Abstract
The stability of two-wheeled vehicles is predominantly characterized by the well-known weave and wobble vibration modes, which have been extensively investigated in the literature, mainly in terms of their frequencies and damping ratios. In this work the focus is towards their mode shapes, which are investigated using the screw-axis (also called Mozzi-axis), instead of the classic compass diagrams, for a better understanding of their three-dimensional patterns. The analysis is then carried out using the velocity centres for a characterization from the top, rear and side view of the vehicle. The multibody vehicle model employed for the numerical analysis is built in Adams. The dataset resembles that of a 250cc sport motorcycle, and has been derived from laboratory tests. The stability analysis is carried out in the frequency domain. It is found that, depending on the selected plane for the projection of the three-dimensional vibration motion, the trajectories of the velocity centres of the weave and wobble can cross either aft or fore the centre of mass, which has been associated to the under- and over-steering behaviour in the literature.
Highlights
The lateral stability of two-wheeled vehicles has been investigated extensively in the last 50 years, both numerically and experimentally
Weave is characterized by steering oscillations combined with yaw, roll and lateral motion of the vehicle, with frequencies usually below 4–5 Hz, while wobble is dominated by steering oscillation, with frequency usually in the range 6–10 Hz
The mode shape of the most important lateral vibration modes of two-wheeled vehicles, namely weave and wobble, are analysed through a screw axis approach, which is an extension of the velocity centre approach recently proposed in the literature
Summary
The lateral stability of two-wheeled vehicles has been investigated extensively in the last 50 years, both numerically and experimentally. Most of the analyses mentioned above focus on the effect that the main vehicle, tyre and rider parameters have on the frequency and damping of the vibration modes. Such modes are usually presented in terms of the real and imaginary part of the eigenvalues—. Velocity centres have been used to investigate the mode shape of the weave mode [24] In this work, such analysis is generalized through the screw-axis and extended to include the front view and wobble.
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