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The vehicle response to specific steering performance inputs is called directional response and is an important
performance mode, which determines the stability of the vehicle. In this paper the dynamic behavior of a vehicle to various inputs and under different circumstances
has been studied. In simulating the dynamic behavior of the vehicle, the most effective element for the validity of the simulation results is the dynamic model of the tire. Therefore a complete vehicle
model which consists of the Roll, Yaw
and the lateral movements of the vehicle and considering non-linear behavior for the tire has been derived from thorough study on directional stability. In the selected model of tire, lateral and
longitudinal product forces in the tire are a function of instantaneous vertical load, slip angle and the physical characteristics of the tire such as pressure, width and so on. Solving the non-linear differential
equations, the effect of venous parameters such as the suspension system, tire characteristics, forward velocity, wind speed, etc. has been
discussed. Finally, since the control of
handing is directly related to the stability of a vehicle, and generally handling and stability of a vehicle, could not be
discussed separately, a comparison of three different steer angle control systems have been made.