Design and Simulation of a Torque Vectoring™ Rear Axle

This paper describes the process and simulation tool chain applied to the design for production of a rear axle with a variable torque biasing capability.

Based upon a proven core design (successfully demonstrated in 2004) comprising a novel epicyclic gear arrangement, several variants have been proposed using alternative actuation technologies to achieve bi-directional control of torque bias. The specific design described here includes two concentric wet-plate brakes of less than 200 Nm that control the left-right bias of up to 1400 Nm in a compact and modular design.

Recorded GPS data was replayed in a vehicle simulation to derive the range of yaw moment that would be usefully generated by the rear axle to control the lane-keeping and slip angle of the vehicle. Detailed modeling of the device was then undertaken to provide the actuation torque and values of tyre slip that enabled prediction of duty cycle and hence the thermal loading required to define the balance of thermal inertia and heat rejection for a practical design.

The paper concludes with a study of a potentially relevant alternative for the wet clutch-type actuation elements of the design. Rig results are presented for a large (c. 100 Nm) magneto-rheological brake with a variable fluid gap. This type of actuator may be applied in conjunction with alternative design variants using a single brake device in conjunction with selectable connectivity.