Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance in a laboratory environment using classical and freestyle techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance coefficient, µR, in order to allow correct comparisons between the results, as well as providing the opportunity to study work economy between different athletes, test occasions and core techniques. Thus, one of the aims of this thesis was to evaluate how roller skis’ µR is related to warm-up, mass, velocity and inclination of the treadmill. It was also necessary to investigate the methodological variability of the rolling resistance measurement system, RRMS, specially produced for the experiments, with a reproducibility study in order to indicate the validity and reliability of the results. The aim was also to study physiological responses to different µR during roller skiing with freestyle and classical roller skis and techniques on the treadmill as a case in which all measurements were carried out in stationary and comparable conditions. Finally, the aim was also to investigate the work economy of amateurs and female and male junior and senior cross-country skiers during treadmill roller skiing, i.e. as a function of skill, age and gender, including whether differences in body mass causes significant differences in external power per kg due to differences in the roller skis’ µR. The experiments showed that during a warm-up period of 30 minutes, µR decreased to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively. For another 30 minutes of rolling no significant change was found. Simultaneous measurements of roller ski temperature and mR showed that stabilized mR corresponds to a certain running temperature for a given normal force on the roller ski. The study of the influence on mR of normal force, velocity and inclination produced a significant influence of normal force on mR, while different velocities and inclinations of the treadmill only resulted in small changes in mR. The reproducibility study of the RRMS showed no significant differences between paired measurements with either classical or the freestyle roller skis. The study of the effects on physiological variables of ~50% change in µR,showed that during submaximal steady state exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a significantly changed maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non significant or small. The final part of the thesis, which focused on work economy, found no significant difference between the four groups of elite competitors, i.e. between the two genders and between the junior and senior elite athletes. It was only the male amateurs who significantly differed among the five studied groups. The study also showed that the external power per kg was significantly different between the two genders due to differences in body mass and mR, i.e. the lighter female testing groups were roller skiing with a relatively heavier rolling resistance coefficient compared to the heavier testing groups of male participants. / Sporttech

Every moment of every day, at least hundreds of thousands of tires roll across a surface throughout the world. Tires are indisputably important in our daily life. The tire's primary component is rubber, which consumes energy when it rotates on a substrate due to the viscoelastic material's internal friction: a phenomenon referred to as rolling resistance. The interaction between the tire and the road surface is one of the most intricate and crucial phenomena in an automobile, because it is responsible for creating forces, moments, and deformation in the tire. Additionally, the road's roughness interacts with the tire and contributes significantly to its performance. This dissertation aims to develop a comprehensive physics-based model for predicting the rolling resistance of a viscoelastic material due to dynamic deformations caused by tire rotation using an analytical approach. The model was developed by proposing a Gaussian wave function propagating across a tire circumference's viscoelastic medium. The wave function was selected to describe the displacement field produced by tire-road interaction. Additionally, by adopting a multi-scale modeling technique, the model was upgraded to estimate rolling resistance while taking into account surface roughness at all length scales, from macroscopic to microscopic. Additionally, another mathematical model was developed using the Fourier series approach to evaluate the steady-state stress response and energy dissipation for any harmonic and non-harmonic periodic strain signals. Additionally, the dissertation strove to build a continuum damage mathematical model using a combined testing/modeling methodology to predict the aging of Styrene-Butadiene Rubber (SBR) after continuous exposure to the atmosphere. The obtained model was developed through the implementation of optimization techniques while formulating a mathematical model, which was then combined with a physics-based model to predict rolling resistance while taking into account rubber aging. Calibration of hyperelastic and viscoelastic material models with testing data was performed using an optimization technique that yielded sufficient results. The results of all mathematical models obtained in this dissertation are reported subsequently. The stress response of a viscoelastic material under harmonic and non-harmonic strain input yielded good agreement with the FEA model obtained using ABAQUS. The rolling resistance behavior under various operating conditions, including texture and aging effects, was reported, and the results aligned with the experimental results found in the literature. / Doctor of Philosophy / Every moment of every day, hundreds of thousands of automobile tires roll across a surface somewhere in the world. A tire is an undeniably important part of everyday life. Rubber is the tire's main component, and when it rotates on a surface, it loses energy, resulting in a force that resists motion, known as rolling resistance force. The contact between the tire and the road is one of the most complicated and important phenomena that happens in an automobile because it is responsible for the vehicle's dynamic performance in areas such as acceleration, stopping distance, and stability. Another factor that affects tire and car performance and should be taken into account is the road's roughness. This dissertation used an analytical method to come up with an accurate physics-based model for predicting the rolling resistance force of a viscoelastic material caused by tire rotation. The model was developed by assuming a Gaussian wave function would move across the tire circumference. Additionally, using a multi-scale modeling technique, the model was improved so that it could calculate the value of rolling resistance force considering surface roughness in all lengths of scale. This project also developed an additional mathematical model using the Fourier series method to determine how the stress response and energy dissipation would behave for any harmonic and nonharmonic periodic strain signals. Additionally, the dissertation presents the developing of a continuum damage mathematical model that could predict the material property of styrene-butadiene rubber (SBR) after being exposed to the air for a long time (i.e., aged). The model was developed based on experimental data and optimization techniques. This model was then combined with a physics-based model to predict rolling resistance force while taking aging into account. The material models were defined using an optimization method that yielded good results. The stress response of a viscoelastic material when it was subjected to harmonic and non-harmonic strain was in good agreement with the Finite Element Analysis (FEA) model made with ABAQUS. Rolling resistance behavior was observed, and the results were consistent with those found in the literature.

An operating vehicle requires energy to oppose the subjected driving resistances. This energy is supplied via the fuel combustion in the engine. Decreasing the opposing driving resistances for an operating vehicle increases its fuel efficiency: an effect which is highly valued in today’s industry, both from an environmental and economical point of view. Therefore a lot of progress has been made during recent years in the area of fuel efficient vehicles, even though some driving resistances still rises perplexity. These resistances are the air drag Fd generated by the viscous air opposing the vehicles propulsion and the rolling resistance Frr generated mainly by the hysteresis caused by the deformation cycle of the viscoelastic pneumatic tires. The energy losses associated with the air drag and rolling resistance account for the majority of the driving resistances facing an operating vehicle, and depends on numerous stochastic and ambient parameters, some of which are highly correlated both within and between the two resistances. To increase the understanding of the driving mechanics behind the energy losses associated with the complexity that is rolling resistance, a set of complete vehicle tests has been carried out. These tests were carried out on the test track Malmby Fairground, using a Scania CV AB developed R440 truck equipped with various sensors connected in one measurement system. Under certain conditions, these parameters can allow for an investigation of the rolling resistance, and a separation of the rolling resistance and air drag via explicit subtraction of the air drag from the measured traction force. This method is possible since the aerodynamic property AHDVCd(β) to some extent can be generated from wind tunnel tests and CFD simulations. Two measurement series that enable the above formulated method of separation were designed and carried out, using two separate measurement methods. One which enables the investigation of the transient nature of rolling resistance as it strives for stationarity, where the vehicle is operated under constant velocities i.e. no acceleration, and one using the well established method of coastdown, where no driving torque is applied. The drive cycles spanned a range of velocities, which allowed for dynamic and stationary analyses of both the tire temperature- and the velocity dependence of rolling resistance. When analysing the results of the transient analysis, a strong dependence upon tire temperature for given constant low velocity i.e. v ≤ 60 kmh−1 was clearly visible. The indicated dependency showed that the rolling resistance decreased as the tire temperature increased over time at a given velocity, and vice versa, towards a stationary temperature and thereby rolling resistance. The tire temperature evolution from one constant velocity to another, took place well within 50 min to a somewhat stationary value. However, even though the tire temperature had reached stationarity, rolling resistance did not; there seemed to be a delay between stationary tire temperature, and rolling resistance. The results did not indicate any clear trends for v ≥ 60 kmh−1, where the results at v = 80 kmh−1 were chaotic. This suggests that some additional forces were uncompensated for, or that the compensation for air drag was somehow wrongly treated at higher velocities. Several factors ruled out any attempts at proposing a new rolling resistance model. These included: the chaotic results for v = 80 kmh−1, the delayed rolling resistance response upon tire temperature stabilization, and the lack of literature support for the observed tendency. The results from the coastdown series on the other hand, showed good agreement with a dynamical model suggested in literature. The stationary temperature behaviour for the considered velocity range at assumed constant condition is also supported in literature. Finally, an investigation of the aerodynamic property AHDVCd inspired by ongoing work in ACEA (European Automobile Manufacturers’ Association), was carried out assuming both zero and non-zero air drag at low velocities. The results indicated surprisingly good agreement with wind tunnel measurements, especially when neglecting air drag at low velocities: as suggested by ACEA. / För att övervinna de motstånd som ett fordon utsätts för under drift krävs energi, vilket levereras genom förbränningen av bränsle. Genom att minska de körmotstånd som ett fordon utsätts för under drift, kan man öka dess energieffektivitet. Denna potential är idag högt värderad i fordonsindustrin, både ur ett miljömässigt och ekonomiskt perspektiv. På senare år har stora framsteg gjorts inom området energieffektiva fordon, men fortfarande råder det förvirring kring de energiförluster som förknippas med luftmotstånd Fd och rullmotstånd Frr, där luftmotståndet skapas av den omkringliggande viskösa luften, medan rullmotståndet genereras av hysteresen som uppstår när fordonets viskoelastiska pneumatiska däck utsätts för deformation. De energiförluster som förknippas med luft- och rullmotstånd motsvarar den största delen av de motstånd som ett fordon påverkas av, och beror på en mängd stokastiska och yttre parametrar, varav vissa är starkt korrelerade både inom och mellan nämnda motstånd. För att förbättra förståelsen kring dessa energiförluster, med fokus på förståelsen av rullmotstånd, har ett antal helfordonstest genomförts. Dessa genomfördes på provbanan Malmby Fairground med en R440 lastbil från Scania CV AB, utrustad med en mängd sensorer sammankopplade i ett mätsystem. Det uppbyggda mätsystemet möjliggjorde samtida mätningar av bl.a. drivande moment, motorvarv, fordonshastighet, däcktemperatur, omkringliggande lufts hastighet och dess riktning. Under specifika förhållanden kunde dessa parametrar möjliggöra analys av rullmotstånd genom en explicit subtraktion av luftmotstånd från den uppmätta drivande kraften. Denna metod är möjlig tack vare en förhållandevis bra modell av ekipagets aerodynamiska egenskap AHDVCd(β), som generats från vindtunneltest och CFD simuleringar. Två körcykler som möjliggjorde ovan formulerade separation designades och genomfördes. Dessa använder två skilda mätmetoder, varav den ena möjliggör analys av rullmotståndets övergående förlopp från dynamiskt till stationärt genom att hålla konstant hastighet. Den andra studerade det dynamiska förloppet genom den väletablerade metoden utrullning, dvs. utan något drivande moment. Dessa körcyklar genomfördes, för ett antal hastigheter, vilket möjliggjorde analys av både hastighets- och däcktemperaturberoendet hos rullmotstånd, under dynamiska såväl som stationära förlopp. Analysen av rullmotståndets dynamik i strävan mot stationära förhållanden visade på ett starkt temperaturberoende vid låga hastigheter dvs. v ≤ 60 kmh−1. Beroendet visade på att rullmotståndet avtog med ökande däcktemperatur och vice versa, tills dess att en någorlunda stationär temperatur för given hastighet uppnåtts. Däcktemperaturen stabiliserades till ett nytt stationärt värde inom 50 min från att hastigheten ändrats. Resultaten tyder dock på att även om stationär däcktemperatur uppnåtts finns det en fördröjning i rullmotståndets tidsspann innan rullmotståndet stabiliserat sig. För högre hastigheter, dvs. v ≥ 60 kmh-1, var dock inga klara trender synliga, varken i hastighet eller temperatur och resultaten vid v = 80 kmh-1 var kaotiska. Detta antyder att man missat att kompensera för någon kraft vid höga hastigheter, alternativt att man på något sätt kompenserar fel för luftmotståndet vid högre hastigheter. Flera faktorer hindrade försök att föreslå någon ny rullmotståndsmodell. Dessa faktorer inkluderar det kaotiska resultatet vid v = 80 kmh-1, tidsfördröjningen mellan stationärt rullmotstånd och däcktemperatur samt att resultatet för antagna stationära värden inte finner stöd i litteraturen. Resultatet från utrullningsprovet överstämmer dock bra med tidigare föreslagen dynamisk modell, samt att resultaten av beteendet hos stationär temperatur för olika hastigheter även de överensstämmer med och finner stöd i litteraturen. Slutligen har en studie kring den aerodynamiska egenskapen AHDVCd, inspirerad av pågående arbete inom ACEA (European Automobile Manufacturers’ Association) utförts både med antagandet av ett noll- skilt och med ett försumbart luftmotstånd vid låga hastigheter. Resultatet visar på en överraskande god överensstämmelse med vindtunnelmätningar, framför allt under antagandet av försumbart luftmotstånd vid låga hastigheter i enlighet med förslagen metod från ACEA.

The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders. / Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbrukning), hjärtfrekvensen ökade, den framåtdrivande kraften från benen på rullskidorna minskade samt att det blev kortare tid till utmattning (~30 %), vid maxtest, när skidåkarna använde rullskidor med en μS i likhet med vad som rapporterats för skidåkning på snö. För arbetsförsöken med olika rullskidor av olika fabrikat med en högre, och likartad, μS förelåg ingen skillnad i de undersökta variablerna.Studien som undersökte åkekonomi och mekanisk verkningsgrad som funktion av prestationsnivå, ålder och kön, visade att elitskidåkarna hade bättre åkekonomi och verkningsgrad (5-18 %) i jämförelse med motionärerna, att seniorerna hade bättre åkekonomi och verkningsgrad (4-5 %) än juniorerna och att ingen skillnad kunde konstateras mellan könen.

Development of electric vehicles is motivated by global concerns over the need for environmental protection. In addition to its zero-emission characteristics, an electric propulsion system enables high performance torque control that may be used to maximize vehicle performance obtained from energy-efficient, low rolling resistance tires typically associated with degraded road-holding ability. A simultaneous plant/controller optimization is performed on an electric vehicle traction control system with respect to conflicting energy use and performance objectives. Due to system nonlinearities, an iterative simulation-based optimization approach is proposed using a system model and a genetic algorithm (GA) to guide search space exploration. The system model consists of: a drive cycle with a constant driver torque request and a step change in coefficient of friction, a single-wheel longitudinal vehicle model, a tire model described using the Magic Formula and a constant rolling resistance, and an adhesion gradient fuzzy logic traction controller. Optimization is defined in terms of the all at once variable selection of: either a performance oriented or low rolling resistance tire, the shape of a fuzzy logic controller membership function, and a set of fuzzy logic controller rule base conclusions. A mixed encoding, multi-chromosomal GA is implemented to represent the variables, respectively, as a binary string, a real-valued number, and a novel rule base encoding based on the definition of a partially ordered set (poset) by delta inclusion. Simultaneous optimization results indicate that, under straight-line acceleration and unless energy concerns are completely neglected, low rolling resistance tires should be incorporated in a traction control system design since the energy saving benefits outweigh the associated degradation in road-holding ability. The results also indicate that the proposed novel encoding enables the efficient representation of a fix-sized fuzzy logic rule base within a GA.

Development of electric vehicles is motivated by global concerns over the need for environmental protection. In addition to its zero-emission characteristics, an electric propulsion system enables high performance torque control that may be used to maximize vehicle performance obtained from energy-efficient, low rolling resistance tires typically associated with degraded road-holding ability. A simultaneous plant/controller optimization is performed on an electric vehicle traction control system with respect to conflicting energy use and performance objectives. Due to system nonlinearities, an iterative simulation-based optimization approach is proposed using a system model and a genetic algorithm (GA) to guide search space exploration. The system model consists of: a drive cycle with a constant driver torque request and a step change in coefficient of friction, a single-wheel longitudinal vehicle model, a tire model described using the Magic Formula and a constant rolling resistance, and an adhesion gradient fuzzy logic traction controller. Optimization is defined in terms of the all at once variable selection of: either a performance oriented or low rolling resistance tire, the shape of a fuzzy logic controller membership function, and a set of fuzzy logic controller rule base conclusions. A mixed encoding, multi-chromosomal GA is implemented to represent the variables, respectively, as a binary string, a real-valued number, and a novel rule base encoding based on the definition of a partially ordered set (poset) by delta inclusion. Simultaneous optimization results indicate that, under straight-line acceleration and unless energy concerns are completely neglected, low rolling resistance tires should be incorporated in a traction control system design since the energy saving benefits outweigh the associated degradation in road-holding ability. The results also indicate that the proposed novel encoding enables the efficient representation of a fix-sized fuzzy logic rule base within a GA.

This thesis deals with no delay gear shifting. The first part is devoted to theoretical introduction. The next part describes comprehensive approach to vehicle dynamics, the choice of gear ratios, the use of reverse engineering to model the interior of the gear housing and the actual structural design of the internal components and strength analysis. Moreover, this work should fill the gap in the available literature which is publicly accessible.

his thesis deals with the analysis of particular road resistances that affect the car. It describes their importance and factors that influence their size. This thesis defines steps that determine particular quantities that are necessary to assess road resistances. Describing, it qualifies transfer and sizes of driving force that is needed to overcome total road resistance, measuring methods of road range tests upon appropriation of road resistances and influence of road resistances on economy of traffic. Practical part discusses the plan and course of realized measuring of selected sample of cars. Final part deals with the evaluation of measured values of realized measuring.

Energi är en resurs som måste användas effektiv för att undvika onödig negativ miljöpåverkan och utgifter. Återmatning från nedåtgående malmtåg till uppåtgående malmtåg leder till en effektivisering i energiutnyttjande. Beräkningen av den återmatade energin utgår ifrån tågets lägesenergi och förlusterna från räls, lutning, vind och kurvor. Totalt kan återmatning av energi ge en besparing på 20 % för enkelspår och 20 % respektive 21 % för dubbelspår. Dubbelspår kan ha mer trafik än enkelspår men förhållandet mellan konsumerad och återmatad energi är i princip den samma. Återmatning av energi minskar järnvägens negativa påverkan på miljön. Företagens utgifter minskas med denna besparing då mindre energi behövs köpas in utifrån. / Energy is a limited recourse and the use of energy has to be as effective as possible to avoid harmful effects on the environment and to cut spending. Reusing the energy the ore train uses to climb the mountains of northern Sweden through regenerative breaking leads to a more effective use of energy. Calculation of energy uses the trains’ stored energy and the losses during its journey along Malmbanan. This results in a total power save of 20 % for single track and between 20 % and 21 % for double track. Traffic on double track can increase but the relationship between regenerated and consumed energy will be the same. Regenerating energy on the railway reduces today’s negative impact on the environment and leads to savings in energy cost for the company.