Improvement of Vehicle Lateral Stability During Overtaking Process by Active Front Steering System

This work presents a theoretical study on a linear 3-DOF vehicle handling model which, incorporates driver's operation and vehicle suspension derivatives. The model is constructed to investigate the performance of vehicles with conventional front steering system and vehicles with actively controlled front wheel steering system as well. The control strategy of the Active Front Steering (AFS) control is based on the optimal control theory using LQR technique. The vehicle model excitation is a simulation of the aerodynamic forces and moments generated on a passenger car when overtaking a truck.

Results are showing a comparison between the performance of the vehicle with conventional steering system and the vehicle with Active Front Steering (AFS) system. A significant improvement with the AFS optimal system is achieved in the vehicle response especially for lateral deviation error. Also, it is concluded that using the optimal AFS system enhances vehicle stability and drivability through reducing the driver's steering effort during such an overtaking process. Therefore, this AFS system reduces driver fatigue and risk of accidents through reducing vehicle oscillations around the straight-ahead path.