabiiliksi. Kyseiset rajat perustuvat laajalti renkaan ja tien väliseen kitkapotentiaaliin. Kitkapotentiaali on siksi yksi niistä muuttujista, joita nämä järjestelmät käyttävät ohjauslogiikoissaan. Täten ajoapujen toimintaa voidaan tehostaa merkittävästi estimoimalla kitkapotentiaalia. Tämän opinnäytetyön tarkoituksena on luoda uudenlainen kitkaestimointialgoritmi, jonka toiminta perustuu inertia-anturilla mitattaviin auton kiihtyvyyksiin ja kallistumis-, nyökkimis- ja pystykiertymänopeuksiin, ja tutkia sen tarkkuutta. Algoritmi suunniteltiin huomioimaan tien nousu- ja sivuttaiskulmien vaikutus, sillä ne vaikuttavat auton kiihtyvyysrajoihin ja mitattuihin kiihtyvyyslukemiin. Algoritmista luotiin kolme eri versiota, jotta tien kulmien kompensoinnin vaikutusta voitaisiin arvioida. Lisäksi algoritmi suunniteltiin siten, että sen pitäisi kyetä arvioimaan kitkapotentiaalia tarkasti myös sellaisissa liikkeellelähtötilanteissa, joissa ohjauskulma on suuri. Kaksipyörämalli sisällytettiin algoritmiin tätä tarkoitusta varten. Algoritmin on myös kyettävä havaitsemaan, milloin auto on lähellä suorituskykyrajojaan, koska arvioitu kitkakerroin on lähellä kitkapotentiaalia vain silloin. Algoritmi toteuttaa tämän tarkkailemalla ajoapujen tiloja. Algoritmia testattiin simulaatioiden ja koeautolla tehtävien testien avulla. Koeauto ja sen merkittävimmät ajoavut mallinnettiin simulaatio-ohjelmistossa. Monenlaisia kiihdytys-, jarrutus- ja kaarreajoliikkeitä suoritettiin algoritmin kykyjen tutkimiseksi erilaisia kallistuksia sisältävillä teillä. Testit keskittyivät alhaisen kitkan olosuhteisiin, sillä kitkaestimoinnista on eniten hyötyä juuri sellaisissa oloissa. Tulokset näyttävät, että luotu algoritmi kykenee arvioimaan kitkapotentiaalia tarkasti useimmissa kiihdytys-, jarrutus- ja kaarreajotilanteissa mäkisillä, kallistetuilla ja tasaisilla teillä. Tulokset kuitenkin myös osoittavat, että nousu- ja sivuttaiskulman huomiointi algoritmissa tuottaa vain pienen eron kitkaestimoinnissa. Algoritmi laskee rengasvoimat perustuen enimmäkseen inertia-anturin pitkittäis- ja sivuttaiskiihtyvyysmittauksiin, jotka sisältävät putoamiskiihtyvyyskomponentin, mikäli tie ei ole tasainen. Täten nousu- ja sivuttaiskulmien vaikutus kompensoituu enimmäkseen pois niissäkin algoritmiversioissa, joita ei erityisesti suunniteltu huomioimaan kyseisiä kulmia. Tulokset näyttävät myös, että kaksipyörämallin tuottama kitkapotentiaaliarvio suuren ohjauskulman liikkeellelähtötilanteissa sisältää merkittävästi virhettä johtuen siitä, että etupyörät tuottavat tällöin voimaa eri suuntiin

    Longer and Heavier Vehicles: An Overview of Technical Aspects

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    Within the frame of the Logistics Action Plan, the European Commission is analysing the impacts of a potential introduction across the EU of Longer and Heavier Vehicles (LHVs), i.e. vehicles measuring up to 25.25 m and weighting up to 60 tons. Such vehicles are expected to improve the efficiency of the road freight sector but their impacts on the environment, infrastructure and safety need to be analysed in more depth. The present study aims at providing an overview of the technical aspects associated with LHVs with regard to energy efficiency, infrastructure (road wear and bridges) and safety issues. This is carried out at vehicle level based on a comparison with standard 40t heavy duty vehicles (HDVs). Some enhancing technologies that can potentially improve the performance of and reduce the damage caused by LHVs are described and issues that require further and detailed research are also identified.JRC.J.2-The economics of climate change, energy and transpor

    Investigation and modelling of rubber friction

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    PhDThe friction between a rubber surface in contact with a rigid surface is still not fully understood. Unlike other materials, friction behaviour in rubber is significantly dependent upon a variety of parameters due to its viscoelastic nature. The aim of this work is to understand frictional phenomena occurring on different length scales of intrest. In the first part of this work the influence of an entirely geometric factor on friction is confirmed by FEA and is validated by experiments for the first time. Under certain conditions, it can increase the frictional force significantly above that expected from a consideration of the interfacial coefficient of friction alone. This term is thought likely to make a considerable contribution to frictional sliding applications such as a tyre on a road surface. In the second part of this work an instability, observed at the rubber surface during sliding, is investigated. Despite experimental research in the past, virtually no information has been published on the modelling of the so-called Schallamach waves using FEA techniques. This work models successive Schallamach waves, giving the opportunity to investigate the transition of individual waves throughout the area of contact, for the first time. The use of FEA allows for a detailed stress and strain analysis at the interface and thus gives new insights into the onset of buckling instabilities. So far, Schallamach waves have only been observed experimentally for optically smooth rubber surfaces, however, during this work, surface waves have been also noticed for rough rubber surfaces. Furthermore, the examination of the frequency dependence of Schallamach waves allows for the consideration of a relationship to stick-slip behaviour. The third part of this work investigates the influence of the rubber surface topography as well as the rigid slider geometry on rubber friction under a wide range of experimental conditions. It was noted that subtle changes of surface finish significantly change the resulting frictional force. The knowledge gained from this can help in the design and understanding of more complex frictional interfaces

    Road Surface Characterization by Near Infrared Light Scattering and Absorption

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    This work is dedicated to creation of a non-contact optical sensor for tire-road friction estimation based on near-infrared radiation scattering and absorption in the case of different road conditions. Here we present implementation of such a sensor based on different detector response to backscattered light from the asphalt surface in four possible conditions: dry, wet, snowy and icy. We discuss light-matter interaction behind the chosen methodology, describe such a sensor prototype and its optical and electric components, perform experimental evaluation of sensor's ability to distinguish these surface types and compare experimental results to computer simulations. Theory, experiment and simulations come in agreement and the road conditions can be determined with the sensor. Additionally, ideas of sensor improvement and further perspectives are discussed
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