Two Approaches for the Synthesis of a Weave-Wobble-stabilizing Controller in Motorcycles

Weave and wobble are well-known eigenmodes of motorcycles. Depending on the motorcycle parameters, these modes may become unstable, thus impairing safety and maneuverability. Steering dampers are fitted in modern motorcycles to improve the wobble stability and prevent the kick-back phenomenon. However, they have a detrimental effect on the weave stability, so that the damping coefficient is a trade-off between wobble and weave stability. Even though a similar problem concerning the vertical dynamics of passenger cars is well documented, there are not so many applications which try to optimize this trade-off for motorcycles. In the present work, two control strategies for a steering controller are presented, which help to optimize the trade-off. The first one is a proportional controller, where the controller parameters are optimized for several speeds. The second one is based on H∞ controller synthesis coupled with a model identification process. Both controllers are able to increase the stability range of a specific motorcycle model. In particular, the high speed weave stability issue is solved. The H∞ controller performs better than the proportional controller and, even though it is synthesized for a single speed, it demonstrates the desired behavior over a wide speed range.