Torque vectoring

Under Active Yaw or torque vectoring means the active influence of the yaw angle of motor vehicles ( engl. " Yaw Angle" ) or the yaw angular velocity ( yaw rate, closely " Yaw rate ". ) - Or simply put: With active yaw systems can steer through the wheels a motor vehicle in addition, by selected left and right distributes the drive torque differently. The system is not with the steering, active steering, four wheel steering and active rear axle kinematics (eg, rear-wheel steering in the BMW 850) to be confused. The effect is due to redistribution of the drive torque of a controlled, not the change in the wheel position.

The classic open differential distributes drive torque always the same, left and right wheels always transmitted the same forces, whereby the transfer is free of greed moments.

For a limited slip differential, however, torque can be shifted from rotating faster to the slower rotating wheel. When cornering, so come on steering effects. Since at normal cornering the slower wheel gets more torque, it means that a vehicle resists with limited slip differential steering movements and tends to understeer, or to put it positively: It has a better straight-line stability. Under high lateral acceleration changes the behavior. The inner wheel is relieved, is tending to spin. The locking differential manages the majority of the torque to the outside wheel, making a eindrehendes ( oversteer ) yaw moment generated during acceleration and when coasting, turning out a yaw moment ( understeer ).

Active Yaw systems are electronically controlled and, both the faster and the slower wheel feed with a higher torque, so that the cornering is selectively supported or suppressed. Thus an Active Yaw system includes the function of an electronically controlled limited slip differential. For the purpose of redistributing a portion of the drive torque from the differential carrier is routed directly to the desired wheel. In principle, this is the inverse of the ESP, in which a braking intervention (instead of drive torque ), the yaw moment is affected. The interaction of Active Yaw and ESP is that the Active Yaw in dynamic driving stability of the vehicle so improved that an intervention of the ESP is delayed. However, once the ESP detects a critical driving situation, it takes control and disabled ( as of 2008) the active yaw system. Future developments might be to share the Active Yaw.

The electronic control can be brand-typical characteristics, such as the handling of a rear-wheel drive in curves, targeted support while limiting the risks (loss of control). The driver obtains the expected standard of driving behavior, arise without risky side effects, or the practicality suffers.

Technically, this concept was for example in the Mitsubishi Lancer Evolution IV ( Active Yaw Control, AYC short, since 1996, with contribution to development of GKN Driveline ) placed first in series and in its technical structure is still based on the current and expected systems. In the Honda / Acura Legend ( Super Handling All Wheel Drive System, or SH -AWD ), this system has been implemented since 2004. The BMW X6 has a torque-vectoring rear axle ZF Friedrichshafen and GKN Driveline. Audi followed in 2008 with a system of Magna Steyr in the Audi S4. Nissan sets the system since 2010 Juke model available in four-wheel variant. The new Ford Focus since the 2012 model year Torque Vectoring Control is standard equipment. The electric mobility project MUTE the Technical University of Munich also uses torque vectoring.

For vehicles with pure electric drive, the torque vectoring can float on the top. Bosch Engineering has a road vehicle so modified as pure technology demonstrator that it controls the four each 60 kW motors by torque vectoring, which results in excess of 3000 Nm an unprecedented, highly agile form of driving dynamics, together with the total torque. From the current perspective (11/ 2011) is such a vehicle much too expensive for mass production.