The Active Braking Systems are devices which allow to vehicle stability and performance acting on brakes. The main active function are:
· ABS (Anti-Lock Brake System) Function which allows to improve longitudinal stability avoiding wheel lockage during braking maneuver;
· VDC (Vehicle Dynamic Control) Function which allows to improve lateral stability by generating a suitable yqw moment braking one wheel.
ABS Antilock-Brake System
In critical driving situations, when the road surface is wet or slippery for example, or when the driver reacts to a sudden shock, the wheels may block when the brakes are applied. This means that the vehicle can no longer be steered. The Antilock Braking System ABS recognizes the blocking tendency of one or several of the wheels at an early stage and reduces the braking pressure on the wheel or wheels concerned. It ensures that the driver can avoid obstacles and slow the vehicle down or bring it to a stand safely and quickly even after an emergency brake application.
VDC Vehicle Dynamics Control
Immediate reaction if the vehicle threatens to leave its track VDC can apply individual braking forces at each wheel in order to correct vehicle movement. If for instance the vehicle threatens to oversteer in a curve, VDC applies the brakes at the front wheel on the outside of the curve and generates a reaction torque which stabilizes the vehicle. Furthermore, if necessary, VDC is able to influence engine torque and with it the slip at the driven wheels. VDC reacts in a flash and thus neutralizes critical situations before they have a chance to materialize.
The complex VDC control system would be impossible without high-performance sensors and electronics. The system calculates the desired trajectory based on steering angle, while wheel speed sensors are measuring the rotational velocity of all wheels. A central element within this system is a yaw-rate sensor designed to consistently monitor the vehicle’s tendency to rotate around its vertical axis.
CRF was involved in the development of ABS system for Tractors, developing hardware architecture and control algorithms.