Integrated Effects of Active Suspension and Rear-Wheel Steering Control Systems on Vehicle Lateral Stability

This research focuses on an integration of two optimal tracking controllers, the active suspension controller and the rear-wheel steering controller, with the objective of improving vehicle performances in terms of maneuverability and safety by enhancing road holding capability and lateral stability. The active suspension controller adjusts the vehicle roll angle and utilizes the vertical force at each active suspension to boost road holding capability. On the other hand, the rear-wheel steering controller adjusts rear steering angles to use lateral force at each ground-tire contact point and amplify the vehicle’s ability to follow the desired yaw rate and sideslip angle during cornering maneuvers. Though the active attitude motion and mass shifting of car body may seem to hold relationship with lateral stability, its ability to evenly distribute vertical tire forces benefits the rear-wheel steering controller by enhancing the road holding capability. A 8-degree-of-freedom (DOF) linear full car model is used in designing the active suspension controller, while a 2-DOF linear bicycle model is used in designing a rear-wheel steering controller. The two controllers are then applied to a 14-DOF nonlinear full car model so that the performances of the integrated control system may be evaluated through simulations. The two controllers in combination hold a potential to produce a synergistic effect on lateral safety.