Robust yaw damping of cars with front and rear wheel steering

For a linear model of active car steering, a robust decoupling control law by feedback of the yaw rate to front wheel steering has previously been derived. This control law is extended by feedback of the yaw rate to rear wheel steering. A controller structure with one free damping parameter k_D is derived with the following properties: damping and natural frequency of the yaw mode are independent of speed; k_D can be adjusted to the desired damping level; and a variation of k_D has no influence on the natural frequency of the yaw mode and no influence on the steering transfer function by which the driver keeps the car-considered as a mass point at the front axle-on a planned path. Simulations with a nonlinear car steering model show significant safety advantages of the new control concept in situations when the driver of the conventional car has to stabilize unexpected yaw motions