Design of Variable Vehicle Handling Characteristics Using Four-Wheel Steer-by-Wire

This paper presents a vehicle handling modification approach that tracks the dynamics of a general nonlinear planar reference model. The control structure is a combination of linear and nonlinear state feedback with feedforward of reference model yaw moment, lateral force, and longitudinal force at the vehicle center of gravity. The modified closed-loop system is demonstrated to be stable and has robust tracking performance to reasonable levels of model uncertainty. The handling modification method is applied to the task of emulating the dynamics of a reference vehicle on a low friction surface, with particular attention to actuator constraints. Experimental results demonstrate successful emulation of the low friction reference model's planar dynamics for a variety of driving maneuvers and reference friction coefficients. This handling emulation technique enables further investigation of vehicle handling performance improvements and use as a variable dynamic testbed for human factors studies.