Development and Vehicle Integration of XWD Driveline Technology

Other conference contribution, 2009

The continuously ongoing development of new driveline hardware, improved vehicle state sensing capabilities and sophisticated vehicle dynamics control algorithms are strong enablers for improvements in both safety and functional performance of road vehicles. The present paper describes one of the latest achievements in this area, namely the development and vehicle integration of a state of the art all-wheel-drive driveline, named XWD or cross-wheel-drive, in the Saab 9-3. This all-wheel-drive driveline concerns an active on demand driven rear-axle, coupled to the front by means of an electronically controlled hydraulic clutch to distribute a variable amount of torque from front to rear. In addition to this front to rear distribution, the system is capable of transferring torque laterally across the rear-axle as well using an electronic Limited Slip Differential. In the next section of this paper, a complete system overview will be provided, detailing each and every component and explain both their mutual and external interfaces. Once having presented all key characteristics, the paper will further expand on how these characteristics determine system behaviour on a vehicle level, i.e. especially on vehicle dynamics properties like traction and handling performance. Furthermore, the paper will present specific development implications related to the integration in the Saab 9-3, i.e. how on one hand the vehicle architecture needs to be changed in order to incorporate the described system, and how on the other hand, the system itself is tailored to excel in this particular vehicle.