Mathematical Modeling in Vehicle Ride Dynamics 2012-01-0056

Ride is considered to be one of the criteria for evaluating the performance of a vehicle. However, the evaluation of ride quality of a car varies from person to person. There are many mathematical models which are used to study vehicle ride dynamics. The development of electronics, sensors and actuators has enabled the use of control systems to enhance the ride quality of a vehicle.

This work deals with some of the commonly used ride models viz. Quarter Car model, 2 Degree of Freedom (DoF) Half Car Model and 4 DoF Half Car Model. A complete analysis of these models from a designer's perspective, e.g., variation of suspension stiffness, damping coefficient etc. is being presented. The response of these models to random excitation is being studied. The above mentioned models are based on the rigid body assumption. They do not incorporate a tire model which takes into account the stiffness and damping properties of the tire. The Flexible Ring Tire model is being incorporated into the 4 DoF Half Car model and effect of tire flexibility on vehicle ride is being analyzed. A flexible 2 DoF model, which models the chassis as an Euler beam on springs is also analyzed and a comparison with the rigid 2 DoF model is being done. Semi-active suspensions enable the variation of suspension properties to improve vehicle ride quality. These kinds of systems are becoming popular with high end cars. A simulation of MR dampers (semi-active suspension) using Bouc-Wen Model has been incorporated into the quarter car model using PID controller.