In this research the effects of a rear steering system for motorcycles have been investigated. Both a passive and an active system have been tested to determine which configuration assures the best stability without compromising the rider's feeling. In order to rank each solution, a method based on the oscillation (kinetic) energy has been proposed and validated. The research has been carried out using a multi-body model of the motorcycle, featuring an advanced motorcycle tyre model and specific control routines. It has been found that passive system has good effects on the stability, causing a strong reduction in the weave oscillations that occur after the motorcycle is excited with a lateral impulse. On the contrary, there are not stabilising effects on the wobble mode, that becomes unstable in braking conditions. A configuration with preload MPS = 8 Nm, damping coefficient CPS = 200 Nms/rad, and stiffness KPS = 1000 Nm/rad has been selected as best compromise, but the steering system should be anyway inhibited when the brake is activated. Handling simulations have demonstrated that the 2WS motorcycle with the passive system returns unexpected oscillations when the throttle is opened, altering in negative way the rider's feeling. An original active control for the rear steering system has been proposed. It is based on a 1st order relationship between front and rear steering angles. It has been found that this system may have stabilising effects on both the weave and the wobble modes, but different coefficient sets are required for the two purposes. Assuming as most important target the weave stability, the configuration having ki = kr = 0.15 has been selected. It is worth to remark that also the active system makes the vehicle dangerously unstable in braking conditions and opportune actions (such as inhibiting the rear steering or switching to a different coefficient set) are needed when the brake lever is activated. The handling tests have shown that the active system makes the motorcycle neutral when the throttle is opened, so that the rider feels as it would be riding the conventional motorcycle. By analysing the power spectrum of the weave test response, we found that the stabilising action of the active system is in general due to an energy transfer from weave mode to wobble mode.
How a rear steering system may improve motorcyle dynamics
Verbessurng der Motorraddynamik mit Hilfe eines Hinterrad-Lenksystems
International Journal of Vehicle Design ; 46 , 3 ; 328-346
2008
19 Seiten, 13 Bilder, 35 Quellen
Aufsatz (Zeitschrift)
Englisch
Anwendung im Fahrzeugbau , Motorrad , Fahrzeugdynamik , Fahrzeuglenkung , Mehrkörpersimulation , Mehrkörpersystem , Simulationsmodell , Simulationsmodellbildung , Fahrverhalten , kinetische Energie , mechanische Stabilität , mechanische Schwingung , Schwingungsanregung , Motorradreifen , Fahrzeugsicherheit , Fahrzeugerprobung , praktische Untersuchung
How a rear steering system may improve motorcycle dynamics
Online Contents | 2008
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Kraftfahrwesen | 2008
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