Nonlinear steering and braking control for vehicle rollover avoidance

Steering and braking control is applied to avoid rollover of road vehicles. The control concept presented is composed of three feedback loops: Continuous operation steering control, emergency steering control and emergency braking control. In continuous operation the roll rate and the roll acceleration are fed back by velocity scheduled gains to the front wheel steering angle. Thereby, the vehicle´s roll damping is robustly improved for a wide range of speed and height of the center of gravity. The latter may change for example with a truck from ride to ride. A rollover coefficient is defined that basically depends on the lateral acceleration at the center of gravity of the vehicle´s sprung mass. For critical values of this variable the emergency steering and braking system is activated. The rollover coefficient is also used for nonlinear feedback to the front wheel steering angle. The control concept is evaluated by linear sensitivity analysis and by simulations. Additionally, absolute stability of the steering control concept is verified using Popov´s criterion.