Modeling Nonlinear Motorcycle Dynamical Behavior during severe Acceleration and Braking

The purpose of this work is to study the vibrational behavior, such as wheel bounce or chatter and rear suspension pitch, observed in racing motorcycles during severe acceleration and braking conditions. These vibrations may affect the performances and the safety of the vehicle. A multibody model of the system was implemented using a Newton-Euler approach and an associated linearized model was obtained in symbolic form. Accurate tire modeling was considered, and tire torsional stiffness effects were taken into account, since they may play an important role in transient dynamical vehicle behavior. Several numerical simulations were accomplished with different levels of longitudinal acceleration levels and different values of the tire force characteristic parameters. It was observed that unwanted vibrations may occur, being caused by a loss of stability of the system, and that this phenomenon may exhibit selfexcited behavior. A sensitivity analysis was performed on the associated linearized model in order to identify the possible causes of the vehicle instability in severe acceleration and braking conditions.