Nonlinear steering oscillations of motorcycles

Extensive prior modelling of the three dimensional motions of motorcycles, which has depended heavily on linearization for small perturbations from equilibrium "trim" states, is extended to cover large amplitude, nonlinear operating regimes. For a cornering machine, road undulation displacement forcing is shown to be capable of exciting subharmonic and superharmonic responses. A procedure for identifying particular operating conditions that may be expected to yield internal or combination resonances for a baseline modern machine/rider combination is devised. Interesting cases are examined by simulation and the results analysed using short time Fourier transform processing of the output signals. Internal and combination resonances are shown to occur under specially chosen circumstances. A procedure for choosing these special circumstances is described. Some practical implications are also considered.