The stability of motorcycles under acceleration and braking

A comprehensive study of the effects of acceleration and braking on motorcy cle stability is presented. This work is based on a modified version of a d ynamic model presented earlier, and is thought to be the most comprehensive motorcycle dynamic model in the public domain. Extensive use is made of bo th non-linear and linearized models. The models are written in LISP and mak e use of the multibody modelling package AUTOSIM. There is novelty in the w ay in which control systems have been used to control the motorcycle drive and braking systems in order that the machine maintains desired rates of ac celeration and deceleration. The results show that the wobble mode of a motorcycle is significantly dest abilized when the machine is descending an incline or braking on a level su rface. Conversely, the damping of the wobble mode is substantially increase d when the machine is ascending an incline at constant speed, or accelerati ng on a level surface. This probably accounts for the pleasingly stable 'fe el' of the machine under firm acceleration. Except at very low speeds, inclines, acceleration and deceleration appear t o have little effect on the damping or frequency of the weave mode. Non-lin ear simulations have quantified the known difficulties to do with rear tyre adhesion in heavy braking situations that are dominated by rear wheel brak ing.