Development of Driving Control System Based on Optimal Distribution for a 6WD/6WS Vehicle

This paper describes a driving controller to improve vehicle lateral stability and maneuverability for a six wheel driving / six wheel steering (6WD/6WS) vehicle. The driving controller consists of upper and lower level controller. The upper level controller based on sliding control theory determines front, middle steering angle, additional net yaw moment and longitudinal net force according to reference velocity and steering of a manual driving, remote control and autonomous controller. The lower level controller takes desired longitudinal net force, yaw moment and tire force information as an input and determines additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and has considered the friction circle related to vertical tire force and friction coefficient acting on the road and tire. Distributed longitudinal/lateral tire forces are determined in proportional to friction circle according to the changes of a driving condition. The response of the 6WD/6WS vehicle with the driving controller has been evaluated via computer simulations conducted using the Matlab/Simulink dynamic model. Computer simulations of a closed-loop driver model subjected to double lane change have been conducted to prove the improved performance of the proposed driving controller over a conventional direct yaw moment control (DYC). Adjustment weighting factors applied for the optimal distribution controller enhance performance by comparing controller applied fixed weighting factors.