A New Lumped-Mass Vehicle Ride Model Considering Body Flexibility

Ride comfort is one of the most important criteria by which people judge the total quality of the car. Traditionally to investigate the vehicle ride comfort, some well-known classical lumped-mass models are used. In these models such as quarter car model, half car model and full vehicle model, body flexibility has been ignored and sprung mass (vehicle body) assumed to be rigid. This assumption can reduce the model accuracy, specially in the case of long vehicles such as vans, buses and trucks. To impose body flexibility in the ride analysis, recently some numerical FEM-based models have been introduced, but they are complex and non-parametric. In this paper the effects of body flexibility on the vehicle vibration behavior has been studied based on an analytical approach. For this purpose, a new simple and parametric lumped-mass 8 DOF model has been developed. Comparison of the results of natural frequency analysis and forced vibration analysis for this model with the corresponding results of so called “rigid model” or “classic model” is very informative. As the results are shown, body flexibility strongly influenced on the acceleration and displacement responses of the vehicle so that it is necessary to considering this term at the early stages of the vehicle design.