1,720,986 research outputs found
Multiphysical MF-based tyre modelling and parametrisation for vehicle setup and control strategies optimisation
No full textStarting from the earliest phases of design of the vehicle and its control systems, the understanding of tyres is of fundamental importance to govern the overall vehicle dynamics. A properly characterised tyre–road interaction model is essential to achieve a reliable vehicle dynamics model on which more design variations can be studied directly in simulation environment optimising both cost and time. The possibility to count on computationally efficient and reliable formulations represents nowadays a great advantage, and the multiphysical Pacejka's Magic Formula (MF-evo) tyre model presented is one of the best trade-off solutions to meet the strict real-time requirements and to reproduce multiphysical variations of the tyre dynamic behaviour towards temperature, pressure and wear effects. A specific methodology has been developed to characterise and to identify the MF-evo parameters with a high grade of accuracy and reliability directly from experimental data. The proposed technique is based on a pre-processing procedure to remove non-physical outliers and to cluster the data, which allows to optimise the multidimensional parameterisation process. To the purpose of validation of the parametrisation routine, data from a motorsport case, exceptionally difficult to reproduce in simulation due particularly significant variations of the tyre dynamics during a single test, have been employed demonstrating the MF-evo model potential and robustness
Tyre wear model: A fusion of rubber viscoelasticity, road roughness, and thermodynamic state
No full textWear is due to many causes and involves three major consequences: loss of performance, loss of security and environmental pollution. Depending on the context, the focus on the consequence can be moved: in motorsport tyre's fundamental role is to guarantee high performance as long as it is possible, in road vehicles safety has decisive importance compared to the safety target, in big densely-populated cities the pollution due to tyre particles can be of considerable importance. The main objective of this work is to describe a necessary set of instruments concerning tyre wear mechanism-related phenomena, allowing to better understand and to develop an improved formulation, able to consider the tread compound viscoelastic characteristics, the pavement roughness and the tyre operating conditions. To this purpose the modelling approach considers the viscoelastic behaviour of the compound, changing instant by instant its nominal characteristics as a function of the excitation frequency and the material temperature. To validate the modelling approach proposed and its reliability in completely different scenarios of use, the authors have selected five datasets collected on vehicles belonging to diverse motorsport, passenger and truck categories, unique in terms of vehicle operating conditions both from kinematic-dynamic and thermodynamic points of view
Tire multiphysical modeling for the analysis of thermal and wear sensitivity on vehicle objective dynamics and racing performances
No full textThe handling behavior of a vehicle is one of its most important properties because of its relation to performance and safety and to its deep link with concepts such as “over-steer” or “under-steer”. Tire–road interaction models play a fundamental role in the vehicle system modeling, since tires are responsible for the generation of forces arising within contact patches, fundamental for both handling and ride/comfort. Among the models used to reproduce such forces, Pacejka's Magic Formula (MF) is undoubtedly one of the most used ones in real-time automotive simulation environments because of its ability to fit quite easily a large amount of experimental data, but its original formulation did not take into account of the tire thermodynamics and wear conditions, which clearly affect tire and vehicle dynamics and are not negligible, especially for high level applications, such as motorsport competitions. Exploiting a multiphysical tire model, which consists in an evolved version of the standard MF model (MF-evo), and a vehicle model properly validated throughout experimental data acquired in outdoor testing sessions carried out with an industrial partner, the current work presents a study on vehicle behavior variation induced by thermodynamic and wear parameters, defining a series of metrics to analyze and show results. One of the elements of interest on which the focus is placed is the possibility to highlight how under-over-steering behavior of a car changes according to different thermodynamic states of tires; to do this, a commercial software VI CarRealTime has been used to perform a series of objective steady-state maneuvers and long runs, exploiting the logic of a lap time optimizer
Correction to: Cross-combined UKF for vehicle sideslip angle estimation with a modified Dugoff tire model: design and experimental results (Meccanica, (2021), 56, 11, (2653-2668), 10.1007/s11012-021-01403-6)
No full textThe original article has been updated. Several corrections were overlooked during the correction process; these have now been corrected
Application of Generalized Models for Identification of Viscoelastic Behavior
No full textIn this paper the capability to reproduce the mechanical behaviour of viscoelastic materials is investigated comparing the response of a generalized Maxwell model and a relative fraction derivative model towards the experimental behavior of a selected viscoelastic material. In particular, the rheological models are mathematically described illustrating the advantages of the pole-zero formulation for a constrained parameters’ identification procedure. The effectiveness of the both models’ is then compared focusing on the ability of the models to adequately fit the experimental data with a minimum number of parameters, also addressing the possible computational issues
On the Vehicle Stability and Maneuverability Domain Definition for Automated Vehicles
No full textVehicle safety is of a fundamental importance in the automotive industry and, with an increasing level of automation, the impact of vehicles on the global environment has to be investigated from a totality of different perspectives starting from pollution impact objectives up to the vehicle risk-prevention capabilities. For this reason, the state estimation techniques and the advanced control logics have being developed in recent years with the aim of improving the safety of the semi-automated vehicles, able to assist the driver in emergency situations minimizing the connected risks. Furthermore, the vehicle stability topic has acquired more interest since it could allow to pre-determine the vehicle stability and maneuverability regions, optimizing both the real-time computational efficiency of the control-related logics and the correct identification of the optimum vehicle operating boundaries in completely different use scenarios. Since a vehicle is a strongly nonlinear system mainly because of tyres behaviour, the methodology able to adequately determine the stability region becomes crucial. Starting from a specific literature survey, this work aims to investigate control-oriented approaches, employing the local stability criteria method, able to determine stability regions within the system phase-plane potentially adoptable in a computationally-efficient vehicle onboard logic. The techniques presented and the sensitivity analyses conducted highlight which should be the research directions in this field to remove several not-negligible but yet present assumptions in the literature
Ultraviolet Light Radiation Effects on Viscoelastic Property Variation in Polymers
No full textViscoelastic materials exhibit a variable mechanical behavior generally investigated through Dynamic Mechanical Analysis (DMA). Such kind of test is carried out on standardized specimens, which have to be specifically produced or extracted from the component to be characterized, causing its destruction. This work, taking advantage of an innovative non-invasive testing procedure, based on an instrumented evaluation of indentation, aims to experimentally study the viscoelastic properties changes in polymer compounds, caused by exposure to UV rays. The analysis has been executed on two different polymer compounds designed for tire tread. An extensive use of UV radiation is performed to generate changes in rubber compound properties, but as concerns tire compounds application, there are only a few studies in literature and the same can be stated regarding the monitoring of properties over time using non-destructive procedures. In order to evaluate the viscoelastic properties variation, a proper test bench has been developed employing an UV lamp coupled with an innovative testing device. A test campaign has been carried out on the different tire compound specimens, tested in different conditions in terms of exposure time, exposure face and after various time ranges from the exposition. The tested compound samples exhibit a different chemical composition in terms of polymer blend ratio. The overall results highlight: the ability of the proposed technique to measure the variation in the mechanical behavior of the materials induced by exposure to UV rays and significant variations in viscoelastic properties induced on the compounds as a function of the time of exposure to UV rays and of the chemical composition
Extension of the multiphysical magic formula tire model for ride comfort applications
No full textIn the development of physical tire models, the complexity of the composite structure and the multiphysical variables require strongly nonlinear mathematical formulations to guarantee a desired degree of accuracy. The aim of the current work is to extend the applicability of the multiphysical magic formula-based tire model, already developed and presented by the authors, within a wider frequency range, interposing a rigid ring body between the contact patch and the wheel hub. The contact patch, varying in terms of size, shape, and relative position, is evaluated using instantaneous cams to define the effective plane. Here the advanced slip model, taking into account thermodynamic and wear effects, is then integrated. The adopted formulations have been mathematically and physically justified. They have been analytically compared to formulations related to the rigid-ring implementation available in the literature. Specific experimental activities concerning both the tire’s vertical kinematics and dynamics have been conducted to demonstrate the model’s improved physical consistency on small wavelength unevennesses
Necessity of the Tire Temperature-Dependant Parameters in Vehicle Virtual Sensing
No full textVehicle state estimation plays a crucial role in the design and development of advanced systems for vehicle control and autonomous driving applications. In this context, the knowledge of vehicle side slip angle is required to optimize lateral dynamics control, improving the overall handling performance. On one hand, the direct measurement of lateral velocity can only be provided by employing sophisticated and expensive onboard sensors. On the other hand, the vehicle system and, in particular, the tires can significantly modify their behaviour through time due to temperature, pressure and wear influences, thus modifying both the vehicle handling behaviour and the parameters of the installable control logic. For this reason, the authors propose an innovative estimation method, combining the vehicle mathematical implementation with a double-track model enriched with virtual observations obtained through a kinematic observer. To validate its applicability in contexts covering a wide range of tire thermodynamic conditions, the proposed estimation approach has been integrated with a multiphysical tire formulation, proposed by the authors in the previous studies, able to take into account of temperature and pressure effect on the tire dynamic response. The results have been analysed in terms of the vehicle sideslip angle acquired in a dedicated experimental campaign comparing the accuracy of the proposed approach to the commonly adopted one, not accounting for temperature and pressure influences
An Enhanced Greenwood-Williamson Contact Model for the Evaluation of Local Tire/Road Contact Area
No full textContact modeling plays a crucial role in tire road interaction, impacting several fields, including vehicle dynamics, road safety, and transportation efficiency. As the tire is in contact with the road, the real contact area is smaller than the nominal area due to the indentation of the rubber over the road profile, influenced by the distribution of road texture. This paper introduces a novel approach to contact modeling, focusing on the evaluation of the ratio between the real contact area and the nominal one (AcA0), considering the Greenwood-Williamson formulation. This ratio is fundamental for characterizing the tire-road contact behavior, as it depends on tire viscoelastic properties, road roughness characterization and tire operating conditions. The paper presents some simulations conducted in MATLAB to assess the AcA0 ratio for various road specimens. These simulations were conducted considering a specific compound, while varying parameters such as contact pressure and compound temperature, with a fixed sliding velocity. This research, thus, enhances the understanding of how the road texture, combined with the tire properties and operating conditions, affects tire indentation over the road profile which is strictly related to the perceived friction values
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