Towards an All-Wheel Drive Motorcycle: Dynamic Modeling and Simulation

Modern motorcycles are evolving more and more towards complex systems by the increasing integration of mechanical, electrical and control disciplines. All-wheel drive (AWD) vehicles have proven effective to improve vehicle's performances and rider's safety. Despite this, manufacturers have developed few AWD motorcycles and little research has been devoted to them. Obvious difficulties concern torque distribution to the front wheel because of steering system. Nowadays, the integration of technologies eases the implementation of front wheel drive opening new research perspectives. In this work, the dynamic model of an AWD motorcycle with an attached rider is proposed. It represents the first symbolic analysis investigating the effects of front wheel traction on the dynamics of a motorcycle for supporting the design of AWD motorcycles reducing trials and tests on prototypes. The proposed model is parametric with respect to the motorcycle geometry, and it allows to simulate complex operating modes of the AWD, such as cornering phenomena, taking into account coupling of lateral and longitudinal dynamics and tire-road interactions. Unlike other works, here the authors include a full tire model by exploiting theoretical slips of the brush model for tire's aligning moment too, instead of applying a totally empirical representation less suitable for a complete symbolic description. Besides, to simulate the equations of motion, the benefits and disadvantages of using AWD with torque distribution have been pointed out introducing a new handling ratio. Two verification procedures validate the model: one is performed theoretically, the other carries out a comparison with a multibody software, whose model is more sophisticated, this latter embeds all main motorcycle's dynamics. Although radically different, being the first theoretical and the second numerical-computational, both methods exhibit consistent behavior between them, and effectiveness of the former is also consistent with the results of a multibody simulator under the assumptions made.