Drive torque distribution for yaw control: potential and influence on vehicle handling and stability

The yaw moment potential resulting from variations in the front-to-rear drive torque distribution of all-wheel drive vehicles equipped with individual front axle and rear axle motors is investigated under combined longitudinal and lateral acceleration conditions. Using a detailed vehicle model, the influence of the drive torque distribution on the GG envelope, handling properties, and related types of loss of stability is examined. The analysis is conducted for a vehicle equipped with open differential gears, torque vectoring at the front axle and the rear axle, as well as a locked rear differential gear. A quasi-steady-state yaw moment potential is derived, composed of contributions from both longitudinal and lateral tyre force changes at the front axle and the rear axle. The analysis of this potential allows for an appropriate choice of a baseline drive torque distribution to exploit the maximum acceleration envelope of the vehicle and to avoid an early encounter with stability boundaries. The sensitivity of the yaw moment potential to variations in the drive torque distribution indicates a strong dependency of the potential on the current acceleration state and the proximity to relevant stability boundaries.