Dynamic Performances Analysis of an Electric Motorbike in case of Transient Excitation by Multi Body Dynamic Model

Abstract The dynamic performances of an electric motorbike subjected under transient road profile is analyzed by a Multi-Body Dynamics (MBD) 4 degrees of freedom (4DOF) model. The dynamic characteristics between suspension elements connected to the vehicle frame are determined by a MBD model. The electric motorbike specifications are selected based on the designed vehicle model, including size parameters and loading distributed in the front and rear axles of the vehicle. Suspension system parameters include the stiffness of the spring and the damping coefficient of the shock absorber, which is selected in the common value range of the vehicle’s suspension system, corresponding to the natural frequency and damping ratio. The transient road profile according to the IRC 99 - 1988 standard, has the length ( d 1 ) in range of 1.5÷3.7 (m), and examined velocity ( v ) range of 10÷80 (km/h). The evaluation indexes of the dynamic performances are analyzed including human body stability GA tr (%), safety working space of the suspension system GR tr (%) and the tire road holding ability GL tr (%). In which, the GA tr , GR tr , GL tr are respectively the ratios of the human vertical acceleration to the gravity acceleration, the dynamic suspension relative displacement to the suspension working deflection capacity, and the tire dynamic load to the tire static load. The obtained results show that with only one rider, the obtained GA tr was greater than 1 under excitation range of [ d 1 ≥ 2 (m), v >40 (km/h)], [ d 1 = 1.5 (m), v >13 (km/h)]. With two riders, d 1 = 3.7 (m), the obtained GA tr was less than 1 in the entire examined velocity domain. Both front and rear suspension systems ensured GR ftr <60% in all the investigated cases. In the front suspension system, with the same v and d 1 , with two riders, the GR ftr was always greater compared to the one rider case. The obtained GL tr was greater than the critical value of 1 with d 1 = 3.7 m, v >36 (km/h). The lower d 1 , the smaller critical velocity, causing the GL tr >1 is obtained. The obtained results show that the smaller the critical velocity or the critical stability condition of the designed vehicle decreases, when the applied loading or the excitation frequency increases.