Carlo Miano

Extensions of the LuGre tyre friction model related to variable slip speed along the contact patch length

The recently developed LuGre model describes the three-dimensional tyre friction dynamics given in the brush representation. The model has a three-state lumped-parameter form and an analytical solution for tyre static curves. It is simplified using the assumption of a constant slip speed along the contact patch length. This assumption is abandoned in this paper in order to extend the model with several secondary but potentially important effects such as camber, carcass compliance, conicity, ply steer and rolling resistance. Two approaches to the introduction of a variable-slip-speed effect are considered. The first is based on stepwise approximation of the slip speed along the contact patch length, and the second includes a specific, spatially distributed additive deflection term. Both approaches preserve the three-state lumped-parameter model form and an analytical steady-state solution. Qualitative and quantitative validation results point to consistency and benefits of the proposed model extensions.

Experimental identification of dynamic tire friction potential on ice surfaces

Recently, it has been shown that the tire–ice friction is characterized by a significant dynamic potential for abrupt increases of wheel torque. With the aim to gain insight into the dynamic tire friction potential features and to provide a comprehensive set of experimental data for model validation, a detailed experimental investigation of the dynamic potential has been presented in this article. The experimental data have been collected by using an experimental electrical vehicle with an in-wheel motor. Influence of the following operating parameters has been analyzed: rate of change of applied wheel torque, time for which the tire stands still on ice before applying the abrupt transient, initial vehicle speed, and initial tire force. In order to check a possible correlation between the dynamic potential and the rubber–ice friction dynamics, an experimental analysis based on a pin-on-disc tribometer has also been presented.

Experimental analysis and modelling of longitudinal tyre friction dynamics for abrupt transients

A test vehicle has been used to collect experimental data related to abrupt engine throttle tip-in transients. The data point to a significant dynamic potential of the longitudinal tyre frictional force on an ice surface. Such a behaviour cannot be predicted by using the available brush-type dynamic tyre friction models. Based on the results of experimental and simulation analyses, the LuGre tyre friction model is extended to predict the dynamic friction potential. The extended model is validated against the experimental data.

An in-wheel motor-based tyre test vehicle

An experimental three-wheel electrical vehicle has been developed in order to provide a platform for experimental verifications of advanced tyre friction models, estimators and controllers. The vehicle comprises a high-torque permanent-magnet synchronous motor built in the front wheel and precise incremental encoders for the front- and rear-wheel speed measurements. The paper presents a description of the vehicle and gives characteristic experimental procedures and results related to motor static and dynamic behaviour. Experimental results on tyre friction identification are also presented.