Interaction of Vehicle Ride Vibration Control with Lateral Stability Using Active Rear Wheel Steering

In this work the effects of vehicle vertical vibrations on the tires/road cornering forces, and then consequently on vehicle lateral dynamics are studied. This is achieved through a ride model and a handling model linked together by a non-linear tire model. The ride model is a half vehicle with four degrees of freedom (bounce and pitch motions for vehicle body and two bounce motions for the two axles). The front and rear suspension are a hydro-pneumatic slow-active systems with 6 Hz cut-off frequency designed based on linear optimal control theory. Vehicle lateral dynamics is modeled as two degrees (yaw and lateral motions) incorporating a driver model. An optimal rear wheel steering control in addition to the front steering is considered in the vehicle model to represent a Four Wheel Steering (4WS) system. The tire non-linearity is represented by the Magic Formula tire model. The ride vibration control, vehicle lateral dynamics and tire/road cornering forces are interlinked together in order to study the effect of vertical vibration control on the vehicle lateral stability with active rear wheel steering. The results are time domain simulation of the vehicle response when performing lateral maneuvers while road wheels are subjected to vertical excitation. Vehicle lateral dynamics are compared with 2WS and 4WS systems taking into account the vehicle wheelbase correlation between front and rear active suspension systems.