Driveline instability of racing motorcycles in straight braking manoeuvre

Abstract

Experimental evidence shows that a self-excited vibration may appear during braking manoeuvres performed by road-racing motorcycles. It involves vertical oscillation of front and rear wheel axles as well as angular oscillation of the driveline in a frequency range between 17 and 22 Hz. As a consequence, severe oscillations of the tyre-ground vertical loads can be observed, leading to a loss of grip and ultimately weakening the vehicle overall performance. Several contributions on this topic can be accounted for in the literature; however, a comprehensive description of the phenomenon has not been given yet. The present work is aimed at simulating the above vibration with a planar multibody motorcycle model, and then at analyzing its driving mechanism. Stability maps are drawn for time-invariant braking manoeuvres, and validated with respect to time domain simulations

Patter instability of racing motorcycles in straight braking manoeuvre

“…A full list of parameters describing the proposed model is reported in the Appendix. It presents two differences with respect to the model studied in [1]: first, the centre of rotation of the upper forks P can be positioned out of the fork line, for simulating also modes involving pitching of the motorcycle's main frame; second, the wheel assembly is considered as a single body, since in [1] the torsional compliance of the tyre was recognized to play a negligible role in the development of instability, which was confirmed by simulations performed with the multibody model herein adopted, considering rigid-ring tyres [5].…”

“…Stability maps are drawn on the basis of sets of parameter values related to a straight running braking manoeuvre performed by a road racing motorcycle. Results are compared with those found in the literature [1,3,5] and with those obtained by a multibody planar motorcycle model, in this case also considering transient braking manoeuvres. The source of the self-excited vibration is investigated by means of phase-diagrams of the unstable mode at the stability threshold, aimed at explaining its driving mechanism and at identifying which parameters play a major role in the actual vibration onset.…”

“…First, a modified minimal model of the front assembly is proposed, with centre of rotation of the upper forks positioned out of the fork line, for simulating also modes involving pitching of the motorcycle's main frame (not considered in [1]); its equations of motion are derived in non-linear form and then linearized with respect to equilibrium-states, by imposing stationary values of forward speed during braking; the proposed model is then studied in terms of modal analysis and stability maps. Second, the results are compared to numerical simulations obtained from a full motorcycle multibody model [4], reduced to planar as described in [5], in this case also considering transient braking manoeuvres. This analysis is restricted to planar motion, considering running straight ahead braking manoeuvres not including lateral dynamics.…”

A new application of the Extended Kalman Filter to the estimation of roll angles of a motorcycle with Inertial Measurement Unit

“…where I + II represents the drag acceleration, III the Coriolis acceleration and IV the relative acceleration. Adding the gravitational acceleration to (6) yields the components measured by the IMU: (7) which in the following will be referred to as 'equations A' (exact form).…”

“…Hence, the capability of providing a real-time reliable measure of the actual roll angle is of paramount importance for any advanced braking, traction and stability control systems. More over, this would provide essential data for active or semi-active suspension systems [2,3], for improving the development of innovative suspension systems [4], and for a deeper understanding of motorcycle unstable behaviours due to interactions between longitudinal and lateral dynamics (like chattering [5,6,7] in the presence of a lean angle).…”