A Study for Applying an Anti-lock Braking System to 4-wheel Drive Cars

It is said that a four-wheel drive (4WD) system which can control the distribution of driving torque to the front and rear axles will result in remarkably improved tractive and cornering performance. However, because of the difficulty in obtaining accurate vehicle speed information and in identifying the influence of engine brake torque on performance on slippery roads, it has been difficult to apply an anti-lock braking system (ABS) to vehicles equipped with such a 4WD system.

This paper discusses a solution to this problem achieved through the utilization of a vehicle dynamic simulation model and a new integrated anti-lock and traction distribution control method. The existence of an optimum front/rear torque split which makes it possible to estimate vehicle speed accurately and to obtain the best level of ABS control performance is shown.