Analysis of the Phenomena Causing Weave and Wobble in Two-Wheelers

Francesco Passigato,Andreas Eisele,Dirk Wisselmann,Achim Gordner,Frank Diermeyer

doi:10.3390/app10196826

Francesco Passigato, Andreas Eisele + Show 3 more

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https://doi.org/10.3390/app10196826

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Abstract

The present work follows in the tracks of previous studies investigating the stability of motorcycles. Two principal oscillation modes of motorcycles are the well-known wobble and weave modes. The research in this field started about fifty years ago and showed how different motorcycle parameters influence the stability of the mentioned modes. However, there is sometimes a minor lack in the physical analysis of why a certain parameter influences the stability. The derived knowledge can be complemented by some mechanical momentum correlations. This work aims to ascertain, in depth, the physical phenomena that stand behind the influence of fork bending compliance on the wobble mode and behind the velocity dependence of the weave damping behaviour. After a summary of the relevant work in this field, this paper presents different rigid body simulation models with increasing complexity and discusses the related eigenvalue analysis and time behaviour. With these models, the mentioned modes are explained and the physical phenomena only partly covered by the literature are shown. Finally, the influence of the rider model on weave and wobble is presented.

Highlights

Motorcycle dynamics have always been an extensive research topic due to the complexity and the influence on the riders’ safety
With the parameter set used in the present work and in the speed range considered, the wobble mode remains well damped
The present work further analysed the physical phenomena behind the wobble and weave eigenmodes

Summary

Introduction

Motorcycle dynamics have always been an extensive research topic due to the complexity and the influence on the riders’ safety. The knowledge used to develop a stable motorcycle chassis comes, to a certain extent, from experience or sensitivity analysis which sometimes lack physical and theoretical understanding of the hidden phenomena. Two of the principal eigenmodes of a motorcycle are known as wobble and weave. The first one includes almost solely the rotation of the front assembly about the steering axis whose frequency is in the range between 7 and 10 Hz depending on the motorcycle’s parameters [1]; the second one is more complex, and when affected by this mode, the motorcycle shows roll, yaw, steering-head rotation and lateral displacement [2]. The earlier motorcycle models, such as the model of Sharp [3] which only includes a tyre model but no compliances, show a stable wobble mode in the lower speed range (up to 80 km h−1 ), and this mode becomes unstable in the higher speed range

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