Four-wheel driving-force distribution method for instantaneous or split slippery roads for electric vehicle with in-wheel motors

In this paper, a four-wheel driving force distribution method based on driving force control is proposed. Driving force control is a traction control method, previously proposed by the authors´ research group, which generate appropriate driving force based on the acceleration pedal. However, this control method can not completely prevent reduction of driving force when a vehicle runs on an extremely slippery road. If the length of a slippery surface is shorter than the vehicle´s wheel base, the total driving force is retained by distributing the shortage of driving force to the wheels that still have traction. On the other hand, when either the left or right side runs on a slippery surface, yaw-moment is suppressed by setting total driving forces of left and right wheels to be the same. Therefore, four-wheel driving force distribution method is proposed for retaining driving force on instantaneous slippery roads, and suppressing yaw-moment on split ones. The effectiveness of the proposed distribution method is verified by simulations and experiments.