Search results for "rolling resistance"
showing 10 items of 10 documents
Racecar Longitudinal Control in Unknown and Highly-Varying Driving Conditions
2020
This paper focuses on racecar longitudinal control with highly-varying driving conditions. The main factors affecting the dynamic behavior of a vehicle, including aerodynamic forces, wheel rolling resistance, traction force resulting from changing tire-road interaction as well as the occurrence of sudden wind gusts or the presence of persistent winds, are considered and assumed to have unknown models. By exploiting the theory on delayed input-state observers and using measurement data about the vehicle and wheel speeds, a dynamic filter that allows the online reconstruction of the above-mentioned unknown time-varying quantities is derived. Moreover, by exploiting the notion of effective tir…
Rolling resistance contribution to a road pavement life cycle carbon footprint analysis
2016
Purpose Although the impact of road pavement surface condition on rolling resistance has been included in the life cycle assessment (LCA) framework of several studies in the last years, there is still a high level of uncertainty concerning the methodological assumptions and the parameters that can affect the results. In order to adopt pavement carbon footprint/LCA as a decision-making tool, it is necessary to explore the impact of the chosen methods and assumptions on the LCA results. Methods This paper provides a review of the main models describing the impact of the pavement surface properties on vehicle fuel consumption and analyses the influence of the methodological assumptions related…
Study on Improving the Functional Performance of Linear Motion Systems
2015
In the construction of high performance mechanical transmission with high precision in movement and positioning are used ball screws with preloaded double nuts. Among the factors that influence the performance of these transmissions are friction idle torque and friction load torque. Because, theoretically, the friction idle torque is influenced only by the preload force that loading, the double nut of the ball screw, was experimentally determined dependence of that torque of screw speed. Given the set was determined and exposed in the present work, the relation of dependency, idle friction torque, preload force and screw speed. From the relationship thus obtained can determine the instantan…
Analysis of rolling friction effects on oblique rebound by redefining tangential restitution and friction
2019
The planar oblique impact of a homogeneous sphere on an infinitely massive rough plane is described assuming that normal and tangential restitution mechanisms operate independently of friction, and that frictional effects include not only the usual Coulomb model but also rolling friction effects. This formulation extends early models including rolling friction effects in the description of impact events to include the independent friction restitution closure. The model yields velocity-independent equations for postimpact linear and angular velocities in four impact regimes, namely, sliding plus rolling, sliding nonrolling, stick plus rolling, and stick nonrolling whose predictions are compa…
Independent friction-restitution modeling of two-disk collisions
2021
[EN] The oblique collisions between two axisymmetric disks moving on a flat horizontal surface are described in terms of impact modeling based on the assumption that normal and tangential restitution mechanisms operate independently of friction. Describing these mechanisms in terms of the usual Coulomb formulation, the model allows for an interpretation of some ¿anomalous¿ experimental data reported in the literature. These experimental data, corresponding to the variation of the coefficients of friction and tangential restitution with the impact angle, remained unexplained in classic formulations, are understood within the framework of the independent friction-restitution closure. Experime…
Vehicular Motion and Traffic Breakdown: Evaluation of Energy Balance
2009
Microscopic traffic models based on follow–the–leader behaviour are strongly asymmetrically interacting many–particle systems. The well–known Bando’s optimal velocity model includes the fact that (firstly) the driver is always looking forward interacting with the lead vehicle and (secondly) the car travels on the road always with friction. Due to these realistic assumptions the moving car needs petrol for the engine to compensate dissipation by rolling friction. We investigate the flux of mechanical energy to evaluate the energy balance out of the given nonlinear dynamical system of vehicular particles. In order to understand the traffic breakdown as transition from free flow to congested t…
Analysis of oblique rebound using a redefinition of the coefficient of tangential restitution coefficient
2013
Abstract A redefinition of the coefficient of tangential restitution based on the separation of friction and restitution effects is presented. Using this modified coefficient of tangential restitution and the usual definitions of the coefficients of normal restitution and sliding friction, a description of oblique impacts in both stick and slip regimes is obtained. This, description, which is tested with available rebound data in literature, avoids sharp (apparent) variations in the coefficient tangential restitution with impact angle and can justify anomalous results reported by Calsamiglia et al. (1999) .
Rolling resistance and traffic delay impact on a road pavement life cycle carbon footprint analysis
2017
The application of Life Cycle Assessment (LCA) to road pavements has been continuously evolving and improving over the last years, however there are several limitations and uncertainties in the introduction of some components in the framework, such as road pavement rolling resistance—in terms of pavement surface properties—and traffic delay during maintenance activities. This paper analyses the influence of methodological assumptions and the model used to estimate the increased emissions for traffic delay and road pavement rolling resistance on the results of an LCA. The Greenhouse Gases (GHG) emissions related to these two phases of a pavement LCA will be calculated for a UK case study, us…
The influence of mechanical damaging on the lifetime of positrons In ultrahigh-molecular polyethylene
2013
We study the influence of damaging of ultrahigh-molecular polyethylene [(PE-UHMW) Chirulen®1120] applied, among other materials, in the production of hip endoprostheses on the spectra of positrons lifetime in this material. Polyethylene samples were damaged by the impacts, rolling friction, and collisions with metal balls in a planetary mill. The changes in the parameters of the spectra of positrons lifetime related to the annihilation of orthopositronium (o-Ps) were analyzed depending on the mechanical energy transferred to the sample. On the basis of the Eldrup–Tao model, the changes in the radii of voids in which positroniums are formed and annihilated and the changes in the degree of fi…
Previsione delle prestazioni del veicolo su strada: stato dell’arte
2016
Questo lavoro contiene una rassegna dei metodi che sono usati per la previsione delle prestazioni del veicolo su strada, in dipendenza del motore installato. La prima parte mostra il calcolo delle resistenze al moto, cioè le forze che il veicolo deve vincere per avanzare sulle strade piane e in salita. Particolarmente interessante appare la parte che riguarda la resistenza aerodinamica, della quale si tratta di metodi sperimentali (galleria del vento), metodi empirici e metodi CFD. Si propone inoltre l’applicazione della norma CUNA sulla velocità per la determinazione dei consumi anche al calcolo dei coefficienti aerodinamici. La rassegna esclude la resistenza accidentale in curva perché no…