Ride Dynamic Analysis of a Hybrid Discrete and Continuous Vehicle Model 2008-01-2671

In this study the dynamic analysis of the vehicle system modeled as a hybrid discrete and continuous system has been investigated. The discrete system modeling has formed the traditional ride dynamic analysis model for vehicle systems. In such a model the chassis is assumed as a discrete block attached to different degrees of freedom that can account for the unsprung masses, engine and driver among many others. However, this model cannot accommodate all the aspects of a chassis which is strictly a continuous system. In the present study the chassis is assumed as a flexible beam on which a pair of single degree of freedom systems is added to account for the engine and driver. Moreover, the beam is mounted on a couple of spring-damper elements that simulate the suspension of the vehicle which results in a combination of continuous and discrete systems. In order to solve this problem, the assumed mode method has been employed using the mode shapes of a free-free beam. The method is applied on a city bus and the natural frequencies of the undamped system were calculated. Further, the frequency responses for ground and engine excitations were obtained. The method is validated by comparing the results with those obtained by finite element method where the beam is meshed as a continuous system while all other DOF were assumed as lumped masses connected to the chassis with spring damper elements.