1,721,013 research outputs found
T.R.I.C.K.-Tire/Road Interaction Characterization & Knowledge - A tool for the evaluation of tire and vehicle performances in outdoor test sessions
No full textThe most powerful engine, the most sophisticated aerodynamic devices or the most complex control systems will not improve vehicle performances if the forces exchanged with the road are not optimized by proper employment and knowledge of tyres. The vehicle interface with the ground is constituted by the sum of small surfaces, wide about as one of our palms, in which tyre/road interaction forces are exchanged. From this it is clear to see how the optimization of tyre behaviour represents a key-factor in the definition of the best setup of the whole vehicle.
Nowadays, people and companies playing a role in automotive sector are looking for the optimal solution to model and understand tyre's behaviour both in experimental and simulation environments. The studies carried out and the tool developed herein demonstrate a new approach in tyre characterization and in vehicle simulation procedures. This enables the reproduction of the dynamic response of a tyre through the use of specific track sessions, carried out with the aim to employ the vehicle as a moving lab.
The final product, named TRICK tool (Tyre/Road Interaction Characterization & Knowledge), comprises of a vehicle model which processes experimental signals acquired from vehicle CAN bus and from sideslip angle estimation additional instrumentation. The output of the tool is several extra "virtual telemetry" channels, based on the time history of the acquired signals and containing force and slip estimations, useful to provide tyre interaction characteristics. TRICK results can be integrated with the physical models developed by the Vehicle Dynamics UniNa research group, providing a multitude of working solutions and constituting an ideal instrument for the prediction and the simulation of the real tyre dynamics
A Test Rig for Tyre Envelope Model Characterization
No full textThis paper deals with tyre enveloping behaviour on uneven road surface. To build realistic and reliable vehicle dynamics models it is of fundamental importance to study the influence of road obstacles and irregularities on forces and displacements involving a rolling tyre. After a brief review about early studies concerning this phenomenon, the tandem model with elliptical cams is introduced and described, highlighting its hypothesis and the parameters on which it is based, the most important of which are the cams profiles and the distance between them. The main aim of this paper is the executive project of a test rig aimed to carry out an experimental campaign for the identification of the parameters of the tandem cam model and for its validation.
The idea is to experimentally acquire the path of the patch centre of a tyre rolling over an obstacle, to define the parameters of the curves employed for the cam profiles and the distance between them in the tandem model. It is important to highlight that these parameters are strictly connected to tyre properties and need tests to be investigated and identified.
The design started from a test bench for motorcycles already available at DII’s Tyre Lab, introducing proper changes without compromising original test bench destination
A Flexible Ring Tyre Model for Normal Interaction
No full textA physical – numerical tyre model has been developed. The whole model allows to obtain the tyre – road interactions which can be used in vehicle dynamics simulations. In this paper its capabilities in terms of normal interaction analysis are presented. The tyre normal interaction, i.e. the relationship between the normal load and the normal deflection, influences the tangential (longitudinal plus lateral) one, which determines the vehicle’s handling behaviour. The parameters used in the model depend on the structure of the tyre and they can be measured on the real tyre. The tyre has been schematized as composed by a flexible belt, by the sidewalls and by a rigid ring (rim). The flexible belt is composed by a number of lumped masses linked by extensional and bending stiffnesses and dampers. The tyre model has been developed using the finite segment method. Using this method it is possible to include in the tyre simulations various non-linear structural effects due to large displacements and rotations. The model allows to simulate both steady state and transient conditions
Physical Modelling of Tire Wear for the Analysis of the Influence of Thermal and Frictional Effects on Vehicle Performance
No full textThe tire and vehicle setup definition, able to optimise grip performance and thermal working conditions, can make the real difference as for motorsport racing teams, used to deal with relevant wear and degradation phenomena, as for tire makers, requesting for design solutions aimed to obtain enduring and stable tread characteristics, as finally for the development of safety systems, conceived in order to maximise road friction, both for worn and unworn tires. The activity discussed in the paper deals with the analysis of the effects that tire wear induces in vehicle performance, in particular as concerns the consequences that tread removal has on thermal and frictional tire behaviour. The physical modelling of complex tire–road interaction phenomena and the employment of specific simulation tools developed by the Vehicle Dynamics UniNa research group allow to predict the tire temperature local distribution by means of TRT model and the adhesive and hysteretic components of friction, thanks to GrETA model. The cooperation between the cited instruments enables the user to study the modifications that a reduced tread thickness, and consequently a decreased SEL (Strain Energy Loss) and dissipative tread volume, cause on the overall vehicle dynamic performance
Virtual Testing of Advanced Driving Assistance Systems
No full textThis paper presents some results on the development and testing of new solutions in the field of driving automation. The introduction of increasing levels of vehicle automation aimed at enhancing road safety requires a renewed approach to the research and development process and needs a multi-actor environment where the innovation can be tested. Indeed, vehicle automation spans several scientific disciplines and it is becoming exceedingly difficult and too costly for a single research innovation team to go in depth into all technologies and solutions. This is shifting the innovation process toward a multidisciplinary approach in which the only way to ensure an easy, rapid, efficient and scalable introduction of the required innovation is to adopt integrated and complex testing platforms for the simulation of automation solutions, based on a modular architecture, where independent components can be developed and then integrated and tested in a multi-actor environment. A platform for virtual testing is presented herein and employed to assess the performance of an integrated driving assistance solution based on computing appropriate surrogate measures of safety that allow for the transition between different automation logics in free-flow, car-following and emergency braking conditions
A three-dimensional multibody tire model for research comfort and handling analysis as a structural framework for a multi-physical integrated system
No full textA tire is an extremely integrated and multi-physical system. From only a mechanical point of view, tires are represented by highly composite multi-layered structures, consisting of a multitude of different materials, synthesized in peculiar rubber matrices, to optimize both the performance and the life cycle. During the tire motion, due to the multi-material thermodynamic interaction within the viscoelastic tire rubber matrix, the dynamic characteristics of a tire may alter considerably. In the following paper, the multibody research comfort and handling tire model is presented. The main purpose of the research comfort and handling tire is to constitute a completely physical carcass infrastructure to correctly transmit the generalized forces and torques from the wheel spindle to the contact patch. The physical model structure is represented by a three-dimensional array of interconnected nodes by means of tension and rotational stiffness and damper elements, attached to the rim modeled as a rigid body. Research comfort and handling tire model purpose is to constitute a structural physical infrastructure for the co-implementation of additional physical modules taking into account the modification of the tire structural properties with temperature, tread viscoelastic compound characteristics, and wear degradation. At the stage, the research comfort and handling tire discrete model has been validated through both static and dynamic shaker test procedures. Static test procedure adopts contact sensitive films for the contact patch estimation at different load and internal pressure conditions, meanwhile the specifically developed sel test regards the tire dynamic characterization purpose at the current stage. The validation of the tire normal interaction in both static and dynamic conditions provided constitutes a necessary development step to the integration of the tangential brush interaction model for studying the handling dynamics and to the analysis of the model response on the uneven surfaces
Theoretical and Experimental Estimation of the Hysteretic Component of Friction for a Visco-Elastic Material Sliding on a Rigid Rough Surface
No full textAccording to the most recent approaches, the friction coefficient arising between tyre rubber and road can be seen as constituted by three components: adhesion, deforming hysteresis and wear. This paper deals with the estimation of the hysteretic component of friction. This component is due to indentation phenomena regarding contact mechanics of deformable bodies sliding on the asperities of a rough substrate, which exert oscillating forces at the interface, leading to cyclic deformations of the rubber and then to energy "dissipation" via its internal damping. To evaluate this component, a physical model able to calculate energy dissipation of a rubber block indented by a rigid asperity in sliding contact has been built. To this aim the viscoelastic characteristics of the material have been taken into account. The road profile has been modelled as the sum of two sinusoidal waves characterizing the macro and the micro roughness scales. The results coming out from the physical model have been validated by means both of FEM models results and of experimental tests carried on a pin on disk tribometer
A Full Scale Test Rig to Characterize Pneumatic Tyre Mechanical Behaviour
No full textIn this paper an experimental test rig aimed to characterize mechanical properties of a pneumatic tyre, together with some results, is presented. The objective is to determine tyre mechanical characteristics useful to physically model its behaviour; in particular: the normal interaction characteristic, the radial stiffness, the total stiffness and the longitudinal hysteretic cycles. To this aim two different kind of tests have been executed: radial and longitudinal. In the radial test the load is statically applied to the tyre, along the vertical direction, by means of an hydraulic press and it is measured together with the consequent radial deformation, so allowing the estimation of the tyre normal interaction characteristic and of its radial stiffness. Different radial tests can be conducted for an assigned tyre varying the inflation pressure. The longitudinal tests are conducted applying, under an assigned constant vertical load, a variable horizontal strain to the tyre by means of a linear actuator, two profile rail guides and a system to transfer the horizontal motion to the contact patch of the tyre, opportunely placed on a moving steel plate placed on the two linear guide rails. During the tests the horizontal load and the resulting deformations are measured and acquired so allowing the estimation of tyre total stiffness and of its longitudinal hysteretic cycles. Longitudinal tests can be conducted varying the assigned vertical load, the horizontal displacement law in terms of frequency and amplitude, the tyre inflation pressure. All the different types of rim can be mounted on the test rig thanks to a universal quick flange
Preliminary Studies on Criticalities and Opportunities for Virtual Testing of Driving Automation
No full textThis paper presents some preliminary analyses on the development of new tools for the transport industry, able to deal with the introduction of increasing levels of vehicle automation. Driving assistance is aimed at increasing road safety, but it needs a renewed approach to the research and development process. Indeed, vehicle automation spans several scientific disciplines and it’s becoming exceedingly difficult and too costly for a single research innovation team to “go deep” across all technologies and solutions. The only way to ensure an easy, fast, efficient, and scalable introduction of the required innovation is to adopt integrated and complex testing platform for the simulation of automation solutions. To this aim virtual-testing platforms should be conceived to allow different actors to work on different components, possibly at different levels of detail, any of the actors being allowed to sophisticate with a particular simulation issue (e.g. the driver behaviour in presence of Advanced Driving Assistance Systems) knowing that the other components (e.g. the vehicle dynamics) have been (or will be) simulated at the required sophistication level, possibly by another actor of the innovation process. In this paper the authors wishes to contribute to the development of these newgeneration tools. Analyses will be carried out in order to identify the key opportunities and criticalities in the development of virtual testing platform for testing driving automation. From these analyses research perspectives will be identified and proposed for future developments
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