Vehicle Dynamics and Torque Management Devices

Brake based traction control and electronic stability control continue to grow as an approach to enhance vehicle traction and stability. However, there is still a considerable contribution to the improvement of traction as well as to the longitudinal and lateral dynamics and stability of a vehicle provided by Torque Management Devices (TMD) such as limited-slip differentials and on-demand couplings. Specifically electronically controlled Torque Management Devices can offer significant improvements without compromising other systems like ABS (Anti-Lock Braking System) and ESP (Electronic Stability Program), a.k.a. DSC (Dynamic Stability Control), VDC (Vehicle Dynamics Control), IVD (Interactive Vehicle Dynamics) or TRACS (Traction and Stability Control), etc.

This paper explains various driveline concepts using electronically controlled Torque Management Devices ranging from on-demand (hang-on coupling) to full time AWD systems with a center differential. The influences of controlled TMD's on vehicle dynamics are shown for various driveline layouts and TMD arrangements. Results from vehicle starting and acceleration tests prove the traction improvements achievable with TMD's. Furthermore it is shown that TMD's also have a significant influence on vehicle handling, stability and safety in 4WD systems as well as in 2WD applications. Vehicle test results are presented from circle tests like throttle-off in a bend, which prove that the systems have a significant positive impact on stability and safety. The same applies to highly dynamic driving maneuvers like double lane changes. The results achieved with the Electronic Torque Manager (ETM) from GKN demonstrate the high potential of sophisticated controlled TMD's not only to enhance traction but also to offer significant vehicle dynamics improvements.