Numerical Analysis of Vibration for Flexible Frame of a Lightweight Electric Vehicle

Vehicle vibration is one of the main factors for driving fatigue, discomfort and health problems. Most studies on ride dynamics and suspension systems of vehicles used lumped-mass model to represent the vehicle body and the wheels. However, a lightweight design of an electric vehicle frame may deteriorate the rigidity of the structure and, based on a previously performed finite element modal analysis, induces a flexible vibration. The flexible vibration affects ride performance and study on dynamic characteristics of the vehicle helps to understand the main parameters required to improve the ride comfort especially when using passive type suspension system. This paper presents comparison of numerical analysis of rigid-body and flexible full-vehicle models for lightweight aluminium frame vehicle with experimental results. The MATLAB Simulink was employed to simulate vibration responses at four areas namely front unsprung mass, rear unsprung mass, floor and seat. Sinusoidal input signals to the three wheels at low frequency of 4 Hz were applied in such a way that the vibration accelerations at the front and rear unsprung masses are equal to the experimental RMS accelerations that had been measured on the vehicle driven on road surface. The measured time-domain signal and PSD for front unsprung mass and seat were plotted to represent the actual vibration conditions of the vehicle. The RMS acceleration were computed for the four areas and compared with simulated data. It was found that the accelerations of the floor and seat using a rigid vehicle body model were not comparable with the experimental data. However the flexible vehicle model managed to generate data that corresponds well with the experiment. Thus it can be said that the flexibility model allows accurate analysis and hence better understanding of vehicle dynamics in order to improve ride comfort of the driver.