Vehicle steering control under the impact of low-speed tire characteristics

Controllers for vehicle steering are generally designed based on simplified vehicle lateral models that incorporate static empirical tire models. Dynamic lab tests show, however, that the lag behavior between slip angles and lateral forces is evident especially at low speeds. Among existing tire models, the relaxation length tire model (RLT model) addresses this dynamic behavior. However, the RLT model is still too simple to properly capture this important tire dynamics. This paper investigates the effect of the often-ignored tire dynamics on vehicle lateral controls. An improved tire model that describes the often-ignored tire dynamics is incorporated in a conventional vehicle lateral model to capture the resonant yaw mode and the steering lag behavior. The low-speed experiments of a snowblower were conducted to validate this improved vehicle model. Simulations have shown that the often-ignored tire characteristics significantly impact the steering control designs for the low-speed vehicle lane-keeping maneuvers