Alpine has developed a three-motor architecture that outperforms mechanical limited-slip differentials with extra-precise and quick torque control on each rear wheel, writes Nick Flaherty.

The architecture has one motor at the front that powers the front axle and the two motors at the rear power one wheel each. Besides enabling all-wheel drive, this configuration allows the two rear motors to be controlled independently. This has led to a system Alpine calls Active Torque Vectoring (ATV), which is the result of five years of development and fine-tuning.

“Alpine Active Torque Vectoring is the step beyond conventional limited-slip differentials. This patented breakthrough can distribute anywhere between zero and 100% of the torque between the two rear wheels, enhancing the Alpine A390’s safety as well as its dynamic behaviour,” said Constance Leraud-Reyser, control systems engineer at Alpine.

ATV creates a variable torque split, generating a difference in torque distribution to the rear wheels, in response to steering angle and vehicle speed. This corrects any differences in slip between the right and left wheels and optimises cornering dynamics.

“First, we dynamically distribute the torque between the front and rear. Then, on the rear axle, since there are two electric motors, we replace the traditional mechanical differential, which also gives us the advantage of being able to exceed the range of a mechanical differential. The principle of Active Torque Vectoring ultimately lies in distributing the torque between the right and left wheels in order to add a rotational moment when cornering. It’s as if you were turning a miniature car with your hand. This creates a sense of lightness and agility. It’s as if the car feels less inertial overall,” she said.

The system acts in milliseconds whether the vehicle is accelerating, turning or driving in a straight line.

“This eliminates the slightest hint of oversteer or understeer,” said Leraud-Reyser. “In particular, it helps prevent deviation from your path when one of the wheels goes over a patch of ice.”

ATV has been implemented on the recently launched A390 GTS, the first Alpine with more than 400 hp and over 800 Nm of torque, providing up to 100 km/h in under 4 seconds.

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