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The feeling given through the vibration, which is transiently generated by the body when the throttle is beginning to be opened, is one of the important factors that affect the quality of drivability in motorcycles. This feeling is usually evaluated by subjective ratings on actual motorcycles carried out by expert riders and the specifications are decided based on those results. In this research, the subjective rating was expressed as a formula and the simulation technology of behavior prediction was constructed for the parts associated with the drive train as well as the motorcycle body. The responding time delay, the magnitude of overshoot and the vibration frequencies were extracted as highly correlated factors with the evaluation results of subjective ratings through the analysis on the characteristics of longitudinal acceleration responses of the body to the magnitude of throttle opening.

A new DC brushless motor, which has an almost equivalent driving performance to a 50 cm₃ scooter engine, has been developed to be used in a new electric motorcycle for business. The traction motor is compact enough to be mounted close to the driveshaft of the transmission, which helps reduce friction in the drive train. Consequently, in the downsized motor, by mounting the drive train unit with the PDU (Power Drive Unit) on the wheel side by applying reduction gears, it enables the reduction of maximum motor torque requirement. It also enables other parts of the drive system to be integrated into one unit. In this motor, IPM (Interior Permanent Magnet) structure has been implemented to cope with the high rotation of the motor, and the concentrated winding stator coil has been implemented for downsizing. As for the rotor, the magnets were placed in sections and the yoke shapes were improved to achieve higher rotation speeds that provide the higher power.