No description available.

Wheelchair manufacturers design their products to provide the best possible experience to their users. The user effort and wheelchair mechanical efficiency during motion are highly affected by rolling resistance, which is a resistive force depending on many factors such as vehicle speed, tire/floor materials and tire inflation pressure. The study of this force over several conditions could lead to improvements in wheelchair design. The Anatomical Model Propulsion System (AMPS) is a robotic device to test manual wheelchairs with better repeatability than human subjects, helping to identify the effect of resistive forces. It uses electric motors to apply torque directly to the rear wheel handrims. In this thesis, a control system is developed to achieve a specified wheelchair trajectory and velocity profile, by controlling the input torque to the system. A kinetic and dynamic model is used to estimate this necessary input. Data collected from different experiments allows to determine rolling resistance under various conditions. The results show that rolling resistance also varies with acceleration, affecting the overall mechanical efficiency of a wheelchair following different velocity profiles.

Heavy vehicles require tires which can withstand extreme loads while maintaining control, delivering performance and minimizing fuel consumption, particularly on soft soils. Recent advances in finite element analysis and computational efficiency have opened doors to highperformance, highly complex simulations which were not possible just a few years ago. This research aims to model two tires using non-linear finite element analysis code and validate them using static and dynamic tests, including response to steering input. Soils are modeled using both traditionally-meshed FEA techniques as well as a newer mesh-less smoothed particle hydrodynamics method. Soils are validated and the accuracy of the SPH and FEA models are compared. The tires and soils are used together to estimate the rolling resistance of the tire over various terrains. The developed soil models are sufficient to model soils behaving like clay. The SPH soil models behave closer to actual soils, providing superior penetration and shear properties. This causes the SPH soil models to exhibit rolling resistance closer to experimental data.

The aim of this thesis is a construction concept of tyre rolling resistance measuring device. The first part deals with the rolling resistance. It describes its causes, its influential factors and it also includes rolling resistance identification methods. The second part deals with construction design of the rolling resistance measuring device itself. It contains stress analysis, and fatigue analyses as well. It includes selection of transducers used for tyre rolling resistance measuring and also measurement error analyses. The last part focuses on estimated financial requirements connected with producing and assembling the designed measuring device.

The objective of this thesis is to explore how human beings manipulate their dexterous operation skills to produce follow shot, stop shot, and draw shot while playing billiard. According to basic mechanics, the forces exerted on a billiard ball are analyzed in three different conditions. They include the cue stick hitting the cue ball, collision between the cue ball and the object ball, and the interaction between the ball and the surface. Mathematical models for those three fundamental techniques: the follow shot, the stop shot, and the draw shot, are developed by incorporating the rolling resistance. The friction between the surface and the ball, and the dent on the surface due to the mass of the ball are considered. Furthermore, reverse derivations are also implemented to solve initial hitting conditions between the cue stick and the cue ball for certain final states for the cue ball and the object ball. Computer simulations in virtual reality are conducted using the 3D Studio Max 8 software tool. Opinions from billiard experts are also collected for the purpose of verification. Based on simulation results, reversed derivation can accurately predict final states of the cue ball and the object ball for both stop shot and draw shot. However, for the case of follow shots, final position of the object ball cannot be fully determined. Besides, no unique solution exists for the hitting condition in all three types of shot.

The objective of this work is to develop a band saw tensioner from the drafting of the specifications to the testing of the prototype while finding the optimal solutions technologically and financially. This development covers the mechanical design and dimensioning of the entire machine. In this repport every step of the project are covered, the benchmark, the specifications, the design and dimensioning, and finally the financial study.

No description available.

Bedding angle is a fundamental property of a particulate system that describes the resistance to rolling motion of a single grain. Mean trends of the bedding angle of sand have been described in the literature. This research expands upon the work to date by investigating the distribution of bedding angle for sands. Experimental measurements of bedding angle distributions are made for eight sands. Additionally, a theoretical description of the variability of bedding angle as a function of random grain size is developed and implemented numerically. The shape of the bedding angle distribution is found to be simulated well from the numerical simulations; the mean value of bedding angle is best predicted from particle roundness and empirical relationships. Together, these procedures provide a means of predicting the complete distribution of bedding angle for any given sand.

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

När en lastbil färdas på väg utsätts den för ett antal krafter. Däckens rullmotstånd utgör ungefär 36 till 60 % av färdmotståndet. Att kunna validera rullmotståndet vid egen testning är värdefullt för en fordonstillverkare som Scania. Däcktillverkare tillhandahåller en konstant rullmotståndskoefficient men det är oklart om den går att använda i beräkningar för Scanias testsetup.Provningen går ut på att undersöka om testuppställningen möjliggör uppmätning av däckens rullmotstånd på chassidynamometer med momentnav. För den experimentella delen av examensarbetet har en kvantitativ datainsamlingsmetod använts för vidare maskinell analys och manuellt utföra statistisk undersökning. Testdriven utveckling (TDD) har tillämpats för att utifrån testresultaten kunna arbeta iterativt.Vid testningen går rullmotståndskoefficienten upp, ner eller ligger stabilt. Detta beror på att Kistler (Kistler momentnav består av två fälgar som innehåller universalsensorer för att kunna mäta vridmoment) har elektrisk drift som korrelerar till spridning av uppmätt rullmotståndskoefficient. Kistler momentnav är inte repeterbart på grund av drift. Det är möjligt att kompensera för den elektriska driften i Kistler momentnav och beräkna rullmotståndskoefficienten baserat på sista analyspunkten från körningarna.Mätvärden från Kistler momentnav har spridning. Genom att beräkna medelvärde för rullmotståndskoefficienten fås bättre noggrannhet. Medelvärde indikerar att rullmotståndskoefficienten har inget eller litet hastighetsberoende.Det går att använda Kistler momentnav och chassidynamometer 2 som testuppställning för att mäta upp av däckens rullmotståndkoefficient. Det är möjligt för Scania att fortsätta använda denna testuppställning för att bland annat undersöka fler däck. / When a long haul truck travels on a road it’s subjected to a number of forces. The tires rolling resistance is approximately 36 to 60% off the total travel resistance. Being able validate the rolling resistance during own testing is valuable to vehicle manufacturers like Scania. The tire manufacturers provide a constant rolling resistance coefficient but it’s unclear if it can be used in calculations for Scanias test setup.The purpose of the testing is to investigate if the test setup enables measuring the tires rolling resistance on a chassis dynamometer with torque wheels. For the experimental part of the degree project, a quantitative data collection methodology has been used for further machine analyzation and manually performing statistical analysis. Test driven development (TDD) has been applied to work iterative based on the test results.During testing the value of the rolling resistance coefficient went up, down or was stable. This is dependent on the electrical drift Kistler have (Kistler torque wheel consists of two rims that contain universal sensors to measure torque), that correlated with the distribution of the measured rolling resistance coefficient. It’s possible to compensate for the electrical drift in Kistler torque wheel and calculate the rolling resistance coefficient based on the last analyzation point from the tests.The measurements from Kistler torque wheel are distributed. By calculating the average of the rolling resistance coefficients a higher degree of accuracy is obtained. The average indicates that the rolling resistance coefficient have no or a small speed dependency.It’s possible to use Kistler torque wheel and chassis dynamometer 2 as a test setup to measure the rolling resistance of the tires. It’s possible for Scania to continue using this test setup to investigate more tires.