Development of High Fidelity Combustion-Driven Vehicle Models for Driveability Using Advanced Multi-Body Simulations

This paper demonstrates the development of a full multi-body vehicle model and its use in virtual design and troubleshooting of a vehicle response to throttle input. The multibody model is divided into three main subsystems: the chassis, the driveline and the powertrain subsystems. The chassis system includes a complete representation of both the front and the rear suspensions, both the front and rear subframes, and the vehicle body. The driveline system includes the output shafts from the transmission unit to the tires. The powertrain system includes complete representation of the cranktrain for a V6 combustion engine. Also included in the powertrain is a nonlinear representation of the gearbox where bearing clearances and gear lashes are considered. The cranktrain torque output is linked to the transmission using a torque converter model.

The vehicle components are virtually assembled together through different joint types, force elements, and kinematic constraints. Similar to the physical vehicle, the virtual model is driven using combustion pressure applied on the six pistons as the crankshaft rotates. The combustion pressure is obtained from measurements using pressure sensors. The model is then used to simulate different transient driveability events such as tip-in/tip- out and Wide Open Throttle (WOT) acceleration. In order to validate the virtual model, a set of measurements is acquired on the physical vehicle which includes crankshaft speed, engine block response, driveshaft torque, wheel/tire speed, and the vehicle body dynamic response. Also numerous signals and parameters of the ECU (Engine Control Unit) are collected to cross check the fidelity of the model. Once the model has reached an acceptable level of accuracy, it is exercised to shed light and give insights on the physical vehicle performance. This paper discusses different issues related to measurements, modeling and correlation in the development of a combustion-driven vehicle model and its usage to improve vehicle driveability.