Torque Vectoring Axle and Four Wheel Steering: A Simulation Study of Two Yaw Moment Generation Mechanisms

There is increasing demand for enhancement of stability and handling performance in modern automobiles. Active yaw moment generation mechanisms are essential for implementing intelligent stability control schemes. Two mechanisms being considered here are Torque Vectoring Rear Axle and Four Wheel Steering System.

Torque Vectoring Axle allows active control of wheel speed ratio and torque distribution typically through the use of wet clutch/brake system and secondary gearing. Four wheel steer systems usually have conventional steering in the front axle and an active steering system in the rear axle. The steering logic is based on improved performance in terms of turning radius at low speeds and directional stability and response at higher speeds.

In this study, a lumped parameter, large amplitude, non-linear vehicle model of a rear wheel drive, high-performance vehicle is used. The simulation is executed on a skid pad as well as on a prescribed test track using a closed loop driver-vehicle system. The operating characteristics under steady state situation on a skid pad and dynamic performance on Nurburgring Nordschleife track are evaluated. The investigation is limited to high speed driving on surfaces with high friction coefficient. The results are presented along with that of a baseline vehicle.