Braking behaviour of a 4-wheel-steered automobile with an antilock braking system

The antilock braking system has become a self-evident component of today's passenger cars. It not only affects the longitudinal dynamics but also improves directional stability while braking and keeps the vehicle steerable for the driver. Problems occur if the friction coefficient is much lower on one side of the vehicle (mu-split) as the resulting yawing torque can increase very fast and has to be controlled by the driver. Additional 4-wheel steering of a vehicle provides an opportunity to influence its lateral dynamics effectively. A desired steering characteristic can be achieved and the response of the vehicle to disturbances considerably improved. Simulations of full braking on a mu-split surface show that a vehicle equipped with antilock braking system and 4-wheel steering can combine the benefits of both systems and can thus be seen as a contribution to more active safety.