Influences of a vibration absorber on the lateral stability of a motorcycle

A lightly damped or even unstable weave or wobble mode of a motorcycle can induce self-excited oscillations, which may lead to the loss of the rider's confidence or even to dangerous driving situations. Since design measures that stabilise one of these modes commonly destabilise the other, achieving simultaneous improvement of both modes remains a challenging problem. This paper investigates the use of passive dynamic vibration absorbers (DVAs) to improve motorcycle lateral stability. A Whipple-based motorcycle model, extended to include lumped frame compliance and transient tyre behaviour, is employed to analyse three absorber configurations: a rotational DVA mounted on the front frame, a rotational as well as a transversal DVA mounted on the main frame. The results show reasonable stabilisation potential. A front-frame rotational DVA effectively increases wobble stability, whereas a transversal DVA on the main frame provides the most significant improvement in critical weave speed when appropriately positioned. Road tests using a transversal DVA mounted at the top-case position qualitatively confirm the analytical findings.