Straight running stability without controlling behavior of the rider is analyzed with regard to a mathematical model of 12 degrees of freedom. This model has 2 degrees of freedom concerning leaning movement of upper body and lateral movement of lower body of the rider as well as 4 degrees of freedom of sideslip, yawing, rolling of motorcycle, and rotation of steering handlebar, and 6 degrees of freedom of frame rigidities.Vibration characteristics of the rider's body influence both weave and wobble modes.
Abstract